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Les disgrammes suivants illustrent la m4thoda. 1 2 3 1 2 3 4 5 6 MIOOCOfY RESOLUTION TKT CHART (ANSI and ISO TEST CHART No. 2) l^lli 1 3.2 136 2.2 1.8 ^ APPLIED IIVMGE Ir I65J East Mam Street Rochester, New York 14609 USA (716) 482 - 0300 - Pt,one (716) 288- 5989 - Fo, I. i MOBTABS, PLASTEE8, STUCC08 Artificial Marbles, G>iicretes, Portland Cements and Compositions BEING A THOROUGH AND PRACTICAL TREATISE OM TBI LATEST AKD MOST IMPROVED METHODS OF PREPARING AND USING LIMES, MORTARS. CEMENTS, MASTICS AND COMPOSITIONS IN CONSTRUCTIVE AND DECORATIVE WORK. INCLUDING A PRACTICAL TREATISE ON REINFORCED CONCRETES Prepared, Compiled and Edited By FRED T. HODGSON, O. A. A. A0THOB OF "Treatige on Ums of The Steel Square." "Modern Carpentry, ■• "Architectural Drawing Self-Taught." "Up-to-Date Hardwood Finisher." "20th Century Bricklaypr." "Modern Estimator." "Art of Wood-Carvlnjf." Etc. PROFUSELY ILLUSTRATED With Working Drawings and Sketches of Tools, Appliances, Ceiling Designs and Examples of Ornamental Stucco Work CHICAGO FREDERICK J. DRAKE & CO., PUBLISHERS Copyright 1916 by FREDERICK J. DRAKE & CO. Copyright 1914 by FREDERICK J. DRAKE tc CO. Copyright 1906 by FREDERICK J. DRAKE & CO. I " :l Printed in the U. S. A. PARTI CONCRETES, CEMENTS, PLASTERS AND STUC COS— THEIR USES AND METHODS OP WORKING SAME. INTRODUCTORY This book, or rather compilation, is largely made up of the very best mat rial available on the subjects it proposes to discuss. All the latest improvements and methods in the mixing, proportioning and application of plaster, mortar, stucco and cement will be described jind laid before the reader in as simple and plain a man- ner as possible. The art of using mortars in some shape or other, is as old as civilization, as we find evidences of its use in ruins that date long before historical times, not only in the older countries of Asia and Europe, but also in the ruins of Mexico, Central America and Peru; and the workmen who did their part, or most of this work, Mere evidently experts at the trade, for some of the remains of their work which have come down to us certainly show that the work was done by men who not only had a knowledge of their trade, but that they a?so possessed a fair knowledge of the peculiar qualities of the materials they used. "Plastering," says Miller in his great work on Mortars, "is one of the earliest instances of man's power of inductive reasoning, for when men built they plastered: at first, like the birds h'kI the beavers, with mud; but they soon found out a more lasting and more comfortable method, and the 7 8 CEMENTS AND CONCRETES earliest efforts of civilization were directed to plaster- ing. The inquiry into it inkea us back to the dawn of social life until its origin becomes mythic and prehis- toric. In that dim, obscure period we cannot pene- trate far enough to see clearly, but the most distant glimpses we can obtain into it show us that man had very early attained almost to perfection in compound- ing material for plastering. In fact, so far as we yet know, some of the earliest plastering which has re- mained to us excels, in its scientific composition, that which we use at the present day, telling of ages of ex- perimental attempts. The pyramids of Egypt contain plaster work executed at least four thousand years ago (some antiquaries, indeed, say a much longer period), and this, where wilful violence has not disturbed it. still exists in perfection, outvying in durability the veiy rock it covers, where this is not protected by ita shield of plaster. Dr. Flinders Tetrie, in his 'Pyra- mids and Temples of Gizeh,' shows us how servici-- able and intelligent a co-cperator with the painter, the sculptor, and the architect, was the plasterer of those early da^ s, and that to his care and skill we owe almost all we know of the history of these distant times and their art. Indeed the plasterer's very tools do yet re- main to us, showing that the technical processes then were the same we now use, for there are in Dr. Petrie's collection hand floats which in design, shape and pur- pose are precisely those which we use today. Even our newest invention of canvas plaster was well known then, and by it were made the masks which yet pre- serve on the mummy cases the lineaments of their occu- pants." The plaster used by the Egyptians for their finest work was derived from burnt gypsum, and was there- INTRODUCTORY 9 fore exactly the same as our "plaster of pari*." Its base was of lime stucco, which, when used on partitions, was laid in reeds, laced together with cords, for Iath< ing, and Mr. Miller, who has examined a fragment in Dr. Petrie's collection, finds it practically "three ooat -A-ork," about % of an inch thick, haired and finished just as we do now. Plaster moulds and cast slabs exist, but there does not appear any evidence of piece moulding, nor does any evidence of the use of modelled work in plaster exist. That some process of indurating plast(>r was thus early known is evidenced by the plaster pavement at Tel-el iVmaraa, which is elaborately painted. The floor of this work is laid on brick; the first coat is of rough lime stucco about 1 inch thick, and the finishing eoat of well-haired plaster about % inch thick, very smooth and fine, and showing evidence of trowelling, tha set- ting out lines for the painting being formed by a struck cord before the surface was set, and the painting dom* on fresco. It \h about 60 by 20, and formed the floor of the principal room of the harem of King Amenhotop IV., about fourteen hundred years before Christ, that is, between three thousand and four thouLand years ago. Long before this, plastering of fine quality- existed in Egypt, and so long as its civilization con- tinued it aided the comfort of the dwellings of its people and the beauty of its temples. Nor was it merely for its beauty and comfort that plaster work was used. Even then its sanitary value was recognized, and the directions given in Leviticus xiv, 42-48, which was probably written about one hun- dred years before this date, show that the knowledge of its antiseptic qualities was widely spread, and the practice of it regarded as religions duty. >-. < ,*-^k- n» CEMENTS AND CONCRETES Unfortunately there is no direct evidence that the ndjacont Amyrian powers of Nineveh and Babylon uied plastor work. Poiwibly the fine clay brought down by the livers of the Euphrates and the Tigris sufficed for all I heir pjirposes. Their records arc in it: their illustra- tions on the sculptured walls of their palaces are in stone, their painting is glazed on their bricks, and for them there seems to have been but little need for plas- ter work, nor do we find until the rise of Grecian art anything relating to our subject. Verj' early in Greek architecture we find the use of plaster, and in this case a true lime stueco of most ex- quisite composition, thin, fine and white. Some has been found at Mycenae, a city of HoTneric date. We know that it existed in perfection in Greece about five lumdred years before the Christian era. With this the temples were covered externally, and internally where they wen; not built of marble, and in some cases where they were. Thia fine stucco was often used as a ground on whit'h to paint their decorative ornament, but not infr('(|Ufntly left quite plain in its larger masses, and some of it remains in very fair preservation even to this day. The Temple of Apollo at Bassae, built of yellow sandstone about 470 B. C, has on its columns ihe n'mains of a fine white stucco. Pavements of thick, hard plaster, stained, of various colors, were common in the Greek temples. One of these, that of the Tem,»le of Jupiter Panhellenius at -Egina, built about 570 B. C, is described by Cockerell as existing in the early part of the century, in good ^^ondition, though the tenple itself was destroyed; and I have seen at Agrigent im plaster existing in perfect state, though scarcely thicker than an egt^-shell, on the sheltered parts of a temple built at least three hundred INTRODUCTORY tt /•an before our era, whilst the unprotectcU stone wat weather worn and decayed. What care the ancient Greeks bestowed on their Ntiiceo may be inferred from Pliny's statement that in the temple at El is about 450 B. C, Panaenus, the iiepliew of Phidias, UHcd for the groundwork of his picture "stucco mixed with milk and safTrun, and r isbt'd with spittle rubbed on by the ball of the thumb, nud," wiys he, "it still retains the odor of scffron." J^ysippus, the first of the Greek "realists" in sculpture, was the first we hear of who took casts of the faces of living sitters about 300 B. C, so the art of plaster cast* ing muHt have advanced a good deal by that time, as he made presents of copies to his friends. Afterwards we read of many sculptors who sent smaller plaster models (►f their works to friends. These were, however, prob- ably carved in the plaster rather than cast. Whether the Greeks used stucco for modelling is a somewhat doubtful point amongst antiquarians. From certain passages in classic writers I am induced to think tliey did. Pausanius, who describes the temple at Stym- phaluN, an almost deserted and ruined city when he visited it about 130 A. D., describes the ceiling of tho Temple of the Stymphalides, built about 400 B. C, as being "either of stucco or carved wood," he could not decide which, but his very doubt would imply that stucco or wood were equally common. Now, this ceil- ing was ornamented with panels and figures of the harpies — omens of evil, half woman and half bird, with outspread wings. He also mentions a statue of Bac- chus in "colored stucco." Of course these are not defi- nite proofs of early Greek stucco modelling, but as the city of Stymphalus had decayed and become depopu- lated before 200 B. G., there is certainly presumptive 12 CEMENTS AND CONCRETES evidence of the ancient practice of the art. Again, fig. ures of unburnt earth are mentioned in contradistine- tion to those of terra cotta, and sundry other alhisions to plastic work occur, which lead me to the opinion that quite early in Greek art this mode of using plaster be- gan. At any rate, we know that it was early introduced into Grecia Magna — the earliest Southern Italian col- ony of the Greeks; and as colonists invariably presenx' the customs and traditions of their fatherland even long after they have fallen into disuse in their native home, we can have no reasonable doubt but this art was im- ported rather than invented by them. Thence it spread to the Etruscans of Middle Italy, a cognate people to the Southern Greeks, by whom both plain and modelled stucco was largely used. The Etruscans, as we have seen, were more closely allied to the Greek than the Latin "-ace, but in the course of time these two races amalgan ated, the former bringing skill in handicraft, the latter lust of power, and patriotic love of country and of glory, whilst the Grecian element, which blended harmoniously with the first of these, added a love of art. This union, however, took long to ripen to artistic fruitfulness. The practical Etruscan element firstly constructed the roads and the sewers, and gave health to Rome. The Latins added to their territory until it em- braced half of Europe, giving wealth to Rome, and not till the luxury and comfort thus created did the artis- tic element of the Greek come in, giving beauty to Rome, and the day of decorative plaster work ap- proached its noontide glory, making Rome the attrac- tion of the world. The absorbance of Greece as a Roman province took place B. C. 145, and the loot of it began, giving an enormous impetus to Roman art. Thousands of statues were brought to Rome, and to INTRODUCTORY 13 be deemed a connoisseur in things artistic or a patron of the arts became the fashionable ambition. But it was not until the century just preceding the Christian era that it became especially noteworthy. Of course there is hardly anything left to us of the very early plaster work of Rome. The constant search for some new thing was inimical to the old. Old structures were l)ulled down to make way for new, which in their turn gave way to newer, and until the age of Augustus we have but little of the early work left. Strabo, who visited Rome about this time, complains of the destruc- tion caused by the numerous fires, and continued pull- ing down of houses rendered necessary, for even pull- ing down and rebuilding in order to gratify the taste is but voluntary ruin ; and Augustus, who boasted that "he found Rome of brick and left it of marble," in replacing the brick with marble destroyed the plaster work. How that plaster work was wrought we shall learn more from Vitruvius, who wrote his book on archi- tecture about 16 B. C, and dedicated it to the emperor, "in order to explain the rules and limits of art as a standard by which to test the merits of the buildings lie had erected or might erect." Now, Vitruvius was a man who had travelled and seen much. He was with Julius Caesar as a military engineer in his African campaign in 46 B. C, or ten years after Caesar's invasion of Britain. Afterwards he became a designer of military engines, what we should call head of the Ordnance Department, and also a civil engineer, persuading himself that he liad a pretty taste in architecture, just as though he were an R. E. of today. Thus he had a practical and also an artistic training, and here is what he says on mattcz's connected with plaster work in Book VII, Chapter 11. i « : f ' iT* r 14 CEMENTS AND CONCRETES On tempering lime for stucco: "This requires that the lime should be of the best quality, and tempered a long time before it is wanted for use; so that if any of it be not burnt enough, the length of time employed in slak- ing it may bring the whole mass to the same consist- ency." He then advises it to be chopped with iron hatchets, adding that "if the iron exhibits a glutinous substance adhering to it, it indicates the richness of the lime, and the thorough slaking of it." For cradling out, and for ceiling joists, he recommends "the wood to be of cypress, olive, heart of oak, box and juniper," as neither is liable to "rot or shrink." For lathing he specie fies "Greek reeds bruised and tied with cords made from Spanish broom," or if these are not procurable "marsh reeds tied with cords." On these a coat of lime and sand is laid, and an additional coat of sand is laid on to it. As it sets it is then polished with chalk or marble. This for ceilings. For plaster on wall he says: "The first coat on the walls is to be laid on as roughly as possible, and while drying, the sand and coat spread thereon. When this work has dried, a second and a third coat is laid on. The sounder the sand and coat is, the more durable the work will be. The coat of marble dust then follows, and this is to be so prepared that when used it does not stick to the trowel. Whilst the stucco is drying, another thin coat is to be laid on : this is to be well worked and rubbed, then still another, finer than the last. Thus with three coats and the same number of marble dust coats the walls will be solid, and not liable to crack. The wall that is well covered with plaster and stucco, when well polished, not only shines, but reflects to the spectators the images falling on it. The plasterers of the Greeks not only make their stucco work hard by adhering to these direc- INTRODUCTORY 15 tions, but when the plaster is mixed, cause it to be beat- en with wooden staves by a great number of men, and use it after this preparation. Hence some persons cut- ting slabs of plaster from ancient walls use them for .tables and mirrors." (Chapter III.) You will see by these remarks the great care taken through every process, and how guarded the watchful- ness over the selection of materials, and you will also note the retrospectiveness of Vitruvius' observation, how he felt that the work done before the frantic haste of his own time was the better: very much as we find now. Time is an ingredient in all good work, and its substitute diflReult to find. There are other "tips" contained in this work which are worth extraction, as, for instance, his instructions as how to plaster damp walls. In such case he prima- rily suggests a cavity wall, with ventilation to insure a thorough draught, and then plastering it with "pot- sherd mortar," or carefully covering the rough plaster with pitch, which is then to be "lime whited over," to insure "the second coat of pounded potsherds adhering to it," when it may be finished as already described. Further, he refers to modelled plaster work which, he says, "ought to be used with a regard to propriety," and gives certain hints for its appropriate use. Speak- ing of pavements "used in the Grecian winter rooms, which are not only economical but useful," he advises "the earth to be excavated about two feet, and a foun- dation of potsherd well rammed in," and then a "com- position of pounded coal lime, sand and ashes is mixed up and spread thereover, half foot in thickness, per- fectly smooth and level. The surface then being rubbed with stone, it has the appearance of a black surface,*' "and the people, though barefoot, do not suffer from '.jSla. 16 CEiVlENTS AND CONCRETES oold on this sort of pavement." Now all this bespeaks not only theoretical knowledge, but practical observa- tion and experience, and was written nearly two thou- sand years ago, from which you can surmise how far advanced practical plastering had then become. This written evidence is almost all we have of the work of Vitruvius' own time, for even of the time of Augustus hardly anything remains to us, as the great fire of Nero utterly destroyed the greater part of the city in the year A. D, 64, and almost the only authenticated piece of plaster work done before or during his reign is the Tabula Iliaca, a bas-relief of the Siege of Troy, still preserved in the Capitol Museum at Rome. That this was modelled by Greek artists is proved by the fact that its inscriptions are all in the Greek language, and by some it 's considered to be of verj' much greater an- tiquity. J 1 aueh for the ancient history of the art of plastering, and I trust I will be pardoned if I con- tinue this sketch, bringing it down to a more recent period and show in what high respect the plasterers' art was held in the Sixteenth Century, and later. Quoting from an old work, giving an account of the institution of "The Worshipful Company of Plaisterers, " and mak- ing use of the quaint language then in use we are told that: "The Plaisterers' Company, which ranks as forty-sixth among the eighty-nine companies, was in- corporated by King Henry VII., -^ March 10, 1501, to search, and try, and make, anc cise due search as well in, upon, and of all manner of stuff touching and concerning the Art and Mystery of Pargettors, com- monly called Plaisterers, and upon all work and work- men in the said art or mystery, so that the said work might be just, true, and lawful, without any deceit or fraud whatsoever against the City of London or suburbs INTRODUCTORY 17 thereof. The Charter gave power to establish the Com- pany as the Guild or Fraternity in honour of the Blessed Virgin Mary, of men of the Mystery or Art of i*argettor8 in the City of London, commonly called Plaisterers, to be increased and augmented when neces- .sary, and to be governed by a Master and two War- dens, to be elected annually. The Master and Wardens and brotherhood were to be a body corporate, with per- petual succession and a common seal, and they were empowered to purchase and enjoy in fee and perpet- uity lands and other possessions in the City, suburbs and elsewhere. And the charter empowered the said Master and Wardens to sue and be sued as "Tha Mas- ter and Wardens of the Guild or Fraternity of the Blessed Mary of Pargettors, commonly called Plaister- ers, London." TBS OtD COAT OF ACJ18. The Company under the powers to make examina- tions, appears to have inflicted fines on offending par- ties for using bad materials, and for bad workmanship. Search days appear to have been annually appointed up to 1832, but not since, and the Company has not exercised any control over Plaisterers' work for many years. • • «• ^ 18 CEMENTS AND CONCRETES Another charter was granted by Queen Elizabeth in 1559, but it has been lost, and there is no record of the contents. The Queen granted a new charter in 1597, which confirmed the privileges of the Company, and extended the authority of the Master and Wardens to and over all persons exercising the art of plaisterers, as well English as aliens and denizens inhabiting and exercising the said art within the City and suburbs and liberties, or within two miles of the City. THB nHUMT OOAT OW ABIU. Charles II., by a charter dated June 19, 1679, con- firmed the privileges granted by the previous charters. Having in view the rebuilding of the City, he forbade any person to carry on simultaneously the trades of a mason, bricklayer or plaisterer, or to exercise or carry on the art of a plaisterer without having been appren- ticed seven years to the mystery. The jurisdiction of the Company was extended to three miles' distance from the City. There wer^ two orders made by the Court of Alder- men (exempafied under the mayoralty seal, April 1> INTRODUCTORY 19 1585) lor settling matters in dispute between the tilers ADd bricklayers and the plaisterers as to interfering in each other's trades. The observance of these orders was enforced by an order of the Privy Council dated June 1, 1613, and a general writ or precept issue to the lame effect on August 13, 1613. Indian Centre-Piece. There was also an order of the Cour* of Aldermen (29 Elizabeth, February 14, 1586-7; relating to the number of apprentices to bo kept by members. An act of Common Council was passed, under date of 18 James I., October 5, 1620. An act of Common Council (6 William and Maiy, October 19, 1694) was also passed to compel all persons using the trade of plaisterer in the City of London or *m CEMENTS AND CONCRETES f \he liberties thereof, to become free of the Compan/ under penalty to be recovered as therein mentioned. In the East the Art of ornamental plastering was well known and almost universally practiced before Mahom- et established a new order of things, and the enriched plaster work of India, Persia and other Eastern Em- pires are evidences of the high character of the work- manship of the Oriental workers in plaster. The iVrabian and IMoor brought back the Art of the Western World in the early part of the thirteenth century, and it is to them we owe the splendid plaster work of the Alhambra and other work still in existence in Spain. In the Mosque at IMedina, built in 622, are still to be seen some fine specimens of old plaster work that was wrought on the building at the time of its completion. The Mosque of Ibu-tubun, Cairo, Egypt, which was fin- ished in A. D. 878, abounds with beautiful plaster work. It contains a number of arches and arcades, the capi- tals of which, like the rest of the building, are enriched with plaster buds and flowers made in elaborate de- signs. Even in Damascus, thai old and far-off City indulged in ornamental plaster-work when the people of Western Europe were cutting one another's throats for political ascendency. We illustrate a few examples of old work taken from existing specimens. These will to some extent, give an idea of what the old plasterers could do. See illustrations attached. During the middle ages in Europe plastering and stucco existed only as a craft, and its highest function was to prepare a surface to be painted on. Sometimes it was used as an external protection from the weather but rarely was it employed for direct ornament. Some- times small ornaments were carved in plaster of Paris, but it played no important ^ „rt i\ decorative Art, INTRODUCTORY' 21 excepting perhaps, as gesso, though this belonged rather to the painter than the plasterer. Nor was it until the commencement of the Renaissance in Italy that it showed any symptoms of revival. •A«AiiEsqu« MOM THt Cheat Mos'jui. Damawm. With the commencement of the fifteenth century old learning and old arts began to be studied, the discovery of the art of printing and the consequent multiplication of the copies of the lore heretofore looked up in old manuscripts gave invention and progress new life. 22 CEMENTS AND CONCRETES which has lasted until the present day. Italy has al- ways been the nursinjr mother of plasterers, and in Mr. G. T. Robinson's "Glimpse of the History of the Art and Craft," he has shown something of her great and slorious past, and how she sent her sons over almost all Europu to raise the art and status of this craft Persian Centre- Pikce. Even during the depressing times of her history she religiously preserved its ancient traditions and pro- cesses, and in almost all her towns there was some one or two plasterers to whom was confided the restoration, thfi repair and the conservation of its frescoes or it« stuccos. The art dwindled, but it survived. So late «s 1851 an Enelish architect, when sketching in the INTRODUCTORY 28 Campo Santo at Pisa, found a plasterer busy in lov- ingly repairing portions of its old plaster work, which time and neglect had treated badly, and to whom he appUed himself to learn the nature of the lime he used. So soft and free from caustic qualities was it that the painter could work on it in true fresco painting a few days or hours after it was repaired, and the modeller used it like clay. But until the very day the architect was leaving no definite information could he extract. At last, at a farewell dinner, when a bottle of wine had softened the way to the old man's heart, the plas- terer exclaimed, "And now, signor, I will show you my secret!" And immediately rising from the table, the two went off into the back streets of the town, when, taking a key from his pocket, the old man unlocked a door, and the two descended into a large vaulted base- ment, the remnant of an old palace. There amongst the planks and barrows, the architect dimly saw a row of large vats or barrels. Going to one of them, the eld man tapped it with his key; it gave a hollow sound until the key nearly reached the bottom. "There, sig- nor! there is my grandfather! he is nearly done for." Proceeding to the next, he repeated the action, saying: "There, signor! there is my father! there is half of him left." The next barrel was nearly full. "That's me! ejfclaimed he; and at the last barrel he chuckled at finding it more than half full: "That's for the little ones, signor!" Astonished at this barely understood explanation, the architect learned that it was the cus- torn of the old plasterers, whose trade descended from father to son for many successive generations, to care- fully preserve any fine white lime produced by burning fragments of pure statuary, and to each fill a barrel for his successors. This they turned over from time to "5i I tall 24 CEMENTS AND CONCRETES lime, and let it ain— slake in the nioi«t air of the vault, and 8<) provide pure old lime for the future by which to preserve and repair the old works they venerated. After-inquirie« showed that this was a common prac- Portion of a Ceiling from Teheran, Persia. tice in many an old town, and thus the vain*; of old air-slaked lime, such as had been written about eisihteen hundred years before, was preserved as a secret of th.' trade in Italy, whilst the rest of Europe was advocatine: INTRODUCTORY 31 tbe exclusive use of newly burnt and hot slaked lln,.. wag there in the early part, indeed even in the mid ter. For succeuful work good materials and skillful mixing are essential. It is applied in one, two, or three coats, and by the number of these the plaster is named. The Thinner the Coati of plaster are the better, as the plaster has a better chance of drying and harden* ing. One-Coat Work, necessarily the conunonest an cheapest, is limited to very inferior buildings, such as nuthouses and places where it will not be seen, as be- hind skirtings. One-coat work on laths is specified as "lath and lay," or "lath and plaster," and on wailn Rimply as "render." Two-Coat Work is that usually employed in inferior Nvork, such as factories, warehouses, etc., but it is also used for the least important rooms in better class build- ings. Common setting for walls and ceilings is gener- Hlly used for this class of work. Two-coat work on laths is specified as "lath, lay, and set," or "lath, plas- ter, and set," and on walls as "render, and set." Three-Coat Work is that used in all good buildings, and forms a most satisfactory wall finish, when well done. Three-coat work on laths is specified as "lath, lay, float, and set," or "lath, plaster, float, and set," and on walls as "render, float, and set." The Processes in Plastering ordinary three-coat work are as follows: For the First Coat a layer of well-haired coarse stuff known as pricking-up is laid to a thickness of about y2 in. This should be laid diagonally and with each trowelful overlapping. If on laths it should be soft enough to be well worked through them to form a key. The surface is then scratched with a lath to form a key for the next cofit in lines nbont 4 in. apart. It is WORKMANSHIP 39 ready for the ■econd coat "when too hard to recelv* an imprenion from ordinary preMure. The Coarse Stuff uned in the first coat it mortar com- posed of sand and lime, usually in the proportions of 2 to 1, with plenty of hair, so that when a trowelful is taken up it holds well together and does not drop. The Second Coat known as floating, is next laid. Four processes are involved in laying the second coat, namely: Running the screeds, filling in the spaces, scouring and keying the surface. The scouring is done with a hand float, the surface being sprinkled by a brush during the process. The keying consists in lining the scoured surface with a broom or nail float to form un adhesive surface for the finishing coat. The Fltating is of finer quality than the coarse stuff, it does not contain as much hair, and is used in a softer state. The Third Coat is the finishing cofit, and is known as the setting coat. Great care must be taken in laying this coat in order to obtain uniformity of surface, color, smoothness, and hardness. The second coat shnnld be uniformly keyed, clean and damp before the third is laid. The processes involved are laying, scouring, trow- elling, and brushing. Fine Stuff, which should be used for the finishing eoat if the walls are to be papered, consists of pure lime, slaked and then saturated till semi-fluid, and al- lowed to stand till the water has evaporated and it iorms a paste. It may then be thoroughly mixed with iine sand in the proportion of 3 parts of sand to 1 part of fine stufiF. Plasterers' Putty is much like fine stuff, but is care- fully sieved. I III 40 CEMENTS AND CONCRETES Gauged Stuff is plasterers' putty and plaster of Paris in the proportion of three or four to one. If too much plaster is used it cracks in setting. It is largely used in cornices, and also where the second coat is not allowed time to dry, and Ihe work has to be done in a hurrj'. As it sets rapidlj, It must be mixed in small quantities. The White Cements (such as Parian, etc.), of which plaster of Paris is the base, are usually laid in two coats; the first, of cement and sand, is about i/. in. to % in. thick, and the second of the cement neat. Cracks in Plaster Work are caused, apart from the natural settlement of the building and the use of in- ferior materials and workmanship, by the too fast dry- ing of the work, the laying of the plaster on walls of too great suction, by layinc; one coat on another before the lower one has properly set, and by the use of too little sand. Joist Lines on Ceilings are very unsightly, and are caused by the filtration of dust through the intervening spaces. They may be prevented by using a good thick- ness of plaster, and workinn: it well, that it may be hard and nonabsorbent and aa th? dust comes from the top and filters through, by proteiting the upper side of the plaster. Pugging consists in laying a quantity of plaster be- twecu the joists of a floor or between the studding of a partition for the purpose of preventing the passage of sounds or odors. In the first case, which is the more common, the plaster is laid on thin, rough boards fixed to battons on the sides of the joists; in the second ease, which is called "counterlathing" in some parts of the country, by plastering on laths nailed between the par- tition studs. ?r*- WORKMANSHIP 41 Pugging Should Not Be Used Too Wet There are three objections to this— the first that it takes a ver\' long and inconvenient time in drying, and secondly, that the water is liable to be ab? .^^d by the wood, and to cause it to rot; and thii Jy, h Is liaHe to crack in the drying. For this last re so^i it shou:' i always be laid in two coats. The Battons shonld all be nailed at an equal depth from the tops of the joists, and the plaster should bo of an equal thickness throughout, which is obtained by drawing a trammel along the joists. Mineral Wool is far more sanitary than ordinary pugging, has considerable sound and fire resisting qual- ities, it docs not absorb moisture and so rot the laths and timbers, is a preventive of vermin, and is light in weight. Lime Whiting or Whitewash which is lime dissolved in water, is a useful and sanitary covering for tlio walls of cellars and outhouses. If Lime-Whited Walls Have to Be Plastered, the wall should be first carefully picked, as if the lime is left on, the plaster is liable to scale. Fibrous Plaster is composed of plaster, canvas, wood, • etc. It is light and dry and can be quickly fixed. Ornamental Plaster ceilings may be either modelled throughout in situ, or cast in pieces, or formed by work- ing the ornament on a previously formed flat ceiling. The first method is the more costly, but more feeling is thereby obtained. IS SPECIFICATION CLAUSES. MATEIIIALS. 1. The sand for plastering is to be fresh-water river, or pit sand, and free from earthy, loamy, or saline material, to be well screened, and to be washed if re- quired. 2. The laths to be straight-riven or saron pine of the strength known as lath and half, well nailed with lin. oxidized lath nails, properly spaced for key, and with butt-headed joints, double nailed, and breaking joint in 3 ft. widths. The lathing to be "Expanded metal," No. — gauge. 3. The lime for coarse stuff to be approved well- burnt grey-stone lime, to be run at least one month before being required for use, to be kept clean, and well mixed as required with two parts sund and one part lime. 4. The coarse stuff for ceilings, lath partitions, and elsewhere where directed to have 1 lb. of good, long curled cowhair, free from grease, leading, or other im- purities, well beaten in, and incorporated with every :{ cu. ft. of coarse stuff. 5. Approved lime, free from lumps, flares, or core, is to be used for setting, putty, etc., and is to be run at least one month before being required for use. 6. The Portland cement is to be of the best quality and description for plastering purposes, from an ap- l)roved manufacturer, ai d must on no account be used fresh, but be spread out to cool for at least ... weeks 3?) a dry shed or room. 42 SPECIFICATION CLAUSES 43 All giiitable cement a id all other materials required ill plastering are to be of the best of their respective kinds and descriptions. 7, Provide all plasterers' plant, necessary scaffold- ings, tools, moulds, running rules, straight edges, tem- plates, etc., of every kind and description necessary for the proper execution of the work. WORKMANSHIP. 8. Lath, plaster, float, and set all wood joist ceil- ings, soffits, and stud partitions, and finish partitions to line in trowelled stucco. The concrete ceilings and soffits are to be well hacked for key and floated and set in gauged stuff, and the V )ncrete partitions are to be floated and set. Do all dubbing out where required to concrete ceil- ings, soffits, and partitions in gauged stuff. The concrete soffits of strong rooms to be finished with one coat of putty gauged with plaster only. 9. Cover all chases containing pipes, etc., with heavy wire lathing suitable for plastering on, securing the same in a thorough manner. The wire lathing to be \votted in lime water before being put on. 10. Render, float, and set all walls where not other- wise described. The walls to to be finished in trowelled stucco. 11. All cornices and moulded work throughout to he run clean and accurately to the sections given. All mitres and returns to be truly worked, and all enrichments and modelling to be to architect's ap- I>roval, and strictly in accordance with the models and instructions given. Run moulded plaster comifos girt to roomo, I 44 CEMENTS AND CONCRETES with all mitres, returned, stopped, and mitred ends etc., as required. The cornices to are to be run in fibrous plas- ter, fitted and Ixed with proper oxidized nails, and made good to. 12. All narrow reveals, splays, and returns to be finished in suitable cement on a Portland cement back- ing. Bun strong cement angles and arrises on Portland cement backing to all projecting angles except the fol- lowing, which are to be moulded, viz. : Run rounded angles to of 3 in. girt in strong cement as before. Run avolo moulded angles 3 in. girt with 2 in. wings to opening, finished with moulded stops and short lengths of angle and arris to detail, all in best cement. All exposed surfaces of concrete lintels and girder casings are to be finished in white cement internally and Portland cement externally, kept flush with faces of brickwork; all with arrises and angles excepting those otherwise described. 13. Run Portland cement flush skirting 9 in. high to baaement, where plastered, with flush head to top and trowelled face. The skirting to to be 12 in. high and 1 in. projection, sunk and twice moulded in white on Port- land cement backing. Float off the concrete floors of in Portland ce- ment to the required level to receive mosaic and the payings. 14. Run all necessary quirks, spla>s, arrises, et^., and make good to all mantelpieces; cut away for and make good after all other trades, and cut out and make II gyn*. ■juiiijij SPECIFICATION GLAUSES 45 ..ood all cmcks, blisters, and other defects, and leave plaster work perfect at completion. 15 Ding walls where shown on plans with a coat ot Portland cement 1 part, sand 2 parts, pea-gnt 1 part, Ld ground chalk 1 part. Finish walls where shown !v^th a rough coat of Portland cement 1 part and sand 8 parts, and rough cast with fine pea-gnt. 16 Stop and twice lime white soffits and walk of .. n Twice distemper white all ceilings, soffits, and cornices, and twice distemper to approved tints the walls of all rooms. ■i. '.;«' iHf^ "'' W: if^P^ 1 1* >• 1.51 s i i I PREPARATION OF BILL OF QUANTITIES. MATERIALS. Materials and Plant, etc. — 1 to 7. These items ap- pear in the Leading under Specification clauses. WORKMANSHIP. Ceilings, Partitions, and Walls. — 8 and 10. These are all billed at per yd. super, including lathing where required, also hacking concrete and any dubbing in the Ip^i.er, stating the thickness. Keep all plaster work less than 12 in. wide separate in "narrow widths." Wirelathing. — 9. These being narrow, it is advisable to measure them at per ft. run, stating the width. Cornices. — 11. Cornices and mouldings under 12 in. girt are measured at per ft. run and those over this girt at per ft. super, number all mitres, stoppings, etc. ; those to the running items following same, and those to the superficial items averaged for girt. See whether bracketing is required; if so, take the girt required at per fi. super., numbering angle brackets to mitres and returned ends, and averaging the girt. Measure the walls and ceilings less by the height and projection of the cornice, and add to the girt of the cornice 2 in. (i. e., 1 in. for each edge) for the portion up to the ceiling and walls. Enrichments are measured at per ft. run, giving the girt and description, and including the modt'ling. If 46 BILL OP QUANTITIES 47 of exceptional character, a provision for modelling is Bometimes inserted. Angles.-12. These appear in bill in feet run with thf ^rt of moulding or bead (if any) and also the iTdtS of returns. Number the stops, mitres, etc.. al- 7oW each to follow the item to which they apply^ "he finishings to concre.. beams Untels. etc. is kep separate as in "narrow widths to beams, etc.. and all arrises etc., being measured at per ft. run. Z'tingor vLes.-lS. Describe skirtings or dadoes gi^ng heUt and projection, and also finish at top. and ^ra^ure at per ft. run. numbering all mitres, enck. etc Sde the dubbing with the item. The general wall nlaaterine is deducted for these. . n^^g for mo»ic «.d tile paving, appears m the '"J^rS-irLbor to splays, quirks. arris«. etc.. are measured at per ft. run. The attendance on trades is frequently measured in detdl, as "making good around mantels" or gratings, %he cutting-out and making good appears at the end of the bill in the form here given. Rough Cast.-15. As clauses 8 and 10 Lime Whiting and Distempenng-16 and 1-. ^h^ appear in the bill in yd. super. In the case of distem. pering If the colors are in any way special mention Sr and also if in dadoes and filling, taking the di- viding line in feet run. , Distempering on cornices is usually measured in ft^ sup r Ttat^g the number of tints, and if l-^s picked ouf'n ft run; as is also distempering on ennchmente, teking the latter as "extra to," the distempering to cornices being measured over enrichments. 48 CEMENTS AND CONCRETES LATHS OENERALI.Y, General opinion is undoubtedly in favor of split laths, and split laths are sometimes specified by archi- tects for eeilinpi and partitions. Sawn laths, unless cut from specially selected straight-f?rained stuff, would most assuredly have weak places from uneven srain, and in order to avoid this weakness the sawn laths would have to be made thicker than split laths, and cnly the best quality should be used. Oak laths, for- merly used, are very liable to warp. The defects that are to be avoided in laths are sap, knots, crwkedness, and undue smoothness. The sap decays; the knots weaken the laths; the crookedness interferes with the even laying' on of the stuff, and the undue smoothness n the mortar, and for looHoninx inortnr whi'ii too "stiff," or when it »>aa developed a tondeney to "set." They an- hIko used for preparing "putty" and fine "stuff." (See Fig. 2.) Thr Ilau'h; which is a square board about thirteen inches sfiuare, with a short handle on the under side. It is used for holding stuff while the operator is at work. It is generally made of pine or some other light wood ; it is made thin on thandle should be cut off square with one side and point- ed Its use is to make grooves, or bond in what is called the scratch coat. When completed it has somewhat the appearance of a gridiron. ilod— This is formed by two boards, eleven and twelve inches wide, respectively, and eighteen inches long the wide board being nailed on the edfie of the i,Hrrow one, making a right-angled trough: one end is closed, and the end piece is rounded over the top; the 56 CEMENTS iiND CONCKETES boards forming the sides are rounded at the opening A handle about four feet long and two inches in diam- eter IS then fastened about two inches forward of the middle nearer to the open end, and a piece of wood called a pad is fitted with a groove on the angle just back of the handle. The object of this block is to pre- vent the arris of the hod from chafing the shoulder of the laborer. Much controversy has taken place amono workmen at various times regarding the exact size of hod, but this, I think, should be governed more by the strength of the person who has to use the particular hod than by any fixed rules. Hods for carrying mortar need not be so large as liods intended for carrying bricks. (See No. 2, Fig. 1.) Sievc.—Thia is used for straining through putty for finishing; It requires to be very fine for the purpose Sometimes a hair sieve is used, but they are not last- ing, and should never be used when a wire sieve is ob- t^nable. Sometimes a hair sieve may prove convenient where dry plaster or cements have to be run through a sieve of some kind before it can be used; .so. on the whole, the plasterer who desires a full and complete outfit, should provide himself with one good hair sieve, and at least two sieves of wire. (See Fig. 7, No. 1.) Sand Screens are usually twenty-one inches wide in- side by about six feet long. On small work they are stood lip at an angle of forty-five or more degrees, and the sand is shovelled again.st them ; in some large works the screen is suspended, and one man shovels in the sand and a second one swings or shakes the screen These screens, to be lasting, should have their sides and ends made of sheet iron, and the bottom should be formed with parallel rods of small round iron having wires running across them at regular intervals. These TOOLS AND APPLIANCES 67 cross wires should be attached to thw iron rods so as to hold them in place. The parallel rods may be placed at such distances from each other as will be most con- venient for the work in hand. Mortar Beds are made of rough lumber of any kind, and should be built partly in the ground, where cir- cumstances will permit. They require to be strongly put together, as they have considerable weight to sus- tain. The writer has seen mortar beds built up with bricks and cement where large works have been under construction. Sometimes, master workmen, who do a large business, and who employ a great number of men, keep a large mortar bed or two in the rear yard of their shop and tool house, in which they keep always en hand a supply of ready-made stuff, which enables them to do small jobs or repairs at a moment's notice. The Slack Box.— This is generally made of boards, and is eight or nine feet long, and from two to four feet wide, and twelve or sixteen inches in depth. An opening about eight inches square is left in one end, with a slide door attached, so that it can be opened or closed at pleasure. The opening should be covered on the inside with a grating, so that when the lime is run off no lumps or stones will get through. The grating may be made with iron rods, or may be formed with wooden laths or slats. The bottom of the box should be made as close and tight as rough boards will permit (See No. 1, Fig. 11.) LathingA— It frequently happens in towns and coun- try places that the plasterer has to do his own lathing, or at least have it done under his own supervision, therefore it will be necessary to have something to say on this subject, and on the tools employed by the work- man whose duty it is to prepare the walls for the plas- 58 CEMENTS AND CONCRETES terer. These tools need not be extravagant ones or many in number. They consist of the following: Lather's Hatchet.— This is a small hatchet with a blade not more than one and a half inches wide, and rather larger in proportion than ordinary hatchets. The opposite end to the cutting edge is a hammer, with which the lather drives the nails. Sometimes the face of the hammer end is grooved, which makes it cling to the nails if the latter are not struck fairly on the head. An expert lather, however, will prefer a flat hammer face for driving lath nails. The cutting edge is used for "nipping" off laths when they are too long, or when short spaces of lathing are required to be made. In cutting lath with the hatchet, the workman gives the wood a short sharp blow with the tool at the point where the severance is required, and the lath is in- variably cut at the first blow, if the operator is an ex- pert. (See 0, Fig. 2.) Nail Pocket.—Perhaps the best nail pocket a lather can have is made from a portion of an old boot leg cut off to about four inches deep, and having a bottom of semi-circular shape made of wood, and to which the portion of the boot is fastened by means of broad-head- od tacks. The pocket is fastened to the workman's waist by means of a strap, or other suitable device, and hangs in front of him in a convenient position. Some- times nail pockets are made of canvas, but these are not so handy, as the top is apt to close and then nails fire difficult to get at. This never occurs with the boot leg pocket. Cut-off Saw.~A cross-cut saw is an indispensable tool to the lather for cutting lath in larger quantities for short spaces, and for rigging up platforms to work on, and for cutting supplementary stiidding or stripe J!JU,..,.l,*, •».. 1 TOOLS AND APPLIANCES 50 There such are necessary. The saw should have rather ccarse teeth and have plenty of set. Usually, the lather thinks that almost any old used-up saw is good enough for this purpose, and we find him struggling away with all his strength cutting through a bundle of lath, when, if he had a saw that was worth anything— as a saw- he would perform his labors with about one-half the effort, and one-third of the time. It is all wrong to think of being able to work satisfactorily with inferior or imperfect tools. Tliore is no economy in using tools of this kind,, and any lather who fancies he is going to make or save anything by making use of an old buckled, mortar-staint 3 saw, makes a terrible mistake. Get a good saw and keep it in good order, and it will pay you in two weeks. (See X, Fig. 2.) Besides these enumerated, there are many other tools and appliances that the plasterer will require, such as jointing rules, moulding knives, modellin«r tools, drags, chisels, com- passes, plumb rules, etc. II PLASTER, LIME, CEMENTS, SAND, ETC. Plaster of Porw.— Gypsum, from which plaster of Pans is made, is a sulphate of lime, and is so named from two Greek words— ge, the earth; and epsun, to concoct, 1. e., concocted in the earth. In Italy it is known by the name of gesso; in Scotland it is* called stucco; in this country it is known as calcined plaster; and m the English trade as plaster. The terra "plas- ter" will henceforth be used in this book. The writings of Theophrastus and other Greek authors prove that the use of plaster was known to them. A stone, called by Theophrastus gypsos, chiefly obtained from Syria was used by the ancients f;)r converting into plaster' Gypsum is mentioned by Pliny as having been used by the ancient artists, and Strabo states that the walls of Tyre were set in gypsum. The Greeks distinguished two kinds— the pulverulent and the compact. The lat- ter was obtained in lumps, which were burnt in the fur- naces, and then reduced to plaster, which was used for buildings and making casts. Gypsum is found in most countries— Italy, Switzer- land, France, Sicily, The United States, and some of the South American States; also in Newfoundland and Canada. The latter is said to be the finest deposits in the world. It is found in England in many places The finest gypsum is called "alabaster," and is soft. pure in color, and fragile. This white translucent ma- terial is a compact mass of crystalline grains, and is used for making small statuary, vases, and other ornament's. Gypsum is found in immense quantities in the tertiary 60 ' ^K'^miaw mMmm PLASTER, LIME, ETC. ei strata of Montmartre, near Paris. This gypsum usual- ly contains 10 per cent, of carbonate of calcium, not al- ways in intimate union with the sulphate, but inter- spersed in grains. This sulphate gives the Paris plas- ter some of its most useful properties. Pantin, near Paris, has large beds of gypsum, one bed being hori- zontal and over 37 ft. thick. The term "plaster of Paris" was mainly applied to it because gypsum is found in large quantities in the tertiary deposits of the Paris basin. Another reason is that lime and hair mortar is seldom used in Paris for plaster work, plaster of Paris being used for most kinds of internal and external work. Plaster is known in the color trade as terra alba. Plaster of Paris was known in England by the same name as early as the beginning of the thirteenth century. The gypsum, in blocks, was taken from France, and burnt and ground there. It continued to be burnt and ground by the users until the middle of the nineteenth century. The burning was done in small ovens, and the grinding in a mill, sometimes worked by horse-power, or more often by hand. Plaster is the mast vigorous as it is the oldest vehicle tor carrying down generation after generation the mas- terpieces of art with which the golden age of sculpture enriched the human race. For reproductive uses, plas- ter enables youth to contemplate antiquity in its noblest achievements. Today plaster is revolutionizing indus- trial art for us, and in all probability for those who are to come after us. Plaster, lowly and cheap, but docile and durable, is the connecting agent with this greatest of men's endorsement in the past. Plaster thus employed in duplicating works of marble, pottery, and metal work, is today extending the finest indos- 62 CEMENTS AND CONCRETES tries, modern and ancient. Plaster is one of the bert known fire-resisting materials for building purposes. After the conflagration at Paris, it was found the beams and columns of wood which had been plastered were entirely protected from fire. In cases where limestone walls had been ruined on the outside by the flames pass- ing through the window openings, the same walls in- ternally escaped almost unscathed owing to their being protected with plaster. Plaster in some climates has great lasting properties. T' e Egyptians covered their granite sometimes, and sand stone always, with a thin coating of stucco. The Qreeks coated even their mar- ble temples with plaster, and the plaster portions are now in better preservation than unprotected masonry, particularly at Agrigentum in Sicily. Quick and Slow Setting Plaster. — M. Landrin, in giv- ing the results of his long continued studies relative to the different qualities of gypsum, states that the more or less rapid setting of plaster is due to the mode in which it is burned. Its properties are very different when prepared ir ^umps or in powder. The former when mixed in its own weight of water sets in five min- utes, while the latter under similar conditions takes fif- teen minutes. The reason probably is that plaster in powder is more uniformly burned than when it is in lumps, which tends to prove this fact, that when the latter is exposed longer than usual to the action of heat it sets more slowly. Gypsum prepared at a high tem- perature loses more and more of its affinity for water, retaining, however, its property of absorbing its water of crystallization. Plaster heated to redness and mixed in the ordinary manner will no longer set; but if, in- stead of applying a large quantity of water, the small- est possible portion is used (say one-third of its PLASTER, LIME, ETC. 68 weight), it will set in ten or twelve hours, and becomes extremely hard. To prepare good plaster, it should not be burned too quick to drive oflP all its moisture, and for its molecules to lose a part of their affinity for the water. If the plaster is exposed to heat until it has only lost 7 or 8 per cent, of its moisture it is useless, as it sets almost immediately. If, however, the buminj? is again resumed, the substance soon loses its moisture, and if then exposed to the air it very rapidly retakes its water of crystallization, and absorption continues more slowly. It then sets slowly, but attains great hardness. Testing.— The quality of plaster may be tested by .simply squeezing it with the hand. If it cohere slight- ly, and keeps in position after the hand has been gently opened, it is good; but if it falls to pieces immediately it has been injured by damp. Although plaster does not chemically combine with more than one-fourth of its weight of water, yet it is capable of forming a much larger quantity into a solid mass, the particles of plas- ter being converted into a network of crystals, mechan- ically enclosing the remainder of the water. Sulphate of lime (plaster) is soluble in water to the extant of 1 part in about 450, the solubility being but little influ- enced by temperature. It is on account of this solu- bility in water that cements which have to a large ex- tent piaster for their bases are incapable in this raw state of bearing exposure to the weather. The setting of plaster is due to hydration, or its having but little water to take up to resume a state of consolidation. Plaster is used with hydraulic limes to stop the slaking, and convert the lime into cement. These are then called "selenitic." In 100 parts of gypsum there are 46 acid, iime 32, i 64 CEMENTS AND CONCRETES and water 22 parts. «ood plaster should not begin to «et too soon, and it should remain for a considerable TZ r ^ 'IT^ '*"*'• ^^^^" °"^« «^t •* should be very hard. Plaster should set slowly, as it gives more time for manipulation, but principally because one which sets quickly and swells never becomes so hard as slow-setting material. The quality of plaster can- not be determined by its color, the color being regu- ated by that of the gypsum; but all things being equal the whitest and hardest generally yields the best plas' ter. But as the exception proves the rule, it may be mentioned that some plasters (such as Howe's) are of u delicate pink tint, and of a very fine grain, and ex- <-.'ed.ngly strong when gauged. This pink plaster is much appreciated by many plasterers for making origi- "j. s as owing to its fineness and density it is very sidt- able for cleaning or chasing up models taken from the elay and also for durable moulding pieces. One of the whitest plasters known, which is also very close in tex- ture, IS that manufactured by Cafferata. For cast work he color of plaster is of small moment, because the cast uork IS sooner or later colored with paint, and more- over, un ortunately daubed over with distemper, or •orse sti 1 with whitewa.sh. Coarse pla.sters are da ker n color than fine. Coarse plasters of a sandy nature .-.nd which rapKlly sink to the .ottom when put in ^^at.■r. conta.n too much silica, or improperly burnt RyF.sum. or are .lorivod from a bastard gypsum, and are generally of a weak nature. romm-csshr and Adhesive Strength.~The compres- •s-ve resistance of properly balced plaster is about 120 hZ «n h "'T'' '"'^ ^'^'" ^"""^^ ''''^^ "^^t water and 160 lbs. when gauged with lime water; thus .show- ing that lime water hardens and improves the affinity PLASTER, LIMB, BTU. 66 of plaster. The adherence of plaster to itself is greater than to stone or brick. The adhesion to iron is from 24 to 37 lbs. the square inch. French PUuter.—A considerable quantity of French plaster was formerly used in this country but our own i« more uniform in quality and cheaper in price, so the use of the French material is somewhat limited. In Paris various kinds of gypsum mortars are in general use, raw gypsum and other materials being often inter- mixed. They also contain free carbonate of lime, ac- cording to the degree of heat to which the raw stone has been subjected. The Hotel de Platres, in Paris, affords a good illustration of the constructive uses to which plaster can be put, some of the blocks being about a hundred years old. Irtme«.— Lime is one of the most important materials in the building trades. Limestone is the general term by which all rocks are roughly classified which have <;arbonate of lime for their basis. They are obtained from many geological formations, varying in quality and chemical properties. The carboniferous consists of nearly pure carbonate of lime. In the limestone of the lias carbonate of lime is associated with silica and alumina (common clay), in proportions varying from 10 to 20 per cent. Carbonate of lime is found in a state of chemical purity in rhombohedral crystals as Iceland spar. It is also found in six-sided prisms, known to mineralogists as arragonite. Its purest form as a rock is that of white marble. Colored marbles contain iron, manganese^ etc. The lias strata consists of a thin layer of hard lime- stone separated by another of a more argillaceous ehar. acter, or shale, containing various proportions of car- bonate of lime. i :' fi *' I, •6 CEMENTS AND CONCRETES ?': Hydraulic I.»me«.— Hydraulic limes are thoae whidi have the property of setting under water op in damp places, where they increase in hardness and insolubil- ity. The blue lias lime formation is that from which hydraulic lime is principally made. This lime, while it has excellent hydraulic properties, can hardly be classed »!« a cement. The stones which produce these limes con- tain carbonate of lime, clay, and carbonate of mag- nesia. The clay plays an important part in giving hy- draulicity to the lime, consequently this power is great, er in proportion to the amount of clay contained in the lime. The proportion of clay varies from 10 to 30 per cent When lime contains clay it is not so easily slaked as pure lime, and does not expand so much in doing 5o, and therefore does not shrink so much in setting. Lias lime (called blue lias from the color of the stone from which it is produced) is very variable in quality •nd is generally of a feeble nature, but is sometimes of tn hydraulic nature. M. Vicat divides them into three classes: feebly hydraulic, ordinary hydraulic, and emi- nently hydraulic. "Those belonging to the first class' oontain from 5 to 12 per cent, of clay. The slaking action is accompanied by cracking and heat. They also expand considerably, and greatly resemble the fat lim'?s during this process. They are generally of a buff color. Those of the second class contain from 15 to 20 per cent, of clay. They slake very sluggishly in an hour or 80 without much cracking or heat, and expand very little. They set firmly in a week. The eminently hy- dnu)\> limes contain from 20 to 30 per cent of clay, are very difficult to sbke, and only do so after a long time. Very frequently they do not slake at all, being reduced to a powder by grinding. They set firmly in a few hours, and are very hard in a month." TT?f ii Hlliia s PLASTER. UME, BTO. 91 A natuntl hydraulic lime is obtained from what ap- pears to be a sedimentary limestone that has been formed by being deposited from water which held it in solution. It is very fine-grained, and contains almost no fossil'', and scarcely the trace of a shell is to be seen, except at the top and bottoms of the divisions, which are four in number, and in all from 9 to 12 ft. thick. When first worked, the stone was slaked in hot kilns, but now this is effected by grinding. According to the *'M'Ara" process, the "lime shells" from the kiln arc ground in the same way as the clinker of Portland ce- ment. Beginning with a stone-breaker, the lime passes from this to a pair of chilled crushing rollers, and final- ly to the njillstones, after which the powder is carried by screAT-conveyor and elevator to a rotary screen, 12 ft. by 4 feet, covered with wire cloth, which retains and returns to the millstones any residue in excess of the required fineness. Sifting is r. very important factot in the process, as it is scarcely possible to have the mill- stones so perfect that they will not pass a few large particles. The residue of imperfectly ground lime will doubt- less slake when mixed with water, but at long or un- certain periods, so that it is obvious that fine grinding is a necessity, and the itetting properties are not fully and safely developed unless the whole is finely pulver- ized. With regard to "Fat lime": the general prac- tice is for lime producers to show their lime as rich as possible by analysis, and for users to prefer a rich lime, for the reason that it makes a more plastic and better working mortar with the usual quantity of sand. Now, it has been proved by experiments, many and varied, and extending over a lon«? period, by the most eminent authorities, French, German, English and Amt 'an, 68 CEMEiNTS AND CONCRETES that this preference should exactly be reversed, and that the poorer common limes will make the best mor- tar, and will, in a comparatively short time, show some light setting power, whereas the very rich limes never take band, except in so far as they return to their orig- inal condition of carbonate by the reabsorption of car- bonic acid from the atmosphere, and by the slow evap- oration of the water of mixture. If it does not evapo- rate, the mortar remains always soft. If it evaporates too quickly, the mortar falls to powder, a result which must be in every oae's experience who has witnessed the taking down of old buildings, and the clouds of dust created by the removal of every stone. Some of the stones from which fat lime is produced contain a portion of sand as an impurity. They there- fore yield an inferior substance. This, though cheaper, is not so economical as pure lime, as it does not increase its volume so much when slaked. The pure or fat lime should only be used for plastering, as it is easily slaked, and therefore not so liable to blister as most hydraulic limes. It expands to double its bulk when slaked, and can be left and reworked again and again without in- juring it. The Romans are said to have prepared their limes. Thi.s "lime putty," prepared by immersion for a longer or shorter period — seldom less than three weeks — before heing used, is laid on in a very thin coat, and gives a hard skin to the surface. This hardness is largely, if not wholly, due to the fact that the lime is laid on in H thin layer on the floating coat that has already ab- sorbed carbonic acid from the air. This thin layer be- <'(imes harder than the main body of tke plaster. The whole process of preparing lime and layiiig 'J on the walls in thin coats, with a considerable space of " » ..■ ! ' A ' JHa ! PLASTER, LIME, ETC. 69 time between the coating, is conducive to the ultimate hardness of the whole. The lime is first slaked, and then made into coarse stuff, and setting stuff, all this t'me being exposed to the carbonic acid of the atmos- phere. Again, each coat is long exposed to the same influence before being covered with the next, although in marked contrast to the system of using the mortar in building. Calcination. — The process of "lime burning" is car- ried out in several different ways. But whether the operation be carried out in the simplest manner, or in kilns constructed on the most scientific principles, it will still depend (both as regards the quality and quan- tity of lime produced) upon the kilnsman, as it is only by constant observation from 'lay to day that che man becomes capable of judging lether the proper ttni- perature has been reached or that a correct opinion can be formed as to the effects produced by the various disturbing causes which exert an important influenco upon the working of a kiln, such as its size, shape, the quality of the fuel, and the state of the atmosphere. The kilns vary in size and shape in different districts, though they are generally inverted cones or ellipsoids, Into which layers of limestone and fuel are alternately thrown. When worked continuously as running kilns, the lime is periodically withdrawn from below, fresh quantities of fuel and stone being filled in at the top. When lime has not been properly calcined, or "dead burnt," it will not slake with water. This may arise from two causes — from insufficient burning, when the limestone, instead of being entirely caustified, has only been changed into a basic carbonate, consisting of two equivalents of lime and ouu of carbonic aeid, one-half only of its carbonic acid having been expelled. This 1. ;i 70 CEMENTS AND CONCRETES bane carbonate, on the addition of water, instead of forming a hydrate of lime, and being converted into a fine and impalpable powder, attended with the pro- dnetion of a large amount of heat, is changed, with little elevation of temperature, into a mixture of hy- drate and carbonate. In the case of hydraulic limes AVhich contain a considerable amount of silica, this "dead burning" may arise from the limestone having been subjected to a too high temperature, whereby a partial fusion of the silicate of lime formed has been produced, giving an impervious coating to the inner portions of the stone, retarding the further evolution of the carbonic acid. On this account the eminently hydraulic limes require to be carefully calcined at as low a temperature as practicable ; and hence it is not infrequently found that lias lime has been imperfectly calcined. Pure limes, if subjected to an excessive temperature, exhibit somewhat less tendency to com- bine with water than is the case with lime properly calcined. Caustic limes unite with water with great energy, so much so as to evolve a very considerable amount of heat. When water is poured upon a piece of well-burnt lime heat is rapidly generated, and the lime breaks up with a hissing, crackling noise, the whole mass being converted in a short time into a soft, impalpable powder, known as "slaked lime." Slaking.— Chemic&Uy speaking slaked lime is hydrate of lime— that is, lime chemically combined with a definite amount of water. In the process termed "slak- ing" one equivalent or combining proportion of lime unites with one equivalent of water, or in actual weight 28 lbs. of lime combines with 91 lbs. of water (being nearly in the proportion of three to one) to form 37 Iba of solid hydrate of lime. The water loses its liquid PLASTER, LIME, ETC. 71 condition, and it is to this solidification of water that the heat developed during the process of slaking k partly due. Slaking is a most important part in the process of making coarse stuff and putty lime. Unless the slak- ing is carefully and thoroughly done, the resultant ma- terials are liable to "blister" or "blow," owing to sn^all particles stiU remaining in a caustic state. Blis- ters may not show until a considerable time has elapsed. There are three methods of slaking "lump- lime"— the first by immersion; the second by sprink- ling with water; and the third by allowing the lime to slake by absorbing the moisture of the atmosphere. Rich limes are capable of being slaked by immersion, and kept in a plastic state. They gain in strength by being kept under cover or water. Pliny states that tlie Romans had such great faith in this method that the ancient laws forbade the use of lime unless it had been kept for three y^ars. All rich limes may be slaked by mixing with a sufficient quantity of water, so as to reduce the whole to a thick paste. Lump lime should first be broken into small pieces, placed in layers of jibout six inches thick, and uniformly sprinkled with water through a pipe having a rose on one end, or by means of a large watering-can having also a rose, and covered quickly with sand. It should be left in this state for at least twenty-four hours before being turned over and passed through a riddle. The layer of sand retains the heat developed, and enables the process of .slaking to be carried out slowly throughout the mass. Any unslaked lumps may be put into the middle of the next heap to be slaked. The quantity of water should be perfectly regulated, as if over- watered a useless paste is formed- If a sufficient quantity is not supplied, & 72 CEMENTS AND CONCRETES dangorons powdering lime is produced. Slaking by sprinkling and covering the lime lumps is frequently done in a very imperfect and partial manner, and por- tions of the lime continue to slake long after the mortac has been used. Special care must be exercised, and sufficient time must be allowed for .ae lime to slako when this method is employed. DiflFerent qualities of lime require variable amounts of water; but the medium quantity is about a gallon and a half to every bushel of lime. No water should be added or the mass disturbed after slaking has bo- gun. In most places the lime for making coarse stuff is generally slaked by immersion, and is run into a pit, the sides of which are usually made up with boards, brick work, or sand, the lime being put into a large tub containing water. When the lime is slaked, it is lifted out by means of a pail, and poured through a coarse sieve. It ir sometimes made in a large oblons box, having a movable or sliding grating at one end to allow thd lime to run out and also to prevent the sedi- ment from passing through. In preparing lime for plaster work, the general prac- tice is to slake it for three weeks before using. Not only so, but a particular cool lime is selected, for th.^ reason that it is not liable to blister and deface thf internal walls when finished. Now, vhile all this pro- caution is taken in regard to plastering, in making mor- tar for building the lime is slaked and made up at once, and it is frequently used within a day or two. But this is not all. Limes which are unsuitable for plaster work, known as hot limes, and which, when plasterers are obliged to use, must be slaked for a period of— not three weeks, but more— nearly three months before using, and are then not quite safe from PLASTER, LIME, ETC. 73 blistering, are the limes mostly used for building pur- poses. It will at once be seen that when mortars of t>icse limes are used immediately, the unslaked par- ticles go on slaking for a long time, drying up tho moisture, and leaving only a friable dust in the joints. This should help in understanding the old Roman law which enacted that lime should be slaked for three years before using. If three years should seem to us an absurd time, yet it may be justly said that at least three months are required to slake completely, and to develop fully the qualities of many of the common limes in everyday use. Major-General Gillmore, the eminent American specialist on the subject of Limes and Cement, mentions that in the south of Europe it is the custom to slake the lime the season before it is to be used. Mortar. — This is a term used for various admixtures of lime or cement, with or without sand. For plaster work it is usually composed of slaked lime, mixed with sand and hair and is termed "coarse stuff," and some- times "lime and hair," also "lime." In Scotland tho coarse stuff is generally obtained by slaking the lump lime (locally termed shells) with a combination of water sprinkling and absorption. The lime is placed in a ring of sand, in the proportion of one of lime to three of sand, and water is then thrown on in suffi- cient quantities to slake the greater portion. The whol.; is then covered up with the sand, and allowed to stand for a day; then turned over, and allowed to stand foi another day; afterwards it is put through a riddle t* free it from lumps, and allowed to stand for six weeks (sometimes more) to further slake by absorption. Tt is next "soured" — that is, mixed with hair ready for use. Sometimes when soured tho stuff is made up in MM I 11 74 CEMENTS AND CONCRETES a large heap, and woi^ed up again as required for use. This method makes a sound, reliable mortar. In some parts lime slaked as above is mixed with an equal part of run lime. This latter method makes the coarse stuff "fatter" and works freer. All slaked limes have a greater affinity for water than the mechanicaliy ground limes. Grinding is another process for making mortar or "lime," and if made with any kind of limestone is beneficial. It thoroughly mixes the material, increases the adllesion, adds to the density, and prevents blister* ing. When there is a mortar-mill, either ground or lump lime can be used, and the coarse stuff may be made in the proportion of 1 part lime and 3 parts sand. The lime should be left in the mill until thor- oughly reduced and incorporated, but excessive grind- ing is detrimental. The process should not be con- tinued more than thirty minutes. Both material and strength is economized if lump lime is slaked before being put in the mill. When a mortar-mill is used for grinding the lime, the sand may be partly or wholly dispensed with, and t'xcellent results are obtained by using old broken bricks (dean and well burnt), stone chippings, furnace cin- ders (free from coal), or slag. It is most essential in all cases tLat the materials used should be perfectly clean. It should be "Borne in mind that a complete in- corporation of the ingredients is essential in the slak- ing and mixing for coarse stuff, whether done by hand or machine. The sand or other material used p^n be tested by washing a portion in a basin of clean water^ theii sifting through a fine sieve. If there is an undue i-esidue of clay, fine dust or mud in the water or sieve, the whole of the aggregate should be washed or re- . .' n PLASTER, LIME, ETC. 75 jected. Lias lime should be mixed dry with sand and damped down for seven or ten days to ensure slaking. It should not be used fresh for floating or rendering. Pure or rich limes are not so well adapted for outside Mork, or places exposed to the action of damp, as hy- draulic limes. Mortar should be well tempered before using. Pliny states that it was an ancient practice to beat the mortar for a long time with a heavy pestle just before being used, the effect of which would be not only more thoroughly to mix the materials, but to take from the outside of the sand the compound of lime and silica (if such had been formed during the period of seasoning) and by incorporating it with the mass, dispose it more rapidly to consolidate. Smeaton found that well-beaten mortar set sooner and became harder than mortar made in the usual way. Mortar made from hydraulic limes should be mixed as rapidly as is compatible with the thorough incorporation of the materials, and used as soon as practicable after mixing, because if put aside for any length of time its setting properties will deteriorate. Pure limes may be rendered hydraulic by mixing them with calcareous clays or shales, which have been so altered by the agency of heat that the silica they con- tain has to some extent assumed the nature of soluble silica. In good coarse stuff each granule of sand is <*oated over with the lime-paste so as to fill the inter- St iocs; the lime-paster is to hold the granular sub- stances in a concrete form. If too much lime-plaster is present, it is called "too fat"; if the lime-paster is deficient it is "too lean" or "poor." This can be tested by taking up a portion on h trowel; the "fat" Avill cling to the trowel while the "lean" will run off like wet sand. The coarse stuff can be tested by voA- fi' ».i 76 CEMENTS AND CONCRETES ing bnquettes and slowly drying; the good will stand a great pressure, whereas the bad will not—in some cases falling to pieces. Some coarse stuff will appear fat on the trowel, but it may be the fatness of mud not the fatness of lime, because sometimes sand is adulterated with fine-screened earth. When this stuff IS made in the form of briquettes and dried, it will be extremely friable and easy to crush; or if put into water until soft, the earthy matter can be seen. Pine- screened earth, when dry and in bulk, does not seem an objectionable material; but in a wet state it is dirt or mud, and should at once be sent off to the works AU limes increase in strength by the addition of sand, being the reverse of Portland coment, which is weak- ened by this addition. Mr. Read made four samples 01 mortar with the proportions of ground lime and sand as follows: "Ground lime mixed with 4, 6, 8 and 10 parts of clean washed sand to 1 part of ground lime respectively. All set and went hard. One of each was placed in water; that made with 4 parts of sand expanded and went to pieces; those with 6, 8 and 10 parts of sand remained whole, and continued to .'(•t harder." The addition of a small proportion of brFck dust to mortar will harden and prevent the disinte- gration of mortar. The proportions are 1 part of bric'c dust, 2 parts of sand and 1 part of lime, mixed drv and tempered in the usual way. Adhesive Strength.—The adhwive strength of mortar vanes according to the amount of sand used. The more sand used in the mortar, the less its adhesion. The following table shows the force required to tear apart bricks bedded in mortar made with the usual proportions of sand at the end of twenty-eight days: PLASTKK, LIME, ETC. ' 77 Adhesive Strenoths of Limes and Cements. Fat lime and aand (ItoS) 4*4 lb«. per 8q. In. Common Has lime and aand II 9 " II II II « II II II II (lto4) 6'A " i< II II Portland cement " ii (lto4) 23 " II II II II II i< II (lto6) 16X " II II II The old mortar which was held in such high esteem by the Romans is said to have consisted of lime mixed with puzzoiana or trass. Trass is a material similar in its nature to puzzoiana, obtained from extinct vol- canoes in the valley of the Rhine, also in Holland, and is largely employed in engineering works. The name trass is derived from a Dutch word meaning a binding substance. Much has been written and said about the ancient and the old Roman mortars, but it may be safely said that, from the year one up to the present time, no cement or mortar has the strength, or could excel, or stand our variable climate as well as Portland cement. The primary cause of the premature deca> which takes place in stuccos and cements, when used externally as a coating to walls, is the presence of muddy earth and decayed animal and vegetable matter in the sand used in the lime and cement. To this may be added the frequent impurities in the limes and ee. ment themselves. The impurities in the sand may be eradicated by a thorough washing, and the lime should be carefully selected, prepared and manipulated. Hav- ing now briefly reviewed the principal parts and process of mortar, the practical conclusions to be drawn 6re, that the quality of the lime is of as great importance as the quantity, and thorough slaking is imperative; that the proj)()rtions of sand may vary con- 78 CEMENTS AND CONCRETES siderably, and that it should be coane and irregular in size, and of a clean and hard nature. The Hardening of Mortar. — According to the remits obtained from tests and experience, the hardening of mortar is due to several causes acting collectively. These causes appear to be absorption of carbonic acid from the atmosphere, and the combination of part of the water with the lime which act upon the sand, dia* solve and unite with some of the silica of the sand is composed, thus forming a calcium silicate (silicate of lime). Some authorities state that the silicate of lime is formed by the reaction of lime and silicate of mor- tar, and to this is due the hardness of old mortar. In mortar from the pure lime, the initial setting is due to the evaporation of water, and to the production of minute crystals of hydrate of lime, which slowly ab- sorbs carbonic gas from the air, the rapidity of this absorption necessarily decreasing in proportion to the difficulties presented to the free access of air. The setting and hardening of hydraulic limes are due mainly to crystallization brought by the action of water on the silicate of lime and not mere absorption of carbonic; gas from the atmosphere, as is the case of fat limes. The Romans were convinced that it was owing to prolonged and thorough slaking that their works be- came so hard, and were not defaced by cracks. Al- berti mentions that he once discovered in an old trough some lime which had been left there five hundred years, as he was led to believe by many indications around it, and that the lime was as soft and as fit to be used as if it had been recently made. Common mor- tar made of rich lime hardens very slowly, and only by the evaporation of the water of the mixture, and by the absorption of carbonic acid from the atmosphere, PLASTER, LIMB, ETa 19 with which it forms a ciyttalline carbonate of lime. Thi8 proce«, however, ig ho alow, that it gave riac to the French proverb that "Lime at a hundred years old is still a baby"; and there is a similar proverb among Scotch masons, "When a h indred years are past and gane, then gude mortar turns into stane." Mortar from the interior of the pyramids, where it has been ex- posed to the action of the air, still contains free lime, although it is five thousand years old. It has been ascertained that in rich lime mortars the carbonic acid penetrates about one-tenth c' an inch into the joint in the first year, forming a skin or film which opposes the further absorption of carbonic acid, except at a decreas- ing ratio, so that the lime remains soft for an indefi- nite period. In illustration of this several cases hav«' been cited, amongst others one by General Treuasart, who, in the year 1822, had occasion to remove one of the bastions erected by Vauban in 1666. After these 156 years the lime in the interior was found to be quite soft. Dr. John, of Berlin, mentions that in removing a pillar of 9 ft. diameter in the Church of Saint Peter, Berlin, eighty years after erection, the mortar was found to be quite soft in the interior. General Pasley mentions several instances at Dover Harbor, and at Chatham dock yard, the latter in par- ticular, when part of the old wall was pulled down in the winter of 1834. The workmen were obliged to blast the brickwork fronting the river, which had been built with Roman cement, but the backing, done with common lime mortar, was in a state of pulp ; the lime used had been prepared from pure limestone or chalk. But it is unnecessary to go back so far for knowledge of the absence of the setting quality in the rich limes, as there have been frequent experiences of it in the pres- S J ■1. 1 i 80 CEMENTS AND CONCKETES out age. While these remarks are true of the richmr limea, many of our limes are comparatively poor in fnrbonate, and associated with silica, alumina, mag- nesia and oxide of iron, which may either be partially (-•ombined in the natural state, or enter into combina- tion with the lime during the process of calcination, pnd these limes might be termed slightly hydraulic. M. Landrin, who submitted to the French Academy • he results of some experiments on the hydraulicity and hardening of cements and lime, came to the conclusion that (1) silicates of lime raised to high temperature «et with difficulty, and in any case do not harden in water; (2) for the recalcination of cements to exert a maximum influence on the setting, in connection with water of the compound obtained, the process must be «*arried sufficiently far for the limes to act on the silica HO as to transform it into hydraulic, and not fused silica; and (3) carbonic acid is an indispensable factor in the setting of siliceous cements, in as much as it is ihis substance which ultimately brings about their hard- ening. The comparative strengths of variouh mortars are shown in the following table: PLASTER, LIME, ETC. I a> • Si" © g a I 1 p o ? U < ceo * • * H f-* «« — f • •-. o V a ■. • «rf ^ «« v^ •« ~^ e-!»-« oi --• •"• SS 9 f^SS^S^ 'e;^ 5S t SSiSS'S^S' ^.1 O •-' i 4.> *rf 41 00 •- • "■OC' COO «^ *• *•< T ^ ^ S9S ISIS IS ^S.SSSS 83S i-« 1^ .-J th i-< 04 <-i e* 01 th 1-S o< SS S : : :SSS §sss «-<■ -H 1-; • • • o o" c) 3 ^ ® ® 88SS8S 8SS S§ 8 888888 888 ffi ?t o) te 00* o' ce 00 o «c ad o j:^::g; i. d -^ «» ©J « « aS t- t- go c* »1 t^ 1-40* ee i^c(iM<^e9M t-ievco i 82 CEMENTS AND CONCRETES Magnesia in Mortars.— Uagnesia. plays an important part in the "setting" of hydraulic limes as well as in Portland cement. Vicat, after many experiments, was led to recommend magnesia as a suitable ingredient of mortars to be immersed in the sea, stating that if it couJd be obtained at a cost that would admit its appli- cation to such purposes, the problem of making con- crete unalterable by sea water would be solved. Gen- eral Gillmore, speaking of the American lime and ce- ment deposits, says: "Magnesia plays an important part in the 'setting' of mortars, derived from the ar- gillo-magnesian limestone such as those which furnish the Rosendale cements. The magnesia, like the lime, appears in the form of a carbonate. During calcination the carbonic aeid is driven off, leaving protoxide of magnesia which comports itself like lime in the pres- ence of silica and alumina, by forming silicate of mag- nesia and aluminate of nagnesia. These compounds become hydrated in the presence of water, and are pronounced by Vicat and Chatoney to furnish gangues, which resist the dissolving action of sea water better than the silicate and aluminate of lime. This statement Is doubtless correct, for we know that all of these com- pounds, whether in air or water, absorb carbonic acid, and pass to the condition of subcarbonates, and that the carbonate of lime is more soluble in water holding carbonic acid and certain organic acids of the soil in solution than the carbonate of magnesia. At all eveats. whatever may be the cause of the superiority, it is pretty well established by experience that the cements derived from argillo-magnesian limestones furnish a durable cement for construction in the sea." In Marshal Vaillant's report to the French Academy oi Sciences, from the Commission to which Chatonev PLASTER, LIME, ETC. 83 and Rivot's paper was referred in 1856, this superiority of the magnesian hydrates is distinctly asserted. A few years ago the French Government Office of Civil En- gineers made a smnes of comparative tests on three sam^ pies each of French, English and German cement, in which the results are given in favor of the German cement, which conteins magnesia to the extent of 2.4 per cent, against 0.26 in the English and 0.32 in the French, and summed up thus: "A great value partly due to the higher percentage of ma^esia contained in it." Gillmore further says that magnesian limestoni' furnishes nearly all the hydraulic cement manufactured in the western part of the State of New York. At East Vienna it has been used for cement, and at Akron, Erie County, N. Y., a manufactory of some extent is in operation. Vieat says: "Having analyzed several old mortars, with the view of discovering, if possible, to what their superior durability might be attributed, I found, in some excellent specimens of very old mortar, magnesia to exist in considerable proportions." The limestones, therefore, from which these mortars were prepared must have contained the silica and magnesia as constituent ingredients ; and it is to be Vemembered that it is the presence of these substances which com- municates the property of hardening under water. Pro- fessor Scorgie says of carbonate of magnesia: "Mag- nesium carbonate is a substance very similar to carbon- ate of lime; it loses its carbonic acid in burning, com- bines with silica, etc., and behaves generally in the same way; it does not slake, however, on being wetted, but combines with the water gradually and quietly sets to some extent in doing so. Magnesium carbonate com- bined with lime, reduces the energy of slaking, and in- creases that of the 'setting' process; when other sub I J 84 CEJIENTS AND CONCRETES stances are prt>8ont, its behavior and combination with them are similar to those of lime. When carbonate of magnesia is present in sufficient quantity, say about 30 per cent., it renders lime hydraulic independently of and in the absence of clay." Colonel Pasley also, by t'xperiments, demonstrated that magnenum limestones are suitable for hydraulic mortars. The foregoing assertions that magnesium carbonate^ -.orebined with lime, reduces the energy of slaking and increases that of the "setting" processes are satisfac- tory and conclusive. Many such evidences showing the \alue of magnesia in hydraulic mortars might be quoted, l>nt perhap.s these are sufficient. Effects of Salt and Frost in Mortar. — Few experi- ments have as yet been made to test the general effects of salt in mortars, though as a preventive of the effects of frost it has been tried with varying results. Tn some experiments, designed to ascertain the effect of fmst upon hydraulic limes and cement gauged with and without addition of salt to the water, cubes of stone w<'re joined together witli cement mixed with water ranjring from pure rainwater to water containing from L* tf» 8 i>er cent, of salt. Before the cement M-as set the l>l()ek.s were exposed in air at a temperature varying fiom 20 to 32 degrees Fahr., after which they were K.'pt for seven days in a warm room. At the end of this time the samples were examined. The cement made with Avater was (juite crumbled, and had lost all its tt'uacity. The cement made with water containing 2 ptr otnt. was in better condition, but could not be described HH good ; while that containing 8 per cent, of salt had not Miffored from its expcaure to the lowest temperature Jivailahic for the purpose of experiment. It is .suggested fl.4 tiracH more lime in the same quantity of water. Here it is to be ob- served—and it is a most important point — that there art- hot limes, such as Buxton, which if they be incautiously mixed with tliem, will bum the sugar, make it a deep brown color, and convert it into other chemical forms, and possibly destroy its value in mortar." The Jaghery sugar used in India is sold in the London market at about a penny a pound. Treacle seems to W the most promising form of saccharine matter; beetroot .sugar is not good for limes or cements. There is a rough un refined treacle which is very cheap, and it is supposed would have an excellent effect. Herzfeld states that he used coarse stuff, consisting of 1 part of lime to 3 of sand, to which about 2 per cent, of sugar had been added, to plaster .some walls in the new building of the Berlin Natural History Museum, and on the day following he found the lime plaster ha hard, but not dry, and then "knocked up" to the re- quired consistency with water (preferably lime-water) and the aid of a shovel and larry. While the staff is tirn:ing by evaporation it should be covered up to protect it from dust and atmospheric influences. It should be used as soon as "knocked up." Setting stuff may be colored to any desired tint, and also mixed with various ingredients to obtain a brilliant and marble-like surface. Haired Putty Setting.— HsLired putty was formerly used to a very considerable extent as a setting coat in districts where the local lime was of a strong or hydraulic nature, not very readily manipulated when mixed with sand, as used for setting stuff. This material is com- posed of fine lime putty and well-beaten white hair. The hair was thoroughly mixed with the putty to toughen and prevent it from cracking. To such an extent was hair CEMENTS AND CONCRETES Portland cements for floating. Sand should not be uni- form in size, but, like the aggregate for concrete, should vary in size and form., A composition of fine and coarse .sand for coarse stuff, unless the sand is naturally so mixed, gives the best results, for as the lime will receive more sand in that way without losing its plasticity it will make a harder and stronger material, whether coarse stuff, setting stuff or for Portland cement work. If there is plenty of fine sand and a scarcity of coarse sand, they should be mixed in the proportion of 2 of coarse to 1 of fine. If on the other hand, there is plenty of coarse fiand and a scarcity of fine, they should be mixed in the proportions of 2 of fine to 1 of coarse. The proportion of sand varies according to the different kinds and qualities of limes and cements, also purposes. Barj^e is some- times used as a substitute for sand. Silver sand is used for Portland cement work when a light color and a fine texture is required. Mastic. — Mastic was formerlj extensively used fot various purposes in which now Portland cement is chiefly employed. It is still used sometimes for pointing the .ioint between the wood frames of windows and the stone work. Mastic is waterproof, heat-resisting and adheres 1 () stone, brick, metal and glass with great tenacity. Maa- tie is made in various ways. Some plasterers make their own, Scotch Mastic is composed of 14 parts of white or yellow sandstone, 3 parts of whiting and 1 part of lith- arge. These are mixed on a hot plate to expel any mois- ture and then sifted to exclude any coarse particles. It is then gauged with raw and boiled linseed oil in the I)roportion of 2 of raw to ] of boiled oil. The sandstone is pounded or jrround to a fine powdered state before PLASTER, LIME, ETC. 97 beinjf mixed. The surface to be covered is first brushed with linseed oil. Common Mastic is prepared as follows: 100 parts of j,'round stone, 50 parts silver sand or of fine river sand, «nd 15 parts of litharge. These are all dried and mixed jind passed through a fine sieve; it then resembles fine saiid. This mastic may be kept for any length of time in a dry place. When required for use it is gauged with raw and boiled linseed oil (in equal proportions) until of the consistency of fine stuff. It requires long and fre- quent beating and kneading— in fact, the more it is knocked up the better it works. Its fitness for use can be ascertained by smoothing a portion of the gauge*with a trowel. If there are any separate parts of the differ- ent materials or bright spots seen the knocking-up must be renewed until it is of even texture. The addition of 15 parts of red lead is sometimes used to increase the tenac- ity of the mastic. Mastic Manipulation.— The walls are prepared for mastic by raking out the joints and sweeping with a coarse broom, and the brick work well saturated with lin- seed oil. Narrow screeds about 1 inch wide are formed in plaster to act as guides for floating the work plumb and level. When laying the mastic it must be firmlv pressed on and the floating rule carefully passed over the sur- face until it is straight and flush. The screeds are next cut out and the spaces filled in with extra stiff mastic The whole surface is then finished with a beech or syca- more hand float, leaving a close and uniform textuiv Mastic moldmgs are first roughed out with Medina or « -her quick-setting cement. The running mold is muffl.'d so as to allow 1/4 inch for the mastic coat. Hamelein's Mastic— Thi^ mastic consists of sand and pulverized stone, china, pottery, shard, to which are Si 98 CEMENTS AND CONCRETES i i, added different oxides of lead, as litharge, gray oxide and minium, all reduced to powder, to which again is added pulverized glass or flint stone, the whole being intimately incorporated with linseed oil. The propor- tions of the ingredients are as follows: To any given weight of sand or pulverized pottery ware add two-thirds of the weight of pulverized Portknd, Bath or any other stone of the same nature. Then to every 550 lbs. of this mixture add 40 lbs. of litharge, 2 lbs. of pulverized glass or flint stones, 1 lb. of minium and 2 lbs. of gray oxide of lead. The whole must be thoroughly mixed together and sifted through a sieve, the fineness of which will de- pend on the different purposes for which the mastic is intended. The method of using is as follows: To every 30 lbs. of the mastic add 1 quart of linseed oil and well mix together either by treading or with a trowel. Aa it soon begins to set, no more should be mixed at a time than is requisite for present use. Walls or other sur- faces to be plastered with this material must first be brushed with linseed oil. Mastir. Cemejit.—mx 60 parts of slaked lime, 35 parts of fine sand and 3 parts of litharge, and knead them to a stiff mass with 7 to 10 parts of old linseed oil. The whole mass must be well beaten and incorporated until thoroughly plastic. This mastic a ment assumes a fine smooth surface by troweling. It is impervious to damp and is not affected by atmospheric changes. TERMS AND PROCESSES. The following descriptions are suited to most locali- ties, though there are districts in the East and South that vary somewhat fronj the processes as described; the difference, however, is so trifling that the regular plasterer will have no trouble in reconciling such differ- ences. Three-Coat WorAra— Three-coat work is usually speci- fied by architects for all good buildings, but sometimes two-coat work is specified for inferior rooms, closets, at- tics or cellars in the same building. Three-coat work makes a straight, smooth, strong and sanitary surface for walls and ceilings when properly executed. The follow- ing is the process for three-coat work, which consists of first-coating, floating and setting. F^rs^Coa;- onally. Square scratching cuts and weakens the rivetw, especially when the scratch is drawn in the same line as the laths. Good work is generally scratched with a sin- gle lath. This, like other scratches, should be drawn in a slanting position, so as to give an undercut score. Sin- gle scratches is the best way for circular surfaces. First score it diagonally across the laths and then crossways diagonally, keeping the scoring rather square than loz- enge-shaped. When too pointed the acute angles are liable to be broken when laying the floating coat. The scores should not be more than I14 inch from center tci center, or less than one inch from center to center. Close scoring weakens the body of the first-coating, while wide scoring affords insufficient key. Scratching with a single lath requires thrice or even more time than if done with a four or five pointed scratch, but the work is stronger, as the body and the rivets of the first coating are not cut too deep or otherwise weakened. In some instances — such as a thin body of first-coating already mentioned— the scoring is so deep that the body of the work is cut into a series of detached parts. By using a single lath or point the scoring is also more uniform and better un- dercut, thus obtaining a stronger surface and a better key for the floating coat. Th(- additional time required for "single scratching" should be taken into eonsidera- 108 CEMKNTS AND CONCUKTES tion, and annotatt-d and allowed for when makings specU fications and estimating. All scratching should be done uniformly, taking care not to miss any parts, especially round door and window frames, wood groundb or where there may be jarring or vibration. On the regular and jiroper scratching depends the key and stability of the succeeding coats. Scratching with the point of a trowel .should net be permitted. The use of a trowel as a scratch is detrimental to the strength of the stuff and the key. The sharp t'dge of the trowel cuts the hair and thus weakens the stuff. The smooth and thin plate of the trowel leaves a smooth and narrow key; the smooth side of the key presents no attachment for the second coat, while the deep part of the key is too narrow to receive its due portion of stuff to fill it up, thus leaving a space for contained air and a more or less hollow and unsound ])ody. Rendering. — The first coat on brick, stone or concrete walls is called rendering. Before laying the coarse stuff the superfluous mortar in the joints of brick or stone walls should be cleared off, as the mortar used by brick- layers and stonebuilders often contains live or imper- fectly slaked lime, which in many instances is the cause t'f the plaster work blowing or scaling oft'. The walls, whether of brick, stone or concrete, should be well swept Asith a hard coarse broom and thoroughly wetted to cor- ii'ct the suction, >»hieh otherwise would absorb the requi- site moisture from the coarse stuff, causing it to become inert and dry, consequently weak and non-adhesive. In some cases the joints of brick-work should be raked out and the face of stone walls roughened by picking. The coarse stuff for rendering walls does not require so much hair or to be used so stiff as for coating lathwork. First- coating or rende«-iiig is generally looked upon as a simple TERMS AND i'ROCESSK.S loa process, but it should be carefully laid and scratched, m it is the foundation for the other work. Float inf/.—Floatinff or second-coatincr, termed "brown- ing," is the layinf? of the second coat of coarse stuflP on the first coat when dry to form a struijrht surface for the finishing coat. If th.; first coat has been standing for some time it should be well swept to clear off any dust that may have cccunuilated during the interval between the application of the coats. Where the coarse stuff is of a porous nature a damp brush should bo pussed lightly over the first coat as the work proceeds to prevent the nudstiirc Iwing sucked out of the second laygr, which, if too dry, would tend to crack and fall away. The coarse .stutf for floating should be used in a softer state than for first-coating, because when too stiff the extra press- ure required for laying is apt to crack the first coat on lath work. It also goes more freely and fii-mly into the recesses of the scratching. (It may be here mentioned that a mortar called "dogga" is extensively used in South Africa for phtster anl building work. Dogga is the ground dug iiy, and tempered with sand, about "2 to 1 for rendering and floating. Heavy ground re«pnres more sand. Lime is very expensive in that couutn' and is only used for the best class of work.) Floating for lime plastering consists of four parts: (1) Plumbing and levelling "screeds'* to act as bearing for the floating rule and running mold ; (2) flanking or filling in the spaces between the screeds; (3) scouring; (4) keying the 'iirfaee. These parts are performed as follows: Screeds^— In good work the wall screeds are plumbed and the ceiling screeds levelled. Wall screeds are plumbed by forming "dots" at the top and bottom of 111.' internal and external wall angles. If there are woo^ grounds to receive wood skirtings they are used instead ,J f j ! 104 CEMENTS AND CONCRETES ai NO. of bottom dota. The dots are made by driving two nails through the first coat into the studs or joints of the wall, allowing them to project about % inch beyond the face of the first coat. Thf position of the top nail should be imnic- diately beneath the cornice bracket. If there is ao bracket the depth of tho cornice should be allowed for. The bottom nail is placed in a lijjc with thr upper member of the skirting moldmir. The nails should be placfed perpendicu- lar with each other, otherwise th<; plumb-bobline will not work in unison with the gauges. The dots are plumbed by means of a plumb-rule. If the walls are too high for an ordinary 8ize form "water blubs" and hollow parts. When th. arface is firm, but not dry, the work is fit to scour. This is done by the plasterer having a hand float in one hand, and a stock brush in the other, with which he sprinkles water on the surface, and vigorously applies the float with a 112 CEMENTS AND CONCRETES rapid circular motion, using a little soft stuff to fill vip any small holes or inequalities that may have been left after the floating rule. Care must be taken that no part is missed or loss scoured and that the whole surface is thoroughly and uniformly scoured. The floating should be scoured twice, or for best work three times, and allow- ing the work to stand from three to five hours, accord- ing to the state of the atmosphere, between the first and second scouring, and one day betvopn the second and third scouring. The final scouring should be continued imtil there is little or no moisture left on the surface, 'i'o obtain the same strength and solidity, all other things being equal, coarse stuff composed with a weak lime or containing inferior or an excess of sand, or having in- sufficient hair, or sparsely tempered and used in an over-soft condition, requires a greater amount of scour- ing than coarse stuff which is composed with a strong lime, or containing good sand and in due proportion, or with an ample quantity of hair, or well tempered, and used in a moderately stiff yet plastic condition. Even with extra scouring the ultimate strength of inferior coarse stuff is remote and doubtful. This simple mat- ter is a witness to the fact that inferior or insufficient materials require more labor than good and sufficient materials and that the results are somewhat vague and often unsatisfactory. Keying. — All plastic materials have great adhesive powers, especially to each other. Yet when laying a thin body of fine material on a coarse material which has a more or less smiK)th, dry and absorptive surface, such as laying setting stuff on floated coarse stuff, the adhesion is partly nullified. Portland cement or hydraulic limes, which .set nearly jus soon as laid, reciuire no scouring, and being left from the floating rule with an open grained or TERMS AND PROCESSES 113 rough surface, a natural key is obtained for the final coat; but coarse stuff, which only sets or becomes hard by evaporation of its moisture, must be scoured to con- solidate the yielding and soft body. Scouring leaves a i'lose-grained and somewhat smooth surface, offering lit- tle or no key to the setting coat. The floated coat being often dry before the setting coat is applied, the suction varies greatly; sometimes it is regular, at other times it •iccurs in patches. Sometimes the suction is so excess- ive that the setting stuff dries up and peels as soon as laid, and in other instances the reverse occurs, there being no suction at all. In the latter case the setting stuff runs downwards in the form of globules or in rivu- lets. These defects may to a certain extent be corrected by laying the setting stuff while the floating is still jri-een, or by saturating the surface if the floating is dry. Yet to obtain permanent cohesion in the two coats it is necessary to key or roughen the surface. This is best done by brushing the surface as soon as scoured with a stiff whalebone broom or with a wire brush. A common plan is to dry scour with a "nail float" — i. e., a hand float with the point of a nail projecting about 14 inch beyond the sole of the float. When this method is em- ployed the float should be worked in a close circular motion so as to leave a series of close and irregular in- dents. The usual and careless way of working the float in a wide circular motion leaves the indents too wide apart to give a sound and uniform key; indeed, this method is of little service. A new tool for keying coarse stuff has been recently introduced, which is called a ' devil" and is similar to the nail float, with the excep- tion that there are four nail points projecting on the sole, one of which is placed about IV2 inches from each angle. The process of keying the coarse stuff with this I' f ■ 114 CEMENTS AND CONCRETES is termed "devilling." The work is more speedily and better done with the "devil" than with the nail float. After the floating is finished the next part of interior plaster work is the running of the cornice, and then fin- ishing the ceiling and walls; but in order to continue the methods of setting, the running of the cornice, etc., are described in subsequent pages, and the setting and other parts of wall work are first described a^ follows : Setting. — Setting is the laying and finishing the final coat on floating, termed "finishing," and "hard finish" or "putty coat." In the best work great skill and care is required to make the surfaces perfectly true and uni- form in color, smoothness and hardness. The material for three-coat work is generally known as "setting stuff." The mode of making has already been de- scribed. Setting stuff should not be applied until the floating is quite firm and nearly dry, to allow for any contraction that may take place in the floating. If the floating should become quite dry during the time re- quired for cornice and ceiling work, or where subjected to strong winds or a warm atmosphere, it should be well wetted a d \v or two before the setting coat is com- menced. This prevents the too rapid absorption of mois* ture from the setting coat and gives a closer union of the floating and setting coats. Before wetting copi- ously, a small portion of the floating should be tested with a wet brush to ascertain the degree of suction. In some floating there is no suction, or at least there is none until the surface has been dampened and the glaze and sometimes grease has been washed off. Glaze is caused by slightly hydraulic lime, also by insufficient scouring. Glaze is more noticeable on first-coating which has been left smooth by the laying trowel. Grease occurs through friction, also dirt where the float is left I TEKMS AND PROCESSES 115 long exposed. These matters of excessive and non- suction, dry, glazed or greasy surface, either singly or in combination, also smooth or uniteyed floating, are the cause of cracked or scaly setting, which one sees more or less in a plaster career. It is therefore absolutely neces- sary, to insure perfect cohesion of the two coats, that the floated surface should be uniformly keyed, clean and damp before the setting coat is layed. Setting consists of laying the stuff, scouring, trowelling and brushing the surface. Laying Setting Stuff ;i— The setting stuff is laid in two coats, the second following immediately upon the first. The laying is best done with a skimming float, which leaves the face of the first coat rougher to receive the second than if done by a laying trowel, which leaves it smooth. The second coat should also be laid with a skimming float, which leaves a more open grain for the purpose of scouring. When laying setting stuff some men take a trowelful or skimming-floatful off the hawk and stoop to spread the stuff from bottom to top with an upward motion, laying the joint with a return down- ward motion ; but a smart man can take a trowelful or floatful of stuff and spread it with a downward motion from top to bottom and lay the joint with the return mo- tion, this saving one stoop in each spread or floatful. This is similar to laying setting stuff on a ceiling. A man who hss a thorough command of the trowel hand always lays the stuff in a long even spread outward, and lays the joint with the inward return motion. After one side of a bay or wall is laid the surface is then scoured, trowelled and brushed. Scouring Setting Stuff.— The importance of good and sufficient scouring of setting stuff with water cannot be too strongly insisted upon. The scouring and the water IM 119 G£M£NTS AND CONCRETES combined consolidate, harden and render the surface of a uniform texture and evenness. The work must be well and thoroughly scoured, twice with water and an ordi- nary hand float and finally with a cross-gained flotit. The hand float is worked with a short and rapid circular motion and sprinkling water uniformly with a stock brush until the surface is uniform in moisture and tex- ture. After a rest to allow the stuff to shrink the scouring is repeated, and then it is ready for the final scouring. This is best done with a cross-grained hand float, which, having sharp square edges, cuts off all ridges and leaves the setting with a uniform and even surface that cannot be so quickly or as well done with an ordinary hand float. Water is more sparingly used for the final scouring, using only as much as will moisten the surface and allow the float to work freely. The scouring is continued until a dense, even and close-grained surface is obtained for the trowelling. Trowelling and Brushing Setting Stuff. — Trowelling setting stuff is best done by the use of a half worn trowel (commonly called a "polisher"), the edges of which should be perfectly straight and parallel. Some men use an old and worn trowel with the point narrower than the heel. This shaped trowel should never be used for high class work, since, not being parallel, the press- ure when trowelling is not equal, and the heel or widest l)art is apt to score the surface of the setting. The trowel and water should be perfectly clean to prevent any discoloration. The trowelling should be done by one man following up the other, who is finishing the final scouring. This is done by the plasterer having a polish- inf» trowel in one hand and a stock brush in the other, with which he sprinkles water on the surface and works the trowel in long and vigorous strokes, first downwards TERMS AND PROCESSES 117 and upwards, and then croggways or diagonally. This in repeated, using the water more sparingly and finishing or "trowelling off" with an up-and-down motion and leaving the surface free from "fat" or "glut." The work is then brushed with a wet stock brush, first up and down, then crossways, afterwards up and down a sec- ond time. The brush is then semi-dried by violent shak- ing, or rubbing on a clean board, the work again b^'ing brushed as before and finished perpendicular. Oencral Remarks on Setting.— When the work is re- quired for painting the setting stuff is laid on the form of screeds, and when firm the intervening spacte are laid flush with the screeds and the whole surface ruled fair with a floating rule. Should there be any hollow or soft places (the latter being liable to shrink), they are filled in with more s. r stuff and ruled over again. rh:s IS repeated until ti whole surface is true and ni- form in thickness and r'.rmness. The whole surface ^ be scoured, trowelled and brushed in one operation. This method has the advantage of saving joints at the connections between the height a man can lay and finish the setting stuff. Joints, unless carefully done, are an eyesore, as they are liable to be moi'e or less discolored and uneven on the surface. The best method for making joints and settmg stuff, where it is inconvenient to lay and finish the whole surface in one operation, is to leave the edg. of the joint untrowelled, leaving a scoured margin so that the adjoining portion can be laid and scoured with- out spoiling the trowelling of the first portion. For in- stance, when setting the walls of a room one scaffold high the top parts are laid down to the level of the scaffold, or as far as convenient, and the surface scoured and trowelled. The latter must not extend to the end 118 CEMENTS AND CONCRETES of the scoured part, ho as to leave an untrowelled margin alwut 4 or 5 inches wide until the scaffold is struck. After the scaffold is removed the lower portions of the walls are laid tiush with the untrowelled mar^rin, and tlu'n the surface w scoured as before, always Koinj? well over the joint. The surface is then finally scoured with II cross-grained float, taking care to moisten and roscour the untrowelled margin to render the whole of the scoured surface equal in texture and moisture for trowel- ling. The surface is then trowelled and brushed as al- ready described, taking care to go over the trowelled and l»rushed joint. By this method no joints are visible, and an even surface is obtained. When the suction is slow «»r irregular, causing the setting stuff to run or be soft in places, float the surface with a darby until sufficiently fair and firm to be scoured. A darbj- is very usefid for forming a fair surface on setting stuff before scouring and trowelling. It forms the next best surface to a ruled surface, A darbied surface is better and truer than a laid surface. No more setting stuff s'lould be laid than can be con- veniently finished in one operation or day. Where prac- lieal, one side of a wall should be finished in one piece, and sufficient men should be employed thereon. If the room is not too high, one man or set of men may do the upper part, while another man or set of men does the lower part. The joints are then made while the settmg stuff is green. In high rooms, several sets of men work together on different scaffolds, each about 6 ft. 2 in. apart. All angles should be ruled in with a long float- ing rule. External angles are sometimes formed by nailing a running rule or a straight edged plumb on one side of the wall, to act as a guide, but external angles &tv generally finished with a run cement bead or an arris. TERMS AND PROCESSES 119 An thioknosM of Vu inch of Hctting coat when fir.isht'tl uivj's tho host rt'snlt. It Hhould not oxeofd 3-16 itit'h, or Ik- Ikss thwii l-Ki iti'.-h i.: thickness. If too thick, it iH liable to criick and flake; if lOo thin, it iu liable to ptH'l. Where extra «trenjfth, and cohesion between tlie tloatinR and Hettinj; coats is desirable, the first coat of the settiriu has a little white hair mixed with it. White hair does not show throu^'h the last coat. Common Sett iny.— Common setting for wall and ceil- ings is j;euerally u.sed for second-class work. It is done liy laying one coat of setting stuff with a skimming Hoat, aind scouring and trowelling once and brushing twice. Where the floating cracks by contraction, or by using in- siinicient hair in the coarse stuff, or by want of scouring, or where the work is green, the cracks are knocked in uith a hammer. The indents are then filled up with gauged st'tting .stuff, and the whole surface laid with a •oat of this material, on which n coat of neat setting stuff is laid, scoured, trowelled, and brushed in the usual v.iiy. Shimming. — Skimming is an inferior class of setting, iiiid is only used for the mist common work. It is done It.v laying a coat of fast-setting stuff with a laying trowel. The .stuff is ski^nmed over the floating as thin as possible, using only as much stuff as will whiten and smooth the floating surface. It is trowelled once, and brushed as .soon as laid. Colored Sctting.~A beautiful color and brilliant finish for walls is obtained by mixing an equal quantity of sifted marble dust with setting stuff* id using this "marble .sotting stuff" as a final coat. Ordinary setting stuff is greatly improved by substituting a part of mar- ble, or alabaster, or gypsum dust, equal in bulk to half the sand wnerally iis.-d. The mai-ble dust should be a.« -i I, liiL 120 CEMENTS AND CONCRETES ,,.,! coarse as the sand. Crushed spar is sometimes used in setting stuff to obtain a sparkling surface. Barytes, sco- ria, and slag are sometimes used as a substitute for sand, for coloring and hardening purposes. Brick dust is also used for coloring, and weather and heat resisting pu im- poses. Ground glass as used by Indian plasterers gives a sparkling surface. Setting stuff may also be colored with the same materials as described for colored stueeo. Where marble d'jst or any of the above materials aiv used, they should not be added until the setting stuff is required for immediate use. They should not be used until perfect amalgamation ha* ensued. Gauged Setting. — Gauged setting is used where the floating is soft, or where the work is required for imme- diate use, and also for finishing gauged floating. This is performed by one man laying the gauged stuff with a skimming float, while his partner follows up with a darby to lay the surface fair. Another batch of setting stuff is then gauged, and one man lays a thin coat with a trowel, and the other man follows immediately and trowels the work before it is set. The surface is finishetl by brushing with a semi-wet brush. Gauged setting should never be scoured unless the size water is used in the gauge to delay the setting, as it will kill the plastei- and render the stuff useless. Even if size water is used, the scouring must be slightly and quickly done. If a gauged surface is desirable, a fair and hard surface is obtained by simply darbying and trowelling as soon as laid. Gauged Putty ^Se^j— Ceilings are sometimes set with gauged putty. This is best done by first laying a "scratch coat" of gauged putty with a skimming float, and, then passing a hand float over the surface (before the stuff is set) to hiy down any ridges, and make the TERMS AND PROCESSES 121 surface more even to receive the second coat. This ig laid with a laying trowel, and then trowelled before the stuff is set. The surface is then finished with a semi-wet brush. Jrowelling after the stuff is set, or even has begun to set, kills the stuff, and causes it to peel \ little washed sand added to the putty makes a stronjrer surface, and not so apt to peel. Putty Set.— In some districts common ceilings are fin- ished with a thin coat of neat lime putty; but unless th.' putty is made from grey limestone, or is of a hydraulic, nature, the work is more or less weak, and in most ca-st's practically useless. Internal Angles.—The setting coat of internal angles on room walls should be ruled fair and then cleaned out with a feather-edged rule. Before scouring the settin- stuff, the angles should be scpiared and made strai-lii with an angle float. The angle float is a tool now unfo,- tunately seldom used, but it is the best tool for makin- a true angle. In the absence of an angle float, the an-l^' should be made fair and square with a eross-graim-d float, and finished with a margin trowel or the heel of i laying trowel. The common way, used in some districts of finishing an angle with a garging or pointed trow.l' should not be encouraged, as it i^ impossible to make a true angle with a tool of this shape. External Angles.—The external angles of room waJIs and windows are generally finished with a bead but ii, some instances with a plain arris, splay, or small' mould- ing. They are formed with Parian or other whit.- cement, and usually run after the floating is done The floating should be cut square on each side, and down to the brick or lath work. After dusting and wettin- th.. foundation, a running rule is fixed on one side, and thni the bead or arris is run. Th(^ run edges form bearings in'- t' Vii 322 CEMENTS AND CONCRETES for the setting coat. A run arris is more speedily done and truer than a ruled and trowelled arris. In some districts wooden beads are used for external angles. The iloating is cut down at each side of the bead, to allow the fjuirks to be formed when the setting coat is laid. When the setting coat is trowelled, the quirks are formed by iipplymg a large-headed nail on the bead, and drawing it up and down to cut the stuff out. They are then fin- ished by working a laying trowel up and down until smooth and true, and afterwards wet-brushed. The head quirks are sometimes cut out by aid of a wooden template, also by laying a straight edge on the A'ork as a guide for cutting the stuff out. They are then finished with a trowel and brush, as already described. Skirtings. — Skirtings or base, are sometimes formed la wood, but are often formed in cement. Cement skirt- ings are far more sanitary than wood skirtings, as the former connects the wall and the floor in one solid fire- resisting and vermin-proof body, whereas wood skirtings, •twing to their nature and construction, afford a ready iiarbor for vermin, and offer but little or no resistance to damp and fire — indeed, their hollow formation pre- sents a vent in the case of fire. Parian or other white cement is generally used where a fine finish is desirable, and Portland cement where the work is exposed to wet ;ind hard wear. Skirtings are generally run by first roughing out the plinth by aid of a gauge rule bearing on the floating, and then forming a running screed, and lixing a running rule on the plinth. The skirting mould- ing is then run in the usual way, after which the running rules are taken off, and the plinth set. The mould plate shonld be cut to form about 1 inch of the top part of the plinth, to form the arris, and a bearing when setting the plinth. The annexed illustration (No. 4) shows the Tii^MS AND PROCESSES 123 method of forming the core and plinth, and running the moulding. Fig. 1 shows the gauge rule (G) in posi- tion to form the core (C). The gauge rule is from 3 feet to 4 feet in length. The plinth is formed by first roughing out willi gauged stuff, and then drawing the gauge rule ahmg the floating to form the core, and a fair surface for the running screed. Fig. 2 shows a sec- tion to form the core (C). The gauge rule is from 3 (R) fixed on the plinth or core (C). r tSkirting Formatij.v. NO. 4. l4 Two-Coat 'n'orA-.— This is a cheap method of plaster- ing, and only used for eommration causes tli,' .rment t,) swell, and in many in- stances to peel or t;.ll oft". Kv,'n if it does adhe.v- it TK'ver attains its due hardness. an,l thus is no bett.T than ordinary plaster, rnfortunately a.l.ilt. ration briu-s TERMS AND PROCESSES 183 diBomlit on the (H'ni.'nt nnd the tnuK'. The only remody iM proptT Hupprvwion by a plHNtcior who posNOiises a thor- ouKh knowl<'«l>r«' of plastic nmterinls and tho methods of nsinj: them. If plasfererH were awarded eertifioate« of i'ompeteriey, adidteration would b,. prevented, and t^ood work ensured. Honest employers wn.dd lluw this ben.- Heial. for seamper-. can only thrive wher«' there is a luatin. or floating I'V ',:] l> 134 CEMENTS AND CONCRETES ceilings, empty a sackful, or half a sack aecordini? to requirements, in a clean banker; then add the sand in the proportions already given, and thoroughly mix the cement and sj-nd while yet dry; then form a ring and I)our m the water, taking care not to pour in too much as It must be gauged, and used as stiff as practicable.' 1 here will be no difficulty in thus using it, as it will take .some hours to set, according to the season of the year (qineker m summer than in winter). When the water IS m, add the hair (which must previously be well beaten and soaked), and gauge he whole mass together. Then begin the first coating, ,ratch it in the usual manner ^.-ushed with a coarse broom to form a key for the finish nig coat If there is a Parian cement cornice to be run tlu' usual mode for plaster and putty is adopted for the rutunng rules. The screeds should be made sufficiently smooth to run on, without forming an extra thieknes. o' TERMS AND PROCESSES 135 '■\ traversing screed. The cornice is roughed out with the same kind of material as used for the floating, employ- ing a muffled running mould for running the rough stuff. It may not be practical to rough out all the cornice at once, as this stuff does not set quick, therefore it may be necessary to leave it for a time until the stuff stiffens. Nr definite directions can be laid down in this matter, as i\-i suction is greater in some seasons and rooms than in < aiers. A little extra hair, also extra stiff gauging, is of .service to make the stuff cling together, thus allowing the work to be roughed out sooner. The running moulds must be made of strong zinc or copper (no iron to be used on any account). Where the work is in cornices, skirtings, achitraves, &c., the mould should be muf- fled with a zinc or copper plate. If there is only a small (juantity to be run, a plaster muffle may suffice. After the cornice is roughed out, it is finished with neat Parian, and then the mitres formed in the usual way. In preparing to finish a large spuee (ceilings or walls) it is absolutely necessary that no more should be laid than can be finished the same day, therefore as many men should be put on the job as will accomplish that object, as no sign of a joint should be shown on the sur- face. In the case of large or high walls, the scaffold should be so arranged that the men can work the whole wall from the cornice down to the skirting in one op( ra- tion. If a wooden skirting has to be subsequently fixed, one end of the rule bears on the fixing grounds ; but if a I'arian skirting or base is specified, it is generally run before the walls are finished, and allowed to get thor- oughly hard, so as to bear the end of the rule used for the finishing coat. The lower end of the rule is cut to fit the upper member of the skirting. Another way is to nail a board onto the end of the rule, so that it bears i 136 CEMENTS AND CONCliETES IT well on the plain plinth and clears the members of the skirtijijr. The cornice screed must l)e Keyed with a draj? bef(!re the finishing coat is laid. For large cornices il is often desirable to traverse the running screeds. In this ease they must be cut down to the floating, leaving only the margin formed by tb- running mould. This margin forms a bearing for the top end of the rule. In some instances a special margin or bearing is cut at the outer members of ruiniing moulds for cornices and skirt- ings, and when run they form a beaiing for the floatin^^ rules. When ready for the finishing coat, empty as nuich as re(|uirod of neat Parian cement into a clean banker, and gauge it smooth and stiff; then soften it down to the desiied consistency, always bearing in mind not to make it too soft, as sloppy stuff for any pui-pose is over 1o be avoided. The gauging should be so arranged that when one batch is in use anoth'^r one is ready, which prevents delay in laying the whole space, thereby ensur- ing similarity of texture and results. The thickness of the finishing coat should not exceed Vts inch. AVhen there are about a dozen yards laid, two men must follow- on and rule the surface fair from screed to screed on ceilings, and top and bottom on walls. The greatest pos- sible care must be observed that the whole surface is ruled in fair and uniform, otherwise the surface will be imperfect. White cements, owing to the suction of the walls or ceilings, have a tendency to shrink more or less, awon)- ing to the stiffness of the gauge and the section, theiv- fore they must be ruled in twice. When the coat already laid is firm, then some more cement, gauged soft.-r than the finst, should be laid thinly all over, and ruled ascar-- fully as before. Having done this the whole surface is TERMS AND PROCESSES 137 J '4 nearly ready for scouring. It is allowed to stand fur an /hour or two, or until quite firm. If scouring is at- tempted before, it will work into hollows, and a bad job will be the result. If the finger cannot make an im- pression upon it easily, it is sufficiently firm, and then all hands begin to scour the work, using very little water, and working the hand float with a circular motion. The hand float must not be worked long on one spot, but kept moving over all the surface within reach, and working back again until the whole surface has an even grain or texture. The whole work must be scoured twice to bring it- up to a fine solul surface. When there is about half of the wall scoured, two or more plasterers can continue the .scouring, and the remainder of the men go back and •start the trowelling. This must be done with good long strokes, using very little water, and taking care not 1o dent the surface with the trowel. After the men haw finished the scouring, they come back and start at tlu" beginning with the second "trowelling off" or final trowelling. This is done th vertically and horizon- tally, and when the work begins to harden, the trowel is laid on the near edge and worked with a cutting motion downwards. This is rerated ail ov.t the work until every particle of glut or "fat" is elean-d off the surfac. If the work has to be polished, the cutting action with the trowel must be followed with a D-ineh joint rule and a damp brush, but the work must be hard before this last can be attempted. Work carried out on the abov plan will reflect credit on the material and the workers The same methods apply equally to Keen's and IMartin's Martin's is preferred by some plasterers for rumiin-' cornices because it sets quicker than Keen'.s. For plain surfaces, such as walls and ceilin-s. it s.-ts too quick and has to be "kilbd" (that is working the stuff again fc i 138 CEMENTS AND CONCRETES and again with water until the initial set is stopped or "dead") before it c je conveniently used. Although it finally sets fairly uard, it never attains the same de- gree of hardness as Keen's or Parian. Several other white cements and plasters have been introduced during the last two decades. They will be noticed later on. White Cement Efflorescence. — For work that has to be painted, care must be exercised in the selection and manipulation of the materials used for the plaster work, so as to avoid as far as possible subsequent efflorescence. In the manufacture of Keen's, Parian, and Martin's cements. Keen's original process is doubtless the best. It requires, however, great care in carrying out, the chemicals used and temperature employed lequiring to be suited to the peculiarities of the gypsum. The de- .sired result is extreme hardness, combined with non-ef- florescence. Keen's cement is practically non-efflores- cent, as if applied on a dry wall containing no soluble salt, in itself there would be no efflorescence that would spoil paint. Perhaps one should not say that Keen's cement, or at least all brands of it, are absolutely non- efflorescent, as there is generally a powdery coating comes t)n the surface, just enough to whiten a colored hand- kerchief, something like the coat of puff powder used on some female faces. On no account should Keen's cement be used on walls as a preventive of damp, as it is useless for this purpose. If used on a damp wall, or in places exposed to atmospheric influences, it will effloresce more or less, as its base is gypsum, which al- ways remains soluble. In damp situations the walls should be rendered or floated in Portland cement before till' finishing coat of Keen's cement is laid. The same remarks apply to Parian and IMartin's cements. The TERMS AND PROCESSES 139 Keen's cement manufactured by Hunkin's and Willis, St. Louis, Mo., is practically non-efflorescent. Cornice Brackets. — Brackets or cores are used to de- crease the amount of materials and weight, and also to form a foundation and support for cornice or other mouldings. For large exterior work they are generally formed with stone, and for small work bricks, tiles, or slates are used, which are builc into the walls as the work proceeds, and roughly fashioned to an approxima- tion to the profile of the intended cornice or other mould- ing. For interior work the brackets are sometimes con- structed with metal lathing, also with spikes and tar bands, termed "spike and rope brackets," but the oldest and most general way for cornice mouldings are "lath brackets. " The " brackets ' ' on which the laths are sub- sequently nailed are cut out of boards from % inch to 11/2 inches thick, according to the size and form of the cornice. The section of the brackets should be about 1 inch less than the profile of the proposed cornice to allow for a thickness of lath and plaster. The thickness of the plaster should not exceed 1 inch, or be less than 1/2 inch. If too thick it is a waste of materials, and the undue weight is apt to pull or spring the laths from the brack- ets, and if too thin the stuff is apt to crack. The profile of the bracket need not follow closely that of the cor- nice, but a general or approximate outline of the most salient members followed. Any thin projecting mem- bers may be subsequently strengthened by means of I)rojecting nails and tar-strings similar to a spike and rope bracket; also by using extra hair and plaster in the roughing out stuff. Brackets for enriched cornices re- Muire special notice. Unless a due allowance is made for sinkings for the thickness of the cast enrichments and a correct form of bed, there will be unnecessary trouble til : f ■tin i 140 CEMENTS AND CONCRETES I ,( in cutting and hacking the lath work and brackets wlieu the running of the cornice is comincnct'd. There is ii marked difference between the section of a runnin-j mould for an enriched cornice and that of a plain coi-- nice, even if the profile of both ar(> the same. To avoid mistakes of this nature the plasterer should supply tlio carpenter with a section of the brackets, taken after tli^ bed of the enrichments Ure set out on the tracing of the proposed cornice. Skeleton brackets is a term applied to a method sonic- times used for coring out angles, to save materials wheie there are no brackets, and for small mouldings. This is effected by placing the mould in position and then tittini,' a piece of lath in a vertical position, and allowing a space of about % inch from the face of the lath to the nearest part or most prominent member of the mould. A murk is then made on the ceiling and wall at the top and bot- tom of the lath. Similar marks are made at the other end of the wall and ceiling, and then a line is struck on the marks, from end to end of the ceiling and wall, by means of a chalk line. The stuff which forms the paits of the screeds inside the lines is cut away, dusted, wetted, and then a narrow strip of gauged coarse stuff' is laid along the lines where the ceiling and wall screeds aie cut, and the laths which have been i>reviously cut to tlie length of the first or trial one are fixed vertically into the gauged stuff, keeping them apart as in ordinary lath- ing. They are further secured by laying strips of gauged stuff on the outward surfaces at the top and bot- tom ends. After the stuff is set, the cornice is run in the usual way. Cornices. — Cornices, either plain or enriched, are fonred with a running mould cut to the profile of tlie intended cornice. The formation ( f cornices consists of TEKMS AND PKOCESSES 141 coTustructinp the mould, making the runniDg screeds, fixing tlie riuiniiig rules, running the cornice and mitring th(? angles, with tht; addition of fixing the cast ornament lor enriched cornices. Cornices were formerly run in short lengths and in sections. Two, three, and even four moulds were employed for cornices that are now done with one. For large cornices, where the mould is diffi- cult or sluj^h to run, or apt to jump, the bearings should be greased or brushed with soap or dusted with ti I)o\vdcred black lead or French chalk. Running moulds .ire run in some places with the left hand, from left to light, and the mould plates are also fixed to the left hand side, having the bevelled part of the stock to the right or running side. In America the plates are fixed oh the running or right side, and the mould is run with the right hand from right to left. The way of running from left to right with the left hand allows more freedom, especially in small mouldings, for the right or trowel luind to assist in feeding the cornice with the stuff that ?zHthers on the mould. It also gives more freedom to Ills partner who is laying on the stuff, as with the hawk in his left hand and his trowel in his right he is able to work in a natural position, namely, from left to right, as in laying coarse or setting stuff on walls, whereas, when llie r.iOuld is run with the right hand, and from right to loft, the worker has not so much {)ower or freedom in assisting to feed the mould with his left hand. His part- ner, who is laying the gauged .stuff", is working back- handed, and if using a laying trowel, can only work from its heel instead of from the point as is usual; and if using the large gauging trowel for laying on every trf)welful used nnist he put on with a backhanded turn. It may be a matter of opinion as to which method is betcer. and de|»ends a good deal upon which way the man jTr' 142 CEMENTS AND CONCRETES has been taught, but the manner of rtmning the mould and laying on of stuff from left to right, the same as in writing, is the most natur-1. Running screeds are used as bearings for running moulds. They are com- posed of gauged stuff, and made straight with floating rules. Screeds for cornices are formed with raw or with gauged coarse stuff. They are next traversed. The line of the screed is got by placing the running mould in its true position or at one end of the wall, and mak- ing a mark on the floating screeds at the outside of the nib and the bottom of the slipper. The same operation is repeated at the other end of the wall, and a continuous- line from one mark to the other made on the ceiling wall by means of a chalk line. A narrow strip of gauged putty and plaster is now laid on the lines by one man, while his partner follows on with a traversing rule, work- ing the rule with a slanting motion, and moving back- wards and forwards until the screed is just and true. Where the walls are very long, running screeds are done by two men working a long straight edge or floating rule. The screed is afterwards further fined by draw- ing a cross-grained hand float three or four times over it in a longitudinal direction. Where the coarse stuff screeds are not gauged, the running screeds are made in a similar manner, but the putty is mixed with an equal proportion of setting stuff before gauging. The addi- tion of sand gives more resisting power to the wear of the nib and slipper of the running mould. The run- ning screeds are made on the long sides of the room, and when set they give a bearing for the end screed in its true position at one end of the wall. Fixing the running rules is the next operation. This is done by placing the running mould in its true position at one end of the wall, taking care that the mould is TERMS AND PROCESSES 143 "square," that is, that the perpendicular parts of mem- bers are plumb with the wall. This may be tested with a plumb bob hanging over the side of the mould, and by seeing that the line of the plumb bob hangs properly over a marked line which has been previously made by squar- ing off from a square member or by extending a parallel line from an upright member of the mould. When the mould is plumb and square, a mark is made on the ceil- ing screed at the outside part of the nib, and another made on the wall screed at the bottom of. the slipper. The same operation is repeated at the other end of the wall, and the line extended from mark to mark by using a chalk line. The line in this case should be blackened by means of charcoal or burnt stick, as it shows better than a white line on the light-colored screeds. As the chalk line may sway when striking the wall line, thus line should not be trusted for fixing the running rules to. This may be proved by placing the mould every 3 or 4 feet apart in the length of the wall, taking care to keep the outer edge of the nib at the ceiling line; then marking with a gauging trowel at the bottom of the slip- per. Nails are now driven into each of these marks and left projecting as a guide for fixing the running rules. The running rules should not be less than 21^ inches wide or more than Sy^ inches wide and Y^ inch thick, being made out of good redwood or pine planed on both sides and edges. The rules are now fixed into the wall screed either by nailing them to the studs or into the joints of the walls. They are also fixed by wetting one face of the rule and laying dabs of gauged putty and plaster about two feet 6 inches apart. The rules are now pressed on the wall while the stuff is soft, taking care not to force the guide nails out of position. The rules are further secured by laying patches of gauged li;i ■|l 'it • i;V 144 CKMKNTS AND CONCKETKS stuff undoriu'Hth the rule partly on the wall and rule where the dabs aiv. When the rules arc fixed by nail- ing, it is apt to crack the first-coat of floating, and the joints of the wall are not always easily found. The coarse stnflf for the first-coat of cornice brackets should ' e extra hain-d and carefully scratched to t'ivo a strong foundation for tlu' following coats of jraujred stuff, which in many instances is extra thick at bold or projectiniy: parts of the motihlings. For larjre monldinjr and wire lathinjj it is best to leave the brackets uncoated when first coating the general work until the cornice running is commenced, and then to rough out the whole cornice from the lath work with gauged coarse stuff. This gives uniform suction aMlH.ster muffle or muffin plate, as the case may be, is taken off. Jitid the ninninjr with fine jjauped putty commenced. The prauge board and all tools should now be cleaned to free them froni jrrit. A ring of putty is formed on the j.'!ui«e board, leavinj: the bottom of the board clear: Milter is put in the ring and the plaster quickly and evenly sprinkled over the water, taking care not to sprin- kle it on the putty ring. The plaster and water are mixed together by stirring with the point of a trowt'l. The putty is then (piickly mixed with the gauged plaster by using the trowel and turning it over with the hawk. It is put on with n large gauging trowel, or if the mem- bers are large, with the laying trowel, following the form of the mouldings. The mould is then run along by one man, who also feeds the moulding with any stuff that may gather on the side of the running mould. This operation is continued until all the members of the mouldings are filled oiit. A thin gauge of fine putty, having less plaster than the previous gauges, is lightly drawn over with a trowel, or brushed over the Hat n».>m- bers, and thrown with a brush for small or dry mem- bers. This mould is thin (piickly and steadily run along the cornice from beginning to end and finished. If the moulding is extra large =n girth, or a long length of moulding has to be run. extra men are required to lav tho stuff, while two may be neces.sar\' to run the mould. u ■■'■ I ■ ..■ft 146 CEMENTS AND CONCRETES When running small mouldings, sny of 10 o** -.2 inches in girth. *>'>f "lan can run and feed the mould while his partner iM laying on. When all the mouldings are v\m around, the running' rules are taken down, the screi'ds cleaned and scraped, ami any hoK's or defects causeil by naila or patches used for the rules made good by fill- ing up with gauged putty. If soap, black lead, or any other materials already mentioned are used to aid and case the running of the mould, they should be scrajH'd off with a drag as soon as the cornice is nni off. other- wise they will prevent the finishing coats for wall and ceiling from adhering to t'.iose parts. To S( t Out and Construct Corinthian Entablalurr. — To ena]»le (he pla.sterer to set out a full si/e or working drawing from the architect's design, also to comprehenil the cornice and the architrave, which are sometimes used alone or as separate mouldings, their proportions with that (f the entire entablature are given. The entabla- ture and the details of the enrichments of the coffers and modillions are shown on plate. The whole height of the entablature is divided into ten parts, giving three to the architrave, and three to the frieze, and four to the cornice, as shown by the finst upright scale at Fig. 1. This figure shows the combined section and elevation of the entablature. The height of the architrave is subdivided into five parts to form its members, as .shown by the second upright scale. Projection is taken from the lower fascia, and is equal to one-fourth part of its height. As the cornice of the Corinthian order is frequently used alone as a separate moulding, an enlarged view with figured details is given, see illustratiou Fig. 4. It is necessary that the details of the cornice should be mastered befox^ proceeding with the entablature. See Plate 1. TERMS AND PROCESSES 147 With regards to the enrichments of the entablature, am shown in Fig. 1, the whole must be set out and so dis- posed and arranged that the centre of each will be in line with each other, or, in other words, that they are regu- larly disposed perpendicularly above each other, as sho^^ni from A to B (Fig. 1) where it will be seen that the centres of the modillion, dentil, egg, and other bed- mould enrichments are all in one perpendicular line. Enrichments set out in this way are said, in phisterers' parlance, to "principle." Nothin;; is more ciinii'ss, eon- fused, and unseemly than to distribute tlicin without any order or principle, as they are in many buildiuf-s. The centre of an egg answers in some places of the cor- nice to- the edge of a dentil, in some to the centre, and in others to the space between, all the rest of the enrich- ments being distributed in the same slovenly artless manner. The larger parts must regulate the smaller. All the enrichments in entablatures are govcrnc;! by the modillions, or mutalcs, and distribution of these must depend on the interval of the columns, and to be so dis- posed that one of them may come directly over the eenti-e of the column, as shown in the present example at C (Fig. 2), the axis of each column. The enrichments must partake of the character of the order they em i«h. When the frieze is enriehod, and the enrichment may be characteristic of the order, or it may serve to indicate the use of the building, the rank, quali- ties, profession, and achievements of the owner. Hav- ing set out the profile and the enrichments, making the running mould and the running mouldings now claims attention. For large work the cornice and the archi- trave are run separately, the cornice being run from the slipper screed made on the frieze and a nib screed, and the architrave from a slipper ^ereed made on the' wall .:^f "ir §\ w m 148 CEMENTS AND CONCRETES and a nib screed made on the frieze. Sections of t?ie cornice and architrave running moulds are shown at Fig. 4. It may be here remarked that the nib and slipper bearings of the cornice and architrave running moulds }ire made for work on ceilings and walls; but if the entablature projects or is independent, and supported by columns, the nib of the cornice mould must be cut so as to bear and run on a nib running rule fixed on the weathering of the cornice, and the slipper of the archi- trave running mould cut so as to bear and run on a running rule fixed on the soffit of the architrave. The frieze, if plain, is set by hand; and if enriched, a bed for the enrichment must be made by running a small part of the bed at the top and bottom of the frieze when running the cornice and architrave mouldings. In this <'ase the screed on the frieze must be set back to allow for the plate or ground of the ornament, and the nibs and slippers of the running moulds extended at these parts. In setting out the mould plates an allowance iimst be made for the bed of the various enrichments, as l>reviously described. The profiles of the three largest enrichments are indi- cated by the dotted lines. The angles of the beds of these enrichments are splayed, as shown, to save fine piaster used for the cast work. This also strengthens the top member of the architrave while it is being run. It will be seen that an in-dentil is used in this cornice, ;is shown by the dotted line at 1 on the elevation. This is the apace between the face or main dentils. The in- Vlentil is run with the mouldings, and the dentils are cast Jiiid planted. The in-dcntil and the dentil may also bt; cast together in short lengths, and then i)lanted. In this case the nmiiing inonld must be cut to form a bed TERMS AND PROCESSES 149 for the combined dentils, as indicated by the dotted lino on the outside of the section of the running mould. Thi' dottwl line on the section of the running mould shows the section of the main dentil. In some examples the external angles of the bed of the dentils are filled in with an ornament fashioned like a cone or pineapple, instead of using an angle dentil. An enlarged view of this cla.ss of ornament fixed in pasition is shown at F'ig. 11. The bed of the small enrichments is made square as shown. When setting out the mould plate, the profile of the soffit of the coi-ona must be taken through the centre of the sunk panel, as shown by the shaded part at Fig. :{, thus forming the raised part of the mould as shown .it Fig. 4. The most intricate part in the construction of a Cor- inthian cornice consists in the formation of the coffers, as shown at Fig. 2. This is a plan of the cornice at an external angle. F is a coffer, and M is a modillion uv "block," as it is commonly called. The coffer consists of a sTink panel, with an enrichment on the four sides, and a rose or patera in the centre ^s shown. A section of the coffer is showai at Fig. 3. The coffers are formed by fixing a "style," as from S to S (including the side enrichments), on the sunk panel, so as to connect the two run plain sides of the soffit and form two sides of the coffer. The lines in the front and back of S and S indicate the joints of the style before they are stopped. Tt will bo understood that the style is fixed before tli.' block is fixed. A plan of the complete style is shown at Fig. 5. When making the model of the style, the sid.' enrichments must be set out mitred and fixed on the plain part of the style, and a perforation made in the centre to act as a key for the fixing stuff used when fixmg the block. A mark must also be made in the cen- ,.: t k 150 CEMENTS AND CONCRETES tre of the front of the style to act as a guide when fixing the styles. The model of the style is moulded in wax, taking care to splay the back and front edges and the centre perforation, also the mitres of the enrichments, to allow the mould to draw in one piece. These parts are trimmed square after the styles are cast. Having fixed two styles, the front and back parts of the coffer enrichments, as shown at Figs. 6 and 7, are fixed; then the patera (Fig. 8) is fixed; and then the joints of the styles are stopped, which completes the coffer. This done, the block (Fig. 9) is fixed, and then the small en- richment (Fig. 10) is fixed, thus completing a part of the soffit of the corona. The other parts are of course made and fixed in a similar way, but the positions of the coffers and blocks must be set out on the whole length of the cornice before the fixing is commenced. Setting out coffers and blocks is a simple matter, yet it requires care to ensure accuracy. First fix a coffer and a block in each mitre, as shown at the external mitre (Fig. 2) ; then from the centres of these blocks set out the whole length of the cornice. This is best done by measuring the full length of the cornice from the mitre blocks, and dividing the total by the combined width of one modillion and a coffer, and if there is no remainder, the combined width is marked on the soffit; but if there are a few inches over, they are divided among the given number of blocks. The marks are proved by going over them, with a compass or a wood gauge. When the exact positions of the centres of each coffer with the block is asceitained, the marks are extended across the corona and down the plain member on which the back end of the block rests on by the aid of a square. These ex- tended marks or lines give the centres for fixing the styles of the coffera and the blocks. Fixins the coffers 'i,::'f TERMS AND PROCESSES 151 ajd the blocks is the next part of the process. This being done, as already described, taking care to use the centi« mark on the coffer as a guide for fixing it fair with the centre lines on the soflBt, and using a wood square to prov^ the square of the style, also using the edge of the square to prove the level of the coffer with the run sides of tJie soffit, then clean off any excess stuff that may exude at the keyhole and edges of the style. After this the back and front side enrichments are fixed, as already mentioned. Before fixing the paterae a keyed or under- cut hole must be cut in the sunk panels to give a key for the stuff that is used for fixing the paterae. A corre- sponding keyed hole must also be formed on the back of the paterae. This is best done by making the desired size of sinking in the model of the paterae before it is moulded. These sinkings must be undercut after the pa- terae are cast. The model of the paterae is generally moulded with a front and back waxed mould. For large paterae, or those having a deep projection a piece of twisted galvanized or copper wire, sufficiently long to enter the keyed holes in the paterae and the soffit, should be inserted in the fixing stuff when fixing the paterae. This method should always be adopted where the bedding surface of the pa- terae is small, so as to enable it to resist the weight of a brush while being painted or gilded. If the paterae are oxlra deep, and project below the line of the soffit, they should be fixed first, otherwise they are liable to get dis- turbed when fixing the blocks and other enrichments. The modillions should be fixed with stiff gauged stuff for the keyed holes in the styles, and the corresponding holes in the blocks (which are made while being cast), and using softer gauged stuff for the bedding surface of the block. After the fixing stuff is laid, place the block ( pfc I rff ' »! ■II 152 CEMENTS AND CONCRETES in position, and work it gently but quickly from right to left, so as to force the excess stuff out, and obtain a true and solid bed, taking care that the centre of the block is linable with the centre mark on the soffit, and usin^r a square to prove the squareness of the block, and then clean off the excess stuff. The small enrichments (Fijrs. 6, 7, and 10) are fixed with soft gauged stuff, so th'it they can be easily and quickly fixed. Small cast work of this kind should always be fixed with soft gauj^ed stuff, as there is very little weight to carry until the stuff is set. The suction alone between the two bodies is often suf- ficient to support Ihe cast until the sUiff is set. These small enrichments are moulded with a face or front wax mould. Modillions or blocks were formerly cast in three parts, namely, the body, the mam part • of the leaf, and the tip or curled end of the leaf; the body being cast in a wax piece mould (some- times a plaster piece mould), and the leaf and its tip in a front and back wax mould, but now the complete block is generally cast in one piece in a gelatine mould. The body of the block may be cast in a gelatine mould, but vhere the back section of the leaf is clear or away from the block near the scroll end, as shown in the accom- panying illustration, and seen in fine old buildings, the leaf should be (last and fixed separately. An enla^jjed view of the plan and side elevation of a modillion is shown in illustration No. 5. The bed moulds and the other small enrichments in the entablature are generally cast in wax moulds. . ^*.M. V4»0»4*#liM^«t»* h umm ModUlion. NO. 6. lit TERMS AND PROCKSSES 153 When fixing the (.nriehments in an entablature, take special care that they all "principle" with each other as already inentionecl, thus forminjr a phrasing and artis- tic finish, which ,s characteristic of well-designed mould. I whlhl ^"^«' ^^'^^''^^ C'a,.«a...-The members nt Plate r".*" " *^' ''''''''' ^^"^^ *° *h^ r>rece.i- as to show the profile and method of setting out more n.: Its 154 CEMENTS AND CONCRETES 'M The combined elevation and profile of the cornice shown at Fig. 1, in the accompanying illustration, No. 6, is an enla^rged view of the cornice of the Corinthian en- tablature. The first upright scale contains four parts of the ten into which the whole entablature is divided, as on the preceding plate. The second scale is divided into five parts, the third of which goes to the modillion, the fourth to the corona, and fifth to the cymatium ; the first and second together are divided into three parts, the first for the reversed cyma at the bottom, the second for the dentils, and the third for the ovolo. The smaller mem- bers are in proportion to the greater, as shown by the smaller divisions on the scale. The modillions are 1-6 of the diameter of the column, and their distances two- sixths and a half. Half a diameter is divided on the corona at Fig. 2 into six parts, of which the width of the modillion is two, and the length of it is four. The cap projects 1-3 of those parts, and the distance between the modillions is 'five. By this rule the exact distance from lentre to centre of the modillions is 7-12 of the diameter. 1'he dotted line A C answers to the diminished part of Ihe column, from whence the cornice is projected; the projection being equal to its height, is divided into four parts, as shown by the scale at the bottom of the cor- nice. One-fourth of this scale is divided into six. parts, :is shown at C, five of which gives the width of the modil- lion. The distance between them is in proportion to it .•!s figured at Fig. 2. The fillets, F F, of the modillion {lie Ys of its width, and so is the bead, B. The position and size of the sunk panel are indicated by the dotted lines in the corona at Figs. 1 and 2, the size being ob- tained as shown by the figures in the dotted spaces. The width of the dentils, D, is obtained by dividing the semi- diameter of the column marked on the corona at Fig, 2 TERMS AND PROCESSES 155 into fourteen parts, two of which gives the width of the dentil, and one the space between them. This space of course is also the width of the in-dentil, the height of which IS one-fourth of the height of the main dentil, as mdicated by the small division on the inner side of the second upright scale. The centres and radius for describing the profiles of the cymatium or cymarecta, the ovolo, and the inverted cyraa or ogee members are indicated by small crosses and dotted lines. Mitring.—Uitring is looked upon by the generality of I^lasterers as a test of speed and ability. As they gener- ally work in pairs on other portions of the work, their in- dividual ability is not easily seen, but when mitring a man carries the operation through alone. Mitring bein<' done by hand, is a near approach to modelling, and is an operation of which a dexterous and good plasterer is nat- urally proud. The quality and time required for mitres j,'reatly depend upon the degree of hardness of the run cornice, also upon the suction. A mitre can be more ireely worked and more expeditiously done on a hard cornice surface, and where there is a suction. The extra absorbing powers of brick walls as compared to lath par- titions cause the gauged stuff to get firm sooner, and enables the mouldings to be more readily blocked out be- fore the stuff is set. A common error when mitrjn" is ^'augmg the stuff stronger than that which has been used tor the running of the cornice, causing extra swelling and difficulty of ruling the members over, and cuttin- the run part of the cornice with the joint rule, especiallv It the stuff sets before the plastc-er has had time to rule all the members over, and then leing stronger, and con- sequently setting quicker, ho b.rs not so much time Xor tormmg the members. Ordiniiry" sized mitres can be 156 CEMENTS AND CONCRETES done with one gauge by using less plaster than in the gauge for running the cornice, and stiffening the greater portion with dry plaster, and using this for roughing out the mitre; then using the soft portion left for brushing over the members and filling up all holes, and afterwards working the joint rule over the metal to take the hu- perfluous stuff off. Should the mitre not be fine enough, the gauged stuff can be further softened on the hawk by adding water, and working it with the gauging trowel, brushing the soft or creamy stuff all over the mitie again, then working the joint rule again. Small mem- bers, and those at the top and bottom of the cornice, where there is most absorption, should be worked by the joint rule first, leaving the large members, drips or coves, or wliere there is a large bi dy of stuff, to be ruled over last. The joint rule should always be worked horizon- tally, especially when dealing with beads »and carvettos. Drips and large members should be worked with the joint rule with an upright motion, because if worked down, the stuff may be pulled down. Mitres should not be worked, fined, or tooled with small tools, as they can and should be brought to a good and straight surfa«-e by the proper use of the joint rule. Small tools should only be used for laying the stuff* when required, and cleaning out the intersections of the mitres, quirks, and for stopping. A square-ended small tool may be used for smoothing flat, straight surfaces. Returned mitres and short breaks are "run down," then cut to the re- quired lengths and planted. They may also be mitred by hand. Mitrc-Mould.— Various attempts have been made to construct a running mould that would form the mitres simultaneously with the cornice running. Most plasterers will have heard of, and some mav ht>ve tried to make TERMS AND PROCESSES 157 and work a raitre-monld to save hand labor. Those who have tried it will Imvo found the results far from satis- faetory. The subjoined illustration, No. 7, shows the method of sottinir (iiit iiud const met ins a mould intendec" -MlTRE-MorLD. N< ). 7. ftir forming the monldinj; and mitres in one operation. The mould is made by fixinjr th" metal plate at an angle of 45 degrees on tht' slipper, oi- in (jtlier words fixnig th(. iron plate at one anelo of a square slipper, whieh allows the mould to run nearly up to the angle, one face of the slipper being used for one side of the wall, and the other m h ll , I! ' . 158 CEMENTS AND COMCRETES face at right angles being used for the other side of the wall. Fig. 1 shows the method of setting out the profile of mould. A is a given section of a moulding, and B is the section of the moulding at the mitre. To obtain this, first draw the moulding A full size, and then extend the ceiling line and draw another wall line. Then from the projection of the top member draw an angle line at 45 degrees. Carry up the projections of the various members to the angle (or mitre line) and then draw hori- zontal lines from the various members; also centre lines of large members as from a to 1 (the vertical letters). Take off the lines a to 1 (diagonal letters) on the angle line, and set them on the ruling line from a to 1 (hori- zontal letters), and then laying them down to the hori- zontal lines, the intersections give the profile for the mitre-mould. Fig. 2 shows a side elevation of the mitre- mould, and Fig. 3 shows a front elevation. It will be seen that the mitre-mould is an expensive and unsatis- factory fad. The time expended in setting out the elon- gated members, making an extra mould, and cleaning out the intersection by hand (as the mould does not leave a finished mitre), also making good the parts broken by drawing out the mould from interlocked or undercut members in the moulding, is not repaid. An average plasterer would put in all the mitres of an ordinary sized room while the mould was being made. The mould will only run into every second angle, and must be taken off and reversed to fit the next. It may seem a waste of time and space to describe and then show the utter use- lessness of a mitre-mould, but having met many plas- terers who stated that they had used or had seen a mitre- mould that worked wonders, I am constrained to give a description, not only to save future futile controversy, (nit to show that in this book the much-debated trade TERMS AND PROCESSES 15i» subject has not been omitted. In concluding this sub- ject, it may be stated that not any one of the mitre-mould plasterers would or could practically explain the modus operandi of this mysterious mould. Fixing Enrichments.—Emichmenta should be fixoil straight, square, plumb, and firm. Cornice enrichments, such as bed moulds, friezes, &c., for which a bed or sink- ing to receive them is formed by the running mould, do not require such strong gauges stuff as soffits, medallions, or other hanging casts. For light enrichments the gauged putty and plaster should never be stronger than that used for the cornice, and clean strong size water should be used. This gives more time for fixing a number of easts, and improves the cementing force, ^he bpd for the cast work should be scratched, dusted, and wetted before the cast work is applied. A snail portion of fim* plaster (the same as used for casting the enriehnients) should be gauged with clean size water, to be used for the joints. The gauged fixing stuff should be spread evenly over the back of the cast and over the scratched bed of the moulding. No more should be laid on than will fully fill up the scratches. Then place a small piece of the white or joint gauge on the point, and press the cast into position by gently but quickly sliding the cast twice or thrice backwards and forwards to expel the air and incorporate the two bodies. It is a mistake to dab a lump of gauged stuff at randon» on the back of the cast and press it on the bed, as the stuff does not properly enter the scratched part of the bed, and the contained air prevents proper cohesion and solidity. When too thick a coat of stuff is laid on the coat, straight and evt-n fixing is more difficult. The excess stuff oozes out at the sides, and unless time and care be taken in cleaning it off. the moulding, or east, or both, get damaged. A lull w. leo CKMKNT8 AND CON'CRETES Minail pt>i-tion nuiy uIhd oozr out in the Hrat method, but it will be »o thin that it can bt* brushed off while soft. When fixing niedallion blockn or truHMes, a dovetailfd hole 8hould be cMit in the vertical and horizontal partn oC the bed, and similar holes in the bloeks (which are made when being east) are filled in with uau^ed stuff and applied in |M)sition. If the cast should be very heavy, or of Portland cement, it is further secured by insj'rtinjf II slate or iron dowel while the stuff is soft, allowing: a jKirtion of th<' dowel to project to enter into the l)ody of the cast. Heavy easts should be temporarily supported by wood props until the fixing stuff is .set. When fix- inj? heavy ca.sts the plain surface of the pla.ster work should be flit as lar as the lath to obtain a better and stronger key. The putty in the fixing stuff should be mixed with long strong hair or tow, as described for rib mouldings or ceilings. Hair or tow may also be used advantageously in fixing Portland or other cement work. ( 'ast work, when extremely heavy, .shoiUd be further se- cured by means of long screws or bolts, placed so as to pas.H through the cast work and into the timber, the easts being bedded with gauged haired stuff and tem- jwrarily propped up. The screws or bolt« should be fixed before the stuff is set to avoid the probable dis- turbance of the gauged bedding. Before fixing any "cast work they should be placed in position to prove their correct fitting. Centre, side and end lines should be made on the surface of the bed to give a guide for fix- ing. It may be neces.sary to fix nails at intervals in the lines to give a further guide. Mitring Enrichmrufs. — Before fixing contintious or space cast work, the length and widtli of the panel or room should be set out to prove that the mitres aie (>quai- sided. balanced jukI have flowing lines. Nothing Iook.9 TKKMS AND PHOCKSSKS 161 H.. ilovf • nnwiirkmanlikt' an a mitre in an ornament lilt hapn«./nrd, with tln' IfadiUR «tem disjointi'd or sprintfinjf out of u tlowiM- or tt'ni' the plaster, which makes the work more difficult to do when floating, setting, running mouldings, or mitring. A quart and a pint measure should always be kept (>») the scaffold for measuring the water used for the vari- ous gauges. The quantity of water will regulate i)»* quantity of plaster for each gauge. A proper plaster TERMS AND PROCESSES 169 box should also be on the scaffold, made to hold a sack of l)laster, and having a lid made in two halves hinged from the centre. This prevents the plaster from getting dirty by falling stuff, and from getting damp by absorption from the atmosphere. Where there is a large quantity or continuous gauging, the box should be placed on h stand (this is called a stand-box) to prevent unnecessary exertion and loss of time by stooping for each hr ndful. When gauging coarse stuff for large surfaces which require several gauges to complete the work in hand, size water should be used in proper proportions with the neat water used for gauging, so as to allow sufficient time to properly manipulate the material. In the event of gauged stuff setting before the work is laid and ruled off, it is difficult to make the surface strong and fair. This also allows the various gauges to be laid on or against the previous ones while they are in a soft state, thus forming stronger joints and better eolu'sion between the various gauges. The use of size water in gauged set- ting stuff' and putty enables the wt)rk to be freely trow- elled and finished. Gauged stuff .should not be hand- floated, as excessive working destroys tl>e settin.; powers of the plaster. Joist Lines on Ceilitigs.—Comuum flat ceilings show in time the precise position of the joi.sts above, and in many instances the position and form of the lath work can be easily discerned. JVIany theories have been ad- vanced as to the cause of these unsightly lines or marks, which are so distressing to the mind and eye. In my opinion they are due in a great measure to insufficient material and inferior work. The plaster which is be- tween or separate from the joists is more pervious to the atmosphere than that which is in more direct contact. The air in passing through leaves behind it particles of 170 CEMENTS AND CONCRETES s dirt assigned in larger measure to the unattached than to the attached portions. Dust that finds ingress be- twt«n the joints of flooring boards lies on the unattached portions, consequently the joists show themselves as lighter lines on a more or less dirty background. The same causes apply to the lines on the lath work. An- other cause is that the plaster work is too thin. In many instances the floating is brought up from the lath in one coat This is a most pernicious habit, as it is not only the cause of lath lines, but the ceiling invariably cracks, and develops spontaneously original patterns indicative of rivers, which too often lead like Niagara to a catas- ti-ophe in the form of falling plaster. Joists and lath lines on thin ceilings may be partly obviated by laying strong brown paper over the upper side of the lath and plaster and then pasting the edges to the sides of the joists, so as to form a cover to the plaster work. The better and most sanitarj' way is to lay the work in three coats, allow the first coat to dry, consolidate the floating coat by well scouring with a hand float, and render the setting coat hard, non-absiirbent, and impervious to the air by thorough scouriuff, trowelling, and brushing. Rough Casting. Several years ago I was requested by the Editor of "Architecture and Building" of New York to prepare a short treatise on the subject of "Rough Casting" for publication in that magazine. The article was pub- lished in almost every architectural journal in the coun- try, and Mr. Kidder embodied it in his excellent work, "Building Construction and Superintendence, Vol. I." I reproduce it here, as the directions given therein have been found to be of the very best, and most workmen in 11 TEllMS AND PROCESSES 171 this line of the trade adopt the methods of manipulation herein described. "Rough casting, or, as it is sometimes called, slap dashing, both of which are synonymous with the French hourdage, rough work, and ravalement, having a similar meaning, is a method of plastering the outside of a build- ing much used in the northern part of Canada because of its being durable, cheap and well adapted to keep out cold winds during the long winters in that section of the world. The methods of applying rough ca«t and the mixing thereof do not materially differ from the meth- ods adopted in Northern Europe or even in the North- western States, but it is these minor differences, says a writer in an exchange, that make the Canadian rough casting superior, so far as durability is concerned, to much that is done in other parts of the world. There are frame cottages near the City of Toronto and along the northern shores of Lake Ontario that were plastered and roughcasted exteriorly over 40 years ago, and the mortar today is as good and sound as when first put on, and it looks as though it was good for many years yet if the timbers of the building it preserves re- main good. Rough cast buildings are plentiful in every province in the Dominion from Halifax to Vancouver and from Lake Erie to Hudson Bay, and when well built and the rough cast properly mixed and properly applied the result is always sat i.s factory. It is quite a common occurrence in Manitoba and the Northwest Territories in the winter to fiind the mercury frozen, yet this inten- sity of frost does not seem to affect the rough casting in the least, though it will chip bricks, contract and expand timber, and render stone as brittle as glass in manv cases, and the effect on iron and steel is such as may 172 CEMENTS AND CONCRETES pruve diuit^erous if exposed t<- suddeu aud unexpeuted strain. in preparing a frame or log building for rough cast- ing eare must be taken in putting down the fouiula- tion. A good stone or brick foundation is, of course, tlu- best, but where rou^'h casting is intended stone or biitk foundations are seldom ustnl because of their cost, and the builder is compelled to use posts of wood. Tlu' posts are generally made of white cedar, which has ji lasting quality of 35 or 40 years if sound when usid. The posts are put in the ground from 3 to 5 feet, the deeper the better, as they should be deep enough in any case to prevent frost from forcing thcMu upward. Whcu a sufiicient number of posts havf been properly placed a line is struck on them a proper height from the ground and the tops levelleti off. The sills are then placed — all joints being broken on top of posts — and the whole made level. These sills and all the other timber, scantlings and lumber should be well seasoned, if possible, for the greatest enemy to the plasterer is unseasoned timber; shrinkage of joists, posts and scantlmg not only breaks the bond of the mortar, but causes great cracks in coi- ners and angles that no amount of pointing or patching can ever niaki' good. When the frame is up and the rafter on and well se- cured the whole of the outside should be covered wilh good, sound, common inch stock pine, hemlock, spruce, or other suitable lumber, dn^s.sed to a thickness. If j)iit on diagonally .so much the better. t)ut this is not abso- lutely necessary if the rough easting is to be of the best ouality. as will appear hereafter. When it can be done it is best to get all partitions .set in place and lathed, the roof on and all necessary out- side finish or grounds put in place and made ready to TERMS AXU I'KOCESSES 173 receive the lath. The carpenter must prepare hin finish or grounds for finish to acctuninodate the extra lath, aa the walls will bo thiekcned accordingly. For the cheaper sort of rou},'h casting in otic or two • oats the following incthixl vi lathing i^ cnii)l.;j,ed: Nail laths on the boarding — over paper or felt, if paper or felt is used— perpciidii'ularly l(i inches from centre to ci-ntre if 4 foot laths are used, or IH inches or 1 foot from center to center if .i f»x)t laths are used. The whole surface to be rough cast will mpiire lathing this way. When done lath as is ordinurily done with No, 1 pine lath, breaking joints every 15 inches. Put 5 nails in each lath, driving each nail home .solid, coat over with UKH-tar, well haired, and that has been njade four or more days; 8ni(M>th and straighten as well as possible with a (laiby. When done and while yet soft the rough cast is thrown on it with six-h force as to drive the pebbles or small stones deep into it. The mixture or dash, as it is railed, is compcsed of fine gravel, clean washed fronj all «'arthy partick>s and mixed with pure lime and water till the whole is of a semi-fluid consistency. This is mixed in a shallow tub or pail and is thrown upon the plastered wall with a wooden float >about o or 6 inches long and as many wide, made of \<. inch pine, and fitted with a wooden handle. While with this tool the plaster- er throws on the rough cl ,t with his right ha ml, he holds m his left a common white-wash brush, which he dips into the rough ca.st and then brushes over the mortar and rough cast, wl ich fiives them, when finished, a reg- ular, uniform coL.r and appearance. For this sort of work the following proportions will answer: To one barrel of prepnn'd gravel uko a quarter of a barrel of putty; mix well before using. This may be colored to suit the taste by using the proper materials, 174 CEMENTS AND CONCRETES :.i; aa given further on. It nnwt be understood that the fore- going is the cheapest sort of rough casting, and is not reeommendt'd where more durable but more expensive work in required. The best niude of doing this work aa practised in the Lake district of Ontario is nearly as follows. Have the frame of building prepared as indicated in the foregoing, with partitions all put in and well braced throughout and well secured. Lath diagonally with No. 1 pine lath, keeping IV2 inches space between the lath. Nail each lath with 5 nails, and break joints every eighteen inches. Over this lath again diagonally in the opposite direction, keeping the same space between the lath and breaking joints as before. Careful and solid nailing is required for this layer of lathing as the permanency of the work depends to some extent on this portion of it being honest- ly done. The mortar used for the first coat should have a goodly supply of cow's hair mixed in with it, and should be made at least four days before using. The operator must see to it that the mortar be well pressed into the key or interstices of the lathing to make it hold good. The face of the work must be well sciatched to form a key for the second coat, which must not be put on before the first or scratch coat is dry. The mortar for the second coat is made in the same way as that re- quired for the first coat, and is applied in a similar man- ner, with the exception that the scratch coat must be well damped before the second coat is put on in order to keep the second coat moist and soft until the dash or rough cast is thrown in. The rough casting is done ex- actly in the same manner as described for the cheaper sort of rough cast work. A building finished in this manner, if the work is well done, possesses many advantages over the ordinary TERMS AND PROCESSES 175 fi wood covered structure. It is much wanner being al- most air tight so far as the walU> .e concerned. It is safer, as fire will not eat its way through work of that kind for a long time, it is cleantT, as it will not prove such a harbor for insects. It may be made as handsome as desired, for before the rough cast is dashed it may bo l»»id off in panels of any shape by having strips of bat- ten? * ;cked over the soft mortar, which may be removed an I' • )Ugh casting is done and the coloring finished. It s n .(■'(: mperior to the so-called brick veneered house, as :t ;s w - ler, more exempt from fire and cheaper. >'>•• r yards of rough casting in the manner •Icnorih^d the following quantities will be required: 1800 LirJiK 12 bushels of lime, V/^ barrels of best cow hair, !»'. lis of sand, % yard of prepared gravel and 16 ounds of hot cut lath nails, V/^ inches long. The gravel should be sifted through a Yo inch mesh screen, and should be washed before mixing with the lime putty. To color 100 yards in any of the tints named herewith use the following quantities of ingredients : For a blue black mix 5 pounds of lamp black in the dash. For a buff use 5 pounds of green copperas, to which add 1 pound of fresh cow manure ; strain all and mix well with the dash. A fine terra cotta is madj; by using 15 pounds of metallic oxide mixed with 5 pounds of green copperas. A dark green color is made by using 5 pounds of green copperas and -^ pounds of lamp black. Many tints of these colors m > be obtained by varying the quantities given. The coicrs obtained by these methods are perma- nent; they do not fade or change with time or atmos- pheric variations. Many other colors are used but few stand like the ones named. A brick color may be obtained by the use of Venetian red and umber mixed in whisky first and then poured into the dash until the proper tint IF^ ■• E r- r :n , fil " ^ #1 ■m ■■■.flail t. (1i .1] V 176 CEMENTS AND CONCRETES is obtained. In tinio, however, like all earthy pig- ments, these coloi's fade and have a sickly appearance: tliey answer better in eements than when incorporated With fat limes. VARIOUS SIETIIODS OP RUNNING CORNICES. CIRCLES, ELLIPSES AND OTHER ORNAMEN- TAL STUCCO WORK. Diminished Columns. — The diminishing of cohimns is an interestiof? but sotnewhat difficult operation. Great care must be exercised not to overdo tlie entasis or swell- in}:. The swell may commence veiy jfradually from the base to the capital], or the third part of the column may be of the same diameter, and then swell and diminish for the remainder of its heijjht. Two methotis are here fjiven to show how this may be done. Tliise are jriven more to illustrate the metlKKl of setting.' out the dimini.shcd floating rules — so ne(M's.sin-y to the j)la.ster«'r — than to define the SH-ell or diminishinj: of a coluiim, which, being within limits a matter of ta.ste, pertains more correctly to the architect. The best instrunipnt for forming a diminished column (plain or fluted) is a diminished thwitiiig rnlc. with a cutting edge made to the contoui- of the proi)oscd col- umn. This rule is us«h1 Uj dctcnuint' tiic central posi- tion of the astragal and has*' mouldings (which act as bearings when ruling olf the tlojiting stiitV and the final <'««it), so as to (►btain a true and uniform diminish, and also to form a fair surfact\ The appended illustration No. 9 elucidates the method of setting out dimini.shed columns which is also used for setting out the diminished rule for both columns. The method for setting out a diminished rule for a coliunn that dimini.shes two thirds of its height is as follows : The dimensions of the column 177 178 CEMENTS AND CONCEETES n i| f^ METHODS OP WORK 179 having been fixed, i. e., the height of the shaft and its upper and lower diameters, draw a perpendicular line which may be taken as the centre line of the column; then set out the upper and lower diameters, as shown in Fig. la. This figure also shows one-half of the con- structural brick work, and the plaster, which is dis- tinguished by being dark shaded with the floating rule in position. A floating rule for forming the curved and diminished surface requires an iron plate, similar to a mould plate, as shown, so that it will cut the stuff off cleaner and truer, and last longer. The other half of the elevation shows the lines and divisiwis for obtaining and setting out the entasis. To diminish the column, first divide the height into three equal parts then at the lower third (5) draw a semicircle equal to the lower diameter of the column. Next divide the upper portion of the column into four equal parts, as shown at 1, 2, 3 and 4, then draw a line, parallel with the axis or centre line of the column, from figure I at the top of the column, cutting the semicircle at 1, divide the remainder of the semicircle into four fqual parts, which gives the diminishing points. From these point« draw lines parallel to the axis of tlie column, and from the corresponding figures, or from 2 to 2, and w on. In these intersecting points fix pins or nails, and bend a flexible strip of wood or metal round the nails, and draw the curved line. The whole line from top Ut bottom is then transferred on to the board that is to be M.s<'d for making the floating rule. This column will have Its greatest diameter for one-third of its height, and the Ripper portion its entasis. This method is so far defect- ive as to require the curve to be drawn by hand, a de- feot, however, obviattnl by using a column trammel, »hieh is used for a column that diminishes with a grace- ;;d ;r i, J 80 CEMENTS AND CONCRETES fill curve from the base to top of the shaft. This trammel isi made as follows: Column Trammel. — A eolumn trammel is simple in construction, and when carefully used gives very satis- factory results, forming a graceful diminished curve from the lower diameter to the upper diameter of tin- shaft. Befor«' describing the methwl of setting out and constructing the column trammel, the method of finding the point D on Fig. 2 is given on » separate sketch (Fig. 5) to show the metlunl more clearly. Fig. 5 illustrates the method of obtaining the point D, on which the centre ]>in is fixed for the trammel to slide on while working. This point also gives the length of the radius-rod. This sketch is reduced one-half in si/e to that of Fig. 2}i. but the letters correspond to it. Having set out the axis or centiv line of the column (A li) iiiid the base line (A C) (extending the latter indefi- nitely) as described for Fig. la. proceed as follows. From A as a centre, and fn)m A to B as a radius, describe an nre. as iiulieated by the dotted line; then from the in- tei-secting point at V, as a centre, and fnmi C to the l»oint at B as ji radius (as inr a clean floor. To si't it out, first draw a line to the exact height of the propos<'r block to work smoothly. It iiiso allows a ffreater space for a thicker boartl for the Moatiny: i-nle. Fiir. 2 shows erdarf.'etl details of the <;roove rules (A, A.) the jrroove (b,) the slidinj? block (H). with the pin ill), the radin.s.ix)d (F), with the pencil ((}), and the hoard for the floatinj; rule i('), with the diminished line. FifT. 1 .shows a secti(«i of Fijr. 2. The letters in all fi}.'ures correspornl with each other. Fif;. 2a shows the whole column with the tnunmel and fini.shed Hoatintr rule (C). Make the radiu.s-nxl about '2 inches wide, 1 inch thick and in lenjrth a little lon-rer than the distance from D to B, and the half diameter of bjwe of the shaft. The .sliding block (I!) is about 4 inches Ion}; and equal in depth and width to that of the sliding' {groove (b). It should be made smooth, and fit the een content to work them by theorx , forj.'ettinfr that an ounce of practice Is worth a ton of theoiy. Some men thoufiht they had accomplished a feat when they had run a sinple flute with a hinired mould, between two run- ninp ndes fi.x"d to form diminution in width, forpetr 186 CEMENTS AND CONCRETES i '• 1 ( , tiDK ur not knuwint; that fluteti diminiih in depth a& well as width. The diti rctioe in depth of flutes, at the bane and the top of the sauft, is shown at A, the base, and B, the top, in Fig. 1, ilUihtratioD No. 10. Running moulds have also been made with springs to regulate the diminish in depth, but their art ion was uncertain, and they are also too expt'tisive for the purpose. Another form of run- ning; mould was made by fixing wire, catgut, or leather on one end of one of the slippers, and on the upper edge of the st(K>k, so that the slipper, when being forced up the diminished space between the running rules, became more an^'ular, or in other words, the slipper on which one end of the wire was attached was higher up the diminished space than the other slipper, and thus caused the 8to<'k to cant forward, or be drawn out of an up- right, and reduce the depth of the flute. The stock in this case is connected to the slippers not by hinges, but by a pivot inserted at each slipper to allow the stock to cant forward when pulled by the wire. This form of mould also proved to be too erratic in its working to be of useful service. Running moulds having the .stock connected to a slipper at each side by means of two hinges (termed a double-hinged mould) allow the uioidd to a.ssume an angular or slanting form as it passes^ up the diminished space, thus forming a diminution in the width of flute, but it does not form it with a true arc all the way. On the contrary, it assumes an elliptical form which becomes more and more pronounced as it ivaches the top of the shaft. The nearest approach to perfection in running dimin- ished flute is performed by means of a running mould nijide with hinged slippers as described, but having the mould plate and stock cut through the centre of the i! METHODS OF WORK 187 prufile, the two ptaU beinp then connected by a hinge. Thin form of running mould (termed a "triple-hinged mould") allowa the mould to collapse in the form of a V on plan, and the slippers to run level or parallel with fach other, thus forming each half of the flute alike, and at right angles from the centre. Still this has the defect of forming the flute without the necessary decrease in depth. A method for diminishing the depth of the flutes is to make the running rules with a diminish on face, or rather to make them with an increasing thickness towards the top ends, so that the mould when running up on the increasing thickness will form a corresponding de- eri'ased depth of flute. When running a fluted column by this process, the running rules are flxed flush with the faee line of the fillets. Only one flute can be run at a time, but twelve may be in band at the same time. As there are generally twenty-four flutes in a column, twelve rules would be rwiuired to keep a couple of plasterers going. When the ft»^t set of fluti-s are run, the rules are taken off and fixed to run the remaining flutes. When all are run, the returned ends at top and Iwttom require to be made >rootl. It will be seen that the running rules for this method must be carefully made and fixed to ensure true lines and forms. It will be nnderstcKxl that a bed or urouut] nuist first be formed as a puide for setting out and fixing the nuinin^' rub's on. This is done with the aid of a diminished lloating ml<'. It will also be self-evident ♦hat the floatinjr rule would be more profitably employed for fonning the •■ntire shaft with the flui.«, thus dispensiut? with run- iiinjf rules and hinged moulds. This method of running' the flutes is slow and tedious, but the worst part is that tile flutes are not true seirrniMitH ; in fact, the wliole of the \ 4\ ii^ MICROCOTY RESOIUTION TEST CHART (ANSI ond ISO TEST CHART No. 2) I.I 1^ ■ 50 l;. 2.8 \^ 1*0 2.5 2.2 2.0 1.8 ^ APPLIED IfW^GE Inc S"- '653 East Mam Street I^S Rochester. Ne* York 14609 USA ^S ("6) 482 - 0300 - Phone S (''6) 288 - 5989 - Fax 186 CEMENTS AND CONCRETES •ti ■ II n III 4'^ ^l! 1.' -ii " methods mentioned are more or less a rule of thumb, un- certain and inaccurate. A knovvledffe of the rudiments of },'eometry will prove that the true form of a diminisht^ and swelled fluted column cannot be run with a mould, however ingeniously made. This may be proved by cutting a plaster or card- board disc to the former radius of a single flute, and de- scribing a line round it on a board. This would be the form the mould, when at right angles at the bottom of the shaft, would give the flute. Then place the disc in an oblique position (the same as the hinged mould would be at the top), and project the plans by means of a set square on to the board. It will be seen that the mould Avould give the flute an elliptical form. It may be further explained by stating that when the mould is square at the base, or at right angles with the vertical running rules, the form of the flute would be a true segment; but when the mould is moved up the dimin- ished space between the rules, it assumes an oblique or slanting position. It gives the flute an elliptical form, which increases and becomes more pronounced as it ap- proaches the necking. It may be said that the pointed or elliptical defects can be filled in and worked fair with circular hand floats, but this plan necessitates a series of hand floats to fit the ever-varying widths ; d depths of ^he flutes. It may seem unnecessary to describe the above meth- ods, and then to point out their defects. However, the methiwls and defects are given to prevent the rising plas- terer falling into the same errors, and to enable him t«> resist and rebut the arguments that are so often ad- vanced by sonic men. who persistently a.ssert that their own ])ailieiilar way (geuer^riy oii<* of the methods al- ,v METHODS OF WORK 189 ready mentioned) is the correct and only way of proper- ly performinfi this different but interesting operation. It is worthy of note, to show the interest taken iu this subject that a patent was obtained for a running mould and pri>cess for forming diminished fluted col- umns, in 1878, whica obtained a provisional protection for "improvements in moulds or templates for running stucco or cement tapered fluted columns." The follow- ing is a copy of the specification in extenso: — This invention relates to the running of stucco or ce- ment in forming fluted or other columns, pillai-s, or pi- lasters, and similar surfaces, in a more simple, economi- cal, and expeditious manner than heretofore; and the nature and novelty of the invention as applied for run< ning or making the body part of a fluted tapeied col- umn of stucco or cement, consisting in constructing a short box-shaped temi)late, having two sides joined to- gether by a back plate outside, with a handle upon it, for drawing it up and down the column, and with an open space inside the back between the sides open above Jind below, equal to any desired section or segment of the column at its base or widest part, into which the column is equally divided by narrow longitudinal strips of wood, against which the inner edge and end surfaces of the sides of the template slide close, so as to luevent the escape of the semi-liquid or stucco. A thin elastic segmental mould plate is hinged or jointed at its ends to the inner faces or edges of the template, formed ill its inner scraping edge to correspond to the segmental curve of the base of the column, with rounded pro- jections corresponding to the flutes to be formed on the column. This plate and its hinges are laid at an angle highest at the inner scrapiiig edge, and inclined down- wards towards the back, leaving a space between it and ■1 " ■! ' 1' H •,lhi.. 190 CEMENTS AND CONCRETES ' : i '■•"•II: m !!• III M ,1^1 the back for the free passage or escape of the super- fluous stucco or cement scraped off the column during the ascent of the mould along the column on its longi- tudinal shaping strips before mentioned, "The one end or side of the mould is made to slide or contract laterally in slots or other equivalent guides in the back of the mould frame as it ascends along the con- tracting or tapering longitudinal laths, the thin plate bending or yielding down in a curvilinear form on its end hinges before mentioned, so as to bulge inwards while bending downwards^ and so contract the column in a nearly true radical and segmental form from the bottom to the top of the column, the angle at which the scrap- ing mould plate is set on its hinges determining this con- traction of the scraping centre edge of its segment radi- cally in a ratio corresponding to the contraction of the lengths of the segment and moving sides of the mould, which, for large moulds and columns, might be car- ried and drawn up by handles secured to the tops of the ends of the moulds with ropes led up and over pul- leys at the top of the column, thence down to the hand of the operators, so that the mould may be raised and lowered at pleasure to form the whole segment of the column from the bottom to the top in nearly as simple and efficient a manner as plain mouldings are at present run by the usual simple edge scraping moulds, one seg- ment being run after the other in succession until the column is finished. "For plain or other forms of columns the inner scrap- ing edge of the mould plate is made to correspond to the tapered surface of the column to be formed plain, seg- mental, or fluted as desired ; and for flat, square, or polyg- onal columns, which do not require a segmental mould scraper, this would be made straight, either plain or METHODS OF WORK 191 fluted, as desired on its scraping edge, and set horizontal- ly on its hinges, instead of at an angle as described for the segmental mould scraper for forming round col- urans; and this mould scraping plate in any case is pre- ferred to be made of thin elastic steel or tempered cop- per or brass, which would bend and contract the flutes or ridges on the surface of the columns or pillars, equally and proportionally to the several parts of the column over which the mould is traversed. Although the mould or template has been described as made with only one of its ends movable laterally, it is to be understood that both ends or sides may be fitted so as to move in a similar manner to suit different kinds of work This patent method would be better understood if it had been illustrated. No provision for diminishing the depth of the flutes is given in this method. The use of flexible metal for diminishing purposes cannot be relied on for accurate work. Another method for forming diminished fluted col- umns is thus performed:— Make a single flute in plaster, and use it as a mould for casting reverse flutes composed of fibrous plaster. After casting as many reveree flutes as there are flutes in the proposed column, indurate them with litharge oil or paraffin wax. Casts of the necking and base, eax;h with about 3 inches of the fluted shaft, are fixed on the brick core. The shaft is then laid with Portland cement (or other desired cement) and sand un- til within abor-t one-third of the line of fillets, and while this stuff is still soft, take a reverse ' flute (previously oiled) and press it into position, using the cement flutes at the necking and base as guides for fix- ing, and using a diminished floating rule to prove the outline. Repeat this process until all the flutes in the column are filled with reverse flutes. The intervenins 192 CEMENTS AND CONCRETES • «!!; I'l'i fl^il ! : tj::: - 2 It : n spui-es or fillets are then filled in with gauged cement until flush with the outer surface of the reverse flutes, and further regulated with the floating rule. "When the stuff is set, the reverse flutes are extracted, and any de- fects in the flutes made good. On the care in fixing the reverse flutes and filling in the fillets depends the success of this method. Diminished fluted columns are also made by cfusting two vertical halves, and then fixing them on the brick core. The halves are fixed by means of cement dots, which are laid on the core at intervals. iCorresponding dots are laid on the interior of the casts. The casts are then pressed on the core until the dots meet, and both halves are in proper position. The cast work is made solid with the core by pouring a thin and weak solution of cement and sand into an orifice at the neck- ing. The cement and sand .should be mixed in the propor- tion of one of the former to five of the latter. This gauge has sufficient binding power and strength for this purpose, and is not liable to expand or contract in wet or dry weather. This process is useful for small work, and makes a good .job wiien cleanly cast and neatly fixed. The necking with the capital and the base may be fixed be- fore or after the shaft casts are fixed, according to eir- cumslances. The shaft casts are best formed in a reverse casting mould. Another method of casting a diminished fluted col- unui is effected by making a reverse casting numld. Fix it round the core, and pour th«' gauged material in at the top of the necking mmihi. ]>y using a reverse casting mould made with a j>laster face and a wood back- ing. (»r a niiMiid made in filn'ons plaster, llie whole column with the core can be made in one piece. IJol- METHODS OF WORK 193 low columns, composed of Portland cement concrete, can be made to carry any weight supported by a stone column, or one constructed with a brick core of equal diameter. Cast hollow columns are made by temporarily fixing a wood or fibrous plaster core tapered to one end to allow it to be withdrawn when the concrete is set. A rough wooden or a fibrous plaster hollow core is used when casting a hollow column in situ. The core in this case is left m. After many years' experience and observation on this subject, I am of opinion that the true form of a dimin- ished fluted column (composed in Portland or similar cement, and constructed in situ) is best obtained by hand, with the aid of cement rims or plaster collars and a diminished floating rule. Most plasterers will admit that what can be and is done in stone or wood, can be done equally well in cement or plaster. A plaster- er has one advantage, inasmuch as he can add as well as subtract when forming circular surfaces, whereas the mason can only subtract. The two methods hereafter given for forming diminished fluted columns by hand are simple, speedy, and accurate. They are on' one prin- cipal, and each may be used as circumstances require: one is termed the "rim method," and the other the "collar method." Forming Diminished Fluted Colutrv by the Rim Method. — First make models of the half circumferences of the astragal or necking and base mouldings, each having about 4 inches of the fluted shaft, as shown at Fig. 1, the plan and Fig. 2, the elevation, on illustra- tion No. 10. To make the models, cut a mould p^ate to fit each of the full-sized mouldings, and the required sue of the shaft, and "horse" them with radius-rods, &iiCi ruu a little over one-half of each circumference in ';J I • -. ■is;! a: I .. 200 CEMENTS AND CONCRETES Havmg now briefly reviewed the more or less useful methods^, and described some of the most useful and practical methods, the conclusion to be drawn is, that diminished fluted columns are best dv>ne by working them by hand, with the aid of diminished floating rules and cast Oi* run beax'ings. This first or rim method will be found useful for many purposes; but the collar meth- od, with the addition of intermediate collars for extra high columws, is the best for general use. Diminish /d Fluted Pilasters. — Pilasters are said to be a Roman idvention. They bear an analogy to columns in their parts, have the same names and stardard of measuremt'Uts, and are diminished and fluted on the same principals When pilasters are placed behind coliunns, and very Lear them, they should not project above one- eighth of vheir diameter; but if they are from 6 to 10 feet behind the column, as in large porticoes and per- istyles, they should project at least one-sixth of their diameter. When they are in a line with colun^ns, their projectioti should be regulated by that of the columns. When pilasters are used alone as principals in composi- tion, they should be made to project one- fourth of their diameter to give regularity to the returned parts of the capitals. The process for forming pilasters is the same as for coI>imns. Panelled Coves. — ^Large coves, segmental or elliptical on section, having their surfaces panelled with mouldings which spring from the back or above a wall or main cornice, nnd finish at or intersect with a beam or other moulding at the top or crown of the cove, require to be carefully set out and screeded. The floating is done from two horizontal screeds made at the top and bottom of the eovc«, and from these vertical screeds are formed, nnd Ui<'n the intermediate spaces or bavs are fill(>rf I 1 11 Ski ll Hi <•] ;;; »!' » », 202 CEMENTS AND CONCRETES running the main cornice. To float this cove for the run- ning? of vortical mouldings, first form the top and bottom horizontal screeds (A and B), then form the pressed screed. This is effected by temporarily fixing the template, G, or by one man holding it on the bottom screed, and another man holding it on the top .screed, while a third spreads and presses the gauged coarse stuff nntil the space between the first coating and edgx? of the template is filled up, then drawing the trowel do\vn each side of the template clears oft' any superfluous stuff. -Fig. I. Floating Coves. Fig. 2. Levelling Rulb. NO. 14. 11 it;- ' : The template, wliicli has been previously oiled, is then removed, leaving a narmw, l)ut true and smooth screed ready for working on. This method gives a truer screed, especially in elliptical or long circular screeds, than floating or working with a template, because if the t^nnplate is not worked perfectly vertical, the curve of the screed is altered and not true. The subjoined illustration (No. 14) elucidates the meth; d of forming the sf^reeds for floating cove surfaces, also for floating segmental, "Uiptieal. or any other form METHODS OF WORK 203 01 toterior and exterior aiip:Ies in coves. Fig. 1 shows a plan of the cove. The letters in this sketch correspond with those on the same parts in the section on illustration \o. 13. The first eoatin*.' and the various bays, after the screeds are made, are indicated b}- crossed diagonaJ lines at the D's. The top screed. A, should be levelled from end to end and made parallel in depth with the ci-own moulding. Their levelness is tested with the aid o? a "levelling" rule. The bottom screed, B, should he made parallel with the main cornice, so that the pro- jection of the vertical mouldings will be uniform. The vertical screeds, C, are next formed, making the first two Jiear the internal angles, then two at the external angles. 'I'ho inten,'ening space is now set out, so that the screeds may be 8 to 10 feet apart. The screeds may 1k> formed farther apart according to requirements. If there are vertical mouldings to })e run in the cove, the screeds sliould be made at the sides of the proposed mouldings. It is always best to have two or three screeds near the angles, so as to give a bearing for the floating rule, R. This shows the position v)f the rule when floating the in- lernal angle. The external angles on the other side are formed in the same way. The distance betwetm the screeds used for floating the juigles can be regulated ac- cording to the depth or form of the angle. It will be understood that the floating rule nuist be sufficiently long to bear on two vertical screeds, and reach to the extreme point of the angle. The floating rule. R, here shown is termed a grooved floating i-ule. This is grooved on both sides, as sho\3:ji by the section, S. Pig. 2 shows the elevation of a levelling rule as used for levelling dots for ceiling, beam, or crown screeds. This is similar to an ordinary parallel rule, but with the addition of a fillet, F, nailed flush with the bott..m edge 'urn If '. Ill I h "i ■ lU "I IN"' ii;!!!! ■ f* ■Ml I -I":! i;;i| Mil « i: I'fil 204 CEiMExNTS AND CONCRETES to form a ledge to carry the spirit level, L. The level- ling rule is applied on the dots to test if they are level; this is proved by inspecting the spirit-level ; if one dot is too full it must be depressed until the levelling rule is level. Diminished Mouldings.— Mouldings that diminish in depth or projection as well as in width (termed "double diminished moulding:s") are not so common as those that diminish in width only. The diminish in width is simple, and is obtained by the aid of a "triple-slippered" run- ning mould and two running rules fixed to form a diminished space, as described hereafter. The formation of a regular and pleasing diminish in depth greatly de- pends on the profile of the moulding. A moulding hav- ing small members, especially at the sides, is more diffi- cult to diminish than one having large members, es- pecially one with plain and deep fillets at the sides. Three methods are here given for running double dimin- ishod moulding!* on domes, cupolas, or vaulted ceilings, or on lower surfaces. These methods give good results, especially if a little thought for the requirements of the case is bestowed on the designing of the moulding. Double Diminished Moiddings, False Screed Method — By this method the diminish in depth is obtained by false screeds, and the diminish in width by the aid of a dimin- i-'V ^ '•ule, which is fixed on the centre of the profile or bfc^ .. enrichment. This method is elucidated in the fol- lowing illustrations. The annexed illustration No. 15, shows the section of a vertical moulding on the plaster or floated surface of the inside of a dome. C is the main cornice from which the inner line of the dome springs. The D's are dots which are used to regulate the-diminish of the false screeds. The various thickness- es and positions of the dots are obtained by settinsr out METHODS OF WORK 205 ihe full size of the section on a floor or woriced out to a *fale. If the section is elliptical, dots should be placed at. tiie points where the transition of curves takes place. When the surface of the dome has been floated, the diminishing dots, D, are placed at each side of the in- tended moulding and at their proper positions, begin- i I Section ^Doukle Diminishkh Mouli)inc!>>' False Screep Method. NO. 15. ning above the main cornice, C, and going upwards m rotation but having no dot at the top. The spaces "be- tween the dots are next filled and ruled in, bearing on the variotis dots with the curved rules or templates When ruling the top bay of the screed, the top euiJ d-" (he rule bears on the orisiual floating at the top or ex- 11' ■>ii Hi 206 CEMENTS AND CONCRETES P'i2 M F-St '71 i 1. d u « u' J < b u u J K J u 3 « t 1 U ^ 5 n Z E 5 A 1 1 1 A EuCVATION. Plan, Elevation Double Dimi- MSHKL) Mouldings — False Screed. Method. METHODS OF WOKK 207 treme point, this point Imxv^ tlu' true thickness of the screed. Illustration No. 16 shows the ])lan and elevati(m of the work. Pifj. 1 shows it in i)io<>:re.ss, and Figr, 2 when finished. The A's on plan and elevation (Fi«f. 1) are false screi^ds, the B's are brackets, while C C indicates the diminished running rule. This rule is made as fol- lows:— Fii-st plane one face of a pine board about i/o inch thick, and of sufficient length and width for the desired purpose. On this make a centre line from end to .d. From this centre line set off the width at one end, and the diminished width at the other end; then extend the diminished width lines from end to end, and then plane the running edges to the diminished lines. In order to allow the rule to bend freely to the curved surface, make a series of saw-cuts crossways on the back or bed face. The false screeds are made as already de- scribed. A centre screed for the running rule is made by the aid of a template. This is made with two slippers, one on each side, similar to a running mould, so as to run on the false screeds, the centre or cutting edge of tl-.M template being made to the depth of the proposed screed. The face surface of the bracket is then laid with gauged stuff and finished off by working the template up an^ down. This done, fix the diminished rule, C, on the centre of the screed. The running mould, E, on the plan is made with the slippers, one to bear on the centre screed and against the running rule, and the other to bear on the side false screed. The slippers are made circular on their running edges, so as to fit the circular screeds. A short slipper at the nib gives more freedom and ease when running the moulding, and tlK- mould is not so liable to cut up the screeds. After the moulding is run on both sides, take the running rule off, then cut ! ■» r I 208 CEMENTS AND CONCRETES "H, 1 II. I H; tii;; I'! » I.' I 1 , ■ ".in i '■1 -u t«' '. I'! the false screeds down to the floating, and make the sides of the fillet good, and then fix the enrichment. Fig. 2 hhows the plan and elevation of the finished mouldinji and enrichment. A, on the plan, shows one side of the moulding before the false screed is cut off, and G shows the screed cut oflE and the member made good to the fioating. The amount of diminish from the bottom to the top of the moulding is shown at the brackets B and B, and by the profiles of the cornice on the plan and ele- vation. The bed and section of the enrichment is shown at F on the plan. As this enrichment is diminished (in Avidth and projection) the whole length must be modelled. Running Double Diminished Mouldings, Diminished liule ^epth is obtained by the use of two runninjr rules i?; R, R, are sections of the running rules ; S, S. the slip- .-I ■t METHODS OK WOKK 2U p«'rs: and H, H, the hinges whifli connect th<' two halves of the stock to the slippers. The hin^e which connects the mould in the centn- i.s fixed on the other «ide of the stcK-k. Its position is indicated by dotted lines. Fijr. 2 shows the form of the mould when at the top of the moulding'. The letters correspond with th.Mse on Fijr. 1. The thin sei ms at the centre and sides of the mouldiuK: which are caused by the joint of the mould in the centre and by the joint of the mould and the rubs are cleaned off by hand. This method, like the tint, has the defect that the actual diminish or the whole depth of diminish lies in the fillets of the outside members of the moulding. The difference between the diminished mom- hern and the regular members will be most noticeable on the adjoining membei-s, the vertical fill< ^ the cavettos. If this defect should prove offensive to t. eye, it may to some extent be rt>medied by working these members down by hand, with the aid of planes, gouges, drags, and joint rules, after the moulding is run, so as to reduce the depf li of the fillets, and throw the differ-'ueo into the cavettos. A line should Be set out to the desired diminish on the fillets to act as guides when working the cavettos down. Running Double Diminished Mouldings, Top Bule Method.—liimmn^ double diminished mouldings by the aid of a "top rule" is another method that I have intro- duced for this purpose. The diminish in width is oh- tained by fixing two slipper nmning rules to the de- sired diminish and a triple-hinged mould as previously described, and as shown at Figs. 1 and 2 on the an- nexed illustration, No. 18. Fig. 1 shows the nmning mould, M, and the slipper rules, R, K, at the full-sized or springing end of the moulding, and Fig. 2 shows the running mould and rules at the diminished end. The diminisliing depth is obtained by the aid of a "top rule" ' m ■.-I » i-A i ';iirt 4tis ^m I !r;!iil 1. ■ 'I il !5;;l 'I I ' 212 CK.MKXTS AM» CONCKKTKS M'hich w fixed on tw«) blocks, one at each end of th* mouldinp, as shown at Fig. 3. This shows the elevatioB Elevations, Plan, and Sections of KoNNiNC Mould and Rolbs roR Diminishbh Mouldings— Top-Role Method. NO. 18. of one side of the running moulds at the springingr and diminished ends of the mouldinsr. also the runnincr rules. METHODS OP WORK 213 B is the section of the fixing block at the upringing end of the moulding, and D \h the HxinR block at the dimin- ished end, upon which the top rule, T, is h.ed. This rule is fixed on the slant, to suit the desired ciminish. It must be made sufficiently wide to allow a bear'ng for a part of each half of the stock, M, M, of the running mould, and also fixed over the joints of the nioidd, us shown at T, Figs. 1, 2, and 3. The top rule Ix-ing fixed on the slant, caus(« the running mould to gradually cant over when it is drawn from its upright position at tlu^ springing end of the moulding to the diminished end, as shown at Fig. 3, thus forming the diminish in the depth of the moulding. JI a shows the end section of tho 8l ■ in an upright position when at the springing; end, an M is the section of the stock in a slanting posi- tion when at the diminished endi: of the moulding The dotted lines in both indicate the parts of the stocks in- side the slippers, and the angular dotted line at II, H. indicates the splayed or cut side of the hinge. S S i.s the outer elevation of one .slipper when at each end of the moulding, and R is the .slipper running rule. It will be 8t>en that the running mould at Fig. 1 is some- vhat similar to the triple-hinged running moulds pre- viously described. But there are two important excep- tions, namely, the hinges at the centre end the two sides of the mould. The side hinges for this mould must be cut on one side and the angles rounded off, leaving only one screw-hole, so as to cause less friction, and allow this part of the hinge to turn on a screw when fixed on the slipper. Thi use of this will be seen hereafter. An elevation of a hinge, before and after it is cut, is shown at Fig. 4. The lower hole on the cut half of the hinge is used, because the nearer the "turning-points" or pivots are to the ft 214 CEMENTS AND CONCRETES :!-! running ground or screed, as the case may be, the less ■will the bearing edges of the i-unning mould rise when the mould cants over. For instance, if the "tnming points" were made at the centre of the depth of the nioidd, the bearing edge of the mould would rise from the ground in pi-oi>()rtion to the cant of the stock. This would increase the depth of the lower members (those below the pivots or turning points), instead of dimin- ishing them. This hole must be enlarged so as to admit of a short thick screw to give the necessary strength. It will be undei-stood that this part of the hinge works on the plain part at the head of the screw. Having cut the right and left hinges, they arc screwed on to the stock and the slippers of the running mould, keeping the half of the hinge with the three screw-holes on the stock, and the cut part with one screw-hole on Ihe slippei-s, as shown at II, II, Fig. 1. It will also be noticed that these hinges are fixed at the lower edge of the mould. This is done so as to allow the stock of the jnould to cant from its bnse for the reason already men- tiojied. When screwing the cut side of the plate to the slipper, allow just suificient i)lay for the hinge to turn smoothly but firmly on the screw. The centre hinge con- necting the halves of the stock. M, M, is formed with two pieces of metal plate. The inner ends are rounded off to allow them to turn and a circular orifice one-third the width of the plate is drilled at the circular ends, and tlu'U three or more screw-holes for fixing purposes are drilled on the other ends. The two plates are fastened together with a flat metal ring or with stout copper wire. The thickness of this ring is regulated according to the size of the orifice, but allowing just suflfieient play for the plates to turn both ways when the mould assumt^s a slanting and an angular position, as shown at Fig. 2. il METHODS OF WORK 215 An enlarged view of tht centre hinjfe is shown at Fig. 5. The -centre hinge is screwed on the inner side or profile of the stock, as shown at C, Fig. 1. An enlarged view of part of the stock at the joint, when inverted for fix- ing the centre hinge, is shown at Fig. 6. The top and fiottom edges and the ends of the stock must be rounded off, to allow it to cant over easily. The diminish of this moulding, both in depth and width, as shown in the illus- tiation, is a little more than may generally occur in prac- tice, but this is given to show the various parts more clearly, also what to avoid in the amount of diminish ivhen using this method. The diminishing depth here slio\\-n is about two-fifths, and the diminishing width about one-third. The dimin- ishing depth, by this method, should not be overdone, l)eeause the running mould assumes an angular position l)oth on plan and section, therefore it forms the vertical I)arts of the members in a slanting line and the horiw)n- tal parts out of a level. These defects become more pro- nounced at the dinnnished end of the moul ling, as shown at Fig. 2. The top member can easily I made level and fair by hand, but it would entail too much labor to rectify the defects of the other members, there- fore this method should only be used for snuxll mould- ings or where the diminish in depth is of a slight nature. The .seam at the top member, caused by the joint of the mould, is cleaned off and made gcxxl by hand. Cupola Panels and Moiildiugs.~In order to facilitate the setting out and formation of cupola panels and mouldings, the method of drawing them is given. This will be found very- useful in the general setting out and construction of cupolas, whether in "solid" or in "fibrous plaster." Acinous [)arts ol; cupolas and soffits of arches (from designs by J. Gibl)s. architect, a pupil m dm -I'm ill '-■■ ! 11 V- 1^ I •' 216 CEMENTS AND CONCRETES of Wren, and a great patron of the plasterer's art), with the method of drawing same, are illustrated on plate 11. To draw an octagonal cupola, as shown by the plan at Fig. 1, take A B (the width of one side of the octagon) as the'base line. From the centre of this erect the per- pendicular line D C, then draw the lines C A and C B ; this will give the triangle A B C, forming the plan of an eighth part of the cupola. The profile (Fig. 2) is made by the quadrant of circle (ABC) directly over the plan. Divide half the base line, A B on plan, into seven paits, as here figured, and six of them will make two panels; the seventh will remain for the border. The same divisions must be marked on the profile over the line A B, as follows :— Take for the border at the bot- tom four parts, as shown in the plan ; place them on the profile from the base line to No. 1, and draw a line par- allel to the base line of the plan ; measure the length of the two central lines marked 2 2, and pla^e it in the- profile for the second panel. From thence draw anotluM- parallel line, and measure the length of the two central lines at 3 3 in the plan to find the square height of the third panel, and so on to No. 8, as shown in the plan and profile. The elevation or upright side of this octagonal cupola (Fig. 3) is made by the following geometrical rule. Firat draw the base line (A B) on plan even with the base line (A B) of the profile; on this erect the perpen- dicular line (DC) for the centre of the side; then draw- all the parallel lines as shown by G G, etc. Take hall" the length of each line, figured in the plan, and mark it on each side of the middle line of Fig. 3 until the lengtli of every panel is fixed. From these lines and points the forms or outlines of the panels are taken. Tlu' ituKM- divisii lis are brought over to tlu' number of piiiicls i-oiv- METHODS OF WORK 217 tained therein in the same manner aa they appeal- in Fig. 3. The same rule is used for setting the side jhown at Fig. 4. With regards to the soffits of arches, if they are divided into panels, they must be of any uneven number, as shown at K and L, by having a panel in the eentiv.' The border must not be more than one-sixth nor icss than one-seventh part of the whole breadth. The (juad- rant or profile, E F (Fig. 2), on which the panels of this semi-circular soffit are divided, will be sufficient to ex- plain them. A circular soffit of lesser breadth is shown at M, and one of greater breadth is shown at N. S«H'- tions of ea- i|,i METHODS OF WORK 223 ping out of the jfrocA-.s when the trammel is fixed face downward on the ceilinjr, the inner sides of the fillets should be splayed so as to receive d.)vetailed pins hs shown at H, Fio. 2. This may also I,.. eflVoted by fixiu.*. runnmu' rnl.s on the tilh-ts .so as to overlap ab(„it 1-4 ineh. ov.M- the -roove sj^aee, thus forminf; rebated <.r sqnare ^^-oovc^. The pins are n.ad. with shouhL-rs to fit the -rooves. In both modes a 1-ineh pin „„,,st I,.. i„- ser ed in the trammel pni to prevent the rod drrppi,,.^ A stron- aeeurate, and permanent trammel .an he constructed entirely with metal. To make this, proeure a sulhe.ent length of metal tube, about 1-2 inch in dian,- eter, having; a slot about 1-8 ineh wide, cut lon.ntudi- nalJy. Cut the tube into four pieces, mitrin- the inter- sections, and fix and brace them together in the f.,nn (,f « cross, as already mentioned. A pin n.ade to fit the slot fixed m a ball made to fit the tube, completes one of the' sliding puis. The rod may be made of metal or wood, but J.e latter gives more freedom for chaiiging the sixo tor different sized ovals. Various methods are employed for running oval panel mouldings on ceilings. The most useful are by meaas of trammels, or wood or plaster templates. A trammel is a g(Kid instrument for running oval panels where the mou uings are not wide. Wide mouldings (sav over 1 foot) cannot be run true or uniform in width in one operation with a trammeV because the running mould which ,s fixed on the end of the rod of the tramm-l' assumes a raking position when it is between the ri-ht •ingle points of the ma.jor and minor diameters of J'he oval This raking position takes place at the four joints • or change of cun.^s of the oval, and is more pronounced m extra wide mouldings. This ditTienlty is overcome by running the mouldings in tw.. parts, using a trammel Mi ■i I ■! I- . /'i: ■if ;, I I 'U i I- If i 224 CEMENTS AND CONUHETES 'N. I III ■* ■ 11 mould for running the first or inner part, and a run. ning mould (horsed to run on the run part) for running the second or outer part. This is eflfected by dividing the section of the moulding into two parts, taking care to make the joint at the side of a fillet or in the center of a flat member at the outer side of the part to be run with the trammel mould, so as to allow for a good bear- ing (wide and strong) for the slipper of the running mould used for running the second part,. The running mould for the first part is fixed on the rod of the tram- mel as already mentioned. The running mould for the second part is horsed with a circular slipper cut to fit the curve of the first moulding. If the oval has quick curves, a slipper with two pins will give the best re- sults. If there is an enrichment in or near the center of the moulding, run the moulding in three parts, using the l)ed of the enrichment (which is run with a trammel mould) as a center running rule for running the outer and inner parts, which are run with circular or pin- slippered running moulds, as already described. It will be seen that by using either of these tliree methods, wide mouldings for oval panels can be run uniform on width ; the trammel mould giving the form of the oval to the first part of the moulding, or to the center running rule, {ind the curved slippered running moulds giving the de- sired uniformity of width to the full section of the moulding. Most forms of oval panel mouldings are best run with templates. When run with trammels, or with liulius-rods, the running mould is apt to jnn)p j.nd cause cripples at the junction of the major and minor diam- Templates for Rnnning EUivtical Mouldings. — The true form of an ellipsis can only be derived from the METHODS OF WORK 225 diagonal cut from the cone or the cylinder, and the near- est approximation to this curve must be obtained by continuous motion. There is no other instrument so well adapted for effecting this purpose as a trammel. For a true ellipsis, make the distance from the outer end of the rod to the nearest point or centre pin equal to Template and Pin-Moui.d for Runmno Elliptical Arch Mouldings. NO. 20. half the shortest or minor diameter of the ellipsis, and from the centre pin to the outer pin equal to half the longest or major diameter. This shows the use of a trammel for setting out the lines to make a template for this fonii of ellipsis. The subjoined illustration No. 20 elucidates the method of setting out another form of ellipsis: also an oval hav-. 226 CKMENTS AND CONCHKTES I,' 12 ■! ■i I'll 1 iii^ itM iiiajur uxIh one-third greater tlinn its minor. This alt« Hhows the template and a pin running mould in poHi- tion for running an elliptical arch moulding. The template (Fig. 1) is made to extend below the springing' line of the nrch, so hh to allow tht> mould to be run down to the Mprinj,' of arch and save mitrini;. The template for running the arch extend.* 'o the shaded pjirt; but to utiii/e t\w space the curv. w been continued round to show a method of setting out a template from which an ovjd moulding can be run, the oval haviii'j; its major axis oiu*-third greater than it.s minor. The niel'iod of setting out is as follows: First druw the line AB, the gn>ater diameter, to the desired length; then bisect it, and erect the perpendicular line CD; this being the lesser diameter, is nuide a thirJ less than the line AH. Then bi.sect each half of the line, which will divide the line AB into four ecpud parts and give the centres E, E, which are the centres for describing the ends, as from F to F, and Fl to F2. Then from the centres C and D describe the flat curves from 1' to Fl, and from F to F2. which complete the oval. It is, however, better to set out this template by the trammel, as the junction of the segments of the circles always has a more or less crip- pled look. Fig. 2 shows a "pui-monld" in position when run- ning an elliptical arch moulding. This mould is pro- vided with two hardwood pins in.s<'rted into the bearing face of the slipper. The pins bear on the edge of the template, and owing to their position, and being apart, allow tlu; mould to take any change of curve without "jumping." Before runnintr elliptical moiddings on arches or win- d<)ws, the centres and running rods should be tested, so that the mouldings will interserrt accurately, and so avoid MKTIIODS OF WORK 227 jtimpii flf th.> vhHUKv of (.urv..s. All .vutr.. pim, shoul.I bt' level with eueh .ither, and efiuidistunt from the centre of the areh or window. The outline and intersections of the proposed moiildinj? can he t.>sted by temporarily tix- inu a pencil on the outer and inner pr.)fileM of the run- ning mould, then working the mould over the sermls NO that the pencils will form two lines. I have heard of a three-centered elliptical hood niouldinu beiuK run over a wnidow with what is called a "holt radius-rod." This rod in made in two parts and connected with a liLriKe and held ^trai^-ht when runninjr the lonff diameter with' a l>olt juid .sockets where fixed at the joint. The run- ning mould is fixed on one end, and a centi-e plate o.. the other m the i:sual way. The lon^' diameter of the "louldmg ,8 run first, and when the radiu.s-rod reac^hes the change of curve the holt is drawn baclr, and the short diameter of the moulding run with the .short part of the radiU8-rod. A nail is inserted in a board which is pre- viously fixed in the window opening. The nail mu.st be ^N-d in a line with t!.- change of curve so as to stor. the radius-rod, and hold the long part in position while the short part i.s working. The same operation is re- peated for the other .side of the work. It is needless to say that this method is far too complieated to be serv- leeable for general purpo.ses. Templates are used for running most forms of ellip- tieal panel mouldings. }»la.stererN may make their own templates or running rules by using fib.-oas pla.stor ca.sts as a substitute for W(K)d. This is ..ffected by fi.-st set- ting out a quarter of the r)ropo.sed oval panel, then cut out or run a temporary plaster running rule to fit the inner line, allowing a .space for the .slipp, , f u runnin- mould. Cut a reverse running mould to the section of the proposed fibrous plaster rules (say about 1 inch thick fti iM N' ,1 228 CEMENTS AND CONCRETES h. i' and 3 inches wide), then run the quarter length of the oval, and after making true joints at the ends, cast four fibrous plaster quarters, and then lay and fix them re- versely, thus completing the full oval template or run- ning rule. The full oval rimning rule can also be run in situ and in one operation. This may be done with a trammel or with radius-rods, acf>rding to the form and size of the panel. Strong an stiff gauged plaster or a strong white cement, should be used for the run- ning rule, to enable it to resist the friction of the run- ning mould while running the moulding. Radius-rods are more often used for setting out the lines for oval tem- plates than for running the mouldings. Circular mould- ings — vertical, horizontal, or angular — run off circular grounds require special running rules, so that they will take or bend to the double curvature. For this purpose, cane, flexible metal pipes, and wooden rules, having series of saw-cuts on the backs and sides, have been used, but cast fibrous plaster rules or a jack template are more suitable for most of these purposes. Template can also be made by means of a plasterer 's oval. Plasterer's Oval. — The subjoined illustration (No. 21) elucidates the setting out of this form of oval to any given size, also the method of forming two oval mould- ings from two circle nwuldings. The ovals are formed by running two circular mouldings in plaster, the diam- eter of one being exactly double that of the other. Each circle is cut into four quadrants or quarters. Two of the quadrants of the larger circle form the sides of one oval, and two quadrants of the smaller circle form the ends, the four segments making a fairly good oval. The re- maining segments constitute another oval of similar size and shape. The method is ■ nple and speedy, and it can also be employed for t":.^ f.^rmation of elliptical METHODS OF WORK i2^ M m '-{ jK^^^^^BV^^H '"^S^^^BI^I r^l^^H m 1 1 in ^ 1 ' A a\ 1 1 ' ^^ wivR 1 * i f 1 ' ' fl rjl ' ' ■ *** J ^1 u* iH ■Mm 1 ; p ■ -K t' '^1 ^ik'^ ^^1 •Hi A 11 I'!*- 1 ••- - . H : It* 1 ' i^'!' ^^* . 1 ' ^' [I J 1 1 i;i ' ;» f ,¥ : 'i :i.:.jm ' f liM I ill ',i'''li .J M m 2dM CEMENTS AND CONCRETES > III », ,it ; I is ^^. mouldings on arohes, doors, or windows as well as for oval panel mouldings. The formation of ovals by this method has been employed by plasterers ft)r genera- tions, but owing to the want of a definite rule for set- ting out this form of oval to any given size, its use has been somewhat limited. To meet this want, I have in- vented a method which can be adopted for moNt pur- poses, and which 1 give here for the first time. For want of a better name we have called this a "Plasterer's ()val," for the rea.s(»n that plaster lends itself more read- ily than any other material to the formation of circular mouldings. No one in the building ti-adtvs can form a circle or an oval moulding so quickly and accurately as a plasterer. The method of setting out and of con- si i-ucting this form of oval is as follows: To set out an oval to a given size, the greater diameter biing given, 'i'jike this greater diameter as a base to determine the required di meteis i>r the large and small circle mould- ings, M and N, Fig. 2. Let the line A B, Fig. 1, be the given diameter, .siiy ;J feet; on this form two squares, each according to their diameter would be 1 foot fi inches by 1 foot G inches, a.s shown at C D E F and F G II C ; then draw diagonals in each .square as at vl E and D F iiud C G and F H and at their intersections 1 and 1 as centres draw the circles 1 K and 1 K. The radius in this example would be 9 inches. The quadrants M and M 1 correspond with the same letters in P^'igs. 2 and 3, and Ihey form the two ends of the oval. After this take C as a centre, and with a radius from C to O at E or G de- .s<'ribj that part of the circle L from O L O, which forms the upper side of the oval ; now take F as a centre, and with the same radius describe the lower side, joining K K at and 0, thus forming the plan of the oval as shoAvn bv the line ALB, and the dotted line below C. It will be METHODS OP WORK 231 seen that the re.sj).-i-tivi' centres to describe this figure '/ive Lhe centres and diameters to run the two circle ni()ulJin«s from which the ovals are formed. To construct the oval, iirst make a running mould to the desired profile, using a radius-rod iu the usual man- n.T, for running circles on the flat. Before running the mouldings, set out two lines at right angles on the mould- nig board, taking care to extend the lines a little be- yond the outline of the large ^irele, as shown by the 'L.tted lines (Fig. 2). The extended parts of these lines act as guides for cutting the moulding into e.xaet quad- '•imt.s. The intci-section of them is the centre from wiiich both circles are nui. Apply the running mould, iitid turn it round, so that it leaves a faint mark on the running board to indicate the width of the moulding to be run. The width can also be marked »n' the aid of a pencil, holding it at the outside member, . 1 turning the mould round, repeating thi.s operation on the inside mem- <»''r. On this space drive in eight tacks, two in each Muadrant, leaving tlie heads projectir , about Va inch. The object of these tacks is to prevent the mo"'ulding from lifting owing to plaster swelling, or from moving round while being run. Cover the tacks with clay to allow tlie moulding to be freely taken up after it is run and cut. The moulding is then run in the u.sual way, iind is cut into four quarters, or quadrants. This is done by applying two set-s(iuare.s. one inside and one outside of the moulding; and at one of the quarter lines l.iy a straight-edge ovei- the moidding and against the set-squares. The moulding can then be marked or .sawn at the proper place and angle. The dotted or (piarter Inies divide the m«mldings into quadrants, and give the angles for cutting them. 'i '\t ^1 :ft. m f ^a3 r. - i ■ ^'1 1-4 1 ^ ri . 1 ;! i liii- 232 CEMENTS AND C JRETES The use of extending the lines beyond the moulding will here be seen. A part may be obliterated while the moulding is being run, but the extended part will af- ford a correct guide for the outside set-square. If the quadrants are cut fine, square, and clean, the joints will be scarcely perceptible when the four segments are placed together. When this circle is cut and taken ofl" the board, the radius has to be altered to exactly omc- half of the large circle, and the small circle is run and cut precisely in the same way as the large one. The fuiii' quadrants can now be fixed to form an oval, as shown in Fig. 3. If a quantity of oval mouldings be reciuired. a easting mould can be taken off this oval in which thcs- may be cast. It will be seen that the quadrants ^l and N 1 form the sides of the oval in Fig. 3, and the quad- rants M and M 1 form the ends. It will also be seen tluit after completing this oval there are four quadrants left to form another oval. If but one oval is required, run only one-half of each circle, allowing a little spacf beyond the centre line, so that a square and clean Joint can be cut. A thin saw with fine small teeth should be used for this purpose. Fig. 3 shows the four segments of the moulding in position forming the oval. In this figure the moulding is struck on the outside of the setting-out circle line, as shown in Fig. 1, but the moulding in Fig. 2 is struck on the inside of the setting-out lines. This is simply to show that the same centres can be used for moulding.'^ struck on either side of the lines. A mould for casting oval mouldings, also templates, can also be made by the above process. For this purpose a reverse running mould must be used for running the two circles. A plaster piece mould for ca.sting oval mouldings that arc undercut mav jilsn he fov.nc d hy this method. In this •ill, METHODS OF WORK 233 case the running mould must be made and used as de- scribed for "reverse moulds." Coved Ceilings.— Cqv(}s to ceilings are of various heights, as one-third, one-fourth, one-fifth, &c., of the whole height. The form of the cove is generally either a quadrant of a circle or of an ellipsis, taking its rise a little above the cornice, and finishing at the crown or other moulding. If the room is low in proportion to its width, the cove must likewise be low; and when it is high, the cove must likewise be si>; by which means the excess of height will be rendered less perceptible. An example of two coved ceilings (from designs by James Gibbs) are shown is the annexed illustration No. 22. Fig. 1 shows the plan and elevation of a coved ceiling, with circular windows between the groins. Fig. 2 shows the plan and elevation of a coved ceiling, the design of which is less intricate than that of Fig. 1. The curve of this cove is a quadrant of a circle, as shown by the section at the side. The plans will enable the section of each design to be understood, and vice versa, and the whole will render the method of constructing coves and circular mouldings (m circular surfaces (which is given hereafter) to be more clearly understood. The external and internal angle mouldings in these coves may be formed with a jack template or as described for coves. Circle Mouldings on Circular Surfaces.— The accom- panying illustration, Plate III, is given to elucidate various methods of running circular mouldings on cir- cular surfaces, shows the elevation of a cove suitable for an aquarium or marine hall. The external angle rib moulding, C, and the panel rib moulding, D, spring from the top or weathering of a main moulding, and intersect with a horizontal or crown moulding at the top of the cove. The section of the horizontal n.oulding is shown m *l' ':J 'i, ill I" I'J yf! i '■i I ft [ f!- 1 I. 1 ii 234 CEMENTS AND CONCRETES lii' METH(J1)S OF WOKK 235 at G, and the section of th(.> panel moulding is sliorni «bove D; the soetion of the external rib being of course double that of th.. panel moulding. Where circular or straight mouldings intersect with each other, it is ad- vantageous in most cases to run the circular mouldings first, so that the whole of the moulding can be run "Md leave the intersection to be mitred on the' straight part, which is naturally the easiest part In s<.me examples it is m^t a^lvisable to run the circular part fii-st. For example, if the crown or horizontal mouldin- gs sho^vn at G, Fig. 1, was the lower part of a large • rown moulding made to intersect with small covp 'Mouldings, it would be be.sl to run the straight mouldin- (n-st, and then cut away as much of the straight mould" >ng as will allow th(. nib of the running mould to pass while running the circular moulding. For the section ■n this example there would be very little mitrin-- to do Jis It would simply be a butt mitre up to the back of thJ circular mouldin-.^. The external rib mouldiii.^ C is 'H'.st run with a jack template. The circular panel '"onldm.os (one-half of a moulding is .shown at D) can IH- nin by two metho.ls. By the first, the inouldin-^ is rnn m three parts, using a sledge-slippered running ""•uld fixed on a hinged radiu.s-rod. and the two straight IMrts are run from running niles. By the seco^nd "..'thod, the whole moulding is run at one operation bv asmg a fibrous pla.ster template, made as already de- scribed. Forming Nichcs.-X\,hos are recesses formed in walls •s.-metimes for the purpose of placing some ornamental' object m them, such as statues, vases, &c., and thev are often constructed -n thick walls in order to save mate- rials The plans or bases of niches are generally semi- circular, but some partake of all the segments under a n Si J '^ l!i. •' »-fi III f.l'i • ! itl ^*.' , I i ' B: li'; 236 CEMENTS AND CONCRETES >l» semicircle, while others are elliptical, and in a few in- stances they are square or rectanj^iilar. Th elevations of niches are generally in accordance with cheir plans, but variations from this rule are sometimes met with. The crown or heads of niches are generally plain, but they are sometimes enriched with scalloped shells, &c., or panelled with mouldings. With respect to the pro- portion of niches, there is no fixed rule, but the general one is twice and a half their width for their height. Various methods are employed in the formation of niches. The crowns of circular niches are generally run with a mould, because being circle on circle and small in surface, it is difficult to finish them true and smooth by hand. The accompanying illustration (No. 23) elucidates two methods of forming semicircular niches with the aid of running moulds. Fig. 1 shows the elevation, and Fig. 2 the section of the crown and a part of the body of niche, with the centre-boards and moulds in position when forming the crown of the niche. Fig. 4 shows the section of the body of the cove, with the mould in posi- tion when forming same. By the first method the niche is formed in two operations, and by the second method it is formed in one operation only. For the first method, cut a running mould to the section of the niche, as shown at B, Fig. 1, then fix it on the centre board. A, with two hinges, keeping the upper surface or mould plate levol with the top edge of the centre board, as shown on the section of the niche. Fig. 2. This also shows the end section of the centre-board and the mould, with the mould plate and a hinge. The dotted line indicates the distance the mould travels. After this, fix the com- bined centre-board and mould on the wall, taking care that the top edge of the centre-board is level and ex- h METHODS OF WORK 237 Forming Niches with Running Moutw. ■vm ■ m ■ i i:!'' mm I ' « NO, 23. M. :; !'• 238 CEMENTS Ai\D CONCKKTES actly at the tprin^rinf; of the crown, C. The face of thf wall must be floated plumb, and an allowance made by means of dots for the thickness of the setting coat be- fore the centre4M)ard is fixed. After the crown is fin- ished, the cent'e-board and running mould Ls taken otV the wall and sejjarated. The moiild is then hoi-sed witii twx) slippers to allow of its runniiif; the body or vertieiil part of the niche. The mould works on a running rule fixed on one of two screeds which are formed on the face of the wall, one on each side of the opening. Care must be taken that the screeds are plumb with the centre-boavd dots. Fig. 3 shows an elevation of the mould when horsed. B is the mould, D is a connecting board on which the mould is fixed by means of the cleats, C, C. and F, F, are the .slippers. Fig. 4 shows an end section of the horsed mould in position when running the body of the niche. The base is finished by hand. By the second method the niche is run in one opera- tion, as already mentioned. This is effected by cutting a running mould to the vertical section of the niche, then fixing a pivot at the bottom and a bolt at the top. A wood block, with a socket to fit the bolt on the mould, is let into the face of the wall at the top of the niche, and temporarily fixed, then another block with a socket to fit the pivot of the mould is fixed at the bottom of the niche. Care must be taken that the sockets are plumb and in a line with the centre of the niche, also that they are in a line with the face of the wall, so as to allow the mould to form a true semicircle with perpendicular arrises. Place the pivot of the mould in the socket, and push the bolt up and secure it, and the mould is ready for working. Fig. 5 shows a section of the niche with the mould in position. A is the mould with the pivot and bolt, and METHODS OP WORK 2S1) B, B, Mtv till" socket blocks. A plan of the niche and mould is shown at V'm. (i. This also shows the plan of the pivot block, and a boird which is sometimes used to secure the block. The dotted line indicates the dis- tance the mould travels. When there are splays or beads on the an for small work and a radius-rod for large work. In either ease they must be fixed on the centre of the mould, so as to be in a line with the mould plate. After the crown is run, the mould plate of the crown surface is cut off. and the remaining part of the mould u.sed for runninu; the vertical mould" ings. In some designs a small moulding, such as an imjH>st moulding, is carried round the body surface of the niche, and in a line with the springing of the crown. Thi.s moulding can be nui in a similar way as shown at Fig. 5, or by fixing a flexible wood or a plaster running ndo on the body of the niche for the mould to run on. *•. II 'Ji J'i" ■■ i i' J' n If 240 CEMENTS AND CONCRETES The crowM of nichw that are parallel with amall mouldings are best executed by making a model of the design, then moulding' it and casting, and fixing as many as are required. In niche crowns that are enrichetl with shellM, foliapo, &c., the enrichment should be cast with the crown surface an a background. Fibrous plas- ter is well adapted for the construction of niches. For this purpose a reverse easting mould should be employed for forming the ca>«tH. This is made by cutting a re- verse running mould to the section of the niche, and after a sufficient length of the bt)dy is run, cut the mould in half and run the crown. Then fix it on the end of the run body, and then fix rules at the sides and ends to form fences and rims, thus completing the casting iiioi'ld. Any of the above methods for forming niches with vimning moulds can be advantageously used for forming the body and crown of the Ionic niche when such is re- ♦ inired. Running an Elliptical Moulding in Situ. In No. 24 a method of running an elliptical curve with ii trammel is shown. Fig. 1 represents the front eleva- tion of the trammel mounted and in working order, and Fig. 2 is a section of the same. Take two floor boards, B, long enough to reach to the .springing line of the arch, and nail them on the back of two lengths of 5 in. by 2 in., A, which, as shown may be somewhat longer. Fix these up inside the jambs of the opening, taking care to see that they are perfectly up- right, and keep them the thickness of the trammel boards (which is 1 in.) back fi-om the face of the openinf on which the architrave Ls to ho. Then cut three pieces of Ml. I'l iODS OF WOHK 2tt 6 in. by 2 in., C, tight in between and secure them in place with 3 in. cut nails, talcing care to see that the Mtom H,de of the top (,„e is above the springing line I hen prepare the trammel boards, D and E 6 in by 1 rLASTEIUs TBAMHU. rOR U-UTTICAL A«CHITaAV«.- NO. 24. i"., and cut the slots, which are % in. wide and of « length which may be easily ascertained by simple geom. otry. Halve the board., tog-ether at the joint and fur- ther secure them by screwing a plate of the thickest sheet zinc obtainable on the back, as per Fig. 3 Nail the i » M' L I I •■!- i !l ''; if i 1^ I. ii ,1:1 I 242 CEMENTS AND COMCRBTES boards up as shown, keeping the horizontal slot centra] on the springing line and the vertical slot exactly in the centre of th*^ opening, and be most particular to see that the whole lot is perfectly upright and level. Next pre- pare the trammel stick, 2 in. by 1 in., and mount the mould on the top in the usual manner, as shown. Then insert the pins in holes bored in the stick and secure by a screw through the edge. Have them just thick enough to work comfortably in the slots, and keep the centre of the pin XI, the distance of the rise, and the centre of the pin X2, the distance of the half span from the bot- tom member of the architrave. All the timber may be deal except the pins, which must be of some kin-i of hard wood. If well made and used with care this trammel ought to serve many times ; the pins, of tywirs*, «eelaces where large surfaces have to be covered, it is the least costly process that can be adopted. It has also the great advantage of being non-absorbent, and it can be washed down at any time. The artist is untrammelled by difficulties of execution, but he should Ifcar in mind that the more carefully he draws his lines and the simpler he keeps his composition, the more charmed with the process he will be, and the better will be the effect of his work. MISCELLANEOUS MATTERS 247 A well-known artist records his experience of sgraffltto (ts fellows: "Bake and sweep out the mortar joints, then give the wall as much water as it wiU drink, or it wiU absorb the moisture from the coarse coat, as it will not set, but merely dry, in which case it will be worth little more than diy mud. Care should be taken that the cement and sand which compose the coarse coat should be prop- erly gauged, or there may be an unequal suction for the fiHLshmg coats. The surface of the coarse should be well roughened to jrive a good key, and it should stand some days to thorouprhly set before laying the finishing I'oat. When sufficiently set, fix your cartoon in its des- tined position with nails; pounce through the pricked outline; remove the cartoon; replace the nails in the ivynster holes; mark with chalk spaces for the different colors, as indicated by the pounce impression on the coarse coat; lay the several colors of the color ooat ac- cording to the design as shown by the chalk outlines- take care that in doing so the register nails are not dis- placed; roughen the face in order to make a good key for the final ooat. When set follow on j^ith the final sur- facT coat, only laying as mu » as can be cut and cleaned lip in a day. When this is sufficiently steady, fix up the cartoon in its registered position; pounce through the inieked outline; remove the cartoon, and cut out the de- sign m the surface coat before it sets; then if the regis- ter ,s correct, cut through to different colors, according to the design, and in the course of a few days the work sliould set as hard and as homogeneous as stone, and as damp-proof as the nature of things permit. ''When cleaninjr up the ground of color which may be exposed, care should be taken to obtain a similar quan- tity of surface all through the work, so as to .^et a broad '■yi 4^ t,' « 248 CEMENTS AND CONCRETES effect of deliberate and calculated contrast between the trowelled surface of the final coat and the scraped sur- face of the simple contrasts of light against dark, or dark against light. The following are the proportions of the various coats : ' ' Coarse coats : One of Portland cement to 3 of washed sharp coarse sand. "Color coat: One and one-half of air-slaked Port- land to 1 of color laid Vs inch thick. Distemper coloi-s are Indian red, Turkey red, ochre, umber, lime bluo; lime blue and ochre for green; oxide of manganese for black. In using lime blue, its violet hue may be over- come by adding a little ochre. It should be noted that it sets much quicker and harder than the other colors named. "Final coat, internal work: Parian, air-slaked for twenty-four hours to retard its setting, or fine lime and selenitic sifted through a fine sieve. "For external work: Three selenitic and 2 silver sand. "When finishing, space out the wall according to the scheme of decoration, and decide where to begin, and give the wall in such place as much water as it will drink; then lay the color coat, and leave sufficient key for the final coat. Calculate how much surface of color coat it may be advisable to get on to the wall, as it is bet- ter to maintain throughout the work the same duration of time between the laying of the color coat and the fol- lowing on with the final surface coat; for this reason, that if the color sets hard before laying the final coat, it is impossible to get up the color to its full strength wher- ever it may be revealed in the scratching of the decora- tion. When the color coat is quite firm, and all shine has passed away from its surface, follow on with the MISCELLANEOUS iMATTERS 249 final coat, but only lay as much as can be finished in one day. The final coat is trowelled up, and the design is incised or scratched out. Individual taste and experi- ence must decide as to thickness of final coat, but if laid between % inch and 1-12 inch, and the lines cut with slanting edges, a side light gives emphasis to the fin- ished result, making the outlines tell alternately as they take the light or cast a shadow." Another method which I have used in sgraffitto for external decoration was done entirely with Portland cement. This material for strap-work or broad foliage, or where minuteness cf detail is unnecessary, will be found suitable for many places and positions. Three colors may be used if required, such as black for the background, red for the middle coat, and grey or white for the final coat. These colors may be varied and sub- stituted for each other as desired, or as the design dic- tates. The Portland cement for Boating can be made black by using black smithy ashes as an aggregate, and by gauging with black manganese if for a thin coat. The red is obtained by adding from 5 to 10 per cent, of red oxide, the white by gauging the cement with white mar- ble dust, or with whiting or lime, the grey being the nat- ural color of the cement. After the first coat is laid, it is keyed with a coarse broom. Tlie second coat is laid' fair and left moderately rough with a hand-float. The suction of the first coat will give sufficient firmness to allow the third coat to be laid on without disturbing the second. The third coat should be laid before the sec- ond is set hard. The second and third coats may be used neat, or gauged with fine sifted aggregate as re- quired. The finer the stuff, the easier and cleaner the work, and the cut lines are more accurate and free frore* jagged ?dgps. The outlines of the design may be m n \ f i' i I 250 CEMENTS AND CONCRETES IK)ttnced or otherwise transferred to the surface of the work, and the details put in by hand. The thickness of the second coat should be about 3-16 inch, and the third coat about Vs inch. The thickness of one or both coats may be varied to suit the design. The beauty of effect of this method of linear decoration, aided by two or three colors, depends greatly on the treatment of design, the clearness of the incited lines, and the pleasing color contrasts. It will be seen that in the three methods described there is a similarity, yet the method of using two color coats on a darJc floating coat will give more ^■Jlriety and effect. There is a large use for sgi'affitto in the future, as it has been in the past, and its use is inti- mately bound up with the future of cement concrete. In order that the foregoing examples of high-class sgrafBtto may not deter the young plasterer from trying his *' 'prentice han' " in this class of work, some simple designs are given in the annexed illustration (No. 27). Pig. 1 shows a design for a frieze in two e(»lors. The ground may be black or red, and the ornament buff or grey. The colored material for the ornament is laid first, and the colored material for the ground laid last. Fig. 2 shows a design for a cove in two coloi-s, one with two shades. The ground is grey, and the band work liuff. A deeper shade of buff for the honeysuckle can be ohtained by brushing this part with li(iuid color made deeper than the original gauge, also by laying a black coi t first, and in a line with the honeysuckle; then laying the buff stuff for the band work next, aJid then laying the grey color last. In the latter case the honeysuckle i.s cut deeper than the band work, so as to expose the black coat. Different effects can be obtained by changing the col- MISCELLANEOUS MATTERS 251 ors. Sections of the surface of the frieze and part of the moulding are 8ho\*Ti at the ends. Fresco.— The plasterer is closely allied to the artist painter. He has always to be in readiness to plaster the wall for the artist. Owing to the alliance with distin- guished artists, and the various methods of preparing mid using the plaster materials, I am induced to give a few notes, also extracts from writers of authority. t Tig :iig?^¥r TTJ-- TiT-^^^^^^ :3i Fig. I. ) I'ig. 2. -SURAkHTlO I'RIF.ZE I.N TwO COLOURS. NO. 27. Fresco is a mode of painting witli water-colors on freshly laid plaster while it reiiiain.s naturally wet. It is called "fre.sco" either because it was m-ifrinally used ou build- ings in the open air, or I.eeause it was done on fresh plaster. Fresco is an Jiiieient art, being mentioned by 'I r.'i. «,l tf| M 111 'M 111 I 252 CEMENTS AND CONCKETES Pliny. Mr. Flinders Petrie found some remarkably fine specimens on floors and walls at Tel-el-Amama, which reveal the state of the art four thousand years ago. Pine frescoes were discovered in the ruins of Pompeii, In one of the principal houses the plaster walls are adornoil with theatrical scenes; in an inner room is the nielie often to be seen in Pompeiian houses. The frescoes on the wall consist of floral dados. Above this is a whole aquarium, with sheila, plants, birds and animala. They are all executed in their natural colors, and are natur- ally and gracefully drawn. Michael Angelo's beautiful fresco on the ceiling of the Sistine Chapel in the Vatican is grand both in conception and execution. It measures 133 feet in length by 43 feet in width. Raphael's fres- coes in the Vatican, Farnesina Palace, &c., are wonder- fully fine, and may be regarded as the high-water mark of Cinque Cento decoration. For fresco or huon fresco the lime has to be care- fully run, and the sand should be white, clean, and of even grain, being well washed and sifted to free it from impurities or saline properties. Silver sand is pre- ferred by some artists. The older the putty lime, the better the results. The lime is slaked in a tub, and then run through a fine wire sieve into a tank, and after beinp covered up, is left for three months. It is then put into the tub again, and re-slaked, or rather well worked, and run through a fine hair sieve into earthenware jars or slate tanks, and the water which collects at the top drawn or poured off, the jars or tank being covered over to ex- clude the air. Lime putty in this state will keep for an indefinite time without injury. From 2 to 4 parts of Band to 1 part putty is usual. iSJarble dust alone is sometimes used in place of sand, >nd also sand with f^iwA parts. Every difference of li-.ne and sand found MISCELLANEOUS MATTEKS 253 in various localities should be considered and tested be- fore using. A soft sand is quickly dissolved by a .strong lime, and a plaster made of this is fit for use Nooner, and will deteriorate more quickly than a plaster made with a less powerful lime and a harder sand, or with marble dust. The wall surface to be plastered must be well scraped and hacked, the joints raked out and brushed, and the whole surface well scrubbed and wetted. The rendering is done with the best possible prepared old coarse stuff. If the walls are rou^'h or uneven, they should be first pricked up and then floated. In any case, the surface IS left true, and with a rough face, to receive the fin- ishing coat. Portland cement or hydraulic lime gauged with sand, also gauged with coarse stuff, has been nsed where the walls were damp (damp is fatal to fresco), or if exposed to the atmasphere. When Portland cement or hydraulic lime is used, the work should be allowed to stand until thoroughly dry to allow any contained sol- uble saline efflorescence to come to the surface. This is l)rushed off with a dry brush, and a few days are allowed to elapse to see if there is a further efflorescence. When this is all extracted and swept off, and the artist is ready to commence, the wall is washed with a thin solution of the fine setting stuff", and then laid about !/« inch thick, with well-beaten, worked, and tempered fine setting stuff. It Is then rubbed with a straight-edge and scoured with a hand-float (using lime water for scouring) until the surface is tnie and of uniform grain. Most artiste prefer a scoured surfaee without being trowelled. No more surfaM should be covered than can be conven- iently painted in one day. While the plaster is still soft and damp, the cartoon is laid on, and the lines and details pounced in or indented by means of a bone or -m { ! i I J ■ t:lR' \k if- ! i i: 254 CE>1*]NTS AND CONCRETES hard-wood tool. Should the liniHhinf? coat get too dry in any part, it can be made tit for woric by usinB a fine spray of water. The method oi" pltwterinp and the ^au^- ing of raaterijilH may wliKhtly vary uceordinp to the de- sire of the painter and the kind of fresco in hand. Tin? following iK taken from an old tuanuscript dated 1()99 : - "1. In paintinir the wall to make it endure the weather, you must gr'niil colors with lime water, milk, or whey, mixed in size. "2. Then pjiste or plaster must be made or well- waahed lime, mixed with powder of old rubbish stones. The lime must be oft«'n washed till finally all the salt i« extracted, and all your work must be done in clear and dry weather. "3. To make the work endui-e, stick into the wall stumps of headed nails, about "> or 6 inches asunder, and by this means you may preserve the plaster from peeliii);. "4. Then with the paste plaster the walls a pretty thickness, lettinjj it dry; but scratch the first coat with the point of your trowel lonjovays and croeswayB, a.s soon as you have done layinjj on what plaster or paste you think fit. that the next plastering? you lay upon it may take good key, and not come off nor part from the first coat of plastering: and when the first coat is dry, plaster it over ajrain with the thickness of half a barley- corn, very fine and smooth. Then, your colors being al- ready prepared, work this last plastering over with tho said colore in what draught or design you please — his- tory, ete.,1 — so will your painting unite and join fast to the plaster, and dry together as a perfect compost. "Note — Your first coat of plaster or paste must be very haired with ox-hair in it, or else your work will crack quite through the second coat of plastering; and will spoil all your painting that you paint upon the sec- MISCELLANEOUS MATTERS 255 ond coat of plastermg; I tlio w^eond coat that ii. laid on of paate or piaster tnere must be no hair in it at all, but made thua:— Mix or temper up with well-washvil lime, fine powdor of old Htonc« (ealled flni«hiuK Htutl) and .harp prit aaiid as much a. you 8hall have .K!ca.sion for, to plaater over your first coat, and plaater it all very smooth and even, that no rouKhness, hills, nor dales, be «,.en. n.»r scratch i.r your trowel The bc*t way i« to float the second coat of plastering thu8:-After you have laid it all over th. first coat with your trowel as even and smooth as po^- sible. you can then take a float made of wood ven- Hmooth, and 1 foot long and 7 or 8 inches wide, with 'a handle on the upper side of it to put your hand int.. to float your work withal, and th.« will make your plastering to he even; and lastly, with your trowel yo„ may ma^e the said plastering as smooth as possible 5 In painting be nimble and free; let your work be bold and strong; but be sure to be exact, for there is no alteration after the first painting, and therefore p£ure ^""^ ^^'"* '"""^'^ "* "'*'*' '''"" ""^ ^""P"" «^ "6. All earthy colors are best, as the ochres, Spanish brown terra^vert, and the like. Mineral colom are naught. ''7. Lastly, let your pencil and brushes be long and soft, o henvise your work will not be .sm(X)th; let your colo^ be full, and flow freely from the pencil or bn.s • and let your design be perfect at first, for in this therJ IS no alteration to be made." Fresco ^rcro.-Closely allie.l with the genuine fres,.o (fresco buono) ,s another kind e.lled tVeseo secco (di-v ) or mezzo (half) fre«c Th,. plaster work for fresco see' CO 18 simdar to that used for fresco buono. It is allowed if, 2* 256 CEMENTS AND CONCRETES ; t i to stand until thoroughly dry. The surface is then rubbed with pumice-stone, and about twelve hours before the painting is commenced it is thoroughly wetted with water mixed with a little lime. The surface is again moistened the next morning, and the painting begun in the usual way. If the wall should become too dry, it is moistened with the aid of a syringe. There is no fear of joinings in the painting being observable, and the artist can quit or resume his work at pleasure. Joinings are distinctly noticeable in the frescos in the Loggia of the Vatican. Fresco secco paintings are heavy and opaque, whereas real fresco is light and transparent. While the superiority of fresco buono over fresco seceo for the hi^rhest class of decorative painting is unquestionable, still the latter is suitable for many places and forms of decorative paintings. The head by Giotto in the National (lallery, from the Brancacci Chapel of the Carmine at Florence, is in fresco secco. Indian Fresco and Marble Plaster. — ^"Fresco painting is a common mode oi decoration in Jeypore, and is used ill ornamenting walls inside and outside of buildings — also as a dado or border round the wainscot or on the floor — and on any surface where decoration is desired. The beautiful marble plaster on which it is done is com- mon Rajputana, and i.s used to line the surface of walls or floors, and of baths or bath-rooms. It is admirably Jidapted to places whore ''oolness and cleanliness are de- .*irpd, and is very suitable to a warm climate. It would jio doubt be more commonly used if pure lime could be obtained. "To prepare the marble plaster, the process in use in .Icypore is as follows: — Take pure stone lime, mix it with wator until it ha.s dissolved, then strain it through a fine cloth. In Jeypore the lime is made from pounded - MISCELLANEOUS MATTERS 257 marble chips or almost pure limestone. The substance which remains in the cloth is called bujra, and all that passes through the cloth is called ghole. These should be prepared a few days before they are required so as to allow time to settle, and every day the water should be changed, so as to leave a very fine sediment. "Jinki, which is also used, is pure marble ground to a very fine powder; kurra is a mixture of bujra and jmki; and jinkera is a mixture of ghole and kurra. These are the materials used, and the names by which they are known in Jeypore. In Madras, where similar plaster is used, it is made, I believe, from shells and the mgi-edients are probably known by other local names. "If the surface to be polished is a slab or stone, the r.mra mixture consists of 1 part by weight of burja and IV2 parts nf jinki. If the surface is a wall or a chunam floor. It must be first thoroughly dry and consolidated.- then take equal parts of burja and jinki to form the kurra mixture. Mix the burja and the jinki well to- gether; add a little water and grind them well together, m the same ways as natives mix their condiments, by hand with a stone rolling-pin on a slab, until they form n perfectly fine paste. Wet the surface which is to be polished, and spread over it a layer of this kurra mix- ture, about Vs inch thick. Then beat the surface gently with a flat wooden beater, sprinkling a few drops of clean water on the surface occasionaUy. Then mi^ a little ghole with the kurra plaster (described above as .linkera) and lay it on evenly with a brush as if it were a coat of paint; rub the surface over carefully with any olose-grained flat stone, called in Jeypore jhaon. The ob- ject of this is to smooth down all irregularity and roughness, and to prepare a smooth even surface Sprinkle a few drops of wat.'r and repeat the process i:- ill 258 CEMENTS AND CONCRETES taking care that no hollow l icea are allowed to re- main. Paint it over with fine jinkera (ghole and kurra mixed), increasing the proportion of ghole, and rub it down well with a flat stone (jhaon) as before; then paint it over with ghole only, after each coat rub- bing it doAvn carefully with the jhaon stone. After this, rub it all over with a soft linen cloth, called in Jeypore nainsukh, folded into a pad. Then give it another coat of ghole, and now rub it down carefully with a piece of polished agate, called in Jeypore ghinti, until it begins to shine. The surface must not be allowed to dry too rapidly, or a good polish will not be obtained. Care must be taken that the lime has been thoroughly slaked in the first instance, or it may blister; also that the sur- face, if a floor, is thoroughly consolidated, as the least settlement naturally causes the plaster to crack. The polishing process with the agate cannot be repeated too often; the more it is carefully done, the better will be the polish. Every time the agate is moved backwards it should be made to pass over a portion of its previous course, so as to prevent any mark or line at the edge. Lastly, if the surface is to remain white, take some water which has been mixed with grated cocoanut, and lay it on the surface. Let it dry, and then rub it down with a fine cloth folded into a pad. If any coloring is desired, the same process is adopted until the polishing with the agate is begun. This is only doflf Rightly. If any pat- tern is desired, it is drawn on paper and pricked out. The paper is placed on the surface, and is dusted with very finely powdered charcoal tied up in a muslin bag. The charcoal passes through the perforations and marks the plaster surface. The paints are mixed with water, and are painted on by hand while the surface is still Iresh and moist hence the term fresco. Where a large MISCELLANEOUS MATTERS 259 surface has to be done, it is necessary to employ several men at the same time, in order that the surface might be all painted before it has time to dry ; or else the pat- tern must be so arranged that the connection of one day's work with the work of the next will not be amiss. Immediately after the surface has been painted the colors are beaten in with the back of a small trowel, in such a manner that the color is not rubbed or mixed with the color adjacent. As soon as it shows to the touch that the color has become incorporated with the plaster, the surface is painted over with water mixed with grated cocoanut, and is then polished down with the agate. "The following colors can be used in process :— Lamp black; red lead; green (from a stone known as hara pathar); yellow (from a stone called pila pathar) ; brown or chocolate. A little glue is mixed with the two first colors, and gum only with the others. The colors used are mostly earths or minerals, as other will not stand the action of the lime. Vegetable pigments can- not be used for this model of painting, even when mixed with mineral pigments, and of the latter only these are available which resist the chemical action of the lime. The lime in drying throws out a kind of crystal surface which protects the color and imparts a degree of clear- ness superior to that of any work in tempera or size paint. The process, although apparently simple, re- quires dexterity and certainty of hand, for the surface of the plaster is delicate, and the lime only imbibes a certain quantity of additional moisture in the form of liquid colors, after which it loses its crystallizing quality, and the surface or a portion of it becomes rotten. It is' only after the lime has dried that such flaws are dis- covered, and the only remedy is to cut away ihe de- 'At'h • M ill Pi">ii' I In- 260 CEMENTS AND CONCRETES fective portion, lay on fresh pilaster and do the work over again. The colors become lighter after the plaster dries, so allowance must be made for this. The advan- tag'« which this process possesses are clearness, exhib- itiag the colors in a pure and bright state; the surface is not dull and dry as in tempera or size painting, nor glossy as in oil painting; it can be easily seen from any point, and it is not injured by exposure to the air; it will stand washing, and can be cleansed with water with- out injury." SCAQUOLA. Eistorkd. — Scagliola derives its name from the use of a great number of small pieces or splinters; scagliole of marble being used in the best description of this work. It is said to have been invented in the early part of the sixteenth century by Guido Sassi, of Cari, in Lombardy, but it is more probable that he revived an old process, and introduced a greater variety of colors in the small pieces of marble and alabaster used to harden the surface, and better imitate real and rare marbles. It is sometimes called mischia from the many mixtures of colors introduced by it. The use of colored plaster for imitating marbles was known to the ancients, although the pure white, or marmoratum opus and oZ- harum opus, mentioned by Pliny, was more used. The plastic materials used by the Egyptians in coating the walls of their tombs partook of the nature of marble. 'I'he ancients also used a marble-like plaster for lining the bottoms and sides of their aqueducts, which has endured for many centuries without spoiling or cracking. In the decoration of their domes the Moors used colored plasters, which have stood the ravages of tune. The MISCELLANEOUS MATTERS 261 beautiful chunam or plaster of India, as used by the natives, has a hard surface, takes a brilliant polish rival- ling that of real marble, and has withstood for many- ages the sun and weather without sign of decay. The roofs and floors of many houses in Venice are coated with smooth and polished plaster, made at a later date, strong enough to resist the effects of wear and weather, without visible signs of crack or flaw, and without much injury from the foot. Scagliola was largely employed by the Florentines in some of their most elaborate works. It has been used in France with great success for archi- tectural embellishment. The rooms are so finished that no additional work in the shape of house-painting is required, the polish of the plaster and its evenness of tint rivalling porcelain. Scagliola is the material used. At times the surface of the plaster is fluted, or various designs are executed in intaglio upon it in the most beautiful manner. Scagliola is one of the most beautiful parts of decora- tive plaster work, and it is regrettable that there should not be a greater revival of such a charming and beautiful art. Its limited use in recent times is greatly owing to its manufacture being restricted by rules and rigid methods and even prejudices, and being confined to monopolists, who kept the method secret until it was looked upon as a mystery which greatly enhanced its cost. But through the information now at hand, com- bined with a little practical experience and enterprise, there is no valid reason why architects should not adopt it for second or even for third class buildings. It possesses great beauty, and is capable of affording grand effects and the richest embellishments in architecture, Scagliola, in skilful hands, c>»ji be produced in every vajnety of color and shade, in every possible pattern, in M t i" 262 CEMENTS AND CONCRETES every conceivable form and size, from a paper weight to the superficial area of a large wall. It can be made at a price that would enable it to take the place of the most durable material now in use. Experience has proved that it will last as long as the house it adorns, and with an occasional cleaning, it will always retain its polish and beauty. It has been produced in past days in our own and other lands, and carried to such high ex- cellence, that many of the precious marbles, such as jasper, verd antique, porphyry, brocatello, giallo an- tique, Sienna, etc., have been imitated so minutely, and with an astonishing degree of perfection, as to defy de- tection. It will not only retain its polish for years, but i-an be renovated at much less comparative cost than painting and varnishing marbled wood, or plaster work. It is cheaper and more satisfactory to use scagliola in the first instance than to go to the expense of plastering walls, columns, etc., with Keen's or other kindred ce- ments, used for their hardness and ready reception of paint, which are to be afterwards marbled and var- nished. Both are imitations, but painted marble can never be compared with scagliola, which has the look, color, touch, and polish of the more costly natural marbles. Varioits Artificial Marbles. — ^Various patents have been taken out for the production of artificial marbles, having for their bases plaster of Paris. These patents vail be briefly mentioned here. Evaux's Artificial Marble is composed of plaster mixed with albumen and mineral colors, the ground being zinc white. Rowbotham also employed plaster and albumen soaked in a solution of tannic acid. Lilieuthal makes an artificial marble with Keen's cement, slaked lime, and curdled mUk. MISCELLANEOUS MATTERS 263 Pick's " ycoplaster."—Thia composition was patented in 1883, aatl is composed of 75 per cent, of plaster, mixed with feldspar, marl, coke dust, and pumice-stone. Gule- ton and Sandemaa patented an artificial marble in 1876. It is composed of Keen's cement backed with fibre, and soaked or brushed on the back with a solution of as- phalt. The slabs were made in glass moulds. La- roque's patent marble is formed of plaster and alum gauged with gum water, the veining being done with threads of silk dipped in the required colors. The backs of the slabs or panels are strengthened with can- vas. Mur Marble is composed of a mixture of Keen's and Marin's cement in equal proportions, made into a paste, with a solution of sulphate of iron and a small quanti- ty of nitric acid in water. The slabs are dried and tarred at a temperature of 250 degrees F. for about twenty hours, and when cool are rubbed, colored, var- nished, or japanned, as required. There is another patent formed of plaster, gauged with a solution con- taining tungstate of soda, tartaric acid, bicarbonate of soda, and tartarate of potash. Another is composed of Keen's cement 10 parts, ground glass 1 part, and alum Vj part, dissolved in hot water. Ouattaris Marble is obtained by transforming gypsum (sulphate of lime) into carbonate of lime (marble) Tlu-re are two methods. The first consists of dehy- tlrating blocks of gypsum, and then hardening by im- mersion in baths containing solutions of silicate of soda sdicate of lime, chloride of lime, sulphate of potash' soda, acid phosphate of lime, etc. The blocks are cut mto slabs or carved before being put into the bath. The second method consists in dehydrating the gj-psuni, and bathing in some of the above chemicals. They are then III K a *• /, M t !■ i\ I i. 264 CEMENTS AND CONCRETES dried and burnt at a red heat, and allowed to ood. After a second burning and cooling, the products are ground as for plaster. This powder is called "Marmo- rite". The marmorite is gauged in a trough with some of the water from the baths as above, kneaded into a paste, and the colors added and mixed. The paste is then put in- to moulds and pressed, and when set they are taken out, dried, and finally polished. Mineral colors are used. Yellow and its tints are obtained with citrate of iron dissolved in oxysulphate of iron, sulphate of cadmium, chloride of yttrium, chromate of lithium, and yellow of antimony. Red and its tints are obtained with dragon 's blood, sesquioxide of iron, mussaride red, and sulphate of didymium, and the salts derived from it, which give a rose color. Azure blue is obtained with sulphate of sodium mixed with acetate of copper and tartaric acid and oxide of cobalt. Green and its tints are obtained with verdigris, hydrochlorate of cobalt. Black is ob- tained by pyrolignite of iron reduced by boiling in gallio acid with sirco black. Black marble is also obtained by immersing gypsum blocks or slabs or the cast mar- morite in a hot preparation of bitumen. During this operation the dehydration of the material under treat- ment is accomplished, and the bitumen not only pene- trates the mass, but fills up all the pores and spaces evacuated b> the water which was contained in the ma- terial treated, and a hard mass of brilliant black is ob- tained in every way equal to Flanders marble. It is said that the above imitation marbles are largely used in Florence. Scagliola Manufacture. — Scagliola can be made in situ or in the work shop, according to the requirements of the work; but in either case it is necessary that the work place should be kept at a warm temperature, and the MISCELLANEOUS MATTERS 265 work protected from dust or damp atmosphere. The plaster should be the strongest and finest in quality, and free from saline impuritiea It should be well sifted to free it from lumps or coarse grains, which otherwise would appear as small specks of white in the midst of the dark colors when the polishing is completed. Glue water should be made in small quantities, or as much as will suffice for the day, as it deteriorates if kept too long. Glue tends to harden the plaster, and gives gloss to the surface. Unfortunately it is also the cause of its sub- sequent dullness and decay when exposed to moisture and damp air, hence the necessity of using the best glue, good and fresh glue water. If scagliola is required to be done in situ on brick walls, the joints should be well raked out and the walls well wetted. This gives a good key, stops the excessive absorption, and partly prevents the evil effects of saline matters, that are found in most kinds of new bricks. These saline matters are the prin- cipal cause of subsequent efflorescence which sometimes appears on plastic surfaces, and is so unsightly and dis- astrous to surface decorations. Saline matters are also caused by acids, used in the manufacture of some ce- ments. Saline is also found in mortars made with sea water, or with unwashed sea sand. These impurities can be avoided by carefully selecting, mixing, and work- ing of the materials. Brick walls for scagliola should be allowed to stand as long as possible, and wetted at in- tervals. This allows more time for the saline to exudo and be washed off. The exudation may be hastened or the salts absorbed and killed by brushing the walls with a solution of freshly slaked lime. This is allowed to stand until dry, and then cleaned off by scrubbing with warm water and a coarse broom. If space permits, a wall bat- tened and lathed is the best preventive. Scagliola slabs, I 1>66 CEMENTS AND CONCRETES saline scoewed to plugs or battena, are protected fr^ ifl and internal damp. Iron columns to support overhead weights, and fixed as the building proceeds, are often covered with scaglio- la. If the work is done in situ, the iron core is sur- rounded with a wood skeleton and strong laths, or paint- ed wire lathing. The wood templates are cut, equal to the lower and upper diameters of the columns, and one fixed at the top and bottom of the shaft. The ground work is then ruled fair with a diminished floating rule. This gives a guide and equal thickness for the scag (the trade abbreviation for scagliola stuff) . The floating coat is composed of the best and strong- est plaster procurable, and gauged as stiff as possible with sufficient strong size water, so that it will take from twelve to twenty-four hours to set. The floating is gen- erally brought out from the lath in one coat. A tenth part of well-washed hair is sometimes mixed with the gauged plaster, to give greater toughness and tenacity. The surface must be carefully scratched with a singly- pointed lath, to give a sound and regular key for the .scag, which Is laid on in slices, and pressed and beaten with a stiffish, square pointed gauging trowel, somewhat lik»' a margin trowel. The scag is laid about Ys inch fuller than the outline, and when set, the surface is worked do\vn with a "toothed plane." This plane is similar to that used by cabinetmakers for veneering pur- poses. The irons are toothed in various degrees of fine- ness, and set at an angle of 70 degrees. If the columns are fluted, a half-pound plane is required for the flutes. As the planing proceeds, the outline is tested at inter- vals with a rule, as a mason does is ushs;; a straight- edge when working mouldings. A planed or chisel-cut surface shows up the grain and figure of the marble MISCELLANEOUS MATTERS 267 much better than if ruled. A rule is apt to work out or otherwise spoil the flgtire of most marblea. The t eating on the slices may distJirb the figure of the marble at the outer surface, but if the scag is pauped stiff, the inner portion wih be intact, hence the advantage of planing. To obtain greater cohesion between the scag and the floating, the latter is brushed with soft gauged stuff just before each piece of the former is laid. The scratching is also filled up at the same time, so aa to obtain the full power of the key with the least amount of pressing on and beating the scag slices in position. When the shaft is planed, the wood colors are taken off; then the baae and necking moulding, which has been previously cast, are screwed in position, using plaster (colored the same as the ground of the marble) for the joints. When dry, the whole is atoned and polished Pilasters or other surface work done in situ are executed by similar pro- cesses. Cast and turned work should always be support- ed by strong wooden frames, formed with ribs, and cov- ered with l^ inch to i^ inch thick sawn laths. The strength of the frames is regulated according to the posi- tion and purpose of the intended work. For example, a column with base placed on a square pedestal would not require so strong framing as the pedestal which has to support the column and base. Also bt.ng on the floor level, it is more exposed to contact and pressure. Fram- ing is also necessary for fixing purposes, and to allow for the work being handled fr. \y when being moved from the work shop to the building, and when being fixed. Small work may be made without framing. Turned columns are framed in two different methods, each way being for a special purpose. If it is an "in- dependent column", or in other words a complete col- umn, not intended to surround a brick or iron core, the m «i ■S-. 268 CEMENTS AND CONCRETES frame is made lighter and thinner, and in such wayii m to admit the column to be cut either in two equal pnrta, or with one-third out, or just as much as will allow ilu« larger part to pass over the iron core. Care mmt be taken that the inner diameter of the skeleton frame is greater than the diameter of the iron core. This is to allow for fixing. The outer diameter of the frame is mad«' about 1 inch less than the finished outline of column, to allow Vs inch for the core and V2 inch for the scag. Thf two parts of the frame are fixed with wooden pegs (not naib), so that they may be sawn when the column is cut into halves. This is not done until the column is pol- ished and ready for fixing. The parta are best separated by cutting with a thin and fine-toothed saw. The thin- ner the cut the better the joint. The two parts ai-c fixed on the iron core with brass screws or clamps, from 3 to 4 feet apart, and the joints made good with colored piaster aa before. Sometimes a zigzag joint is made, tho one side fit*'ng the other, to give the marble or figure a more regular and natural appearance. The joints are then stopped with various tints, these being the same gauge as used for the face. Sometimes the framing is made longer than the shaft, so as to project ai each end. These projecting parts ar»* used as fixing points for screws, and binding round with hoop-iron before the plinth and cap are fixed. Thew parts project the edges of the work while being moved and fixed. Considerable skill and patience is requiri'd to make a strong joint, well polished, and imperceptib''} to the eye. The frames are made with solid ends, with a square hole in each to fit the spindle. The solid ends are cut out of inch deal, and are used to keep the skele- ton firm and in a central position when the spindle is turning on its bearings. One of the ends is fixed to MISCELLANEOUS MATTERS 269 flangv of the spindle with screws. If a case c»<. ..in is being made, the solid ends are taken off before the coU limn k cut ; but they form permanent parts of the fram- ing for an independent column. The mould is fixed at one side, and level with the centre of the spiiidle, which *8 the cen*..« ,-f the column's diameter. Care must be taken t!u' i.c profl'" of the mould plate to the centre .. ? of the required diameter at of the i'3ch . ! . M the eh:i nri' mt m without wood framing. They .ha plaster core screwed to the 1 .' i*'>.m .„ I I arabola, to give the form of the hoilt-w iiv.dt ( >ii th(> c"re a coat of scag is laid and al- lowed to si't. Tlu- -s scratched to give a key for the coarse pi.' . aich !'< rms the body of the vase. This is formed to lue uesired outer profile by means of a mould fixed on the outside, and muffled to allow for a thickness of outside scag. When the core is run, the muffle is taken off, and the scag laid, keeping it about Vs inch thicker than the true profile, to allow for turning and stoning. When the scag is set, it is turned, and then the vase is taken off the spindle and plaster core. The spindle hole is used as a key for a slate or iron dowel for fixing the vase on to the square plinth. The vase is then polished. Cheap work is usually run or turned with a mould. This is done to save turning with chisels, hut it spoils the true figure o .nost marbles. A more recent way of imitaang marbles is known by I he name of Marezzo, which does not require so much polishing, being made on plate glass or other smooth surface. Keen's superfine plaster is used. The mod(! of making Marezzo is described later on. Specimens of the real marbles, to give the color and form of veining. m 270 CEMENTS AND CONCRETES spots, and figures, will be of gre&L service to the be- ginner. Mixing. — Mixing the colors is an important part of scagliola manufacture, and the following colors, mixing and mode of using, will serve as an index for the imi- tating of any other marble that is not detailed. Fine plaster (not cement) is ased for making the best class of scagliola, gauged with sized water, which is made by dissolving 1 lb. of best glue with 7 quarts of water. (This is known in the trade as "strong water".) The stuff, when gauged will take about six houre to set. All mix- ing is done on a clean marble or slate slab. One of the principal arts is the mixing, but there are no two men who mix exactly alike, and it is largely a matter of ex- perience. The chopping or cutting into slices with a knife is another important point in the mixing, apart of course from the special colors. Where there are two shades of one color in any given work, the cutting does not affect their original shade. No dry color is used, only ground water-colors. The beginner had better ex- periment with a small sample of "Penzatti" or Pen. ranee marble. With one gill of size water, gauge plaster middling stiff, then mix thoroughly with the gauged plaster a little red. Do the same with a little black. (See quantities below.) Blend this stuff pi-operly by working it on the bench with the hands (not tools), then roll it out, and cut it into slices about one inch thick. Take up these slices, and part them with the fingers about the size of a walnut, and put t)iem aside, a little distance apart, on a bench. The veining in this instance *.i white. Over these little lumps scatter half a handful of crumbs, made by re- serving a little of the gauged plaster, and making it crumbly with dry plaster, mixing with it i few small MISCELLANEOUS MATTERS 271 « bits of alabaster or marble. Then gauge a little plaster in a basin, with a tooth brush, about 2 inches wide, dip into this gauged plaster, and smudge the little lumps all over with it. Knock these lumps together into a big one, and chop the big lump three times. (This chopping means cutting with a knife into slices once, and knock- ing up again ; cutting with a knife a second time, and knocking up again ; and then cutting with a knife a third time, when it is finished.) This lump is then ready to be cut into slices, and applied to any purpose required ; but in this case, being wanted for a specimen, it is cut into slices about Yq inch thick, and laid close together flat on a sheet of paper, and allowed to remain until set. It is then planed, and when dry polished. This opera- tion is an embodiment of the principle of "scag" mix- ing nearly from beginning to end, only submitting on« color for another for the various marbles. The mixing is generally known as plain and rich, and may be described thus: Take a Sienna pedestal, for instance. Two shades of sienna, plain mixing; one or two shades of dark with veining, rich mixing, both done on the same principle as Penzatti. They are cut into slices and laid on alternately. All veining of any color is done as described above, only modified by the consideration that if strong veining is wanted the stuff must be stiffish, and for fine veining it must be slightly softer. Various^sized measures for the water and scales for weighing the color should be used. Pats of each gauge should be set aside as te^t pats to determine when the main portion of stuff is set. It is advisable to number the pats for future refetence as to quantity of colors, time of setting, and tints when dry. The various colors and tints are gauged and chopped aa previously described, and according to the marble required. The con- b brown; 1 shade grey; 1 shade 274 CEMENTS AND CONCRETES lemon chrome. Veining, burnt sienna, with small ala- baster spots. Sienna Mixing. — 5 oz. sienna to y^ pint, A^rk shade; 3 oz. sienna to V^ pint, middle shade; 2 oz. sienna to Y2 pint, light shade. Griotte Marble. — 10 oz. of light purple brown to 1 pint 5 oz. of dark purple brown to ^ pint, with ala- baster spots. Ground with red veins, and small spcts. Spanish Buff. — Burnt sienna, 2 shades, with large ala- baster spots. Veiuing, white and blue black, with small alabaster spots. Ground with red veins, and blue spots. Light Vcrd Antique. — 2*4 oz. green to Yn pint; 1 V^ oz. black to 1 gill ; 14 gill black to 1 gill grey shade. Dark Vrrd Antique. — Green spots cut; grey spots cut ; black spots with green and grey. Veining 2V^ oz. green to V2 P'"^ (rich mixing) ; 2*^ oz. dark green to % pi"t (rich mixing) ; % oz. black to Vii pint (rich mixing). Plain mixing, same as above, with small alabastei spots, and small black spots. Black and Gold. — 5 oz. of black to 1 pint. Veining, 2 shades dark sienna to V^ pint (rich mixing) ; 2 shades light to y^ pint (rich mixing) ; 2 parts light and grey, with alabaster spots, and crumbs. Veining must be stiff ; 3 oz. of black to 1 gill. Walnut. — 2 parts burnt umber; 1 part rose pink. Veria Alps Marble. — 5 oz. black to 1 pint. Veinin^r. V/i oz. of green to l'/. gills; 14 oz. green to 1/2 J?J11> with black crumbs ehopped three times for the ground. liossc De La Vantz Marble. — Rich mixing with indi- go blue — 1 shade light purple brown; 1 shade dark pur- ple brown ; 1 shade Venetian red. Veining, black for the ground, and white and green veining for the mixing, with alabaster spots and crumbs. MISCELLANEOUS MATTERS 275 Polishing White Scagliola. — ^White scagliola is often made with superfine Keen's cement. A small portion of mineral green or ultramarine blue is added to improve and indurate the white color. "White work requires spe- cial care to prevent discoloration or specks. When the work is left for drying purposes, or at the end of the day, it should be covered up with clean cotton cloths to pre- vent the ingress of dust, smoke or being touched with dirty hands. The tools should be bright and clean. Steel tools should be as sparingly used as possible. When the cement has thoroughly set and the work is hard, it is rubbed down with pumice-stone, or finely grained grit- stone, by the aid of a sponge and clean water, rubbing lightly and evenly until the surface is perfectly true. It is then stoned with snake- water (Water of Ayr), using the sponge freely and the water sparingly until all the scratches disappear. Afterwards well sponge the sur- face until free from glue and moisture. It is now ready for the first stopping. Stopping is an important part of the polishing process, and should be carefully and well done, to ensure a good, sound, and durable polish. First gauge a sufScient quantity of cement and clean water in a clean earthenware gauge-pot. The gauged stuff should be about the consistency of thick cream. It is well dubbed in, and brushed into and over the surface, taking care that no holes or blubs are ]eft. When the stuff on the face gets a little stiff, scrape off the super- fluous stopping with a hard-wood scraper having a sharp edge. Then repeat the brushing (but not the dubbing) with the soft gauged stuff, and scraping two or three times, or until the surface is solid and sound. The work is now left until the cement is perfectly set. It is then stoned again for the third time with a piece of fine snake- stone, and stopped as before, with the exception that the 276 CEMENTS AND CONCRETES superfine stopping is not scraped off, but wiped off ^th soft clean rags. The work is left until the cement is set and the surface dry. It is then polished with putty powder (oxide of tin), which is rubbed over the surface with soft clean white rags, damped with clean water. In polishing mouldings, the stone must be cut or filed to fit each separate member of the moulding. Polishing Scagliola. — The polishing of scagliola is slightly different. It is rubbed down with a soft seconds (marble grit) or gritty stone, using the sponge and water freely until the surface is true. The glut and glue are ••leaned off with a brush and sponge, using plenty of water, until the pores are free from grit. The moisture is sponged off, and the work left until sufficiently dry. It is then stopped in the same manner as white work, but using stiff stopping for large holes and steel scrapers in- stead of wood. The stopping is made with the same kind of plaster, size water, and color as was used for the ground color of the marble that is being imitated. The stopping and stoning is repeated as before, and it is finally polished with putty powder, using pure linseed oil instead of water. The repeated operations of stopping and stoning must not be proceeded with until the previous stopping is perfectly set, and the work dry. A small portion of spirits of turpentine is sometimes added to the gaufjed colored stuff to facilitate the drying. The work between each combined stopping and stoning will take from one to five days to dry, according to the size and thickness of the work and the state of the atmos- phere. Never dry the work by heat. The thorough dry- ness and hardness of the work are most essential be- fore proceeding to polish with the putty powder and lin- seed oil, because any contained damp will work out and spoil the polish. Work not perfectly dry may take a MISCELLANEOUS MATTERS 27'/ high polish, but it will soon go off when the damp comes through. Columna or large hollow work are not so liable to be affected by the damp, as it may escape through the back ; but there must be some opening or ventilation tu allow it to finally escape. If the polishing is well and carefully done, the polish produced on scagliola will equal, if not surpass, that on real marble. Tripoli polishing stone, sometimes called alana, is a kind of chalk of a yellowish-grey color. Water of Ayr stone is also used for polishing. In large work a rubber of felt dipped in putty powder may be used. Salad oil is sometimes used for finishing. Linseed oil makes the hardest finish, and dries quicker. Marczzo. — Marezr.o artificial marble manufactured from plaster or Keen's cement and mineral coloring mat- ter is mtide in wood or plaster moulds for moulded work, and on slate or glass benches if in slabs. If thick plate glass is used, the worker has the advantage of being able to look through it to see if the figure of the work re- quires altering. Glass also has the advantage of leaving a smoother and more polished face. All wood and plaster moulds should be got up with a good face, and properly seasoned, to save stoning and polishing the face of the work. Keen's cement may be used advantageous- ly in making Marezzo, especially for chimney pieces, or other works required for exposed positions. Keen's cement for Marezzo should be of the highest class. If the cement is not of the best, it will effloresce, rendering the work of polishing difficult, if not spoiling it alto- gether. Keen's cement requires no size water, but in gauging either Keen's or plaster, no more should be gauged than can be conveniently used. The quantities of colors. Keen's cement, plaster, and size water should be measured and gauged pats kept for future reference. » ■ 278 CEMENTS AND CONCRETES All gauge-pots snould be of earthenware, as they are more easily cleaned out, and do not rust, as is the case with metal pots. All the tools should be kept bright and clean, as when working scagliola. Marezzo is made in the reverse way to scagliola, as the face or marble is put in the mould first, and the core or backing put on afterwards. All the mineral colors should be of good quality, in fine powder, and ground in water, known as "pulp." A number of basins should be handy, and there should be a supply of twist silk in skeins varying in diameter from Va to 14 of an inch, and cut into lengths of 14 to 18 inches. For common work, good long flax fibre may be used. Canvas is also required. One end of the silk or fibre skein must be knotted. These are known as "drop threads." After the moulds are made, seasoned, and oiled, the young hand may begin by trying t8 make some easy marble, for a slab or chimney-piece. Gauge Keen's extra superfine cement or superfine plaster, in a large basin labelled No. 1, well mixing it until about the consistency of cream. This is pure white. Now pour a small quan- tity of this white plup into two small gauge-pots, Nos. 3 and 4. Pour a third of what remains in the No. 1 pot into another gauge pot. No. 2. Take some black> colored pulp, and make No. 1 a blackish-grey. Color in the same way No 2. only very much blacker than No. 1. No. 3 is now slightly tinted with pulp from No. 3. This leaves No. 4 pure white. Then take a skein of twist (or threads), dip into No. 4, the pure white, and well charge it by stirring it about with the fingers ; take out the threads, taking each end between the thumb and forefintrer of each baud, and with the remaining fingers ci each hand separate thf^ threads, allowing plenty of MISCELLANEOUS MATTERS 27» "swng," and strike this into the face of the mould, mak- ing each stroke at different angles, recharging the threads when necessarj'. Repeat this process with pulp from No. 3, but iu a lesser quantity; then dip your finger ends into No. 2, and fling drops about the size of large peas all orer the veining. These drops must be thro^m on with considerable force, so as to cut into the veinsi as much as possible. Dip the fingers into No. 1, and throw on No. 2, ufling alternately from each gauge- pot until you get a uniform thicku'jss of surface (seag), about Vti inch in thickness. Nov/ run a trowel over th»s t«) lay down any ridges. Cover the work with a piece of canvai), laying it evenly, smoothly, and without wrinkles. Be careful to put the canvas in the proper I)lace, as moving it would spoil the lines of the veining; thfti spread a quantity of dry coarse Keen's lightly over th«' entire surface. This will absorb any superfluous moisture through the canvas. After the canvas and t'ourse Ket'n's have Iain from ten to twenty minutes, or nei'ording to the stiffness of the gauge of the marble, the L-unvas and coarse cement are easily lifted off. Should any portion of the face of the scag leave the mould, and adhere to the canvas, it is taken off and put back in its place in the mould. The whole surface is now trowelled to render it dense and hard. The moisture should be sufficiently absorbed, or the trowelling may spoil the figure. The proper absorption of the moisture by the dry cement through the canvas, and well trowel- ling, are most essential to good work, ensuring hardness and dfiusitv. The core or backing is now made by using tVie eooi-se Kt'en's i)reviously used for absorbing the moisture frtsm the face, gauging it with sciine fresh eoai-se Keen's as stiff as Dossible. This is laid on as thick tis re((uired. K ■i H"- i1 |;j^■ 280 CKMENTS AND CONCRETES the face of the scag be ver dry, spread a thin coarse gauged Keen's, so as to give a |)erfect cohesion between the marble and the backing. The flat surface of the backing should always be ruled or floated straight with » uniform thickness, so as to give a true bed for the cast when it is taken out of the mould, and laid on a bench ready for stoning, stopping, and polishing. This can be done as soon as it is thoroughly set and hard, and in the same manner as scagliola. Marbles having long stringy veins require a different method of putting in the veins. Take the skeins, or "threads," by the knot with one hand, and thoroughly saturate them with the veining mixture, and run the finger and thumb of the other hand down the threads to clear them of any excess of veining color with which they may be charged. Then give the end not knotted to your partner, holding the knot in your left hand. Pull the threads asunder, so as to take the form of the veins of the marble you are copying, then lay them in the mould, leaving the knots hanging over the edge of th»> mould, or at least visible, to facilitate their removal when required. The threads should be arranged on the mould so as to take the form of the veining. The other colored materials are then thrown upon the thread veins, which quickly absorb the coloring matter from them; care being taken that the various colors are thrown or dropped from the finger tips, to form the figure of the body of the marble that is being copied. When the mould is sufficiently and properly covered with the marbling, take hold of the knots and withdraw the threads. These should be cleaned by passing down the finger and thumb for future use, saving the superfluous stuff for filling up any holes in the marblinsr. The absorption of the use of canvas and dry coarse Keen s, MISCELLANEOUS MATTERS 28] and the flllinff in of the backinf? or core, is then proceeded with as before described. Granites, porphyries, etc., are made in a different manner. For porphyries with white and black specks, make a slab of white Keen's about Vs inch thick, antl unothor in h]m:k, the same thicknws. When they an* set and hard, chop them into small pieces, then r»in them through H sieve, havint; a mesh to let throuph the pieces of the rj*(juired size only. The pieces retained in tlu- sieve can be broken and sieved n^Hin. The whoh' is now sieved again through a smaller mesh, which re- tains only the size wanted. The refuse can b<* used for small work or backing up. When the gauged stuff t'oi- the facing is mixed of the required tint (a rcddLsh- brown), damp the black and white specks with the gauged color by means of a trowel and rolling, can being taken not to break the edges and faces of the black and white specks. When it is well mixed, lay iv onto the face of the mould about 3-16 inch thick, pres.s. ing it as firmly and evenly as possible. Then absorb th(» moisture by means of canvas and dry coarse Keen's, trowel it well to give density, and fill in the backing or core as before. For "Rouge Royale," **Verd Antique,'* &c., requiring large white patches of irregular size, th*- sieving can be dispensed with. The white pieces ar*« broken haphazard, and pieces of alabaster can also be inserted in these, and many other marbles, due regara being given to the size and quantity, so as not to produe** an unnatural effect. The remainder of the figure is formed with the "drop threads," and the other colors being thrown on. From this description of Marezzo, the workman wilf understand that in the case of marbles classed as ' ' Brec- cias," such as "Rouge Royale," "Black and Gold," &c.. f ,1' V 11 I' i i i\ ■ I'. MICROCOPY RESOLUTION TEST CHART (ANSI and ISO TEST CHART No. 2) I.I 1 45 1^ jjm !i 1^ 2.5 2.0 1.8 ^ >^PPLIED \MAC3E Inc IS"^ 1653 East Main Street ^tSi Rochester. New York 14609 USA ^^ (716) 482 - 0300 - Phone ^S (^'6) 288 - 5989 - Fan 282 CEMENTS AND CONCRETES having patches and rough jagged veins in them, he must have flat pieces of the required color previously made and broken up, or alabaster, as the case may be inserted into them, and the veining done with the "drop threads'* and that fine or long veining threads are not required; that unieolored marbles require no veinini? threads; that the long veined marbles require the long threads, and in some cases the "drop threads" as well, and that granites, porphyries, &c., require no threads; that black is diffi- cult to make owing to the pure white cement requiring so nuich color; and finally, that in all cases, whether Ma^- rezzo or scagliola, the polishing is done in a similar man- ner, whether using plaster or Keen 's cement. 'J'he details given must be carefully followed to pro- duce work artistic in figure and appearance. The direc- tions for making "St. Ann's" so far as manipulation is foncerned, apply to all others. A little patience, prac- tice, and perseverance will soon give confidence and ex- l)ertness in producing sound scagliola and Marezzo. Granite Finish. — Granite is a peculiar finishing coat of plaster which is sometimes used in this country to imi- tate granite. For granite finish, first render the walls with hydraulic lime, and when nearly dry lay with a thin coat of the same material but colored light brown. Then while this coat is still moist, splash the surface lightly with white stuff, then with black stuff, using only half a.s much a.s used for the white stuff, i '»e red stuff is best applied by dotting the surface with a small brush ehiirged with the colored stuff. After these colored lime stuffs are firm, but not set, the surface is carefully trow- ♦•llcd, using the minimum of water so as not to mix the various colored stuffs. The surface Is sometimes left in a rough state, or as left when splashed. After the surface MISCELLANEOUS MATTERS 283 ia firm, it is set out and jointed to represent blocks of gralte. Granite Plastering. — Granite plastering is a method, introduced by the author, to imitate granite. This mode of imitating granite is based on the scagliola process. It is also somewhat similar to the granite finish, and gives better and more reliable results. The method of executing granite plaster work is as follows: First select the most suitable lime or cement for tho situation, such as Portland cement or hydraulic lime for exterior work, and Parian or other white cement for interior work. Having decided on the material, gauge three different colored batches, one white, one red, and one black, taking care that the stuff is gauged stiff and expeditiously so as to obtain a hard substance. The material is colored to the desired shades, as described for scagliola or colored stuccos. When gauged the stuffs are laid separately on a bench and rolled until about .'M6 inch thick, and when nearly set they are cut into small irregular cubes and allowed to set and harden. The wall is then floated, ruled fair, and the surface keyed, and when set it is laid with a thin bedding coat of simi- lar stuff used for the floating, but colored light brown. The colored cubes are then mixed together in due propor- tions, and gauged with a portion of the light brown col- ored stufi and laid on the thin coat while it is soft. The whole is then firmly pressed with a hand-float until a close, compact, and straight surface is obtained, taking • are when pressing the stuff not to break the cubes. After the stuff is set and perfectly dry and hard, the surface is rubbed down and polished, as described for scagliola or for marble plaster. The bedding coat should be sufficiently thick to receive the colored cubes, other- wise the larger cubes will project at parts, and cause I ■' ! 1 i iJff- -m 284 CEMENTS AND CONCRETES extra labor in making a uniform and straight surface. Unless the cubes are fairly level when pressed, the sur- fa^' will have a spotty appearance, besides being more ditdcult to polish. Where expense or time is a consid- eration, a striking appearance is obtained at less cost than polished work, by simply finishing the surface with a cross-grained hand-float, and a semi-polished surface is obtained by trowelling, or by scraping the surface with a joint-rule. Grey or light-colored granites are imitated by altering the colors of the cubes and the beddiag coat a« desired. Bold and striking effects on wall surfaces can be obtained by a combination of different colored granites, laid out in bands and borders. The effect can be increased by the introduction of borders in sgraffito, irith th« bands in granite plaster. PART II CEMENTS AND CONCRETES, AND HOW TO USB THEM. It is not necessary to the workman that he should ex- pend a long period of hLs valuable time in reading up the history of cements and concretes, nevertheless it is jiroper he should be acquainted with the outlines of the origin, growth, and development of cements, concretes 51 nd their uses, and to this end the following brief his- torical summary is presented, sufficient to give the work- man a fair idea of the beginning and growth of the use of cements and concretes : The word concrete is of Latin origin, and signifies a mass of materials bound or held together by a cementing matrix. The Romans used concrete B. C. 500. They made good use of lime concrete both in the construction of buildings and roadways. "Roads," says Gibbon, "were the most important element in the civilization of ancient Rome; and the cost of the Appian Way was such as to entitle it to the proud designation of *Re- gina Viarum' (the Queen of Roads)." The Appian (the oldest of the Roman highways) was commenced by Appius Claudius Caius, when he was censor, about three centuries before the birth of Christ. It extended from Rome to Capua, whence it was consequently carried on to Tarentum and Brundusium. Antonio Nibby, an archaeologist of the highest authority, states that the Appian Way had an admirable substructure, with lime concrete materials superimposed, and large hexagonal 285 Ml 3i )'¥■•■"• rl Am m i'lf 286 CEMENTS AND CONCRETES blocks of stone laid on the top of all. The Romans built concrete aqueducts, often several miles long, to couvey water to the cities. The palace of Sallust, the historian, was built about B. C. 50, and was frequently used as a residence by most of th • emperors until as late as the fourth century. It was partly burnt by Alaric in the year 410. This once magnificent edifice was erected on a strange site, partly in the valley at the foot of the Quirinal Hill, and partly on the top of the hill. The latter portion of the palace, which was of great extent, has been almost wholly destroyed by the builders of the modem boulevard. The walls, which were thick and high, were most valuable examples of the Roman use of concrete, unfaced by brick or stone. There is still visi- ble evidence, in the form of impressions left on those walls, which clearly demonstrates their method of cast- ing walls in situ by means of wood framing. Rows of timber uprights, about 10 feet high, 6 inches wide, and 3 inches thick, were fixed along both faces of the in- tended wall. Boards about 10 inches wide and ly^ inches thick, in suitable lengths, were then nailed hori- .zontally along the uprights, thus forming two parallel wooden walls, into which the concrete was laid and rammed until the space between the boards was filled to the top. "When the concrete had set, the wood fram- ing was removed, and refixed at the top of the concrete, the whole process being repeated until the wall was raised to the required height. This concrete was far more durable than brick or stone. The jerry-builders of the modern Rome had no diflBculty in pulling down the stone wall of Servius, but the concrete walls required the use of dynamite to complete their destruction. After withstanding the wear and tear of many centuries, and the repeated onslaughts of the Goths and Vandals, it was HOW TO USE THEM 2S> left to the nineteenth-century speculative builder to de stroy those interesting remains. The use of concrete for floors and roofs is of great an* tiquity. It was employed for this purpose by the Ro- mans in the time of Julius Caesar, Professor Middleton in his first book, "Ancient Rome," states that the whole of the upper floor of the Antrium Vesta is formed of \ great slab of concrete, 14 inches thick, and about 20 feet in span, merely supported by its edges on travertine cor. bels, and having no intermediate supports. In his sec. ond book, "The Remains of Ancient Rome," Professor Middleton mentions that the Romans used concrete for the construction of the Pantheon, which was erected about the time of Christ. A curious and apparently un- accountable feature as regards practical pui-poses is that the concrete is faced with bricks, which were faced again either with stucco or (in special cases) with marble veneer. The Professor gives a sketch showing the ex. terior facing and the section of a wall of this kind, the entire mass being composed of concrete, except a facing of thin bricks, triangular in plan, with the points in- wards. As the author observes, these bricks could not possibly be intended as a matrix for concrete, as it would not have withstood the pressure of the latter while in a wet state. It must therefore have been necessary to re- tain the brick and the concrete with an external tim- ber framing, as in the case of unfaced concrete. There could be no gain of strength or other benefit to compen- sate for the time expended setting the brick skin. The dome of the Pantheon is 142 feet in diameter and 143 feet high. This is also formed with brick-faoed concrete. It has often been described and even drawn by various authors as essentially a brick dome. Professor Middle- ton remarks there must have been very elaborate eon- M •m 288 CEMENTS AND CONCRETES struction of centring for this and other massive concrete vaults. He states they employed a method, which has become common of late, to avoid the necessity of build- ing up the centring from the ground. They set back the springing of the arch from the face of the pier, so as to leave a ledge from which the centring was built, the line of the pier being afterwards carried up until it met the intrados of the arch, leaving it a segmental one. The Professor also found signs of timber framing for Avails in the remains of the Golden House of Nero, un- der the Thermae of Titus, where, he says, "the chan- nels forme4 by the upright posts are clearly visible. These upright grooves on the face of the wall are about earthenware for making sewer tubes. Experience has proved that the acids present in li(iuid sewa^^ and the gases generated by the action of a faecal decomposition do not injure the concrete tubes, but on the contrary tend to harden them. Among the many unlikely purposes for which concrete has come into use may be mentioned stat- uary, vases, fountains, sinks, tanks, cisterns, cattle- troughs, silos, railway sleepers, platform copings, man- telpieces, chimney pots, tall chimneys, tombs, tombstone's, and coffins. Concrete is slowly but surely coming to the front as one of the most useful, economical, constructive, and decorative materials for works requiring strength and endurance. It may now be said to be indispensable to the architect, engineer and builder. Concrete, when properly made with a Portland cement matrix, and slap or a similar aggregate, is undoubtedly the best fire-proof material iised in any building construction. It can be made thoroughly waterproof and acid proof, and may be moulded or carved to any design and colored to any shade. After this brief historical review of concrete, the practical considerations of the modem working by pla.s- terers claim attention. Before describing the methods of working the concrete, a description of the material.<«, with their characteristics and application, is given as a preliminary guide and reference. Matrix. — ^Matrix is a word used to designate any nui- terial having a setting, binding, or cementing power, such as limes, plaster or cements. For concrete paving, stairs, floors, or cast work for external purposes, it may be truly said that there is only one matrix, namely, Port- land cement. f * ^^' '■ lit 294 CEMENTS AN£> CONCRETES Aggregate. — This is a term applied to those materials held or bound together by the matrix. Aggregates may- be fibrous or non-fibrous, natural or artificial. The nat- ural aggregates comprise granite, stone, shells, marble, slate, gravel, sand, metal filings, &c, : the artificial slag, brick, pottery, scharff, clinkers, coke-breeze, ashes, glass, &e. ; and the fibrous slag, wool, coir, fibre, reeds, hair, cork, tow, chopped hay, straw, shavings, &c. The fibrous aggregates while being principally of a natural kind, are generally of a vegetable nature. They are commonly used with a plaster matrix for the interior works. The best aggregates for the upper coat of concrete paving are granite, slag, and some of the hard limestones. The best and cheapest for the first layer or rough coat are broken bricks, old gas retorts, clinkers, whin and other stone?. Stone chippings from masons' yards and quar- ries are cheap and good. Shingles and gravel are also lused, but owing to their round and smooth surfaces they afford little or no key for the matrix. When found in large quantities and at a cheap rate, they should be l)roken to render them more angular, so as to give a bet- ter key. Aggregates are broken by a crushing or stamp- ing machine. In Paris, the stone aggregates used for casting figures, vases and similar ornamental works is irenerally broken by hand. Aggregates should be clean, and their surfaces free from mud and dust. Coarse aggregates are easily (•leaned by turning on a strong stream of water from the liose. The aggregates should be laid on an inclined plane to allow the water and dirt to run off. The importance of a clean aggregate is seen from the fact that briquettes made from washed particles resist a tensile strain from 15 to 20 per cent, higher than those made from unwashed particles, when tested iiiidtT similar conditions. HOW TO USE THEM 29S Porous Aggregates. — All aggregates of a porous na- ture or having a great suction should be well wetted before being gauged, to prevent absorption of the water used for gauging the matrix. A porous aggregate re- - erites are imperative, gravel and coke-breeze as aggre- gates stand lowest in the scale. Owing to their abun- dance and cheapness, however, or for want of better ma- terials, their use is often unavoidable. Their individual defects may be partly if not wholly corrected by a com- bination of two or more aggregates so as to balance their respective good and bad qualities. It is self-evident that the hard, non-porous, and incombustible nature of gravel will correct the soft, porous, and combustible nature of HOW TO USK THEM 297 coke-breeze, and that the light, rough, angular, and elas- tic nature and variety of size of coke-breeze will counter- balance the disadvantages of the heavy, smooth, round, and rigid nature and uniformity of size of gravel. The strength, irregularity of size, and form of broken bricks and its incombustible nature, causes it to be a diiTct gain to either of the above. The mixing of various aggre- gates may seem of small importance, but if by their judi- cious amalgamation the strength is enhanced, or the weight or cost of the material decreased, or gained, if the practice enables any waste or by-product to be utilized, then the advantage becomes obvious. To argue by analogy, it is well known that it is by the judicious com- bination and manipulation of various materials that mortars and cements attain their strength and hardness, therefore the same course will give equally good results with concretes, while rendering economy with safety pos- sible. The compressive and tensile strength of concrete is influenced both by the matrix and the aggregate. Aggro- gates which are uniform in size (or if of various sizes which are not graduated in proportion to each other), or having their surfaces spherical, soft or dirty, will not bind with the matrix, or key or bend with each other, so well as those which are of various graduating projxir- tional sizes, and have their surfaces hard, angular and clean. Sand and Cement. — Sand is extensively used as an aggregate in Portland cement for cast work, mouldings, and wall plastering. Fine sand does not give so good results for strength as coarse sand, and a hard-grained sand is more durable than a soft one. Ground brick- bats or pottery, .sandstone and flints, fine gravel, smithy '•U,'!' |H ''^11 » i \ *^ ! I. i,:sii iiu 298 CEMENTS AND CONCRETES i li ashes, and coke-breezo are often used as substitutes for sand. It has generally been assumed that sharp coarse sand is one of the best and strongest for gauging with cement, but, according to experiments made by Mr. Grant, clean .sharp pit sand gives better results, as he found that Avhereas test briquettes having a sectional area of 2Vo superficial inches, composed of equal proportions of coarse sand, broke at the end of twelve months with a tensile strain of 724 lbs., it required 815 lbs. to break briquettes composed of equal parts of cement and pit sand. With reference to various sands suitable for mak- ing mortar with cement, Mr. Grant's experiment is of a most surprising nature, as it indicates that sand made from gro'iie clay ballast, or ground brick — which are identical — aad Portland stone dust, were superior to pit or sea sand, or smiths' ashes. The following sliows the results of tests of various aggregates made by Lieutenant Innes. The briquettes are composed of Portland cement, sand, or other aggre- gates, in the proportions of 1 to 2, and were kept in water for seven days. It will be seen that Portland stone dust gave the best results, and the others follow in this order — coarse sea sand, rough pit sand, smooth pit sand, drifted sea sand, and lastly smithy ashes. If *' ist had been elimi- nated, the tests would be more vtuuable. The degree of coarseness has a considerable influence on the strength of the concrete and mortar. Fire sand makes weaker mortar than coarse. The following table gives the re- sults of two series of tests carried out by Mr. Grant. The cement was sifted through a sieve with 2,580 meshes to the square inch, and was made into briquettes with 2 HOW TO USE THEM 299 H U a o o S O A «■» 1 ^ i <-• eo « 00 lO (D i g s s $ s a 1 £ «* |i 1 5 § 5 9 lO ^ ^ ^ 2 ^s lO 04 rH Q 4 rH C 5 l« •^ > a ec ^ « •^ • ■'t • • a" b • p* § -a P : ■*> . e i S3 a> Qj •k a u C 1 c 9 o 09 a a'- a 1 8 . -3)3 3 8 GO go .- •2 s a 1 ■ S : g be ■s" 9 -3 .S.CJ is i a 1 1 n cB a; . "3 B eg o; CO a i ; 302 CEMENTS AND CONCRETES be broken small, or used for internal layers of concrete. The bricks should also be paased through a y^ inch sieve. The finer the breeze and brick, the better for receiving and retaining nails. Voids in Aggregates. — The quantity of voids or in- terstices depends on the shape and size of the aggregates. The least quantity of voids will be found in those aggre- gates which are broken small, and contain pieces of va- rious sizes. Gravel free from sand contains about 30 per cent, of voids, and broken stone of uniform size about 50 per cent. Sand is often mixed with gravel, stones, &c., to lessen the quantity, or fill the voids, so as to en- sure the full strength of the concrete, without adding more cement than the proper ratio. The following method is used to ascertain the voids in aggregates: — Fill a box of known capacity with damp, broken aggre- gate ; start shaking it during the operation ; then fill the box to the brim with water ; the quantity of water is the measure of the voids in the a^regate. Having now briefly reviewed the characteristics of the agp^-egates most used, the practical conclusions to be drawn are that they should be angular in form, hard in natui«, grad- uated in size, and clean. Crushing Strength of Concrete. — The crushing strength of concrete depends upon the ratio of cement, and the nature of the aggregate. Another important factor is compression, done by heating and ramming. Compression increases the weight of concrete about 4 per cent., and the strength about 25 per cent. The follow- ing table shows the crushing strength of concrete made with Portland cement and ■»' rious kinds of aggregates as given by Mr. Grant. The tests Wci-e made with 6-inch cubes. One-half were compressed by heating the con- crete into the mould with a mallet ; the other half were HOW TO USE THEM 303 not compressed. The whole were kept in the air for a year before being crushed. The granite and slag might have been expected to have given the better results. It is probable that they were unwashed^ and contained a considerable amount of dust. If the compression was done by hydraulic power, so as to obtain a uniform compression in all the cubes, the results would be more reliable. i Cbushinq Strength (in Tons per Square Foot) op Portland Cement Concretes Havinq Various Aggregates. Nature of Af- Kregate. six to One. Eight to One. Ten to One. Com- prewed. Not Com- pressed. Com- pressed. Not Com- pressed. Com- pressed. Not Com- pressed. Ballast Portland stone Granite Pottery Slag Flints 81.6 162.4 122. 115.2 92. 82. 72.8 120. 98. 98.4 80. 62. 54. 182. 78.4 88. 78. 70. 50. 98. 68. 72. 56. 66. 42. 88. 62. 74. 42. 60. 82. 76. 46. 66. 34. 51.2 Water for Concrete. — Water for concrete should be perfectly clean, and free from organic and inorganic impurities. As regards the quantity, it can only be said that for such purposes as the foundations for pav- ing, casting blocks, &c., or where the material can be well rammed, so as to insure perfect consolidation, less is required than where the concrete can only be poured or laid in position. When mixed with sufficient water, the concrete occupies about one-eijrhth more space than when m mi 304 CEMENTS AND CONCRETES mixed with the full (luantity, and percolation through the former gauge would be greater than through the lat- ter. Yet by thoroujili ramming the former would oc- cupy less space and offer gri'ater resistance to moisture. An over-watered gauge is slow to set, difficult to work, liable to surface cracks, and often there is a loss of strength, caused by escape of a portion of liquid cement. The work will also be unequal in strength, owing to the liquid cement flowing to various or lov/er parts, leaving parts of the aggregate bare and weak. It must not be inferred from the foregoing remarks that water is entirely unnecessary or of little value for concrete. On the contrary, it is of the utmost value. Tne evil is in the abuse, not in the use. Portland ce- ment has a great affinity for moisture. For instance, if a sack of cement is left on or in a damp place, a part of the contents soon becomes set and extremely hard, which is a proof of its affinity, and that moisture alone will set cement without water, far less excess of water. Fresh cement requires more water than stale cement. Cement gauged with sea water sets more slowly than with fresh water. Sea water should not be used in concrete in- tended for paving stables, chemical tanks, or similar places where it will come m contact with ammonia. Sea water having a lower freezing-point than fresh water, is sometimes used in frosty weather to allow the work to be carried on. It ought not, however, to be used for ex- ternal work, especially for plastering facade as it has the property of attracting moisture and causing an ef- florescence on the surface. Sometimes in frosty weather hot water, also hot lime, is used for concrete; but al- though these hasten the setting and hardening of con. erete, they also wash away some of the finest and best particles of the cement during the gauging. A part of now TO USE THEM 305 the vater also forms in little globules throughout the mans, and when the water-drops evaporate a series of small holes or bulbs ure left, which deteriorate the strength of the concrete. Finally, it may be stated that the quantity of water re«iuired for gauging concrete is regulated by the class and condition of the aggregate, by the state of the atmosphere, and by the purpose for which the concrete is required. Another important point is the careful and thorough incorporation of all the ma- terials when gauging. A mass of raw materials, if gauged carelessly, will require more water to attain the hume plasticity than that which is carefully gauged. Ap- proximate quantities of water are given for Portland cement plastering. For conciete the quantity is about 21 gallons of water to 1 cubic yard of dry materials, or about 1 part by volume to 8 parts. It is a good maxim to bear in mind when mixing water for concrete, that other things being equal, the minimum is better than the maximum. Water may be said to give birth to the strength of cement ; to carry the simile further, the ag- gregate may be termed the bone, the matrix the skin and sinew, and the water the blood of concrete. Gauging Concntc. — It is a common idea that concrete can be gauged and u«;ed anyhow, with any ag^egate, or with any amount of water ; and in consequence of a lax- ity in supervision in the selection of the materials, and their correct gauging and manipulation, unsatisfactory results are sometimes arrived at, the blame being at- tributed to the wrong cause. Gauging concrete re- quires considerable care to avoid waste of the materials and obtain the best possible work. Concrete can b« gauged either by hiind or by machinery. For small quantities, such as for stairs and similar work, the former is almost invariably used; and for large quan- m\ ill ' 306 CEMENTS AND CONCRETES titles, such OH for foundation or buildings, &c., the lat- ter beinj? more economical, is preferable. A careful and uniform method should be employed for hard gauginK; nothing should be left to chance or rule of thumb. The gauge-board should be sufficiently large to allow the materials to be turned over without spilling, it should be placed as near the work as possible, ana it should be cleaned after each gauge. For fine concrete, no more than 1 ouhie yard should bo gauged at a time. This is as mu.h :is thiv men can properly gauge at once and in the proper time— that is, before the "initial set" begins. Portland cement con- crete, unlike some mortars, does not improve by pro- h.nged working. If larger quantities are desirabh'. then more men must be employed in the gauging. All ma- terials should be measured for each gauge, to ensure uni- form setting and .strength, and also the best work. This, combined with the saving of time and materials, will re- pay a hundreilfold the cost of the measures. It is a common yet a wrong way, when gauging for paving pur- poses, to measure the aggregate by so many barrowfula to a sack of cement. Neither the aggregate nor the ce- ment can be accurately measured in this haphazard way. No man fills a barrow twice alike, and the cement being turned ont ol' 1ht> sat'ks direct onto the aggregate is apt to vary, as it may contain lumps caused by damp, and very often some of the finest ('cuient is retained in the sack, as more bften than not it is simply drawn up and then thrown on one side without shaking it, as would be, or at least should be done if the cement was emptied for air-shaking. The aggregate should be measured in a bottomless box or frame with handles at the ends, the cement in a box (with a bottom), and the water in a gallon metal measure or a pail made to contain 4 gal- HOW TO USE THEM 307 Ions. Five pailfuk of this size are about sufHcient to gauge 1 cubic yard where the conen'te can be well rammed or punned. For work that is simply laid, 1 gal- loil extra is required. The box frame is laid on the gauge-board and filled with aggregate (in a damp state). The frame is lifted oflf, and the aggregate spread over the board until about 6 or 7 inches thick. The cement is then distributed ove" the ag{?regate. The materials are then gauged by three men, two with shovels, and one with a rake or larry, the former facing the latter. The dry materials should be carefully but energetically turned over twice or even thi , and then when being turned over the third time \.'at./ must be gradually ad- ded by means of a rose fixed on a waver-can. Water poured from a pail is apt to wash parts of the cement away ; the water also cannot be regularly and gradually distributed over the dry materials as when a rose is used. The mass is again turned over twice or evea thrice, until thoroughly incorporated. This turning over does not consist of merely turning the mass over in the centre or on one place o£ the board, but to be effectively done a shoveller should stand at each side of the board, and the raker at the end to which the mass is to be first turned ; the shovellers lift the stuff and spread or rather scatter it on one end of the board with a jerking mo- tion, and the raker further mixes the stuff by working each shovelful backwards and forwards. This is repeat- ed, the stuff being turned to the other end of the board, after which it is turned to the center, the water being added as ah-eady described. The wet mass is then turned over twice in a similar manner, and finally finished in the centre of the board. The shovellers in the final mix- ing turn the stuff from the outside of the heap to the centre, while the raker gives the final touches. After m -It? ' r if ' ill 308 CEMENTS AND CONCRETES being gauged, it should not be disturbed, but immediatei ly shovelled into pails, and conveyed to the place of its use. The "initial sev" begins nearly or as soon as gauged, and any after or unnecessary disturbance tends to de- stroy the setting properties of the cement. The practice of gauging, and afterwards regauging or knocking it up, is most objectionable, as it destroys its setting properties. No more should be gauged at one time than can be con- veniently laid in one operation. The gauging of this valuable material should not be left entirely to unskilled labor, but ought to be carried out under careful super- vision. Ramming Concrete.— The ramming, beating, or pun- ning of concrete is of great importance. It compresses the concrete, rendering it more dense and free from voids, and forces out all superfluous water. The re- sultant gain in strength, durability, and imperviousness is by no means to be despised. Without compression it is impossible to obtain impervious concrete. Prolonged ramming, however, is dangerous, as it may be contin- ued until the cement is set, which would be a direct loss of strength. For this reason, the ramming of concrete made with quick-setting cement should immediately fol- " low the deposition of the material, and be expeditiously done. The concrete should always be gauged rather stiff than soft. If in the latter form, the ramming will separate the more fluid portions, and produce strata of different densities. When the concrete is deposited in layers, the joints of each layer, if dry or exposed, should be well swept and watered before the next layer is de- posited. It is often advisable, especially in very dry work, to brush the joints with liquid cement after they have been swept and wetted. For larger constructional work, the joints should also be keyed by aid of a pick, or HOW TO USE THEM 309 by inserting stones at intervals into the concrete before it is set, leaving them projecting 3 or 4 inches above the level of the joint. Another method of forming a key is effected by forcing a batten on edge about 2 or 3 inches deep into the concrete, at the middle of the joint, and when the concrete is firm or nearly set the batten is ex- tracted, thus leaving a groove which forms a key for the succeeding layer. No layer that has to be left for some time, or until dry, should be less than 4 inches deep. Thin layers are always a source of weakness. If the successive layers can be laid before the previous one is firm or set, the thickness is not of so much consequence. For large work, when each layer has to stand until set, the thick- ness may vary from 9 to 12 or even 18 inches. Ram- ming may be done by using an iron punner, or one made of hardwood and bound with iron. Wooden mallets and punchers or iron hand-floats are most suitable for ramming stairs and cast work. The gain in strength is shown in the table of the crushing strength of Port- land cement concrete. Thickness of Concrete Paving.— The thickness of con- crete paving laid in situ is regulated according to the purpose and the position of the work. The thickness al- so depends upon the nature and solidity of the founda- tions. It is obvious that a thicker paving is required for a foundation that is weak or soft than for one that is strong and hard. The best foundations are those com- posed of strong and well-laid rough concrete. Founda- tions composed of broken bricks or stone thoroughly con- solidated by ramming are the next best. The thickness of foundations is also regulated by the nature of the soil and the subsequent traffic. Paving for the sidewalks oi mam streets, or where the traffic is heavy and con- i . ml i Hi li 310 CEMENTS AND CONCRETES tinuous, should not be less than 2 inches. For a medium traffic, and on a strong foundation, a thickness of IV^ inches will be sufficient. For side streets, garden paths, ^jBSsages in houses, or similar places where the traffic is : :ght and limited, a thickness from 1 to 11/2 inches will t . ample if on a rough concrete foundation ; but if on a ■(i'xy "dry," that is, broken brick or stone one, the thick- -jess should not be less than 11/2 inches. The thickness for stable floors may vary from 3 to i inches, according to the class of horses. For instance, a thickness of 3 inches would be ample for race or carriage horses, but 4 inches is necessary for heavy cart horses. The same rule applies to yards, a thickness of 3 or 31/2 inches being sufficient for carriages, while 4 inches is required for carts, wagons, &c. Factory floors are generally made 2 inches thick, but where there is machinery or wheel traffic a thickness from 2V2 to 3 inches is employed. By computing the volume and nature of the traffic, and comparing the tests of concrete paving given herein, the requisite thickness will be readily obtained. It must of necessity greatly depend on the class of the materials and manipulation used for the paving. Like most other articles, a good material will go further and last longer than a bad one. Concrete Paving. — Good pavements proclaim a city'» l>rogress. Isodorus states that the Carthaginians wer© the first people to pave streets. The subject of paving and floors will be best understood by dividing it into two parts — namely, paving, which is a floor surface laid and resting on solid ground ; and floors, by which are meant floors over voids. The following items briefly embody the processes Used for most concrete pavings now in use. Paving in situ is either laid in "one coat" or "two coats," the latter being in more general use than HO^ TO USE THEM 311 the former, yet each method has its individual merits. One-coat work is not so liable to rise or laminate as two- coat work. It takes slightly less labor, the whole thick- ness being laid in one operation. The aggregate is either granite or slag, or both in equal proportions, [gauged with Portland cement in the proportion of 2 of the latter to 5 of the former. Two-coat is laid with two different aggregates and gauges. The first coat has a cheap aggregate, such as ballast, clinkers, bricks, or whinstone, broken bo that they will pass through a 1 inch mesh riddle, and gauged in the ratio of 1 of Port- land cement to 5 of the aggregate. It is laid till within 1 inch of the finished surface. The second coat is laid Hs soon as the first is set, and is composed of 1 part of Portland to 2 of the aggregate, the latter being either crushed granite, slag, limestone, or whinstone that will pass through a 3-16 sieve. In some districts fine shingle is used for the topping aggregate. Quick-setting solutions are used to reduce the time re- quired to allow the paving to harden before it is avail- able for traffic. Many pavements are ruined by being used before having become sufficiently hard and set. r^Iany of the so-called quick-setting materials have the desired effect of setting the concrete quickly, but the work in many cases is none the better for these solutions. On no account should these quick-setting materials be used, unless thoroughy tested and the concrete proved durable by use and time. In order to protect the sur- face and allow the paving to be used immediately, P. M. Bruner, an American engineer and concrete specialist, <'ovprs the surface of the pavement directly it is finished with a thin coat of plaster or Parian cem«nt, which ad- mits of walking upon in a few hours, and resists pedes- i/m\ \i i ! ■ i, i ■it t! m 312 CEMENTS AND CONCRETES n ' i* ♦,rian trafiSc until the surface proper is sufficiently hard, ifter which it is shelled off with a trowel. Eureka Paving. — This is the name for an improved concrete, which has been extensively used with f?ood ii-- sults for many purposes, such as pavements, floors and stairs. Eureka, if not exactly one-coat work, is neaicr that than two-coat work, and may be said to be the happy medium, or a combination of both. Eureka is laid in iwo layers. The first is termed the "rouf>h coat," and the second the "fine coat" or "topping. " The topping is laid nearly as soon as the rough coat is laid, just as in rendering or dubbing-out plaster work. The materials and gauges are nearly alike for both layers. The gauged rough stuff is laid on the founda- tion, previously wetted to prevent suction, and spread and beaten with an iron hand-float. The laying, spread- ing and beating is continued until the rough surface is within l^ inch of the finished line. The surface of the rough coat is made fair, and a uniform thickness for the topping is obtained by passing a "gauge-rule" across the surface. A uniform thickness of topping gives an equal expansion, therefore the surface is not liable to crack. The suction is also more regular, which permits of the trowelling to be done with greater free- dom, and without causing hard ana soft places on the surface. As many alternate bays are laid as will allow of all being topped and finished the same day. When the number of bays to be laid in on one day has been de- cided, and the last one roughened in, the first bay will be firm to receive the topping. The topping is laid and .spread with a wooden hand-float, ruled and trowelled and brushed as afterwards described in the general pro- cess. This method of laying a i)art of the thickness ot HOW TO USE THEM 313 the paving, gauging stiff and bpating the mass, forces it into the interstices of the broken dry foundation, and not only consolidates the foundation and the rough coat, but also forms a solid bed to receive the topping. The topping goes in sooner and more regularly on a stiff- gauged and well-beaten coat than on a soft-gauged one, or than if the whole thickness of the paving were laid in one coat. Eureka Aggregate.— The method of preparing the ag- gregate for Eureka is of the utmost importance. The labor expended on its preparation is more than repaid, not only in the ease and rapidity when finishing, but also in the satisfaction of doing a strong and workmanlike job. Slag and granite is far more preferable to gravel or stone as an aggregate. Slag and granite in equal proportions have been used with good results. The size ordered from the furnace or quarry should be % inch screenings. It must be washed through a Vs inch sieve in a tub or iron tank. The coarse part rejected by the sieve to be laid aside for the rough coat. The fine ag- gregate is then washed again through a fine sieve to ex- tract any mud or impalpable powder, as the presence of such impurities weakens the consolidating power of the cement, and decreases the ultimate strength of the con- crete. This fine aggregate for the topping should be angular and of various graduating sizes, from that of fine sharp sand to the largest size that has passed through the Ys inch sieve. It has been proved by experience and the test of time that an artificial stone made with a fine a^regate has not only more resemblance to the grain or texture of natural stone, but is also denser, and wears better and with more uniformity, than one made with a large, round, or equal-sized aggregate. The use of small and angular aggregate of the graduating sizes ensures 1 -Si ;> ■ 'fm ! ,; •: . it ; ' f ; 1 { : i^i'. J 5 ' m :LM It 314 CEMENTS AND CONCRETES their fitting closer and interlocking together, thus form- ing a stronger bond, giving a regular key and freedom for each separate , piece to be coated with cement, the whole forming a solid and homogeneous body with a hard surface. Concrete with large or round aggregate, and the various pieces disproportionate in size to each other, will fit loosely and unevenly, and only touch at their most prominent points, thus leaving voids, and con- sequently unsound work. The voids may perchance be wholly or partly filled with matrix, still this is an un- necessar waste of cement. Consequently, concrete pav- ing having large or round aggregate wears unevenly, and leaves the large or round pieces uncoated and loose, or so exposed above the surface that they soon get dis- lodged, leaving a series of small holes, which sooner or later wear larger and larger. Another point of import- ance is that concrete with a fine hard aggregate is more plastic, works freer, and has a greater compressive strength than concrete with a large or soft aggregate. Eureka concrete, having a fine, clean, and regulated ag- gregate, should be used for the topping of paving, steps, landings, or for any class of work exposed to friction or wear. It is well to remember that a good matrix will not make a bad aggregate strong, although a bad ag- gregate will make a good matrix weak, or rather the re- sultant concrete weak. Eureka Quantities. — The quantities for the rough coat are 1 part of Portland cement and 4 parts of the coarse portion of Eureka aggregate. These materials must be gauged stiflf, only as much water being used as will allow the mass to be thoroughly mixed and plastic. The quantities for the toppinp: are 2 parts of Portland cement to 5 of the fine ajijircsate, and gauged about the consistency of well-temperod "coarse stuff," as used for HOW TO USE THEM 815 floating. Experiments prove that neat cement is infe- rior in wear-resisting qualities (such as frictional wear and pedestrian traffic) to mixture of cement with sand or other aggregate, being in fact equal to a mixture of about 1 part of cement to 3 parts of aggregate. The l)est wearing qualities are obtained by a mixture of 2 l)arts of cement to 3 of aggregate. Levels and Falls.— Accurate levelling and adjustment of the requisite falls are important features for pave- ments and tiooring. Levelling is the art by which the rel- ative heights of any number of points are determined. FhIIs are used to allow rain and water used for cleansing purposes to run off into channels and drains. The levels jind falls in good buildings are generally marked, on the n in aucci^ssive short and quick strokes. If the stuff i8 soft and laid too full, the rule is worked loosely on edge with a zigzag motion, so as to draw the excess Htuff and water oflf the surface, and leave the body full and regular. If there arc any hollow places, they are filled up with stuff, and the rule again applied. In all rases the surface should be finally straightened by beat- ing with the rule. This process leaves the surface more uniform, straight, and solid than by dragging or working the rule. Trowelling Concrete. — After being ruled, and when isliKhtly firm, the surface is beaten with a wood hand- Hoat, which lays any irregular parts or projecting pieces of aggregate. The beating or patting is continxied until the "fat" appears on the surface. It is then trowelled, or rather ironed, the trowel being worked on the flat of Die blade with a circular motion. The plasteri'r, when trowelling off, should iiave a liaiid-float in the other luiniervals \\K.\ water. If the sun's rays are hot, the s al" tfo i>f i e work while in progress should be protected by exte^>ding tarpaulin or sail-cloths above the parts being laid. Concrete surfaces are further hardened by Hooding with v.ater, or where this is not practical, covering with wet saw-dust or sand as soon as set. Care must be taken that the saw-dust is clean and of a light color, as otherwise it will stain the work. Non-Slippery Pavements. — Concrete pavements for special purposes are rendered non-slippery by mixing % inch lead cubes with the topping stuff. Lead cubes about Y2 inch square laid by hand from 1 inch to 4 inches apart in the moist concrete surface, have been used for rendering concrete surfaces non-slippery. Iron and brass filings are also used for the same purpose, and also for increasing the wear-resisting of concrete surface. Roughened, indented, grooved, and matted surfaces are also used to obtain a better foot-hold on concrete sur- faces. Grooved and Roughened Surfaces. — Stables, yards, &c., are grooved and channeled on the surfaces to pre- vent animals from slipping, and also to carry off urine or other liquids to the traps or gulleys. Indented sur- faces are useful on steep gradient to give a better foot, hold. Grooves are made with a special wood or iron tool, which is beaten into the surface as soon as the con- crete is floated. The grooves for stables are generally made about 5 inches from centre to centre, and the depth about % inch. A line is first made at the one end of th^ work, and the groover is then laid on this line, and beat- t-- (■ ! . a I I ,u' ■•.f..irlv .1 f ;riHf P.lyf r 324 CEMENTS AND CONCRETES en down with a hammer to the desired depth. Before it is taken oflf, a parallel rule is laid on the surface and against the groover, which is then taken up and laid ck)se to the other side of the parallel rule, and beaten in as before, and so on until the whole surface is done. The width of the parallel rule is equal to the dasired width between the grooves, less the width of the groover. Grooves, however long, can be made by moving the tool along, and against a long parallel rule. After stretch of grooves have been sunk, the surface is trowelled, and the indentations made true. It may be necessary to apply the groover again, and beat or work it forward and back- ward and further regulate their depth and straightness. They are then made smooth with a gauging trowel and finished with adampbrush,thesidesof the grooves being left smooth to give a free pass; ge for liquids. Grooves on a surface having a fall should radiate to- ward the deepest point. A level surface may be made to carry off the water by the indentation being formed wider and deeper towards the outlet. Street and other pavements are sometimes indented with metal rollers to give a better foot-hold. Platforms and other surfaces are sometimes made rough or indented by beating the moist concrete, with a "stampiiig-tiuat." The sole has a series of squares projecting about % inch, each square about 1 inch, and a half inch apart. Concrete surfaces are al- so roughened or matted by dabbing the surface as soon as trowelled with a coarse ^tiff whale-bone brush. Illus- tration No. 2 shows three designs of grooved surfaces for carriage drives, conservatories, &c. A plain border, or one with a single width of the main design, is generally formed on the sides and ends of the floor. A rough mat- i *1 HOW TO USE THEM 325 ted sflrface may also be obtained by pressing or beating a wet coarse sack or matting over the moist concrete. Stamped Concrete. — Various materials and methods are used for stamping or indenting concrete surfaces to obtain a better foot-hold, or to form any desired pattern. Iron stamps are generally used, but owing to their weight and rigid nature, ire unsuitable for large sec- Fig. I. Fig. I. Fig. 3. Se.U •fjttt. Tu&ES Examples of Grooved Surface-s. NO. 2. tions. Plaster stamps ar e sometimes used for temporary purposes, or for small sections and quantities, Stami)s for large concrete surfaces should be composed of a ma- terial that is easily made to the desired form durable and slightly flexible. Expansion Joints. — Compressive or flexible joints ai-e used to allow for any expansion or contraction that may take place in a large area of concrete exposed to atmos- pheric changes. There are various methods in use for .|U il f i ill 1 1 ^ r IJ >■• I' . hi ):'■'? I' I :, 11; ■ 5- HiJ ? 1 ■ I ! ' I :vi I \ 826 CEMENTS AND CONCRETES 'ii the purpose. The first is to set out the area in small sections, and to lay them in alternate or isolated bays, thus giving time for their expansion before the inter- mediate bays are laid. This method, by dividing the area into small sections, is the best for preventing cracks, because small sections are stronger than large ones ; and in the event of any subsidence in the foundation, the surface fissures are limited to the immediate joints of the section. Contraction and expansion is also less in small bodies than in larger ones. Another method of forming joints is by cutting with a wide chisel or a cutting tool before the rough concrete is set, a corresponding joint being cut in the fine concrete topping. False joints are made by indenting the top- ping after it is trowelled. A metal roller is used for finishing true joints and forming false joints. Frame strong enough to resist the expansion of the concrete would not only increase the density and strength of concrete paving and blocks, but also effectually prevent its cracking. Another method for forming sections in large sur- faces of pavement of floors to prevent cracks is effected thus: — first set out the size of proposed sections on the rough or first coat, then with a straight-edge, a wide chisel, or a cutting tool and a hammer, cut through the rough coat, so as to divide it into sections as set out. This done, insert wood strips into the cutting, keeping their top edges about Vs inch below the screeds or rules which represent the finished surface. The strips are made from % to 1% inches wide, 3-16 inch thick, and in suitable lengths. The width is regulated according to the thickness of the paving. For instance, for two inch paving the widths should be 1% inches. This allows ti; ' HOW TO USE THEM 327 about Ys inches in the rough coat (with 14 inch play from the bottom), and about % iiich in the topping, and Vs inch for the upper thickness of the topping to cover the top edges of the strips. After the strips are inserted the rough coat is beaten up or made good to the sides of the strips, and then the topping is laid and trowelled in the usual way. The surface joints are then made direci> -Half Plan of Coach Yard, with Section through Centre. NO. 8. ly over the strips, with the aid of a straight edge, so as to form a clean and sharp joint. As already mentioned, these strips allow for any subsequent contraction or ex- pansion, thus avoiding zigzag cracks ; and in the event of repairs to underneath pipes, each section can be cut out and relaid separately without injury to the adjoining sections. This process of inserting strips in the rough coat, cutting nearly through the topping, gives the same results as if the strips were laid flush with the surface of the topping, with the advantages that the surface can be more readily trowelled, and is more pleasing to the m\ 1 >• k i. >^ ''if ir ' ■rl,;'. 'i; i 1'. * ■H .iF5 '4-1 . .'; *• ■. i •■ i -, 1 . i 1 \S> 82S CEMENTS AND CONCRETES n I rye, because the strips are not seen. A cutting tool is a blade of steel about 5 or 6 inches long and 4 inches wide, with a wood handle at one end. The section of the blade is well tapered, so as to obtain a sharp cutting edge, and form a wide top edge to offer a broad surface for the hammer while being beaten. Washing Yards.*— Eureka concrete being of a hard nature, and having a close and smooth surface, is well adapted as a flooring for all washing or cleaning pur- poses. The surface being smooth, it can in turn be read- ily cleaned. Illustration No. 3 shows the half plan of washing yard for Avashing carriages, &c. Stable Pavements.— The paving for stables, and other places for keeping animals, should be jointless, non-ab- sorbent, hard, and durable. Such paving must not be slippery, yot smooth enough to be easily washed, the whole laid to falls, and grooved to give an easy and ready passage for liquid manure and water when being washed. No material can so fully meet these require- ments as a well-made and well-laid concrete. Granite sets are hard, but slippery. Bricks are too absorbent; the urine percolates between the joints and generates ammonia and other effluvia which are detrimental to the health of the animals. (See Nos. 4 and 5.) Stables are generally laid with a fall toward the main channel. The amount of fall varies according to ideas of the horse owners. The fall adopted by the War office is 1 in 80 from the top of the manger to the main channel, and 1 to 36 from each side of the stall to the centre groove. The width of the main channels is u. ually set out with screed rules, which also act as screeds to work from. Channels are generally formed after the other surface is finished. Sometimes templates are fixed on the bed ot HOW TO USE THEM 329 the channels, and the space filled in and ruled off wit^' a straight-edge while the whole surface is being formod. The thickness of stable paving varies from 2 to 314 inches, according tj the class of horse. The thickness of the stalls is often decreased toward the manger. The most useful length is 2 feet 6 inches. They can be cut with a chisel as easy as cutting stone. Special slabs can be made for circular work, also with rebated sinking for metal plates, to cover coal-holes, drains, gas and water taps, &c. Concrete paving slabs are laid in precisely the same way as natural stone. f-*--^*'-4 , i^^^^r*^'***' '^^c^^ ■ ^ ^~ . vi^- Stctian. 9f datmel «} 3 jZkitnt..^ ^inn araU SttHan y etnlttftuvn 2> -Sections of th« vAtious Parts op th ". SxABtt Floors SHOWN ON Illustration NO. 4. NO. 6. Concrete Slab Moulds. — Slab moulds are made with 11/^ inch boards ledged together. On this ground, wood sides and ends (each being 2i/^ inches by 2 inches, or 3 inches by 3 inches, according to the desired thickness ol slab) are fixed. One side and end is keld in position with thumb screws, which fit into iron sockets, so that, they can be unscrewed to relieve the slab when set. Th(f bottom and the sides and ends are lined with strong irou or zinc places. ill IP :ri' hi! I 'r« !!■! 330 CEMENTS AND CONCRETES Slab Making.— Slaha are mostly made by machinery. The materials are 1 part of Portland cement mixed ary with 21/2 parts of crushed granite and slag in equal pro- portions that have been washed and passed through a Vi inch sieve. They are thoroughly incorporated together in a horizontal cylinder worked by machinery, a mini- mum of water being added, and the mixing continued until the mass is well gauged. The mould, which has been previously oiled, is placed on a shaking mavjhine known as a "trembler" or "dither," which gives a rapid vertical jolting motion to the mould and its contents. A small portion of "slip," that is, neat cement, is laid round the angles. The machine is then started, and the concrete laid on the mould by small shovelfuls at a time, a man with a trowel spreading it over the mould until full. The surface is then ruled off. If both sides of the slabs are required for use, the upper surface is trowelled. The whole operation of mixing, filling in, and ruling off takes about seven minutes. The filled moulds are re- moved and allowed to stand for about three days. The slabs are then taken out, and stacked on edge and air- dried for about five days. They are then immersed in it silicate bath for about seven days, and are afterwards taken out and stacked in the open air until it is required lor use. They should not be used until three months old. Paving slabs are also made by hand, by ramming and beating the moist concrete into the mould with an iron hand-float. Powerful ramiriing, trituration, or vio- lent agitation of the gauged material in the mould, tend to consolidate concrete, and it is possible to further in- crease homogeneity by the use of hydraulic pressure. Induration Concrete Slabs. — The surface of concrete Blabs or other work exposed to friction or wear may be HOW TO USE THEM 331 hardened by soaliing in a silicate solution. Silicate of soda has u ^rreat affinity for the materials of which con- crete is composed, and by induration cauaes the surface to become hard, dense, and non-porous. The silicate of soda and potash is known as soluble 5,'la.ss or dissolved flint. The soluble silicate is a clear viscous substance made from pure flint and caustic soda, which is digested by heat under pressure indigester. Its strength is technically known as 140 degrees, which shows 1,700 on a hygrometer. When used as a bath for concrete, it is diluted with water, the proportion vary- ing from 6 to 10 parts of water to one of silicate. Con- crete pavements, laid in situ, may also be hardened by washing with silicate solution. They should not be sili- cated until two days after being laid, to allow the mois- ture to evaporate and the silicate to penetrate. Mosaic. — The art of making mosaic is at the present time scarcely within the province of plasterers, but in former times many kinds were made in situ or in slabs by plasterers. The subdivision of labor has to a great e.Ktent caused mosaii making to be confined to special- ists. Concrete is still made by plasterers. A brief de- scription of this and other kinds may prove useful as well as interesting, especially to plasterers who are in the habit of fixing tiles and working in concrete. Mosaic is the art of producing geometrical, floral, or figured de- signs, by the joining together of hard stones, marbles, earthenware, glass, or artificial stone, either naturally or artificially colored. The term "mosaic" embraces a wide range of artistic processes and materials for the decoration of floors, walls, ceilings. The Egyptians were experts in mosaic. The Cairo worker as a rule bad no drawings made beforehand, but the mosaic design was : I l\} H ■■ ■ ■( i i; I ;,ik': .It t, f'l .ra' 1 ■1\ 332 CEMENTS AND CONCRETES * i' ; i.' constructed by tho artist as h< arranjred the pieces on the groand. The mosaic pavements of Cairo arc of a slightly different character from those used for wall decoration, and are generally composed entirely of mar- ble tesserae (and sometimes red earthenware) of largii* size than the delicate pieces included in wall mosaics. They are arranged to form geometrical patterns within a space of about two feet square. Each square slab is made separately, and the pieces are set, not in plastei-, but in a competition of lime and clay impervious t<> water. The clay must be unbumt, just as it comes from the pit. Sarace/iic mosaic in Egypt is a combination of the tesselatcd nwthod with a large proportion of sectiK' mosaic. The K "tans also were great workers in mosaic. The mosaics oi Byzantium and Ravenna consisted of cubes of opaque and colored glass. The general method used here for pavement mosaic \* as follows : The repeated design is traced on stout paper and small pieces of marble, or more often tile, .ire gummed on the paper, following the design of form and color, one pifce at a time (with the smooth face down- •wards) being laid until the design is completed. The mosaic slabs, which are thus temporarily kept in posi- tion, are sent to the building and laid where intended. A rough concrete foundation, which has previously been made level, is then floated with Portland or Keen's cement, and the slabs with paper are then damped and drawn off, and any openings or defects filled up with small pieces of the same form and color as the design. The slabs are made in various sizes accordinsc to the de- sign. For instance, a border 12 inches wide may be made from 3 to 6 inches long. Wlien laying the slabs, it is best ^c begin at the centre and work outwards, and any ex- HOW TO USE THEM 333 cesa or deficiency taken oflf or made up in the pla'n part of the border at the walls. The tiles are made at pottery works in the required sizes and colors. The thicknesH is jronorally about Vi inch and the average surface size about Va inch. Females are often employed fixing the liieces on the paper. The designs of coats of arms, mono- grams, dates, figures, flowers, and foliage are effectively produced by this simple and cheap process. Concrete Mosaic. — All mosaics are more or less of a concretive nature, and the trade term of "concrete mo- saic" is due to the fact that the matrix used is Portland or other cement gauged with the marble aggregate, and laid in most cases in a similar manner as ordinary con- crete. Concrete mosaic is extensively used for paving halls, corridors, conservatories, terraces, &c. It is also used for constructing steps, landings, baths, pedestals, &c. Slabs and tiles made of this class of mosaic for paving purposes are slowly but surely proving a for- midable rival to Italian mosaic encaustic tiles. It can he made in larger sections, thus facilitating rapidity of laying. It is more accurate in form, durable, non-slip- perj-, and cheaper. The last reason alone is a favorable item in this keen age of competition. Whore marble has been scarce, broken tiles, pottery, colored glass, flints, white spar, &c., have been usud as aggregate. If the marble chips are obtainable as a waste, and near the place <»f manufacture, the primary cost is small. If the moulds ai'o of metal, and made in sections so as to form a series of moulds in one case, and the casts are pressed by means of a hydraulic power, the cost of production is reduced to a minimum. If the ca.sts are polished in large num- l)ers by machinery nti a rev(>lviiig table, the total cost is further reduced. For local purposes they can be made II -4; '|i ip T: •< iV\ ,M>^ i»i I \» the centre part. The screed rules are tfencraliy fixed with a j?auKe plaster, which is (piieker than fixin;,' on i,'auj,'(tl cement. After the centre is laid, the plaster should be carefully swept off, and the conereti- wi'll wetted before the border is laid. The marble and cement is Kau:4ed in the proportion of 2 of marble to 1 of cement, and laid flush with screeds, laying and beatinj? it in position with a long wood hand- float. The surface is ruled in from s'. When no house or shed is available for the purpose, a rough platform may be erected clear of the ground, on which the cement may be placed and so covered as to exclude water. When properly protected, it often improves with age. Cement is shipped in barrels or bags, the size and weight of Avliieh usually are given. Cement Mortar. — Cement mortal- is an intimate mix- ture of cement and sand mixed with sufficient water to produce a plastic mass. The amount of water will vary according to the proportion and condition of the sand, and had best be determined independently in each case. Sand is used both for the sake of economy and to avoid cracks due to shrinkage of cement in setting. Where great strength is required, th<'re should be at least suffi- cient cement to fill the voids or air spaces in the sand, and a slight excess is preferable in order to compensate for any uneven distribution in mixing. Common propor- tions for Portland eeniont mortar are 3 parts sand to 1 ^i II III ; 1 1 m m '6SB CEMENTS AND CONCRETES ii;- i I. of cement, and for natural cement mortar, 2 parts sand to 1 of cement. Unless otherwise stated, materials for mortar or concrete are considered to be proportioned by volume, the cement being slightly shaken in the measure used. A "lean" mortar is one having only a small propor- tion of cement, while a "rich" mixture is one with a large proportion of cement. "Neat" cement is pure cement, or that with no admixture of sand. The term "aggregate" is used to designate the coarse materials en- tering into concrete — usually gravel or crushed rock. The proportion in which the three elements enter into the mixture is usually expressed by three figures sepa- rated by dashes— as, for instance, 1-2-5, meaning 1 part cement, 2 parts sand, and 5 parts aggregate. In the great majority of cases cement mortar is subjected only to compression, and for this reason it would seem nat- ural that, in testing it, to determine its compressive strength. The tensile strength of cement mortar, how- ever, is usually determined, and from this its resistance to compression may be assumed to be from 8 to 12 times greater. A direct determination of the compressive strength is a less simple operation, for which reason the tensile test is in most cases accepted as indicating the strength of the cement. Mixing. — In mixing cement mortar it is best to use a platform of convenient size or a shallow box. First, de- posit the requisite amount of sand in a uniform layer, and on top of this spread the cement. These should be mixed dry with shovels or hoes, until the whole mass ex- hibits a uniform color. Next, form a crater of the dry mixture, and into this pour nearly the entire quantity of water required for the batch. Work the dry material f I HOW TO USE THEM 339 from the outside toward the centre, until all the water is taken up, then turn rapidly with shovels, adding watoi- at the same time by sprinkling until the desired consist- ency is attained. It is frequently specified that the mor- tar shall be turned a certain number of times, but a bet- ter practice for securing a uniform mixture is to watch the operation and judge by the eye when the mixing has been carried far enough. In brick masonry the mis- take is frequently made of mixing the mortar very wet and relying upon the bricks to absorb the excess of water. It is better, however, to wet the brick thoroughly and use a stiff mortar. Grmit.—The term "grout" is applied to mortar mixed with an excess of water, which gives about the consist- ency of cream. This material is often used to fill the voids in stone-masonry, and in brick work the inner por- tions of walls are frequently laid dry and grouted. The practice in either case is to be condemned, except where the conditions are unusual, as cement used in this way will never develop its full strength. Lime and Cement Mortar.— h. C. Sabin finds that in Portland cement mortar containing three parts sand to 1 of cement, 10 per cent, of the cement may be replaced by lime in the form of paste without diminishing the strength of the mortar, and at the same time rendering it more plastic. In the case of natural cement mortar, lime may be added to the extent of 20 to 25 per cent, of the cement with good results. The increased plasticity due to the addition of lime much facilitates the operation of laying bricks, and has caused lime and cement mortar to be largely used. * Cement Mortar for Plastering. — In plastering with cement, a few precautions must be observed to insure M I'" J .il 'i 3 I 340 CEMENTS AND CONCRETES 'i good and permanent results. The surface to receive the plaster should be rough, perfectly clean, and well satu- rated with water. A mortar very rich in cement is rather a drawback than otherwise on account of shrink- age cracks, which frequently appear. The mortar, con- sisting of two or three parts sand to one of cement, should be mixed with as little water as possible and well worked to produce plasticity. It is essential that the plaster be kept moist until it has thoroughly hardened. Materials for Making Concrete Sand. — In securing sand for mixing mortar or concrete, if it is possible to select from several varieties, that sand should be chosen which is composed of sharp, angular grains, varying in size from coarse to fine. Such sand is, however, not always obtainable, nor is it essential for good work. Any coarse-grained sand which is fairly clean will answer the purpose. If gravel, sticks, or leaves be present they should be removed by screening. The voids in sand vary from 30 to 40 i>er cent., according to the variation in size of grains. A sand with different-sized grains is to be preferred, because less cement is required to fill the voids. By mixing coarse and fine sand it is possible to reduce the voids considerably. It is customary to use the terms "river sand," "sea sand," or "pit sand," according to the source of the supply. River sand as a rule has rounded grains, but unless it contains an excess of clay or other impurities, it is suitable for general purposes. When river sand is of a light color and fine-grained it answers well for plaster- i Sea sand may contain the salts found in the ocean. The tendency of these salts to attract moisture makes it HOW TO USE THEM 341 advisable to wash sea sand before using it for plastering or other work which is to be kept perfectly dry. Pit sand for the most part will be found to have sharp, angular grains, which make it excellent for mor- tar or concrete work. Where clay appears in pockets it is necessary either to remove it, or else see that it is thoroughly mixed with the sand. The presence of clay in excess frequently makes it necessary to wash p't sand before it is suitable for use. The results of tests made in this laboratory would in- dicate that the presence of clay, even in considerable amounts, is a decided benefit to "lean" mortars, whereas it does not appreciably affect the strength of a rit'h mixture. Gravel. — It is important that gravel for use in con- crete should be clean, in order that the cement may prop- erly adhere to it, and form a strong and compact mass. As with sand, it is well to have the pieces vary in size, thereby reducing the voids to be filled with mortar. The voids in general range from 35 to 40 per cent. Crushed Stone. — The best stone for concrete \ k con- sists of angular pieces, varying in size and having a clean, rough surface. Some form of strong and durable rock is to be preferred, such as limestone, trap, or gran- ite. The total output of the crusher should be used be- low a maximum size, depending upon the nature of the work in hand. All material under % inch will act as so much sand and should be considered as such in propor- tioning the mixture. Precautions must be taken to in- sure a uniform distribution of the smaller pieces of stone, otherwise the concrete will have an excess of fine ma- terial in some parts and a deficiency in others. i, S 1^ Ijl j... = 1' ■'»s»j-i •it |cl| .Ml ' I IP!: . ], 'I , 1 '! ' |i 'I i I I ' ■' II :i| 342 CEMENTS AND CONCRETES Less than 8 per cent, of clay will probably not serU ously impair the strength of the concrete, provided the stones are not coated with it, and may even prove a benefit in the case of lean mixtures. The voids in crushed stone depend upon the shape and variation in size of pieces, rarely falling below 40 per cent., unless much fine material is present, and in some cases reaching 50 per cent. A mixture of stone and gravel in equal parts makes an excellent aggregate for concrete. Stone Versus Gravel. — It would appear from tests that crushed stone makes a somewhat stronger concrete than gravel, but the latter is very extensively used with uni- formly good results. This superiority of stone over gravel for concrete work is attributed to the fact that the angular pieces of stone interlock more thoroughly than do the rounded pebbles, and offer a rougher surface to the cement. A point in favor of gravel concrete is that it requires less tamping to produce a compact mass than in the case of crushed stone. Then, too, the proportion of voids in stone being usually greater than in gravel, means a slight increase in the cost of concrete. Cinders. — Cinders concrete is frequently used in con- nection with expanded metal and other forms of rein- forcement for floor construction, and for this purpose it is well adapted on account of its light weight. Its poros- ity makes it a poor conductor of heat and permits the driving of nails. Only hard and thoroughly burned cin- ders should be used, and the concrete must be mixed quite soft so as to require but little tamping and to avoid crushing the cinders. Cinder concrete is much weaker, both in tension and compression, than stone or gravel concrete, and for this reason admits only of light rein- forcement. i !i ■<' «» V 1 HOW TO USE THEM 343 Concrete. — General Discussion: Cement concrete is the product resulting from an intimate mixture of cement mortar with an aggregate of crushed stone, gravel, or similar material. The aggregate is crushed or screened to the proper size as determined from the char- acter of the work. In foundation work, stone or gravel 3 inches in size may be used to advantage, whereas in the case of moulded articles of small sectional area, such as fence posts, hollow building blocks, &c., it is best to use only such material as will pass a V^ inch screen. An ideal concrete, from the standpoint of economy, would be that in which all voids in the aggregate were com- pletely filled with sand, and all the voids in the sand completely filled with cement, without any excess. Un- der these conditions there would be a thoroughly com- pact mass and no waste of materials. It is a simple matter to determine the voids in sand and also in the aggregate, but in mixing concrete the proportions vary a great deal, depending in each case upon the nature of the work and the strength desired. For example, in the construction of beams and floor pan- els, where maximum strength with minimum weight is desired, a rich concrete should be used, whereas in mas- sive foundation work, in which bulk or weight is the controlling factor, economy would point to a lean mix- ture. When good stone or gravel is used, the strength of the concrete depends upon the strength of the mortar em- ployed in the mixing and the proportion of mortar to aggregate. For a given mortar the concrete will be strongest when only enough mortar is used to fill the voids in the aggregate, less strength being obtained by using either greater or less proportion. In practice it is ( k- ' i( • u: i ti I 1 i ;''t M ' 1 Id \ \ '344 CEMENTS AND CONCRETES » ' f if ' I ? usual to add a slight excess of mortar over that roquired to fill the voids in the aggregate. It is more accurate to measure cement by weight un- less the unit employed be the barrel or sack, because when taken from the original package and measured in bulk there is a chance of error due to the amount of shaking the cenient receives. As it is less convenient, however, to weigh the cement, it is more usual to measure it by volume, but for the reasons stated this should be done with care. Proportioning Materials.— For an accurate determina- tion of the best and most economical proportions where maximum strength is required, it is well to proceed in the following way: First, proportion the cement and sand so that the cement paste will be 100 per cent, in ex- cess of the voids in sand ; next, determine the voids in the aggregate and allow sufficient mortar to fill all voids, with aa excess of 10 per cent. To determine roughly the voids in gravel or crushed stone prepare a water-tight box of convenient size and fill with the material to be tested, shake well and smooth off e"cn with the top. Into this pour water until it rises flush with the surface. The volume of water added, divided by the volume of the box, measured in the same units, represents the proportion of voids. The propor- tion of voids in sand niay be more accurately determined by subtracting the weight of a cubic foot of packed sand from 165, the weight of a cubic foot of quartz, and divid- ing the difference by 165 degrees. The following will serve as an example of proportion ing materials: Assume voids in packed sand to measure 38 per cent., and voids in packed stone to measure 48 per cent. Cement paste required per cubic foot of sand, HOW TO USE THEM 345 C.38 and 1-10 equals 0.42 cubic fot^t, approximately. By trial, 1 cubic foot of loose cement, lightly shaken, makps 0.86 cubic foot of cement paste, and requires ^ or 2 cubic feet of sand, approximately, producing an amount of mortar equal to 0.8.") and 2 (1-0.38) equals 2.09 cubic feet. Mortar required per cubic foot of stone equals 0.48, and 1-10x0.48 equals 0.528 cubic foot. There- fore 2.09 cubic feet mortar will require ^ equals 4 cubic feet of stone, approximately. The proportions are therefore 1 part cement, 2 parts sand, 4 parts stone. Althou jrtland cement concrete is well adapted for work exposed to sea-water. i \ I u Ill i\ "1 i ■! ^' :-l it Id h ■' 350 CEMENTS AND CONCRETES but when used for this purpose it should be mixed with fresh water. The concrete must be practically imper- vious, at least on the surfaces, and to accomplish this purpose the materials should be carefully proportioned and thoroughly mixed. It is also of great importance that the concrete be well compacted by tamping, par- ticularly on exposed surfaces. Concrete Work in Freezing Weather. — Although it is advisable under ordinary conditions to discontinue ce- ment work in freezing weather, Portland cement may be used without serious difficulty by taking a few simple precautions. As little water as possible should be used in mixing, to hasten the setting of the concrete. To prevent freezing, hot water is frequently used in mixing mortar or concrete, and with the same object in view salt is added in amounts depending upon the degree of cold. A common practice is to add 1 pound of salt to 18 gal- lons of water, with the addition of 1 oz. of salt for each degree below 32° F. Either of the above methods will give good results, but it should be remembered that the addition of salt ol'ten produces efflorescence. It seems to be a fairly well-established fact that concrete de- posited in freezing weather will ultimately develop full strength, showing no injury due to the low temperature. Rubble Concrete. — In massive concrete work consider- able economy may often be introduced by the use of large stones in the body of the work, but only in heav>' foundations, retaining walls, and similar structures should this form of construction be permitted. In plac- ing these large stones in the work the greatest care must be exercised to insure each being well bedded, and the concrete must be thoroughly tamped around them. Each HOW TO USE THEM 351 stone should be at least 4 inches from its neighbor and an equal distance from the face of the work. To Face Concrete. — A coating of mortar one-half inch in thickness is frequently placed next the form to prevent tb<> stone or gravel from showing and to give a smooth and impervious surface. If in preparing this mortar finely crushed stone is used instead of sand, the » » 'i •8bMt-m«tal plate nied In facing cracnt*. NO. 6. 4i work will more nearly resemble natural stone. A common method employed in facing concrete is to pro- vide a piece of thin sheet metal o' convenient length and about 8 to 10 inches wide. To this pieces of angle iron are riveted, so that when placed next to the mould a narrow space is formed in which the cement mortar is placed after the concrete has been deposited behind it. (No. 6.) The metal plate is then withdrawn and the 3! I *^ * ill I; m ii U i- 352 CEMENTS ANI5> CONCRETES concrete well tamped. The concrete and facing mor. tar must be put in at the same time so that they will set together. If the concrete is fairly rich, a smooth surface can usually be produced without a facing of mortar by working a spade up and down between the concrete and inner face of the mould, thus forcing the larger pieces of the aggregate back from the surface. Wood for Forms. — Lumber used in making forms for concrete should be dressed on one side and both edges. The expansion and distortion of the wood due to the absorption of water from the concrete frequently make it difficult to produce an even surface on the work, and unless the forms are accurately fitted together more or less water will find its way out through the cracks, carrying some of the cement with it. A method some- times adopted to minimize the effect of expansion is to bevel one edge of each board, allowing this edge to crush against the square edge of the adjacent board when expansion takes place. In the case of a wooden core or inside mold, expansion must always be taken into consideration, for if neglected it may cause cracks or complete rupture of the concrete. Sharp edges in con- crete are easily chipped and should bo avoided by plafr ing triangular strips to the comers of moulds. To pre- vent cement from sticking to the forms they may be given a coating of soft soap or be lined with paper. This greatly facilitates their removal and enables them to be used again with but little scraping. A wire brush answers best for cleaning the forms. Concrete Sidewalks. — A useful and comparatively simple application of concrete is in the construction of sidewalks, for which purpose it has been 'ised with marked success for a number of yeai*s. HOW TO USE THEM 352 Excavation and Preparation of Subgrade. — The ground is excavated to subgrade and well consolidated by ramming to prepare it for the subfoundation of stone, gravel or cinders. The depth of excavation will depend upon the climate and nature of the ground, being deeper in localities where heavy frosts occur or where the ground is soft than in climates where there are no frosts. In the former case the excavation should be carried to a depth of 12 inches, whereas in the latter from 4 to 6 inches will be sufficient. No roots of trees should be left above the subgrade. The Subfoundation. — The foundation consists of a layer of loose material, such as broken stone, gravel, or cinders, spread over the subgrade and well tamped to secure a firm base for the main foundation of concrete which is placed on top. It is most important that the subfou'^dation be well drained to prevent the accumula- tion of water, which, upon freezing, would lift and crack the walk. For this purpose it is well to provide drain tile at suitable points to carry off any water which may collect under the concrete. An average thickness for subfoundation is 4 to 6 inches, although in warm cli- mates, if the ground is firm and well drained, the sub- foundation may only be 2 to 3 inches thick or omitted altogether. The Foundation. — The foundation consists of a layer of concrete deposited on the subfoundation and carry- ing a surface layer or wearing coat of cement mortar. If the ground is firm and the subfoundation well rammed in place and properly drained, great strength will not be required of the concrete, which may, in such cases, be mixed in about the proportions 1-3-6, and a depth of only 3 to 4 inches will be required. Portland cement should i % ii 854 CEMENTS AND CONCRETES I ' t: ^'\i ft'" be used and stone or gravel under 1 inch in size, the con- crete being mixed of medium consistency, so that moisture will show on the surface without excessive tamping. The Top Dressing or Wearing Surface.— To give a neat appearance to the finished walk, a top dressing of cement mortar is spread over the concrete, well worked in, and brought to a perfectly smooth surface with straightedge and float. This mortar should be mixed in the proportion 1 part cement to 2 parts sand, sharp coarse sand or scren.iags below one-fourth inch of some hard, tough rock being used. The practice of making the concrete of natural cement and the wearing surface cf Portland is not to be commended, owing to a tendency for the two to separate. Details of Construction. — A cord stretched between stakes will serve as a guide in excavating, after which the bottom of the trench is well consolidated by ram- ming; any loose material below subgrade is then spread over the bottom of the trench to the desired thickness and thoroughly compacted. Next, stakes are driven along the sides of the walk; spaced 4 to 6 feet apart, and their tops made even with the finished surface of the walk, which should have a transverse slope of one-fourth inch to the foot for drainage. Wooden strips at least \\'y inches thick and of a suitable depth are nailed to those stakes to serve as a mould to concrete. By carefully adjusting these strips to the exact height of the stakes tlioy may be used as guides for the straight- edge in levelling off the concrete and wearing surface. The subfoundation is well sprinkled to receive the con- crete, which is d''po'iitcd in the usual manner, well tamped behind a board set vertically across the trench, ; I HOW TO USE THEM 355 and levelled off with a straightedge as shown in Fig. 7, leaving one-half to 1 inch for the wearing surface. Three-eighths inch sand joints are provided at intervals of 6 to 8 feet to prevent expansion cracks, or, in case of settlement, to confine the cracks to these joints. This is done either by depositing the concrete in sections, or by dividing it into such sections with a spade when soft and filling the joints with sand. The location of each joint is marked on a wooden frame for future reference. J>«U1U of eoncnt* walk coBctraetleB. NO. 7. Care must be exercised to prevent sand or any other material from being dropped on the concrete, and thus preventing a proper union with the wearing surface. No section should be left partially completed to be finished with the next batch or left until the next day. Any con- crete left after the completion of a section should be mixed with the next batch. It is of the utmost importance to follow up closely the concrete work with the top dressing in order that the 'jf. 'i;^'^ if m til i : I; I .( H 356 CEMENTS AND CONCRETES two may set together. This top dressing should be worked well over the concrete with a trowel, and levelled with a straightedge (No. 7) to secure an even surface. Upon the thoroughness of this operation often depends the success or failure of the walk, since a good bond be- tween the wearing surface and concrete base is absolute- ly essential. The mortar should be mixed rather stiff. As soon as the film of water begins to leave the surface, a wooden float is used, followed up by a plasterer's trowel, the operation being similar to that of plastering a wall. The floating, though necessary to give a smooth surface, will, if continued too long, bring a thin layer of neat cement to the surface and probably cause the walk to crack. Jointer lued la dlTUUag walk Into MCtiOM. NO. 8. The surface is now divided into secticna by catting en- tirely through, exactly over the joints in the concrete. This is done with a trowel guided by J» straightedge, after which the edges are rounded off with a special tool called a jointer, having a thin shallow ton^me (No. 8). These sections may be subdivided in any manner desired for the sake of appearance. A special tool called an edger (No. 9) is run round the outside of the walk next to the mould, giving i* a neat rounded edge. A toothed roller (No. 10) having: small HOW TO USE THEM 357 projections on its face is frequently used to produce slight indentations on the surface, adding somewhat to Tool tiaed in roundloK edges. NO. 9. the appearance of the walk. The completed work must be protected from the sun and kept moist by sprinkling •BoUtt oMd la ODtoblns sntteee NO. 10. for several days. In freezing weather the same precau- tions should be taken as in other classes of concrete work. *' 't ■'1 ^1 i^ i *l J 358 CEMENTS AiND CONCRETES i m 1 1 t ;l: U n; I ) 1 1 Concrete Basement Floors. — Basement floors in dwelU ing houses as a rule require only a moderate degree of strength, although in cases of very wet basements, where water pressure from beneath h^ to be resisted, greater strength is required than would otherwise be necessary. The subfoundation should be well drained, sometimes re- quiring the use of tile for carrying ofiE the water. The rules given for constructing concrete sidewalks apply equally well to basement floors. The thickness of the concrete foundation is usually from 3 to 5 inches, ac- ' cording to the strength desired, and for average work a 1-3-6 mixture is sufficiently rich. Expansion joints are frequently omitted, since the temperature variation is h'ss than in outside work, but since this omission fre- prove thoroughly satisfactory, must fulfil three conditions: (1) It must be obtainable cost; (2) it must possess sufficient strength to meet the demands of gen- eral farm use; (3) it must not be subject to decay, and must be able to withstand snccessfuUy the effects of water, frost and fire. Although iron posts of various designs are frequently used for ornamental purposes, their adoption for general farm use is prohibited by their excessive cost. Then, too, iron posts exposed to the weather are subject to corrosion, to prevent which neces- sitates repainting from time to time, and this item will entail considerable expense in cases where a xarge num- ber of posts are to be used. Il HOW TO USE THEM 361 At. the present time the material which seems most nearly to meet these requirements is reinHorrvd con- crete. The idea of constructing fence posts of concrete reinfoi-eed with iron or steel is by no means a new out', but, on the contrary, such posts have been experimented with for years, and a great numb«r of patents have been issued covering many of the possible forms of reinforce- ment. It is frequently stated that a reinforced con- crete post can bt: made and put in the ground for the same price as a wooden post. Of course this will de- pend in any locality upon the relative value uf wood and the various materials which go tu make up the concrete post, but in the great majority of cases wood will prove the cheaper material in re^'urd to first cost. On tho other hand, a concrete post will last indefinitely, il^ strength increasing with age, whereas the wooden post must be replaced at short intervals, probably making it more expensive in the long run. In regard to strength, it must be borne in mind that it is not practicable to make concrete fence posts as strong as wooden posts of the same size ; but since wooden posts, as a rule, are many times stronger than is nwwft- sary, thin difference in strength should not condemn the use of reinforced concrete for this purpose. Moreover, strength in many cases is of little importance, the fenee being usetl only as a dividing line, and in such cji^cs small concrete posts provide ample strength and presint a very uniform and neat appearance. In any ease, tu enable concrete posts to withstand the loads they aie called upon to carry, sufficient strength may be secured by means of reinforcement, and where great strength is required this may be obtained by using a larger nost with a greater proportion of metal and well braced, as iff 6! ^:\ f |: ■i 1 1 J SI! 1^ : ,H 362 CEMENTS AND CONCRETES is Mual in such cases. In point of durability, concrete is unsurpassed by any material of construction. It offers a perfect protection to the metal reinforcement and is not itself affected by exposure, so that a post constructed of concrete reinforced with steel will last indoflnitely and require no attention in the way of repairs. Reinforcement. — No form of wooden reinforcement, either on the surface or within the post, can be recom- mended. If on the surface, the wood will soon decay, and if a wooden core is used it will, in all probability, swell by the absorption of moisture and crack the post. The use of galvanized wire is sometimes advocated, but if the post is properly constructed and a good concrete used, this precaution ajrainst rust will be unnecessary, since it has been fully donionstrated by repeated testa that concrete protects steel perfectly from rust. If plain, smooth wire or rods are used for reinforcement they should be bent over at iie ends or looped to pre- vent slipping in the concrete. Twisted fence wire may usually be obtained at a reasonable cost and is very well suited for this purpose. Barbed wire has been proposed and is sometimes used, although the barbs make it ex- tremely difficult to handle. For the sake of economy the smallest amount of metal consistent with the desired strength must be used, and this requirement makes it necessary to place the reinforcement near the surface, where its strength is utilized to greatest advantage, with only enough concrete on the outside to form a protective covering. A reinforcing member in each corner of the post is probably the most efficient arrangement. Concrete for Fence Posts. — The concrete should be mixed with Portland cement in about the proportions 1-21/^-5, broken stone or gravel under Yz inch being used. HOW TO USE THEM 363 In cases when> the af^gre^ate than 14 in<^h> 1^'<*> "*^^ '^'^y ^^ it may be omitted altogether. A Nistcncy Ih reoommended on the molda better and with Ic88 tr /Ji, dry. Molds for Fence Po«/v — Vi.-rr.oinv poji, < to the me of a tapering post, w! .r, . ; irtvj.iiiv.'" calties in the way Oi <> ri(.^r;i. contains pieces smaller used, and in some csAes mixture of medium con- ground that it fills the .'ntr than if mixed quite AH him rs no diffi- "Xjnsidered, V^odra ■oM-tor ■aUac fMM Doat* wttk NO. 12. tm uparlac Mm. II 1 ■) wooden molds will be found most suitable. Tl ,/ can easily and quickly be made in any desired form aui size. Posts may be molded either in a vertical or horizontal position, the latter being the simpler and better method. Jf molded vertically a wet mixture is necessary, requir- ing a longer time to set, with the consequent delay in removing the molds. No. 12 shows a simple mold, which has been used with satisfactory results in this laboratory. MS: J 364 CEMENTS AND CONCRETES This mold has a capacity of four posts, but larger molds could easily be made on the same principle. It consists of two end pieces, (a) carrying lugs, (b) between whidi are inserted strips (c). The several parts are held to- irether with hooks and eyes, as shown in No. 12. To pre- vent any bulging of the side strips they are braced, i>s illustrated. Dressed lumber at least 1 inch thick, and preferably IV^ inches, should be used. In No. 12 the Hfl .•WaoiteB omM tor Maklaf I NO. 13. post nieasiires 6 by 6 inches at the bottom, 6 by 3 at the top, and 7 feet in length, having two parallel sides. If it is desired to have the poets square at both ends th»' mold must be arranged as in No. 13. This latter form of post is not as strong as the former, but requires less concrete in its construction. Great care in tamping is necessary to insure the corners of the mold being well i I T.. HOW TO USE TUEM 365 filled, and if this detail is not carefully watched, the metal, being exposed in places, will be subject to rust. Attaching Fence Wires to Posts. — ^Various devices have been suggested for attaching fence wires to the posts, the object of each being to secure a simple and permanent fastener or one admitting of easy renewal at any time. Probably nothing will answer the purpose better than a long staple or bent wire well embedded in the concrete, being twisted or bent at the end to prevent extraction. Galvanized metal must be used for fasteners, since they hi i; 1 " 'I'll ■Detail sbowtBf OMthod at •^ taching wire to poat. NO. 14. are not protected by the concrete. A piece of small flex- ible wire, about two inches in length, threading the staplf and twisted several times with a pair of pliera, holds the line wire in position. (Xo. 14.) Molding and Curing Posts.— For the proper method of mixing concrete see previous pages. It is recommended that only so much concrete bo mixed at one time as can be used before it begins to harden ; but if an unavoidable delay prevents the posts being molded until after the < i t ■ It-,', ; II. I It I I*' ', U :-k f ' 5 ii! i! I' 366 CEMENTS AND CONCRETES concrete has begun to set, it is thought that a thorough regauging with sufficient water to restore normal con- sistency will prevent any appreciable loss of strenglb, though the concrete may have been standing one or two hours. In using a mold similar to those illustrated in Nos. 12 and 13 it is necessary to provide a perfectly smooth and even platform of a size deiK'uding upon the number of posts to be molded. A cement lloor if accessi- ble may be used to advantage. The molds when in place are given a thin coating of soft soap, the platform or cement floor, serving as bottom of mold, being treated in the same way. About VyU inches is spread evenly over the bottom and carefully tamped, so as to reduce it to a thickness of about 1 inch. A piece of board cut aa in No. 12 will be found useful in leveling off the concrete to the desired thickness before tamping. On top of this layer two reinforcing members are placed about 1 inch from the sides of the mold. The molds are then filled and tamped in thin layers to the level of the other two reinforcing members, the fasteners for fence wires being inserted during the operation. These reinforcing mem- bers are adjusted as were the first two, and the remain- ing 1 inch of concrete tamped and leveled off, thus com- pleting the post so far as molding is concerned. To avoid sharp edges, which are easily chipped, triangular strips may be placed in the bottom of mold along the sides, and when the molds have been filled and tamped, similar strips may be inserted on top. The top edges may be beveled with a trowel or by running an edging tool hav- ing a triangular projection on its bottom along the edges. Such a tool is shown in No. 15, and can easily be made of wood or metal. It is not necessary to carry ihe bevel below the ground line. HOW TO USE THEM 867 The eads and sides of the mold may be removed after twenty-four hours, but the posts should not be handled for at least one week, during which time they must be well sprinkled several times daily and protected from sun and wind. The intermediate strips may be carefully withdrawn at the end of two or three days, but it is bet- ter to leave them in place until the posts are removed. Although a post may be hard and apparently strong when one week old, it will not attain its full strength in that length of time, and must be handled with the utmost care to prevent injury. Carelessness in handling green posts frequently results in the formation of fine cracks, which though unnoticed at the time, give evidence of their presence later in the failure of the posts. r ; I %f Vool ONd for bcveUns edges of posu. NO. 15. Posts should be allowed to cure for at least sixty days before being placed in the ground, and for this purpose it is recommended that when moved from the molding platform they be placed upon a smooth bed of moist sand and protected from the sun until thoroughly cured. Dur- ing this period thoy should receive a thorough drench- ing at least once a day. ii 1 T If hi I 368 CEMENTS AND CONCRETES The life of the molds will depend upon the care with which they are handled. A coating of mineral oil or shellac may be used instead of soap to prevent the cement from sticking to the forms. As soon as the molds are removed they should be cleaned with a wire brush before being used again. The cost of reinforced concrete fence posts depends in each case upon the cost of labor and materials, and must necessarily vary in different localities. An esti- mate in any particular case can be made as follows : One cubic yard of concrete will make twenty posts measuring () inches by 6 inches at the bottom, 6 inches by 3 inches at the top, and 7 feet long, and if mixed in the propor- tions 1-21/2-5, requires approximately: 1.16 barrels of cement, at $2 $2.32 0.44 cubic yard of sand, at 75 cts 33 0.88 cubic yard of gravel, at 75 cts 66 Materials for 1 cubic yard cement $3.21 Concrete for one post ^ • 28 feet of 0.16 inch steel wire, at 3 cts a pound 06 Total cost of concrete and metal for 1 post 23 To this must be added the cost of mixing concrete, molding and handling posts, and the costs of molds, an addition which should not in any case exceed 7 cents, making a total of 30 cents per post. Concrete Building Blocks.— ConcreU building blocks, or cement blocks, as they are frequently called, are more extensively used now than ever befort». These blocks are molded hollow primarily to reduce their cost, but ihis hollow eonstfuetion serves other useful purposes at the same time. The fundamental principles governing HOW TO USE THEM ordinary concrete work, so far as proportioning and mix in J? materials is concerned, apply equally well to the manufacture of building? blocks, and it should be borne in mind that strength and durability can not be obtained by the use of any machine unless the cement, sand, and aggregate are of good (|uality, properly proportioned and well mixed. The aggregate for blocks of ordinary wize should be crushed stone or gravel not larg«'i' than Y2 inch. One of the chief causes of complaint against the concrete building block is its porosity, but this defect is in a great measure due to the fact that in an endeavor to economize too little cement is frequently used. It is not unusual to give the blocks a facing of cemeut mor- tar consisting of about 2 parts sand to 1 of cement, while the body of the block is composed of a concrete oi suflfi- cient strength, though not impervious. Thus outside layer of mortar adds practically nothing to the strength of the block, and is used simply to give a uniform siir- face and to render the face of the wall more clearly im- pervious to water. It would not be praiticable as a rule to attempt the manufaetuix' of eiinerete bloeks without one of the many forms of molding machines designed for the pui-pose. noi would it be economical to purehase sueh a machine un- less a sutfieicnt muiiber of bloeks were reipiired to jiustify such an outlay. Blocks in almost any desired shape and size, with either plain or ornamental facias, may be ob- tained on the market, and in the great majority of cases it is best to buy them fnmi some reliable Hrm. Among the advantages claimed for hollow concrete block con- struction may be mentioned the following: (1) Hollow block coiLstruction introduces a saving of material over brick or stone masonry. t'3 r n' ;■ i- 370 CEMENTS AND CONCRETES (2) The cost of laying concrete blocks is less than for brick work. This is due to the fact that the blocks, being larger, require a much smaller number of joints and less mortar, and, being hollow, are of less weight than solid brick work. (3) A wall constructed of good concrete blocks is as strong or stronger than a brick wall of equal thickness. (4) Concrete blocks, being easily molded to any de- sired form, will prove to be a far more economical build- ing material than stone, which has to be dressed to shape. (5) Experience has proved concrete to be a most cx- •ellent fire resisting material, (6) Concrete blocks, being hollow, tend to prevent sudden changes of temperature within a house, making CO :;1 in summer and easily heated in winter. (7) Jhe hollow spaces provide an easy means for running pipes and electric wires. These spaces may also ^ used wholly or in part for heating and ventilating ues. Tests of Concrete Fence Posts.— In the summer of 1004 a number of reinforced concrete fence posts were made for experimental purposes, with a view to deter- mining their adaptability for general use. These posts were made both with and without reinforcement, and tested at the age of 90 days. The reinforcement, rang- ing from 027 per cent, to 1.13 per cent., consisted of four rotiiul steel rods, one in each corner of post about 1 inch from surface, the posts having a uniform cross- section of 6 by 6 inches. The posts were molded in a horizontal position, as this was found by trial to be more satisfactory than molding them vertically. HOW TO USE THEM 371 The concrete was mixed moderately soft, crushed stone between 1 inch and '/4 inch and gravel under •J4 inch being used as aggr^^te. River sand, fairly clean and sharp, was employed with Portland cement. The posts were tested as beams, supported at both ends and loaded at the centre, with spans varying from 4 feet to 5 feet 6 inches. An attempt was made to prevent slipping by providing the reinforcing rods with collars and set screws at the ends, but in every case, with but two ex- ceptions, the rods slipped under a comparatively light load, thus showing the necessity for some form of me- chanical bond. As would be expected, those posts which were not reinforced possessed very little strength. i f I tvi4- .*'o^- Mettaod of teatlnf ponB oltder static loads. :!(■■ A series of tests was made with sheet-iron reinforce- ment, in the form of round and square pipes, embedded in the posts, but these posts, though developing consid- erable strength, proved less economical than those rein- forced with plain rods, and at the same time were less simple in construction. The results of these tests, as re- corded in Table I., do not properly represent the strength of similar posts in which some form of mechanical bond « provided to develop the full strength of the reinforce- ment. 372 CEMENTS AND CONCBBTBS o u u u ST. t. E K O ■.J c w o II. % u b O \ in a > < !':<' 28§ag8SI5§?855gig88§832?!H8|2||S2 ,1 I I i •c a « s«l^^^ai€^^l«««i^|i55S|€€5|i5€€_^| 2 J:::! go -O ■ • ■<0 '•2 • -.9 ■ • -S : : :S : : : : :2 • "O : : :ao O M 8 a "3 3 r,t;S;KKBBSRSi^S^^^^^^?2S5?s?^i?«S 8 s -a -«a888''SF!35Sss68SSJ?—aaRS5!;S''sasagjsi h *i 5 Q g O as w III o i il HOW TO USE THEM 373 |s|§§8Mliiiiiia§9iSS 998 §11 fSS R |s§§liSSIggg§ll§8§893 S9 i &S3 SSS 1^ a-5 o en M O O n -a -c M i o o I |p.;^SP§§SI8^l§§l88g§ §§i SSI u% IP.P8 S§^8I89S§8S§§|8 89 i §18 §1 i V eogoo « o o 00 « o o o og< o o o ooo ooo «oo 8 : :S : :fi : : : -S : • ■ :C . S . : 00 : ^S???SS??SSS22g?S???§ ?ss ss? s?: 7SS^!S$S^!£S;^^SSSSSSSS9 SSS 888 SSS ? rrcr'^csessssssaoowootS-Soo ioa ■ O 0>O 00 o e5?'»=£5SS:'5?*''2asSa853 S&S S88 gg 4 •I:, V. 874 CEMKNT8 AND CONCRETES t% I'R'll In order to obtain more data on the subjei^ this in- vestigation has been supplemented by a second series of terts, the results of which form the subject matter for the sections on concrete fence posts and are expressed numerically in Table II. In these tests it was decided to make the posts taper- ing in order to economize material and reduce their weight. For the concrete, Portland cement, river sand, and gravel were used in the proportion l-2>/|.-5, meas- ured by volume, the gravel being screened below Vu inch. SuflBcient water was uw^d in mixing to produce a plastic mass, requiring only a moderate degree of tamping to bring water to the surface. The posts were molded and kept under wet burlap for four weeks, and tested at the end of sixty days. The reinforcing members were placed in the corners of the posts about 1 inch from the surface, being looped and b«'nt, as indicated in Table II. These posts were not desijmed with a view to developing the ultimate compressive strength of the concrete, but where greater strength is neees-sary it may be obtained at small expense by increasing the percentage of reinforcement. It is important that fairly rich concrete should be used ill all cases to oiiable the posts to stand exposure and to prevent chipping. All of these posts measured 6 by 6 inches at the bottom and 6 by >i inches at the top, except Nos. 29, :W. 31, 32, 33, and 34, which were 6 by 6 at the bottom and 3 by 3 at the top. It will be noticed that the saving in concrete introduced in the construction of these posts is accompanied by a marked decrease in strength as compared with the other posts similarly reinforced. It would also appear that the twisted wire has a slii^ht HOW TO USE THEM 375 Tabiib II. SHOwiNn the Strength of Rkinfobced CoNCBRTK Fence Pcwts. No. Kind of rein- forcemeDt. 1 •i X 4 37 :«« !• 10 II ».• HI i:i I'l III 17 IH lu a •H 'ih ■i»\ ■r, •» •3* ;n 41 Xy :W 6 7 H 14 ■JO l>rawn uteel rod* ilo do do do do A ..do do do do Twiaud ftiM win do .do do ...do . .ilo ...do ...do ..do ., ..do Harlrt'd wire ...do ...do ...do ...do ...do ....ra\vii liteel rodH do do T«iiU4 Uv» wtrt do O.OH .im IM .(M .(W .OM .11* .l .OK .(»> .13 .13 .13 .13 .OX .1!» .'» .0<> .06 Mon 7,% xm Hlft 770 7MI I.ViO l.'7.'i ijno l.'iUO WO K-JO M» 74S .MM) &'« NiO 4M0 ■ >• 3 3 & £f9 CB^T O^ Ci.^V //V »5>f/VO /O /S SO 3S JO ^S -^O ^S 90 3 DiaKram showine the effect of clay on cement mortara. NO. 19. Retempering. — Table III. illustrates the effect of re- tempering Portland cement mortar. The mortars used consisted of Portland cement and crushed quartzite be- tween 1 and 2 miUimetcrs in size, mixed in different pro- HOW TO USE THEM 379 portions. In each case, after the initial or final set had taken place, sufficient water was added in retempering to TABLE III. — Effect of Retempering on Cement Mobtabs. Tensile Strenirth, in Pounds Per Square Inch. Treatment of Mortar. Neat Cement. a IPart Cement, IPart Sand b IPart Cement, 2 I'arts Sand, c IPart Cement, 3 Parts Sand, d Mortar made up into briquettes . immediately after mixing 651 650 673 634 679 624 701 624 681 610 527 493 529 480 492 417 385 421 403 409 Average 657 628 504 407 Mortar allowed to take initial set, then broken up and made into briquettes 671 593 644 633 724 692 670 654 676 700 589 554 559 534 532 326 349 330 858 267 Average 653 678 554 826 Mortar allowed to take final set, then broken up and made into briquettes 455 522 525 558 642 527 569 587 566 568 492 491 497 486 531 864 880 861 315 845 Average 540 563 499 358 n Initial set, 1 hour 42 minutes: fiual set, 7 hours 15 minutes. '» Initial set, 1 hour 30 minutes- final set, 7 hours 15 min» tea. r Initial set, 2 hours; final set, 7 hours. (i Initial set, 2 hours 20 minutes; final set, 7 hours. restore normal consistency, at the age of four months. The briquettes were tested I if 4. iim » it if jS I K 'm I. t 380 CEMENTS AND CONCRETES Some Practical Notes.— Spencer B. Newbury, who is an authority on the subject, says "that the making of good cement concrete is a comparatively simple matter, and yet, like most simple operations in engineering, there is a right way and a wrong way of doing it. Probably nine-tenths of the concrete work done falls far short of the strength it might develop, owing to the incorrect pro- portions, use of too much water, and imperfect mixm-. AU authorities are agreed upon the importance of thor- ough mixing and the use of the minimum quantity of water in all classes of concrete work. The matter of cor- rect proportions of cement, sand, broken stones, etc., is one which requires some thought and calculation, and by proportioning these ingredients correctly an immense saving in cost and increase in strength can easily be se- cured. The chief object in compounding concrete is to pro- duce a compact mass, as free as possible from pores or open spaces; in short, to imitate solid rock as closely as possible. Cement is the "essence of rock" in portable form, and by its judicious use granular or fragmentary materials may be bound together into solid blocks of auy desired size and shape, which in strength and wearing' qualities are at least equal to the best stone that comes from the quarries. Cement is, however, very costly m comparison with the other ingredients of concrete, and must not be used wastefully. A little cement, judi- ciously used, is better than a large quantity thrown in recklessly, as a little study of the principles involved will plainly show. To produce a compact mass from fragmentary ma- terials, the voids must be filled. Imagine a box holding 1 cubic foot. If this were filled with spheres of uniform HOW TO USE THEM 381 size, the voids or open spaces would be one-third the total volume, or 33 1-3 per cent., with spheres o^ various sizes, as, for example, from large marble down to fine shot, the voids would be much less, and it would theoretically be possible, by the use of spheres of graded sizes, from the largest down to dust of infinite fineness, to fill the box completely, so that there would be no voids whatever. In practice it is well known that the use of materials of varying fineness gives the best concrete, since the voids are much less than in materials composed of pieces of uniform size. Hence the common practice of making concrete with cement, sand and broken stone, instead of with cement and sand, or cement and stone only. The sand fills the voids, and if the proportions are correct, a practically solid mass results. As an example of this, the writer found the briquettes of cement with three parts of sand and four parts gravel showed higher ten- sile strength at 28 days than those made with three parts sand only. The following table gives the relative weights of a given volume of different materials, and also the per- centage of voids, as determined by the writer. The ma- terials were shaken down in a liter measure by giving one hundred taps on the table, and weighed. In the case of the broken stone a larger measure was used. The voids were calculated from the specific gravity. Comparison of the three different grades of Sandusky Bay sand shows how greatly the percentage of voids varies with the proportion of fine and coarse grains pres- ent. The first is the natural sand, not screened, as pumped up by the sand sucker from the bottom of the bay, and contains a large amount of fine gravel. The second is the same, passed through a 20-mesh screen to •] :« I m m •1 fill 382 CEMENTS AND CONCRETES remove the coarse particles. It will be seen that this operation increases the proportion of voids from 32 to 38 per cent. The third is the same sand passing a 20- mesh and retained on a 30-mesh screen, thus brought to the fineness of the "standard sand" used in cement test- ing. This shows 40.7 per cent, of voids, owing to the uni- form size of the grains. The same relation is seen in the WEIGHT OF UNIT MEASURE AND PERCENTAGE OF VOIDS IN VARIOUS MATERIALS. Per Cent of Voids. Portland cementr Louisville cement SanduBky Bay sand, not screened Sandusky Bay sand, through 20-nie8h HCTftftTl ,,,......... •* Sandusky Bay sand, 20-30 mesh (standard sand) Gravel, K to % inch Gravel, Y* to Vt inch •• •• Marblehead broken stone (chiefly about egg size) 40.7 42.4 85.9 two grades of gravel given in the tab>, that containiug finer grains showing much the lower percentage of voids. These figures illustrate the imprudence of screening any of the materials used in making concrete. The pres- ence of clay in sand is, however, objectionable, not be- cause of its fine state of subdivision, but because the clay coats the sand particles and prevents the adhesion of the cement. Such sand might be improved by wash- ing, but probably not by screening. It has been found HOW TO USE THEM 383 that cement which has been ground to dust with an equal amount of sand goes much further when used for con- crete than the same quantity of cement when used in the ordinary way. This is doubtless ovting to the fact that the sand dust aids in filling the voids. It is also well known that slaked lime, when added to cement mor- tar, greatly increases the strength of mixtures poor in cement. From the figures given in the above table the compo- sition of a theoretically perfect concrete may readily be calculated. The existence of voids in the cement may be disregarded, since in the process of hardenmg the cement sends out crystals in all directions, completely encrusting the sand particles and practically filling all the voids which the cement itself contains. Examination of a well-hardened briquette of cement with 3 parts sand, after breaking, with the aid of a lens, will show this clearly Suppose, for example, we wish to make the best pos- sible concrete from Portland cement with the sand and gravel given in the above table. We should, of course, choose the unscreened sand and gravel as containing the least proportion of voids. One hundred measures of gravel would require 35.9 measures of sand. As the sand contains 32.3 per cent, of voids, we require 32.3 per cent, of 35.9, or 11.6 measures of cement. The pro- portions would, therefore, be : Cement, 11 ; sand, 3, and gravel, 9. It is customary, however, to increase the pro- portion of mortar (cement and sand) by about 15 or 20 per cent., in order that the coarser materials may be completely coated with the finer mixture. Making this addition, we find the concrete proportions to be : Cement, 1 ; sand, 2.8 ; gravel, 7. Allowance must also b( made in i k 384 CEMENTS AND CONCRETES practice for imperfect mixinj?, since the matcriata can jiever be distributed in a perfectly uniform manner. I'ractically, with these materials, a concFete of cement 1. sand 21/0, and gravel 6, would probably give the best result, and" little or no improvement would result from increasing the proportion of cement. A similar calculation shows that the correct propor- tions for a concrete made of the sand and broken stone given in the table would be 1 to 3 to GVg. Increasing the amount of cement and sand by 20 per cent., we have 1 to 3 to 51/2. Probably 1 to 2V2 to 5 would be found to give the best results in practice. The determination of the voids in the sand, gravel and broken stone used is of the greatest value in adjusting the proportions of concrete The simplest method of determining this in the case of <'ravel and broken stone is to have a metal box made of 1 cubic foot capacity; this is filled with the material to be tested, well shaken down and struck off level. The box and contents are then weighed. Water is now poiired in until it rises even with the surface, and the ^otal weight again taken. The difference in the weights is the weight of the water filling the voids of the ma- terial. Now 1 eubic toot of water weighs 64 4-10 lbs., «nd from the weight of the water found the percentage of voids can be simply calculated. For example, in one experiment the box and broken stone weighed 88 l\s. After filling the spaces in the stone with water the wei"ht wjis 1171/2 lbs., a difference of 291/2 lbs. The percentage of voids is, therefore, 291/2x100 divided by 62.4 equals 47 per cent. In the case of sand this method will not answer, as it is difficult to completely fill the voids of the sand by HOW TO USE THEM 885 adding the water. The voids can, however, be readily calculated from the weight of a cubic foot and the spe- cific gravity. The specific gravity of quartz sand is about 2.65. A cubic foot of sand, free from voids, would therefore weigh 2.65x62.4 equaling 165.4 lbs. The weight of a cubic foot of sand, well shaken down, was, however found to be only 112 lbs., a difference of 53.4 lbs. The proportion of voids was, therefore, 53.4x100 divided by 165.4 equals 32.3 per cent. The percentage in voids in clean natural sand does not vary greatly, and may be taken as 33 to 35 per cent, for coarse and 35 to 38 per cent, for fine sand. We have already seen that with the materials above described, concrete composed of Cement 1, sand 2Y^, gravel 6, or Cement 1, sand 2V^, broken stone 5 by measure, will be practically compact and non-porous, and that there is no object in increasing the proportion of cement. Such concrete, if made from Portland cement, will, however, be rather expensive, requiring about one barrel of cement (equals 3% cubic feet) for every cubic yard. This is unnecessarily good for ordinary work, and will only be required for foundations of engines and other heavy machinery, in which the best possible result - must be secured regardless of cost. In cheaper concretes the relative proportions of sand and broken stone should be the same, as determined by the voids in the coarser materials, while the proportion of cement may be varied according to the required eondition.s of quality and cost, ^lost excellent concrete may be made by using : Portland cement 1, sand 7, stone or gravel 14. Ilt-ve are specimens iif these two concretes, taken from tria'i blocks laid Get. 1, 1894, to determine the best p'**. S86 CEMENTS AND CONCRETES portion for the foundation of brick pavement. The richer of the two, 1-5-10, is certainly good enough for any purpose, even for engine foundationg. A cubic yard of such concrete reciuires about V-j barrel of cement ; th«' total eont of the cement, sand and stone is about two dollars per cubic yard. This is no more expensive than concrete made from Louisville cement with 2 of sand and 4 o" broken stone, and is inmiensely superior to the latter in strength. The following table shows the results obtained in (Germany by R. Dykerhoff in determining the iTushing strength of various concretes. The blocks used were 2Vi: inches sipiare, and were test**'! after one day in air and 27 days in water. Proportlonii by Mcaiure. StreoRth under Compreaalon Pounds per Square Indi. Portland Cement. Sand. Oravel. 2 2125 2 8 2747 2 6 2387 6 978 8 •• 1888 8 6 1632 8 6K 1516 4 „ 1053 1 4 5 1273 4 8X 1204 These figures prove the statement already made, that mixtures of cement and sand are strengthened, rather than weakened, by the addition of a suitable quantity of gravel. It will be noticed that the mixture — cement 1, HOW TO rSK TIIKM 387 Band 2, jrravel 5 — is a concrete oant protlnced has a surfufe cither friable when newly cast, or when dry the surface is full of small water lines, like a map, or a broken spider's web. This is owinp to the suction caused by the porous naliire of the mould and the water escaping' through the weak or open parts leavinir correspondinjr lines on the concrete surface. These defects are obviated by using waterproof cen- tring. Where fineness of finish is not required, such as ware- house floors, the surface can be made sufficiently fair and smooth when filling in the concrete withotit sub- sequent setting. The plaster is laid on the centring, and made fair and smooti d then the surface is saturated with water to co» ct the suction; or the surface, if dry, may be brushed over with a thin soaj) solution to prevent adhesion. On this surface a coait of neat cement about Vs inch is laid, and <>n this the concrete is placed. The two unite in one body, aiul when set, and the centring struck, the plaster sheet comes with the boards, leaving a smooth surface. This surface can be made in color by lime washing, which will also give more light, or a finished white surface can be obtained by substituting parian or other white cement for the neat Portland cement. The concrete must not be laid until the white cement is firm, not set, otherwise the concrete will force its way in thin or soft parts and disfigure the surface. I have success- fully used this method for obtaining a finished sur- face when encasing iron girders with concrete for fire- proof purposes. Staircase Materials. — With regard to the materials for a concrete staircase, no one who intends to eou- 400 CEMENTS AND CONCRETES Htruct them substantially, fireproof and economically, can afford to use common substances, when by judi- cious selection and for a trifling additional first cost a combination of materials can be obtained, which, if not (strictly speaking) fireproof, is at least the most incombustible constructive compound known. This is a quality of the most vital importance in modern house construction. Portland cement and slag cement an; the best known matrices. The finer Portland cement is ground, the greater its heat-rcsi.sting powers. Slag cement is lighter than Portland cement, and its fire- resisting properties exceed those of both gypsum and Portland cement. But as its manufacture is as yet somewhat limited, and its strength not uniform, ex- ceptional care must be exercised in testing its general (lualities before using it for staircases. Broken slap, firebricks, clinkers and pottery ware are the best ag- gregates, being practically fireproof. All should be (•lean, and in various graduating sizes, from that of n pin's head to that of a walnut, for roughing out with. The topping should be the same as that described for Eureka paving. PUling in Stairs.— Beiore gauging the materials, sweep out all dust in the interior of the framing and the wall chase and then wet the latter, and oil the woodwork. If the wood of the nosing moulds and risers is sappy or open grained, the long lengths, be- fore being cut and fixed, should be made smooth and indurated by coating with a solution of hot paraffin wax. The smoother and less absorbent the surface of the wood, the more readily and cleaner will the mould leave the cast work. Paraffin also renders the wood uamp-proof, thus preventing swelling or warping. For HOW TO USE TIT EM 401 nrdlnary purposeH one or two coatH of parafHn oil will lie found Hufficient. Thi.H Nhould be done two or three hoiifN before the stepH ure filled in, ho hh to allow tlio oil to partly dry in and stop the pores of the wood. If the wood absorbs ail the oil, and has a dry sur- face, brush the surface ajjain with parai!ln, usin? a semi-dry brush. This should be done as the work ')ro- eeeds. If the surface is over wet, the oil mixes 'vith tht' cement, thus causing a more or less rough sur- face. Soap solution may be safely used for rough concrete, or where a rough surface is left to be sub- <|uently set. In the latter case the surface must be .»ell wetted with water and scrubbed before the final coat is applied. Soap solution may also be used fop rough framing, such as soffit boards, but soap should not be used for fine concrete or a finished surface, as it leaves a film of grease which has a tendency to prevent the cement adliering when clearing up or raak- ing good the finished stirface. As the worlt of fillinp [)roceeds, the surface should be brushed over with a slip, that is, neat cement, to fill up all angles, and ohtiiiu a surface fro*' from "bulbs" and ragged ar. rises. The coarse concrete for rougliing out the stairs is composed of 1 part of Portland cement and 3 parts of coarse fireproof aggregate. Tliese materials must be ganged stiff and laid in small portions of About a pail- ful at a time, taking care to thoroughly cor olid.ite by ramming and beating with a wooden malk ., using a wooden punner or punch to get into the angles and deep part.^. When tlie first layer, which may be about li inches thick, is rammed, another layer is deposite«l and rammed, and so on until the rough stuff is within 'i- mm 402 CEMENTS AND CONCRETES i/o inch of the line of tread. It must not be omitted to brush the strings, treads and nosing moulds with slip as the work proceeds. This is most effectually done by the aid of a tool-brush. Care must be exercised when ramming stairs with mallets or punches that tin* mallet or other implement used is not too lar<,'o or too heavy, for it would most likely cause the frjimin«r to bulge out, and the form of the work would be irre- trievably spoilt. During the operation of ramming some of the water and a part of the constituent of tlie cement is forced upwards, and leaves a thin, smooth, clayey film on the surface, which prevents the adhesion of the next layer. For this reason the successive lay- ers should be deposited before the previous one is set, and the topping should be laid while the coarse con- crete is yet green. Too much stress cannot be laid upon the importance of topping the rough coat while it is green. This is one of the secrets of success of solid and strong work, so no more rough stuff shoiUd be laid than can be topped befor j the rough is set. The fine stuff for the topping is the same as for Eureka paving, viz., 1 part of cement to 2 parts of fine aggregate, gauged firm and plastic. The tread is made level and fair by means of a running mould so formed that it bears on the nosing moulds above and below tlu' tread. The mould has a metal plate or "shoe" fixed 80 as to run and form the tread. The shoe projects Bo that it will work under the riser board close up to the concrete riser. Illustration No. 23 shows a sec- tion of steps with the mould in position; also a sec- tion of the nosing mould and soffit boards and car- riage. The end of the slipper next to the wall is cut short to allow the mould to run close up to the wall. A HOW TO USE THEM 403 sec -ion of a T iron is shown as sometimes used as an in* tergal support. Iron is used for long steps, or where s^ii'Vs are intended for heavy trafSc. Iron helps to sup* 1 —Sections op Framin RING Mould in Position. Na Si. ^rt the concrete until set; it is placed in alternate steps, or in every third or fourth step, aceordinu: to the lengty. of step. Ordinary sized steps require no iron iivty y- .{' ,11" P ^* i'j ^ im nm 404 CEMENTS AND CONCRETES unless as a support for the concrete while green, and during the process of making. Finishing Stairs.— When the treads are firm afUT being run, the upper part of the nosing moulds are removed, the surface and joists trowelled off. The ad- vantages of having the nosing mould in two parts will thus be seen, as it allows the joint at this most notice- able par+ to be neatly cleaned off while the work is green, i'he lower part of the mould will support the concrete nosing during the finishing of the tread and until the conci^te is set. If the work is done with a nosing mould in one piece, which necessitates its being left on until the concrete is set, the joint has then to be filed down and stopped, and however well done, has a patchy appearance. When the treads are finished, and the work set, but not dry, the riser and string boards are taken off, the joints made good, and the returned end of the steps cleaned off. If the stuff has been properly gauged and rammed, there should be little or no making good required, but it is important that if necessary it should be done while the work is green. A thin layer of neat cement will not adhere on a dense and dry body of concrete. The only way to obtain perfect cohesion is to cut the damaged surface out to a depth of not less than i/t inch, then thoroughly wet it, brush the surface with liquid cement, and fill it in with gauged cement. No traffic should be allowed on the treads during the process of setting and harden- ing. The work is further protected and hardened by covering with sacks kept wet for several days by fre- quent watering. Where there are several flights of stairs to construct, there should not be less than three sets of strings and riser boards, which will enable the HOW TO USE THEM 405 carpenter to fix one set while the plasterers are filling in and cleaning oflF the others. Non-Slippery Steps. — Incessant traffic tends to make the treads of steps more or less slippery. In order to obviate this, the surface is indented with a concrete roller, similar to that used for some kinds of pavinjr. Another way is to form three or four V-shaped grooves from 1 inch to 2 inches apart on the treads while the concrete is moist. Another way is to insert leaden cubes about 1 inch square from 2 to 3 inches apart in the surface of the treads. Well-seasoned, hard wooden blocks, about the samo size as the lead and fixed in a similar way, keeping the end grain vertical, are also used for this purpose India rubber and cork cubes may also be used. Striking Centrings. — This should not be attempted luitil all the other work, with the exception of finishing the soffits, is done. It will be understood that the framing can be arranged so that the string and riser boards can be taken oflF without disturbing the soffit centring, which is kept up as long as possible. The time for striking centring greatly depends upon the class of cement used, the manner of gauging and lay- ing the concrete, and the temperature; but generally speaking, centring should not be struck for at least ten days. A stair between the walls can be struck much sooner than one having only one bearing by which its own weight is carried. I have seen a stair, with steps projecting 3 feet 6 inches from the wall, cleared of all supports in five days from the time of filling in ; but this was with good cement, gauged 1 part to 2 of aggregate, and in warm weather, and the stair was strengthened with T iron. 'U^ ^ 406 CEMENTS AND CONCRETES im The centring and framing for a flight of stairs should, where practicahle, be independent of other stairs above or below, so that they can be struck in due rotation. The wedges of the main props should be gradually witlidrawn. This tends to avoid the sudden jar which otherwise often happens when the centring is too sud- denly struck. The sudden removal of centring and the inflexible nature of concrete are the cause of body cracks. The damage caused by the sudden jar may not be seen at the time, but it will be eventually devel- oped by the force of expansion, which alwi..v . finds out the weak spots. Concrete and Iron.— Iron pipes, bars and T pieces are sometimes used with concrete stairs where the steps are long, or where landings have little support from walls. They help to carry the dead weight until the mass is thoroughly set, and also prevent sudden de- flection if the centring is struck too soon. When iron pipes are used for steps they shouid go right into the wall chase. Iron T pieces are used for long landings. Care must be taken that, if the iron is used, no part should be left exposed. It must be embedded in the concrete to protect it from oxidization and the effects of fire. When iron girders, etc., are partly exposed, they should be painted. Iron bars or pipes are occa- sionally used to strengthen the outer strings of spandrel stairs. The iron is laid in the moist concrete :. ar and along the string, having the ends projecting into the walls or landings. Angle irons are often used for unsupported concrete angles. Iron pipes, bars or joists are used as integral supports for landings and floors having unsupported ends. The tensik strength of bar iron is materially in- HOW TO USE THEM 407 creased by twisting. A bar Vs inch square with three twists per foot will gain about 50 per cent, in tensile .streii^xth when embedded in concrete, and give a corre- sponding strength to the concrete. A combination of iron and concrete is of special service where space is limited. For instance, if a beam or landing recpiires a certain thickness to carry a given weight, and it is inconvenient or diflRcult to obtain that thickness, the requisite degree of strength with a reduced thickness , may be obtained by the combination of both materials. This gives the combined iron and concrete a useful ad- vantage over stone. It is important to secure the full strength of the iron, and that none be lost or neutral- ized. In order to obtain the full strength the iron should be judiciously placed. Thus, a piece of iron surrounded by twenty t'mes its sectional area of con- crete would increase the weight-sustaining power of the iron in the centre and would have its strength in- creased about twice. If the same quantity of iron was placed in several pieces, so as to throw as much tensile strain on the iron as possible, the strength would be increased nearly four times. In order that none of the strength be lost or neutralized, the iron shoidd be placed near the lower surface; if fixed higher, they are nearer the axis of neutral stress, and are correspond- ingly less effective. The use of iron in concrete is in- valuable for many constructive purposes, but for gen- eral work, unless as a temporary aid and in a few ex- ceptional cases, it is unnecessary. For all other things ])eing equal, the huge board of reserve strength in good concrete is alone suflRcient to sustain as great if not a greater weight than that sustained by natural stone. No other artificial compound exceeds the strength i»f the I! m =!?. 408 CEMENTS AND CONCRETES 1 m§-[' 1 ti. 1 HB'- n ^I^^^E S* m natural substance, as does artificial stone composed of Portland cement concrete. Setting Concrete Soffits.— The soffits of stairs and landings, if neat cement has been used on a water- proof centring, as already described, only require a lit- tle stopping and coloring, but for work done on rough centring a setting coat has to be laid. This is usually done with neat Portland cement, though it is frequently 4rauged with lime putty to make it work more freely. The surface should be well roughened and wetted, to give a key and obtain perfect cohesion. It requires great care and time to make a good and true surface with Portland cement on a body of concrete, esp«'- cially if the concrete is dry, which is generally the case where there are several flights of steps in a stair- case, and the setting of the soffits and landings are left to the last part of the work. I have obtained equally good results by using Parian or other white cements for setting the soffits of staircases. When using white cements for this purpose it is better to brush the concrete surface with liquid cement before laying the gauged cement. The laying trowel should follow the brush, or at least before the liquid cement dries in. This not only secures better cohesion, but tends to prevent the setting coat peeling when trowel- ling it off. Soffits are sometimes set with gauged put- ty. This 'is like putting a beggar on horseback, and the Avork is never satisfactory. Fibrous Concrete.— As already mentioned, canvas and other fibrous materials may be advantageously used with Portland cement for several purposes. Can- vas forms a good ground for a setting coat on concrete surfaces. It gives a uniform and strong key, prevents HOW TO USE THEM 409 surface cracks, and the final coat from peeling. Coarse canvas cut to convenient sizes is used. It is laid on the centring, and held in position with tacks, or with the same kind of cement as intended for the final coat. Tlie canvas is then brushed with liquid cement, and then the concrete is laid while the canvas is moist, so that the whole will form one compact body. When the centring is struck, the fibrous concrete surface is rough- ened with a sharp and fine drng, so as to raise the fibre of the canvas, thus giving a fine, regular and strong key. This surface requires less material for the final coat than the ordinary concrete surface. If tacks are used they must be extracted before the final coat is laid, to avoid discoloration. The rough concrete and the white surface coat may also be done in one opera- tion. The centring is made fair and smooth, and then oiled with chalk oil. The white cement is gauged siifl: and laid on the centring. Coarse canvas is then laid on and well brushed with liquid cement. When this is firm (but not set) the surface is again brushed, and then the concrete is laid. The concrete is deposited in two or more layers. The first must not be too thick, taking care that it is well rammed or pressed on the moist canvas surface without disturbing the white ce- ment. After the centring is struck any defects on the surface are made good. The surface may be then left white, or painted, or polished as required. Polished Soffits. — Soffits, landings and strings of con- crete stairs that are finished in white cement may be polished. The material may be tinted, or left in its natural white or creamy color. Polished cement work is always bright, and has a lustre like marble. Be- ing diirable and easily cleaned, it is more sanitJiry and ;j i^^ 410 CEMENTS AND CONCRETES cheaper than paint. The polishing is done the same way as described for "white work." Concrete Staircases and Fibrous Plaster.^Fihroxxa plaster is well adapted for concrete surfaces when an enriched finish is desirable. I have introduced this material for decorating the soffits of steps and land- iups; also the strings of concrete stairs. By this method tlie soffits may also be enriched, and strings can be jianelled, or enriched with medallions or foliage, as re- quired. The soffits may also be enriched with modelled work done in situ, with some of the white cements, or with plaster and tow. The strings may be decorated -.vith hand-wrought gosr- ). In order to obtain a fixmg or keying substance that will receive nails or screws to sustain the fibrous plaster, a rough plan of the de- sign, or rather the fixing points, is set out on the in- side' of the centring before the concrete is laid. On the.se plans wood plugs, fillets or concrete fixing blocks are laid, and held in position with nails, plaster or ce- ment until the concrete is laid and set. Care must be exercised when fixing the plugs or fillets that the centring will leave freely without disturbing the plugs, etc. Doivel nolcs.—Cutimg dowel holes in concrete to receive iron or wood balusters is a slow and tedious process. They are best formed by means of wooden plugs, which are fixed before treac's; the plugs are driven into the rough concrete befor. it is set, leaving them flush with the line of tread, so that when the topping is laid they will not be in the way. Plugs are best fixed by the aid of a wooden gauge. The gauge is made the same thickness as the topping, the fength being equal to the distance between the nosing HOW TO USE THEM 411 mould and the riser board, and as wide as will admit of plug holes and the plugs to be driven through. The plu;,'s are made a little larger than the baluster ends to allow for the lead. The gauge is laid on the rough concrete, using the returned nosing as a guide, and then driving the plugs flush with the top of the gauge. The gauge is then lifted up and laid on the next step, and so on until the finish. This method is accurate and saves measuring and marking the position of each hole on every step. When balusters are fixed on the ends of the steps, the plugs are fixed on the inside of the outer string. The plugs are generally left in until the balusters are ready for fixing. A ready method for forming "lewis" holes or other undercut sink- ings in concrete is performed by casting wedge-shaped blocks of plaster of the required form and size, and then laying them in the desired positions while the concrete is soft When the concrete is set, the plaster blocks can then be easily cut out, leaving the under- cut sinking as desired. Summary of Staircases Constructed "in Situ."— It will be seen from the foregoing that the operations em- ployed in the construction of concrete staircases formed m situ are: (1) setting out the stairs and landintr; (2) fixing the wood frai-^ing; (3) gauging the materials and filling in; (4) removing the framing; (5) cleaning up the treads, risers and strings; (6) striking the soffit centring and finishing the soffits; (7) protecting and wetting the work until set and hard. Cast Steps. — Staircases are also constructed with steps cast separately, and then built in, in the same way as stone. Illustration No. 24 shows various sections of steps. Fig. 1 is a spandrel step, which may be used .i ^ 'f 412 CEMENTS AND CONCRETES for model dwellings, factories, etc. The tread is grooved to afford a good footing and prevent dipping. The dotted line indicates a square seating or tail-end of the step, which is embedded in the wall. Fig. 2 is a square step. Pig. 3 is a step with a moulded and returned Fig. I. Fig. 3. Fig. 3. Fig. 4. Skctions ok SrsHi NO. 24. nosing. Fig. 4 is a similar step, but having a moulded soffit. For cast work these steps must have a square seating or tail-end, as indicated by the dotted lines on Fig. 1. so as to bond into the walL TSBADS AND RISERS. NO. 25 Treads and Risers. — Stairs between walls are some- times formed with treads and risers. The treads and risers are cast and built in as the construction of the work proceeds. Sometimes they are let into chases and pinned after the walls are built. Illustration No. 25 ihows a section of treads and risers. HOW TO USE THEM 418 Closed Outer Strings. — Staircases are sometimes fin- ished with a close outer string, which prevents dirt or wet falling into the well. Illustration No. 26 shows the section, Fig. 1, and the elevation, Fig. 2, of a moulding outer string. The dotted line at A indicates a dowel hole for the balusters. Outer strings, whether plain or moulded, are much stronger when formed in Fig; r. NO. 28. w\ i- if' ■ situ. This is best effected by fixing a reverse mould at each side, then filling in the space from the top. The top is finished by hand and the aid of a template. The dowel holes are formed as already described. Concrete Floors. — It has been mentioned that the Romans, in the time of Julius Caesar, were in the habit of constructing their floors and roofs, as well as their wnlls. of concrete. According to an article in Arehaeolo- gia, the cementitious agent was pozzolana. The lim© \'m ■H ■ft 1 414 CEMENTS AND C0NCBETB8 was obtained by burninR ' ' travenitine. ' ' The aggreRnte usually cimsisted of broken tufa for walls, of broken lava for foundations where jrreat Htrenjrth was re- quired, and of broken pumice where lightness was es- sential. The tloors were ». orally constructed of liiry.' slabs of concrete, supported o» sleeper brick walls. The upper surface Avas finished with u layer of liner concr.'te niul mosaic. The roofs were uuule Hat, r.'st- in^' oti brick pillars. The first known Knulish patent fin'pniof (ronstruction was obtained by one Uekins Hull, in 1():}:{; but as at that period patentees wen- not com- IH'll.'d to disclose what the'r patents covered, no de- scription of the materials and methods can be jriven. Up to the middle of the elKhteenth century fireproof floors usually consisted of brick arches, but owinj? to their prent Weight and cost, were seldom used. But towards the close of M.al , ^vUicy cpst-iron Jiirders hiuI segmental brick arches were gradually comiuK into use where strength was essential. Up to a century ago plaster was largely employed as a floor material. In 1778 Karl Stanhope invented pugging for rendering wooised for fire-resistin>,' structures. Cast concrete is nsereiidinf,' from one compartment to another; to gain additional strength, so as to avoid as far as possible lateral thrust on the walls, and to secure the buildinir from attacks and effects of both dry rot and damp. Tiiere have been about a hundred patents for fireproof floors during the past generation, of which about five or six survive. Plaster Floors. — Plaster concrete, that is, plaster and broken bricks, or similar aggregates, also neat plaster, were at one time used largely f<»- the formation of floors. The use of plaster floors i common in some ago the rough plaster, as in general use where > III districts, and known a! up to a century floor plaster,' 416 CEMENTS AND CONCRETES ..ypsum was found in abundance. Plaster floors were rarely used on the ground level, because they could not resist moisture, which caused them to become soft and retain the damp. They were principally used for up- per floors. The gauged plaster w s laid upon reeds These reeds were spread upon th tops of joists, and over them was laid straw to keep the soft plaster from percolating through the reeds. The floors were about 3 inches thick, floated fair, and finished the following day Wood strips were placed around the walls, and dr'awn out when the plaster began to set, to allow for ♦he exnansion of the plaster. The materials bemg so li.Tht the timbers were less in size and number than those now in use. The joists were in some instances .31/0 inches by 2V-> inches, fixed wide apart, and sup- ported by small b^ams about 41/, inches by 3 V. inches. Tlie undersides between the joists were made fair by plastering the reeds, but in the better class of work the ioists were covered with reeds, and held in position with oak laths, and plastered. Bullock's blood was used to harden the floors after they were dry. In some in. stances they were coated with linseed oil to increase their hardness. Their use is now practically super- seded by Portland cement concrete. Joist Concrete Floors.— For this form of floor the concrete is laid between, over and under the iron joists Beyond the supervision of the fixing of the centring and the gauging of the materials, little skilled labor la required. The rough concrete is laid between and partly under the iron joists vhich are fixed from 3 feet to 5 feet apart, according the span and strength of the joists. The centring i .^upnorted, or rather hung bv the uid of timber laid acros ae joists and secured HOW TO USE THEM 4X1 \,,- Tc]ts. The materials are generally Portland ce> ment ano gravel,, coke-breeze, clinkers and broken i.ricks, c» uged in the proportion of 1 part of matrix ^0 ■> of aggregate. Sand equal to one-third of the bulk shoixld be added. Coke-breeze is weak, light and elastic, but combustible and porous, A mixture of gravel and breeze in equal proportions is bette^- than either alone. The proportion of cement varies accord- ing to the span and class of aggregate. All other things being equal, the strength of concrete is influ- enced by the strength of the aggregate, so that it would take a greater proportion of cement to make coke-breeze concrete equal in strength to a concrete made with hard aggregate, such as granite, slag or brick. The upper surface of this class of floor may be finished with wood, tiles or fine concrete, as re- quired. Joist concrete floors have been largely used. This is principally owing to their supposed cheap- ness, but it is more than probable that, in the event of fire, they would be dear in the end, because the lower part of the flanges are barely protected from the effects of fire, as the concrete, being thin at these parts, and also on a comparatively smooth surface, would soon crack or scale off, and leave the flanges of the joists exposed to the ravages of fire. They are also more or less conductors of sound. Caminus concrete cement is an excellent material for the construction of fireproof ceilings and partitions. Caminus Concrete Cement. — This material is specially designed to produce a hard and practically indestructi- ble concrete for the construction of fireproof floors and walls. It is manufactured from a waste product, and all inflammable material, such as coke-breeze, being en- m :-;H t m I 418 CEMENTS AND CONCRETES • tirely dispensed with, the concrete is thoroughly fire- resisting It is lighter and much cheaper than Port- land cement concrete, and is perfectly free from ex- pansion and contraction whilst setting. It can be man- ufactured to set in a few hours, so that the centres can be struck the day after the floor is laid. It can be supplied in a ready aggregated condition, so that the bags may be hoisted direct to the floor where the con- crete is being laid, and gauged on the floor, thus sav- ing a great amount of waste, and also labor in handling, mixing and laying. Concrete Floors and Coffered Ceilmgs.-A method was patented by E. Ransom for decreasing quantity ot material and yet obtaining equal strength in floors. The floor is divided by a series of beams at right angles to each other, so as to form a series of coffers in the ceiling For instance, for a floor 12 inches thick, the floor proper would be about 4 inches thick, and beams about 3 inches thick and 8 inches deep— a rod of twist- ed iron being placed in the centre of the thickness, and near the lower surface of the beams. The beams are generally about 2 feet 6 inches from centre to centre. The method of construction is as follows: First, form a platform or centring; on this a series of core boxes 2 feet 3 inches is placed, 3 inches apart, so as to form a 3-inch beam. The core boxes must be tapered and their upper edges rounded, so that they will draw when .he centring is struck. The size of the core boxes may be altered to suit the size and requirements of the floor With regard to the iron bars, the inventor says : "It is of vital importance for the strength of the struc- ture that the iron bars be placed no higher in the beain than calculated for; thctt the longitudinal centre of HOW TO USE THEM 419 these bars should be at the lowest point ; and it is ad- visable that the bars curve upwards slightly and uni- formly each way from the centre to the ends, so that the ends are from 1 to 3 inches hijrher than the cen- tres. By preparing the concrete bed on a Cf^rrespond- ing curve, the natural sag of the bar, as it is being handled to its place, gives all the requisite facility to accomplish this purpot . No crooked or irregular twisted iron must be used; otlierwise, when the strain comes upon it, it will perforce straighten and lengthen out, and weaken the structure in so doing. After placing the iron, the rest of the concrete is tamped in place, and the whole made to form a monolithic block. It is of vital importance that n& stop be made in the placing of concrete from the ti^^e the beam is begun until the thickness of the bea is in place and a 'through joint' is made. The v,eb and the thickness must be one solid piece of homogeneous concrete." Combined Concrete Floors o^ i Panelled Ceilings. — A combined floor and panelled ctiling may also be formed in concrete. This is executed as follows: First, form a level platform or centring, and on this fix the re- verse plaster mould, run and mitred, according to the design of the ceiling. The intervening panels are then made up with framing, and the concrete filled in the usual way, and when set the centring and reverse mould are removed, and the ceiling cleared off. If de- sired, a finely finished and smooth white surface may be obtained by coating the surface of the moulds and panels with firmly gauged Parian, or other white ce- ment, until about % inch thick, and when this is firm (but not set), the rough concrete is deposited in layers and tamped to consolidate the concrete, and unite it *- I 420 CEMExNTS AND CONCRETES with the white cement. The surface may also be fin- ished with fibrous concrete. The method of domg this, also for carrying out the above white cement process, is described in "Fibrous Concrete." „ . ^ ^ .,. Concrete and Wood.— Concrete floors finished with flooring boards require special care to prevent damp or dry rot There are various methods in use for fixing and keeping the flooring boards from contact with the rough concrete, one way being to fix wood fillets to the joists by means of wedges or clamps. Another way is to embed wood fillets or fixing blocks in the rough concrete, leaving them projecting above the level of the iron joists, to give a bearing and fixing points to the flooring boards; or fine coke-breeze, concrete or plas- ter screeds, may be laid at intervals on the rough concrete, onto which the boards are nailed. Fixing blocks, concrete or plaster screeds, are preferable to wood fillets, as they do not shrink or rot, and will better resist fire. All these methods leave intervenmg spaces between the concrete and the boards, and unless thoroughly ventilated, they harbor vermin, dirt and stagnant air. Unless the wood is thoroughly seasoned, and the boards grooved and tongued, dust and ef- fluvia will find egress through the joints. A portion of dust and water when sweeping and washing the floors also finds egress through the joists; and as the concrete will not absorb the water, or allow the dust to escape, they accumulate and become unseen dangers. These sanitary evils may be obviated, or at least reduced to a minimum, by laying the boards direct on the con- crete This not only forms a solid floor with no inter- spaces, but admits of thin boards being used with as ipuch if not greater advantage than a thick board. HOW TO USE THEM 421 There is no uneven springing between the joists, which causes friction and opening of the joints, and the whole thickness is available for wear. There is also less total depth of floor, consequently less height 'f building and general cost. Another important advantage of a solid floor is that it will resist fire better than one with hol- low spaces. It is here that the sponginess and elasticity of coke-breeze concrete as a top layer is of special service, and where it may be utilized with advantage. Owing to its being able to receive and retain nails, the boards can be nailed at any desired place. Wood blocks for parquet floors can also be bedded or screwed on the concrete surface. Flooring boards will lie even and solid on this surface, and if a thin layer of felt or slag-wool be spread on the concrete before the boards are laid, a firm and noiseless floor is obtained. Slag- wool is an imperishable non-conductor of heat, cold and sound, and it will not harbor vermin. If the work is in humid climate, the coke-breeze surface when dry should be coated with a solution of tar and pitch, to prevent atmospheric moisture being absorbed by the porous coke-breeze. Concrete Drying. — To prevent dry rot It is of the ut- most importance that the concrete should be thoroughly free from moisture before the flooring boards are laid and fixed. The drying of concrete is a question of time, which depends upon the amount of water used for gauging, the thickness and the temperature. It may take from three days to three weeks or even three months. The drying can be accelerated by directing currents of hot air on the lower surface, or by laying some absorbent material, such as dry sawdust or brick dust, on the upper surface. As soon as the surface m ^ f ■'.'.i 422 CEMENTS AND CONCRETES „„istnre is absorbed, or the dry material has no further .hsorbent power, it should be removed tojiU^w the ,„„ss to be air dried. Another way is to !«>' J^-' ^"^^ two ooats. and to allow one coat to dry be ore the ther is laid. For instance, if the floor is to be 6 hhes thick, the first coat is laid with rough but on. concr;te, the a..ro.ate being the best available; but talcin.^ Jiravel and coke-bree/e to be the most lit u i"t will be best to assimilate and combine t^- ■^: od <,u.;iities of each to ..lalize the- defects b^iiux- ■u. them in e^ual proportions. I brick plentiful vid broken to properly graduated sizes, it mU gut ; er esults than gravel or breeze. The mixed ag^ ..n-ate is gauged 5 parts to 1 of cement, and laid 4/, i, hes thicJ a^d gently but linnly beaten in situ, the r^^Jetingleft^oughtogiveakeyfor^ie^^^^^^ .oat Th-. second coat is not laid until the tirst is ..and consists of one part cement to 5 of si ted and nined coke-breeze, gauged stiff, and laid IV, mches th"k, beaten in situ, ruled level, and any ridges being aid air with a long hand-li..at. The moisture ot the second coat, by reason of the density of the firs coat 11 onlv be absorbed to a small degree, while the "reater portion will be taken up by the atmosphere and enable the combined coats to dry sooner than if ;,., in one. The fir.^t coat should be laid as soon as the roof is on, so as to give all P^^^le tnne for to drv, and the second eoat to be laid and dried before the flooring =s laid. When coke-breeze is not avail- able for the second coat, use s<,ft brick, broken to pass hrough a 3-16-inch sieve. The method of laying floors in two coats is only given as an alternative plan, and as an example of a p.-css used in some parts. Greatei HOW TO USE THEM 423 strength, as a whole, and more perfect cohesion be- tween the two coats, is obtained by laying the second coat as soon as the first is laid, or at least while it is Concrete Slab Floors. — The term, slab floor, is applieil to a concrete floor formed in situ, and in one piece or slab. It must not be confounded Avith slab pavements, which are constructed with a number of small cast slabs. Slab floors are usually made without exterior iron supports, but in a few instances iron T pieces or bars have been used as internal supports. lJeann isolating the floor ends from the walls. This is done by forming expansion partitions or linings in the chases, the lining^ befng composed of slag, felt or wood shav- ings, straw, reeds or other compressible material. The chSe shouid be sufficiently deep to allow for a com- pressible lining about IV2 inches thick, and a fair U^ L the slab floor. Care must be taken to ea^e a U^^^ half bricks solid at intervals, say trom 3 to 4 Ioh. HOW TO USE THEM 425 apart, to support the upper walls until the floor is set. Compressible linings may be used for floors supported on corbelled ledges; and when the expansion, and in many cases subsequent contraction, has finally finished, the linings can be taken out, and the vacant space filled up with fine concrete, or utilized as a ground key for cement skirtings. If girder or iron posts are iso- lated from the walls by means of compressible linings, the efl'ects of expansion and sound are limited. In some instances a judicious use of iron may be made. P'or instance, large areas may be divided with three or four rolled iron joists, so as to form shorter spans or smaller bays. Joists tend to bind the walls together, and to serve as scaffold bearings for building the upper parts of walls. They may also be used for hanging the centring on instead of strutting, or as aids to the strutting. Joists may also be used as integral suj)- ports at unsupported ends of concrete floors. They should be so fixed that the lower flanges are not less than 1 inch above the lower surface of the concrete. The whole strength of iron is brought more fully into use by fixing it near the lower surface. If fixed near the centre, or at the axis of neutral stress, a correspond- ing part of the strength is comparatively of little value. Construction of Slab Floors. — Portland cement as a matrix is indispensable. The unequal nature of gravel and coke-breeze renders them unfit and unsafe aggre- gates for this class of work. Broken brick being cheap, and obtainable in most districts, affords a ready aggre- gate, and may be used with safety and success. In ordinary cases of concrete construction, the whole thickness is usually made with cne rate of gauge ; but U t "■ 426 CEMENTS AND CONCRETES ,o,. slab tioorK covering lar«e areas, a^^ u^^^^^^^^^^^ bv iron or oth^r supports, exceptional strength is re 'ni Stronger results are obtained by making up i whole thickness with difTorent rates of gauge. Tak^ . the usual gauge for Hoois as from 4 to ^.parUot „,.,regate to one of cement, and used for the .hole thU-km-ss, it gives an uuequal strength a 1-^^^" ^^^^^ is comparatively of little use especially ^t the ne^tra^ .xis; but if the cement is divided so as to form an .....Hnary coat in the centre, and stronger coats tt^^^^^ upper and lower surfaces at the points o greatest : a n, the upper being compressive and the lower ten^ sive a better and more accurate arrangement of strength and allowance for disposition of strains is ob- t lined The additional strength at the proper placc^ Obtained not only by the use of add^tjonal c.^^^^^^^^ ,,ut bv the method of construction, which enables tl. ne quantity of cement as gauged for the usual rac for firming the whole thickness m one coat to : used more profitably. Take the section o ; iron joist as an example; this gives divided vet united strength, which sounds paradoxical but is true. The Hanges sustain the greatest strains, and the web comparatively little. With con- crete, the strong coats at the upper and lower surt^ics represent the flanges, and the ordinary ^^^^^^[^ As already stated, the increased and profitable cs- tribufion ci strength is obtained by tl--etlu>d o. con- struction. For instance, tnke a slab floor 20 feet bN 14 feet and 12 inches thick, without iron Jo'^ts <>j- ^the^ supports, and intended to cany a safe load of -J"^ c^*; T.er superficial foot, in addition to its own weight of sa> 1 ^.wt per square foot. This Hoor is laid in three coats. HOW TO rSE THEM 427 the first composed of 1 part cement and 2 of fine broken bricks trau}.'cd stiff, and luid 2 incJit>s thick; the second composed of 1 part cement and G of coarse broken ItriclvH jranucd stiff and biid and rammed 8 inches thick; and the third composc.l of 1 part cement and 2 of fine brolvcn bricks tran«,'ed stiff and hiid 2 inches thick. If the nppcr surface is intended for hard frictional wear a slitrlit ditVerence is made in the <;»iif:t' and nmtcrials. The ftrst coat i» composed of 2 parts of cement and 5 of fine broken bricks jran^'cd stiff and hiid 2 inches thick; the second of 1 part cement and 6 of coarse broken bricks «:anj:ed stifT and laid and rammed till 8 inches thick : a'lid the third coat composed of 1 part cement and 2 of fine cnished slai; or ixranite. It will be seen that this constrnctive method jjives the desired positions of stren;:th and the total .piantity of cement in the nnited i,'aiii.'cs is 1 part to 4. and \ii) to 5 parts of aj:^'rej,'ate. The tine broken bricks shonld be passed thronirh a V-^- inch siev<'. and the coarse thronsrh a 2-inch screen, takin<.' care that the latter contains a «rreater (|nantity of the smaller i>ieces than of the lar-er. It nujst be .•learly niiderstood that the second coat nnist be laid before the first is set : also that the third is laid before the second is set, so as to ensnre perfect cohesion be- tween each coat, and the absolute homou'cneity of the whole mass. Ilulldw Floors.— (in-nWv li^ditness in eoncreto floors is obtained by the nse .»f eoiicivte tubes. If the tubes are placed apart and in tiie centre of the floor thickness, a hollow homojreneous conei-ete slab is formed. The vertical divisions between the tubes connect the upper and lower coats, as with a web of a joist connecting the upper and lower tlanges. The methord of construction i : i . ir. i 428 CEMENTS AND CONCRETES in -imple and expeditious. For example for a Hlal. floor 10 inches thick, first lay a coat 2 inches thick of the stronger and finer concrete, as described for the 12-inch slab floor, and when this is firm lay .. or b- inch tube, from wall to wall. Bed the sides with rough concrete, and lay another row of tubes parallel with W first row and about 2 inches apart, and so on until th.' floor area is covered ; then make up interspaces with rough concrete till level with the upper surfaces of thr tubes, and then cover this with a coat of fine concrete - inches tliick. Concrete tubes or common earthenwar.- drain pipes may be used. Half-circle pipes, laid on their side edpes, may be used to save concrete and •Aeicht in joist floors, etc. ^ , dmcrete Roofs.-ConcMv roofs require special can- to render them watertiKht. Subsidence in the brick work of new buildinps is often the cause of cracks on concrete roofs. The roof should have a good camber, to give greater strength and allow for the fall of wa- ter to the outer edges. The rough coat should be laid and well consolidated by ramming or beating, and then left for seven days (the longer the better) before the topping is added. The upper coat should be strongly gauged with fine aggregate, as in "Eureka." If pos.si- ble. the topping should be laid in one piece. If the area is too large to be laid and finished m one piece, the ioints of the bays should overlap This is done by rebating the screed rules, so as to allow one-half of topping thickness to go under a part of the nile and form an underlap or ledge about V> inch wide, and when the adjoining bay is laid an overlapped but .evel ioint is the result. Roofs exposed to the sun s heat should be kept damp for several days after being laid. now TO I'HE THEM 429 as joints nre nflfccted by tho hfat as well as by detlec- tion of centring or .siibsidfiice of walls. Compressible linitijrs or wood strips slKudil be used round the walls to counteract any cxpiinsion. All concrete roofs should have a cement skirtiii;;- G inches hijfh and 1 inch thick well keyed into the wiiils. 11' linings are not used when the topping is laid, tbf topping should be turned up on the walls, so as to form a rim, to prevent water get- iing between the nml" and the walls. Greater heat and damp-resisting {)owt is are obtained by laying the up- per surface with ^^-inch thick coat of special concrete, composed of 1 part of Portland cement, VIj part of slaked lime and 1 part of firebrick dust. This should l)t> consolidated with a hand-float, and finished fine and close with a trowel. Notes on Concrete. — When calculating the strength of Moors, stairs, etc., the following facts should be borne i.i mind: Portland cement, when new, is too hot; sets more rapidly and expands more than old cement. The finest ground cement is the best and strongest. The time in setting, and in which the maximum strength is attained, varies according to the age of the cement, the (juantity of water used, and the mode of gauging and the mean atmospheric temperature. The maximum strength of a briquette of mature cement is maintained, while one of new cement "goes back." A briquette of matured cement will stand a tension strain of 550 pounds per square inch, and a crushing weight of 6,000 pounds per square inch. A briquette of neat cement is more brittle than one of concrete. Briquettes mature more rapidly than thick slab floors. The adhesive strength of Portland cement is about 85 pounds per squa'-e inch. The adhesive .strength increases more -i U{ ill ■< t I 430 CEMExXTS AND CONCRETES rapidly than the cohesive. A mass with a^^^'-f^^e lar-e in proportion to its volume sets more rapidly than a mass with a small area in proportion to its volum. Masses subject to pressure set more rapidly and atta n greater hardness than masses not so pressed The average compressive strength of concrete is about eigV,. times its tension strength. The P-Port- of c pressional and tensional strength varies according ?he quality and quantity of the aggregate. The strength of concrete depends greatly o^^^^P^^Pf "" ^ {^^ ,r,al.rix and aggregate; also on ^^^^'''-^'' fj^l' ^^^, ter As regards bricks, it must be remembered that there is a wide difference between the tensile strength of hard well-burnt bricks and soft stocks. No bricks l:: 'strong as cement, the best kinds b.ng abou one-fourth the strength of neat cement Takmg the Tuge as one part of cement to 4 of broken brick, the Tength of the concrete will be about two-fifths of neat ll^nt, but for safe and practical calculations ^-^^^ be best to take the strength as one-fourth of neat ce 'Lt Square slabs are stronger than rectangular slabs Slab floors being homogeneous throughout the who e weight is a dead weight, and con«equcn ly there Tsn thrust on the walls. With regard to the live load or weight which floors should be constructed to carr^ , some difference of opinion exists. Hurst says that for dTeUings VA cwt... public buildings V. cwt .an^^^^^^^^^ houses and factories 2V2 cwt. are safe calculations Others assert that for domestic building. 1 -t^P- o^ would be ample for all contingencies. An American Tuthority states 40 lbs. is sufficient for ordinary pu^ poses The following tabl. shows the results of testa HOW TO USE THEM 431 of slab floors made without iron. The slabs were sup- ported all round, and uniformly loaded with bricks. Test op Slab Floors. No. IvenKth between Sup- ports, feet. Breadth between Sup- ports, feet. Thick- ness, feet. A(teln Days. Breaking Weight, in cwt. per sq. ft. Weight of Slub, in cwt. per sq.ft. Total Breaking Weight, in cwt. per sq. ft. 1 2 8 4 5 6 14.5 6.75 (t II 13.5 6.75 It .5 ii II II II 11 7 14 21 7 14 21 3. 2.76 8.88 1.07 2.51 2.84 .54 II II II II II 8.54 8.30 9.42 1.61 3.05 8.38 Cast Concrete. — Innumerable patents have been ob- tained for a combination of materials, also moulds for the construction of artificial stone. Among the many that may be mentioned is Ur. Ranger's system. He obtained a patent in 1832 for artificial stone formed with a lime concrete. The aggregate consisted of shingle, broken flints, mason's chippings, &c. The in- ventor stated that the best results were obtained by using 30 lbs. of an aggregate of a siliceous or other hard nature, 3 lbs. powdered lime, and 18 ozs. boiling water. No more of the materials were gauged at the time than were sufficient to fill one mould, as the boil- ing water caused the concrete to set very rapidly. This material, after fifty years' exposure is still sound and shows no sign of decay. No artificial stone equals, far less excels, the strength and durability, sharpness, and evenness of Portland cement concrete. This form of artificial stone is now extensively used as a substitute "fm f:.r. ..-If mm iii ill ip i m 4 ."A if CEMENTS AND CONCRETES for natural stone, for window heads, string courses, uircoTumns, copings, keystones, and many ot^her ar^h. tectural, constructive, and decorative features. Fig uret animals, bas-reliefs, capitals, panels, can be made n fine concrete with all the relief, undercut, and fine detail which distinguishes high-class ^-m -fe^^^^^^ work. Cast work has the adva^t^^e.^^^^^^YJ^Y^;^^ that any defect can be detected previous to fixing. The methods of moulding and casting various works are given in the following pages. „„„:„iw " Concrete I>re.sm^..-Architectural works, espec^^Uy large or plain parts, are generally cast in wood moulds. If there are ornamental parts in the blocks, a combina- on of wood and plaster, and sometimes gelatine is used for the moulds; wood for the mam or plain parts^ Lr for circular or moulded parts, and gelatine fj undercut parts. The plaster or g^^f ;°^' ^^^.^^^/^'^ may be, is screwed on or let into rebated parts of the wood Ornamental parts are sometimes cast separately :,::^hen fixed on the main cast. They may also b cast separately and laid into the main mould (face inwards) and the whole is cast together in a somewhat Zilar way to that described for "bedded enrich- ments" in fibrous plaster cornices. ,. ^ ^a Considerable skill and ingenuity has been displayed in the construction of wood moulds for castmg concrete Wocks for architectural purposes. Many methods have beTn employed for fixing the sides and ends together and ako to the bottom of the mould, leaving one or more parts unfixed to facilitate the release of the cast^ The primitive method is to fix the various parts o the mould with screws. This is a slow and unrebable process, as the continual screwing and unscrewmg for HOW TO USE THEM 433 each cast soon wears the screw-holes, and the sides be- come loose and out of square, causing the casts to get out of their true form. Hinges, also hooks and eyes, have been used for the same purpose, but they are liable to the same defects as the screws when subject to long iise. •Wedge Mould for Casting Blocks. MouLOBa Lintels, &c. NO. 27. Thumbscrews to fit into iron sockets are also used, but they are too expensive for ordinary work, and are unsuitable for small moulds. One of the most simple and reliable methods is the "wedge mould," invented by an architect. It is easily made, and expeditious in working. Even after long and constant use, the casts are always accurate in form and size. The wedges and the rebated ends allow the various parts to be correct- ly fixed and held in position. Illustration No. 27 shows the method of constrnetion. The various parts are 434 CEMENTS AND CONCRETES named, and the sketch is -"--P^^^'^^'martwotr moulds are extra deep, it is necessary to make two or "ore sets of tenons and wedges at each angle. When there are a large number of casts required the mould ends are strengthened by binding the Pro3ectmg end with hoon iron. This method has been adopted foi Ta ting a'lo'of blocks. Illustration No. 28 shows two useful kinds of moulds. Fig. 1 is ^ --Ple form ^f mould adapted for plain blocks ^^f ' ^^°*«^^' ^^^- ^'^J are the sides, which are grooved into the ends B, B, and Fig. 1. Fig. 2. NO. 28. held together by the bolts and nuts, C C, two on each side. The bolts may be about % mch diameter, with a good-sized square-head at one end and a washer and nut at the other. This, having no bottom, is termed a bolted frame mould. It should be laid on a bench o moulding board before the cast is filled in. Fig. ^ is Tseetion of a combined wood and plaster mould on the wedge principle, adapted for casting a strong course moulding. A is a moulding board, IV2 inches thick, formed with two or more boards; a is one of two or more cross ledges, 1 inch thick on which A, the jmind is nailed. B is a width board, 1 inch thick, which is HOW TO USE THEM 435 nailed &n to A. This gives a point of resistance to the plaster piece C and the side board G. D is a side board on which E is screwed. E forms the sloping part of the weathering. F is one of two or more vertical wedges which hold D E in position. The sockets for the wedges P are made between the cross ledges, so that the wedge will project below the ground A. This allows the v/edges to be more easily driven out when the east is set. G is the back or plain side board. H is a fillet, IMj inches square, screwed on to the ground A. I and J are two folding wedges, or, in other words, wedges driven in opposite directions. These hold G in position. Two or more of these folding wedges are re(iuired, according to the length of the mould. The sam6 remarks apply to the vertical wedges F. The lat- ter form of wedge is only given as an alternative. The end pieces are held in position by dropping them into grooves in a similar way as shown in the previous fig- ure, with the exception that the grooves are cut in the sides instead of the ends. K is a gauge rule which is used for ruling the iper surface of the cast fair. This may also be done by working a straight-edge longi- tudinally. The dotted line at L, the concrete, indicates the wall line. The level part of the weathering up to this line, or if splayed from the outer member of this line, must be finished smooth to allow the water to run freely off. When the cast is set, the wedges are with- drawn, and the sides and ends released. The cast is then turned over on its back end or top side on a board, and then the plaster piece and the wood ground is taken off. If the cast is green, it should be tum?d over on old sacks or wet sawdust, so as to protect the arrises, and avoid fractures. i 436 CEMENTS AND CONCRETES Illustration No. 29 shows a method commonly adopted for constructing moulds for sills and copings. Pig. 1 is the section of a mould for a window sill. A is the moulding board, made with two or more pieces, each 114 inches thick; a is one of two or more cross ledges, made with 1 inch stuflP, on which A is nailed. B is the width board, made of % inch stuff, nailed on to A. C is a block, I14 inches thick, which is nailed on to B. These blocks are placed about a foot apart, or no that they will carry the lining D, 1 inch thick, A Fic. I.— Section of Moi>u> roii Casting Sills. Fic. 2.— Section of Moui.n.roR Casting Coping. NO. 29. groove or an iron tongue E is made in B, and a piece of thick hoop iron or iron bar is placed loosely in th< groove before the cast is filled in. P is a fixed side. l»/4 inches thick. G is a fillet, li/4 inches square, nailed on to P, and screwed on to moulding board A. H is a loose side, II4 inches thick, on which the fillet I is nailed. J is one of two or more clips, which turn on a screw, and are used to hold the loose side H in posi< tion. These clips are made and used in the same way as described for fibrous slabs. As compared with wedges, clips are always in position ready for use, are HOW TO USE THEM 437 not liable to be mislaid, and when the fillets are fixed on to the side pieces, the clips keep the sides from rising as well as expaflding. K is a throating or water groove, which is formed in the concrete L, with a rule having a rounded edge. Two blocks, dished at the inner ends, must be fixed one at each end of the mould so as to form a stool or bed for the superstructure Tlie position and form of the groove is obtained from sink- ings cut m the end pieces of the mould. The end pieces are held in position by grooves cut in the side pieces m a similar way, as already described, with the excep- tion that the grooves are cut in the side pieces, instead of the end pieces. When setting out the mould, an extra length must be allowed for the side j.ieces for the grooves. A part of the upper ourface of the east (be- ing the part which projects beyond the line of wall) must be finished fair by hand at the same time as form- ing the water groove. This must be done while the cast IS green. When the cast is released from the mould the iron tongue will be found firmly embedded in the concrete. Fig. 2 is a section of a wood mould adapted for casting wall copings. A is the ground of a mould- ing board, which may be made of 114-inch stuff, and in - or more widths; a is one of two or more cross ledges 1 inch thick, on which A is fixed. B, B, are blocks about 114 inches thick, placed about 1 foot apart C C, are linings, 1 inch thick, nailed to B B D is a fixed side, 114 inches thick. E is a fillet, V/. inches square, fixed to D, and then screwed on to a" F is i loose side, 114 inches thick, on which is nailed the fillet ther mouldinf,' here siiown. A drip member, as shown at the top member of both cornices, is generally used for exterior mouUliims. to prevent the water run- iiiiij? over the wall surface. Kifr. 3 is the section of n wall coping and the castinjr m«»nld. M is the mould, a simdar one beiiif; used for the other side. A mould for this purpose is best f(»rmed with lloorins boards about I inch thick, and fixiii« them to._'ether as shown. The drip 1) is readily formed by sjiwinjr an inch bead throuu'h the centre, and nailinn it oil I he bottom. Two forms of brackets, li and H. are here ^'iven. One is eiit «)ut of the solid, and the other made of two pieces of wood nailed together. Fi^'. 4 is the section of » eastinR mould for a saddle- back copinp. R is a <|uarter-round piece of wood tixed ill the anple of the mould to form a cavetto, which is sometimes used in eopinj.'s. 1) is an anjrular-shaped drip, sometimes used in place of a circular one. T is part of a template used for forming the saddle-back of the eopinjjj. Fi«r. .^) is the section of a mould for a eoi.iniir with sphiyed or chamfered anjrles. S is a triaiiiridjir strip of wood tixed in the anirle .iiid the top of the mould to form the splays, and 1) is a circular drip. Concrete mouldin-js that are deeply undercut or iu- tricjite in profile mHv U.' cjist in situ by the use of the "Waste Mould Process." HOW JSE THEM 448 Modrllhifj in Fine Concrete. — Figures of the huinnn nml nnimiil form, also rriiblcms, trade signs, and build- inj.'M. jiiv now being made in fine concrete. The work may It. executed in situ, or in the moulding shop, and th«ri Mx«hI in position. For important works a plaster model is first made, and placed in position, so as to jiidire of iho effect b<'f<»ro committing it to the pernia- n«'tit material. For this purpose the model is first modelled in clay, and then it is waste-moidded. and a plasti'r east obtained. After the model is approved it is nn)idded, and then east in the fine concrete. The nuilcriiil is composed of Cortland cement, and a light, l)nf strong, aggregate; and the cast is made in a similar way In fluit described for easting vases. The material iiiiiy l»e colored as refpiired to suit the subj«'ol. The ifi'Mcral method of ex«'euting figures "on the roiuid" iti HiH" concrete or I'ortland cement is to model the liirnri' direct in the cement on an iron frani*'. and then to lix it in its permanent position. This is effected by first iriakiiig a full-sized sketch of the proposed figure, tin II si'tting out on this the form of the necessary iron- work to .serve as frame or skeleton to form an internal support. This iron frame also forms a core to enable the figure to be made hollow, and serves as a permanent support for thin parts and extremities of the figure. The rjuantify, size, and form of the iron frame is regu- lated hy the size, fonn, ami position of the figure. For iiista;iee. if the model of a f>dl-size lion is re(|uired. first juake a rectangular frame to suit the feet of the lion and the base on which ilie figure stands. The base frame is made " iron bars. I'j inches wide by 14 inch thick, fixed on edsre. Then set out four leg-irons, i\m\ connect them on the base frame, and then set out one . :«l 444 CEMENTS AND CONCRETES or two body-irons, and connect them with the leg-irons. After this set out a looped piece to fit the contour of the neck and head, and fix it to the body-iron. Now set out the tail-iron. This is best formed with an iron pipe, and it should be made to screw on to the body- iron. This allows the tail to be unscrewed when the model is finished, and screwed on after the model is fixed in position, thus enabling the model to be more freely handled, and with less risk of breakage when moving and fixing in its permanent position. Having made the frame, place it on a stout modelling board, keeping the base frame from 1 to 3 inches above the board, according to the depth of the base ; the frame being temporarily supported with four pieces of brick or stone. This is done to allow the base frame to bo enveloped with concrete. This done, fix wood rules, cut to the depth of the base, on the board, so as to form a fence on all sides of the base. Then fill in the base with concrete ; and when this is set, proceed with the coring out, so as to obtain a hollow model. In order to decrease the weight of concrete figures "on the round," and to enable them to be more easily handled and hoisted when fixing them in their perma- nent positions, they should be made hollow. This is effected by making a round skeleton frame with hoop- iron, or with wire-netting, for the body, neck, and head, and other thick parts. This metal skeleton must bo built on and securely fixed to the main iron frame. The whole, or parts of the figure, may also be cored out with shavings or tow, and held in position with tar bands or canvas strips, dipped in plaster. Tow is an excellent material for forming cores. By making up the inner parts with dry tow, and then dipping tow in plaster fot HOW TO USE THEM 445 the outside coat, the coie can be made to any desired shape, and also leave the necessary thickness for the concrete. To prevent the material slipping down by its own weight, pieces of iron or wood, in the form of crosses, are fastened with copper wire or tar rope to the iron rods, which are used as single supports. These iron or wood pieces must be fixed in all directions, and in such a way that the material is held up by them. For small extremities, such as fingers of human figures, beaks of birds, fins of fishes, horns and tails of animals, iron rods should be fixed on the main frame, and the parts to be covered with cement must be notched or bound at intervals with copper wire or tar rope. The distance between the core and the finished face of the figure is of course the actual thickness of the model. This thickness may vary from 1 inch to 3 inches, or even 4 inches at some parts. An actual thickness of 2 inches will be sufficient to give the requisite strength. When the core is made, cover it with a coat of Port- land cement and old lime putty, in the proportion of 3 of the former to 1 of the latter, and add sufficient tow or hair to give tenacity. If there are open spaces in the skeleton iron work, bridge them over with bits of tiles and cement. The whole surface, after being coated, must be well scratched with a nail, to give a key for the roughing out coat. This scratched coat must be allowed to set before proceeding with the actual model- ling. The stuflF for roughing out is composed of 2 parts of Portland cement and 1 part of fine aggregate. Crushed bricks, stone, or pottery ware passed through a sieve having a % inch mesh may be used as aggre- gates. The finishing stuff is composed of fine sifted Portland cement. The addition of a fifth part of old -t 446 CEMENTS AND CONCRETES lime putty to the cement makes the stuff more mellow, and works freer and sweeter. The modeUing is done as described for in situ work. The finishing coat can be colored to any desired tint, as already described. Concrete Fountainst—Fme concrete is an excellent material for the construction of fountains. It is ob- vious that a vast amount of cutting and consequent waste of material is involved in the executing of foun- tains, "on the round," when natural stone is employed. Saving of material, and a corresponding reduction in the cost, is effected by use of a material that can be easily cast, and is at the same time durable and im- pervious. These qualities combined are found in arti- ficial stone composed of fine concrete. Being readily made in large blocks (any sized basin can be made in one piece), there is no jointing required, as is the case with terra cotta, which is another form of artificial stone. Fountains composed of fine concrete are made in a similar way to that described for making and cast- ing vases. Concrete Tanfes.— Concrete tanks to contain water, and for a variety of manufacturing purposes, are now largely in use. They are strong and durable, and hav- ing" hard smooth surfaces, they are easily washed and kept clean. Being impervious to vermin, damp, and atmospheric influences, they are the coolest and most sanitary water cisterns that can be used. Cattle troughs are best made in conemte. Concrete tanks have been used as water and silicate baths for indurating con- crete casts, and during their constant use for over a decade no signs of cracks o- damp are visible. They were made in one piece, varying in si/e from 6 feet ui to 18 feet long, 3 feet to 7 feet wide, 2 feet 6 inches to HOW TO USE THEM 447 4 feet high, and from 3 to 4Vli inches thick. Some were cast, but the large ones were made in situ. The method of construction (for in situ work) being simple and ex- peditious, the total cost is small. For a tank 9 feet long, 4 feet 6 inches wide, 2 feet 6 inches high, and Sy^ inches thick, first frame up wood sides and ends to the above length, width, and height, then make inside boards, the lengths and widths being the same as above, less the tank thickness, and the heights less the bottom thickness. The sides and ends are hung by means of cross battens laid on the upper edges of the outside framing, and kept in position with inside stays. This leaves an open and continuous space at the sides, ends, and bottom. The constructive materials are 1 part of Portland cement and 2 of fine slag or granite, gauged stiff, and laid over the bottom. Next, the open sides and ends are filled up, taking great care that the whole mass is thoroughly consolidated by ramming. The stuff for the sides and ends should be laid in layers from 6 to 8 inches deep, each layer being well rammed before the next is laid. The angles are strengthened by inserting angle irons during the process of filling in. As soon as the concrete is set the inner boards are removed, and if the surface Is smooth or dry, it must be keyed with a coarse drag or a sharp hand pick. It is then swept and wetted to cleanse it r.nd stop the suction, so as to ensure perfect cohesion, and allow the final coat to retain its moisture during the process of trowelling and the stuff setting. The finishing coat is composed of neat cement, the finer ground the better, as percolation through con- crete made with a finely ground cement is less liable than when made with a coarsely ground cement. i 1! » -I I - 448 CEMENTS AND CONCRETES The final coat is laid about 3/16 inch thick, and pre- ceded by brushing the surface with liquid cement to f u up all crevices, and afford better adhesion between the surface and the final coat. When the stuff is firm, it is well trowelled to a fine and close surface. The outer boards are then removed, and the surface finished in a similar way. Concrete Sinks.— Concrete sinks can be made to any desired size or form. They are cast in wood or plaster moulds, and are composed of 1 part of Portland cement to 2 parts of fine crushed granite or other hard aggre- gate They are made with rebated holes for traps. The ordinary size are as follows: 2 feet 6 inches by 1 foot 8 inches; 2 feet 9 inches by 1 foot 8 inches; and 3 feet by 2 feet, all 6 inches deep, and from 2 to 3 inches thick. ' Garden Edging.— nam and ornamented edgings are now made in concrete. They are made in various lengths The most useful size is 3 feet long, 6 .nches deep, and 2 inches thick. They can be made to any curve, and tinted to any shade. Cmcrete Foscs.-During the last half-century thou- sands of vases, composed of fine concrete— commonly called "artificial stone"— have been used for the dec oration of buildin-s and practical use in gardens, con- servatories, &c. For vases that are cast in sections the thickness of large and open parts, such as the "body," are regulated by means of a plaster core, which is placed in the open mould. The contour of the core must be 80 arranged that the cast will draw from the core, or vice versa. For some forms of vases, the core must be made in pieces similar to a piece mould. The method of making, moulding, and casting— the latter by the aid of a template instead of a cora E ?! HOW TO USE THEM 449 Concrete Mantel Pieces. — Chimney-pieces of all sizes and shapes are now extensively made in fine concrete. They are generally made in wood moulds, plaster moulds being let in the main mould for ornamental parts. They are often made in colored concrete. Colored Concrete. — Concrete casts, also work laid in situ, can be colored to imitate any natural stone. This is effected by mixing mineral oxides of the required color with the cement used for the surface coat. The color coat should not exceed Vs inch in thickness, as oxides are too expensive to use for the entire thickness of the cast. The quantity of oxide to be added to the cement depends upon the strength of the oxide. Some are much stronger than others. Five per cent, of a strong oxide will impart a close resemblance of the desired color to the concrete, but a weak oxide will re- quire from 10 to 15 per cent., and even 20 per cent., to obtain the same color. Some of the red oxides range in color from scarlet or Turkey red, gradually deepen- ing to chocolate. Some oxides contain 95 per cent, of pure ferric oxide, Avhich is made from copperas, or, scientifically speaking, sulphate of iron. This is a by- product, and is frequently evolved from waste acid liquors at tinplate works, and is obtained in large quan- tities from South Wales. This kind of oxide is far more suitable for coloring concrete than ochres and most of the earthy oxides. Earthy colors, like Venetian red and umber, soon fade and have a sickly appearance. The oxides should be intimately mixed with the cement in a dry state before it is gauged. The mixing is gen- erally done by hand, but lietter resiilts are obtained by the use of grinding nuiehine. It is a safe plan to tr\ various proportions (tf color and eiMuent an«l giuige !i ft' '1 Pi V'' ' I ,T It' ' i •H; »!■ 11 I , If! % 450 CEMENTS AND CONCRETES small parts, and when set and dry select those most suitable for the desired purpose. All cast work, as soon as extracted from the moulds, should be exammed, and any blubs stopped and chipped parts or other mmor defects made good while the work is moist or green, using neat cement and colors in the same proportion as used for the surface stuff. Colored surfaces may be greatly improved by brushing the cast as soon as set with a solution of the same color as used for the sur- face coat. A color solution, made by mixing the color with water and a solution of alum, is very useful for coloring Portland cement, with or without sand. If this coloring solution is brushed over the surface while it is moist or semi-dry, a good standing color can be ob- tained without mixing color with dry cement. This method will be found useful for sgraffitto, &c. A novel and color-saving method, for coloring the upper surfaces of slabs or other flat casts, is eflEected by first filling in the mould in the usual way, then placing the coloVed cement in a dry state in a hand sieve, and then violently shaking or tapping the sides of the sieve, so as to sprinkle the colored cement uni- formly over the surface until it is nearly 1/16 inch thick. The surface is then trowelled in the usual way. The sprinkling must be done as soon as the main body of the stuff is ruled off, so as to obtain a homogeneous body. Another and a novel method which may be ad- vantageously employed for finishing slab or other large surfaces in a mould is as follows: A fine finished face is more readily obtained by using a smoothing knife (for brevity termed a "shaver") than by a trowel. A shaver is a piece of polished steel about 3 mches wide and % inch thick, the length being regulated according ;i -i HOW TO USE THEM 451 to the width of the mould, and allowing about 8 inches at each end for handles. For instance, for a slab 2 feet win^' PO>°t« for wire-lathing and fibrous plaster work. Floor boards may also be fixed to them. They are also bu.lt into brick walls for similar purposes, as well as for external M-all tilings. For ceilings, stair soffits, and laudmgs, tlie blocks are laid on the centrings where required, and permanently secured by laying concrete between and over them. For bearings and fixing floormg boards, they are secured flush. TYPICAL SYSTEMS OF REINFORCED CONCRETE CONSTRUCTIONS FROM VARIOUS SOURCES. Of the interesting features of modern civil engineer. injr, interesting because of their extreme m»v.lty nnd successful application, reinforced concrete is Probably most noteworthy because of its unique adaptability. How striking is the influence of steel reinforcemont is . best exemplified by a reference to Fig. 1. There twv HOW TO rSK THEM 453 beams are shown designed tt) carry ordinary floor loads, the one made entirely of eoiicrt'te and the other of con- crete with a sheet of expanded metal imbedded in tlie tensile portion of the beam. Tlic saving in mere weight of concrete alone is apparent; and when we remember that the adoption of floor beams entirely of concret" means an increase of thickness of nine inches or jis- suming five to eight floors, an increase in the total height of the building (with extra cost and heavier walls, together with heavier foundations to carry them) of from four to six feet, we see that even as regards initial outlay for materials, the introduction of settle reinforcement into concrete construction is of import- ance. So far as economy in initial cost of materials is eoii- cerned. reinforced concrete is undoubtedly cheaper than either concrete or steel alone. It is not very ejisy to demonstrate this economy except by comparative cost in individual cases, but an approach to a sy.stematie comparison has been made by Mr. Walter Loring Webb, as follows: A cubic foot of steel weighs 490 pounds. Assume as an average price that it can be bought and placed for 4.5 cents per pound. The steel will therefore cost $22.05 per cubic foot. On the basis that concrete may be placed for $6 per cubic yard, the concrete will cost 22 cents per cubic foot whieh is 1 per cent of th'j cost of the steel. Therefore, on this basis if it is neces- sary to use as reinforcement an amount of steel w hose volume is in excess of 1 per cent of the additional con- crete which would do the same work, there is no econ- omy in the reinforcement, even though the reinforce- ment is justified on account of the other eonsiderati.Mi.s. Assuming 500 pounds per .square inch as the workiny 454 CEMENTS AND CONCRETES compressive strength of concrete, and 16,000 as the per- missible stress in steel, it requires 3.125 per cent of steel to furnish the same compressive str-ss as concrete. On the above basis of cost, the compression is evidently obtained much more cheaply in concrete than in steel —in fact, at less than one-third of the cost. On the other hand, even if we allow 50 pounds per square inch tension in the concrete and 16,000 pounds in the steel, it requires only 0.21 per cent of steel to furnish the tig, i.-^The«e Bmuiu Are Designed to Carry the Mame Load. The Upper is of Reinforced Concrete, the Lower of Plain Concrete. same strength as the concrete, which shows that, no matter what may be the variation in the. comparative price, of concrete and steel, steel always furnishes ten- sion at a far cheaper price than concrete, on the above basis at less than one-third of the cost. The practical meaning of this is, on the one hand, that a beam com- posed wholly of concrete is usually inadvisable, since its low tensile strength makes it uneconomical, if not actu- ally impracticable, for it may be readily shown that, beyond a comparatively short span, a concrete beam will not support its own weight. On the other hand. HOW TO USE THEM 455 on account of the cheaper compressive stress furnished by concrete, an all-steel beam is not so economical as FU;. a.— Types of Steel Beinforcinflr Rods. a beam in which the concrete furnishes the compres- sive stress and the steel furnishes the tensile stress. •%• ••—A Reinforced Concrete Pier for Railway Traffic. This statement has been very frequently verified when comparing the cost of the construction of floors de- a-ii 456 CEMENTS AND CONCRETES Hicncd bv u«intf Hteel l-bonmM Hi.pporting a fire-proof o^r to'floor. and that cf « -ncrete floor mvm, a siX Hoor Hlab but makinc the beams as T-beams of ^^'r;:::f^r::;^-info-d concrete con«tn.c.io„ can be oM iued from Fi.. 3. which '. an -metr.ca pro- lection of ft portion of a pier strong enough to carr> ^t^."aviest railway traffic. The dispos.tum of tu Ht el work is shown in the pilen. the mam K.rders, a 1 W„«; and the manner in which the « - rod. n - ninir aloni: the tensile or bottom side of the jjirU.rH Td b"a ns are bent up over the top of the pde. wh.eh There the tensile meu.ber (the b..«m. bem.^ cont.nu- ous). mul then down a.ain to the bottom of the ^.rders and b.'iuus. is most instr.u-tiv.'. Pig. 4.-Method of Joining Colammi and Floon. The sections of the steel employed vary in different systems, beinjr round, rtat, ^^uare angle and tee-Fi^ o m all cases the simplest section is the best, as . ;osts less, and readily allows the concrete to be rammed into the closest contact with the entire surface of the armoring. In America the Ransome system is mos extensively used-a system m which a bar of twisted now TO rSK TIIKM 457 ■teel iM employed. Small Hertinns are better than larjff ones, for by their use we obtain a more uniform tlia- tribution of stress in the steel; we «'an also readily bend and work them info any rer|uired shape; and finaPy i . lost eeonomieal disposition <»f material is obtat'i. (i, tile m •' I bein»; placed at the maximum dis- tanci f'f()/t. f fic 1 '» iixis. m m Fig. 5.— The Monier Hyutem. Expanded metal meshinjr (PiR. 6) is increasingly em- ployed, more particularly in the lighter forms «>f con- struction. It consists of sheets of metal which have b?en mechanically slit an\ An improvement on . i il u I: I 458 CEMENTS AND CONCBETES ♦hi. 8V8tem is the Clinton method (Fig. 11) of using Itelec Sly welded wire netting in comhination w.th concrete. Clinton fabric consists of drawn ware of 6 to 10 gauge, which may be made m lengths up to 300 feet The system is therefore a continuous bond system, which prevents the entire collapse of a span unless the weight imposed is sufficient to break ah the wires. File. 6s-Expsnd«l Metal. Columns and Piles. -^in forced columns are made with either square, rectangular, or circular sections^ Thev are reinforced with from four to twenty rods, the d amet s of which vary from % to 2V, inches. The rodTare placed as nearly as practicable to the circum- ference of the column, so as to give the greatest radius ofZlLn for the section: but they are never placed so nell the surface ^hat they have not at ^east one or twoTnches protective covering. The steel so disposed .able to take up the tensile stresses wh.ch may be HOW TO USE THEM 459 induced in the column by eccentric loading, lateral shock, wind pressure, and the pull of belting. Columns and piles are made in wooden boxes, each consisting of three permanent sides and a fourth side which is temporary and removable. Under the patent rights of Francois Hennebique the reinforcing is placed ff(f.V.-i SjniMi «( InMtlBK in these boxes, and adjusted by gauges to within one or two inches of the sides. The concrete is laid and rammed, about six inches at a time, with small hand rammers. The open side of the box is built up by battens fitting into grooves in the permanent sides, as the work proceeds; this enables inspection of the work 460 CEMENTS AND CONCRETES to be mad.', and facilitates the placing of the ties at the proper positions. The ties are made of round wire 3/lB II FIf . S^Wood Centering and BweeBie Steel Bms for W^feot Floor Span. inch diameter and are dropped down over the top of the steel rods. They ar.' spaced down two-inch centres HOW TO USE THEM 461 at the bottom and top. to twelve-inch centres in the centre of length of tlie column, and are intended to I.revent the steel rods from spreading out under thci «ction of longitudinal loads. Fig. 4 shows the method <>! .loining columns to the Hoor. ! I i :^ Fig. 9.-Concrefe Power I'lant in Course of Construction. ;.*J •i teliM In the Ransome c<.lumns as .•xi-mplified in a recentlv constructed factory building (Fig. 7). the vertical n-- inforcement consists of round rods with the connections made about 12 inches above ti... ri.H.r line; in order that 'i| 462 CEMENTS AND CONCRETES these rods might be continuous the ends were threaded Ind connected with sleeve nuts, thereby developing the d strengh of the rods. Horizontal reinforcemen wa 1 used, consisting of hoops formed by a spiral n(. io.-SUdM of CMCteto EMdy «w «••'• made from V. ineh dminrter soft wire, havmR a pitch rsnacin. of 4 inel.es in the basement eolumna, and g^ JuaT/inereasing to a pitch of 6 inches m the top " AeeirtoMi'Mr. Henry Longcope the fi^t in.ovv tion In eoncrot. pile. »as the sand pile, produced br HOW TO USE THEM 408 driving a wooden form in the ground and withdrawing it, the hole being filled with moist sand well rammed. The next method adopted was to drive a metal form into the ground and after withdrawal to fill the hole with concrete. This was not successful, as it was open to the serious objec- tion that on withdrawing the form, the ground would col- lapse before the concrete could be inserted. Still another method was introduced, which consisted in dropping a cone- shaped five ton weight a num- ber of times from a consider- able height, in order to form a hole, which was afterward filled with concrete. This method never passed the ex- perimental stage. Coming to more successful systems we may mention a method of moulding a pile of concrete, allowing it to stand, and then driving it into the ground, a cap being used to protect the head. Of modem systems which have proven successful, Gil- kNreth's pile must first be re- "T^m I i 1 1 4«4 CEMENTS AND CONCRETES HOW TO USE THEM 465 corded. Oilbreth U8ed a molded corrujated taper pile, cast with core hole the entire length of the pile, which is jetted down by a water jet and finally settled by hammer blows. F'eatures which recommended the Oilbreth piles are the opportunities for complete inspection before driv- inp and the fact that th«»y save time because they can he cased while excavation is jroing on. After being driven they can be loaded immediately. Naturally they present con.siderabIe skin friction. The making of these piles above the ground surface also does away with the [jossibility of their beinj; damaged or sqiieezed out of shape by the jar occasioned by driving forms for ad- joining piles. Still another method is used by Raymond. Under this system piles are usually put in by either of twe method.s, the jetting method or the pile core method. The water jet system is iised only where the material penetrated is sand, quicksand, or soft material that will dis.solve and flow up inside the pile when the water is forced through the pipe, thus causing the shell to settl-^ imtil it comes in contact with the next shell, and so on imtil the desired depth has been reached. The shells are filled with concrete simultaneously with the sinking process, and when necessary spreads are attached to keep the hole in perfect line with the pipe. The Yj inch pipe is left in the centre of the pile and gives it greatly increased lateral strength. If desired, the lateral strength may be further increased by inserting rods near the outer surface of the concrete, hy this method, piles of any size \ip to two feet in diameter at the bottom and four feet at the top can be put through If 1 466 CEMENTS AND CONCRETES any depth of water and to a suitable penetration in jand or silt (water sediment). The pile-core method is the one most generally used for foundation work and consists of a collapsible steel pile core, conical in shape, which is incased m a thin, tiRht-fitting metal shell. The core and shell are driven into the ground by means of a pile driver. The core ig so constructed that when the desired depth has been reached it is collapsed and loses contact with the shell, go that it is easily withdrawn, leaving the shell or cas- ing in the ground, to act as a mold or form for the concrete. When the form is withdrawn, the shell or casing is filled with carefully mixed Portland cement concrete, which is thoroughly tamped during the fiUmg ^ThTsimplex system uses another method in which the driving form consists of a strong steel tube, the lower end of which is fitted with powerful tooth jaws, which close together tightly, with a point capable of opening automatically to the full diameter of the tube while being withdrawn. The point of the form closely resembles the jaws of an alligator. At the wime time the form is being withdrawn, the concrete is deposited. It is so evident that concrete is vastly superior to wood in the construction of piles that it is almost su- perfluous to mention the points of superiority . Con • Crete is not subject to rot or the ravages of the teredo worm, neither can the piles constructed of concrete be destroyed by fire, and no cost is attached for repairs. While it is not possible to give accurate statistics as to the life of a wooden pile, as it varies so much under different conditions, yet we know that in som^ casea a wooden pile is rendered worthless in a very few years. HOW TO USB THEM 4«7 especially when the surrounding material it composed of rotted vegftation. or where the pile if exposed by the rise and fall of tides. It is also impossible to statw the exact coat of a concrete pile, as it varies also ac< cording to conditions. Ordinarily speaking, a concrete pile will cost from one and one-half times or two times as much as a wooden pile; but in order to illustratft where a saving can be mado. the following extract is given from a report on the piles driven at the United States Naval Academy at Annapolis, Md. : "The original plans called for 3,200 wooden piles cut off below low water with a capping of concrete. To get down to the low water level required sheet pil- ing, shorting and pumping, and the excavating of near- ly 5,000 cubic yards of earth. By substituting concrete piles, the work was reduced to driving 850 concrete piles, excavating 1,000 cubic yards of earth and placinif of 1,000 cubic yards of concrete." In the work mentioned, the first estimate for wooden piles placed the cost at $9.50 each, while the estimate for concrete piles was placed at $20 each, yet the esti- mate based on the use of wood piles aggregated $52,840, while the estimate based on the use of concrete piles was $25,403, or a total saving in favor of concrete of over $27,000. In several instances piles have been uncovered to their full depth, and they were found to be perfectly sound in every particular. By surrounding the opera- tion with the safeguards provided, it is almost impos- sible to make a faulty pile. The concrete is made as wet as good practice will allow. Constant ramming and dropping the concrete from a considerable height tend to the assurance of a solid mass, then the target on 468 CEMENTS A f the loads to be earned. If intended for small buildings «»d ^^^^r**- ^^^^'V'^" can be made before erection (Figs. 9 and 10) ; but m the case of warehouses, factories, piers, and jett.es, where live loads and vibrator stresses have to be borne, a monolithic structure is secured by buildmg m molds directly on the site. For the lighter classes of mono- lithic structure, expanded metal is admirably suitable; it is also much used for the roofs of reservmrs. and fcir thin partitioned walls. The meshing is simply laid over the ribs or floor beams, which have been already erected,and thegreen concrete is applied to the acquired thickness, being supported from below by suitable sup^ porting work, which is removed as soon as the concrete has set. In cold storage factories, the floor beams and eoilings are invariably erected first, the floor being laid afterward. The ceiling is then solid with the floor beams on their under side, and the floor is solid with them on their upper side, the air space between being a great aid to the maintenance of a low temperature for refrigeration. _ • * ^t In the Monier floors the reinforcement consists ol round rods varying from % inch to % inch diameter The rods are spaced at about six times their diameter, and are crossed at right angles, being connected by iron wire bound round them. This artificial method of securing the rods take, considerable time, and is thus a somewhat costlv process. To produce contmuity ol HOW TO USE THEM metal, the diff«rent lengthfi of rod« are overlapped for about 8 to 16 incheM, and bound with wire. The Schluter are similar to the Monier floors, but the rods aro croased diagonally, and the longitudinal tihIh are of the same size as tho transverse ones. The Cottnncin Hoors have their rods interlaced like the eanes of a chair seat or a hnsket. and the Hyatt floors have squarp rods with holes throiijrh which small trans- viTso rod.s pass. Over fifty systoins of reinforcinjr jire in use, and in most cases the only points of diflferenc*' are the shape of the section and the method of attai'h- ment and adjustment. Hrams. — It is obvious that, as the span increases, a limit will soon he reached beyond which it is not eeo- noniiciil to use plain floor slalw. for their dead weiijiil becomes of such ma^rnitude as to prohibit tlieir use. We have thus to resort to a division of the main span h.\ cross beams resting on columns, and the floor is laid on these beams, which are arran^red to take as much of the load as to render it possible to reduce the thick- ness of the floor within reasonable limits. Reinforeed concrete beams are typical of the construction in which the merits of two component materials are nmde to serve a common end ; but in the particular case of steel and concrete, the actual part played by the steel is not at all well understood. Speaking generally, beams do not diflFer in construc- tional details from floors. The same reinforcement is used in both, the only difTerence beinpr. that as beaiiis are usually deeper than floors, the shearing stresses l»e- come more pronounced, the greater provision has to i)e made for them by a liberal use of stirrups or vertical binding rods. In some systems the reinforcement con- I MICROCOPY RESOLUTION TEST CHART (ANSI and ISO TEST CHART No. 2) ■- IIIIM ■ so '""= til 140 2.2 1 2.0 1.8 ^ APPLIED IM^GE Inc a^T'- '6^3 East Main Street S^^ Rochester. New York U609 USA '.^S {7' 6} 482 - 0300 - Phone S^ (716) 288 - 5989 - Ta* i^ 470 CEMENTS AND CONCRETES sists entirely of straight rods, disposed in a-y P-^J^ the beam where tensile stresses are likely to be eallea into play In others, specially bent rods are joined or TmX straight rods, disposed and when weldmg has to be done it would appear that wrought iron is more ^tt\L'uTl ttrange the dimensions of the beams so Lt the whole of the compressive st-ses ^ ^^^^^^ hv that portion of the concrete on one side of the neu tral axis- but in some cases, as with contmuous beams rLTy' beams of small depth, a PO^tion o .^^^^^^^^^ forcement is disturbed along compressed P^f ^^e^^^^^^^^^ beam the steel rods either takmg up the excess ot Lrressive stress over that at which the concrete can TsSy worked, or else taking up t";^^^^^^^^^ at the places where they occur over the 8"PP«^f , f a .eneral rule we may take it that the economical depth Jofa reinforced concrete beam, freely -PPOf^^d at both ends is one-twentieth the span, and is thus ap- proximately the same as that of a steel girder of equal strenSh Reinforced concrete beams are now made for spans up to 100 feet for buildings, and 150 feet for brXs But for each class of work beyond this limit the w ght becomes excessive. Several arched ribs, for much greater spans have, however, been success- ''^The'beams are made in much the same way as pUes and columns; they can be made m sheds on the sxte, or in the actual position they are to occupy when fin- • i,n/i ThP ceilint' and beams are erected tirst, tne ;tor bei?/. t -rd worked on the top of the bean.. Wrthus obtain a very perfect -"olith.c stmetu^^^^^^ which any vibration set up by maclimery, falling loads, 1 HOW TO USE THEM 471 etc., will be of much less extent than with any ordinary type of building, in which there is often a great want of rigidity, the beams and arches being loose and able to vibrate independently of other parts of the struc- ture. Ccncrete being as weak in shear as in tension, pro- Tision is also required to take the shearing stresses. Somo American designers have to this end patented special forms of reinforcement bar, in which each main tension bar has projecting upward from it ties inclined at the angle of 45 deg. (Kahn system.) These ex- tend to the top of the bar and take the tensile stresses arising from the shear. The corresponding compres- sive stress at right angles to this is carried by the con- crete. The system is efficient and on large spans, where weight must be reduced to a minimum, it has its ad- vantages. Thus, in the Ransome system (Fig. 12), the shearing stresses at the end of a beam are taken up by inclined reinforcing rods imbedded in the concrete at the junc- tion of beam with column. Arches. — Concrete has long had an extensive ap- plication in the building of arches, but until the in- troduction of reinforced r mcrete the arches that could be economically and safely constructed were limited to spans of a few feet. The general rule that the line of resistance fell withm the middle third had to be ob- served for simple concrete arches, as for those in brick- work and masonry; and the thickness of the arches at the crown was thus approximately the same whether built in either of these materials. The introduction of steel reinforcement, however, made it possible not only to reduce the thickness of the rinjf ,H .1 1. iiil r It i 4»(. CEMENTS AND CONCRETES (Cinders should mvrr he used, an they have a tn^nej, in destroy the life of the eemcnt and eame it to d«- i„tn/rate.) A foundation, however, may also hv formeU „f lirick or hollow til.- .-mbt'dded solidly in and covon-d with cemfnt mortar. Concrete nhould b<- allowed to th..r.M.>rhIy harden lu-tore laying' the floor, and should he ,vell 8oaked with water before laying the tile. Umc mortar should never be mixed with conereting. roncrdc should eonsint of one part Portland cement, two parts clean sharp sand, two parts clean gravel, and thoroughly n.ixed with sufficient water to form a hanl. solid mass when well beaten down into a bed, which should be from 2V.. inches to 3 inches thick. If tlu concrete bed can be made over three inches ir thickness, the concrete can then be made of one part Louisville cement, one part clean shan) sand, one part clean gravel and thoroughly mixed with sufiicient wa- ter, as above described. For Floors.— Tho surface of the concrete must be level and finished to within one (1) inch of the fin- ished floor line, when tile V, inch thick is used, which will leave a space of i^: inch for cenr. nt mortar, com- posed of equal parts of the very best quality Portland cement and clean sharp sand. The distance below tlu> surface of the finished floor line, however, should be governed by the thickness of the tile. For Wood Floors.— Vfhi-n tiles are to be laid on wood flooring in new buildings the joists should be set Ive hiehes below the intended finished floor line and spaced about 12 inches apart and thor .ughly brid-ed so as t<. make a stiff floor, ami covered with one-uich boards „nt over six inches wid.' (boards three inches wide preferred), and thoroughly nailed, and the jon.U Vh HOW TO USE THEM 481 inch apart to allow for HwelliriK. (See No. 31.) (A iHver of heavy tar paper on top of wood flooring will protect the boards from the moisture of the concrete. Hnd will also prevent any moisture from drippinjr through to a ceiling below) In Old 5u»Wmflr«.— Cleats are nailed to joists fivo inches below the intended finished floor line, and short pieces of boards V^ inch apart fitted in between th.' joists upon the cleats and well nailed, and the joists thoroughly bridged. The corners on the upper edge of the joists should be chamfered off to a sharp point (see Fig. 32), as the flat surface of the joists will give an uneven foundation. When the strength of the joists will permit, it is best to cut an inch or more off I ■;i li 482 CEMENTS AND CONCRETES the top. (Where joists are too weak, strengthen by thoroughly nailing cleats six inches wide full length of joists.) When the solid wood foundation is thus prepared, concrete is placed upon it as above directed. Where Steel Beams and hollow tile arches are used, frequently very little space is left for preparing a proper foundation for setting tile, as the rough coating is usually put in by the hollow tile contractor to pro- tect his work, but this covering should always conform Fig. ss. to the requirements for a solid tile foundation. Should this not be the case, the tile contractor should remove sufficient of the covering to allow him to put down a foundation that will insure a satisfactory tile floor. (Cinders, lime, mortar or inferior material must never be used.) The tops of iron learns should be from three to font inches below ihe finished floor line, to prevent floors, when finished, showing lines of the beams. For Hearths.— The foundation for heanhs should b« placed upon a brick arch, if possible, to ensure perfect fire protection, and then covered with concrete in the same manner as directed for tile floors. If placed upon a sub-foundation of wood, the concreting should be at least six inches thick. (See Figs. 34 and 35.) HOW TO USE THEM 483 v//MrmxafA-,T',Tccrja/M^MrMr/yzryyj'AryM^^ Vis. 84. Fl» 8S. w»^< 484 CEMENTS AND CONCRETES For Wofls.— When tiles are to be laid on old brick walls the plaster must be all removed and the mortar raked out of the joints of the brick work to form a key for the cement. On new brick walls the points should not be pointed. When tiles are to be placed on^tud- dins, the studding should be well braced by filling in between the studding with brick set in mortar to the height of tile work (see Fig. 36) ; or brick work may be omitted and extra studding put in and thoroughly (TVDOINC -CfMtHr -TIW Ftg- 36. t.ridged. so as to have as little spring as possible and this studding then covered with sheet metal lathing (See Fig 37 ) {Tih must never be placed on wood latii ar on old planter.) The brick walls must be well wet with water and then covered with a rough coatm, of cement mortar, composed of one part Portland co- HOW TO USE THEM 485 ment and two parts clean sharp sand. When tiles are placed on metal lathinjcr, hair should be mixed with the cement mortar to make it adhere more closely to the lath. The cement mortar should be y^ inch thick, or sufficient to make an even and true surface to within one (1) inch of the intended finished surface of the tile, when tile V'z inch thick is used, which will allow -snioaine Fig. 37. a 'space of ^A inch for the cement mortar, composed as above for rough coating the walls. The face of the cement foundation should be roughly scratched Jind allowed to harden for at least one day before com- mencing to lay the tile. If anj- lime is mixed with the cement mortar for setting the tiles^ it should never exceed 10 per cent., and great care must be used to have the lime well slaked, and made free from all ill n % ^i X. It H- »i I 3i ■" 486 CEMENTS AND CONCRETES lumps by runnin? through a coarse sieve in order to guard against "heaving" or "swelling," and thus loosening or "lifting" the tiles. Important.-The foundation for both floor and wall tiling should be thoroughly brushed, to remove all dust and small particles adhering to it, and then well wet before putting on the cement mortar To ensure a perfect bond it is best to coat the foundation by brush, inc over it pure cement mixed in water. Cmen*.-The very best quality of Portland cement Bhould always be used for setting either floor or wall tile and for grouting the floors, and the very best quality of Keene's Imported Cement for fiUing the joints in the wall tiling. , » „ u Sand.-C\em, sharp -m sand, free from aU salt, loam or other matter, and perfectly screened before mixing with the cement, should always be used. Mortar.— For floors or vitrecud tiles, should be com- posed of equal parts of cement and sand, and for wall tiles one (1) part of cement .nd two (2) parts sand. The mortar should not be too wet, but should be rather H\m, and should always be used *resh, as mortar, when allowed to set before using, loses a portion of its strength. , , , , Soaking.-Tiles must always be thoroughly soaked in water before setting, which makes the cf- .^ unite to the tiles. , . , The Tiles for tite Floors are first laid out to ascer- tain if they are all right and compared with the plan provided for laying the floors. Strips are then set, ^ beginning at one end of and in the centre of the room, and level with the intended finished floor line Two sets of guide strips running parallel about 18 to 30 HOW TO USE THEM 487 inches apart should be set first. (See Fig. 38.) Th© mortar is then spread between them for about six to ten feet at a time, and level with a screed notched at each end, to allow for the thickness of the tiles. The tiles are placed upon the mortar, which must be stiff enough to prevent the mortar from working up be- •■^>:4<^---<;>s>--<><>-v': Ky!! ^A A A A • • • ;' >i • FiS.38. tween the joints. The tiles are to be firmly pressed into the mortar and tamped down with a block and hammer until they are exactly level with the strips. When the space between the strips is completed, the strips on one side of the tile is moved out 18 to 30 inches and placed in proper position for laying an- other section of tile, using the tiles which bave^beeu i. j' . ii ! I > I I.' 488 CEMENTS AND CONCRETES laid for one end of the screed, and the laying of tl* tile continued in the same manner until the aoor is finished. When the cement is sufficiently set, which should be in about two days, the floor should be well scrubbed with clean water and a broom, and the joints thoroughly grouted with pure cement (mixed with water to the consistency of cream). As soon as this begins to stiffen, it must be carefully rubbed off with sawdust or fine shavings and the floor left perfectly clean. Ceramics.— The foundation and cement mortar for ceramics are the same as for plain or vitreous floors, and the guide strips used in the same manner. The cement mortar is then spread evenly and the tile sheets laid carefully on it with the paper side up. After the batch is covered, the tile setter should commence to press the tile into the mortar, gently at first, firmly afterwards, using block and hammer, thus leveling the tile as correctly as possible. The tile should be beaten down until the mortar is visible in the joints through the paper; however, without breaking it. The paper is then moistened, and after it is well soaked and can be easily removed, it is palled off backwards, starting from a comer. After removing the paper, the tile should be sprinkled with white saiid before fin- isliing the beating, so that the tiles will not adhere to the beater, owing to the paste which is used in mount- ing them. Corrections of the surface are then made by^ leveling it with block and hammer. The filling of the joints and cleaning of the surface is a delicute op- eration, as the looks of this work depends largely upon u. The joints are to ' filled with clean Portland i" f f ^ ll 498 CEMENTS AND CONCREIES show that a 6-inch thickness of 1-2-4 concrete properly made is waterproof up to about 50 pounds to the square inch. This concrete is frequently used for facing dams. 1-3-6 is the proportion generally used for the interior of dams and large structures. It is entirely suitable for large foundations. 1-4-8 is frequently used for foundation work, and when pro{)erly mixed makes good coafi^te, although it is about the limit of what is consiaiered good work, and would not be suitable for very important structures. 1-5-10 is equal to any concrete made with natural cement. It is a well-known fact that the volume of concrete when mixed with water is somewhat less than the volume of the aggregate and cement before mixing. The con- tractors' rule is that the volume of mixed concrete is HOW TO USB THEM 499 equal to the volume of the stone plus one-half to one- third the volume of sand. There has been much discussion among engineers and others as to the amount of water that should be added to the aggregates and cement for making the best concrete, and while it is not the purpose of this paper to enter into this controversy, it might be said that the modem tendency is toward wet concrete. The old way was to add just enough water so that when all Flff. 4S. the concrete was in the form and tamped, it would show moisture on the surface. The tamping is a very important part of the operation, and the quality of the work is dependent upon how well this is super- intended, as unless it is well and thoroughly done the concrete is liable to be honeycombed and imperfect, especially near the forms. With, the growth of tho 500 CEMENTS AND CONCRETES use of concrete the old method of putting it in the forms nearly dry and depending on tampmg to con- solidate it has been more or less abandoned, and the more modern way is to put the concrete in quite^wet. as less tamping is required and much labor and ex- pense saved. One of the great objections to this scheme is that if care is not taken the water will tend to wash the cement from the stone and sand; in other words, unmix it. However, it may be said that it is now generally understood that rather wet concrete properly handled makes better work. The amount of water to be added to the aggregates and cement va- ries from 1 water to 3 cement by measurement to 12 per cent of water by weight. Mr. Carey, of New- haven, England, says that 23 gallons water per cubic yard of cement was the best mixture. Quite frequent- ly salt water is used in mixing concrete in cold weather to prevent freezing, and it seems to have no ill effects on the resulting mixture. Reinforced Cmcrete.-Vv to the last few years the use of concrete as a building material was chiefly con- fined to the construction of foundations, piers, reser- voir dams and similar purposes, in which the stresses to be met were almost entirely simple pressures. In- deed even fifteen years ago, many engineers looked askance on the use of concrete for arches, considering it for this purpose much inferior to brick. Much ot the caution shown in extending the use of this valua- ble material doubtless arose from the frequency with which concrete masonry exhibited unsightly cracks, due largely to the material being allowed to get too drv while hardening. At the same time, careful ex- amination has shown that cracks of the sara^ char- HOW TO USE THEM 501 acter are common in masonry of all kinds, but are unnoticed, because they follow the regular joints of the structure; whereas, on the smooth uniform sur- face of the concrete, cracks of much less significance are immediately visible. The plan of reinforcing the material with metal, of which several systems have been introduced durinjr the last four years, has greatly extended the possible use of concrete; and it appears that in many cases structures so far as these affect the uae of reiu^ forced concrete. REINFORCED CONCRETE. The engineer who is designing a steel structure speci- fies that tests shall be made at the shops which wiU give a clear indication of the character of the materials used. These tests refe- to the ultimate strength, elastic lunit, ultimate elongaiion and reduction of area. He also in- Bpects the cons' ruction of his structure, and bad work- manship is getting more and more rare. If poor work is v)metimes done it can be discovered by careful inspec- tion and when the structure is tested on completion noth- ing unexpected wilx take place, if its type and design are bied on practical experience. Thus the deflections which steel structures show under their test loads are found to be almost identical with those computed for them and their determination is, therefore, not of great ""Vhe measuring and observation of the local deforma- tion., on the contrary, furnish valuable information on the distribution of streases, and enable the engineer to appreciate the advantages and disadvantages of the vari- ous types of construction ; but it is very seldom that they disclose faulty construction or bad material. It can thus be said that for steel or iron structures the preliminary' tests of the materials used and the inspection of construe tion and erection furnish all the necessary assurances. Quite different is the case with concrete-steel structur^, because laboratory tests tell us only of the quality of the materials employed, and the most active inspection will not be able to prev<;nt positively poor workmanship and 510 REINFORCED CONCRETE 5U faulty construction which can destroy the strength of structures made of the best materials. In fact, the proportions of the concrete may, in spit* of careful watching, not be in all parts in accor*i;Ui" with the specifications: the quantity of water ui cl in mixing must, in order to produce identical results, vf-ry within a wide range, according to the condition of iuoli- ture in the r iterials and the atmosphere, and it is quite sure that it ill be sometimes badly proportioned. If too much water be added the strength of the concrete, and especially its coefficient of elasticity, will be decreased to a degree which may be considerable ; if too little water be added the adhesion of the concrete to the reinforcing metal will not be sufficient. The thoroughness of the tamping has a still greater influence on the strength of the work. To the faults of execution, faults of design may be added. The latter must especially be guarded against in a new type of construction, the theory of which is not yet fully established. Whatever the results of the tests of the materials may be, very little information on the strength of a concrete- steel structure can be obtained without direct tests of the structure itself. But observed deformations will furnish reaUy useful indications only when compared to the nor- mal deformations which, according to the computations, should have been caused in accordance with the quality and disposition of the materials. Hitherto no method has been established to enable the engineer to compute these normal deformations. However, at one time it was assumed that reinforced concrete, whatever its deforma- tion, preserves the coefficient of elasticity as determined in ordinary tension tests, and at another that the resist- ance of the concrete in tension can be neglected in rein- forc I members. Sometimes it has also been assumed m 512 CEMENTS AND CONCRETES i that the resistance of concrete in tension can be negiectea only when its deformations exceed the elongation which causes rupture in common tension tests. None of these assumptions has given results agreeing with the actual behavior of reinforced concrete. We may conclude that in reinforced concrete construction certainly some par- ticular phenomena occur, a knowledge of which is neces- sary to predict their resistance and deformations. Concrete in compression is generally not reinforced and it cannot be expected that the phenomena mentioned in the preceding section will be found to be caused by it. It suffices to recall the well-known law of deformation of concrete in compression and to make it more precise by naming the ratio of an infinitely small variation of com- pression to the variation of length caused by it, the "in- stantaneous coefficient of elasticity." When the compres.sion increases, but remains within an amovint which, in general, is nearly a third of tb« ultimate strength, the instantaneous coefficient of elas- ticity decreases, but in a very small degree. When the stress increases still more the change in the elasticity gradually increases; it is appreciable for a compressive stress near one-half the value of the ultimate, and it then increases so rapidly before failure that the instantaneous coefficient may fall below one-twentieth of its value un- der a light stress. This aspect of the deformation is similar to the one generally observed on all materials. The simple law which determines the deformation of concrete in compression thus cannot furnish the explana- tion of observed irregularities, and it mu?> he loo'.etl for in the phenomena which are produced in tension. Tt appears to be evident that the test loads should not be heavier than the amount refjuired to insure the safety of the structure. Even smaller loads could, no doubt, be REINFORCED CONCRETE 513 employed if a comparison of the computed deformations and those actually observed is made, as has been proposed in this chapter, so as to obtain by means of moderate test loads the coefBcient ' f elasticity, the elastic limit and the tensile resistance of the concrete of the tested beams. It is, besides, known that the compressive resistance is al- most proportional to the tensile resistance and it is con- sequently evident that a test with a moderate load will suffice to furnish information on all the properties of the concrete employed. To the preliminary tests of the materials to be em- ployed the direct tests of reinforced concrete structures must be added to obtain sufficient assurance of safety. The tests will not show their full usefulness unless the deformations which should normally be expected be first computed and t'len compared to the observed defor- mations. The computation of the deformations to be expected must be based on the knowledge of the laws of defor- mation of concrete reinforced by metal, and it appears that above the elastic limit, these laws are different from the laws which determine the deformations of unrein- forced concrete. The deformations of members in flexure appear to be influenced by the shearing stresses, by the character of the surroundings in which the concrete has set and was kept and by the action of any transverse reinforcing members. The investigation and study of these phenomena is still more important because the strength of a member is intimately connected with its deformations. It is easier to compute the elongations and shorten- ings which should be expected to take place, under nor- mal conditions, in a given section than the deflection of 514 CEMENTS AND CONCRETES a beam, which is the resultant of the deformations of all of its sections. The measuring of the local deformations deserves, therefore, to be recommended and at least to take its place side by side with the measuring of di-flec- tions. Concretes placed under water and gradually hardened there show a tendency to swell in all directions, and thf more so the richer their proportions of cement. This swelling varies from 0.1 to 0.2 per cent, for pure cement mortar and from 0.02 to 0.05 per cent, for concrete pocr in cement. When the Ewelling cannot take place freely, coiiipres sive stresses are developed in the masonry, which may reach much higher values than the stresses caused by the shrinking in the air. Experiments were made which were intended to establish the law of relation be- tween the deformations, prevented from exceeding cer- tain limits by external means or metal reinforcing, and the stresses developed at the same tune. An idea of the importance of these stresses will be formed by the fact that, in a rectangular prism 2.36 by 0.98 inch, made of neat cement and reinforced in its axis by an iron rod 0.4 inch diameter, there have been developed, after ten months in water, internal and opposing stresses of about 2.200 pounds, equivalent to a compressive stress of about 90 pounds per square inch in the concrete and a tensile stress of about 17,500 pounds per square inch in the iron. The tension in the iron was measured directly, jind computed as accurately as possible by multiplying the coetlicient of elasticity by the shortening of the rod ' caused at the instant when the s\ir rounding cement which prevented it from taking its natural length was carefully removed. The internal stresses caused by the prevention of the REINFORCED CONCRETE 515 swelliii- of mortar or coDc;retc members by the reinforc ing rocfs are, in general, favorable to their resistance, be- cause these stresses increase the compressive stresses and decrease the tensile stresses of the materials which can resist the former ten times better than the latter. They have especially the effect of consolidating building joints and all sections of small resistance to tension by prevent- ing cracks in them. Obvious advantages result therefrom for the resistance of masonry kept under water and the aurability of the concrete and its reinforcing metal. Differences in the swelling of layers of different age must, however, be guarded against as they cause parallel stresses in the joints, which seem to be injurious to the adhesion. But, contrary to what takes place in the case of shrinking, it is here the oldest masonry in which ten- sile stresses are caused, and its resistance being superior to that of the superimposed masonry the possibly dan- gerous effect is decreased. However, the author has no experimental proof as to the dangers due to the diftVrent swelling of parts of masonry. In general an exaggerated account of the internal stresses should be avoided because their effects combine according to little-known laws with the stresses caused by the external forces, and it may be possible that m some places their actions should be added together. . It seems, therefore, to be proper not to raise the pro- portions of cement in concrete above the limits which insure sufficient impermeability and long life to the aib- merged concrete. It appears to be of advantage not to exceed 1,300 to 1,500 pounds of cement to the cubic yard of concrete, which proportion gives the greatest resis- tance except for work exposed to the waves, where rapid- itv of setting is a necessary condition foi succpssfuj work From all the above considerations it follows that 616 CEMENTS AND CONCRETES reinforced concrete masonry will give rtill better results for hydraulic work than for structures exposed to the air, and the success of these has been proved by experi- ence. It should be stated that, in the computations of the resistances of concrete masonry structures in which the free cliange of volume is in any way prevented, these changes should be considered. On this basis the author recently showed that in the floor of a dock only harmless stresses could be produced in spite of the fact ihat this floor was of a thickness which would have caused exces- sive stresses if the increase in volume had not sitrongly compressed the floor against the foundations of the side walls. It is well known that all the materials employed in masonry show an increase in volume when they absorb water and a decrease when their moisture is reduced. The author has found these changes in volume to be much greater than is given by Busing and Schumann in their work on cement. A prism of neat cement, not rein- forced, which was kept in dry air during two years elon- gated 0.024 per cent, of its length after three weeks ol' immersion in water. A prism of mortar, not reinforced, containing 730 pounds of cement to the cubic yard of sand, which was kept fifteen months in water, shortened 0.05 per cent, after being two months in dry air. Prom the observations made it appears that contrary to what has taken place in the changes of volume due to th»' Sfradual hardening of the cement, the variations in vol- ume produced by changes in the state of moisture on hardened mortar do not increase with the higher pro* portions of cement. The contrary rather takes place. There is still another radical difference between the effects which the two causes of change in volume have REINFORCED CONCRETE 517 on reinforced concrete members. During the hardening the mortar possesses at the beginning a very high degree of plasticity, which gradually decreases. This results in causing the mortar, which has gradually hardened, to yield to a large extent to the stresses which the reinforc- ing rods produce in it. Thus reinforced members which have set in the open air remain of a greater length than that which they would have taken freely without re- straint from the reinforcing. The crystallizations which take place during the setting are between the artificially separated molecules, and a decrease in density, elasticity, and resistance is the result. The opposite should be caused in reinforced memliers which have hardened in water, but the author has not had the occasion to verify whether an improvement in the r, since internal stresses, and cspeeially tensile stresses in the reinforcing rods, may be caused, which attain r).r)()0 to 8,500 pounds per square inch. Contrary to what takes place during the slow hardening of mortar, the hygrometric variations appear to b(> the more danserous? the less rich in cement the mor- tar is, because its resistance is smaller while the internal stresses are, at least, as great. It should be added that these disadvantages are practi- callv of no account for masonry always exposed to the air because the changes in the proportions of moisture in the air have a very small effect. The question is only of im- portance for members made in the open air which begin to harden before being put in water where they finally remain submerged, as in the case of piles, caissons, etc. By keeping them moistened until put in place, not only will the cracks which are often caused, as has been shown by experience, be prevented, but also the changes in the internal stresses, which cannot be of any advantage. It would be both interesting and useful to determine experi- mentally the results to be obtained by keeping reinforced concrete members, to be permanently exposed to the air, as moist as possible by abundant and repeated sprinklmg for several weeks. It is obvious that the final shrinkmg, as well as the disadvantages resulting therefrom, would be decreased. • In concluding attention should be called to a fact worthy of research. Reinforced concrete members pre- viously subjected to test loads have shown very little ef- fect due to changes of the moisture in them. This will seem probable when it is remembered that the test load reduces the coefficient of elasticity of the concrete very considerably. . . The first idea which presented itself to engineers to in- REINFORCED COXCRETE 6}» crease the resistance of toTi.-retc in compression was to reinforce it, simil-^rly to tension pieces, by rods laid longitudinally in tl.e diivction of the stress. For purposes of construction, to keep the rods better in place, the rem- forcin" rods were tied t<»}.'ether by a network or a belt of sinalk-r rods. Some en-ineers understood that these belts perform another important role, that they protect the lon^'itndinal rods from premature flexure and retard the sweHinj: of the concrete and, hence, its ultimate failure. It will be seen below that by hooping or completely sur- rounding the concrete by steel rods a considerably higher resistance can be obtained, and it is evident that between thivs method, supplemented by the addition of longitudi- nal rods, on one side, and the method of reinforcing by lon.'itudinal main rods tied together by belts of lighter material on the other side, there is an intermediate con- tinuous series of methods of reinforcing. The conclu- sions reached by this study will enable us to foresee the effects of these complex combinations, but before making the synthesis the influence of each element should be in- vestigated separately. Concrete reinforced by longitu- dinal vods tied together by netting or belts of dimensions too small or spaced too far apart to e-rt noticeable influence on the resistance of concrete will, therefore, be treated first. It was admitted, up to the present time, that the dif- ferent varieties of stone, mortars, and concrete, when under compression, always fail by shearing along planes which are inclined to the direction of the stress. The recent experiments made in Germany by Foeppel and repeated by Mesnager at the laboratory of I'Ecole des Fonts et Chaussees have proved that this mode of failure is due to the friction exerted on the lower planes of the test specimens by the plates transmitting the pressure. Ij S20 CEMENTS AND CONCRETES And it has further been proved that by suffieiently re- ducinf? this friction by the introduction of a greasetl sur- face, the failure will take place along surfaces which will be parallel to the direction of the ^^ressure. It is not clear how longitudinal reinforcing bars, which are parallel to the lines of rupture, could prevent the separation of the molecules and increase the resistance of the concrete, and it seems that the only eflfect of longi- tudinal reinforcing in compression members consists in adding the resistance of the steel to that of the concrete without strengthening the latter. Experience has shown that such is the ease. The effects of the reinforcing bars are, however, complicated, for the reasons which follow. As has been shown, the tendency to shrink which con- crete shows when hardening in air causes in reinforced concrete internal stresses of great intensity tension in the concrete and compression in the metal. Experiments made in 1902 at the laboratory of TEcole des Fonts et Chaussees, according to the program laid out by the French Commission on Concrete-Steel, have determined the eflfect due to the shrinking of large concrete-steel specimens of the most commonly employed mixture, 420 pounds of Portland cement to the cubic yard of sand and i-inch gravel in the proportion of 1 :2. Measurement of the variations in length of the reinforcing bars has shown that after three months the shrinking of the concrete had compressed the metal, 6,540 pounds per square inch, in prisms 6.5 feet long of a section about 4x4 inches and reinforced near the edges by 4 iron wires Vt inch in diameter. The compressive stress in the metal has reached 10,800 to 14,200 pounds per square inch in beams 13.1 feet long having a cross-section about 8x16 inches and re- inforced near one of the smaller sides by 4 metal rods of 7/s-inch diameter placed 1.3 inches from the face. The REINFORCED CONCUETE 521 & I latter speciraons were prepared to be tested for bending. It is superfluous to point out the importance of the above statement as to the magnitude of the interior stresses in members of the usual mixtures and of dimen- sions similar to those met in practice. Neglecting this kind of stresses, some engineers have made grave mistakes in the interpretation of bending experiments and have established incorrect formulas and rules, especially on the subject of stresses in compression members. They have assumed that if a certain specimen has undergone a shortening, i, its reinforcing bars, which had a coefficient of elasticity E, were compressed to a stress E i, neglecting the addition which has to be made to the latter stress for the shrinking of the concrete, if it has hardened in air, and which usually exceeds it in amount. The above con- siderations are sufficient to compute the strMses in com- pression members as long as the elastic limits have not been surpassed, neither in the concrete nor in the metal ; but this is only one side of the question. Without entering into a discussion of the unit stresses which may be allowed for the various elements of rein- forced concrete structures, it is evident that the basis of any computation must be the knowledge of the stresses which are induced in these elements at the instant at which, for the first time, there appears any danger for the one or the other of them. It is, therefore, important to know the stress caused by the reinforcing steel in a member in compression at the instant where it begins to fail by the crushing of the concrete, which takes place a long time before that of the steel. A concrete of common quality can stand without crushing a reduction in length of 0.07 to 0.10 per cent, and sometimes more. Such a compression will cause a stress in the metal of 20,000 to 29,000 pounds per sauare 522 CKMKNTS AND (JOXCUKTKS iiK li. il" the (wmcitMit of flHsticity Im' 2«>.()(KMHH^ pcunds This htnss luUh'il to »hf prfvi(»us htri'M of 7,000 to 14,000 l>oun.is, irives » total of 27.000 to 43,000 pounds \wr squjirc inch of the metal, which is equal and even hu- perior to the ehistie limit of the iron and mild stwl whieh is usually employed. Therefore, before the crushing of th«' t'oncrete, the leiiiforcinK hars are almost always stressed up to their elastic limit, unless the elastic limit of the bars be exceptionelly high' or the concrete excep- titiually poor. This stress cannot be appreciably surpassed because a very ^'rcat decrease takes place in the value of the coeffi- cient nt' elasticity of the metal as soon as the ela.stic limit has been exceeded, and the stresses increase, therefore, with an extreme slowness which is limited by the sumll • leformatious which the concrete can still undergo with- out crushing. Whatevei- the mode of luptui-e of concrete in compres- sion, the crushing of the same must be retarded by the use of reinforcing rods put in planes perpendicular to the j either ot c.r. cumferential hoops or of netting win's at n^ht anwles and parallel to the sides of th.' section. For ecpud we.K'h.s of metal the -asistance to crushing: was apprecuibly more than twice as preat for the circumferential reinf.)rc.n« as for the wire netting. Without entering into a theoretical discussion, tae above result can be explaine and Marble Plaater," the procew of it. compoaition and the - purpoMs for which it U adapted. 114. OivTTdewription of "Scagliola," 't« excellent qualities, durability, and the purposes for which it is adapted. 115 Give a description of the colors and quantities that are used for the following marbles, respectively, namely, Penzance marble, Egyptian Green, Dark Porphyry and Green Genoa. 116. Give a description of the process of the polishinjr of "Scagliola." . 117 Give a description of the process m the manufac- ture of "Marezzo," and the purposes for which it is adapted. 118 Give a description of the method of executing ■ granite plaster work, and how it is manipulated in its composition. 119. Give a description of concrete in general and some of the uses to which it is applied. 120. Give a description of what the term ' matrix is applied to when considering the qualities of any material. 121 Give a description of what is meant by the term ' ' Compound Aggregates, ' ' and explain the aiffer- ence between an inferior and superior aggregate by an example. ' ,, 100 Give a description of the "Voids in Aggregates, and what methotl is used to ascertain the voids. 123. Give a description of the "crushing strength of con- crete" and upon what it depends. 124. Give a description of the "ramming of concrete and the effect that is produced. CKMENTS AM) CONCRETES 125. Oivp a d«wription of the thickn«. of conmte paving «»d it. relation to the foundations, and to Sie amount of traffic on street sidewalks, stable floors and yards. „.„:„ 126. Give . description of "Eureka Paving ite man^- ulatica, and the purposes for which it is best 127 GWe* a^tscription of the method of preparing the a^ate for Eureka, and the quantities for the rough coat and topping. , v -♦ 128 Give a description of the "levelling and adjust- Tent of the requisite falls" in the laying of con- Crete pavements and flooring. 129 Give a description of the two parts in the compo«. Jon of foundations, and the method of manipula- 130 GiTa description of the "laying concre*^ pave. mLJs" and the processes to be employed m order to leave the surface uniform, straight and solid 131 Give a description of "trowelling concrete and how the best effocts may be attamed. ^ 132. Give a description of the process termed grout- inir " and when it is adopted. 133. Oivf, ascription of the Method. otj-P^'t'™ of maUriak that are sometimeB adopted for non- 134 g!« r7e.Sp™'°rf the preparation of "((rooved and ronghened 8»rfaee»," that are requu^ for stables, yards, etc. j • ^i 135 Give a description of the process employed in col- ' oring cemen^t work, and how the best r^ulte iw be obtained, also some of the materials to be used in producing the color desired. yllBSTIONS 186 Give » da^jription of the method of depotitini? .on- ^ itnd what Hhould be .voided in the proce*.. 137. Give a' d-cription of the pro« f ™«d •' R*tem- pering, " and the conditioim upon which the prop- er lettiiig of concrete depends. 188 Give a description of how to treat operat.onH m concrete during freezing weather. 139 (Jive a deacription of "Rubble Concrete. lU oor> poaition and meth«Ki of manipulation. 140 Give a description of how to face concret.-. the ■ composition employed, and how it is prepared. 141 Give a description of the "top dressing or wearing ■ surface" for finished walks, and the ineth.Hl of mixing the mortar. 142 Give a description of the composition of Haw- ■ ment Floors" and the method of their treatment. 143. Give a description of the construction of eonerete stable floors and driveways. 144 Give a description of concrete nteps, their manner of construction, aiul in what places they may be advantageously adi»pt«Hl. 145. Give a detaiUnl deseriptit.n of wood fram.ntj in the construction of coiurete stairs. 146 Give a dewsriptiim of Hie materials required for a concrete steireas.., an.l h..w to manipulate them for the several purposes retiuired. 147 Give a description of "iModelling in Fine Con- crete" and the several stages in the development of the process to obtain the proper execution of the figure or design required. 148 Give a description of how concrete fountains are constructed, and how a saving of material may be effected. i CEMENTS AND CONCRETES 1AQ Give a description of the construction of concrete '''• Z^Z the manipulation of the matenals for the purposes desired. 150 Give a description of the composition of "concrete 150. ^'^^^^^^ „,thod of manipulating the ma- terials. INDEX , rtam MATERIALS: 21 Limes .• '''^ 30 Cements '..'..'. 28 Mortars ' * * * 28 Sand 31 Plasters and laths WORKMANSHIP: 35 External work 3^ Internal work SPECIFICATION CLAUSES: ^2 Materials * * *" 43 PREpIra™]? op bill* of' QUANTITIES: ^ Materials " * 45 Workmanship '^ 4g Laths TOOLS AND APPLIANCES: ^ Iloes and drags g2 The hawk ' 52 The mortar board g2 Trowels ' 52 Floats 54 Moulds 54 The pointer 55 The paddle • • • 55 Stopping and pickmg out tools • • • ^ Mitering rod 55 Scratcher INDEX TOOLS AND APPUANCES.-Continued. ^^ Hod ■ * ' 56 Sieve . 56 Sand screens 57 Mortar beds * 57 Slack box 57 Lathing • 58 Lather's hatchet " -g Nail pocket * " ' ' ] 53 Cut-off saw -Aairt PIJS.STER. LIMB. CEMENTS, SAND, ETC.: ^^ Plaster of Pans. ...... •• g2 Quick and slow setting plaster •••••• ^^ Testing '"*'/, 65 French plaster 65 Limes 66 Hydraulic limes 69 Calcination * * ' 70 Slaking ] " " 73 Mortar •• _ 78 Hardening of mortar g2 Magnesik in mortars.... ••• g^ E^ts of salt and frost in mortar .• ^ Sugar with cement • gg Sugar in mortar " gg Lime putty \ 90 Setting stuff ...••• " . 91 Haired putty setting •• ^^ Lime water ..*..!!..... 91 jjiiii- 92 Fibrous substitutes for hair ^jj Sawdust as a substitute for hair • • • • ^^ Sand 96 Mastic 96 Scotx'h mastic " 97 Common mastic * 97 Mastic manipulation INDEX vAoa PLASTER, LIME, CEMENT, ETC. -Continued. ^^ Ilamelein's mastic gg Mastic cement TERMS AND PROCESSES: ^ Three-coat work gg First coating * jqq Scratching ' ' ' iq2 Rendering ^ ' " jqS Screeds " joS Floating 106 Flanking • m Scouring coarse stuff ^^2 Keying 114 Setting •••:••••••• '.115 Laying settmg stuff. ^^^ Scouring setting stuff. .......... •• -.-.g^ Troweling and brushing settmg stuff JJ^ General remarks on settmg ^^g Common setting jig Skimming * ' jjg Colored setting 120 Ganged setting 120 Gauged putty set ^2i Putty set 121 Internal angles ^21 External angles • ^22 Skirtings I23 Two coat work • ^23 One-and-a-half coat work ^24 Stucco 124 Old stucco 129 Common stucco ^29 Rough stucco ^3Q Bastard stucco ^3^ Troweled stucco ^g. Colored stucco • , gi Method of working cements ^ INDEX PAOB TERMS AND FROCESSES. -Continued. ^gg White cement efflorescence 139 Cornice brackets 140 Cornices 155 Mitring '[[ 156 Mitre mould _ i ,9 Fixing enrichments ^^q Mitring enrichments 1^3 Pugging " * 164 Sound ceilings • 165 Cracked plaster work jg5 Repairing old plaster •' ^^^ Gauged work _ 169 Joist lines on ceilmgs • • yjQ Rough casting . • VARIOUS ME;fDS OF f >^NIKG CO^ NICES, CIRCLES, ELLIPSEb Axm^ ORNAMENTAL STUCCO WORK : ^^^ Diminished columns IgO RunSraiminisheiflut^i column by the Co.- ^^^ lar method ..••••• .200 Diminished fluted pilasters • • • • goo Pannelled coves 204 Diminished mouldings 204 False screed method. . . • • • •;• " \V.„L:' ' " 208 Running double diminished mouldmgs • ^^^ Diminished rule method gll Top rule method • • •• .... 215 Cupola panels and mouldmgs • ^20 Panelled beams INDEX FAOB VAPIOUS METHODS, .ETC.-Conliaued. Trammels for eUiptical mouldings ^24 Templates for elliptical mouldmgs • • • ^gg Plasterer's oval " * ' 233 Coved ceilings • • • ••••■•;;'' ' , . 233 Circle mouldings on circular surfaces. . . . • • • ^^^ Forming niches ::.''"•' "i', 240 rSuS an elliptical mouldmg m situ -*» MISCELLANEOUS MATTERS : .... 243 Depeter 243 Sgraffitto *.'.'.'.'.".'.. 251 Fresco 255 Fresco secco ••••••••••* i * V ' 256 Indian fresco and marble plaster ;;'..... .260 Scagliolia 262 Artificial marbles '.'.... 263 Pick's neoplaster 264 Scagliolia manufacture 270 Mixing •. • ■ . " . 272 Colors and quantities 275 Polishing white scagliolia 276 Polishing scagliolia 277 Marezzo 282 Granite finish 283 Granite plastering Ll'i„ n^n. CEMENTS AND CONCRETES AND HOW TO USE THEM : 291 Fine concrete 293 Matrix 294 Aggregate 295 Porous aggregates 296 Compound aggregates 297 Sand and cement " 300 Fire-proof aggregates 302 Voids in aggregates • gQg Crushing strength of concrete INDEX CBJAFNTS AND CONCRETES.-Continued. ^^^ Water for concrete 3Q5 Gauging concrete ' " 308 Ramming concrete 3(j9 Thickness of concrete paving ^^^ Concrete paving 313 Eureka paving ] 313 Eureka aggregate 3^4 Eureka quantities " ' 3j5 Levels and falls ' 31g Pavement foimdations ' • 3^^^ Screeds and sections • 320 Laying concrete pavements • ^21 Troweling concrete ' ' * . . 322 Grouting '/..,.. 322 • Dusting . . 322 Temperature 323 Non-slippery pavements 323 Grooves and roughened surfaces ^^5 Stamped concrete '" 325 Expansion joints 328 Washing yards " 328 Stable pavements 329 Concrete slab moulds 3gQ Slab making • • ". '. 330 Induration concrete slabs ''*.'... 331 Mosaic * _ 333 Concrete mosaic . ... • • • • • 334 Concrete mosaic laid in situ gg^ Storing cement 337 Cement mortar 33^^ Mixing ' ' . . . 339 Grout • ... 339 Lime and cement mortar ggg Cement mortar for Pla^*^"^;,- -„. [/, UO Materials for making concrete ^a"^- ' ' ' " ' ' ;• * 341 Gravel gwrAnm or Cowirmi*" EHTAKATUM AKn PU.« Or CO«N.C. AT EXT..«L A«6t^ rtATKi OKVLU MOBtlinfOI on Cl«COtA» 8»«rACI». la. .|.-ltnAiini or ShaU Covi, wrm Stcnoai. -_._ S^' fc m-r o» Um Cm, mt. toctiM mo Eu«tioii o. Um» Cw»ici. ^^^ PLATE m .!H -••iJMCaHM ■M* INDEX CEMENTS AND CONCRETES.— Continued. Crushed stone ^ Stone versus gravel «♦* Columns and piles '^^^' Floors, slabs and roofs • • ^^^^ Beams ^1 ^' Arches ^,' . Lintels ■!-.- Concrete walls -''^ Strong rooms *i*j Concrete coffins and cementation ^'J^ Tile fixing '* ' ' Setting floor and wall file 479 Foundations ^^j* Lime mortar *2'; Concrete 480 For floors J^ For wood floors *^Y In old buildings 481 For hearths J^ For walls -J"* Cement *°J Sand 486 Mortar ***• \ INDEX n CEMENTS AND CONCRETES.-Continued. ^ Soaking ^g Tilea for floors J^ Ceramics •.•••: aqo Piles for walls and wainscoting ^ Floating wall tile „ Buttering wall tiles Hearth and facing tile ^^^ Cleaning ^^2 Cutting of tile ^^2 Tools AM Laying tile on wood ^^^ Good concrete ^^ Eeinforced concrete