UNIVERSITY OF CALIFORNIA ARCHITECTURAL DEPARTMENT LIBRARY CLASS GIFT OF Mrs. George Beach From the collection of the z n m relinger Jjibrary t P San Francisco, California 2006 CONCRET BY JOHN C. TRAUTWINE, JR. ' AND JOHN C. TRAUTWINE, 3D. CIVIL ENGINEERS FIRST EDITION, SECOND THOUSAND REPRINTED FROM TRAUTWINE'S CIVIL ENGINEER'S POCKET-BOOK TRAUTWINE COMPANY 257 S. FOURTH STREET PHILADELPHIA CHAPMAN & HALL, LTD. RENOUF PUBLISHING CO. LONDON MONTREAL 1909 CORRECTED 1916 T7 Copyright 1909 by JOHN C. TRAUTWINE, JR. AND JOHN C. TRAUTWINE, 3o. WM. F. FELL COMPANY ELECTROTYPER8 AND PRINTERS PHILADELPHIA MURPHY-PARKER CO. BINDERS PHILADELPHIA PREFACE. In the nineteenth (1909) edition, 100th thousand, of our Civil Engineer's Pocket-Book, the most notable of the new features is the series of articles on Concrete (plain and reinforced), including Cement, Sand and Mortar. Practically all of this matter (occupy- ing about 200 pages), altho by no means original, is entirely new, so far as our publications are concerned. In compiling it, our object has been to present, in convenient and condensed form, the essentials of existing knowledge and opinion in regard to these subjects. Special attention has therefore been given to the rules and results of modern practice in concrete construction ; a feature which is reflected thruout the text and especially in the "Selected Results of Experiment and Practice," pp 1135, etc., and in the "Digest of Specifications," pp 1184, etc. These contain, we believe, a more complete and more conveniently classified presentation of modern practice in concrete than is to be found elsewhere in equal space. To attain this, great care has been taken jo to arrange the material as to give maximum density in the resulting text, and maximum convenience for reference. In the selection of "results of experiment and practice," we have had in mind not only the weight and standing of the authorities quoted, but also the importance of covering, as nearly as possible, the entire field of practice, with its very numerous and diversified problems. For reasons explained on p 1140, it was found impracticable to arrange these results in satisfactory logical order, and they are therefore furnished with a special and very complete table of contents, or "Directory," pp 1135-1139, arranged in practically the same order as are the articles on cement, etc., pp 930, etc., and on concrete, etc., pp 1084-1134. It is believed that, in connection with this ' ' Directory, ' ' the ' ' selected results ' ' will be found a very useful feature. Similarly, the concrete specifications have been selected from different lines of work, including not only U. S. Government 81239! iy PREFACE. operations and the building codes of the larger cities, hut the care- fully prepared rules of consulting engineers and experts in concrete. As in the case of our digests of specifications for trusses and build- ings, etc., prepared for our 18th Edition (1902), these digests are "by no means mere quotations from the originals; but, as their name implies, the result of careful digesting of the contents of the specifications selected for the purpose ; their several provisions being carefully studied, in nearly all cases re- worded or reduced to figures, and tabulated in form convenient for reference, the whole being arranged in such logical order as to facilitate reference." The specifications include those for concrete blocks and for concrete sidewalks, adopted by the National Association of Cement Users at Philadelphia, January, 1908. With these exceptions, and those of beams and columns, we refrain from extended discussion of special works (such as arches, dams, etc. ) in concrete ; confining ourselves, for the present, to the material itself and its constituent parts. Under Cement, the Committee Report of the American Society of Civil Engineers, submitted in 1885, has been replaced by that of the later Committee, submitted in 1903 and amended in 1904 and in 1908. The recommendations of the Board of U. S. Engineer Officers, 1901, are retained ; and those of the American Society for Testing Materials (1904, amended 1908) and of the Engineering Standards Committee of Great Britain (1904) are added. Owing to the nature of the materials involved, the theory of concrete design and construction is less firmly established and less capable of satisfactory demonstration than that of other branches of engineering. m We have therefore avoided useless refinement and expenditure of space upon this branch of the subject, devoting ourselves chiefly to its practical side ; but we have nevertheless endeavored to state, clearly, succinctly, and in form convenient for reference and use, the commonly accepted theories, as they affect the principal features of practice. In the article on Cost of Concrete, pp 1207-1210, we have aimed to give merely the ranges of cost to be expected in different features of concrete work, keeping in mind those differences of condition which so largely affect the several items of cost. We have of course drawn freely upon the existing literature of concrete. In giving credit for material so used, we have aimed to err upon the side of liberality, not only as a matter of justice to the authorities quoted, but also for the convenience of those of PREFACE. V our readers who may wish to study the sources of our information in further detail. With the same object in view, we give these references with full detail as to volume, page, date, etc. ; and it is therefore hoped that these articles, together with the references under " Bibliography, " may serve, to some extent, as an "Index to Current Literature" on the subject of concrete. For convenience of reference we reprint here also, from The Civil Engineer's Pocket-Book, pp 454 to 461, remarks on the general principles of the strength of materials, and, pp 494 a to 494 h, on diagonal stresses in beams. For economy of space we not only (as heretofore) use such obvious abbreviations as cen, diag, hor, vert, cem, agg, cone, etc., but we frequently drop qertain letters which (like "ugh" in "though") are as useless as the "k " which our forefathers considered essential in "niusick," or the "u" which our English cousins still like to use in ; ' honour. ' ' The same consideration of space has led also to the liberal use of symbols, such as D for "square," D" for "square inch," / for "per," > < > and < for "more than," "less than," "not more than" (equal to, or less than), "not less than" (equal to, or more than), respectively. In connection with the theory of reinforced concrete we have been forced to the extensive use of letters with subscripts, as/ s , E c , etc., etc. We have made special arrangements to secure the great- est possible legibility for these characters, as well as in connection with the symbols, mentioned above. In this reprint, the paging is that of the Pocket-Book ; and the matter is here accompanied by the appropriate portions of the Table of Contents, Price List, Business Directory, Bibliography and Index of that work. Our acknowledgments are made to many who have assisted us in our labors, notably to Professors A. W. French and L. J. Johnson, and to Messrs. J. Y. Wheatley and Wm. H. Balch. JOHN C. TKAUTWINE, JR., JOHN C. TEAUTWINE, 3D. PHILADELPHIA, September, 1909. CONTENTS. In this reprint, the paging is that of Tbe Civil Engineer's Pocket-Book. See Index. STRENGTH OF MATE- PAGE General Principles. Stress and Stretch ........... 454 Elastic Modulus ............. 456 Elastic Limit ................ 459 Elastic Ratio ................ 459 Yield Point ................. 460 Resilience .................. 460 Suddenly Applied Loads ...... 461 Transverse Strength. Diagonal Stresses 494o Horizontal and Vertical Shear 494c Maximum Unit Stresses 494e Moments in Continue us Beams 4940 CEMENT MORTAR. Cement. Materials 930 Manufacture 931 Natural and Portland 931 Puzzolana 932 Silica Cement 932 Other Cements 933 Composition 933 Properties 934 Packages 935 Age 935 Testing 936 Specifications Requirements U S Engr Officers 937 Am Soc Test Materials . . . 940 Engng Standds Comm of Gt Brit 940 Tests Am Soc Civ Engrs 942 Sand. Composition 946 Sizes of Grains 946 Density 947a Other Properties 947c Mortar. Constituents 947d Amount Required in Masonry . Cement ' .947d Sand 947e 947e Lime . . . . . .947/ Consistency '. " .947/ Setting and Hardening Soundness .... .947/ 947/1 Strength Finish . .... .947* 947? Behavior in W'ater .947Jfc CONCRETE. Aggregates 1084 Size 1084 Density 1084 Cyclopean 1085 Constituents 1086 Advantages 1086 Proportions 1086 Materials Required 1087 Voids 1088 Density 1089 Consistency 1090 Handling and Mixing 1090 Handling Ingredients 1090 Mixing 1092 Mixers 1092 Placing 1093 Forms. . 1094 For Buildings 1095 Lumber for 1097 Strength 1098 Details 1098 Adhesion 1099 Removal 1099 Joints 1099 Ramming 1100 Placing under Water 1100 Surface Finish 1102 Properties 1103 Weight - 1103 Permeability 1103 Elastic Modulus 1106 Strength 1106 Setting 1106 Effects of Heat and Cold 1107 VI CONTENTS. Vll Protection . . PAGE 1107 Placing etc PAGE 1189 Expansion 1108 Joints ..1190 1108 Under Water. . .1190 Tests in Place 1109 Rain 1191 Frost . . 1191 Moistening . .1191 Reinforced Concrete . Removal of Forms . .1191 Expansion, Contraction, etc . . Adhesion 1110 1111 Finish, Waterproofing, etc. . . Artificial Stone ..1192 1193 1112 Strength. 1193 Hooped 1113 1115 Permissible Loads Elastic Modulus. . . ..1193 1194 Theory Tee Sections. . . 1115 1122 Safety Factors Reinforcement. . . . .1194 1194 Shear 1123 Permit 1196 Reinforcement 1124 Clearance 1196 Unit 1125 Columns . .1197 Diagonal Stresses 1125 1126 Beams Slabs . .1198 1199 Continuous Beams 1126 Continuity 1200 Methods 1127 Tests 1200 Bar Web * 1128 1132 Sidewalks Blocks. . . . .1201 1203 Trussed With Structural Shapes 1133 1133 Column 1134 Cost Materials 1207 Experiments. Directory Results 1135 1140 Transportation Storage Mixing and Placing Forms . .1208 . .1208 ..1208 1209 Miscellaneous 1210 Specifications. Alphabetical List 1184 Total . .1210 Classified List Contents 1185 1185 1186 PRICE LIST 1301 Sand 1186 Aggregate Consistency 1186 1187 BUSINESS DIRECTORY.. . . 1307 Mixing 1188 Forms. . . .1189 INDEX. NOTICE. The following pages are selected from those of The Civil Engineer's Pocket-Book, and they are numbered similarly with the corresponding pages in that book. IX > if* : 2 454 STRENGTH OF MATERIALS. STRENGTH OF MATEEIALS. GENERAL PRINCIPLES. Stress. 1. Stress occurs when forces act upon a body in such a way that its particles tend to move simultaneously with different velocities or in differ- ent directions; to do which, the particles must change their relative posi- tions. This occurs, for instance, when a body is so placed as to oppose the relative motion of two other bodies; as when a block is placed between a weight and a hor table. Here the two bodies (the wt and the table) tend to come closer together; but they cannot do so without distortion of the in- tervening block; and such distortion is resisted by internal forces, act- ing betw the particles of the block and tending to keep those particles in their original relative positions. The action of these internal forces is called stress.* 2. Similarly, if a body be suspended by a long chord, and if we push or pull the body to one side, the particles, on the side acted upon, will first tend to move, and the transmission of this tendency to the remaining par- ticles causes stress within the body. 3. For internal equilibrium, the internal stresses must balance the external forces. Hence, it is not unusual to apply the term, "stress," indifferently to either. 4. Let the two forces, a and b, Figs A, B, acting upon the body, o, meet at an angle, a o b. Then the two equal and opposite components, a" o and b" o, cause compressive or tensile stress in the body, o, as in H 1; while the other two components, a' o and b' o, unite to fprm the resultant, c o, which, unless balanced by other forces, moves the body, o, in its own direc- tion, causing, as in H 2, another comp stress, Fig A, or tensile stress, Fig B. Fig. B. 5. Upon any plane within a body, a force may act (1) normally, (2) taiigentially, or (3) obliquely. If it act obliquely, it may be resolved into two components (see Statics, H 65, p 372), one acting normally and the other tangentially, upon the plane. 6. Consider the two portions into which the body is divided by such a plane, Then (1) forces, acting normally upon the plane, produce ten- sion (or compression) in the plane, tending to separate the two por- tions (or to push them closer together); and (2) forces, acting tangentially upon the plane, produce shear (or torsion) in the plane, tending to slide the two portions one past the other in a straight line (or with a twisting motion). Torsion occurs in planes betw and parallel to two con- trary couples, as in cross sections of a hand-brake axle when the brake is applied. 7. Thus, if an iron bar be pulled (or pushed) lengthwise, its cross sections sustain normal tension (or compression). If it be sheared across (or twisted), the cross sections, between and parallel to the two shearing (or twisting) forces, sustain shearing (or torsional) stress. 8. At any point, in the circular path of a torsional stress, we may consider the tangents to the path as representing shearing forces. Torsion is * In every-day language, and often in the writings of engineers, this action of the internal forces, or the external force causing it, is called "strain"; but scientists apply the word " strain " to the deformation occurring under stress. See "stretch," HI H etc. GENERAL PRINCIPLES. 455 therefore merely.a shearing stress in which the direction changes at each point. 9. Transverse stress. In Fig 124, p 438, the two equal and parallel forces, W and R, in opposite directions, cause a tangential or shearing stress, . = W = R, in the vertical planes lying between their lines of action; but W and R, as a couple, have a moment, which, for equilibrium, must be re- sisted by the equal and opposite moment of another couple, as C and T; and the opposition of these two couples causes normal (comp and tensile) stresses in the same vert planes parallel to and betw W and R. 10. The ultimate tendency of any opposing external forces is to fracture the body by increasing the distances between its particles. Even under compressive stress, rupture can occur only by separation of particles. Stretch. 11. When the internal stresses and the external forces are in equilibrium, no distortion takes place; but, at the instant when opposing external forces are first applied to a body, the internal stresses are not yet developed, and distortion begins, under the unopposed action of the external forces. See 1111 35 etc. But the stresses are brought into action by the distortion, and they increase with it; and, if the external force is not increased beyond the elastic limit (1J 26) the stresses finally equal the external forces, and prevent further distortion. Strctvh. 1OOO e = 1OOO l/L 100 150 200 250 1.0 1.5 2.0 Stretch, JOOO e 1OOO l/L Fig. C. Behavior under Normal Stresses. 12. Fig represents the behavior of a typical material (mild steel) under tension. From to A, i.e., under stresses up to the elas- tic limit (If 26), say 34,000 Ibs per sq inch, the stretch progresses propor- tionally with the stress, as indicated by the straight line, A. (The earlier portions of the process are represented, in the lower diagram, to a scale of stretch 100 times as great as that of the upper diagram. 1 After passing the point A, the stretch increases faster than the stress; and, betw B and B', the stretch (in iron and steel) increases with little or no increase of stress, or even under a slightly diminishing stress.* B is called the yield point. See U 31. The scale of the lower diagram does not extend to B'. Beyond B' (upper diagram), the stretch increases much less rapidly than betw B *See tH 16, 17 30 456 STRENGTH OF MATERIALS. and B', and remains, for a time, nearly proportional to the. stress* (though much greater, relatively to stretch, than in A); but the stretch now pro- ceeds faster and faster, and in increasing ratio with the stress, until the stress reaches its maximum or ultimate value (say 70,000 Ibs per sq inch) at C. At C, the stretch is increasing without increase of stress (diagram horizontal); and, beyond C, the stretch continues increasing altho the stress is diminishing, until, finally, at D, rupture occurs. 13. If, after passing the elastic limit, the bar is relieved from stress, as at F, Fig C, lower diagram, its recovery is incomplete, the length remaining somewhat greater than in its original unstressed condition. The permanent increase, F', is called the permanent set, or simply the set. The line F F' is, in general, approx parallel to the line, A, of elastic stretch. W hen the same stress is again applied, the stretch is greater than before, by a small amount represented by F F". 14. When the stress is within the elastic limit (If 26), the recovery, upon release from stress, is so nearly complete that the per- manent set cannot be indicated in our Figs. (U 28.) 15. Under tension, the sec area is diminished, and, under compression increased. In ductile materials, under tension, the reduction of sec area is very marked, especially along a relatively short portion of the length, usually near the middle of said length; and fracture occurs normally at the point of maximum reduction. 16. In Fig C, both diagrams, and, in Fig D, the solid curves, represent the nominal unit stresses, or those usually stated. These are found by dividing the total stresses, respectively, by the original section area, as in If 18. 17. The dotted curves, Fig D, represent the actual unit stresses, found by dividing the total stresses, respectively, by the actual section area, as diminished or increased by stress. Under tension, the actual unit stresses are of course greater, and, under comp, less than the corresponding nominal unit stresses. Negative stretch Stretch li Fig. D. Elastic Modulus. Fig. C. 18. Let P = the load (one of the two equal and opposite external forces) acting at one end of a bar and in line with the axis of the bar; and let a = the original* cross-section area, or section area, of the bar, normal to its axis. Then, s, = P I a, is the normal stress per unit of area, or stress intensity, or normal unit stress, in the bar. We assume that, so long as the external force acts axially, P is uniformly distributed over a, altho this is seldom strictly the case in practice. *See HH 16, 17 GENERAL PRINCIPLES. 457 19. Let L = the original length of the bar, or of some designated portion of that length, and I = the stretch * which takes place, in the length, L, under the action of a given unit stress, s. Then, e, = I / L, is the stretch per unit of length, or unit stretch,* corresponding to the unit stress, s. 20. In many materials, the unit stress, s, and the unit stretch, e, at first increase proportionally, the ratio, s/e, or unit stress -;- unit stretch, remain- ing practically constant. This ratio is called the elastic modulus, and is designated by E ; or Elastic modulus = E = s/e =-= unit stress -5- unit stretch. 2O a. The elastic modulus is thus proportional to the tangent of the angle, X A , Fig C, the proportion depending upon the scales adopted . 2O b. The elastic modulus, E, increases with the unit stress reqd to pro- duce a given unit stretch. Hence E is a measure of the stiffness of a body, i.e., of its ability to resist change of shape. ".Stiffness modulus" would have been a better name. 2O c. If equal additions of stress could indefinitely continue producing equal additional stretches in a bar, beyond as well as within the elastic limit (H 26), then a stress, equal to the elastic modulus, would double the length of a bar when applied to it in tension, or would shorten it to zero in compression. 2O d. For example, within the elastic limit, a one-inch square bar ot rolled steel will stretch or shorten, on an average, about Q of its length under each additional load of 1000 Ibs. If it could stretch or shorten in- definitely at the rate of of its original length for each 1000 Ibs. of added load, then 30,000 times 1000 Ibs., or 30,000,000 Ibs., (which is about the average modulus of elasticity for such bars) could either stretch the bar to double its length or reduce it to zero. 2O e. If equal infinitesimal stresses, applied to a bar, could indefinitely produce stretches, each bearing a constant ratio to the increased length oi the bar, if in tension; or to the diminished length, if in compression; then the same load which would double the original length of the bar, if applied in tension, would reduce it to half its original length, if applied in compression. *We regard shortening, under compression, as negative stretch. 458 STRENGTlf OF MATERIALS. 21. In a prismatic bar, under longitudinal tension or compression, let W = the total load ; a = the cross section area ; a = = the unit stress = the stress per unit of area ; a L = the original length ; I = the stretch * ; e = if L = the unit stretch * = the stretch * per unit of original length ; E = the elastic modulus of the material ; r = E a = a measure of the resistance of the bar. Then Tot al load W a E a I (2) W ' L = E e . (3) Total stretch* 1 a W L a E'" L (5) 1 ii if vt !<>! <-ll * I E"" W 8 (6) 22. In a beam, supported at, both ends and loaded at the center, let L = length of clear span of beam ; w = weight " " " " " ; A = deflection ..... ' " " ; b = breadth of cross section of beam ; d = depth ..... ' ; / = moment of inertia " " " " " . Then F = ( W + 5/8 w} L3 '48 A / b d 3 If the beam is rectangular, / = y^- (p 469), and _ 12 (W + 5/8 w) L* _ (W + 5/8 w}L* 48 A b <*> , 4 A frd 3 For beams, see also pp 480-481. 23. Reciprocal of elastic modulus. The>lastic modulus, = ' mc ^ cates t ^ ie 8tre88 required to produce a certain distortion. Its reciprocal, = Umt stretch S h ws to what extent a bar etc of a unit stress therefore, a relatively great distortion must take place before a given fiber stress (such as the maximum safe fiber stress) can be brought into action. Thus, in the case of a wharf, supported by long timber piles, the piles may submit to so great a lateral deflection as to give the load, resting upon them, a dangerously great horizontal leverage, and thus a dangerous overturning moment. * Compression is regarded as negative stretch. GENERAL PRINCIPLES. 459 24. Variable elastic modulus. Fig 11, Concrete experiments 81a p 1172, shows an example (in both tension and compression) of a material in which the elastic modulus, E, is constantly changing; the stretches, from the first, increasing faster than the stresses. 25. Even in the case of ductile materials, the stretches, produced by stresses within the elastic limit (If 26), are so small and so irregular that a satisfactory average value of the elastic modulus can be arrived at only by comparing the results of many experiments. In the case of brittle materials, where scarcely any perceptible stretch takes place before rupture, the deter- mination of the elastic modulus is very uncertain. Elastic Limit. 26. The stress, A, Fig C, beyond which the stretches in any body increase perceptibly faster than the stresses, is called its elastic limit, or limit of elasticity. Owing to the irregularity in the behavior of different specimens of the same material, and to the extreme smallness of the distor- tions caused in most materials by moderate loads, and because we often cannot decide just when the stretch begins to increase fastei 4 than the load, the elastic limit is seldom, if ever, determinable with exactness and certainty.* But by means of a large number of experiments upon a given material we may obtain useful average or minimum values for it, and should in all cases of practice keep the stresses well within such values; since, if the elastic limit be exceeded (through miscalculation, or through subsequent increase in the stress or decrease in the strength of the material) the structure rapidly fails. The table, p 460, gives approximate average elastic limits for a few materials. The elastic limit, as here defined, is sometimes called the " true " elastic limit. Compare If 31. 27. Brittle materials, such as stones, cements, bricks, etc., can scarcely be said to have an elastic limit; or, if they have, it is almost impossible to determine it; since rupture, in such bodies, takes place before any stretch can be satisfactorily measured. 28. A small permanent "set" (stretch) probably takes place in all cases of stress even under very moderate loads; but ordinarily it first be- comes noticeable at about the time when the elastic limit is exceeded. The elastic limit is sometimes defined as that stress at which the first marked permanent set appears. 29. The elastic ratio of a material is the quotient, It is usually expressed as a decimal fraction. The permissible working load of a material should be determined by its elastic limit rather than by its ultimate strength. Hence, other things being equal, a high elastic ratio is in general a desirable qualification; but, on the other hand, it is possible, by modifying the process of manufacture, to obtain material of high elastic ratio, but deficient in "body" or in resil- ience i. e., in capacity to resist the effect of blows or shocks, or of sudden application or fluctuation of stress. See If 34; also 111(35 etc. In the manufacture of steel, the elastic ratio is increased by increasing the reduction of area in hammering or rolling, and the rate of increase of elastic ratio with reduction of area increases rapidly as the reduction becomes very great. Kirkaldy found t for steel plates 1 inch thick, mean elastic ratio = 0.53 ..... ' H " " " " " = 0.53 ...... V* " " " " " = 0.54 " M " " " " " = 0.61 *The U. S. Board appointed to test Iron, Steel, &c., found a variation of nearly 4000 Ibs. per square inch in the elastic limit of bars of one make of rolled iron, prepared with great care and having very uniform tensile strength; and, in another very carefully made iron, a difference of over 30 per cent. between two bars of the same size. Report, 1881, Vol. 1, p. 31. t Annual Report of the Secretary of the Navy, Washington, 1885, Vol. I, p. 499; and Merchant Shipping Experiments on Steel, Parliamentary Paper, C. 2897, London, 1881. C2 460 STRENGTH OF MATERIALS. 3O. Elastic Moduli and Elastic Limits. Approximate averages, t E = elastic modulus, in millions of pounds per square inch ; I = stretch or compression, in ins, in a length of 10 feet, under a load of 1000 pounds per square inch. = (10 X 12 X 1,000) -*- (1.000,000 E) ; *r = stress at elastic limit, in thousands of pounds per square inch. m I *e Metals. 10 to 30 012 to 0.004 4 to 8 *' " ordinarily . ... 12 to 15 0.010- to 0.008 6 to 7 27 to 31 0.004 20 to 40 Steel structural* " to " 34 to 38 8 to 10 015 to 0.012 5 to 7 ** wire . 12 to 16 0.010 to 0.007 14 to 18 10 to 14 0.012 to 0.009 6 to 7 10 to 14 0.012 to 0.009 8 to 12 Lead 8 to 10 150 to 0.120 1 to 1.2 Tin cast 6 to 7 0.020 to 0.017 1.4 to 1.6 13 to 15 0.009 to 0.008 14 to 15 Stones etc f 4 to 8 0.030 to 0.015 1 to 2 5 to 2 0.240 to 0.060 Art. 4 (h) wSdjT.1 .""..::: """". 1.5 to 2 0.080 to 0.060 5 to 7 31. Yield point. Commercial, Relative or Apparent Elas- tic Limit. In testing specimens of iron and steel, it is commonly found that, at a stress slightly exceeding the true elastic limit (^26), the stretch begin! to increase without further increase of load. This point is usually called "the yield point," or " the elastic limit" in commercial testing. The French Com- mission on Methods of Testing the Materials of Construction called it the " apparent elastic limit." The late Prof. J. B. Johnson (" The Materials of Con- struction," New York, John Wiley & Sons, 1906, p. 19) applied the term, " rela- tive or apparent elastic limit" to that point on the stress diagram at which the rate of deformation is 50 per cent, greater than at points below the true elastic limit. Resilience. 32. The resilience of a bar, under a stress, s, is the work done, upon the bar, in producing that stress, or, theoretically, the work which the bar will do, in regaining its original shape, when relieved from stress. Usually we are concerned with the elastic resilience, or that corresponding to the stress, e at the elastic limit. 33. Let s e = the unit stress at the elastic limit ; a = the section area of the bar ; P g = a s e = the load corresponding to s e ; L = the original length of the bar ; I = its stretch, at the elastic limit ; E = the elastic modulus. *In rolled iron and steel, the elastic modulus is remarkably constant for all grades. In wrought iron, the elastic limit depends chiefly upon the degree of reduction of cross section in rolling; the smaller sizes having the higher elastic limit. In steel, this effect is less marked. t See UH 25, 26. Jin wood, "the extreme fiber stress at the true elastic limit (*[f 26) of a beam Is practically identical with the compressive stress endwise of the material," table, p. 958. See discussion by S. T. Neely, in "Timber Physics," 1889 to 1898, by Filibert Roth, House Document No. 181, 55th Congress, 3d Session, Wash- ington, 1899, p. 374. GENERAL PRINCIPLES. 461 The work has been done by the mean load, P e /2 = a s e /2, acting thru the dist, I = L s e /E. Hence, Resilience = K = P e 1/2 = a s e L s e /2 E = (sJ/2 E) a L. 34. Here s//2 E is the resilience modulus = resilience of a bar of unit section area and unit Igth. The resilience modulus of a material is a measure of its capacity for re- sisting shocks or blows. Suddenly applied loads. 35. Let a body, of weight, W, be suspended by a string, and let it just touch the scale-pan of a spring balance, without depressing it. Now let the string be cut with a pair of scissors. 36. At the moment of cutting, the spring has not been stretched; its resisting stress, S, is therefore zero, and the net or resultant downward force, acting upon the body, is F = W S = W = W. 37. Under the action of this force, the spring stretches, and S increases proportionally with the stretch. Hence (W remaining constant) the re- sultant downward or accelerating force, F, acting upon the body, decreases until S = W, when F = W S = W W = 0. 38. The body, having thus far been constantly accelerated, (by a dimin- ishing force, F), has constantly increased its velocity. Let h = the height thru which it has now fallen, and let x be the point reached, at the end of h. 39. Beyond x (W remaining constant, while S continues to increase), the moving body is acted upon by a constantly increasing, retarding up- ward force, F = W S, which brings it to rest at a second point, z, at the end of a second distance = h. Its total fall is therefore 2 h. 40. Let S max = the max value of S, or that at the end, z, of the fall, 2 h. Then, since S has increased proportionally with h, its mean value, during the fall, 2 h, was S max/2; and the work done, during the entire fall, 2 h, was 2 W h = (S max/2) 2 h = S max X h. Hence, S max = 2 W. 41. At the end, z, of the fall, 2 h, the body, having come to rest, is acted upon by an upward force, F = W S max = W 2W = W; and (neglecting friction) the same performance is now repeated, but in the up- ward direction, and so on indefinitely. 42. But losses of energy, due to air resistance and to internal friction, render each oscillation less than its theoretical value ; and the body therefore finally comes to rest at the point, x, midway of the fall, 2 h. 43. Thus (If 40), within the elastic limit, a load, suddenly applied (tho without shock) produces temporarily a stretch nearly equal to twice that which it could produce if applied gradually ; i.e., twice that which it can maintain after it comes to rest; and develops temporarily, in the stretched body, a resisting stress = twice the load. 44. If the load be added in small instalments, each ap- plied suddenly, then each instalment produces a small temporary stretch, and afterward maintains a stretch half as great. Under the fast small instalment of load, the spring stretches temporarily to a length greater than that which the total load can maintain, by an amount equal to half the small temporary stretch produced by the sudden application of the last small instalment. DIAGONAL STRESSES IN BEAMS. 494 a DIAGONAL STRESSES l\ BEAMS. Maximum Unit Stresses. 104. When a body (as a bolt) is under tensile (or comp) stress only, the tendency of the body, as regards sections normal to the stress, is to pull apart (or crush together) in the direction of the stress, or normally to the section, and the entire stress acts normally upon the section; but, on planes oblique to the stress, the stress is resolved into two components, one (n) of tension (or comp) normal to the plane, and one (0 tangential to the plane (shearing stress). 105. Under shearing 1 stress alone, the effect, upon a plane parallel to & betw the 2 shearing forces, is pure shear; but, upon planes oblique to the forces, the shearing forces are resolved into (t) tangential or shearing stresses, and (n) normal (tensile or comp) stresses. If' Fig. 17. 1O6. Thus, Fig 17, let a bar, of length, L, and depth, D, be subjected to a tension, S = S', in line with its hor axis, and to two pairs of forces, V= V' and H = H', as shown; V and V constituting a right-hand vert shear, while H and H' constitute a left-hand hor shear. Suppose the bar divided by a section, as N N, F G or K M, and consider the forces acting, in either case, upon the right-hand segment of the bar as thus divided. Upon the normal section, N N, the tension, S, and the hor shear, H, act normally (S as tension, H as compression), and the vert shear, V, tangen- tially (as shear); but, for an oblique section, F G or K M, we first resolve each force, S, V and H, into two components, b and y, c and z, a and x, respectively normal and parallel to the section, as shown by the force-triangles on the right.* Then, summing these comps, algebraically, we obtain the resultant forces, P n (normal) and P t (tangential or shearing), acting upon the section in question. With the forces, S, V and H, as shown in Fig 17, we have: On sec F G, + z P t , right-hand shear, = a + c b ; On sec K M, P n , compression, = a + c b ; P t , right-hand shear, = y + z x. 1O7. If, now, we examine all possible planes cutting the body at a given point, we shall find (1) one such plane upon which the resultant unit tensile stress reaches its max; (2) another, normal to (1), upon which the resultant unit comp stress reaches its max; and (3) two planes, normal to each other & bisecting the right angles betw planes (1) & (2). Upon the two planes last named, (3), the resultant unit shearing stresses reach their max. *In order that, for either force, S, V or H, the two force-triangles (for the two sections, F G and K M) may be identical, and thus simplify the figure, we take the two sections, F G and K M, normal to each other. 4945 STRENGTH OF MATERIALS. Fig. 18. 1O8. Let Fig. 18 represent a small element in a bar under tensile & shearing stresses; and let it be required to determine the positions of these planes and the corresponding- max stresses. Let s = the original normal (tensile or comp) unit stress ; v = " " vertical (shearing) unit stress ; = h = " " horizontal (shearing) unit stress ; s = " max or min resultant normal unit stress ; v r = " max resultant shearing unit stress ; = " angle betw s and s Then CD If 8 is! ' ]/ (s/2) 2 + v* (2) lax = s/2 + V T = s/2 4- ;/ (s/2) 2 + v 2 (3) iin = /2 v r = s/2 l/ (8/2) 2 + v 2 (4) ' tension sign gives max tension ' comp = min tension f + ' comp { " " ' tension = min comp. 1O9. Example. Let 8 = 2000 Ibs/sq inch, tension (not drawn to scale); v = h = 1600 " / " " , shear ( " ' ). Here v is left-handed, h right-handed. If this be reversed, the angle, A, betw the resulting tension, s n , & the hor, will be below the neut axis. 11O. Then tan 2 A = -- = =58; A = 29 V (s/2) 2 + s/2 + s/2 - = v/1000 2 + 1600 2 = 1887; = 1000 + 1887 = 2887 (tension); = 1000 1887 = 887 (comp). 111. In other words, we have, as resultants. (1) a max unit tension, s max = 2887 Ibs/sq in, forming an angle, A = 29, with the axis of the bar or with the direction of s ; (2) a min unit tension or max comp, s min = 887 Ibs/sq in, normal to s max; (3) a right-hand unit shear, v f = 1887 Ibs/sq in; and a left-hand unit shear, v = 1887 Ibs/sq inch; the DIAGONAL STRESSES IN BEAMS. 494 C directions of the shearing stresses bisecting the right angles betw the max normal stresses. 1 1 2. The max tension and compression, at any point, are called the ** principal stresses " for that point. Horizontal and Vertical Shear in Beams. See also pp 440 &c, 446 &c, 450 to 453, 478-9. 113. Let Fig. 19 represent the left half of a homogeneous beam, of rectangular section; breadth, b, = 1 inch; depth, d, = 10 ins: span, L, = 100 ins; with cen load, W* of 200 Ibs; left reaction, R = W/2 = 100 Ibs. Weight of beam neglected. The bendg mom, at cen of span, is M = RL/2 = PFL/4* = 5000 inch-lbs; and the mom decreases uniformly,* from its max, at cen of span, to zero at the supports. In the extreme upper & lower fibers, the longitudinal unit stress, (T 10, p 468) s, = MT/I, where T = df2 = dist from neut axis to extreme fibers = 5 ins; / = inertia mom of cross section = bd*/12 = 1000/12. Hence, in Fig 19, s = 12 X 5 M /1000 = 0.06 M. Now s, being thus proportional to M, also decreases uniformly,* from its max, at cen of span, to zero at the supports. Values of M and of s, for the sections 0, a, b, c, d, e, are figured on the diagram. d - _. h~~*-::l _.--.-. - % i ' _==- : _-4 ~- =--- K T"~" \ \ 8 i % w ^=~ [ n \ '/ / / /' K ^ o /\ ^^ : T I / ' '' ; i / 1 Avis / ~/? j V- * it* :i i \ 10" 2 1000 20 60 IS 0" 3 00 30 JO li L w" 0" 41 00 40 50 24 3" 5 00 50 Q 3( 0" S? z w Fig. 19. * Under a uniformly distributed load, the bendg mom, at cen of span, is WL/8; and the bendg moms, M, and the resulting longitudinal unit stresses, s, vary as the ordinates of a parabola, as indicated by the dotted parabola, r me,at top of Fig 19, which corresponds to a uniform load = 400 Ibs = 2 W, The unit shears, v, in a given hor section, then decrease uni- formly, from a max, at the supports, to zero at the cen of the span. Com- pare 3d and 4th figures, p 474. 494 d STRENGTH OP MATERIALS. 114. The unit hor tensile and eoinp stresses, s, at the several points in any vert section, are proportional to the (lists of those points from the neutral axis, as indicated by the diagram at each vert section, Fig 19. 115. In Fig 20, let n and g be two vert sections of this beam, such that, at n and at g, the extreme unit fiber stresses are: m n = 15, and u g = 25, respectively. Then the rectangular portion, n f, of the beam, betw sections n A g, is acted upon by a series of net or resultant forces, ranging from compression, e g = u g m n = 25 (15) = 10, at the top, to tension, = +10, at bottom, as indicated by the diagram, e k. 116. Suppcfse the piece nf to be divided into 10 hor strips of equal depth, = 1 inch. Then the net unit stresses, s, acting at the tops and bottoms of these strips, respectively, are those, (10, 8, 6, ... .6, 8, 10) figured from e to k; and the mean stress, or (since depth of each strip = 6 = 1) the force, acting upon each strip, is that (9, 7, 5, ... .5, 7, 9) figured betw g and f. 117. These forces are transmitted, from strip to strip, thru their surfs of contact; and, in determining the shearing force, acting in the hor plane betw any 2 strips, we regard the upper (or lower) strip as acted upon by its own push or pull plus (algebraically) those of all the strips above (or below) it. 25- 118. Thus, the 3d strip from the top is pushed to the left by a force of 9 7 5 = 21, while the 4th strip, just below it, is pulled to the right by a force of 9 + 7 + 5 + 3+1 13 = 21. Hence the surf betw the 3d and 4th strips, sustains a counterclockwise shear of 21 ; which, divided by the area, 6 I = I, of that surface, gives the unit shear in the plane betw the 3d and 4th strips. With central load,* this unit shear is uniform from each support to cen of span, where it changes sense (from plus to minus, or vice versa) but is of the same intensity in the other half-span. See 3d Fig, p 474. 119. In any vert section of the beam, let V = the total shear = " reaction of either support, minus the sum of all loads betw that support and the section ; / = " inertia moment with respect to the neut axis; b = " breadth; d = depth ; a = " area above (or below) any given point in the section; c = " dist from neut axis to grav cen of a; M s = a c = static mom of a, with respect to the neut axis; v = the unit vert shear = unit hor shear at a given point. 120. Then * See foot-note p 494 c. DIAGONAL STRESSES IN BEAMS. 494 6 At the neut axis, M g (= a c) Hence, at the neutral avis: v = v * = F - 1 - 2 . * 2 bd = --- X the mean vert shear in the cross section. See also Uf 51 etc. Since, under a center load, (1[ 113 and Fig 19) s increases uniformly, from zero (at support) to smax (at span center), we have, for the increase of , in any portion, as n g = I, Fig 20, of the span : sg sn = Smax /-"TO = ^ smax j- . 131. At the left of Fig. 19 is a diagram showing the unit shears in the several hor sections. 122. Let Fig 21 represent a small element of a body, of unit thickness, normal to the paper, and acted upon by a right-hand vert shear, V = v D, (where v = the unit vert shear, and D = the depth of the element) and by a left-hand hor shear, H = h L (where h = the unit hor shear, and L = the length of the element). For equilib of moments, we must have V L = H D\ orvDL = hLD; or v = h. In other words, unit vert shear = unit hor shear. I Fig. 21. Ufaximum Unit Stresses in Beams. 123. The common theory of beams (pp 466 to 494, t f 1-103) considers only the longitudinal tensile and compressive forces and the vert and hor shearing forces, due directly to the load and to the upward reactions of the supports, and acting, at any point, upon vert and hor planes passing thru such point; but, except in certain limited por- tions of the beam, these stresses are not the maximum stresses act- ing at such point; for they combine to form resultant diagonal stresses, acting upon diagonal planes (passing thru the same point); and, upon some of these diag planes, the resulting normal and tangential stresses are greater than either of the original stresses. 124. The common theory is sufficiently well adapted to beams of many kinds, and especially to steel beams, where the longitudinal forces are resisted by the flanges, and the shears by the web; but in certain por- tions of deep and heavily loaded beams, especially those of reinforced concrete, the diagonal resultant or maximum stresses are the riding stresses, and must not be neglected. 125. In a beam, at top and bottom, we have, respectively, hor tensile and comp stresses only, and, at the neut axis, shear (vert & hor 1 ) only; but, at all other points, we have shear (vert & hor) acting conjointly with hor stresses, either tensile or comp. At all points.these shearing and longitudinal stresses may be resolved into components, normal & tangl to any plane, at pleasure, as in the case of the bar or bolt, Fig 17. 494/ STRENGTH OF MATERIALS. 126. Thus, each element of the beam, Figs 22, 23, 24, is acted upon by hor & vert forces (unit stresses), which, acting upon diagonal planes, are resolved into diagonal components, and these components may be alge- 1 i __ ~-*---'?r g2 ~ V.T-- - "- -c S \ 1 ir /!~I. ,1 I- t J I/ 1 f_ | ''Neutral / / > A ^ZZ"I I JLvi* / -7 <- /* \ i j M 8 = ? = 1 k 10" a 1000 20 60 IS o" a 00 30 JO li I* _ en" 0" 4 {X) 40 50 & 0" 5 00 50 W 3( 0" 00 2 50 " > rig. 22. Section Fiff. 24. braically summed into resultants: but the original stresses vary in intensity, and the resultant stresses both in intensity and in direction, from point to point. For the directions and values of these resultant stresses at their maxima, we have, from Eqs 1-4, fllOS, p 4943: Tan 2 A = -(2) where 8/2 v r = s/2 db l/(/2) s = original unit tensile or comp stress at the point ; v = original (vert or hor) unit shear at the point. The max normal stresses, s~, are called the principal stresses. 127. Applying these formulas at numerous points in the profile of the beam, Fig 22, we are enabled to construct curves. Fig 23, showing the directions of the stresses ; and to plot, as in Fig 24, for given points, the directions and intensities of the stresses there acting. At any given point, Fig 24, we have resultant normal and shearing stresses analogous to those in Fig 18, p 494 6; but, in the present Fig 24, owing to want of space, only the max principal stress, s_ max, is shown for each point selected. DIAGONAL STRESSES IN BEAMS. 494 128. In Fig. 23, the directions of the principal stresses, s p , are repre- sented by the solid curves; those of thie resultant shears, V T , by dotted curves. Of the solid curves (principal stresses) concave horizontal at cen of span at 45 with at 90 with The tension curves are The compression curves are upward downwd below neut axis above ' neut axis top of beam bot " The tensile and comp curves are normal to each other at their intersections. 129. Following any curve (concave upward) of normal tension,* we find that, (1) for its point of tangreiicy with the hor (viz: at cen of span) max = tension = s ; s_ min = comp = ; (2) for the point where the curve crosses the neut axis (at 45) max (tension) = min (comp) = v r v (shear); (3) above the neut axis, the tension becomes s p min, and continues diminishing, as the direction approaches the vert, becoming zero at top, where A = 90. Above the neut axis, for points in the same curve, the compression (normal to the curve) is now s max, and increases from s_ = v r = v, at the neut axis, to s max (comp) = s, at top. 130. Where v = zero (viz: at any point in the vert cross section at cen of span, and along the extreme upper and lower fibers), we have (1{ 126) : v f = s/2 s p max = s/2 + v f = s ; tan 2 A = ; s p min = s/2 v f = ; tan 2 A = 0. 131. The equation, tan 2 A = 0, gives either 2 A = or 2 A = 180; i. e., A 0, or A = 90; but we know that, at cen of span and along the extreme upper and lower fibers, s p max is hor, or A = 0; and min is vert, or A = 90. 132. Where s = zero (as at the neut surf and where bending mom = zero), we have (t 126) : v r = v ; s max = s p min = \/v 2 = +v; tan 2 A = oo ; 2 A = 90 ; and A = 45. 133. Of the (dotted) shear curves, Fig 23, those of one set are tan- gential to the neut axis and reach top & bottom of beam at angles of 45, tending away from cen of span; while those of the other set are normal to these and to the neut axis at their intersections, reaching top and bottom of beam at 45, tending toward cen of span. MOMENTS IN CONTINUOUS BEAMS. See also 1ffl 78, etc. 134. Figs 25 and 26 show positive and negative bending moments in two continuous beams, Fig 25 of two equal spans, and Fig 26 of three equal spans, resting freely upon their supports. Each span = 1. Fig 26 (three spans) may be used, with sufficient approximation, for cases where the spans are more numerous. * Conversely for curves (concave downward) of normal compression. 494 A STRENGTH OF MATERIALS. -- - V. *j "i" - x ' J . ' ^ x tu 7 t ^ ,'/ Iv \j \^ (, 2 / 1 N \ t \ / | i ^7 n t (i 6 \ s K.1 0, / 1.5 J JP *(< rr \ / ,- -- .... \ I --1 *> A /' \ 1 5 I \ Fiff. 25. 0.10 i *''f -x 1 , ' 1'"" s^ I t \ x^ t o.W s '- r- x X ( \ \ / ta * ' / 0.03J '' \ \ t > . 3 ' \^J / / \ ^ 5 \ i. t - ' / 1 5 V 'v 3 () 1 a 5 3\ 1 ' -^ \ f s. 1 ~ 'A -- ^ \ / \ 1 t .- ^- ' IV -0 03- \ t,* It 1 ^ \ ^ / \ /> 5 /^ '\\ If ^ // 1 k ri-. 26. 135. At any cross section, the ordinate, betw the axis, X, of abscissas, and the curve, (1) m w , (2) m p pos, or (3) m neg, represents, respectively, by the scale of ordinates on the left, (1) the dead load moment, m w , (2) the max positive live-load mom, m p pos, or (3) the max negative live-load mom, m p neg, at that section, the dead load (1 per unit of span) being uniformly distributed over the entire length (two or three spans, as shown) of the beam, and the live load (1 per unit of span) being uniformly distributed alternately over two portions of the length of the beam, said portions being, for each cross section, such that the uniformly distributed live load, placed upon said portions, will produce, alternately, the max pos and the max neg mom at that section. 136. In an actual beam, at any point, we have, for bending mom: M = m w w U + m p p V ; where m w = the ordinate, at the point, from .Y to the curve m w ; m p = ". ' ' " " " " w = uniform dead load per unit of span; p = live " , placed as explained in If 135. L = the actual span. Thus, at the point, a, Fig 26 (distant 0.7 L from 0), we have, by scale, m w = 0.035; m p pos = 0.070; m p neg = 0.035. Hence, at point a, max pos mom = 0.035 w L 2 + 0.070 p L 2 ; max neg mom = 0.035 w L 2 0-035 p L 2 . If, therefore, p = w, the max neg mom, at a, is zero, and there is no resultant neg mom to the left of a; but, if p = 2 w, we have w = p/2 = (w + p)/3; and, at a, with p = 2 w : max neg mom = 0.035 w L 2 0.035 X 2 w L 2 = 0.035 w L2 0.070 w L 2 = 0.035 w L 2 = 0.035 (w + p) L2/3. 930 CEMENT MORTAR. MORTAR. Cement. For experiments, see p 1135. For specifications, see pp 937, 940, 942, 1184. For Concrete, see pages 1084, etc. For abbreviations, symbols and references, see p 947 1. 1. The property of setting and hardening under water is called hydrau- licity; and cements, which harden under water, are called hydraulic cements: or, more briefly, cements. For behavior of cement when mixed with water, with or without sand, see Mortar, p 947 d. Materials. 2. The elements, chiefly concerned in the action of lime and cem mortars, are Calcium, Ca ] Aluminum, Al Carbon, C \ Oxygen, O. Silicon, Si Hydrogen, H J 3. Oxygen combines with each of the others, forming oxides. Thus : Calcium oxide, CaO, is lime; Aluminum sesqui-oxide, Al 2 Os,* is alumina; Carbon dioxide, CC>2, is carbonic acid ; Silicon dioxide, SiO 2 , is silica, or silicic acidjf Hydrogen monoxide, H2O, is water. 4. The materials most used in the manufacture of cements are either (a) calcareous, (b) argillaceous, or (c) both calcareous and argillaceous. (a) Calcareous (rich in lime carbonates). Limestone, a lime carbonate, or combination of lime and carbonic acid, CaO + CO 2 , or CaCO 3 . Marble is limestone. Dolomite, or magiiesian limestone, containing about 45 per cent of magnesia carbonate, MgO. CO 2 . Where strata of limestone and dolomite adjoin, the rock varies in composition between the two, containing percent- ages of magnesia carbonate varying from to 45. Chalk, a soft limestone, composed of remains of marine shells. Marl, a soft and impure hydrated J lime carbonate, precipitated from still water and found in the beds and banks of extinct or existing lakes. Alkali waste, lime carbonate, precipitated, as a waste product, in the manufacture of caustic soda. Coral. See H 5. (b) Argillaceous (rich in alumina silicates). Clay (including argillaceous minerals in general), an alumina silicate, or combination of alumina and silicic acid, A1 2 O.3 + SiO 2 . Shale and slate, clay, solidified by geological processes. Puzzolana, or pozzuolana, a volcanic slag, found at Puzzuoli, or Poz- zuoli, near Mount Vesuvius, an impure alumina silicate. Blast furnace slag, practically an artificial puzzolana. Brick-dust. See r>. (c) Rich in both lime carbonate and alumina silicate. Cement rock is argillaceous (clayey) limestone. The alumina silicate usually ranges from 13 to 35 %. There is generally a considerable per- centage of magnesia carbonate, amounting sometimes to 25 %. 5. A soft coral rock, from the reefs near Colon, Panama, mixt with clay and silt brought down by the Chagres river, or with "a pumiceous rhyolite tuff," found on the Isthmus, or with both, and crushed, burned and tested at the Lehigh Valley Testing Laboratory, at Allentown, Pa., gave a *The subscripts indicate the combining ratios of the several elements. Thus, in alumina, A1 2 O 3 means a compound of 2 atoms of alumina with 3 of oxygen. t Quartz is silica; and most of the sand, used in mortar, is quartz sand. % Hydrated; containing chemically combined water. CEMENT. 931 uniform cement, comparing favorably with average standard brands of Lehigh cement. The coral rock is "a remarkably pure lime carbonate." The Chagres clay and silt are "rather low in silica, but contain a relatively large amount of iron as compared with alumina." The tuff "is of approx- imately the same composition as the argillaceous materials used in the Lehigh district of Pennsylvania. " (Ernest Howe, U. S. G S, E N, '07/Nov/ 21, p 544.) See HH 29, etc. 6. Mr. Ernest McCullough "mixed fine brick dust and hydrated lime together and made a fairly satisfactory cem for a small concrete job in a locality where Portland cem could not be obtained." (E N, '07 / Nov/21, p 557.) 7. Iiime. When limestone (without clay) is "burned," its CC>2 is driven off, and the remaining ("quick") lime has a strong affinity for water, absorbing it with such avidity as to develop heat sufficient to pro- duce steam, the generation of which disintegrates and swells the mass. Combining thus with the water, the lime forms calcium hydrate, CaO.H 2 O, or CaH 2 O 2 . This process is called slaking or slacking? ; and lime which has satisfied its affinity for water is called slaked (or slack) lime. When slaked lime is used as mortar, it gradually absorbs carbonic acid from the air, forming lime carbonate, the water being liberated and evaporated. Hardened lime mortar may thus be regarded as an artificial limestone. Manufacture. 8. Cement. When alumina silicate, such as clay, in sufficient quantities, is " burned " with calcium carbonate, such as limestone, the burned prod- uct, called cement, is deficient in, or devoid of, the slacking property; but, on the other hand, when it is made into mortar, the combinations, formed between the elements of the lime, the alumina, the silica and the water, during the burning, and afterward in the mortar, are such that they readily proceed under water. Chemists differ as to the nature of these combina- tions, except that these constitute a process of crystallization, resulting chiefly in the formation of hydrated lime silicate and hydrated lime alumi- nate, which two compounds constitute the major portion of most cems. Natural and Portland Cement. 9. In the manufacture of " natural " cement, cement rock, broken into lumps, is first calcined, at from 1000 to 1400 C (1800 to 2500 F) in a stationary kiln, in alternate layers with coal of about pea size, as fuel. It is then ground to a fine powder, and this is sometimes specially mixed, in order to increase its uniformity. 10. The qualities of nat cems vary widely, owing to diffs in the compositions of cem rocks found in diff localities. 11. The name Rosendale, originally and properly restricted to nat cems made in Ulster County, N Y, was at one time applied indiscriminately to American nat cems in general. 12. In Europe, quick-setting nat cems are called " Roman cements." 13. Portland cement was so called on account of the resemblance of the hardened mortar to Portland stone, the oolitic limestone of Portland, England. 14. Portland cem is made from different combinations of the cal- careous and argillaceous materials named in K 4, and these require different preliminary treatments. Thus, hard rock is crushed; soft rock and clay are ground; marl and clay are mixed wet, and the marl is sometimes pumped to the mill. In any case, the resulting materials are dried and finely ground, mixed, and then calcined at a temperature of 1450 to 1550 C, or say 2600 to 2800 F, producing incipient vitrifaction, which consists of the chemical combination of the silica, alumina and lime, into a glassy clinker, essentially a lirne silicate and aluminate. The resulting clinker is again ground to an impalpable powder, which is the finished product. 15. The proportions of the several materials are carefully adjusted. There is usually from 74 to 77.5 % lime carbonate, and about 20 % of alumina silicate and iron oxide. See H 32. 16. Manipulation. The raw material is sometimes molded into bricks which are burned in a stationary kiln; but it is now more generally fed, as a fine powder, into the upper end of a nearly hor cyl (rotary kiln) 6 to 8 ft 932 CEMENT MORTAR. in diam and from 60 to 100 ft or more in length. Coal dust, as fuel, is in- jected, by an air blast, into the other end; while most of the air, required for combustion, is admitted freely from the atmosphere thru other openings. 17. As in the case of lime, the burning- drives off the carbonic acid and water, and more completely oxidizes any iron present. 18. The higher cost of Portland cement is due to the more careful selection of the materials and to the more elaborate and expensive treatment given them, resulting in the ultimate attainment of much greater strength and uniformity than are usually found in nat cems. 19. The improvements, which have been made in the manufacture of Portland cement, are driving out other makes. Owing to its greater sand-carrying capacity, it is often used, by contractors, even where the specifications permit the use of nat cem. 20. Overburningr is liable to occur, if the material is deficient in lime ("over-clayed"). Underburning yields a soft brownish clinker, and weak, quick-setting cem, heating in water. Some cems, slow at first, be- come quicker after storage. 21. Portland Cement is used for structures subjected to severe or repeated stresses, for cases where high strgth must be attained in a short time, for concrete buildings, where water will be in contact with new work, for thin walls subject to water pres, and for work exposed to abrasion or to weather; while natural cement may be used in dry sheltered founda- tions under compressive loads not exceeding 75 Ibs per sq inch and not imposed until 3 months after placing, for backing and filling in massive cone or stone masonry where wt and mass are desiderata, and for street and sewer foundations. Pnzzolana. 22. Slag cements (sometimes called puzzolana cements or puz- xolana) are intimate mixtures of slaked lime and basic blast-furnace slag, both finely ground, and not calcined. As the slag leaves the blast-furnace, it is chilled and disintegrated by running it into water. A little soda is sometimes added, to hasten setting. Slag cem is not to be confounded with those Portland cems in which slag is one of the ingredients. 23. In dry air, the sulphides, contained in Puzzolana cement, oxi- dize, and cause superficial cracking. It sets more slowly than Portland, unless treated with soda. If so treated, the soda becomes carbonated under long storage, and the cem again becomes slow-setting. Since puzzo- lana cem, properly made, contains no free or anhydrous lime, it does not warp or swell, and requires less water than Portland; but, for permanency after placing, the finished work should be kept constantly moist. It is recom- mended for use in sea water, alone or mixed with Portland. Its mortar ia tougher than Portland, but never becomes so hard. It should not be subjected to attrition or blows. (Report, Board of U S Engr officers, U. S., Prof'l Papers No 28, '01.) 24. Puzzolana cement is said to work well if used with 2 or 3 parts sand and not subjected to freezing weather. Its ingredients must be finely ground and intimately mixed. It is used where extreme strength and hardness are not required. Silica Cement. 25. Silica Cement, or sand cement, was originally made by mixing Portland cem with quartz sand (silica) and grinding the mixture to extreme fineness It was claimed that the cem thus became much more finely ground, and that "silica cement," containing one part Portland cem and three parts silica, could therefore carry, in mortar, nearly as much sand as could the pure cem alone; also that mortars, made with silica cem, were less permeable to water than those made with pure cem in the ordinary way. 26. Owing to the high cost of grinding the quartz sand, less refractory materials, such as lime-stone, are now substituted for it. The product, so obtained, is still called "silica cement," altho containing a less propor- tion of'silica than Portland cem. 27. Silica cement mortar is said to work more smoothly under the trowel than that made with ordinary cems. 28. In the construction of a concrete lock at St. Paul, Minn., it was in- tended to use 1.5 volumes silica cem as equivalent to 1 vol Saylor's Port- CEMENT. 933 land; but experiments indicated that, at 6 mos, concrete, made with silica cem, was as strong as that made with Portland. Other Cements. 29. White Portland cement, obtained by making certain modifi- cations in the process of manufacture, is nearly colorless. It is suitable for making imitation marbles, etc., and capable of taking artificial coloring. It is higher in price than ordinary Portlands. See If 44. SO. Iron ore cement ("Erz-cement"), Krupp Steel Co. In this cem, the argillaceous material of Portland cem is mostly replaced by iron oxide. The material is burned and ground as for Portland cem, HU 13, &c. Spec grav, 3.31. Slower setting than Portland. Sound. Low early strgths; but, in time, strgth far exceeds that of Portland. No trace of expansion or crackg in sea water under 15 atmospheres. (Wm. Michaelis, Jr., Western Soc Engrs, Aug 1907; S. B. Newberry, Cement Age, Jan 1907.) 31. Hydraulic lime is a name given to cems (much used in Europe) which, while to some extent hydraulic, do not contain enough of the hydrau- lic elements to prevent slaking. The slaking, however, is slower, and the swelling less, than with lime proper. Composition. 32. Analyses of cements, in percentages. In each group of three lines, the upper line shows the max percentage. " middle " " mean " lower " " " min " Silica. Alumina. Iron Oxide. SiO z Xiwe. Ca O 10 20 30 10 10 20 10 20 30 40 50 Magnesia. MgO 10 20 Fig 1. Analyses of Cements. 33. The ratio of the wt of alumina silicate to that of the lime, in a cem, is called its hydraulic index. Other things being equal, it may be used as an indication of the hydraulicity of the cem. 34. Thus, if a cem contains 30 % alumina silicate and 60 % lime, its hy- draulic index is 30/60 = 0.50. 35. The hydraulic modulus is approximately the reciprocal of the hydraulic index; i.e., the modulus is the ratio, by wt, of lime, to silica, * Richard K. Meade, " Portland Cement," 1906, pp 16-17. t E. C. Eckel, "Cements, Limes and Plasters," 1907, pp 253 etc., 667-8. 1 16 analyses of "Steel" (slag) cement, made by Illinois Steel Co., Soufch Chicago, reported by Board of U. S. Engr Officers, 1900, gave practically the same avs, but with generally greater uniformity: silica, 29.9 to 27.8; alumina and iron, 12.1 to 11.1; lime, 52.1 to 50.3; magnesia, 3.0 to 1.6. C3 934 CEMENT MORTAR. alumina and iron oxide. It is sometimes specified that the modulus, in Portland cement, shall be 1.7. 36. In natural cements, the modulus usually ranges from 0.667 to 1.667. 37. Mr. Spencer B. Newberry uses the ratio : (lime alumina) -r- silica, which he terms the lime factor, and which usually varies, iu the raw material, betw 2.7 and 2.8, and, in the best commercial cems, betw 2.5 and 2.6. 38. Mr. Edwin C. Eckel (Cements, Limes and Plasters, p 170) suggests the Cementation index - 2 ' 8 * + l ' 1 * + ' 7i I + 1.4m where s, a, i, I and m are the percentages, by wt, of silica, alumina, iron oxide, lime and magnesia, respectively. 39. The most common adulterants of cem are ground limestone, lime, shale, slag and ashes; and Portland cem is sometimes adulterated with nat cem. Most of the adulterants commonly used are merely inert, and there- fore only weaken the cem; but quick lime may do more serious mischief. See Cement Mortar, Iffl 28, etc., p 947 /. Properties. Fineness. 40. Fineness. Even in cem of standard fineness, the inner portions of the grains seem to remain inert. The finer the cem, the more sand it will carry and still produce a mortar of a given strength; but, in each case, there is a point where the cost of additional fineness offsets the additional advantage which may be gained. 41. Hence fineness is less important with natural than with Port- land cem; for the cheapness of nat cem may render it advisable to use the cem in larger quantities, rather than pay for finer grinding, in order to secure the desired strgth. 42. Cements, ground to extreme fineness, in order to secure strgths beyond those of commercial products, set so quickly that they must be used immediately after adding water. (VVm. Michaelis, Jr., Western Soc of Engrs, Aug '07.) 43. The fineness of cement and sand is indicated as fol- lows, where the large numerals represent the sieve numbers; the small numeral, to the left of each sieve number, represents the percentage retained upon that sieve; and the final small numeral, to the right of the last sieve number, represents the percentage passed by the last sieve. The sum of the small numerals = 100. Thus, 5 20 15 30 35 40 45 means that 5 % were re- tained on a No. 20 sieve, 15 % on a No. 30, and 35 % on a No. 40, while the remaining 45 % passed the No. 40 sieve. Color. 44. Color. The lime silicates and aluminates, which constitute the cem proper, are colorless when pure. (See White Cement, If 29.) The color of cems is therefore due to other matter which is unavoidably present, notably to the iron oxides, and may be affected by either beneficial, harmful or neutral ingredients. Hence, color, in itself, is of but little value as a guide to quality, but variations in shade, in a given kind of cem, may indicate diffs in the character of the rock or in the degree of burning. Thus, with nat cems, a light color generally indicates an inferior or under- burned rock. A coarse-ground cem, light in color and wt, would be viewed with suspicion. 45. "With Portland cem, gray or greenish-gray is generally considered best; bluish gray indicates a probable excess of lime, and brown an excess of clay. Natural cems are usually brown, but vary from very light to very dark. Slag cem has a mauve tint a delicate lilac." (Prof Ira O. Baker, "A Treatise on Masonry Construction," p 55.) Weight. 46. Specific (gravity and weight. See spec grav, pp. 940, 942. The sp gr of the solid particles of cem is not affected by fineness of grinding, CEMENT. 935 but is diminished by absorption of water and carbonic acid under exposure, and is therefore increased by drying. The sp gr of Portland cems may range from 2.9 to 3.25, ordinarily from 3 to 3.2; nat cems, 2.7 to 3.2; Puz- zolano cem, from 2.7 to 2.9. 47. The weight, per cu ft, of cem powder, is affected by exposure and by drying, as explained above, and is increased by compression, as in pack- ing. It is reduced by fine grinding, the finer particles packing less closely. Faija found a loss, in wt, of about 6 % in a few days after grinding; 17 % in 6 mos, and 21 % in a year. 48. In a German Portland cem, Eliot C. Clarke found 90 Ibs per cu ft when 40 % was retained on No. 120 sieve, and 75 Ibs per cu ft when so finely ground that all passed the same sieve. 49. As a rude approximation, Portland cem is taken as weighing 100 Ibs, nat cem 75 Ibs, per cu ft. Packages. 50. Owing to variations in the specific gravity of cems, there is corre- sponding variation in sizes and weights of packages and their contents. The trade practice is to sell a bbl of Portland cem as 400 Ibs gross (including wt of bbl); nat, 300 Ibs gross. 51. A Portland Cement barrel is 2 to 2.2 ft high, betw heads, 1.38 to 1.46 ft av diam. It weighs 21 to 29 Ibs, and is lined with paper for ordinary transportation. Its capacity is 3.1 to 3.5 cu ft, but the cem, com- pressed into it, in packing, occupies 3.75 to 4.3 cu ft loose, and weighs 370 to 390 Ibs. The bbl is not returnable. 52. A natural cement barrel weighs about 20 Ibs. In the Wes- tern states it contains 265 Ibs; in the Eastern states, 300 Ibs, of cem. 53. " Domestic "" barrels are used for shipment to all points in the U. S., with slight reinforcement for Gulf ports; "standard export" bbls for Mexico and the West Indies; "'special export barrels" where specially severe treatment is expected. 54. The standard export barrel is of better stock than the "domestic," and is reinforced with cross pieces in the heads and with two iron hoops. It costs from 5 to 10 cts more than the "domestic" bbl, vary- ing with cost of cooperage stock. 55. The special export barrel costs 10 to 15 cts more than the standard export bbl. It is all-hardwood, heavily hooped and reinforced, with wood cross-pieces in the heads, iron hoops, and clamps to hold the heads in place. A heavy waterproof lining is used instead of the heavy Manila paper used with the standard export bbl. 56. Most cem is now packed in "cloth" or paper bags, except for ship- ment by sea. 57. Cement bag's are made of cloth (canvas or cotton duck) and of "rope Manila" paper. When empty, they measure about 17 X 28 ins. (See Digest of specification of the Am Soc for Testing Materials.) A "cloth" bag is usually charged to the purchaser at about 10 cts, and credited at about 7.5 cts when returned. I'aper bags are charged at 2.5 cts each and are not returnable. 58. The use of paper bags obviates loss of time in emptying and re- turning bags, shortage on lost or damaged bags, and loss of cem in transit or by failure to empty bags completely; but paper bags are more likely to lose their entire contents by breakage, and pieces of broken bags may get into the work and weaken it. 59. p\>r large work, cem has frequently been shipped in cars in built . with little loss or damage, provided the cars are carefully selected. This method is especially advantageous where the cem is tested at the mill, stored in "accepted bins," and shipped direct to the work, in sealed cars. The cars may be unloaded by automatic conveyors. Bags and bbls are often preferred as furnishing a convenient means for keeping account of the quantities of cem entering the work; but, in large operations, there should be no difficulty in arranging to keep such accounts with bulk shipments. Age. O. "Aging" consists in the slaking pf the free lime remaining in the cem after burning. Good Portland cem is improved by a few weeks of 936 CEMENT MORTAR. aging in dry air; and, if kept dry. it deteriorates but slowly under even long storage; but nat cems usually suffer by aeration; and cems in general, being composed of compounds with a strong affinity for water, deteriorate if exposed to dampness. Hence, protection from moisture, even that of the air, is very essential for the preservation of cems, as well as of quick- lime. With this precaution, the cern, altho it may require more time to set, than when fresher, does not otherwise very appreciably deteriorate in many months. 61. Storage, under pressure, tends to the caking of cems, which, there- fore, does not necessarily indicate deterioration. 62. Restoration by reburning. Cems which have deteriorated by exposure, may be in great measure restored by reheating to redness. 63. If cem is stored in warm places, it is apt to "flash" when mixed with water, i. e., to set much more rapidly than it should. Testing. See Digests of Specifications, A S C E, p 942 ; Engng Standards Comm of Gt Brit, p 940; Report of Board of U S Engr Officers, p 937. 64. Thorq chemical tests of cem can of course be made only by expert chemists; but the following simple test may be made by the engi- neer. Treated with hydrochloric acid, "pure Port cem effervesces slightly, gives off some pungent gas, and gradually forms a bright yellow jelly, with- out sediment. Powdered limestone or cem rock, mixed with the cem, causes violent effervescence, the acid giving off strong fumes until all the lime carbonate is decomposed, when the yellow jelly forms. Quartz sand remains undissolved. Reject cem containing these adulterants." Judson, "City Roads and Pavements." The presence of slag is generally indicated by the sulfur present, which causes a milky appearance, if the cem be agi- tated in a solution of hydrochloric acid in water. 65. Fuller and Thompson found that cems, which failed to stand this test, failed also to set properly; while cems which passed it, also passed more elaborate chemical tests. (Trans A S C E, Vol 59, '07, Dec, pp 73-4.) CEMENT. 937 Properties and Tests of Cement. Report of Board U. S. A. Kngineer Officers. Properties and tests of Portland, Natural and Puz- zolan* cements. Digest of a Report of Majors W. L. Marshall and Smith S. Leach and Capt. Spencer Cosby, Board of Engineer Officers, on testing Hydraulic Cements. Professional Papers, No. 28, Corps of Engineers, U. S. A., 1901. Unfortunately, tests for acceptance or rejection must be made on a product which has not reached its final stage. A cement, when incorporated in masonry, undergoes chemical changes for months, whereas it is seldom possible to continue tests for more than a few weeks at the most. A few tests, carefully made, are more valuable than many, made with less care. Cement which has been in storage for a long time should be carefully tested before use, in order to detect deterioration. A cement should be rejected, without regard to the proportion of failures among samples tested, if the samples show dangerous variation in quality or lack of care in manufacture, and resulting lack of uniformity in the product. The practice of offering a bonus for cement showing an abnormal strength is objectionable, as it leads to the production of cements with defects not easily detected. For Portland or Puzzolan cement, make tests for (1) fineness of grinding ; (2) specific gravity ; (3) soundness, or constancy of volume in setting; (4) time of setting, and (5) tensile strength. For Natural cement* omit tests (2) and (3). (1) Fineness. Ceinentitious quality resides principally, if not wholly, in the very finely ground particles. Use a No. 100 sieve, woven from brass wire No. 40 Stubs gage; sift until cement ceases to pass through. The percentage that has passed through is determined by weighing the residue on the sieve. The screen should be frequently examined to see that no wires have been 'displaced. (2) Specific gravity. The specific gravity test is of value in determining whether a Portland cement is unadulterated. The higher the burning, short of vitrification, the better the cement and the higher the specific gravity. If under- burned, the specific gravity of Portland cement may fall below 3 ; if overturned, it may reach 3.5. Natural cement has a specific gravity of about 2.5 to 2.8, and Puzzolan about 2.7 to 2.8. The temperature may vary between 60 and 80 F. Any approved form of volumenometer or specific gravity bottle may be used, graduated to cubic centi- meters with decimal subdivisions. Fill the instrument to zero of scale with benzine. Take 100 grams of sifted cement that has been previously dried by exposure on a metal plate for 20 minutes to a dry heat of 212 F., and allow it to pass slowly into the benzine, taking care that the powder does not stick to the sides of the graduated tube above the fluid, and that the funnel, through which it is introduced, does not touch the fluid. The approximate specific gravity will be represented by 100 divided by the displacement in cubic centimeters. The operation requires care. (3) Soundness, and (4) setting qualities. The temperature should not vary more than 10 from 62 F. For Portland cement use 20, for Natural 30, and for Puzzolan 18 per cent, of water by weight. Mix thoroughly for 5 minutes. On glass plates make two cakes about 3 inches in diameter, % inch thick at the middle and drawn to thin edges, and cover them with a damp cloth. At the end of the minimum time specified for initial set, apply needle J^- inch diameter, weighted to \ pound. If an indentation is made, the cement passes the require- ment for initial setting. Otherwise the setting is too rapid. At the end of the maximum time specified for final set, apply the needle ^V inch diameter, loaded to one pound. If no indentation is made, the cement passes the requirement for final set. Otherwise the setting is too slow. Generally speaking, both periods of set are lengthened by increase of moisture, and shortened by increase of temperature. *By Portland cement, in this report, is meant the product obtained by calcining intimate mixtures, either natural or artificial, of argillaceous and calcareous substances, up to incipient fusion. By Natural cement is meant one made by calcining natural rock at a heat below incipient fusion, and grind- ing the product to powder. By Puzzolan is meant the product obtained by grinding slag and slaked lime, without subsequent calcination. 62 938 CEMENT MOETAR. Recommendations of Board of II. S. A. Engineer Officers. Continued. In gaging Portland cement in damp weather, thesamples should be thoroughly dried before adding water. This precaution is not deemed necessary with Natural cement. Sufficient uniformity of temperature will result if the testing room be comfortably warmed in winter, and if the specimens be kept out of the Bun in a cool room in summer, and under a damp cloth until set. Temperatures may vary between 60 and 80 F., without affecting results more than the probable error in the observation. Boiling test. Place the two cakes under a damp cloth for 24 hours. Place one of them, still attached to its plate, in water 28 days; immerse the other in water at about 70 F., and let it be in a rack above the bottom of the receptacle; heat the water gradually to the boiling point, maintain the heat for 6 hours and then let cool. The boiled cake should not warp or become detached from the plate, or show expansion cracks. If the cold-water cake shows evidences only of swelling, the cement may be used in ordinary work in air or fresh water for lean mixtures, but if distortion or expansion cracks appear in it, the cement should be rejected. Accelerated tests are not generally recommended, but where a test mugt be made in a short time, the boiling test is considered about the best. It not only gives short-time indications, but at once directs attention to the presence of ingredients which might lead to disintegration. On the other hand, it may lead to the rejection of a cement which would behave satisfactorily in actual work alid which would stand the test after air-slaking. Sulphate of lime, while enabling cements to pass the boiling tests, introduces an element of danger. (5) Tensile tests are preferred to flexural or compressive tests. Sand tests are the more important and should always be made; and neat tests should be made if time permits. A cement which tests moderately high at 7 days, and shows a substantial increase in strength in 28 days, is more likely to reach the maximum strength slowly and retain it indefinitely with a low modulus of elasticity, than a cement which tests abnormally high at 7 days with little or no increase at. 28 days. Use briquettes of the form recommended by the American Society of Civil Engineers,* measuring 1 inch square in cross-section at place of rupture, and held by close-fitting metal clips, without rubber or other yielding contacts. The tests should be made immediately after taking the briquettes from the water. Neat tensile tests. Use unsifted cements. For Portland cement, use 20; for Natural, 30; and for Puzzolan, 18 per cent, water by weight. Place the cement on a smooth non-absorbent slab ; in the middle make a crater sufficient, to hold the water; add nearly all the water at once, the remainder as needed ; mix thoroughly by turning with the trowel, and vigorously rub or work the cement for 5 minutes. Place the briquette mold on a glass or slate slab. Fill the mold with consecu- tive layers of cement, each to be % inch thick when rammed. Give each layer 30 taps with a soft brass or copper rammer weighing 1 pound, having a face % inch diameter or 0.7 inch square, and falling about % inch. After filling the mold and ramming the last layer, strike smooth with a trowel, tap mold lightly or^side, to free cement from plate, remove the plate, and leave for 24 hours, covered with a damp cloth. Then remove the briquette from the mold and immerse it in freshwater, which should be renewed either continu- ously or twice in each week during the specified time. Tensile tests with sand. For Portland and Puzzolan cements, use \ part cement to 3 parts sand ; for Natural or Rosendale, 1 to 1. Use crushed quartz sand, passing a No. 20 standard sieve, and being retained on a No. 30 standard sieve. After weighing carefully, mix dry the cement and sand until the mixture is uniform, add the water as in neat mixtures, and mix for 5 minutes. The con- stituents should be well rubbed together. For maximum strength in tested briquettes, Portland cements require water = 11 to 12% per cent, by weight of constituent sand and cement ; Natural, 15 to 17 ; and Puzzolan, 9 to 10. A machine which applies the stress automatically and at a uniform rate * See page 944. CEMENT. 939 Recommendations of Board of U. Is. A. Engineer Officers. Continued. of increase is preferable to one controlled entirely by hand. The stress should be increased at the rate of about 400 fos. per minute. A rate materially greater or less than this will give different results. The highest tensile strength from each set of briquettes made at any one time is to be considered the governing test. Field tests are recommended, whether or not the more elaborate tests above described have been made. In connection with tests of weight and fine- ness, and observations of texture and hardness in the work, field tests often suffice for well-known brands, showing whether the cement is genuine and whether it is reasonably sound and active. Pats and balls of neat cement from the storehouse, and of mortar from the mixing platform or machine, should be frequently made. Estimate roughly the setting and hardening qualities by pressure of the thumb-nail ; hardness of set and strength by breaking with the hand and by dropping upon a hard surface. The boiling test may also be used. Should the simple tests give unsatisfactory or suspicious results, then a full series of tests should be carefully made. A cement may be rejected if it fails to meet any of the following requirements Requirements. Portland. Natural. Puzzolan. Slow. Quick. Fineness. Percentage to pass through a No. 100 sieve as in (1) 87 to 92* 80 97 Specific gravity. Between 3.10 3.10 Not 2.7 and 3.25 3.25 given 2.8 Time of setting. Initial, not less than 45m. 20m. 20m. 45m. nor more than 30 m Final, not less than 45m nor more than 10 h. 2.5 h. 4 h. 10 h. Tensile strength, neat, - / 7 days f 450 400 90 350 fts. per sq. in. -j 2g da - y ^ 54Q m m 500 Tensile strength. With sand, as in (5). fcsnprsnii i 7 days f 140 120 60 140 1 28 days f 220 180 150 220 *92 per cent, is quite commonly attained by high-grade American Portlands, but rarely by imported brands. For the latter, use 87. f Reject any cement not showing an increase at 28 days over 7 days. 940 CEMENT MORTAR. DIGESTS OF SPECIFICATIONS. Requirements. American Society for Testing Materials. Digest of Specification adopted by the Society, Nov 14, 1904. See Amendments of 1908.* Adopted by Assn of Am Portland Cement Mfrs, June 10, 1904,* and by Am Ry Eng fc .Mainl of Way Assn, Mar 21, 1905.* 1. Packages. Brand and mfr's name plainly marked thereon. Bag to contain 94 Ibs net. Bbl Portland = 4 bags; nat, 3 bags. 2. Tests in accordance with recommendations of Comm of A S C E, p 942. "Gem, failing to meet the 7-day requirements, may be held awaiting the results of the 28-day tests before rejection." 3. Qualities. Natural Portland Sp gr, cem thoroly dried at 100 C.* min 2.8 * min 3.1 Loss of wt, on ignition ... * Fineness. Percentage, by wt: Residue on No. 100 sieve max 10 max 8 on No. 200 sieve max 30 max 25 Time of setting, mins, initial min 10 min 30 hard min 30 / min 60 L max 180 \ max 600 Tensile strgth, Min requirements,* Ibs per sq inch; briquettes 1 inch square section. Briquettes must show no retrogression in strgth during specified periods. 1 day in moist air in all cases. Neat Natural Portland 24 hours 50 to 100 150 to 200 7 days 100 to 200 450 to 550 28 days 200 to 300 550 to 650 1 part cem, 3 parts standard sand. 7 days 25 to 75 150 to 200 28 days 75 to 150 200 to 300 Soundness (constancy of volume) (For normal and accelerated tests, see digest of A S C E Specfns, p 945) to stand to stand normal test. normal and accelerated tests. Anhydrous sulfuric acid max 1 .75% Magnesia max 4.00% Engineering Standards Committee of Great Britain, Adopted Nov. 23, 1904. 1. Consignments of from 100 to 250 tons to have expert testing and chemical analysis. For consignments of less than 100 tons, makers shall, if required, give certificate, for each delivery, that cem meets this spec'n. 2. Samples. Test samples to be taken as soon as bulked at factory or on the work, at consumer's option. Samples to be taken from each "parcel," each sample consisting of cem from at least 12 diff positions in same "heap," mixed together and spread out, 3 ins deep, for 24 hours, at a temp between 58 and 64 F. * Amendments adopted by Am Soc for Testing Materials, Sep 1908: Strength. The means of the values given shall be taken as the required minima where these are not specified. Natural Cement. Omit specification for specific gravity. Portland Cement. Specific gravity. For "thoroly dried at 100 C," read "ignited at a low red heat." Loss of weight, on ignition, > 4 %. TESTS. 941 Requirements. Engineering Standards Committee of Crreat Britain. Continued. 3. Fineness. Meshes Wire Residue not per lin inch per sq inch diam, ina to exceed 76 5,776 0.0044 5.0% 180 32,400 0.0018 22.5% Wire woven, not twilled. 4. Tensile strength. Test room temperature, 58 Q to 64 F. Water, fresh, renewed every 7 days. Temp 58 to 64 F. Paste, smooth, easily worked, that will leave the trowel cleanly in a com- pact mass. Briquette, filled, not rammed, into mold resting upon an iron plate, and left until cem has set. Briquette kept in damp atmosphere 24 hours; then in water until broken. Clips. See Fig. 1. = 0.40 inch; = 0.60 " = 1.00 " = thickness; = 1.75 inch; = 2.00 " Fig 1. Briquet and Clips. British Standard. Load, start at zero. Add 100 Ihs each 12 seconds. Neat test. 6 briquettes at 7 days, and 6 at 28 days. Av of the six ac- cepted as the tensile strgth of the cement. 7 days, < 400 Ibs per sq. inch- 28 days, < 500. When 7 day test is betw Increase, from 7 to 28 days, must be not less than 400 and 450 IDS per sq. in ..................... 25 per cent. 450 and 500 " " " " .................... 20 500 and 550 " " " " .................... 15 550 and over " " " " .................... 10 " Test with sand. By wt, 1 cem, 3 standard sand from Leighton Buzzard, thoroly washed and dried. Sand must pass No. 20 sieve of 0.0164 inch wire, and remain on No. 30 sieve of 0.0108 inch wire. Mixture thoroly wetted, but without superfluous water. 7 days, 120 Ibs per sq inch; 28 days, 225. Increase, from 7 to 28 days, not less than 20 %. 942 CEMENT MORTAR. Requirements. Engineering Standards Committee of Great Britain. Continued. 1 Sot I in- Time ' mins - o. < ing 1 . maximum minimum Quick 30 10 Medium 120 30 Slow 300 120 "Set" has occurred when needle, loaded with 2% Ibs, with flat end Vio inch square, fails to make an impression. 6. Soundness. LeChatelier test. Expansion not to exceed 12 mm after 24 hours aeration; 6 mm after 7 days. 7. Specific gravity. Not less than 3.15, when sampled and hermeti- cally sealed at makers'. Not less than 3.10, when sampled after delivery to consumer. 8. Analysis. Water, > 2 %, whether added or naturally absorbed from the air. Calcium sulfate, > 2 % of wt of cem, calculated as anhydrous calcium sulfate. Lime, > enough to saturate the silica and alumina. Insoluble residue, > 1.5 %. Magnesia, > 3 %. Sulfuric an- hydride, > 2.5 % Tests. American Society of Civil Engineers. Digest of report of Committee on Uniform Tests of Cement,* Jan '03. as amended Jan '04 and Jan '08. 1. Selection of samples left to discretion of engineer. Number of samples and quantity to be taken from each package depend upon impor- tance of work, upon number of tests to be made and upon facilities for making them. Where conditions permit, sample one bbl in ten. Individual samples may be mixed, and av tested; but, where time permits, test sepa- rately. 2. Barreled cement to be sampled through a hole made in the center of a stave, midway between the heads, or in the head. Bagged cement to be sampled from surface to center. 3. Samples to be coarsely screened thru a No. 20 sieve. 4. Chemical analysis may show adulteration in the case of cems rich in inert material, but is not conclusive evidence of quality. Committee recommends method proposed by Committee on Uniformity &c., New York Section of the Society for Chemical Industry, see E N, '03, Jul 16, p 60; ER, '03, Julll,p49. 5. Specific gravity test. Le Chatelier's method recommended. Fig 1. Flask, D, 120 cubic centimeters (cc); neck about 9 mm diam and 20 cm long, with bulb, C; vol, betw marks, F and E, 20 cc. Neck graduated, to 0.1 cc, above F. Neck of funnel, B, enters neck of flask, and extends to top of bulb, C. Use benzine (62 Baume naphtha) or kerosene free from water. During the operation, in order to avoid variations in the temperature of this liquid, the flask is kept immersed in water, in a jar. Two methods, viz-. (a) Flask filled to lower mark, E. Weigh out 64 grams (2.25 oz) of the cem powder, cooled to temp of liquid. Thru the funnel, B, introduce the cem powder gradually until surf of liquid reaches the upper mark, F. Then 64 grams, minus wt of powder remaining unused, = wt, w, which has dis- placed 20 cc and Specific gravity = w / 20. (b) Fill, with liquid, to lower mark, E, as before. Add the entire 64 grams cem powder, liquid rising to some division of the graduated neck. *Geo. S Webster, Richard L. Humphrey. Geo. F. Swain. Alfred Noble, Louis C. Sabin, Spencer B. Newberry, Clifford Richardson, F. H. Lewis, W. B. W. Howe. A S C E, Proceedings, Jan '03, Feb '04, Feb '0* TESTS. 943 Tests. Am Soc Civ Eng-rs. Continued. The reading of this division, plus 20 cc, is the vol, v, displaced by 64 grams of the powder; and Specific gravity = 64 /v. 6. Fineness. Sieves should be circular about 20 cm (7.87 ins) diam, 6 cm (2.36 ins) high, with pan 5 cm (1.97 ins) deep, and a cover. Sieves should be of wire cloth, No. 100, 96 to 100 meshes per lineal inch; wire 0.0045 inch diam. No. 200, 188 to 200 " " " " " 0.0024 " Use 50 grams (1.76 oz) or 100 grams, cem; dried at 100 C (212 F). Hand sieving preferred. Use No. 200 sieve until one minute continuous sieving, at about 200 strokes per minute, passes not more than 0.1 %. Weigh residue, and treat it similarly on No. 100 sieve. A small quantity of large steel shot, placed in the sieve, expedites the work. The results should be reported to the nearest 0.1 %. Fig 1. Sp grav Flask. Fig 2. Vicat Needle Apparatus. 7. Xormal consistency. The percentage of water, used in making the pastes, for tests of strgth, soundness and setting, vitally affects the results. Normal consistency is determined as follows : The quantity of cem, to be subsequently used for each batch in making the briquettes, but not less than 500 grams, is kneaded into a paste as under "Mixing," ^ 12, quickly formed into a ball, with the hands, and tossed six times from hand to hand, held 6 ins apart. The ball is then pressed thru the larger opening of the Vicat needle apparatus into the gum ring, I, 7 cm (2.76 ins) diam, 4 cm (1.57 ins) deep, smoothed off below, and placed on the glass plate, J. Its upper surf is then smoothed off with a trowel. The point of the Vicat needle, H, is then brought into contact with the upper surf of the sample, and the cyl, L, is allowed to descend. The paste is of the normal con- sistency when the needle penetrates to a depth of 1 cm (0.39 in). With this rather wet paste, the committee believes that variations, in the amount of compression to which the briquette is subjected in molding, are likely to be less than with a drier paste. H. Setting. Vicat needle, H, Fig 2, 1 mm (0.039 in) diam, loaded to 300 grams (10.58 oz). Setting has begun when needle ceases to pass a point 5 mm (0.20 in) above the upper surface of the glass plate; and has terminated when the needle does not visibly penetrate the mass. Test pieces kept damp, during test, by storage in a moist box or closet, or placed on a rack over water in a pan and covered by a damp cloth, the cloth resting upon a wire screen, so as not to touch the test pieces. Keep needle clean; as cem, adhering, seriously 944 CEMENT MORTAR. Tests. Am Soc Civ Engrs. Continued. vitiates results. Time of setting is materially affected by temp of mixing water, by temp and humidity of air, by the percentage of water used, and by the amount of molding paste receives. 9. Standard sand. Crushed quartz objectionable, "especially on ac- count of its high percentage of voids, the difficulty of compacting in the molds, and its lack of uniformity." Comm recommends natural sand from Ottawa, 111. Sand to pass a No. 20 sieve, with wire diam = half the diam of spaces betw wires; < 99 % to be retained on a similar No. 30 sieve after 1 minute of continuous sifting of a 500 gram sample. The Sandusky Portland Cement Co., Sandusky, O., has agreed to furnish such a sand at actual cost of preparation. 1O. Standard briquette. See Fig. 3. Am Soc Civ Engrs. Dotted lines are those recommended by earlier Comm. Trans, Vol 14, Nov. 1885. W = 1.25 ins. c = 0.25 " = contact with briquet. Fig 3. Briquet. Fig 5. Clip. Fig 4. ing Mold. Gang 11. Molds, "of brass, bronze or some equally non-corrodible material;" sides strong enough to resist spreading. Gang mold, Fig 4, recommended, because the greater quantity of mortar, required for it, conduces to uniform- ity of results. Molds to be "wiped with an oily cloth before using." 12. Mixing. Proportions stated by wt; quantity of water stated as percentage of dry material. Metric system recommended. Temp of room and mixing water as near 21 C (70 F) as practicable. Sand and cem thoroly mixed dry. Mixing done on some non-absorbing surf, preferably plate glass. If an absorbing surf is used, it should first be thoroly dampened. Quantity of material, mixed at one time, depends on number of test pieces to be made; about 1000 grams (35.28 oz.) convenient to mix, espe- cially by hand methods. Hand mixing and hand molding recommended. Material weighed, and placed on mixing table, and a crater formed in the center, into which the proper percentage of clean water is poured; material on outer edge turned into crater by aid of a trowel. As soon as the water is absorbed, the opera- tion is completed by vigorously kneading with the hands for an additional 1 ^ minutes. A sand-glass affords a convenient guide for the time of knead- ing. The hands should be protected by gloves, preferably of rubber. Molds filled immediately after the mixing is completed, material pressed in firmly with the fingers and smoothed off with a trowel, without mechani- cal ramming; material heaped up on the upper surface of the mold. In smoothing off, the trowel should be drawn over the mold, exerting a mod- erate pressure on the excess material. Mold turned over and operation repeated. TESTS. 945 Tests. Am Soc Civ Engrs. Continued. Weigh the briquettes "just prior to immersion, or upon removal from the moist closet," and reject those varying > 3 % from the av. 13. Moist Closet. "A moist closet consists of a soapstone or slate box, or a metal-lined wooden box the metal lining being covered with felt and this felt kept wet. The bottom of the box is so constructed as to hold water, and the sides are provided with cleats for holding glass shelves on which to place the briquettes. Care should be taken to keep the air in the closet uniformly moist." "Where a moist closet is not available, a cloth may be used and kept uniformly wet by immersing the ends in water. The cloth should be kept from direct contact with the test pieces by means of a wire screen or some similar arrangement." 14. Immersion. "After 24 hours in moist air the test pieces for longer periods of time should be immersed in water maintained as near 21 C (70 F) as practicable; they may be stored in tanks or pans, which should be of non-corrodible material." 15. Tensile strength. Solid metal clip, Fig. 5, recommended. No cushioning between clip and briquette. Briquettes broken immediately after removal from water. Center the briquette carefully in the clip, to avoid transverse stresses. Load applied at rate of 600 Ibs per min. "The average of the briquettes, of each sample tested, should be taken as the test" of that sample, "excluding any results which are manifestly faulty." 16. Soundness (Constancy of Volume). "In the present state of our knowledge it cannot be said that cement should necessarily be con- demned simply for failure to pass the accelerated tests (be'ow); nor can a cem be considered entirely satisfactory, simply because it has passed these tests." Pats of cem paste of normal consistcy (^j 7), abt 7.5 cm (2.95 ins) diam, 1 .25 cm (0.49 in) thick at center, tapering to thin edge, made on a clean glass plate about 10 cm (3.94 ins) square, 24 hours in moist air before test. (1) Normal test. One pat immersed in water maintained as near 21 C (70 F) as possible; one in air at ordinary temp. Both observed at intervals for 28 days. (2) Accelerated test. A pat is exposed in any convenient way in an atmosphere of steam, above boiling water, in a loosely closed vessel, for 5 hours. Pats must remain firm and hard, and show no signs of cracking, distortion or disintegration. Warping may be conveniently detected by applying a straight edge to the surf which was in contact with the plate. 946 CEMENT MORTAR. Sand.* Composition. 1. The sand,* used in mortar, is ordinarily made up chiefly of grains of quartz (silica), with some impurities, mostly grains of silicious minerals. In testing cements in the laboratory, crushed quartz or some standard natural sand is used. (See Spec'ns A S C E, under Cement, p. 942.) 2. The silica of the quartz, in sand, undergoes no chemical change in the mortar; but the use of sand, by diminishing the quantity of cem reqd, reduces also the cost of the finished work. See remarks on strength, under Mortar, p 947 t. SIZES OF GRAIXS. 3. Screening. Sand and gravel are screened, usually in an inclined fixed screen, upon which the material is placed by a conveyor, or shoveled by hand; or in an inclined revolving cylindrical or hexagonal screen, into which the material is fed. 4. Method of quartering. "To obtain an average sample from a pile of sand, gravel or stone, the method of quartering is useful. Shovel- fuls of the material are taken from various parts of the pile, mixed together and spread in a circle. The circle is quartered, as one would quarter a pie, one Of the quarters is shoveled away from the rest, thoroughly mixed, spread, and quartered as before. The operation is repeated until the quan- tity is reduced to that required for the sample." (T & T, p. 281.) Mechanical Analysis. 5. The mechanical or granulometric analysis of sands, etc., is the determination, in any given sand or broken stone, of the propor- tions of grains of diff sizes. It is usually performed by means of sieves or screens. See f 3. Sometimes, for broken stone, &c., by hand-picking. 6. Fig. 1 shows mechanical analyses of a gravel and a sand by Mr. Allen Hazen (Mass. State Board of Health, Report 1892, pp. 546-7). In order to represent both analyses on a single diagram, we have used diff scales for diams for the two materials. 7. In Fig. 1, the diagrams show, for the two materials there represented, that of the sand, 10 % was in grains under, and 90 % over, 0.055 mm diam " " gravel, 10 % ' " " 90 % " 34.5 " " 10 ^ - 2.5 | 2.0 1 "f 0.5 o 5 gr 22^ m=5l ^ ^ 34.5 / 7 / ^^ ^ a&- ^0.055 - JL f^" , ' 7=0 46 "0 OD 20 30 40 50 60 70 80 90 100 fercentage gassing Fig 1. Sand Analyses. * By " sand " or " gravel " we mean a mixture of mineral par- ticles with air, or water, or both; i. e., an aggregation of mineral particles, with voids betw them said voids being filled with air, or with water, or with air and water, as the case may be. Hence, the "volume" of a given quantity of sand or of gravel is the space occupied by both the solid particles and the air or water or both, filling the voids. "Dry sand," or "dry gravel," means: not solid mineral, but a mixture of dry particles of sand (or gravel) and dry air. The solid mineral portion of such sand or gravel, we designate as "solid." SAND. 947 Effective Size. 8. The effective size ("e. s.") of a sand or gravel, as defined by Mr. Hazen (Mass State Board of Health, Report 1892, p 341; Hazen, Filtration, pp 21, 240) is that size, than which 10 %, by wt, of the grains are smaller, and 90 % larger. Or, the length of' the ordinate, at 10 % passing, gives the effective size. Thus, in the cases just mentioned, Fig 1, we have: for the sand, e. s. = 0.055 mm; for the gravel, e. s. = 34.5 mm. Uniformity Coefficient. 9. Uniformity coefficient. Similarly, let m = that diam of grain, than which 60 %, by wt, is smaller, while 40 % is larger. In Fig 1, we have for the sand, m = 0.46 millimeters; " gravel, m = 51.00 The uniformity coefficient (" u. c. "), is m/e. s.; and we have: for the sand, u. c. = 0.46/ 0.055 = 8.4; " gravel, u. c. = 51.00/34.5 = 1.48. 10. With m = e. s., the unif coeff, u. c., would have its least possible value, = 1. In general the less nearly uniform a sand is, as to size, the higher is its "uniformity coeff." 11. In ordinary bank sand, the effective size, e. s., does not vary widely. Hence the uniformity coefficient, u. c. = m/e. s., varies roughly with that diam, m, than which 60 % of the grains are smaller, and thus serves as an indication of the coarseness; as well as of the departure from uniformity, of the sand. (T & T, p. 182.) Feret's Method. 12. Mr. R. Feret (Annales des Fonts et Chaussees, 1892, second semes- tre,) made elaborate experiments as to the effects of fineness of sand, and the mixture of different finenesses, upon the density, etc., of sand and upon different qualities of the mortar. He divided his sands into three finenesses, as follows: Coarse, c, passing 5.0 mm diam = 4 meshes / sq cm = 5 meshes / lin in Medium, m, " 2.0 " " = 36 " / " " =15 " / " Fine, /, " 0.5 " " = 324 " / " " = 46 " / " "Coarse" grains are retained on 2.0 mm diameter; "medium" on 0.5 mm. 4* aO "i'e <*t v;< Sand Analyses, Feret. See U 18. ' x 13. The results, obtained in a certain case, with diff mixtures of these three grades of fineness, are shown in Fig 2, which is similar to diagrams used in connection with alloys of three metals. 947 a CEMENT MORTAR. 14. After a given mixture has been analyzed, and its percentages of the three grades thus determined, it is plotted, in the triangle, by a point so placed that its perp dists, from the three sides, respectively, of the equi- lateral triangle, are as follows: distance from side c = percentage of coarse grains; " m = " medium " / = " fine 15. The plotting of the points, and the measurements of their dists, are facilitated by the lines drawn parallel to the three sides respectively. 16. Thus, point a represents a sand having 20 % fine grains, 30 % medium and 50 % coarse, as shown by the three scales; 20, 30 and 50 being the dists of a from sides /, m and c, respectively. 17. When a series of experiments has been made, upon any given quality (as density or porosity, etc, etc) of sand or mortar, as affected by diffs in mixtures of the three finenesses, they are plotted in this way, and "contour" or " iso "-lines are drawn thru those points which represent equal results in the quality experimented upon. Each "iso "-line therefore represents a series of diff mixtures, each of which will- give the value (as to density or porosity, etc, etc) represented by it. 18. Thus, in Fig 3 (T & T, p 144, Fig 51) the four contours and the point (0.610) represent five diff mixtures of coarse, fine and medium sands, said mixtures having densities (see U 20) of 0.525, 0.550, 0.575, 0.600, 0.610, respectively. I>ensity. 19. Specific gravity or unit weight. Solid quartz weighs about 165 Ibs per cu ft = 2.643 grams per cu cm; sp gr = 2.64 to 2.67. 20. In mechanics (see p. 338, Art. 14 a) density is defined as the mass in unit volume. In sand,* the solid portions have practically constant sp gr. Hence, for a given sand, "density" is used to designate the vol of solid in unit vol of sand, or the ratio of solid to total vol. This ratio is sometimes called the "absolute volume." Thus, in unit vol of sand, "density" = 1 vol of voids. 21. The greater the density of sand,* the less cement will be reqd for a given quantity of mortar. 22. The weight, per cubic foot, of a sand,* of given sp gr. varies directly with its density; and this, in turn, depends upon the shape of the grains, upon their range of size, upon the compacting accomplished, as by shaking, tamping, etc, and upon the dryness of the sand. ^ Voids, percentage of total volume. 8 g 8 5 8 ; i ^ X 1UU . i /* x"^ so 1 Vo *ds / / /^ Le. -ha} dsc e x" fe :$. Tbe presence of clay and loam, in sand, may be de- tected by nibbing the damp sand in the hand, and observing the condition of the hand, or by mixing the sand with clean water and noting the effect upon the water. 34. Washing. Dirty sand may be washed in a specially constructed sand washer; or, by means of a jet from a hose, in a box so arranged that the mud, clay and organic impurities are floated off, leaving the heavier sand behind. 35. Washing may carry off the finer particles of a well assorted sand, leaving it less dense than before. It is well to test a small quantity of the eand, washed and unwashed, before arranging to wash for use. (Jas. C. Hain, E R, '05/Jan/28, p 105.) 36. The degree of sharpness of a sand may be estimated by means of the sound emitted by it when kneaded betw the hands or more cloeely estimated by means of a magnifying glass. MORTAR. 947 d MORTAR.* Constituents. 1. Cement mortar consists of cem, mixt with water, with or without some inert granular material, as sand, fine grayel, stone or gravel screenings, or ground cinder. Without sand, etc., the mixture is called neat mortar, or cement paste. Amount of Mortar Required for a Cubic Yard of Masonry.f Mortar. Description of Masonry. Cu yd. Min. Max. Ashlar, 18" courses and YS joints 0.03 0.04 " 12" " " " " 0.06 0.08 Brickwork (bricks of standard size, 8 MX 4 X 2M ins.): y%" joints 0.10 0.15 Ys" to W joints 0.25 0.35 %" to H" joints 0.35 0.40 Rubble, of small, rough stones 0.33 0.40 " large stones, rough hammer-dressed 0.20 0.30 Squared-stone masonry, 18" courses and M" joints 0.12 0.15 " 12" " " " " 0.20 0.25 2. Effect of roasting and of subsequent wetting-. The materials, of which cem is made, are inert or stable compounds, remaining practically unchanged under ordinary conditions; but when, in burning, the calcareous materials are subjected to high temps, either alone or mixed with argillaceous materials, relatively unstable compounds are formed, ready to enter into new and again stable compounds when their particler are brought into intimate contact by being mixed with water, the water also entering into the new combinations. The mixture then soon "sets" (loses plasticity), and, shortly thereafter, begins to solidify and harden. See H '8, Cement, p 931. 3. In the process of crystallization, the alumina appears to act chiefly as a flux, promoting the formation of the lime silicate, upon which the success of the operation depends. Iron oxide, which is generally present, seems to answer as well as alumina, as a flux, and it requires a less high temp for calcination. 4. The proportion of sand, which should be used in any given case, cannot be properly stated without stating also its range of size, or the proportion of voids to the whole mass; but, in general, good Portland cems will "carry" from 2 to 3 vols of sand; nat cems from 1.5 to 2 vols. 5. Approximate quantities of Portland cement and loose sand per en yd of mortar. Neat 1:1 1:2 1:3 1:4 1:5 1:6 bbls cem 8.0 4.6 3.1 2.3 1.8 1.5 1.3 cu yds loose sand 0.65 0.87 0.97 1.02 1.06 1.10 Cement in Mortar. See also CEMENT, p 930. 6. Owing to the cheapness with which cements are now manufactured, and the superiority of the mortars made from them, the latter have to a great extent superseded lime mortars, even in ordinary building operations. 7. In selecting cem, a reputation, gained by years of successful use and experiment, is of greater value than the results of a few tests; but such tests are of value for excluding inferior parcels of such accepted brands. 8. High grade cements are usually economical, even at a higher cost, as they allow the use of a larger proportion of the cheaper in- gredients, sand, gravel and broken stone. *As the strgth, permeability, etc, of a cone depend largely upon those of its mortar, we discuss, under "mortar," many of its properties commonly discussed under "concrete" t Taken, by permission, from "A Treatise on Masonry Construction," by Prof. Ira O. Baker. New York, John Wiley & Sons. 9th edition, 1907. 947 e CEMENT MORTAR. 9. Free Lime. Cem may contain "free" (uncombined) lime as a result (1) of insufficient manipulation of the raw materials, (2) of insufficient burning, (3) of an excess of lime carbonate (CaCO 3 ) in the raw materials, or (4) of adulteration after burning and grinding. 10. This lime may be present either as quick lime, CaO, or as slacked lime Ca(OH) 2 , either of which may be washed out (the CaO first becoming Ca(OH) 2 ) by infiltrating water. This, of course, weakens the cem. 11. Slacked lime takes no part in the hardening process, but remains as an inert filling material. 12. Quick lime slacks by absorption of the water used in mixing; and, when the burning has been at a high temp, the slacking is delayed. If it takes place during the setting of the cem, the swelling of the lime weakens the cem by rendering it porous. If slacking is delayed until after harden- ing, and if the expansive force is sufficient, the cem is disintegrated. 13. Excess of lime retards setting, and reduces soundness. 14. Free Magnesia. Much uncertainty exists as to the effect of free magnesia, in diff proportions, in cem. Like lime, it expands when wet, but much more slowly; and its presence may therefore remain unsuspected until too late. I>olomite, or magnesian limestone, contains about 45 % of magnesia. Formerly, 1.5 % of free magnesia, in cem, was considered dan- gerous. It is now generally believed that more than from 3 to 5 % weakens the cem, and that 8 % or more causes cracking. In any proportion, it is probably objectionable, at least as displacing an equal quantity of the more valuable lime. Sand* in Mortar. See also SAND, pp 946, &c. 15. The quality of the concrete depends upon the strength of the mortar, and this, in turn, depends largely upon the character of the sand. . 16. For a given proportion by wt, the best sand is that which produces the smallest vol of plastic mortar. 17. Weight. As betw two sands, of a given material, the heavier of course has the smaller vol of voids. 18. Fineness. A fine sand, well assorted as to sizes of grain, and therefore dense, may make better mortar than a coarser sand, with grains of more nearly uniform size and therefore less dense. 19. Extreme fineness prevents penetration of the paste betw the grains, and delays setting. 20. Mortars made with fine sand, altho less permeable than those made with coarse sand, are apt to be more easily acted upon by sea water. 21. Shrinkage. Mortars, with coarse sand, shrink less than those with fine sand. 22. Sharpness. It has been customary to insist upon sharpness of grain, in sand used for mortar, probably owing to the impression that sharp grains form a better bond with the cem or that sharpness indicates freedom From impurities; but the advantage is doubtful. Sands with rounded grains are commonly used, and with entirely satisfactory results; and the laboratory tests generally indicate that sharp-grained sands have no marked superiority Roundness of grain facilitates the packing, and thus increases the density of the sand. 23. The Board of Public Works of Porto Rico, with briquettes of 1 : 2 mortar, found 25 % greater strgth with washed than with unwashed sand. Sand, containing much foreign matter, should be tested before being accepted. 24. In general, the evidence, as to the relative values of sand and of screenings, appears to be favorable to the use of screenings (see Experiments), but opinion is divided. The hydraulicity of the dust, in the screenings, may add to the strength of the mortar. 25. Harry Taylor, Capt, Corps of Engrs, USA, tested 1650 briquettes- of 1- : 3, 1:4 and 1 : 5 mortars, at 1, 3, 6 and 12 mos, with standard crushed quartz, Plum Island sand and crusher dust. Crusher dust gave briquets * See foot-note, SAND, U 1, p 946 MORTAR. ' 947/ 2.3 times stronger than sand, and 72 % stronger than quartz. 1 : 5, with stone dust, stronger than 1 : 3 quartz. 20. G. J. Griesenauer, E N, '03/Apr/16, p 342. Chicago, Mil & St P RR, 225 tests, as follows : Limestone screenings, 1 : 3, passing No 12, held on No 40 sieve, averaged 74 % better than Hammond pit sand, 1:3; with all sizes used, they averaged 115 % better. Mortar of 1 : 6 screenings was 23 % stronger than 1 : 3 sand, dtravel screening's were not much better than sand. 27. Maryland highways. Briquettes, made with stone screening's, were 34 to 62 % stronger than with Potomac River sand. Lime in Mortar. 28. The substitution of 10 % to 20 % lime paste for an equal vol of cem paste, reduces the cost of the mortar, renders it less "short", and slightly retards setting, without seriously diminishing its strgth. Larger quantities reduce strgth. (Baker, Masonry Construction.) 29. Feret found the effect of lime dependent upon the richness of the cem mortar. With 1 : 4 cem mortar, the addition of 4 to 5 % of dry slaked lime increased the strgth; while, with 1 : 1.25 cem mortar, the addition of lime lowered the strgth. (Chimie Appliquee, 1897, p 481.) Clay in Mortar. 30. Laboratory tests indicate that a small admixture of clay increases rather than diminishes the strgths of mortar, and diminishes its permeability; but, in actual work, the clay particles tend to adhere and thus to form lumps having but slight cohesion. 31. Laboratory conditions, as to dryness, pulverization, etc., cannot be reproduced in practice. 32. When the clay occurs naturally in the sand, it may not be practicable to effect a perfect mixture and distribution. 33. Clay, etc, are more likely to give trouble with dry than with wet mixtures. Consistency. 34. Relative strengths of dry and wet mortars, 1: 1. Alfred Noble, over 5000 experiments. Strength of dry mortar taken as 100. T xl 1 XT_A 1 Age 30 days 3 mos 6 mos 1 yr 30 days 3 mos 6 mos 1 yr Dry Mortar. ... 100 100 100 100 100 100 100 100 Moderately stiff. 97 94 97 97 78 89 95 90 Grout 90 92 91 95 63 77 86 82 35. Use dry cone when it is to be heavily loaded at once. Tests indicate that wet and dry cone will be equal in strgth within a year. 36. Wet cone bonds better to 9ld work than does dry cone. Excess of water increases efflorescence and laitance. 37. Rule for percentage, W, of water. H. P. Gillette, Cost Data, p 266. Let S = parts of sand to 1 part cem. Then W = (8S + 24) -H OS + 1). This gives when S = 1 1.5 2.Q 2.5 3.0 3.5 4.0 W = 16 14.4 13.3 12.6 12.0 11.5 11.2 Falk finds that mortars, thus proportioned, adhere well to steel. 38. Slag cement requires plenty of water for its proper hardening. Therefore, if used in air, slag cem mortar should be kept damp. Setting and Hardening. 39. Setting, or the loss of plasticity, usually occurs within a few hours (sometimes within a few minutes) after mixing cem with water; whereas hardening and increase of strength (which appear to result from a different set of chemical processes) often proceed for months or even years, 63 CEMENT MORTAR. 40. Molded blocks of Portland cone, of even 50 tons wt, can generally be handled and removed to their places in from 1 to 2 weeks Initial and Final Set. 41. Initial and final set are stages of the setting process, arbi- trarily distinguished by means of the resistance, of the mortar, to penetra- tion by cylindrical wires, of standard dianis and loaded with standard wts, the blunt ends of the wires resting upon the surf of a pat of the mortar, formed in a flat cylindrical mold on a glass plate. See ^ 8, p 943. Determination of Set. 42. Genl Tottcii, (Genl Q. A. Gillmore, Limes, Hydraulic Cements and Mortars, p 80,) at Fort Adams, R. I., prior to 1830, used a Ha inch wire, loaded with 0.25 Ib, and a J /k inch wire, loaded with 1 Ib; initial and final set being taken as the conditions when these wires, respectively, failed to make an impression upon the mortar. 43. Vicat used but one wire, or "needle." The A S C E (see specifica- tions, p 943) prescribes, for this needle, a diam of 1 mm (0.039 inch) and a load of 300 grams (10.58 oz). Initial set occurs when the end of the needle, penetrating a pat of mortar 4 cm (1.57 ins) deep, can no longer approach within 5 mm (0.2 in) of the glass plate; and final set when the needle fails to sink visibly into the mortar. The mortar, under the setting test, must be of "normal consistency," or such that a cylindrical rod, 1 cm (0.39 inch) in diam, loaded with 300 grams, its end resting upon the mortar, penetrates 1 cm into it. Speed. 44. Speed. Some of the best cems are the slowest setting. A layer of very quick-setting cem may partially set, especially in warm weather, before the masonry is properly lowered and adjusted upon it, and any disturb- ance, after setting has commenced, is prejudicial. On the other hand, quick-setting cements are best in certain cases, as when exposed to running water, etc. They may be rendered slower by adding a bulk of lime paste equal to 5 or 15 % of the cement paste, without weakening them seriously. Nat cems usually set quickly. Slag cem sets slowly. 45. In general, setting is accelerated by high alumina and by soda and potash in the cem, by freshness and fineness of the cem, by the use of warm water and warm sand in mixing, and by warm weather. Set- ting* is retarded by excess of lime and silica in the cem, by the presence of sand, by wetness of mixture, by cold, by retempering, by salt or sulfuric acid in the mixing water, by the presence of 1 or 2 % of lime sulfate, either hydrated (gypsum) or anhydrous (plaster of Paris) or of slaked lime, in some cases by hard burning, and. in general, by the age of the cement, but the storage of new cem in warm places accelerates setting. 45 a. Gypsum. CaSO 4 . Time of setting (initial and final) increased rapidly with additions of gypsum up to about 2 %, and remained constant, or increased slightly, up to 4 %. E. Candlot, "Ciments et Chaux Hydrau- liques." 45 b. Time of setting (initial and final) increased, up to about 1.5% gypsum, but then decreased, as the gypsum was increased to 7 %. Knis- kern and Gass, Sibley Jour of Engng, '05, Jan. 45 c. Calcium chloride, CaCl 2 . A weak solution retards, but a concentrated solution accelerates, the setting of Port cems. Thus, with 10 to 40 grammes per liter, the time of setting reached 500 to 850 mins ; while, with 200 to 300 grammes per liter, it was reduced to from 2 to 25 mins. Cems with very high or very low alumina are but little affected by CaCl2. A weak solution (30 to 60 grammes per liter) may render sound a cem con- taining free lime, by facilitating the hydration of the lime. E. Candlot, "Ciments et Chaux Hydrauliques. " 45 d. From % to \% % dry CaCl 2 , ground with cem clinker and made into pats of normal consistency (See Tests, H 7, p 943) increased the time of initial set from 2 to 167 mins, and that of final set from 52 to 275 mins. With 6 %, the times were 68 and 145 mins respectively, Kniskern and Gass, Sibley Jour of Engng, '05, Jan. 46. Setting is attended by an increase of temperature. In quick setting, this increase may amount to 10 C (18 V) or more. MORTAR. 947 /i 47. Slow setting cems are apt to harden more rapidly than quick setting. 48. In warm air, setting cem, in drying, loses the moisture upon which the operation of hardening depends. It therefore sets without hardening-. In hot weather every precaution should be taken against this. 49. Cems of the same class differ much in their rapidity of harden- ing-. At the end of a month one may gain nearly one-half of what it will gain in a year, and another not more than one-sixth; yet at the end of a year bolh may have about the same strength. Hence, tests for 1 week or 1 month are by no means conclusive as to the final comparative merits of cements. 50. Many years are required to attain the greatest hardness: but after about a year the increase is usually very small and slow, especially with neat cem. Moreover, any subsequent increase is a matter of little importance, because generally by that time, and often much sooner, the work is completed and exposed to its max loads. 51. Cems which are slow-setting when made, are apt to become quick- setting (or "flashing"*) when stored, especially in warm places, and if the cem is underlimed. This is attributed to disintegration of the particles and consequent increase in fineness. The change sometimes take* place very quickly. This difficulty can usually be overcome, without reducing the strgth, by storage in cool places and by adding 1 to 2% of slaked lime. Oh small jobs, a few lumps of lime may be added to each bbl of mixing water. 52. The requirement, not uncommon in specfns, that a certain percent- age of increase of strength must take place between 7 and 28 days, tempts the mfr to grind the cem coarsely, or to adulterate it with inert material, in order that it may not gain too much of its strgth within the first 7 days. Properties. Soundness. 53. ITnsoundness, in cem mortar, is the tendency to expand, contract or disintegrate in air or water, or under heat and cold. See Specifications. 54. Cem, of any established brand, will seldom be found deficient in strength; but may be deficient in soundness, upon which durability depends. 55. Unsoundness is generally due to excess of, free lime, arising from incorrect proportioning, overburning, lack of seasoning, or coarseness of grinding; the latter preventing perfect hydration. The presence of lime sulphate (gypsum plaster of Paris) is favorable to soundness. Unsound cern is improved by storage. 56. Change of dimensions during hardening of concrete. Cone, placed in air, shortens or shrinks during the first two or three months; while cone, in water, expands during about the same time. These changes are greater with those cones having the larger proportions of cem. 57. Shrinkage of mortar set in air. per cent. ins. per 100 ft. Neat cement,* 0.132 to 0.140 1.58 to 1.68 Mortar, 1 : 1,* 0.080 to 0.170 0.96 to 2.04 Lean mortars.t 0.030 to 0.050 0.36 to 0.60 The expansion ill water is somewhat less than the contraction in air. The total change in dimensions is the algebraic sum of that due to setting, and that due to temperature changes. 58. Cone shrinks less when it sets under pressure. Fineness ot sand is conducive to shrinkage. * Trans. A S C E, Vol xvii, 1887, p 214. t Considere. Experimental Researches on Reinforced Concrete. Trans- lation by Moissieff , p 87. 947 i CEMENT MORTAR. Strength. 59. Cem mortars are usually tested (by means of briquets) for tensile strength. 60. Factors affecting strength. The strengths of samples, under test, are much affected by the temperature of the air and water, as also by the force with which the cem is pressed into the molds; by the extent of setting before being put into the water, and of drying when taken out; and still more by the pres under which it sets, which increases the strength materially. On this account, cems, in actual masonry, may, under ordi- nary circumstances, give better results than in tests of samples. The causes named, together with the degree of thoroness of the mixing, the proportion of water used, and other considerations, may easily affect the results 100 % or even much more. Hence the discrepancies in the reports of different experimenters. Specimens of the same cem, tested under apparently similar conditions, may give widely diff results. 61. Personal equation. In connection with the building of the Croton Aqueduct, New York, one set of testers, testing 835 briquets, ob- tained an av strgth of 62.3 Ibs per sq in; while another set of testers, testing 2434 exactly similar briquets by the same methods and under the same circumstances, obtained an av strgth of 85.2 Ibs per sq in, or 36 % greater. 62. Owing to such uncertainties, a series of tests, to be of value, must cover a large number of specimens, in order that the accidental diffs may be averaged. 63. Diffs in comparative results with diff materials may be due to one or other of several diffs betw the materials. Thus, in comparing mortars made with clean and with dirty sands, the strgths may be more affected by diffs in density than by the diffs in cleanness of the sand. 64. Effect of age. The diagram,* Fig 1, illustrates approx the strengths of av Portland and of av nat cems, neat and with 2 and 3 parts 000 14334 O Weeks JUotithii Fig 1. Age and Strength of Mortar. 1 Year 2 years of sand, up to an age of two years. Tests may readily vary 10 per cent or more eitherway from the average. * See Richard L. Humphrey, in "Cement," Chicago, May, 1899. MORTAR. 947J 65. Fig 2 * shows, approximately, the effect of sand, in diti proportions, upon the strengths of Portland and natural cements, at diff .S 700 01 234567 Parts of Sand to 1 fart Cement Effect of Sand upon Strength. Fig 2 ages from 1 week to 1 year. The four solid curves represent average Port- land cements, and the four dotted curves represent average natural cements. For each kind of cement, the curves represent ages of 1 year, 6 months, 1 month and 1 week, respectively, beginning at the top. The curves for natural cement are carried only to 5 parts sand. 66. The compressive strengths of cem mortars, in cubes, appear to be about 8 to 10 times their tensile strengths, and their shearing strgths about Vi their tensile strgths. 67. The adhesion of cem mortars to bricks or rough rubble, at diff ages, and whether neat or with sand, may be taken at an av of about % the tensile strength of the mortar at the same age. If the bricks and stone are moist and entirely free from dust when laid, the ad- hesion is increased; whereas, if very dry and dusty, especially in hot weather, it may be reduced almost to nothing. The adhesion to very hard, smooth bricks, or to finely dressed or sawed masonry, is less than the adhesion to rough and porous surfs. 68. Dr. Bohme, Berlin, found tensile strgth -=- adhesive strgth = 10, with 1 : 3 and 1 : 4 mortars, and = 6 to 8, with neat and 1 : 2 mortars. Finish. 69. Lime mortar and cems, when used as mortar for brickwork, often disfigure it, especially near sea-coasts, and in damp climates by white efflorescence, which sometimes spreads over the entire exposed face of the work, and also injures the bricks. This occurs also, to some extent, with Portland cems; also in the mortar joints of stone masonry, but to a much leas extent. It injures only porous stone. It is usually a hydrous soda or potash carbonate, or magnesia sulfate (Epsom salts) often with other salts. As a preventive, General Gillmore recommends to add to every 300 Ibs (1 bbl) of the cem powder, 100 Ibs of quicklime, and from 8 to 12 Ibs of any cheap animal fat; the fat to be well incorporated with the quick- lime before slacking it, preparatory to adding it to the cem. This addition will retard the setting, and somewhat diminish the strength of the cem. It is said that linseed oil, at the rate of 2 gals to 300 Ibs of dry cem, either with or without lime, will, in all exposures, prevent efflorescence; but, like the fat, it greatly retards setting, and weakens the cem. See also Bricks, p 929. 70. For pointing, the best Portland cem should be used, and is best used neat, but it is often used with from 1 to 2 parts of sand. Mix under shelter, and in quantities of only 2 or 3 pints at a time, using very little water; so that the mortar, when ready for use, shall appear rather incoherent, and quite deficient in plasticity. The joints being previously scraped out * Compiled, by permission, from Prof. Baker's "Masonry Construction." 947 k CEMENT MORTAR. to a depth of at least half an inch, the mortar is put in by trowel; a straight- edge being held just below the joint, if straight, as an auxiliary. The mortar is then to be well calked into the joint by a calking-iron and hammer; then more mortar is put in and calked, until the joint is full. It is then rubbed and polished under as great pressure as the mason can exert. If the joints are very fine, they should be enlarged by a stonecutter, to about ^4 inch, to receive the pointing. The wall should be well wet before the pointing is put in, and kept in such condition as neither to give water to, nor take it from, the mortar. In hot weather the pointing should be kept sheltered for some days from the sun, so as not to dry too quickly. Behavior in Water. 71. Ijaitance. "When cone is deposited in water, especially in the sea, a pulpy gelatinous fluid exudes from the cem, and rises to the surface. This causes the water to assume a milky hue; hence the French term, laitance. As it sets very imperfectly, and, with some varieties of cems, scarcely at all, its interposition betw the layers of cone, even in moderate quantities, will have a tendency to lessen, more or less sensibly, the continuity and strgth of the mass. It is usually removed from the inclosed space by pumps, which must be used cautiously, to avoid disturbance of the cone by currents. The proportion of laitance is greatly diminished by reducing the area of cone exposed to the water, as by using laroe boxes, say from 1 to 1.5 cu yds capacity, for immersing the cone." (Gillmore, "Limes, Hyd. Cems & Mortars.") 72. Authorities differ as to the effect of sea water. H. LeChatelier (Internatl Assn for Testg Materials, Procs, 1906), finds that the active in- gredients of cem (lime, aluminates, silicates) are decomposed by the magne- sium salts of sea water, yielding soluble calcium chlorides and lime sulfates. The latter, with lime aluminate, forms a compound whose crystallization tends to swell and crack the material. 73. In view of the notable puddling effect of percolating water, it would appear that sea water especially, with its numerous salts, ought shortly to block its own passage into the cone. 74. The substitution of iron for alumina, in cem, is found to remove one of the most active reagents in the deteriorating effects of the salts in sea water. See Cement, U 30, p 933. 75. The disintegration of cone in water (salt or fresh) ap- pears to be due less to action of the water itself than to the repeated action of frost where the cone is alternately exposed to freezing temps between high and low water. 76. Mortar of puzzolano and lime has remained in perfect condition for 15 to 20 centuries in Italian harbor works. 77. At the dock at Kobe, Japan, to avoid possible injury, the salt water, inside the dam, was replaced with fresh water, which entered at the surface, while the heavier salt water was pumped out from the bottom. For Concrete, see pages 1084, etc. ABBREVIATIONS. 947 I Abbreviations, symbols and references, in general use in the articles on Cement, Sand and Mortar, pp 930-947 k, and on Concrete pp 1084-1210. For references to specifications, see pp 1184-5. agg aggregate A S T M American Society for Testing Materials ASCE American Society of Civil Engineers Assn Eng Socs. . .Association of Engineering Societies cem cement cone concrete constr construction c c cubic centimeter d day elas elastic E N Engineering News E R Engineering Record expt experiment h, hr hour Instn C E Institution of Civil Engineers Jour Journal kg kilogram km kilometer m meter mm millimeter mo month mod modulus mom moment nat natural Port Portland Procs Proceedings reinfd reinforced . reinfmt reinforcement specf n specification standd standard surf surface T&M Turneaure and Maurer, "Principles of Reinforced Con- crete Construction," 1907. T&T Taylor and Thompson, "Concrete, Plain and Reinforced," 1905. Trans Transactions transv transverse U. S. A Report, Chief of Engrs, U. S. Army. wk . .week / per U square G" square inch > greater than, more than < less than > not more than, equal to or less than. < not less than, equal to or greater than, at least. 1084 CONCRETE. CONCKETE. For Cement, Sand and Mortar, sec pages 930, etc. For abbreviations, symbols and references, see p 947 I. AGGREGATES.* Constituents. 1. Order of value. (1) Trap, (2) granite, (3) gravel, (4) marble, (5) limestone, (6) slag, (7) sandstone, (8) slate, (9) shale, (10) cinders. 2. The strath of cone, with good sandstone, is about 0.75 X strength with trap. With slate, less than half strength with trap. Good cinders nearly equal to slate and shale. Hardness of agg increases in importance with the age of the cone "because, as the cem becomes hard, there is greater tendency for the stones themselves to shear thru, and the hardness of the agg thus comes into play." (Sanford E. Thompson, E R, '06/Jan/27, p 109.) 3. The choice of agg is of course a matter of cost, as well as of strength, &c, of product. Thus, with gravel sufficiently cheap, as compared with broken stone, it may be economical to use the gravel, or a mix of gravel & stone, obtaining the reqd total strgth by Using a larger mass of cone. In foundations, on weak ground, this is advisable because it distributes the load over a greater area. 4. In many cases, the choice of sand and agg depends largely upon what material can be had, and upon its distance from the work. 5. Where cem is cheap, it may be economical to use materials nearest at hand, and to depend, for quality, upon excessive use of cem. 6. Stone which breaks into nearly cubical fragments packs better than that which splinters into long pieces, and the fragments are less apt to break in the finished work. 7. Good broken stone is usually preferred to gravel. The roughness of the stone particles is believed to give better adhesion. Gravel cone cannot well be tooled. 8. Cinders are sometimes used for the agg. They are ordinarily those resulting from the burning of bituminous coal under boilers. The material is mostly a fine ash, containing considerable unburned coal. 9. Anthracite cinders are less extensively used, the supply being less abundant. 10. Cinder cone, weighing only from 80 to 100 Ibs per cu ft, is of advantage where lig'htness is reqJ. Broken stone or gravel cone weighs from 140 to 145 Ibs per cu ft. 11. Clay or loam, adhering to gravel particles, destroys or weakens the adhesion of the mortar to the stones. The Boston Transit Commission, Report for 1901, page 39, found the ratio of strength, betw cone with clean and dirty gravel, about 60 : 45. See "Clay and Loam," under "Sand" and "Accidental ingredients," p 1135. Size. 12. In beams, arches, &c, the size of aggregate should not exceed 1.5 to 2 ins on any edge; but, if it is well freed from dust by screening or washing, and if the mortar completely fills the voids, all sizes, from 0.5 to 4 ins. on any edge, may be used in mass work, as foundations, dams, piers, etc. 13. With large agg, coarse sand should be used, and vice versa. 14. It is usually economical of cem. to screen sand from gravel, or fine material from crusher stone, and then remix in the required propor- tions. Density. 15. When a solid body is reduced to a mass consisting of broken pieces separated by voids, the increase in bulk is due solely to the voids, and is * By "aggregate," we mean the solid materials of cone, other than the cem and sand. The term "aggregate" is sometimes used as including the sand also. PLAIN CONCRETE. 1085 equal to the space occupied by them. Hence the ratio, betw the increase of bulk, or ' swelling," and the original bulk, is that of the voids to the original, and not to the final bulk. Thus, if a solid cu yd of stone, after being broken into pieces, occupies twice as much space as before, then the increase in bulk, or the space occupied by the voids, is = that occupied by solid pieces = half that occupied by the entire broken mass. 16. In sharp and angular broken stone, having all its pieces of nearly uniform size, about 50 per eent of the vol, when measured loose, will be voids. If the sizes of the stones vary betw somewhat wide limits, as from 2 ins down to % inch, the vol, occupied by the voids, will be less, often as little as from 28 to 30 % of the whole. 17. Tests by Mr. Wm. Hall (Trans A S C E, Vol 42, 1899, p 132) of voids in crushed Green River blue limestone, 2.5 inch, screened; very clean Ohio River gravel, 1.5 inch, and mixtures of the two, resulted as follows: Percentage of stone... ..100 80 70 60 50 " gravel 20 30 40 50 100 " voids 48 44 41 38 36 35 These are ays of a number of tests of several bargeloads of materials, but there was little variation betw the mixtures. 18. Stone Crushers. See Price-list, p 992. Cyclopean Concrete. 19. "Cyclopean" cone, consisting of large, rough stones ("dis- placers" or "plums") laid in cem mortar, is largely, economically and ad- vantageously used in mass work, especially in dams, where wt and hot shearing strgth are desiderata. The stones need not be flat. They are usually dropt into the wet mortar, without other bedding than that due to their fall and wt. Wet cone facilitates the bedding of the stones, and bonds better with them than does dry cone. 20. At Chaudiere water power dam, Canada, the "plums" were obtained from hard ledges in the river bed, in good shape for bedding. Their agg vol av'd betw 25 and 30 % of the vol of the dam; max, 40 %. 21. At Transmere Bay Development Works (Procs Inst C E, Vol 171, 1908, p. 145) the "plums were of sandstone, 9 ins apart hor'y. Near the bases of the walls, they weighed a ton or more. The proportion of plums decreased, with wall thickness, from 10 to 7 % of the whole mass. 22. Unnecessary restrictions, imposed upon contractors, may eliminate the profit due to the use of "plums." See H 19. 1 086 CONCRETE. P:LAI:N CONCRETE. 1. Cement Concrete is composed of broken stone, gravel, cindera, slag, shells, or other hard and inert * material (the aggregate), held together by cement mortar, composed of cement and sand. Advantages. 2. The principal advantages of cone are the convenience with which it may be placed, particularly in otherwise difficult situations or under water; its availability for subaqueous work; its cheapness, due largely to convenience of placing and to its use of stone too small for masonry; and its fire-resisting qualities, as compared with limestone (which calcines) and with granite (which splinters). 3. The availability of C9nc has been very greatly extended by the practice of reinforcement, which permits its use (heretofore often impracticable "> in members subject to tension as well as to compression, as in beams, in cantilevers (including dams and retaining walls), in columns, and in arches where the rise is either very great or very small, relatively to the span. Reinforcement permits the use of much lighter sections than would have been safe when use was made only of the compressive strength of the material. For reinforced concrete, see p 1110. 4. Disadvantages. Cone is rather weaker than good rubble masonry. and has only about half the strength of first class ashlar masonry of granite with thin joints in cem. Like both the stone and the mortar in masonry, it is subject to deterioration, especially in sea water; but this difficulty is being eliminated by the care which is being given to the manufacture of cem and which is fostered by its extensive use and by the conduct of its manufacture upon a large scale. As in all human work, and notably in the laying of masonry, care is necessary in order to secure faithful performance, upon which the success of the structure so intimately depends. The quality of the finished work may, however, be tested by borings. 5. Cone is used for bringing' np uneven foundations to a level before starting the masonry. By this means the number of hor joints in the masonry is equalized, and unequal settlement is thereby prevented. <$. On railroad work, the use of cone may obviate tlie use of der- ricks, which are a source of interference with, and danger to, trains. 7. Cone is \ised to advantage.in reinforcing and protecting old stone masonry ; but, unless special precautions are taken, the two construc- tions are liable, in time, to separate, owing to unequal settlement, especially if the ramming has not been thoro. Natural Cement. 8. Natural cement is now seldom used in cone, except in mass work where it is not subjected to the wearing action of water or frost, and where early strength is not reqd. It is suitable for footings and for low retaining walls not subject to serious vibration. 9. In dams, breakwaters, etc, the core is frequently of natural cement cone ; with a substantial outer shell of Portland cem cone. Proportions. 10. The proportions of cement, sand and aggregate should cheoretically be determined, either all by wt, or all by measure in loose condition; but, in practice, the cem is measured by the number of pack- ages used (the contents of the packages being known; see "packages," under "Cement") and the sand and agg are measured loose. * Without chemical affinity for other materials. PROPORTIONS. 1087 "Natural Mix." 11. It is customary to designate the quantities of cem, sand and agg, in a cone, by proportions. Thus: 1:2:4 means 1 part cement to 2 parts sand and 4 parts aggregate. Such designation is necessary in instructions to workmen; and, where the ranges of size of the particles are known, it indicates the character of the cone. The proportions are of course governed by the character of the work; but it is inadvisable to affect distinctions between nearly similar classes of work. 12. Usual proportions for Portland cement concrete : Exceptionally massive work (leveling for foundations, dams, breakwaters). 1 : 1.5 : 8 to 1 : 5 : 10; with nat cem, 1:2:5. Foundations, ordinarily, 1:3:6; sometimes as poor as 1 : 4 : 8. Piers, pedestals, abutments, 1 : 2.5 : 5.5 to 1 : 3.5 : 7. Piers and vaulting in filters, 1 : 2.5 : 5.5. Reinforced walls and beams, 1:3:6; light sections, 1 : 2.5 : 5. Foundation walls, 1 : 2.5 : 5.5; retaining walls, 1 : 2.5 : 5.5 to 1:3: 6. Spandrel walls, 1:3:6. Conduits, drains, sewers, 1 : 2.5 : 5.5 to 1:3:6. Reservoir, filter and tank walls, 1 : 1.5 : 3.5 to 1 : 2.5 : 5.5. Subaqueous work, 1 : 2 : 3. Floor systems (girders, beams, slabs) 1:2:4 to 1 : 2.5 : 5.5. Stairways and roofs, 1 : 2 : 4. Arches, 1 : 2.5 : 5; light sections, 1:2:4. Copings and bridge seats, 1:1:2 to 1:2:4. But the essential requisite is that all the voids, between the particles of sand and agg, be filled with cem mortar. Hence, unless the grading of sizes, of sand and of agg, is known or assumed, the bare statement of proportions, of cem, sand and agg, in a mixture, gives but little useful information as to the value of the cone. 13. In reinforced work, in general, richer mixtures should be used than those that would be permissible in large mass work. In order to obtain proper and reliable adhesion, which is of the first importance, the bars must be completely surrounded by cem. Materials Required. 14. Materials required for a cu yd of rammed Portland cement concrete, c = cement, bbls; s = sand, cu yds; a = aggre- gate, cu yds. Dust screened out. Stones not larger than 1 inch. ixti z ire 4 c s a 1 46 44 89 2 5.5 5 1.19 0.46 0.91 1.11 51 085 6 1 01 46 92 n 4 7 7 0.91 0.42 0.97 83 051 89 4 8... , . . 0.77 0.47 0.93 With 2.5 inch stone, the quantities of all the materials, per cu yd cone, were increased from 2 to 5 %. With gravel, > % inch, they were decreased about 9 %. (Chas. A. Matcham, Natl Builders' Supply Assn, 1905.) 15. Let B = No. of barrels of cement reqd per cu yd cone = No. of times 0.141 cu yd cement reqd per cu yd cone; P == parts of sand (or agg) to 1 part cem. Then l/B = No. of cu yds cone from 1 bbl cem; 0.141 P = No. of cu yds sand (or agg) to 1 bbl cem; 0.141 PB = No. of cu yds sand (or agg) to 1 cu yd cone 1088 CONCRETE. Void*. See Weight, p 1103. 16. Reduction of voids. If stone having 50 % voids, and sand having 50 % voids, be used, with cem, in the proportions: Cement, 1 part = 0.25 cu yd Sand, 2 parts = 0.50 cu yd Stone, 4 parts = 1.00 cu yd the resulting cone will measure something more than 1 cu yd, and yet it will contain unfilled voids. 17. These proportions, however, are not economical By selecting a sand having a range of size, or by mixing two or more sands having grains of diff sizes, the voids in the sand can be reduced to say 33 %. Simi- larly, the voids in the stone can be reduced to say 35 %. We should then y have, say: to say 35 % Cement, 1 part = 0.12 cu yd Sand, 3 parts = 0.36 cu yd Stone, 8 parts = 1.00 cu yd, with results as good as with the 1:2:4 mixture above, although using only half as much cement. 18. Mr. Geo. W. Rafter (Trans A S C E, Dec, 1899, Vol 42, p 106) recom- mends that the proportions be stated by means of the ratio of the vol of the mortar to the vol of agg. Thus: a cone containing 75 vols of agg and 25 vols of mortar, would be a 33> % cone. 19. Under usual conditions, the voids in the agg should be filled with as rich a mortar as the strength of the work demands. A better cone may result from the use of a lean mortar which fills the voids, than with a richer mortar but partially filling the voids. 20. The mortar cannot be perfectly distributed thru the agg, and some of the voids are too small to admit the sand grains. Moreover, the mixture is liable to disturbance in depositing. Hence, there will be voids in the cone- unless there is an excess of mortar over the measured voids of the agg. 21. In practice, the excess of volume of mortar required, over the measured voids in the agg, in order to secure the filling of the voids, is usually from 15 to 25 % of the vol of the voids. But by 15 exp'ts with limestone, Prof. Baker found that the voids were not entirely filled unless the vol of the mortar exceeded the vol of the voids by 40 %. (Table 13 c, p 112 b, Baker's Masonry Construction, 1907.) 22. Mr. John Watt Sandeman (Procs, Instn C E, Vol 121, p 219, 1895) believes that, to insure watertightness, the vol of mortar should be 50 % of the vol of agg having 35 % voids; or, excess mortar = 43 % vol of voids. r l F I * 100 100 80 20 Fig 1. Diameter, d, in inches. Parabola of Maximum Density. See U 23, p 1089. PROPORTIONS. 1089 Density. See Weight, p 1103. 23. Mr. Wm. 8. Fuller (T & T, p 197) finds that the greatest density is obtained, and consequently the smallest amount of cem reqd., when the agg and the sand are so graded that the percentages, by wt, passing the various sieves, are as represented by the ordinates of the parabola in Fig. 1, where the abscissas represent the diams, d, of the openings in the sieves; while the ordinates below the parabola represent the percentages passed, and those above the parabola the percentages retained, by these openings respectively. 24. In this parabola d = P 2 M ; where d = a given diam; P = proportion of particles smaller than d; M ~ max diam of stone ( = 2 ins in the Fig). 25. Exp's (Trans A S C E, Vol 59, pp 67, &c, 1907) show that a saving of 12 % in quantity of cem may be effected, and a more impervious pro- duct obtained, by thus grading the sizes of the sand and agg; but the reduc- tion may sometimes be offset by the additional cost of so grading, especially on small work. 26. In the lining of the tunnel for the Sudbury aqueduct, Boston Water Works, the proportions were 1 cask of Portland cem as it came fi 2% casks of loose sand 5 H casks of loose crushed stone the dealer = 3.425 cu ft = 7.35 cu ft . . = 18.56 cu ft Total . . 29.335 cu It. By slightly shaking the sand and stone, the proportions became practically 1:2:5. These 29.335 cu ft produced from 20 to 21 cu ft cone, rammed in place: or say 38 cu ft materials = 1 cu yd cone 27. Mr. Wm. B. Fuller (Natl Assn of Cem Users, Procs, '07, p 95) tested cone beams, 30 days old, of 1:2:6, 1:3:5, 1:4:4, 1:5:3, 1:6:2 1:8:0, (all 1 : 8). The strgths compared as in Fig 2. s $ vnn 319 tupture Modulus, Ibs./ 8 Q c => & 2 285, *. 209 x^ 151 x x^ 102 ^^^ ^^. -^"^ a Aggregate, Parts. Fig 2. Proportions ; strength. 28. From this it appears that, so long as the voids in the agg are filled with mortar, the comp strength of cone seems rather to increase than diminish as the proportion of stone increases, and to depend largely upon the richness of the mortar. 29. Proportioning by trial mixtures: (Wm. B. Fuller, Trans A SCE, Vol 59, pp77, &c).' Having determined the particular sand and stone to be used on any work, provide a strong and rigid cylinder, such as a short piece of 10 inch wrought iron water pipe capped at one end. SO. On a piece of sheet steel or other non-absorbent material, weigh out and mix together all the ingredients, to the consistency required for the work. Place the mixture in the cylinder, tamping carefully and continu- C5 1090 CONCRETE. ously, and note the height to which the cyl is filled. Before the mixture has time to set, empty and clean the cyl 31. Make up another batch, using the same wts of cem and of water as before, and the same total weight of sand and stone, but with a slightly diff ratio of weights of the sand and stone. 32. Note the height, in the cyl, reached by this second and by subsequent mixtures. The best mixture is that which gives the least height in the cyl, provided that it works well while mixing, and that its appearance in the cyl shows that all the stones are covered with mortar. 33. This method enables the engineer to select the best from the materials available in any given case. Consistency. See also Mortar, p 947/. 34. Skill and care, in placing, and uniformity of consistency are more mportant than the consistency itself. 35. The extremes of practice are: (1) Cone with mortar about as moist as damp earth; only enough water used to show on the top surf after prolonged and hard tamping, (2) enough water used to cause the cone to quake when first placed, and to allow only of spading into place. The proper consistency depends largely upon the character and purpose of the work. 36. Dry cone is generally preferable in large open work where it can be thoroly rammed, and where early strength is reqd, as in arch skew-backs. When thoroly tamped, it develops much higher compressive strength at itg early ages, and may have somewhat greater permanent strength, than wetter mixtures; but imperfect tamping of such mixtures may result in very weak cone, while thorough tamping may render the work more expen- sive than the increased strength will justify. 37. Medium. Present practice favors the use, in general, of mixtures wet enough to require only spading; but, even in such work, ramming may be reqd from time to time for occasional dry batches. 38. Wet cone is more easily mixt with thoroness, more readily and more cheaply laid, and more easily forced into the narrow spaces betw reinforcing bars. It comes into more perfect contact with the molds, thus giving smoother and more nearly watertight surf. It is therefore generally preferable (as in buildings) in forms of complicated shape, or in thin sections, or where smooth surfaces are reqd. 39. Wetness retards setting, gives better bond between successive courses, gives a compact mass with less tamping, and provides the surplus water reqd by absorption in wooden forms. Wet cone is less liable than dry to injury by bad workmanship; but an excess of water reduces the strgth, and increases efflorescence. 40. In " cyclopean" cone, more "plums" can be used with wet cone, which allows them to settle down into it, and which bonds better with them. 41. Mixtures, wet enough to be poured into the forms for columns of floors, are frequently used. 42. The quantity of water required, for a given consistency, is materially reduced by wet weather. 43. Water works upward thru placed cone. Hence a less pro- portion of mixing water may suffice toward the end of a day's work. II A \IM \ M I \ I \ 450 cu ft per day. 48. In the choice of a mixer, reliability, as established by success- ful use, is of prime importance, especially where continuity of work is essential. 49. Shortage of output may be due to shortage of power behind the mixer, as well as to the mixer itself. 50. The mixer should be cleaned after each day's work. PL.ACIXG. 51. The best cone may be rendered almost worthless by carelessness or improper method in the placing. 52. When cone is dumpt from a considerable height, there would seem to be danger that the even distribution of materials may be disturbed. Hence, if lowered in buckets, these should be brought close to the work already done, before dumping. However, in the construction of 1094 CONCRETE. pone piers for a bridge at Bethlehem, Pa., by Cramp & Co. (E R, '09 /Mar /6, 280) cone was delivered, thru an inclined wooden shute, lined with sheet on, at a point vert'y 74 ft below the mixer; and the method was found to be economical, and the cone uniformly good, and there was no difficulty from separation of ingredients. 53. In work that will show, the layers are usually restricted to about 6 ins in depth, owing to the difficulty of spading the face work when the layers are thicker; but in foundations, and in heavy work above ground, if to be faced .with masonry, or if appearance is not important, layers of wet cone as deep as 2 feet may be used. 54. If the cone, after placing, is found to be too wet, it is better t-> correct the trouble by placing drier cone upon it. When surplus water is bailed out, some cem is carried with it and thus wasted. 55. Excessive lace spading brings up water from below, and thit washes cem from the face. 56. Works of considerable length, such as dams and walls', are commonly built in sections alternately, thus: sees 1, 3, 5, etc, are first built separately, and, when they have hardened, sec 2 is built betw sees 1 and 3, section 4 betw sees 3 and 5, etc. The sides of sees 1, 3, 5, etc, thus serve as part of the forms for sees 2, 4, etc. This method facilitates bonding betw the sees, by means of vertical dove-tail grooves, formed, by the molds, in the sides of the sees first built. The cone of the remaining sees, placed later, enters and fills these grooves. 57. In freezing weather, cone can be laid in large masses in water or below the ground surf. In excavations, if the ground water is permitted to rise over the work during the night, it will usually prevent frost from reach- ing the cone. 58. At Chaudiere water power dam, cone was laid in temps as low as 2O F. A mixing house was erected, and the temp, within, was kept, by stoves, above freezing. Materials were lowered into the house by derricks thru hatchways in the roof. Water was kept in casks, and kept lukewarm by steam jets. Sand was heated outside the house. Stone, in piles 3 to 4 ft deep, was heated (but not dried) by steam jets from a perfo- iles. After placing, the cone was loosely the nozzle of a steam hose was introduced. rated pipe, passing under the piles. After placing, the cone was Iposely sred with canvas, under which the Forms. 59. In waU foundations, the trench itself may constitute the form; and, in dams and arches of cone blocks, the first blocks, placed alternately, often serve as parts of the forms for the remaining blocks; but ordinarily a considerable amount of timber framing is required. See ^ 56. 60. The economy of the work depends so largely upon the design of the forms, that it is often advisable to modify the design of the work itself, or to use more cone than would otherwise be nec'y, in order to secure economy. The design should be such that commercial sizes of lumber may be used, and with a min of wasteful cutting; and such that the forms may be readily erected and removed with a minimum of damage to them- selves and. no damage to the work, and used repeatedly. Where practi- cable, the forms are made in sections, small enough to be conveniently moved and handled separately. Cutting is economically done by power saw benches. 61. Even in building work, where much of the "centering" must be built in place, and where it can be removed only by taking it to pieces, the lumber may be used two or three times before it is discarded. Where the forms can be assembled in panels, and these panels removed as units, they may be used many times. 62. The requirements of different works, executed under diff conditions, vary so widely, that no useful details, as to the construction of the forms, etc, except for buildings (see Ulf 63 etc), can be given within the limits at our disposal. The designer should witness the removal of his forms before estimating their success. FORMS. 1095 Forms for Buildings. 63. In reinfd building: construction, the forms are chiefly : (a) Column forms, (b) Beam, slab, floor and roof forms, (c) Wall forms. 64. A typical column form, Figs 1 and 2. The boards, G, 1% ins thick, are held in place by cleats, H, 1*4 X 5 ins, and by "column clips," C, made of pieces 4X4 ins, and boards, B, 1 % X* 5 ins. These "column clips" must be spaced to take the pres due to the cone. At the bottom of a column 18 ft high, they should be > 10 ins, cen to cen. At. the bottom, 4 boards, A, are used, to hold the form in shape, and the boards, G, are cut, on one side of the box, at F, 2 or 3 ft from the bottom, to form a door (cleats, on door, not shown), thru which all rubbish may be brushed. The door is then held shut by the lower two "column clips," and the form is filled Triangular fillets, T, are used to bevel the corners of the col. Fig 1. Fig-s 1 and 2. Column Form. 65. Column forms should be so designed that they may be removed without disturbing the forms for the beams and girders. The col forms may then be bared for inspection, before being loaded. Fig- 3. Beam Form. 1096 CONCRETE. 66. Typical beam or girder forms. Fig 3. The forms, or beam- boxes, often miscalled "centers," are supported, betw columns, by tempo- rary struts or shores, /, 4 X 4 ins, about 6 ft apart, resting on wedges, J, and the plank K. Corbels, H, 4 X 4 ins, are placed directly under the bottoms, G (1 M ins thick) and sides, C (1 M ins thick), of the beam boxes. The sides, C, are held together by cleats, E, 1 M X 5 ins, 2 ft apart, to which are nailed the strips, D (1 M X 6 ins), upon which rest the ledgers, B, 2 X 6 ins, about 27 ins apart. These support the panel boarding, A, 1 J4 ins thick; and this, in turn, supports the slabs. Small triangular fillets, T t in the corners of the beam boxes, make the box tight and give beveled cor- ners to the beam. Beam forms should be given a slight camber. 67. Typical forms for floors betw steel beams, Figs 4 to 6, vary with span and load. The forms are hung from the bottom flange of the I-beams, by "hanger bolts," A, Figs 4 and 6, % inch diam, with washers and handle nuts. These bolts secure the pieces, E, of 2 X 4 or 3 X 4, upon Fig 4. Fig 5. Figs 4, 5 and 6. Fig 6. Floor Forms. which the boards, H H H are supported by 2 X 6 or 2 X 8 ledgers, D (about 27 ins c to c, for % inch boards). Wooden blocks or sticks, B, Figs 4 and 5, are sometimes used under the ledgers to reduce their depth. Short cone blocks, C, Fig 4, are used, to keep the forms away from the lower flange of the steel beam. These remain permanently in the work. In order to promote adhesion betw the lower flanges of the I-beams and the thin mass of cone below them, the flanges are often wrapped with metal lath, before the blocks, etc, are placed. 68. Wall forms are usually made up in panels, so that they can be used several times. The panels are cleated together, and are usually about 3 X 12 ft. The panels are kept at the proper dist apart by separators, of wood or cone, and are held in place by bolts or wire ties. When wood separators are used, they must be removed just ahead of the concreting. Cone block or tube separators are sometimes used. These remain in the wall. When bolts are used that are to be later withdrawn and used again, they should be loosened by means of a wrench, about 24 hours after con- creting; otherwise it will be difficult to remove them. 69. In the YTiederholdt system of reinfd cone wall construction, the cone is deposited within small hollow tile blocks, which form the finished exterior surface, and no wooden or other temporary forms are used. The blocks are shaped to meet the requirements of the work. Tiling aad con- creting are carried up simultaneously. FORMS. 1097 70. To reduce the cost of forms fn reinfd building construction, columns, beams, slabs, etc, may be cast oil the ground, and afterward erected and placed as desired; at the sacrifice, however, of the rigidity due to the monolithic character of ordinary reinfd work. 71. Metal forms. When the structure is of small and uniform cross section, permitting the repeated use of the same forms, as in sewers, conduits, tunnels, etc, the lagging, for the wooden forms, may be of sheet metal. In tunnels and similar works, of considerable extent, and in small ornamental work, forms composed entirely of metal may.be used. 72. Both careless and over-careful alignment are to be avoided. Mr. W. J. Douglas (E N '06/Dec/20, p 646) suggests the allowance of " 3 / 8 inch departure from established lines on ' finished ' work, 2 ins on ' unfinished ' work." 73. Avoid fine detail, and detail with sharp angles. Corners should be rounded or beveled, to facilitate the flow of cone and the removal of forms, and to render the corners less liable to subsequent injury. 74. Wooden forms, within which the cone is to be placed, should be fairly watertight, smooth, and of sufficient strgth and stiffness to hold to line under the pres of the green cone. 75. The forms are usually of dimensioned timber, faced with planed boards or planks. The opening of joints betw the planks may be partially prevented by the use of matched boards or of tongued-and-grooved plank. 76. Mortar, exuding thru open joints, leaves voids or stone pockets on the surface. Hence, in forms for facework, joints should be made tight, if necessary, by the use of mortar, putty, plaster of Paris, sheathing paper or thin metal. 77. If the lumber is very dry, when fastened in place, its swelling, due to its absorption of moisture, may bulge the boards and produce unsightly work. In such cases, the boards should not be matched, but should have their edges slightly beveled, and the sharp angle of the edges of adjacent boards placed in contact. Swelling will then crush the edges rather than bulge the board. Lumber for Forms. 78. White pine is best for fine face-work, and quite essential for ornamental construction when cast in wooden forms. 79. Spruce, fir, Norway pine and the softer kinds of Southern pine are more liable to warp than white pine, but are generally stiffer and therefore better for struts and braces. SO. Partially dry lumber is usually best. Kiln dried lumber is unsuit- able, as it swells when the wet cone touches it. In very green lumber, especially Southern pine, the joints are apt to open. Green lumber is heavy, and does not hold nails well. 81. For wall-panel forms, tongued-and-grooved or bevel-edge stuff is preferable to square-edge. Tongued-and-grooved gives smoother surface and less opening of joints, than square or bevel edge, but is more expensive, owing to waste in dressing, and there is more wear at joints if the forms are used often. 82. Even for rough forms, planing on one side may save money by re- ducing the cost of cleaning after using. Studs should always be planed on one side, to bring them to size. 83. Thickness. For ordinary walls, 1 Yi ins; for heavy construction, using derricks, 2 ins. For floor panels, 1 inch boards are most used; but, in tall buildings, they become much worn, and give bad finish to under sides of floors. For sides of girders, 1 inch or 1 % inch answers, but 2 inch is better for bottoms. Col forms usually of 2 inch plank. 84. Studding is usually from 3 X 4 to 4 X 6 inch; 4X4 inch is the most useful size. Spacing, usually 2 ft for 1 inch boards, 4 ft for 1 % inch, 5 ft for 2 inch. 85. Since beams and columns sustain greater stresses than floor slabs, their forms should be left in place longer, and should therefore be indepen- dent of the slab forms. 86. Sides of beam forms should be clamped or wedged together, to pre- 1098 CONCRETE. vent their springing away from the bottom boards, under the pressure of the cone. 87. Hardwood wedges, at tops and bottoms of struts facilitate the setting and removing of the struts, and testing for deflection. 88. I.iu lit Joists (say 2 X 8 or 2 X 10), with frequent shores, are prefer- able to heavier sizes, difficult to handle. Strength of Forms. 89. The strength, required for the forms, may be estimated, where wet cone is used, by assuming the pres of the cone as equal to that of a liquid weighing about 150 Ibs per cu ft.* If dry and hard-rammed cone be used, the wedging of the stone, due to the tamping, will considerably increase the pressure. 90. Permissible loads, in Ibs, on wooden struts for floor construc- tion. Unsupported length, ft Cross section of strut, inches 3 X 4 = 12 4 X 4 = 16 6 X 6 = 36 8 X 8 = 64 14. per sq in total per sq in 7OO total 1 1 OflfJ per sq in QOO total Q94.OO per sq in 1 1 no total 7O4Oft 12 600 7200 800 12800 1000 36000 1200 76800 10 700 8400 900 14400 1100 39600 1200 76800 8 850 10200 1050 16800 1200 43200 1200 76800 6 1000 12000 1200 19200 1200 43200 1200 76800 91. In timber beams, calculated for strgth, the extreme fiber stress is to be taken at 750 Ibs per sq inch. 92. Construction live load, liable to come upon cone while setting, 75 Ibs per sq ft on slabs; 50 Ibs per sq ft in figuring beam and girder forms. This includes weight of men, barrows filled with cone, and structural ma- terial piled on floor, but not piles of cem sand or stone, which should not be permitted unless specially provided for. 93. Floor forms should be based upon allowable deflection, rather than upon strength. Formula: 3 W L 3 . = bh* ~ 384 El '' 12 ' where d = deflection, ins; W = tctal load on plank or timber; L = distance, ins, between supports; E = elastic modulus of lumber used = 1,300,000 Ibs per sq inch; 7 = moment of inertia of cross section of plank or joist; b = breadth of plank or joist; h = depth of plank or joist. In the usual formula for deflection (see p 480) 1 /384 is the coeff for beams with fixed ends, while 5/384 is that for merely supported ends. Weight of cone, including reinforcemt, 154 Ibs per cub ft. (Sanford E. Thompson, Assn Am Portland Cem Mfrs, Bulletin 13, 1907.) Details of Forms. 94. Too much nailing increases the difficulty of taking the forms apart without injury. Wire nails can be pulled with less damage to the wood than can cut nails. * Mr. W. J. Douglas (E N, '06/Dec/20, p 646) assumes that the cone is a liquid of % its own weight, or 75 Ibs per cub ft. FORMS. 1099 95. Iron or steel wall ties, extending thru the wall and fastening the forma in place, are usually removed and used again, if > J4 inch in diam. If > M inch diam, they are usually allowed to remain; but, if their ends reach to the outer surface of the wall, they produce unsightly rust stains. To prevent this, the cone, surrounding their ends, is chipped out, and the rods are cut off, back from the surface. The holes, thus formed, are after- ward plugged with mortar. 96. Separators (patented by Wm. T. McCarthy, 1 Madison Ave., New York city), molded of cem mortar, in the form of hollow cylinders, and in lengths of 4 and 6 ins, encircling the bolts, are sometimes used After the bolt is withdrawn, the hole in the cyl is filled with mortar. 97. Forms are liable to disturbance by blows from the cone bucket, or by the running of machinery in contact with the forms. 98. Any cone, adhering to a form, must be removed before the form is again used. Adhesion to Forms. 99. Adhesion to forms. If the wood is new, and if the forms are thoroly wet before cone is placed, the cone, if hard, is not apt to adhere to the forms when these are removed. If the forms are to be removed before the cone is hard, they should, before concreting, be greased with material thin enough to flow and fill the grain of the wood. Crude oil, linseed oil, soft soap and other lubricating substances are used 100. New work is apt to adhere to old sticks, where cone has previously adhered, even tho this has been cleaned off. 101. Oil, applied to forms (to prevent their absorption of water or to facilitate their removal, 1 99), is apt to find its way to joints betw old and new work, and prevent the formation of a satisfactory bond. Soap and soft soap are of course harmless in this respect. Removal of Forms. 102. Premature removal of forms and props has caused many failures of cone buildings; but undue delay, in their removal, means delay in the work and increase in the number of forms reqd. 1OJ5. The French law requires that test blocks and sample beams be made for every section cast. These enable the engineer to judge intelli- gently as to the condition of the actual work. 104. Props should be removed from one beam or girder only at a time, and should be at once replaced after the forms for that beam have been removed. This permits the discovery and repair of defects. 105. The forms may be removed earlier in warm and dry than in cold and damp weather, earlier from under light than from under heavy loads, earlier with quick-setting than with slow-setting cem, and earlier with dry than with wet mixtures. See Specifications, p 1191. 106. To release the beam boxes, the posts may be supported on wedges and capped. The posts and caps should not be removed, from more than one beam at a time. After the beam boxes have been removed, the posts and caps should be replaced before removing the forms from any other beams. Or, the posts may be supported solidly, and capped with a corbel forming the bottom and supporting the side-boards of the beam boxes. The side-boards may then be removed, leaving the posts and corbels undisturbed. 107. Prying against the cone, in removing the forms, may injure it. Joints in Concrete. 108. Difficulty. In large work, the joints, betw work done on diff days or even before and after an hour's interval, are apt to give trouble, espe- cially where watertightness is reqd. 109. Causes. The difficulty appears to be due partly to a surface skin or glaze, on the surf of the hardened cone, and partly to the presence of oily or dusty materials, laitance or sawdust, betw the two surfs. Oil, used upon the forms, or saturating the clothing of the workmen, is apt to find its way to the joints. Sawdust is particularly difficult to remove. The bond is especially weak if the older surf is frozen. 73 1100 CONCRETE. 110. Remedies. Many remedies have been proposed, advertised and used, but none has been fully tested by time. See Specifications, p 1190. Cleanliness of surface and the use of wet mixtures are probably the best preventives. Water, used in scrubbing joints, should be rinsed off with clean water. A jet of live high-pres steam is very effective, removing even sawdust. Hydrochloric acid is used to advantage. Patented methods of securing bond, at joints, include the use of metallic binders, with their ends left projecting from the older surf, to bond with the newer. Another method employs a layer of prepared honey-comb slag, sprinkled over the still soft older surf; loose slag being removed after the hardening of the older surf and before the placing of the newer material. 111. Where cone is used in reinforcing and protecting old stone masonry, a stone should be removed here and there from the old masonry, and the joints cleaned out and washed. Key-bolts, with large washers on their heads, may also be driven into the face and left projecting into the con- crete. The cone should also be carried far enough down the back of the wall to prevent water from working down into the horizontal joints on the tops of the wing walls and main walls. Ramming. 112. Ramming of cone is necessary only with relatively dry mixtures. When properly done, it consolidates the mass about 5 or 6 %, rendering it less porous, and very materially stronger. For rammers, see spec'ns, p 1189. The men, using them, if standing on the cone, should wear gum boots. 113. Under water, ramming can be done only partially, and when the cone is enclosed in bags. A rake may be used gently for leveling loosely deposited cone under water, 114. Ramming should be discontinued before setting commences. Ex- ramming disturbs the homogeneity of the cone. Placing under Water. 115. Concrete may readily be deposited tinder water in the usual way of lowering it, soon after it is mixed, in a dredge bucket, or in a V-shaped box of wood or plate iron, with a lid that may be closed while the box descends. The lid, however, is often omitted. This box is so arranged that, on reaching bottom, a pin may be drawn out by a cord reaching to the surf, thus permitting one of the sloping sides to swing open below, and allow the cone to fall out. The box is then raised to be refilled. In large works the box may contain a cu yd or more, and should be suspended from a traveling crane, by which it can readily be brought over any required spot in the work. The cone may if necessary be gently leveled by a rake soon after it leaves the box. Its consistency and strgth will of course be impaired by falling thru the water from the box; and moreover it cannot be rammed under water without still greater injury. Cone has been safely deposited in the above-mentioned manner in depths of 50 ft. 116. The Tremie, sometimes used for depositing cone under water, is a box of wood or of plate iron, round or square, open at top and bottom, and of a length suited to the depth of water. It may be about 18 ins diam. Its top, which is always kept above water, is hopper-shaped, for receiving the cone more readily. It is moved laterally and vertically by a traveling crane or other device suited to the case. In commencing operations, its lower end resting on the river bottom, it is first entirely filled with cone, which (to prevent its being washed to pieces by falling through the water in the tremie) is lowered in a cylindrical tub, with a bottom somewhat like the box described in ^[ 115, which can be opened when it arrives at its proper place. When filled, the tremie is kept so by fresh cone, thrown into the hopper to supply the place of that which gradually falls out below, as the tremie is lifted a little t9 allow it to do so. The weight of the filled tremie compacts the cone as it is deposited. A tremie had better widen out down- ward to allow the cone to fall out more readily. 117. The area upon which the cone is deposited must previously be sur- rounded by some kind of inclosure, to prevent the cone from spreading beyond its proper limits; and to serve as a mold to give it its intended shape. This inclosure must be so strong that its sides may not be bulged outward by the weight of the cone. It is usually a close crib of timber or plate iron without a bottom; and will remain after the work is done. If of timber it may require an outer row of cells, to be filled with stone or gravel for sink- PLACING. 1101 ing it into place. Care must be taken to prevent the escape of the cone through open spaces under the sides of the crib or inclosure. To this end the crib may be scribed to suit the inequalities of the bottom when the latter cannot readily be leveled off. Or inside sheet piles will be better in some cases; or an outer or inner broad flap of tarpaulin may be fastened all around the lower edge of the crib, and be weighted with stone or gravel to keep it in place on the bottom. Broken stone or gravel or even earth (the last two where there is no current), heaped up outside of a weak crib, will prevent the bulging outward of its sides by the pressure of the cone. After the cone has been carried up to within some ft of low water, and leveled off, the masonry may be started upon it by means of a caisson, or by men in diving suits. Or, if the cone reaches very nearly to low water, a first deep course of stone may be laid, and the work thus brought at once above low water without any such aids. 118. Tlie concrete should extend out from 2 to 5 ft (according to the case) beyond the base of the masonry. All soft mud should be re- moved before depositing cone. 119. Bags partly filled with concrete, and merely thrown into the water, are used in certain cases. If the texture of the bags is slightly open, a portion of the cem paste oozes out, and binds the whole into a tolerably compact mass. Such bags, by the aid of divers, are employed for stop- ping leaks, underpinning, and various other purposes, that may suggest themselves. Such bags may be rammed to some extent. 120. Tarpaulin may be spread over deep seams in rock to prevent the loss 9f cone; and, m some cases, to prevent it from being washed away by springs. 121. Concrete, placed in water, should be in large batches, in order that the ratio of exposed surface to vol may be small. In running water, lead off the flow in pipes or shutes or by means of bulkheads (for which bag cone is suitable). If water is pumped out of the pit while concreting, it is apt to take cem with it. Observe the water flowing from the pump for in- dications of loss of cem. 132. Cone dock foundation on rock 14 to 19 ft below low water and covered with mud. Laid with assistance of diver. Mud washed off by jet. Rock not leveled,- Wooden forms built on rock. Spaces, under forms, filled with bags of cone. Forms held down by means of boxes loaded with broken stone, anchored, by wire cables, near bottom, to neighboring piles, and braced, at top, by cross pieces nailed to existing dock. Cone lowered, by derrick, in Yi yd bottom-dump bucket, and dumped when close to work. The only cem lost is the little which washes from top of bucket load as bucket is submerged. The work has smooth faces along the forms, and ap- pears to be perfectly homogeneous. (E R, '05/Octy21, p 468.) 123. Placing cone in 9O ft water, in shaft, to stop inrush of water at bottom of shaft. Cone fed, by hopper, into 8 inch screw-jointed wrought iron pipe, lower end stopt with wood plug and resting on bottom of shaft. When the pipe was rai&ed slightly, the plug refused to move and release cone. Pipe withdrawn, taken apart, and each section emptied. Plug, not tight, had allowed lowest section to fill with water, which disintegrated the cone, leaving, at top of lowest section, a plug_of neat cem, which pre- vented the cone, above, from pushing out the wood'pliig as intended. Expt repeated, with tight plug. Inside the 8 inch pipe was placed a 1 ^ inch pipe, by means of which the wood plug was knocked out, allowing cone to descend. Rate regulated by changing dist of foot of pipe above bottom of shaft. Mass of cone, 10 or 12 ft thick, deposited. The upper 6 or 8 ins never set; but the remainder appeared to be solid and homogeneous. (Assn C E, Cornell Univ, Trans, 1898, p 74.) 124. In a case where hollow iron piles, in clean sandy bottom, were filled with cone, some of the mortar leaked out, and formed, with the surrounding sand, masses of cone, which adhered most tenaciously to the piles; suggesting the use of hollow piles, purposely perforated, in their lower portions, with small holes, thru which grout, poured into them, at top, can escape into the sand. (Chas List, Jour Assn Engg Socs, March, 1903, Vol 30, No 3, p 124.) 125. Superior Entry, Wis. Mixer discharges into a sub-hopper, with a cut-off shute, which discharges into depositing buckets on cars under the platform. Upon reaching the work, the buckets are lowered into the sub- 1102 CONCRETE. merged molds by travelling derricks. Each bucket is provided with two canvas covers, in two pieces, quilted with sheet lead, and fastened to op- posite sides of the bucket. When in position, these pieces overlap at the middle of the buckets, completely covering the otherwise exposed cone. When the bucket has been set upon the bottom, it is tripped by a specially designed latch, from which a rope leads to the derrick man on the traveller. The canvas curtains prevent washing of the cone. A loaded bucket weighs 13,652 Ibs. Impact of loaded bucket, upon cone already laid, seems t 2 X vol cem. For cem leaving > 10 % on No. 120 sieve, ordinary sands, and agg with 35 % voids, the following proportions are given: cem sand agg (sand + agg) -v- cem 1 1.0 3.00 4.00 1 1.5 3.75 525 1 2.0 4.50 6.50 See Plain Concrete, If 22, p 1088. 18. Every particle of sand must be coated with cem, and every particle of stone with mortar, so that the stones or the sand grains do not touch. 19. To insure this result, mix by means of one of the newer types of ma- PERMEABILITY. 1105 chine, introducing first the measured quantity of water and then the cem, making a liquid grout which will run easily into the most minute voids of the sand, which, being next introduced, becomes coated in the shortest space of time. The resulting mortar is still quite liquid, and flows into all the voids of the stone. (Win. B. Fuller, Trans A S C E, Vol 51, p 135, Dec 1903.) For the use of lime, see Expt. 82 a, p 1177. 20. In making thin slabs with a cone of 2 parts cem to 5 of fine bitumi- nous ash, reinfd with poultry mesh, Mr. W. K. Hatt (Trans, A S C E, Vol 51, p 129, Dec 1903) employed a 5 % solution of ground alum, in place of one half of the gaging water, and a 7 % solution of soap in place of the other half. This strengthened and hardened the ash cone by about 50 %, and diminished its absorption by about 50 %. The soap solution alone diminished absorp- tion, but did not strengthen the cone. Sand mortar was not greatly strength- ened by the soap and alum treatmt, but its absorption was dimin- ished about 50 %. 21. If joints are inevitable, they may be first wet, and then covered with neat cem paste or 1 : 1 cem mortar, upon which the new work is to be placed before the binding course hardens. 22. The permeability of cone linings of aqueducts &c may be diminished by drilling holes thru them and forcing in grout behind them by means of grout pumps. The grout sometimes appears at many points, indicating that it is passing not only thru the cracks but also thru the body of the cone. This method was successfully used in the Torresdale filtered water conduit, Philadelphia. 23. Superficial. For plastering the inside of a covered clear water well, Mr. Edwd Cunningham used 1.25 Ibs of soft soap for each 5 buckets of water, and 3 Ibs of alum per bag of cem. The mortar was easy to handle with the trowel, but had a nauseating odor. 2 coats, not more than 0.5 inch in all. 18-inch dividing wall showed no leak when one side held 16 ft of water. The soap was made of clarified fats, and cost 7.5 cts per Ib; much too high. With 1 part cem to 2 parts sand, 6 to 9 gals of water and 12 Ibs of alum were required for each bbl of cem. (Trans, A S C E, Vol 51, pp 127-8, Dec 1903.) 24. As an external treatment, Mr. Richd H. Gaines, New York Board of Water Supply (Trans, A S C E, Vol 59, p 160, Dec 1907) found the Sylvester soap and alum process (p 928), "fairly effective, but very expensive for large work. " 25. Asphalt can be successfully applied only to dry surfaces. It becomes brittle and loses its efficiency upon oxidation; but it will often prevent leakage until the structure has become tight thru infiltration. See II 11, p 1104. 28. The cone surface must be clean, and must first be treated with a thin wash of liquid asphalt, thinned with benzine. This enters the pores of the cone, and acts as a binder. Without this, the asphalt coating will not adhere to the cone. 27. Asphalt coatings, should be made continuous, and should be pro- tected against decay, from creeping and from abrasion, by being placed between alternate layers of cone, or by being covered with brickwork or masonry. 28. Tunnels, subways and basements, below water level, have been thoroughly waterproofed by continuous layers of heavy roofing papers, well mopped with tar or asphalt, and placed between outer and inner cone walls. 29. The two basins of Queen Lane reservoir, Philadelphia, originally lined with cem cone on sandy clay puddle, and holding 383 million gals of water 30 ft deep, were re-lined with Bermudez asphalt in 1896-7. The floor received 2 inches of asphalt cone, with a thin top layer of hot liquid asphalt; the slopes, two layers of hot liquid asphalt, with burlap between them; the burlap being anchored at top by being lapped around horizontal iron or wooden bars, let into the asphalt' paving. While this work was in progress, the south basin of the Roxborough reservoir (147 million gals, 25 ft deep) was similarly lined. In the north basin, Alcatraz (California) asphalt was used, and the slopes, as well as the sides, were treated with asphalt cone. All four of these basins have since been in continuous use, without sensible leakage. C6 1106 CONCRETE. Elastic Modulus, E. See Iffl 12 and 13, p 1111. en cone is subjected to l curved throughout it stress, per unit of area 3O. When cone is subjected to compressive test, its stress-strain diagram is in general curved throughout its length; its elastic modulus, ,. . . , . , diminishing as the stress increases. . , shortening, per unit of length Strength. 31. Cone being weak in tension, and brittle, its tensile strength is usually and properly neglected: dependence is placed chiefly upon its comp strgth, and its tensile and shearing strgths are usually exprest as fractions of the comp strgth. 32. The compressive strength is preferably determined experi- mentally by means of cubic specimens. The unit comp strgth decreases when the ratio, length/side, increases, and, in similar specimens, when their dimensions increase. 33. Cone prisms, tested in endwise compression, usually fail by shearing on planes oblique to the axes of the prisms. Upon these oblique planes, the unit shear is about half the ult comp stress. 34. The strgth varies widely with the character of the cone. 35. For 12 inch cubes of Portland cem mixtures having from 6 to 18 volumes of (sand 4- agg) to 1 vol cem, Mr. Edwin Thacher deduces, from the data of Expt 18 a, the straight-line formula, S = M N X where S = ult comp strgth, Ibs per sq inch; X = No of parts of sand to 1 part cem; M and N = values as below: Age = 7 days 1 month 3 months 6 months M = 1800 3100 3820 4900 N = 200 350 460 600 Mr. Thacher holds that, for practical mixtures, "the strgth of cone de- pends principally on the strgth of the mortar, and not, to any great extent, upon the amount of stone. " In these tests, the vol of stone was always twice the vol of sand. 36. But few tests have been made to determine the tensile strength of cone. It is usually taken as approximately from one-tenth to one-eighth the comp strength, and the shearing strength as from 1.2 to 1.5 times the tensile. 37. Prof. L. J. Johnson (Jour, Assn Eng Socs, Vol 38, No 6, p 310, June, 1907) tested 25 reinfd beams, 3 ins X 9 ins X 8 ft, loaded 6 ins from each support; 19 of the beams were of 1:2:2% scaly trap; 6 of 1 : 2.5 : 5. All the beams tailed by slip of reinfmt : the 1:2:2% beams, 137 to 143 days old, successfully resisted shears of 233 to 573 Ibs per sq in; av 470; and the 1 : 2.5 : 5 beams, 488 to 750; av 628. 38. In beams, owing to the rising of the neutral axis, under loading, the ult unit fiber stress, or rupture modulus, is about 1.6 X the unit tensile strgth. Setting. 39. Setting is of course a function of the cement paste. See Mortar. We here treat of setting, as affecting the cone as a composite body. 40. Temperature. In hot weather, cone sets very much faster than in cool weather, and the load may therefore be applied sooner in hot weather; but the time required varies with the class of structure and of cone. 41. Gradual loading. Where the loading is static or gradually increased, the time may be shorter than where the load is applied suddenly or is sub- ject to impact. 42. "As a general rule, bridge abutments and piers of Portland cem cone should be allowed to set at least a month before using, if built during ordinary warm weather. If built during cold weather, their use should, if possible, be deferred until warm weather sets in." (W. A. Rogers, RR Gaz, 'OO/Jul/27, p 514.) BEHAVIOR. 1107 43. Steel girder spans have been placed upon Portland cem cone abut- ments without injury 2 weeks after the completion of the abuts in hot weather; but work of the same character, finished early in Dec, was found not very solid inside, early in the following March. Effects of Heat ami Cold. 44. Freezing 1 nearly always damages nat cem mortar or cone to such an extent that it must be replaced by new material. 45. With Portland cem cone, freezing suspends the setting; and hardening of the mortar, for the length of time during which the material has been frozen. The apparent loss of strgth, in frozen specimens, may often be due merely to such delay in setting. 46. While freezing seldom results in material reduction of the ult strgth of Port cem cone, yet it may produce serious results by giving the cone an apparent hardness; thus causing the premature removal of forms, or the imposition of undue loads, which may produce failure when the cone thaws out, if it had not already set sufficiently before being frozen. 47. If, soon after the mortar, thru the entire thickness of a wall, is frozen, the sun shines on one face of it, so as to soften the mortar of that face, while the mortar behind it remains hard, it is plain that the wall will be liable to settle at the heated face, and at least bend outward if it does not fall. 48. If the freezing does not take place until after the cem has taken its initial set, there is little danger. Thin work should not be done at < 28 F on a rising, or at < 32 on a falling temp. 49. A thin scale is likely to crack from the surface of cone walks or walls which have been frozen before the cem has hardened. Granolithic or troweled finish sometimes spalls up in small patches, when frozen. Protection. 50. Protection against freezing 1 is expensive and uncertain. Hence the placing of cone in freezing weather should be avoided when possible. 51. Housing" and heating* the finished work. Tents or screens may be used ; but wooden sheds are more effective. 52. Covering 1 the cone, as soon as placed, with canvas, cem bags or tar paper, or with a thick layer of sand, straw, manure, sawdust or other poor heat-conductors. Straw should be < 1 foot deep. Manure is the best, but it discolors the work. Canvas etc should be kept an inch or two away from the cone, leaving an air space. Otherwise use two layers. 53. Heating 1 the materials. Stone is frequently heated by piling it over a pipe or improvised oven, and building a fire inside; or over a coilof pipe containing numerous small holes, and then forcing steam thru the pipe. The cone must be used before the steam is condensed and frozen. Sand is heated over a long sheet i'-on stove. 54. Lowering- the freezing point of the mixing- water, by the addition of chemicals. 55. Salt is the cheapest and most commonly used material. It lowers the freezing point about 1 .5 F for each 1 % salt added to the water. A 10 % solution (12 Ibs salt per bbl of cem) reduces the freezing point to 17 F and does not injure the strgth of the cone. For 32 F, dissolve 1 Ib salt in 18 gals water; add.3 oz salt for each 3 below 32 F. (Ch of Engrs, U. S. A. Report, 1895.) Larger percentages of salt appear to weaken the cone. 5H. Calcium chloride, 15% solution, or 1.25 Ibs per gal of water, lowers the freezing point to about 20 F, and does not weaken the mortar. It rapidly absorbs moisture, and it is possible that, if ground dry with the Portland cem clinker, even to the amount of 0.5 %, it would cause the ma- terial to gather dampness. The chloride dissolves with extreme rapidity, and may be added to the mixing water. (Prof. R. C. Carpenter, Cornell Umv, Sibley Jour of Eng, Jan 1905.) 57. The major portion of a pile of sand or stone may be in condition for use altho the surface is frozen. 58. In winter, we may reduce the areas of the exposed layers of the work, by placing the 'bulkheads closer together. A day's work will then run to a greater elevation, and will necessitate the use of stronger forma. 1108 CONCRETE. 59. Mortars, placed in open air, are more or less injured, by drying instead of setting, when the temperature exceeds about 65 to 70 ; but if mixed only in small quantities at a time, and quickly laid in masonry of dampened stone, so as to be sheltered from the air, the injury is much reduced. The sand and stone should both be damp, not wet, in hot weather, and a little more water may be used in the cem paste; also, if possible, not only the mortar, while being mixed, but the masonry also, should then be shaded. Expansion. 60. In variable climates, cast iron cylinders, filled with concrete, are frequently split horizontally by unequal expansion and contraction. In such structures it is safest to consider the cylinders as mere molds for the cone; and to depend only upon the cone for sustaining the load. For expansion coeffs, see Reinforced Cone, If 9, p 1110. 61. Cracks and joints. In abutments or culverts over 60 ft long, divide the wall into sections of about 40 ft, and finish one section before be- ginning the other. Contraction will cause the joint to open, and irregular cracks thru the body of the wall will thus be ayoided. Short sections may be completed without stopping, and horizontal joints thus avoided. "Very small cracks, which, in stone masonry, would be difficult to find, show up very plainly in cone." (W. A. Rogers, R R Gaz, '00/July 6, p 461.) 62. Effect of high temperatures. During calcination of the ma- terials for Portland cem, the chemically combined water is driven off. When, in mixing, this water is returned to the material, hardening takes place; but the re-application of temperatures, sufficiently high to drive off the water again, reverses the hardening process and disintegrates the material. Chemical Effects. 63. ** Dehydration of the water of crystallization of cone probably begins at about 500 F and is completed at about 900 F"; but this cools surrounding masses, and thus increases the heat resistance of the cone. J. C.* 64. Rehydration. Briquets, kept, for 6 to 8 hours, at 1000 to 1200 F (not in contact with flame) and allowed to cool, showed practically no strgth; but 28 days immersion in water restored their strgth to that of unheated briquets. 65. Fire resistance. In quartz sand the expansion coeff is twice that of feldspar; and the expansion, in one direction, is twice tha-t in the direction perp to it. 66. At the Baltimore fire the cone, exposed to flames, was seldom dam- aged to a greater depth than H inch, altho projecting corners were at some places rounded off by flames to a radius of about 2 inches. 67. Sea water has apparently but little effect upon cone so proportioned as to secure maximum density, and thoroly mixt. Damage by sea water, reported as taking place at the water line, has probably been due, in part, to freezing. J. C.* 68. Destructiy action upon cone by electrolysis appears to be due to abnormal conditions seldom occurring in practice. J. C. 69. Green cone is injured by acids ; but first class cone, thoroly harden- ed, is appreciably affected only by strong acids which seriously injure other materials. J. C. 70. In the reclamation of arid land, where the soil is heavily charged with alkaline salts, cone, stone, brick, iron and other materials are injured under certain conditions, at ground water level. Such action can be pre- vented by the use of an insulating coating. J. C. 71. Cone properly made, and having its surface carefully finished and hardened, resists the action of petroleum and ordinary engine oils. Oila containing fat acids appear to injure cone. J. C. 72. Sulphurous and sulphuric acid g'ases, combined with moisture, cor- rode cone, especially if heated * J. C. Report of Joint Comm, A S C E, A S T M, Am Ry Eng & M \V Assn, and Assn of Am Port Cem Mfrs, '09, Jan. TESTS. 1109 Tests of Concrete in place. 73. Tests of concrete in place may be made by analysis of a core of cone, obtained with a core drill,* using chilled steel shot for cutting. The bore holes are afterward grouted.f 74. The ratio of cement to sand, in the mortar, is found by means of the amounts remaining undissolved in hydrochloric acid; sand and cem, of the kinds used, and mortar, taken from the core, being tested separately in this way. (Prof. R. L. Wales, in E N, '08 /Jan 9, p 46.) 75. The ratio of mortar to stone, in the cone, is found (1) by actual separation and by weighing the stone and the mortar separately, or (2) by ascertaining separately, and comparing, the specific gravities of the stone, the mortar, and the cone. * Made by Cyclone Drill Co., Orrville, O., including small drills, worked by hand. " f B. G. Cope, in E N, '08/Jan/9, p 41. 1110 CONCRETE. REINFORCED CONCRETE. 1. The tensile and shearing strengths of cone are low as compared with its comp strgth. Hence metal rods or shapes are embedded in cone struc- tures in those portions subject to tensile and shearing stresses, and in such positions as to take those stresses. 2. Uses. Reinfmt is used chiefly in the tension-sustaining portions of beams and girders, (including floor-slabs), cols, walls, retaining walls, dams, etc; but it is useful also in many other cases; as for preventing hair cracks in surfaces, for which purpose a light web of metal (wire mesh, expanded metal, etc) is placed a few inches back from the face; for preventing fracture due to unavoidable sudden changes in cross-section; for joining walls meet- ing at an angle and liable to settle away from each other; and in culverts, enabling them to withstand hpr tension due to the outward pressure of the embankment. For this purpose old chains may be used, or light rails, with bolts driven thru the bolt-holes, to increase adhesion. 3. Safety. Modern reinfd cone buildings are practically monolithic, and therefore more rigid than skeleton steel construction. 4. On the other hand, in the steel building, the details are more accurately worked out, and the work is usually erected by skilled men, often employed by the steel mfrs; so that there is but little chance of damage to the material in erection; whereas, in reinfd cone work, the best material may be injured in the using, and the work thus rendered unsafe. 5. Good cone protects imbedded steel from corrosion, both above and below fresh or sea water level; but water may penetrate porous cone and corrode the metal. Cone laid very dry is apt to be porous. 6. The steel, used in reinfg cone, has its ult strgth usually betw 50,000 and 70,000 Ibs per sq inch, and its elastic limit between 25,000 and 35,000 Ibs per sq inch, but cold working may raise the elastic limit to 40,000 or 50,000 Ibs per sq inch. ' ' Deformed " bars are often rolled of steel with much higher elastic limit (50,000 to 65,000 Ibs per sq in claimed) for the sake of economy of steel; but see Bar Reinforcement, pp 1128, etc. As in rolled iron and steel in general, the elastic modulus may be taken as averaging approximately 30,000,000 Ibs per sq inch. See U 11. 7. Concrete. In general the necessity of working the cone around the reinfg bars requires that the agg for the cone in reinfd work shall be smaller than would be permissible in unreinfd mass work; and the vital importance of adhesion requires that all the materials for the cone shall be of the best, and the mortar not too lean or too dry. Expansion, Contraction, Etc. 8. The shrinkage of cone, while setting in air, produces comp stress in the reinfmt and tensile stress in the cone itself. Setting under water, the expansion of the cone produces the opposite effects. 9. The linear expansion coefficient, a, of a material, is that fraction of its original length which a bar of it gains or loses for each degree of change in its temp. Approximately: Per degree, Centigrade Fahrenheit Insteel 10,000 a = 0.117 0.065 In concrete 10,000 a = 0.108 0.060* 10. The large number of reinfd cone structures which have been exposed, for years, to wide extremes of temp, without injury thru difference in ex- pansion, confirms the results of experiments, quoted above, as indicating thaf the diff, betw the expansion coefficients of the two materials, is negli- gible. Elastic Modulus. 11. The elastic modulus, E s , of rolled iron and steel, of all kinds (p 460,) is remarkably uniform and constant, ranging ordinarily betw 27 and 31 (av, say 30) millions of Ibs per sq inch = approx 1.9 to 2.2 (av, say 2.1 ) millions of kgs per sq cm. *W D. Pence, 1:2:4 cone, Jour Westn Soc of Engrs, 1901, Vol. 6, p 549, 10.000 a = 0.055 Fahr, results nearly uniform. Columbia Univ, 1:3:6 cone, 10,000 a = about 0.065 Fahr. REINFORCED CONCRETE. 1111 12. On the contrary, the clastic modulus, E C , of concrete varies widely, not only as betw diff mixtures differently manipulated, and betw diff specimens made under like conditions from like materials, but in one and the same specimen under diff intensities of loading; so that, in stating the results of expts, it is usual to specify the range of unit stress within which the observations were made. 13. In stone concrete, E C ranges from 1.5 to 4 (av, say 3) million Ibs per sq inch, = 0.1 to 0.28 (av, say 0.21) million kgs per sq cm. See Expt 81 a, p 1172. In cinder cone, E C is ordinarily from 20 to 50 % less than in stone cone. See If 30, p 1106. 14. The ratio, 11 (sometimes called r and R), = E s /E c ,betw the elas- tic moduli of steel and of cone respectively, is usually taken betw 10 and 15 for stone cone, with higher values for cinder cone. See Specifications, If 107, p 1195. Owing to the variability of E C (see If 12), it cannot be a- constant quantity, even during the range of a single experiment carried from zero load to rupture. 15. The ratio, n, is, however, of constant and important use in all cal- culations respecting the mutual behavior of cone and steel. 16. Considered experiments (Expt 16 a, p 1146) seemed to show that cone, when reinfd (being constrained, by its adhesion to the steel, to share in its movemts), actually underwent, without fracture, far greater elonga- tions than were possible in unreinfd cone; but later expts (36, 38, 81 e, 81 f ), in which the cone surface was more closely observed, have indicated that the supposed elongation of the cone was in fact due to the formation of cracks which had before escaped observation. If the adhesion, betw the cone and the steel, is uniform, the cracking must be evenly distributed over the area of contact, and the cracks must therefore be very numerous and very fine, probably so fine as not to endanger the materials thru the percolation of water. Adhesion. See U 58, p 1126. 17. With rich and wet mixtures, such as are used in reinfd con- struction, the cem adheres very closely to the steel. 18. After the adhesion proper has been overcome, the removal of the steel from the cone is still opposed by friction betw the two. 19. Upon the ability of this adhesion and friction to resist the forces tend- ing to overcome them, depends of course the safety of the structure. 20. Both adhesion and friction, and particularly the friction, are greatly affected by the character of the cone and by its behavior under stress and under temp changes, by the method of testing, etc. 21. In direct tests for adhesion, whether the steel is pulled or pushed, the cone is always under comp, which causes some lateral expan- sion of the cone, and therefore increased pressure upon the reimfmt. Hence, the adhesion may be found higher than (other things equal) in beams, where this condition does not obtain. 22. On the other hand, where the hor reinfg bars, in a beam, are bent upward, near the ends, and pass up into the region of compression and (as is often the case) to a point over the support, the high pressures upon the bar, in those portions, may give it greater adhesion, as a whole, than could be the case with a straight bar under direct test. 23. With great lengths of imbedment, the stretch, in the steel, under high tensile stresses, may be such as to contract the steel laterally, sufficiently to reduce adhesion. Hence, tests where the steel is pushed into the cone, show higher adhesions. 24. Ultimate adhesion. In general, expts (see Expts 64 a, b) give, as the ultimate adhesion of good cone to plain round rods, from 200 to 300 Ibs per sq inch of contact surface. With smooth round rods, in a beam, Kleinlogel (Beton und Eisen, 1904, pp 227 et seq) obtained 560 Ibs per sq inch. The conditions of practice generally differ greatly from those obtaining in the laboratory. 25. Working bond stress. In beams subject to shock, about 50 Ibs per sq inch; for quiet loading, about double this is sometimes allowed. See Specifications, HH 113-115. 1112 CONCRETE. REINFORCED CONCRETE COLUMN'S. 1. A concrete column usually has longitudinal steel rods embedded, near the circumference, thruout its length. If there is no deflection, and no slip between the concrete and the steel, the two materials must shorten equally under load. Hence (p. 458, Eq (3) ) if L = original length, / = change of length, a g and a c = cross section areas; s s ands c = unit stresses, E g and E C = elastic moduli, of steel and of cone, respectively; we have 8 S = E s l/L; 8( . = E e l/L; ........................................................ (1) and, since l/L is necessarily the same for both materials, V*c = E t /E c = n > s s = s c n '< ...................................................... (2) and total stress in steel = a g s s = a g s n .................................... (3) " cone = a c s .................................................... (4) (6) c -c s ..................................... 2. Example. A square cone col 16 ins X 16 ins, 12 ft long has, em- bedded in each corner, a round steel rod 1 inch diam; cross section area of each rod = 0.785 sq inch. Permissible unit comp stress, s c , on concrete, = 500 Ibs per sq inch. Required the load which may be carried by the col. Here Area, a s , of steel = 4 X 0.785 = 3.14 sq ins; Area, a c , of cone = 16 X 16 3.14 = 253 sq ins; E s = 30,000,000 Ibs per sq inch; E c = 2,500,000 Ibs " " " ; n = E S /E C = 12; Total stress taken by cone = a c s c = 253 X 500 = 126,500 Ibs " steel = a s s c n = 3.14 X 500 X 12 = 18,840 Ibs " column .................................................... 145,340 Ibs f 3. Here the steel takes 100 X 18,840 -* 145,340 = about 13 % of the entire load, a safe proportion. This proportion should not exceed 20 %, or, i at most 30 %. 4. A convenient rule is to count each sq inch of steel, in cols, as worth n sq ins of concrete. 5. Conservative designers load cone cols approximately as follows: Mixture Length 1 : 1.5:3 1:2:4 1 : 2.5 : 5 1:3:6 diam p = P/a = Load, in Ibs per sq inch. < 12 ...................................... 600 500 350 350 12 to 18 ............................... 550 450 300 300 6. Longitudinal reinfg rods or bars are usually placed symmet- rically near the outside of the cone, and are covered by from 1% to 2 inches of cone. The rods should be tied together, by smaller rods or by wires, at in- tervals not exceeding the diam of the col. 7. Specifications usually require that the aggregrate cross-section area of compression rods shall not exceed from 2 to 3 % of the cross- section area of the col. 8. In buildings of say three or four stories, the rods of each sec- tion are bent in, near their tops, to form a cylinder, 18 or 20 ins high, of smaller diam than the main cyl below; and the section next above fits down over this portion, so that the two sections overlap the length of the reduced portion. 9. Owing to their much greater cross-section areas, and to the lower unit stresses in their materials, reinfd cone cols are much less liable to failure by deflection than are steel cols. REINFORCED COLUMNS. 1113 10. For ultimate loads on longitudinally reinforced con- crete columns liable to deflection, we have the Rankine formula: -T- -r+irsi (8) where P = ult total load on col; a = cross section area of col; p = P /a = ult unit load on col; 8 = ult comp unit strgth of cone cubes; K = L/r = length/least radius of gyration; Prof. Morsch gives m = 0.0001. Eisenbetonbau, '08, p 73. Hooped Columns. 11. Columns reinforced with hoops (or spirals) of steel, or with web reinforcement bent into cylindrical form, show high ult strgths and are largely used; but they undergo considerable deformation before the strgth of the hoops is developed; the hoops acting much like a steel cylinder, filled with sand, such cylinders being unable to act until the sand is com- pressed. 12. Expts at Watertown (Tests of Metals, 1905) show that, when the col is subjected to loads of from 100 to 1000 Ibs per sq inch, the unit lateral de- formation is less than one-fourth the unit longitudinal deformation. Thus, if the col shortened 0.0004 of its length, its diam increased less than 0.0001 of its original dimension. 13. From tests at the Univ of Illinois (Am Soc Testg Matls, Procs, 1907, p 382) Prof. A. N. Talbot derives the following formulas for the ult strgths of hooped cylindrical cone cols, 1:2:4, wet mixture; av age, 60 days; cols 12 ins diam, 10 ft long. Covering, over the hoops, generally < % inch. Hoops, 1 inch wide, gage Nos 8, 12, 16, electrically welded, spaced generally 2 ins c. to c. Let p = ult strgth of col, Ibs per sq inch; c = ratio of hooping to cone core; 1600 = comp strgth of cone, Ibs per sq inch. Then, For mild steel, p = 1600 + 65,000 c ; (9) " higher " p = 1600 + 100,000 c ...' (10) 1-4. Assuming that the ult unit stress, in tongitudinal col reinfmt, is 25 times that in the cone, the hooping gave additional ult strgth from 2 to 4 times that given by longitudinal reinfmt. 15. M. Considered expts (Genie Civil, Nov 1902), with spirally reinforcedN cone cols, indicate that the bars, forming the hoops, should have a diam of ap- \ proximately 1/40 of the diam of the col; that the pitch of the spirals (dis- I tance between hoops) should be from K to % the diam of the col; and I that the steel, in the hoops or spirals, adds, to the ult resistance of the col, I 2.4 times as much as the same weight of metal used as longitudinal reinfg. I He gives the formula Ultimate total load on col = 1.5a c c + s e (a + 2.4 A) (11) where a c = cross section area of col inside of spiral; c = ult comp unit strgth of plain cone in short blocks; s e = elastic limit of steel; a = cross section area of existing longitudinal reinfmt; A = " longitudinal reinfmt of equal wt with the spiral. 1114 CONCRETE. * olinuii Footings. 16. In a column footing, the stresses are analogous to those in a floor slab resting upon a col; but, owing to the relatively limited spread of the footing, the moments and shears are heavy, requiring considerable depth. The heaviest stresses are under the edges of the col. Hor rods, in the footing, are analogous to rods near the top of a beam, over the support; i.e., they take negative moms, and some of them should be bent upward, or provided with stirrups, just beyond the edges of the col. 17. Figs 1 and 2 (T & M, pp 261, 262). Fig 1: Two series of main reinfg rods, a a', b b', crossing at right angles under the col, with diag rods, JL a' (a) 1. Column Footing. *^*-^" oo (&) Fig 2. Column Footing. d d', d'd'. Fig 2: Combined beam and slab. Side wings of slab tend to bend upward, breaking away from the beam at C and C. REINFORCED BEAMS. 1115 REINFORCED CONCRETE BEAMS. 1. Cone is ordinarily from eight to ten times as strong in comp as in ten- sion. Hence, in an unreinforced cone beam of rectangular section, under bending stresses, failure occurs on the tension side. 2. The ease with which steel can be embedded in cone, the practical equality of the expansion coeffs of the two substances, the strong adhesion between cone and steel and the practicability of supplementing this adhesion by lugs or other lateral projections from the surface of the steel, facilitate combinations in which the principal service of the cone is to resist comp, while that of the steel is to resist tension. 3. The method of manufacture of cone is such that its behavior, in a given case, is less certain than that of steel. Owing to this and to uncertainty, as to the degree of adhesion betw cone and steel, on which their united action depends, the theory of such beams is at once more complicated and less exact than that of steel beams of eco- nomical sections. In the design of reinfd cone beams, proper allowance must be made for this fact, and extreme refinement is out of place. General Theory. 4. Simple reinfd cone beam, of rectangular section, Fig. 1. Fig 1. Reinforced Concrete Beam. Theory. Fundamental assumptions. 1. Cross sections, plane before flexure, remain plane under flexure. 2. Initial stresses (from shrinkage, etc) are neglected. 3. No slipping occurs between cone and steel. Hence they deform equally. 4. The tensile resistance of the cone is neglected. 5. The elastic moduli, E s and E C , of steel and of cone respectively, and hence their ratio, n = E S /E C , remain constant. 5. Notation. Referring to Fig 1, let: b = breadth of cross section of beam, perp to the paper; d = dist from comp side of beam to cen of grav of steel; kd = " " " " " " " neutral axis; z = " " " " " ' resultant of comp forces; (1-fc) d = " " cen of steel to neutral axis; d f = yd " " " " " " resultant of comp forces = leverage of resisting couple ; ] = d'/d; E S = elastic modulus of steel; = unit elongation of steel; = unit tensile stress in steel f; = unit shortening of concrete;* = unit comp stress in concrete;*! * In the outermost' fibers on the compression side of the beam. t/ s and f c are the actual unit stresses. See H 13, p 1118. 74 1116 CONCRETE. a s = cross-section area of steel; a c = bd = cross-section area of cone above cen of steel; T = sum of tensile stresses in steel ; C = sum of comp stresses in concrete; n = E S /E C = ratio of elastic moduli of steel and cone; p = a s / a c ratio of steel area to that portion of cone area which is above cen of steel;* M g = resisting moment, based upon the max allowable value** of/. ; M c - " " ' ............. f c ; M = actual resisting moment. Then a g = p a c = p b d. Stresses, Moments, Design. 6. Figs 1 and 2 and HU 7 to 20 illustrate the relations existing between the important factors, k, j, f s , f c , p, M s , M c and M; when neither f 3 nor f c exceeds the elastic limit. When they exceed that limit, see HI 21, 22, p 1122. 7. In equilibrium, the bending moment of the load (see p 474) is balanced by the equal resisting moment of the couple composed of the two equal hor forces, T and C; these forces being the resultants respec- tively of the tensile stresses in the steel and of the compressive stressest in the cone. 8. The tensile stresses, f g , in the steel, are assumed to be uniformly distributed over its entire cross section, a g ; and their resultant, T, is there- fore taken as acting at the grav cen of the steel area;' but the compres- sive stresses, in the cone, in any cross sec, decrease uniformly}: from a max, f c , at the upper surf of the beam, to zero, at the neutral axis. Their resultant, (7, is therefore applied at a point distant kd/3 below the top of the beam, kd being the distance from top of beam to neutral axis, and d the distance from top of beam to grav cen of steel. 9. Value of "J." The lever arm, d', of the resisting couple is therefore d' = jd = d kd/3 = d (1 fc/3) ............................................. (D and we have ,- = d'/d = 1 fc/3 ...................................................................... (2) For approx values of /, see 1 12. 10. Value of "It." From assumption 1, U 4 we have e c /e s = fc/(l A;) ........................................................................... (3) From assumption 5, we have fc = e c E c-> /. - .*.- ............................................................... (4 > Hence ** e * E c = k (4a) '" /, e s E s l-k'E s n(l *)'" For equilibrium, C = T; but C = f c bkd/2 = e c E c bkd/2 ...................................................... (5) and T = f s a s = f s p b d = e g E S p bd ........................................ (6) e, E, \ k Hence, k = 2 p -^ = 2 p n - ; = l/(pn)2 + 2pn p n ............................. . ................................ (7) *See tf 15, 16, p 1118. ** See H 13, p 1118. . t Below the neutral axis, the cone is in tension, but its tensile stress is neglected. See assumption 4, If 4, p 1115. J See Uf 21, 22. Figs 2 and 3 are by Prof A. W. French, A S C E-, Trans, Vol 56, '06, pp 362, etc. REINFORCED BEAMS. 1117 2.00 steel area cohcrete area n-lQ for full curves E c I n =15 " dotted curves Steel lines plotted for n= Approximate for w= 0.25 0.50 0.75 Scale of 1OO p Fig 2. For Working Stresses. (For ultimate stresses, see Fig 3.) k = l/ (pn) 2 + 2 pn pn, j = d' / d, f m = unit stress in steel, f^, = unit stress in cone at top of beam, p = a s ja c = ratio of steel area to cone area, ,]lf c = resistg mom, based upon allowed value of / s ,/ c ,reHp, M = resistg mom, actual. ; n = E S /E C . Solid curves represent n = 10; dotted curves, n = 15 Steel lines plotted for n = 10; approx for n = 15. 1118 CONCRETE. 11. Hence the position of the neutral axis (given by k) de- pends solely upon the ratio, p, of steel area to cone area, and upon the ratio, n, of elasticity betw steel and cone. For appro x values of k, see H 12. 12. Approximate values of / and k. See Fig 2. when and we have and n = 10, p = 0.010: j = 0.88; k = 0.36: p = 0.015: j = 0.86; k = 0.42; n = 15, p = 0.010: j = 0.86; A; = 0.42; p = 0.015: j = 0.84; /k = 0.48. 13. When, as in reinfd cone, two widely diff materials are used in con- junction, it usually happens that, owing to the impracticability of always giving, to each, its ideal cross-sec area, one or the other is un- avoidably and uneconomically subjected to less than its maxi- mum allowable stress. Thus, with a given value of p = a s /a c , if we load the beam until either f g or f c reaches its max allowable limit, the other (f c or f g respectively) will usually remain below its max allowable limit. See If 19 /. Let F S and F C = respectively the max allowable values of t' m and l' c . 14. Moments. For resistg moms, based upon the max allowable values, Fg and F C , of f g and f c respectively, we have: M g = Td' = F s a s j d = F g pjbd* (8) M c = C d' = C j d = F c b k d j d/2 = F C k j b d 2 /2 (9) For usual values, we may take (see H 12): j - %; k = %, k j = y z . Hence, approx, M s = 7 F g a g d/8; M c = F c b d V6. But the actual resisting; mom. M, of the sec, in any given case, can of course have but one value; and this is the less of the two values, M s and M . Since j b d 2 is common to both these values, M is determined by whether F g p or F C k/2 is the greater. 15. Relation between f s , f c and p. Since C = T,orf c bk d/2 = f s p b d, we have: '=!! ' --''': " - "27, (10> From Eq (4a) we have: Hence k andp = */,/2/. = -J^L_ -- f , x (11) i ( Usually, p ranges from 0.010 to 0.015. It is seldom < 0.005 or 16. Note that f g , f c and p cannot be arbitrarily selected. Given any two of them, the third depends upon the two so given. 17. Value of M/bd 2 . Let F g and F C be the max allowable values of the unit stresses, f g and f c , in steel and in cone respectively. Then, from eqs (8) and (9), II 14, we have (Fig 2, lower portion): M g /bd 2 = F s pj = F g p(l fc/3); (nearly straight lines, for steel) (12) M c /bd 2 = F c k j/2 = F c k (1 fe/3)/2; (curved lines, for cone) (13) REINFORCED BEAMS. 1119 The dotted and solid curved lines, for cone, represent n = 15 and n = 10, respectively. The nearly straight lines, for steel, are plotted for n = 10, but are sufficiently approx also for n = 15. 18. The upper portion of Fig 2 gives values of k = y 2 p n + (p n)* p n, (see f 10) and of j = 1 fc/3 = d'/d, corresponding to given values of p, for n = 10 and n = 15. Note that j varies but slightly with p. Examples. I. Investigation. Required the resisting moments* M s , M C and M. 19 a. Given a rectangular reinfd cone beam: 6 = 8*; d = 20"; a c = bd = 8 X 20 = 160 sq ins; n = E t /E c = 15. Let F g = 16,000, and F C = 500 Ibs per sq inch, be the max allowable values of the unit stresses, f s and f c , in steel and in cone respectively; and let P be the value of p based upon these max allowable stresses. F 8 Then F 8 /F C = 32; ^r + 1 = 3.133; and, from Eq (11), U 15, we have: P t 32->rll33 - - 04987 ' as given by the intersection, in Fig 2, of radial line, for f g = 16,000, with dotted curve for f c = 500. 19 b. (Case 1) Reinforced with two round rods, %" diam; a s => 2 . JT 0.375 2 = 0.884 sq ins; p = a g /a c = 0.884/160 = 0.005525 > P; pn = 15 X 0.0055 = 0.0825; k = l/(jm)2 + 2 pn pn + 0.1650 0.0825 = 0.3322; d' = d j = d (1 fc/3) = 20 (1 0.1107) = 20 X 0.89 = 17.8 ins; C = F c b k d/2 = 500 X 8 X 0.3322 X 10 = 13,288 Ibs; M c = Cd' = 13,288 X 17.8 = 236,526 inch-lbs; T = F 9 a s = 16,000 X 0.884 = 14,144 Ibs; M g = Td' = 14,144 X 17.8 = 251,763 inch-lbs; M = M c = 236,526 " " . Notice that where, as in this case and in Case" 2, P < jp, the mom, M c , based upon the max allowable stress, F c in the cone, is the actual mom, M. Where P > p, M S is the actual mom. 19 c. By Fig 2. The intersection of the vert line, on 100 p = 0.55, with radial line for f g = 16,000 Ibs per sq inch, gives M s /bd 2 = 78.7; and M, = 78.7 6 rf2 = 78.7 X 8 X 20 2 = 251,840 inch-lbs; but the intersection of vert line on 100 p = 0.55, with dotted curve (n = 15) for f c = 500 Ibs per sq inch, gives M c /bd 2 = 74; and M = M C = 74 bd- = 74 X 8 X 20 = 236,800 inch-lbs. 1120 CONCRETE. 19 d. (Case 2) Reinforced with 3 round rods, 1" diam; a s = 37T0.5 2 = 2.356 sq ins; p = a s /a c = 2.356/160 = 0.01473 > P; pn = 15 X 0.01473 = 0.2209; k = i/ Tpn) 2 + 2 pn pn .= I/ 0.22 2 + 0.44 0.22 = 0.48; d f = rf/ = d (1 Jfc/3) = 20 (1 0.16) = 20 X 0.84 - 16.8; C = F e bkd/2 = 500 X 8 X 0.48 X 10 = 19,200 Iba; jjf c = Cd' = 19,200 X 16.8 = 322,560 inch-lbs; T = F s a s = 16,000 X 2.356 = 37,696 Ibs; M s = Td' = 37,696 X 16.8 = 633,293 inch-lbs; M = M c = 322,560 " " . 19 e. By Fig 2. The intersection of the vert line on 100 p = 1.473, with radial line for/ g = 16,000 Ibs per sq inch, would give (on a sufficiently accurate diagram) M,/bd 2 = 198; and M S = 198 6 d 2 = 198 X 8 X 20 2 = 633,600 inch-lbs; but the intersection of vert line on 100 p = 1.473, with dotted curve (n = 15) for f c = 500 Ibs per sq inch, gives M c /bd 2 = 101; and M = M C = 101 6 d 2 = 101 X 8 X 20 2 = 323,200 inch-lbs. 19 f. It will be noticed that/in these cases, an increase of 166.5 %, in the amt of steel, has increased the resisting- mom (which still depends upon the cone) by less than 38 %; and the steel, in Case 2, is stressed to only about 8,000 Ibs per sq inch or half the max allowable stress (intersection of vert for 100 p = 1.473, with dotted curve f or / = 500, is nearly intersected by radial line for f s = 8,000). See U 13. 19 g. In both cases, (1) and (2), the intersection of radial line for f s = F s = 16,000, with dotted curve for f c = F C = 500, would give (on a sum- ciently accurate diagram) p = P = 0.004987; M/bd* = 71.5, and M = 71.5 bd 2 = 228,800 inch-lbs, the actual mom, for the given b and d, in the ideal case where f s and f c = respectively F S and F C = 16,000 and 500. II. Design. 20 a. Conversely, given the bending* moment, 230,500 inch-lbs; F 3 = 16,000; F c = 500 Ibs per sq inch; whence P = 0.004987, as before. Required b and d. Let K and J = the values of k and of j respectively, corresponding to Here we have Pn = 15 X 0.004987 = 0.075; K = (Pn) 2 + 2Pn Pn = l/0.075 2 + 0.150 0.075 = 0.3193; J = 1 A'/3 = 1 0.1064 = 0.8936; M 2 M 2 X 236,500 ,. F S PJ F c KJ 500 X 0.3193 X 0.8963 2O b. An infinite number of section areas, bd, giving the same resisting moment, M, may be found from bd 2 . 20 c. Thus, in the example of H 20 a, with bd 2 == 3315, we may have b d 2 d 6 552 23.5 8 414 20.3 10 331 18.2 etc, etc. REINFORCED BEAMS. 1121 0.25 Scale of 1OO jp 0.75 1.00 1.26 1.50 1.75 2.00 0.25 0.50 0.75 Scale of 1OO p Fig- 3. For Ultimate Stresses. ' l.CJ (For allowable stresses, see Fig 2.) P n ' * = d> I d > f g = unit stress in stoel, f,. = unit stress in cone at top of beam, p = s / c = ratio <;f steel area to cone area, C = resiatg mom, based upon max allowed value of f s , f c resp, M = resistg mom, actual. n = -^ s /-^ c Solid curves represent n = 10; dotted curves, n = 15. Steel lines for n = 10; approx for n = 15. C7 1122 CONCRETE. 20 d. It can be shown (T & M, pp 175-6) that, with given M, given unit stresses, and given unit prices, the cost .of a reinfd cone beam, per unit of length, varies inversely as d, directly as V b, and directly as $ b/d . Hence, for a given bd, the deeper the beam, the less is the cost; but practical considerations (such as practical limits to reduction of b, requirements as to head room, etc) often limit the extent to which this economy can be carried in practice. 21. Within the limit of allowable working stresses, Fig 2, the stresses and deformations, in the several fibers, are taken (assumption 1, H 4) as proportional to the dists of the fibers from the neutral axis, as repre- sented by the shaded triangle in the small figure above the diagrams (said triangle representing approx the lower portion of the parabolic area shown in Fig 3); and we have, Eq (7), t 10, It = V (pn) 2 + 2 pn pn. 22. For stresses exceeding; the allowable workg stresses, up to the ult, Fig 3, assumption 1 is inadmissible, we must employ the entire parabolic area, its vertex corresponding with the ult comp strgth of the cone; and we have k = l/(3pn/2)2 + 3pn 3pn/2 (14) Fig 3 gives values of j, k and M /b d 2 , for ult values of f s and f f . 23. Note that, for steel stresses, f s , not exceeding the usual elastic limit, and with f c ultimate < 2000 Ibs per sq inch, the ult resistg mom in- creases directly with the amount of rciiifmt tintil this reaches 2 % or over. Thus, Fig 3, with f s = 30,000 Ibs per sq inch, f c ult < 2000, and p = to 2 %, we have M /bd ~ = approx 25,000 p. Tee Sections. 2-1. Tee sections. Fig 4. b = flange width; 6' = stem width; I = flange thickness; d = depth from top of flange to cen of steel; k d = depth of neut axis; d f j d = leverage of T and (7. X-6-K i i Fig 4. Reinforced Tee Section. Theory. 25. When the tops of rectangular beams are connected by slabs, the whole being placed at one time and properly bonded, all or a part of the slab may be considered as a compression flange, in some respects similar to those, composed of angles and plates, of steel plate girders. 26. The width of slab. 6, Fig 4, which acts as flange, is sometimes taken as the distance between beams, but should not exceed % of the span of the beams. See Specifications, Ht 168-170. 27. Exact analysis of such a section is hardly possible, but it is believed that the following method is reasonable and safe. 28. Determine the ratio, p = g /a c , of steel area to cone area as tho the beam were rectangular, with depth = d, and width = the flange width. 6. With this value of p, determine the position of the neutral axis. If this falls within the slab or just at its lower side, the resisting moment is found exactly as with any rectangular section. See Case 1, U 19. 29. If the neutral axis falls below the bottom of the slab, the position of the neutral axis will not be exactly given by the equation for rectangular beams; but the difference will not be important. 30. The resisting moment is Cd' or Td' ', whichever is the less. REINFORCED BEAMS. 1123 31. Examples. (1) Neutral axis within the slab. Let 6 = 601ns; b' = Sins; d = 20 ins; t = 5 ins; max allow- able unit stresses, F C = 500, F S = 16,000 Ibs per sq in; E C = 3,000,000; E s = 30,000,000; n = 10. Let there be 3 round steel rods, diam = 1 inch. Then k = V (pn) 2 + 2 p n p n = i/Ti"0~X~OT002y a + 2 X 10 X 0.002 10 X 0.002 = 0.18; k d = 0.18 X 20 = 3.6 ins; C = F c b k d/2 = 500 X 60 X 0.18 X 20/2 = 54,000 Ibs; T = 3 X 0.785 F s = say 37,650 Ibs. Using the smaller value (that for the steel) we have : M = T d' = T (d d fc/3) = 37,650 (20 3.6/3) = 707,000 inch-lbs. (2) Neutral axis below the slab. Letb = 60 ins; b' = 10 ins; d = 30 ins; t = 4 ins; F c ,F s ,E ct E s and n as in Example (l)r 6 round steel rods, diam = 1 inch. Then 'In 5 = 0.0026, and k = 0.2; k d = 0.2 X 30 = 6. ^ n OU X oU 32. Since the comp unit stress, in the outer fibers of cone, is assumed to be F C = 500 Ibs per sq inch, the stress, at the lower side of the slab, is 500 (k d t)/k d = 500 X 2/6 = 167; and the average stress, in the slab, is 5 + 1( = 333 Ibs per sq in. 33. The 2 inches of stem, which lie between the neutral axis and the lower side of the slab, exert some comp resistance, but this is neglected, with a small error on the safe side. 34. The position of the center of gravity of the compressive forces in the slab may be found as for a trapezoid; but it is usual, safe, and sufficiently approximate, to assume that it is at the cen of the slab, or, in this example, at a distance of d t/2 = 30 2 = 28 ins above the cen of the steel. The mom of these forces is then M C = 333 X 60 X 4 X 28 = 2,238,000 inch-lbs; but the moment of the tensile resistance of the steel is only M s = 6 X 0.785 X 16,000 X 28 = 2,110,000 inch-lbs; and this mom, being the less of the two, is to be taken as the actual mom, M. Shear. 35. Shear. In addition to the hor stresses, resisted by compression in the cone and by tension in the longitudinal steel reinfmt, the vertical shear- ing stresses require attention in relatively deep beams under heavy loads. 36. For the total shear, V, in any vert section, distant x from a support, we have : V = R W ............................................ (15) where R = upward reaction at the support; W = the total of any loads in the distance, x. 37. The vert shear is sometimes provided for by using a large safety factor with the ult shearing strgth of cone, which is usually taken at from 500 to 800 Ibs per sq inch, while the working shearing stress is often restricted to from 30 to 50 Ibs per sq inch. But see Stirrups, U1[ 38, etc. 1124 CONCRETE. Shear Reinforcement. Stirrups. 38. Shear Reinforcement. Where the loading produces a shear- ing stress exceeding the limit assumed for plain cone, the beam is often reinfd by vert stirrups, which consist of rods, bent into the shape of a letter U, and passing under the hor bars and up to near the top of the beam; or, in the case of Tee beams (Fig 4), into the slab. 39. The distance between stirrups is sometimes made such that, within a hor length = d', there shall be an aggregate sectional area of vert steel bars sufficient to carry the vert shear by means of the permissible unit tension in the steel. 40. Example. Consider the T beam of example (1) ^[31, Fig 4; V = 8 ins; b = 60 ins; d = 20 ins; k = 0.18; d' = 20 k d/3 = 20 1.2 = 18.8; safe mom of resistce, M = 707,000 inch-lbs. Let span L = 20 ft = 240 ins. Then, foi a uniform load, we have W = 8 M/L = 8 X 707,000/240 = 23,600 Ibs. Shear at ends = W/2 = 11,800 Ibs. With safe unit shearing stress = 50 Ibs per sq inch, we have safe shear resistance of plain cone in section = 50 b' d' = 50 X 8 X 18.8 = 7,5T)0 Ibs Under uniform load, this shear occurs at a dist, from the ends, (11,800 7.500) L 2 X 11.800 = 3 ' 65 ft ' From this point to the center of the span, the cone is able to care for the shear, and no stirrups are there reqd. But see ^\ 41, 45. Between this point and each support, let the stirrups be of % inch round steel; aggregate cross section area of the two limbs of each stirrup = 0.22 sq inch. Allowing 16,000 Ibs per sq in, one stirrup will sustain 16,000 X 0.22 = 3,520 Ibs. The total shear, 11,800 Ibs, at the support, divided by 3520, gives 3.3 as the number of stirrups required, in 18.8 ins of length of beam; or the spacing 1 , next'to the ends, should be ' = 5.5 ins. Let the load, W, = 23,600 Ibs, be uniformly distributed. Then, at a point 3 ft from the end, V = ^j 1 -- X 11,800 = 8260 Ibs; 8260/3520 = 2.35; and stirrup spacing- = 18.8/2.35 = 8 ins. 41. The spacing- may be made to vary uniformly betw these limits; and it would be well for the vert reinft to extend beyond the theoretical stopping point (3.6 ft from end; see H 40), by one or two stirrups spaced a foot apart. See f 45. 42. Let A = aggregate vert cross sec area of hor rods, sq ins; L = span, ft; z = dist from end of beam to stirrup, ft; S = aggregate cross section area reqd in the 2 limbs of the stirrup, sq ins. Then, when the stirrups are 1 ft apart, s _ (,_*_!) (16) (J. W. Schaub, E N, '03/Apr/16, p 348.) 43. In general, spacing betw stirrups > d'. 44. The cone, in each sec, has to act as a connecting medium between the hor and the vert reinft. It is also subjected to comp forces, in transfer- ring the shear from one stirrup to the next. The action here is complex, and an ample safety factor should be used. 45. In order to provide against excessive loadings, which may come temporarily upon the beams during construction, it is advisable to use stirrups, even where not actually required by the shearing stresses deter- mined theoretically as above for the completed structure in use. The etirrups being light, the cost of using them is principally for labor; so that if any are reqd, it is well to be liberal with them. See U 41. REINFORCED BEAMS. 1125 Unit Shear. 46. Unit shear, v. In any hor section of a beam, Fig 5, under uniform or central loading, the hor tensile or comp stresses increase from the ends, where they are zero, toward the middle of the beam, where they are a max. Hence, of any two vert plane sees, 1 and 2, the section, 2, nearer the cen of the beam, will have the greater hor stresses, s. : . V c ~^i Neutral Axis 3 Fr ' T B T, and C' > C. Let T' T - t. 50. Let there be no load on B. Then V = V.* Since the vert forces are distant by x, their moment = Vx = Vx* The mom of T' T is(T f T) d' = id'. Hence, for equilibrium, Vx = td'; or t = Vx/d' (17) 51. In a reinfd cone beam, Fig 5, we neglect the tensile strgth of the cone. Hence, the diff, 7" T = t, of tension, between sees 2 and 1, must be trans- mitted, from the steel to the neut axis, by a total shear, = t, uniform* in each hor sec; and, since the hor sec of the body, B, is 6 x, we have, for the unit shear: v = t/bx = Vx/d'bx = V/bd' = V'/bd'* .... (18) Diagonal Stresses. 52. As a matter of fact, the longitudinal tensile stresses and the vert and hor shearing stresses, combine to form, and are replaced by, diagonal stresses ; and reinfmt, against shear, is more rationally designed by deter- mining, as nearly as may be, the directions and intensities of these resultant diagonal stresses (See t 53), and so placing the reinfmt as best to resist them. 53. From "Maximum Unit Stresses in Beams," p 494 e, we have, in homogeneous beams, for the angle. A, betw the neutral axis and the resultant normal (tensile and comp) or "principal" stresses, s p , at any point: tan 2.1 = 2v/s; ........................................................................... (19) &nd, for the max stress, = s/2 0?/2) 2 (20) where v = the unit vert or hor shear, and s = the unit hor tensile or comp stress, at the given point. * If there is a load, L, upon B (as, for instance, in the case of uniform loading) we have V > V, and V V = L; and there are two couples of vert forces, with moms, respectively: Vx and (V V) x f , where x' = dist from sec 1 to gravity center of L. Here we have, for sec 1, v' = V'/b d'; and, for sec 2, v = V/b d'. 1126 CONCRETE. 54. But, neglecting the tensile strath of the cone, we have, in beams 'with tension reinfmt of straight bars, and for points betw the neutral axis and the steel, 8 = 0; whence : tan 2 A _= oo; 2 A = 90; A = 45; 8p = V & = v = V/bd' (21) 55. Hence, betw the neut axis and the steel, we should provide against tensile unit stresses, s p = V/b d\ acting in parallel directions form- ing angles of 45 with the neut axis. 56. Other things being equal, this provision is preferably made by means of rods, placed liRe the diag- tension members of a Pratt bridge truss, Figs 76, 86, 96, p 693, and forming angles of 45 with the hor. 57. Very commonly, the tension rods, at each end, in a hor dist about equal the depth of the beam, are bent upward to form an angle of 45 or thereabouts with the axis of the beams. Adhesion. Seep 1111. 58. Unit of adhesion. Let z = a given portion of the length of the beam; t = T' T = the increase, in total tension, T, in the steel, in the Igth, x; V = the total vert shear in the cross section; d' = the dist betw T and the cen of comp of the cone; U = t/x = the bond stress, per unit of x; m = the number of rods; a = the circumference of one rod = the circumferential contact area of one rod, per unit of x; u = U/m a = the bond stress, per unit of a. Then (see H 50), t d' = V x; t = V x/d'\ U = t/x = V x/d' x = V/d'\ and u = U/ma = V Id' ma (22) 59. For given values of the bond stress, U, per unit of length, and of the bond stress, u, per unit of circumferential contact area, the product, m a U /u ( = total circumferential area per unit of length) in a given case, is constant; but the cross sec area, weight and cost of the rods increase as the square of a. Hence, for a given total adhesion, numerous small rods are more economical than fewer larger rods; but there is, of course, for each case, a practical limit to this economy. Continuous beams. 60. Floor systems are usually composed of slabs and beams continuous over supports; and, if the negative bending moments over the supports (producing tension at top of beam) are amply provided for, by reinfmt near the top, and if the supports are unyielding, or exactly equal in their yielding, advantage is usually taken of the reduction in the positive bending moms (at and near cen of span) due to continuity. 61. Where floor slabs are laid continuously over the supporting beams, it is usual to assume WL/10 = wL 2 /lQ as the max bending mom, where L = span; W = total load on span; w = W/L = load per unit of L. Beams, continuous over the supports, may have a like value used in design, if the beams are amply reinfd at top and over the supports. 62. On the score of safety, it is frequently specified that beams, slabs, etc, shall be regarded as non-continuous over supports, this practice requiring us to provide, at cen of span, against greater (positive) bendg moms than if the beam were continuous over supports; but, on the other hand, few if any beams are wholly non-continuous; i e, even where the beam is supposed to be non-continuous, there are negative bendg moms over the supports, due to the width of the support and to the presence of loading upon the beam over the support. Such moms require reinfmt at top, over and near supports. 63. Hence, while it is advisable, in the case of non-continuous beams, to calculate the positive center bendg mom upon the assumption of absolute non-continuity, the condition of even non-continuous beams, over their supports, should be carefully investigated, and provision made for any aegative moms there found, REINFORCED BEAMS. 1127 64. I>ouble Reinforcement. The necessity, under certain condi- tions, of reinfg against negative, as well as against positive moments (11 62) gives rise to cases (Fig 6) where reinfmt appears near both top and bottom of the section. For brevity, that on the side which, under positive mom, is under compression, will be called "compression reinft." kd o t's/n Fig 6. Double Reinforcement. 65. In addition to the symbols of K 5, p 1115, let a s f = cross section area of comp reinft; p' = a g '/a c = a g ' /b d = steel ratio for comp reinft; f s ' = unit stress in comp reinft; C" = total stress ...... ; 311 = dist from ' to nearest face of beam; z = " " comp resultant, C + C', to nearest face of beam. 66. Then, (neglecting the slight diminution of a c by the presence of ct s ') f6r position of neutral axis : k = y 2 n (p + p' d"./d) + ri* (p + p') 2 n (p + p'); .................. (24) for position of compression resultant : fc3 d/3 + 2 p'nd" (k d"/d) (26) for arm of resisting couple : jd = d z; for fiber stresses: 6 Af*/b* f s = M/pjbd 1 * (k d"/d) (1 nf c (lk)/k ***\**m j (28) f s ' = n / c (k d"Jd)/k (29) METHOI>S OF REINFORCEMENT. 1. The commonly accepted theory of reinfd cone beams re- quires longitudinal tension reinfmt near the bottom* of the beam, and diag tension reinfmt at 45, nof only betw the hor reinfmt and the neutral axis, but extending upward into the region of compression, in order to take advantage of the superior adhesion due to the compression there. It also requires, usually, tension reinfmt near the top,* at points over or near the supports. See mi 60, etc, p 1126. * The terms "bottom" and "top" are here used as referring to a beam supported at the ends, and loaded on top, where the major portion of the bottom is in tension. In a cantilever, of course, this is reversed. 1128 CONCRETE. 2. Numerous trussed systems (p 1133) have been designed, in order to meet this requirement, and these are in extensive use where the depths of the beams are sufficient to admit them and where the loading is such as to require them. 3. Frequently, vertical st irru;>s are substituted for the diag members, or used in conjunction with them; or the trussing is effected by simply bending some or all of the hor bottom* bars upward, usually at 45 or there- abouts. 4. Under light loading, the truss feature is often omitted, and the reinfmt consists simply of longitudinal bars near the bottom* of the beam. 5. Where the beam is both shallow and broad, as in floor slabs, the few longitudinal bars, used in the beam, are replaced (1) by numerous and comparatively slender rods, supplemented by similar or lighter rods, crc.s.s- ing them at right angles and welded or wired to them at their intersections; or (2) by webbing, such as wire cloth or "expanded metal." See 11f 34, etc. Bar Reinforcement. 6. For a given wt of metal, small bars give a greater adhesion area, and therefore a greater total adhesion, than larger bars (1f 59, p 1126); and the stresses are distributed over a larger area of cone. Besides, with small bars, a larger proportion of the metal can be brought down to the min allowable dist from the bottom* of the beam. Within certain limits, small bars are more conveniently handled than larger bars. The bars used are seldom < J4 inch or > 2 ins diam, and they usually range betw % and 1 J4 inch. In deep girders, two or more rows of small bars are usually prefer- able to one row of larger bars. 7. In vert reinfmt, before completion, the free ends of the rods project from the already imbedded mass of the work, and accidental blows, rn these exposed ends of the rods, may be transmitted to the portions ady imbedded in cone, affecting the adhesion there. In this respect also, light rods are preferable, since they are less capable of transmitting the effects of such blows. 8. High-carbon steel rods, with their high elastic limits, permit the use of smaller sections for a given number of rods and given total stress; but they are more brittle (when of inferior quality) than softer rods, and are not readily bent cold, to desired shapes. The smallness of the sections commonly used, and the protection afforded by the cone, render brittleness less objectionable in reinfd cone work than in most other work where steel is employed. 9. Since the elastic modulus, of rolled steel and iron, is nearly the same (say 30,000,000 Ibs/sq inch) for all grades, these all stretch about equally, per unit of length, under equal unit stresses; but steel with high Uts./aq, in. 60,000 50,000 ^ *&. .. i ^c 40,000 30,000 20,000 10,000 A &?' $ji& $ jf' < \ / 3 0.5 15 2 25 8 3.5 "Elongation, inches, in iooo-inches. Fig- 1. Plain and Twisted Rods. * See foot-note on previous page. REINFORCING BARS. 1129 elastic limit, by permitting the use of smaller sections and therefore higher unit stresses, renders elongation more probable, with the accom- panying cracking of the cone, and lateral contraction of the steel, which endangers the adhesion. On this account, it is sometimes specified that, where the elastic limit exceeds a certain min (say 40,000 Ibs/sq inch) deformed bars, 1JU 15 etc, shall be used. At 30,000 Ibs/sq inch, steel stretches about 0.10 per cent; at 50,000 Ibs/sq inch, about 0.17 per cent. Cold working raises the ultimate strength and the elastic limit, but slightly lowers the elastic modulus; see Fig 1, representing tests at Water- town Arsenal (Tests of Metals, 1904, p 397) on plain and cold-twisted steel bars, % inch square. Gaged lengths, 10 inches. The twisted bar had L twist in 8 inches. Similar results were shown in tests made at Watertown Arsenal, July 12, 1902, and published by Ransome Concrete Co, See 1 21. Square bars, of inferior steel, are twisted hot, and are more brittle. 10. Plain round steel bars are very generally used for reinforce- ment in America, and still more generally in Europe. Square bars also are used, but are less conveniently handled. Flat bars have been found deficient in adhesion. 11. In order to increase the resistance of plain bars to being pulled thru the cone, they are frequently bent up at right angles (or bent over at 180 so as to form a hook) at their ends. 12. "Anchorage, furnisht by short bends at a right angle, is less effective than hooks consisting of turns at 180." J. C. 13. For the same purpose, (^ 11), the bars may be threaded at their ends, and provided with steel anchor plates, secured by nuts. Such plates should be large enough and thick enough to withstand pulls due to the full tensile strength of the rods. In designing such plates, Prof. L. J. Johnson assumes a crushing strgth, in the cone, of 900 Ibs/sq inch, and a fiber stress, in the anchor plate, of 25,000 Ibs/sq inch. Several rods, side by side, pass thru a common large plate at each end, which serves, also, to hold the rods in their relative positions while the cone is being placed. Nuts, on the inside, holding the anchor plate to a firm bearing against the outside nuts, are an important provision. Room, for such plates, is usually found in a wall or column, or over a knee-bracket, etc. Otherwise, in order to give room for the anchor plate, the beam may be deepened locally, or the rods bent up, near their ends. When bent up, the rod exerts an upwd pres upon the cone, near the bend. This increases the friction, in the bent portion, and thus reduces the pull transmitted to the anchor plate. 14. "Adequate bond strgth, thruout the length of a bar, is preferable to end anchorage." J. C. 15. Also for the purpose of increasing adhesion (or rather to substitute, for it, a "mechancial bond") " deformed bars," of various shapes are used. 16. The principal claim, in favor of deformed bars, is that the " mechanical bond, " which they offer, is the sole reliance of the reinfmt, after its adhesion proper has been destroyed, as by a stress exceeding the adhesion, by infiltration of water, by concussion either during or after con- struction, or by constant and rapid alternations or reversals of loading, in service. Vert rods especially, during construction, are liable to accidental blows upon their projecting upper ends; and such blows may affect the ad- hesion of the portions already imbedded in cone. 17. On the other hand, it is pointed 9ut that innumerable struc- tures, with plain bars, have satisfactorily withstood, for years, service involving such vibration; and it is claimed that whatever advantage arises from deformation is more than offset by the slight increase of cost. Plain bars are of course free from patent claims, and they are at all times readily obtainable in the general metal market. 18. The projections, 9n the surfs of some deformed bars, may injure the cone covering unless this is of considerable thickness. 19. In studying comparative tests of plain and deformed bars, attention should be given to the richness of the cone mixture. Unless this is suffi- ciently rich to insure the complete covering of each bar with cem over its entire surf, the adhesion proper will not be fairly developed, and the pulling test will exhibit chiefly the diff in "mechanical bond," in which, of course, the deformed bars are superior. 1130 CONCRETE. 20. "Deformed bars offer a suitable means for supplying high resistance." J. C. The following deformed rods, Figs 2, are in more or less general use: (tt) Ransome cold-twisted square (6) Cold- twisted lug bar rrffmmmt (/) Diamond (Mueser) (.0) Havemeyer (h) Priddle Fig 2. Deformed Rods. 21. Ransome. (a; Square steel rods, twisted cold. Twisted either a'. mill, or (conveniently and inexpensively) on the work. REINFORCING BARS. 1131 22. Cold- twisted lug-bar. (6) Square bar, with angles rounded, to prevent the starting of cracks in the cone, twisted (old. The lugs are de- signed to resist any tendency of the bar to untwist under tension. For effect of cold working, see 1[ 9, p 1129. 23. Thacher. (r) Round rods, deformed by flattening at short intervals. Cross sec area practically constant. Changes in shape made by means of gradual curves. 24. Corrugated bars ; (rf) ordinarily of steel with yield point 50,000 Ibs/sq inch or over. Square, round and flat. 25. Cup bars, (e). 26. Diamond bar. (/) Rolled round, with two spiral projecting ribs of equal pitch and in opp directions (dividing the surface into four rows of diamond-shaped recesses) and two opp longitudinal ribs, at the points where the upper and lower rolls meet in manufacture. Cross-section area and weight = those of plain square bars of like denomination. Claims : uniform cross section area, uniform elongation, uniform distribution of bond; projecting ribs aid in resisting tension; edges rounded; no tendency to untwist under tension. 27. Havemeyer bar. (g) Square, with rounded corners and pro- jections. 28. Priddle Internal-bond Bar. (h) Flat bar, perforated and twisted, and the slit flanged, as shown. Small sizes worked cold; larger sizes, hot, A web may be formed by passing smaller bars, of same or other pattern, thru the slits. 29. The monolith bar consists of a hor tension member with separate diag links. In section, the hor member resembles a heavy rail with two heads instead of head and flange. Each link is a bar of round steel, bent over at top and thus forming two parallel diag legs, which, at bottom', are bent hor, and their hor portions, one on each side of the hor member, are gripped between its heads, which are swedged in, at those points, for the purpose. Supports. 30. It is of course of the first importance that the longitudinal rein- forcing bars be placed and kept in their proper positions. If, as finally located, they are too high, their resisting leverage, d' ', and the resistg moment of the beam, are diminished. If they are too low, they have an insufficient protective depth of cone below them. Various devices are in use for holding the bars in position. 31. Stirrups, Fig 3, act as hangers for the main rods. Plan \ (VsTVl t Air it Fig 3. Fig 4. Supports for Reinforcing Bars. Fig 6. Fig 5. 32. Light rods are sometimes held by wire supports, Fig 4, or by cone blocks, about 1.2 or 2 ins thick, Fig 5. 33. Heavier rods may be supported by clamps. Fig 6, made of pieces of %" or 1" channel iron, held together by round-headed stove bolts, W or %" diam, placed in the forms, and 6 or 8 ft apart. 75 1132 CONCRETE. "Web" Reinforcement. 34. Web reinforcement is used in broad and shallow slabs, in thin walls, in sewers and conduits, in columns, etc. 35. The simplest form consists of rods, placed at right angles, and wired or welded together at their intersections. The heavier or main rods are of course so placed as to take the greater stresses. The transverse rods hold the main rods in position during construction, and afterward distribute their tension across the intervening cone. They thus offer a mechanical bond. The mesh must be large enough to pass the particles of the agg used in making the cone. 36. Jean Moiiier, of Paris, used such webbing in the reinforcement of arches. 37. Expanded metal. Fig 7. Sheet steel, slitted and opened out into diamond-shaped panels. In sheets, 12 to 72 ins wide, 8 to 12 ft long; mesh from YJ' to 6"; metal, Stubs gage, No. 18 to No. 4. . Fig 7. Expanded Metal. 38. When slab reinforcement is furnisht in short sheets, these must overlap sufficiently to transmit the tension from one sheet to the next. The lapping uses about 10 % of the area of the metal. 39. Clinton wire lath, in rolls of 100 or 200 ft or more, of drawn steel wires, crossing at right angles, 2^ inch mesh, electrically welded and reinfd by longitudinal reinfg warp strands, 6 ins apart, and made up each of two wires cross-looped and twisted over each crossing strand; and, when desired, by transverse V-shaped stiffeners of No. 24 gage steel, fastened to the wires at intervals of about 8 ins. Furnisht plain, japanned or galvd, in 36 inch width. 40. Clinton welded wire; No 3 to No. 10 drawn steel wire, plain or galvd; mesh, 3X8, 2 X 12, 3 X 12, 4 X 12 ins. Fig 8. Rib Metal. 41. Rib metal, Fig 8; expanded from specially rolled steel plates, ribbed longitudinally. Mesh varying, by single inches, from 2 to 8 ins. Sheets up to 16 ft long. REINFORCING BARS. 1133 42. Rib lath, Fig 9. Fig 9. Rib-Lath. Trussed Reinforcement. 43. In general, trussed reinforcement is slightly more expensive than plain bar reinfmt; and, if shipped in rigid built-up units, it incurs higher freight charges and is more liable to damage en route; but it has the great advantage of holding the bars in position while the cone is being placed, and 44. In the lialin trussed bar, Fig 10, the projecting side fins are slit away, in places, from the central portion, and bent up, as shown. The same bar, inverted, is used over the supports. Cross sec at cen. Fig 1O. Kahn Bar. 45. Fig 11 shows the collapsible Economy Unit frame. Fig 11. " Economy " Collapsible Trusa Reinforcement with Structural Shapes. 46. The Melan system, invented by Joseph Melan, of Austria- Hungary, in 1892, and patented in the United States in 1893, comprises a concrete arch in which iron or steel beams are embedded. For small spans, the beams are usually rolled I-beams; while, for spans of considerable length, they usually consist of four angles latticed. 47. Where a structural shape, of considerable size, is imbedded in cone, to form a beam, so that the steel predominates and furnishes most of the strgth reqd, the cone acts chiefly as a protecting cover for the steel; and the case is hardly one of reinfmt properly so called. 1134 CONCRETE. 48. It is difficult to secure perfect filling, with cone, of the spaces under the flanges of rolled or built-up shapes. In such cases, each day's work slwuld be stopped either well above or well below the flange. Otherwise, shrinkage, under the flanges, will aggravate the difficulty. Column Reinforcement. 49. Columns are reinfd by means of vertical rods, placed near the circumf and usually wired together at intervals, or by circumferential (hooped or spiral) wrapping, or both. See Reinfd cone cols, pp 1112, etc. 50. In tall buildings, the column rods are often faced at the ends to give good bearing, and connected by loose sleeves, which keep the ends in proper contact; and an iron or steel plate is placed under the feet of the rods in the footing, to distribute the load more evenly over the cone of the foundation. 51. In Mr. C. A. P. Turner's mushroom system of columns and floors, the cols are splayed, at top, to increase their bearing area, and the floor reinfmt consists essentially of straight members (hor or nearly so) radiating from the cols, and joined, at intervals, by circular or polygonal members, which cross the radial members generally at right angles. Beams and ribs are dispensed with, and the floor is of uniform thickness. See E N, '09, Feb 18, p 178. DIRECTORY TO EXPERIMENTS. 1135 EXPERIMENT AtfD PRACTICE. Directory of Selected Results, pp 114O, etc. Words in bold-face type, preceding a semicolon, refer to one of two related matters ; words in plain type, following the semicolon, to the other one. Numerals and letters refer to the records of experiment, etc. Example. Under SANO (below), * 4 Sand, character; density of jiortar, 8c, e, 9d, 86c " refers to Experiments 8c, etc, which give informa- tion respecting the effect of (1) character of sand upon (2) density of mortar. Conversely, on p 1136, we find "Mortar, density of ; character of sand, 8c, e, 9d, 86c." CEMENT. Cement, character of ; water reqd, 61 a Portland A natural : water reqd, 4 d strgth, 14 a, 19 a abrasion, 4 g permeability, 65 a electrolysis, 75 a silica ; oil, 53 d typical mix ; 86 / age of ; soundness, 29 a SiM> Sand, fineness of ; density of sand, 2 a, 8 h, 8 J< 8k water reqd, 61 a density of mortar, 8 c, 9 d, 79 e strgth of mortar, 4 e, 8 a, 52 b, 79 e permeability of mortar, 8 d, 9 e lime reqd for waterproofg, 82 b sea water, 8 g uniformity coefficient ; 5 a grading of ; mortar, 8 e, 86 e shape of grains ; density of, sand, 8 i, 8 I, 94 a density of ; fineness of ; soundness, 29 b strgth of mortar, 4 / water reqd, 4 d quantity reqd ; agg, 79 b, d quantity used; strgth of mortar, 8 a elastic modulus, 70.5 exposure ; 39 a, b sulfuric acid in : 49 a chemical action of ; 26 a, b, c fineness, 2 a, 8 j, 8 k uniformity coeff, 5 a shape of grains, 8 i, 94 a compacting, 2 a, 8 h, 8 i, 8 k, 45 a character, 8 I mica, 87 a moisture, 2 a, 8 h, 8 I, 45 a mortar, 86 c, d voids ; spheres of uniform diam,45 6 ACCIDENTAL Clay in cement ; 4 a Clay A loam : strgth of mortar, 4 a, 34 a, 39 g, 50 6, 52 a, b, 56 a, 80 a absorption, 56 a plasticity of paste, 4 a density of paste, 4 a permeability, 4 a mortar for plastering, 4 a in cone for columns, 92 a compacting ; density of sand, 2 a, 8 h, 8 i, 8 k, 45 a fineness of sand, 8 k moisture in ; density of sand, 2 a, 8 h, 8 I . water reqd, 61 a character ; density of sand, 8 I density of mortar, 8 c, e, 9 d, 86 c strgth, 19 c, 39 g, 50 a, 52 a, 62 a absorption, 62 a impurities in ; 19 c, 52 a clay V loam in ; strgth, 4 a, 34 a, 39 g, 50 b, 52 a, fe, 56 a, 80 a permeability, 4 a absorption, 56 6 mica in ; 79 a, 87 a friction of ; 89 a percentage of ; electrolysis, 91 a abrasion, 4 g fusing point; 89 b vs screenings ; 79 a-j density, 79 c permeability, 79 h, j absorption, 55 a vs crushed limestone; 50 a IXOREDIEXTS. Clay A- alum ; permeability 80 a Mica : 79 a, 87 a fciilfuric acid: 6 a, 49 a Salt: 4 c, 19 a, 31 a , 70 g, i Fire; 41 a-e, 46 a-e, 70 a-i San Francisco, 71 a-d aggregate, 41 c, d, e gravel and broken stone, 41 c cinders, 41 e disintegration, 70 d-f strgth, 46 d, 70 d-f elastic properties, 70 c requirements, 46 e reinforced cone, 41 b, 46 c, e, 70 h COLUMNS. Columns ; clay in cone for , 92 a strgth of ; 35 a elastic modulus ; 35 a DIRECTORY TO EXPERIMENTS. 1139 Directory to Experiments, pp 1140-1183. REINFORCEMENT, METALS, Concrete, reinforced ; shear, 81 6, h stresses in , 81 g, h fire, 41 6, 46 e Reinforcement ; strgth, 81 h fire, 46 c permeability, 47 g adhesion & friction : 64 a, b, 81 d, h, 88 a plain & deformed bars, 64 a, 74 a high & medium steel, 88 a disturbance, 64 a, 76 d proportions, 64 b time, 26 d elastic limit, 88 a ADHESION, CORROSION. fatigue, 76 d exposure, 26 a, 37 a, 6, c corrosion of : 2 6, 26 a, 6 c 37 a, 6, c, 40 a, 6, 44 c, 47 L 54 a, 59 a, 6 conductivity of ; 70 i electrolysis ; 75 a, 91 a disturbance of; 47 /, 64 a, 76 d plain V deformed ; adhesion, 64 a, 74 a high V medium steel ; adhesion, 88 a percentage of ; 81 g strength of ; 81 h stirrups ; 81 h 1140 CONCRETE. Experiment and Practice* Selected Results. See Directory, pp 1135, etc. Order of arrangement. The features entering into the manufacture and behavior of concrete are so numerous, and in the reports of experiments, etc, they are unavoidably so interlaced, that it has been found impracticable to group the several items in the body of the text in satisfactory order below. Most of our "selected results" are therefore here placed approx in the order of their dates of publication, and furnisht with a directory, pp 1135 etc, by means of which any particular subject may be promptly found. The direc- tory is arranged rationally (i e, not alphabetically), and, as far as practi- cable, in the order followed in the text (pp 930-947 k, 1084-1134), referring to cement, sand, mortar, aggregate and concrete, plain and reinforced. The items, covered by any one publisht statement, are given a common number, and, under this common number, the several paragraphs are indi- cated by letters. These letters usually distinguish also betw the several features covered by the common number. Thus, under Expt 8, we have a number of conclusions reached by R. Feret: under 8 a, conclusions respecting strength of mortar as affected by proportion of cement and fineness of sand; under 8 c, conclusions respecting porosity and permeability as affected by fineness of sand and richness of mortar, etc, etc. In the directory, semicolons, in general, are used to distinguish between two different but related ideas. Thus: '"Strength; fineness of sand" and "Sand, fineness of ; strength," refer to items giving information re- specting the effect of fineness of sand upon strength of mortar or cone. 1. Bonriiceau, Annales des Fonts et Chaussees, 1863, p 181. 1 a. Expansion Coefficient. Bar iron 0.000 0123 5 per deg C; 0.000 006 86 per deg F Port cem Cone 0.00001370 0.00000760 " " " 2. John C. Trautwine, Civil Engr's Pocket Book, 1872. 2 a. Sand, density ; moisture, compacting-. Specimens. Ordinary pure sand from the seashore, both dry and moist (not wet), see table. Sand B was of much finer grain than A. C consisted of the finest grains sifted from B. Treatment. The dry sands were compacted by thoro shaking and jar- ring; the moist sands by ramming in thin layers. Results. Sand A Sand B Sand C (coarse) (finer) (finest) Dry Moist Dry Moist Dry Ibs Solid Void Ibs Ibs Solid Void Ibs Ibs. Solid Void per cu ft % % per cu ft per cu ft % % per cu ft per cu ft % % Loose 97 59 41 86 88 53.4 46.6 69 82 50 50 Compacted Increase. . . 112 15 68 9 32 9 107.5 21.5 101.6 13.6 61.6 8.2 38.4 8.2 103.5 34.5 98.5 16.5 60 10 40 10 Percent... 15.5 15.2 22 25 15.5 15.3 17.6 50 20.1 20 20 2 b. Corrosion. 10 years' trial. Dampness absolutely excluded after setting. Cements protect iron, lead, zinc, copper, brass. Plaster of Paris protects all these except ungalvanized iron. EXPERIMENT AND PRACTICE. 1141 For abbreviations, symbols and references, see p 947 1. 3 3. John Watt Saudemau. last C E, Vol. liv, 1878, p 260. 3 a. Aggregates ; density. Results Ibsper Percentage No. cub ft of voids 1. Broken limestone, mostly 3 inch 95 50.9 2. Screened gravel, from small pebbles to 2.5 inch. . Ill H 33.6 3. Equal parts of Nos. 1 and 2, well mixed 113 Y^ 34.0 4. Broken sandstone, 4 to 8 inch 74 50.0 5. " " from sand to 4 inch 92 34.0 6. Equal parts of Nos. 4 and 5, mixed 91 M 36.0 4 4. Eliot C. Clarke, A S C E Trans, Apr, '85, Vol 14, p 163. Expts for Boston Main Drainage Works. Results. 4 a. Clay. The addition of not exceeding one part of clay to 2 of cem, gave a ' ' much more dense, plastic and water-tight paste, convenient for plastering surfaces or stopping leaky joints," and, in general, had no markt effect upon the strength of Portland and natural cem. Mortars, made with sand containing 10% of loam, were of normal strgth at 6 and 12 mos, thp of only about half normal strgth up to 1 mo. Clay, in cem, is "an almost impalpable powder, with particles fine enough to fill the spaces be- tween the particles of cem." 4 b. A year's saturation in fresh or salt water, and in contact with oak, hard pine, white pine, spruce or ash, did not affect the mortars. 4 c. Salt, either in the water used for mixing, or in that in which the cem is laid, retards setting somewhat, but has no important effect upon the strength. 4 d. Consistency. Excess of water retards setting. Nat cems need more water than Port; fine-ground more than coarse; quick- setting more than slow. 4 e. The finer the sand, the less the strength. 4 f. With sand, fine-ground cems are strongest; coarse-ground are strongest neat, especially with Portlands. 4 g. Port resisted abrasion best when mixt with 2 parts sand; nat with 1 part. Resistance diminished rapidly with slight variations from these proportions. 4 h. In setting, mortars expand > 1 part in 1000. 5 5. Allen Hazen, Mass. State Board of Health, Report '92, p 550. Sharp-grained sand. 5 a. Uniformity coefficient (u. c.)p 947: <2 <3 6 to 8 Voids, per cent, approx, 45 40 30 6 6. E. Carey, Inst C E Procs, Vol 107, '92, p 55. 6 a. Sulfuric acid ; strength. Neat cem, gaged with water con- taining 5 % acid, had, at 7 days, only 27 % of the strength of neat cem gaged with water free from acid. 7 7. Dr. Wilhelm Michaelis, Inst C E Procs, Vol 107, '92, pp 372, 375. 7 a. Disintegration of porous cem in sea water shown to be due to the action of sulfuric and hydrochloric (muriatic) acids, contained in the magnesium sulfates and chlorides of sea water. These acids leave the weaker base, magnesium (which is deposited as a hydrate), and combine with the lime of the cem, expanding and disintegrating the cone. 1142 CONCRETE. For directory to Experiments, see pp 1135-9. 8. R. Feret. Annales des Fonts et Chaussees, 7e serie, Tome IV, '92. 8 a. Results. Strength of mortar increases with proportion of cem, and, in general (especially at the beginning of hardening) with size of sand. 8 to. Mortars vary widely as to porosity. Compare 9 d , 9 e. 8 c. Porosity increases 8 d. Permeability increases with fineness of sand, with coarseness of sand, with richness of mortar with richness of mortar. 8 e. Mortars made with a mixture of coarse and fine sands are less porous and less permeable than others. 8 f. The permeability of mortars subjected to continuous percola- tion of fresh or sea water, diminishes rapidly; but, in certain cases, the mortar disintegrates or cracks. 8 g. To avoid disintegration in sea water, use coarse sand and plenty of cem. Mix wet. 8 h. Density of sand; moisture and tamping-. Fig. 1. 0.500 0.04 0.08 0.12 0.16 0.400 0.300 0.000 0.500 0.400 0.300 0.000 0.04 0.08 0.12 0.16 founds of Water per pound of dry sand, Fig 1. Moisture and Tamping. M. Feret used (1) a very fine dune sand and (2) a coarser sea sand. Wm. B. Fuller, E N, '02, Jul 31, p 81, used a bank sand, (1) loose and (2) tamped. From these results, it appears that the addition of water affecvs the vol of the sand* in two opposite ways; (1) by insinuating itself betw the sand particles, thus increasing the vol for a given wt; (2) by decreasing the fric- tion between the grains, allowing them more readily to take up the positions of closest contact, and thus diminishing the vol. When only small vols of water have been added, the first of these effects seems to prevail, the bulk increasing until the vol of water reaches from 2 to 5 % of the vol of dry sand.* With more water, the lubricating effect prevails, the vol diminishing. Loose 10 20 40 50 60 70 90 100 Tamped torefusctlQ 10 20 30 40 50 60 70 80 90 Percentage of solid in given volume of sand. Fig 2. Compacting. 8 i. Shape of grain and tamping. Fig. 2. * See foot-note *, p 946. 100 EXPERIMENT AND PRACTICE. 1143 For abbreviations, symbols and references, see p 947Z. Specimens. Four materials, as follows: a. Granitic sand, rounded grains; c. Broken shells, flat grains; b. Ground quartzite, angular grains; d. Residue from 6, lamellar grains. Each of the four materials screened to the same granulometric compoai- tion, viz: c, 0.5; m, 0.3; /, 0.2.f (See p 946.) Results. See Fig. 2. S j. Effect of size of main. Fig. 3. 383 50 100 150 200 Meshes per linear decimeter. 250 Fig 1 3. Size and Density. A = Alexandre ; C = Candlot. Theoretically, the density, in a sand* or gravel,* composed of grains of uniform size, should be independent of the absolute size (f 30, p 947 6); but experimenters have obtained contradictory results, showing unimportant variations of density with size. Thus (T & T, p 170), if sand (except very fine sizes, such as pass a sieve with 74 meshes per linear inch) and broken stone, with irregular particles of approx uniform shape, be separated into portions containing particles of uniform size, these several portions will show approx equal percentages of voids. This agrees wifh R. Feret's ex- periments (T & T, pp 171 and 142), Fig 3, according to which each of the 3 sizes (coarse, medium and finef) contained 50 % voids. M. Feret's results are represented by the hor line in Fig 3. On the other hand (Fig 3) M. Candlot (Feret, Ann des Fonts et Chaussees, 1892, 2e sem) found the voids increasing continuously, and M. Alexandre (ibid) found them first increasing a-nd afterward decreasing as the size grew smaller. 8 L . Effect of sizes of grains, and shaking* or tamping. Loose sand* shows densities ranging from 0.525 to 0.610, the max density occurring when 60 % of coarse sandf is mixed with 40 % of fine sand, with- out medium sand. In sand shaken to refusal, the densities range from 0.600 to 0.793, the max density occurring with a mixture of 55 % coarse with 45 % fine; no medium. * See foot-note *, p 946. t Classification of sizes. c. Coarse 20 m. Medium 60 /. Fine 180 Retained on 60 meshes per lineal decimeter. 180 1144 CONCRETE. For Directory to Experiments, see pp 1135-9. 81. Densities of loose unscreened sands and gravels; shapes and sizes of grains; moisture. Wt of pebbles con- tained, % Mechanical Analysis of sand proper Dry sand Kg per cu M. Moist sand Mois- ture % Kg per cu M, Coarse Med. Fine Granitic rounded grains . . Schistose 1.0 25.4 6.6 0.136 0.359 0.259 0.723 0.293 0.412 0.141 0.348 0.329 1,586 1,753 1,600 0.8 1.2 1.8 1,495 1,650 1,332 9. Luigi Lniggi and Valentino C'ardi, "Esperimenti sulle Calci, etc;" Gemo Civile, Rome, '93. Porosity, permeability, etc. Safe loads. Twelve years' expts in connection with harbor works at Genoa, Italy. Results. 9 a. In mortar, voids are due partly to air adhering to particles of sand and agg, partly to evaporation of the water used in mixing. 9 b. In mortar, volume of voids may vary from 12 to 46 % of vol of mortar. 9 c. Minimum voids (5 %) in cone formed with 700 Ibs Port cem, 1 cu yd mixt sand, 1 M cu yds small gravel. 9d. Porosity increases 9 e. Permeability increases with fineness of sand; with coarseness of sand; ' richness of mortar; " poorness of mortar; greatest with neat cem. least with neat cem. Compare 8 c, 8 d. 9 f. Concrete of 1150 Ibs Port cem,*l cu yd mixt sand, 1 M cu yds small gravel, carefully mixt with just enough water (about % cu yd) to work it up, was impermeable under 40 ft head (17.3 Ibs/Q"). 9 g. Concrete of 700 Ibs Port cem, 1 cu yd mixt sand, 1 ^ cu yds small gravel, made into a hollow cyl with shell 2 1 A" thick, was impermeable under 13 ft head (5.64 Ibs/D") and barely permeable under 27 ft (11.7 lbs/D"). Similar cyls, of same mixture, without the gravel, leaked somewhat under 13 ft and easily under 27 ft. 9 Ii. Safe load in compression. In the floors of the graving docks, 1:2:3 cone of Port cem, sand and small gravel, safely carries 107 Ibs/Q" ; safety factor, 15. 10 10. r. Keller, Thonindustriezeitung '94, No. 24. 1C a. Expansion Coefficient. Temps from 16 to + 72 C + 3 to + 162 F. Gravel (20 mm) and sand, in equal parts. Mixture of sand and gravel, parts 0248 0.0000101 0.0000104 0.0000095 F... 0.000 0070 0.0000056 0.0000058 0.0000053 Proportions (1 part cem) to Coefficient, per degree C. . .0.0000126 _ -a -m r 11.' Oeo. W. Rafter, 2d Report on Genesee R Storage Project, '94. See E R, '06, Jan 27, p 109. 11 a. Concrete with hard sandstone, gave strength 50 % greater than where shale was substituted. EXPERIMENT AND PRACTICE. 1145 For abbreviations, symbols and references, see p 947*. 12 12. L,eibbrand. E R, '94, Nov 3. 12 a. Comp strength ; age. Bridge over Danube at Munder- kingen. Cone 1 : 2.5 : 5, wet. Cubes 20 cm (8"). Very thoroly mixt in an iron cylinder revolving on a hor axis and con- taining 40 steel balls weighing together 660 Ibs. Mixt 2 mins dry, 3 mins wet. Age in days 7 28 150 970 3285 (= 9 years) Comp strgth, kg/sq cm . . 202 254 332 520 570 l'ba/sq in 2870 3610 4720 7400 8100 12 b. Max existing- pressures, in bridge, 500 to 560 lbs/D". 13 13. J. Watt Sandeman, Inst C E Procs, Vol 121, '95, p 220. 13 a. "Watertight eoiierete walls (pres not stated) made with 1 part cem leaving 10 % on No. 120 sieve, 2 parts sand with 27 % voids, 4.5 " large and small gravel with > 35 % voids. 13 b. Where agg has 35 % voids, vol of mortar should be 50 % of vol of agg. 14 14. A. W. Dow, U. S. Inspector of Asphalt and Cem. Report of Engr Commsr, Dist of Columbia, '97, p 165. 14 a. Compressive strength. Specimens, 12-inch cone cubes, dry; rammed in cast iron molds; thoroly wet twice daily. The results for one year are means of five cubes ; the rest are means of two cubes. Deduct from 3 to 8 per cent, for friction of press. The materials were as follows: Cement. Portland Natural Per cent, retained on sieve of 100 meshes per linear inch, 8.5 14 Time for initial set, minutes 190 20 " hard 305 36 Tensile strength as follows, Ibs. per square inch: 1 Day. 7 Days. 1 Mo. 3 Mos. 6 Mos. 1 Year. Portland, neat 441 839 3 parts stan- dard broken quartz, 248 429 398 428 474 Natural, neat, 96 180 2 parts stan- dard broken quartz, 91 188 327 414 485 Sand used in concrete. No residue on a No. 3 sieve; 0.5 per cent, passed No. 100. Voids 44 per cent., with 4.4 per cent, water. Broken Stone. Gneiss. Of Nos. 6 and 12 (table below) 3 per cent. retained on 2.5 inch mesh; all on 1^ inch. Others, retained on 2.5 inch; nearly all on 0.1 inch. For voids, see table, below. Gravel. Clean quartz, passing a IHnch mesh, 2 per cent, passing a No. 10 mesh. Voids, 29 per cent. Water. With Portland cement, 0.09 cu. ft. ( = 5.7 Ibs.) per cu. ft. of rammed concrete; with natural cement, 0.12 cu. ft. ( = 7.5 Ibs.). For Results, see p 1146. 1146 CONCRETE. For Directory to Experiments, see pp 1135-9. Crushing Strength of 12 in. Concrete Cubes, in Ibs. per sq. in. Experiments by A. W. Dow, as above: Parts by volume; cement, 1; sand, 2; aggregate, 6. Aggregate Voids in Aggregate. Crushing Strength, Ibs. per sq. in., after No. 1 p__ Mortar, J< 1 i er Cent, of Vol. in percentage of Voids. 10 Days. 45 Days. 3 Mos. 6 Mos. 1 Year. s 2 pp o a 7 6 45.3 83.9 908 1790 2260 2510 3060 3 8 3 3 35.5 107.0 950 1850 2070 2750 * 9 4 2 37.8 100.6 2840 1 10 6 39.5 96.2 2700 6 29.3 129.1 694 1630 2680 1840 2820 ^ 12 6 45.7 83.9 1630 1530 1850 1 6 45.3 83.9 228 539 375 795 915 3 2 3 3 35.5 107.0 108 364 593 632 841 S 3 4 2 37.8 100.6 _ 915 I 4 6 39.5 96.2 800 6 29.3 129.1 87 42'l 361 344 763 15 6 6 45.7 83.9 596 829 15 15. Tests of Metals, '98, p 572. 15 a. Cinder Cone with Port cem; ult comp strength. Specimens; 12-inch cubes; water 10 to \2 1 A Ibs per cu ft of cone. Results : Proportions by volume: Cement Sand 1 1 2 2 2 2 2 2 3 3 Cinders 3 3 3 3 4 4 5 5 6 6 No. of tests Lbs/sq inch 90 39 102 38 98 30-38 90-99 29 91 16 1541 2053 1098 1634 904 1325 724 1094 529 788 16. Considerc, Genie Civil, '99. 16 a. Ductility. Specimens and results ; Cone cantilevers, 1:3, 6 cm sq, 60 cm long, tension side reinfd by 3 round iron bars 4J4 mm diam. Treatment. Loading such that bendg mom was the same for all cross sees. In one of the prisms, load increased until unit stretch = 0.002. Then loads, = 44 to 71 % of this original load, were applied 139,000 times; stress returning to each time. Results. Unit stretches, 0.000545 to 0.00125; strgth but little reduced. Similar tests of unreinfd specimens gave unit stretch, at rupture, only 0.0001 to 0.0002; the reinforcement apparently enabling the cone to endure far greater deformation than when not reinfd. But see Expts 36, 38. EXPERIMENT AND PRACTICE. 1147 For abbreviations, symbols ami references, see p 947 1. 17 17. . E. Fowler, A S C E, Trans, '99, Vol 42, p 117. 17 a. Results. Proportions, assuming that 1 bbl Portland cem = 3.8 cu ft. 34 cu yds concrete = abt 27 cu yds after ramming. Those cones, for which the vols of stone appear in bold-face type (as l.OO), have their voids filled or more than filled; while, in those printed in plain type (as 1.04), the voids are not filled and the cone is porous and deficient in strgth. Quantities in 1 cu. yard of concrete: Stone with Stone with Cement, Sand, 40 % voids, 50 % voids, Proportions Barrels cu yds cu yds cu yds 1 :2 1 :2 1 : 2 1 :3 1 :3 1 :3 1 : 4 1 :4 1 :4 3 1.77 0.51 O.87 1.05 4 1.59 0.47 O.95 1.15 5 1.39 0.42 1.04 1.26 4 1.30 0.57 O.83 l.OO 5 1.16 0.52 O.92 1.11 6 1.04 0.48 l.OO 1.20 6 1.00 0.55 0.91 1.09 7 0.92 0.51 O.97 1.17 8 0.83 0.47 1.03 1.25 The foregoing figures agreed well with the results of practice. The column for stone with 40 % voids closely represents broken limestone, which breaks into pieces of various sizes; while the column with 50 % voids represents trap rock, which breaks into pieces of more nearly uniform size. 18 18. Tests of Metals, '99. 18a. ompressive Strength O f 12" cubes of dry Portland ce- ment concrete, for Geo. A. Kimball, Chief Engr Boston El Ry Co. Specimens ; Sand. Coarse, clean, sharp. Voids, measd loose and moist, 33 %; measd after settling by saturation with water, 25 %. Stone. Conglomerate from Roxbury, Mass. Voids, measd loose, 49.5 %. 4.8 % passed 2 y/ ring, caught on 2" ring ; 76.7 % " 2" " , ' 1" " ; 18 % " 1" " , " W " ; 0.5 % " W Treatment. Mixt by hand. Water barely showed after ramming. Cubes, except those tested at 7 days, buried in wet ground until within one wk of testing. In general, 5 cubes of each mix of each brand were tested at each of the ages. Results. Ultimate eompressive strengths, Ibs/D". Each max or min is the mean of five or more tests, upon cubes made from one of the four brands of cem, and thus refers to the cem giving max or min strgth under the stated conditions. The avs are those of such results for the 4 brands. Age 1:2:4 1:3:6 1 : 6 : 12 max av min max av min max av min 7 ds 2219 1525 904 1550 1232 892 759 583 417 1 mo 2642 2440 2269 2174 2063 1816 1218 1042 873 3 mos 3123 2944 2608 2538 2432 2349 1257 1066 844 6 mos 4411 3904 3612 3170 2969 2750 1583 1313 815 For formulas, deduced from these results by E. Thacher, see II 35, p 1106. jj ____ 19. W. A. Rogers, Chic, Mil and St P Ry, Westn Soc Engrs, Jour, 1899 Jun, Vol 4, No. 3, p 262, R R Gaz, '00, June 15, p 402, July 27, p 514. 19 a. Effect of cold, and of mixing with salt water. Specimens ; comp strength of 12-inch cubes of Port and nat cem cone. 8 cubea 76 1148 CONCRETE. For Directory to Experiments, see pp 1135-9, Atlas Port, 1 cem, 3 gravel (2 sand, 1 pebbles), 4 hard crusher run lime- stone; 8 cubes Louisv nat, 1 cem, 2 gravel, 3 stone. Same as used in track elevation masonry by Chic, Mil and St P Ry. Treatment. All the cubes made by same person in molds of 1" lumber, and left in molds until broken. Results. Portland Natural Temp, F Ibs/sq in. Temp, F *lbs/sq in I cube in warm office 28 days 1 " " " " 28 '' 80 to 18 >1290t >1290t 85 to 40 300 defective 1 " outdoors* 28 " 57 to 24 902| 57 to 10 200 1 " " 28 " " 690| " 256 1 " " 28 " in office 28 ' 85 to 32 >1290t 85 to 40 376 1 " outdoors* 28 ' 57 to 24 57 to 10 in office 28 ' 85 to 32 >1290f 85 to 40 352 1 " outdoors * ** 28 " 57 to 24 , >1290t 57 to 10 237 1 " 28 " >1290t 247 19 b. Character of aggregate ; comp strength. Specimens. 12" cubes of Port cem, gravel and stone. Gravel, 2/3 coarse, sharp sand, 1 /3 pebbles from sand to 1 J^". Each result the average of 3 cubes. Age 28 days. Results. Ibs/sq in 1:3: 4.5 hard crusher-run limestone 1270 1:3: 4.5 soft screened " 1170 1 : 3 : 4.5 washed gravel % to 2 in 1050 1:4:7 soft screened limestone ' 714 1 : 4 : 3^5 } washed gravel H to 2 in j 642 19 c. I>irt in sand and aggregate ; comp strength. Specimens. "Dirty" sand and gravel contained apparently abt 10% dirt whictf had the appearance of containing a large amount of iron." Results. With sand, tensile, 90 days, Ibs/Q" Clean 457 Dirty 627 Dirtier 515 1 :2 492 541 514 1 :3 349 430 396 20 With gravel, comp, 12" cubes, 28 days, Ibs/Cf 1:2:5 1 : 2.5 : 5 1097 838 988 928 1020 20. Edwin Thacher, E N, '99, Sep 21. 20 a. "Several brands of Port cem were improved, in tensile strength, by a delay of from 1 to 4 hrs betw mixing and laying." Ransome. 21 21. <5eo. W. Rafter, A S C E, Trans, Dec '99, Vol 42, p 104. 21 a. Volume ; consistency, richness and proportion of mortar. Specimens : 544 12" cubes, broken on the U. S. Govt testing machine at Watertown, Mass. Port cem; sand, 86.5 to 93.5 Ibs/cu ft; agg, broken stone. Cubes abt 2 years old. "Dry," only a little more moist than damp earth; "Plastic," ordinary consistency used by masons; "Excess," under moderate ramming the cone quaked like liver. * During the first part of the 28 days, temp fell to 10 and 20 F ; afterward, thawing during day, freezing at night. t Flaked slightly. Strgths exceeded capacity (185,000 Ibs) of machine j Cold believed to have retarded setting. ** Mixed with salt water, 1 pint salt to 10 qts water. EXPERIMENT AND PRACTICE. 1149 For abbreviations, symbols and references, see p 947 1. S = vol of sand in mortar to 1 vol cem; M = " " mortar " cone " 1 " " A = ' " agg " " " 1 ' C = ' " cone made with 1 ' Results. Volume ! Mortar = 33 % agg Mortar = 40 % agg 1 Proportions Shrkg Proportions Shrkg O S M A C t 8 M A C t D. 1 1.57 4.74 4.30 9.3 1 1.64 4.10 3.82 6.8 P. 1 1.83 5.51 5.01 9.1 1 1.66 4.14 3.82 7.7 E. 1 1.70 5.11 4.64 9.2 1 1.70 4.24 3.97 6.4 D. 2 2.42 7.29 6.74 7.4 2 2.44 6.12 5.89 3.8 P. 2 2.45 7.28 6.62 9.1 2 2.50 6.28 5.83 7.2 E. 2 2.35 7.02 6.36 9.4 2 2.60 6.47 5.97 7.7 D. 3 3.15 9.49 8.78 7.5 3 3.21 8.03 7.36 8.4 P. 3 3.30 9.92 8.89 10.4 3 3.31 8.23 7.62 7.4 E. 3 3.25 9.72 8.83 92 3 3.43 8.57 7.90 7.8 D. 4 4.18 12.69 11.75 7.4 4 4.24 10.71 9.84 8.1 P. 4 4.28 12.94 11.66 9.0 4 4.35 10.96 10.09 7.9 E. 4 4.37 13.14 11.78 10.4 4 4.33 10.84 9.64 11.1 D. 5 5.04 15.05 14.29 5.1 5 4.42 11.25 P. 5 5.00 15.00 13.66 9.1 5 5.00 12.50 lV.56 V.5 E. 5 5.08 15.20 13.6.0 10.5 5 5.24 12.90 21 b. Density of concrete ; thoro ramming, Vol of 1 : 1 mortar, Vol of rammed cone, approx, 0.33 X vol of agg, 0.40 X " " " 0.91 X vol of agg, 0.93 X " " " 21 c. Density of aggregate; compacting. 2" ring, and having 43.3 _ Portage stone, broken to pass a 2" ring, and having 43.3 % voids when slightly shaken in the measure, had 9nly 37.4 % voids, as a mean of 5 trials, after being packed in the measure with a tamping iron, used about as forcibly as in ordinary ramming of cone. 22 22. Tests of Metals, '00, pp 1109, &c. For Contractors Plant Co. 22 a. Specimens; Port cem, sand, crushed stone, 1:3:5. Stone passed thru a 2 Yi' ring; pieces passing a Yz ring screened out. A, hand-mixt; B and mixt in a portable gravity mixer 8 ft long, consisting of a steel trough containing numerous rows of steel pins, staggered. Water from a spray pipe strikes the mixer about midway its length. Hence cone is mixt dry in the upper half, and wet in the lower. Stone spread evenly on a platform in front of mixer Sand ' top of stone Cem " sand. Material then shoveled into mixer. B. Allowed to form a cone-shaped pile, stones accumulating around All, 2 days in air, 2 Material, as discharged, levelled off with hoe. 12" cubes; beams from 4" X 6" to 6" X 6" 30" span, mos in water, 1 mo in air. * Consistency : D = dry ; P 100 (A C) t Shrinkage = - plastic ; E = excess. 1150 CONCRETE. For Directory to Experiments, see pp 1135-9. Results ; Cubes Beams Comp strength, Ibs/D" Rupture modulus. lbs/G" max av min max av min A 3516 3187 2930 454 414 367 B 4451 4256 4041 564 525 450 C 4380 4123 4019 536 451 348 2jj 23. W. H. Ileiiby. Jour Assoc Eng Socs, Sept 1900, p 153. 23 a. Cinder Concrete loses from M to % of its strength by being thoroly wet; but fully regains its strgth upon being dried. g^ 24. E. Dnryea, Jr, "Cement," Vol 2, '01 See E. Thacher, in A S C E, Trans, '05, Vol 54, Part E, p 447. 24 a. Finish. Tunnel portals, Los Angeles, Cal., two coats, 1 cem : 4 sand : 1 lime paste. Showed hair cracks where finished smooth. Pedestals, Chicag9 & E 111 RR, 1 cem : 1 sand. In good condition. Piers, Arkansas River bridge, Kan City So R R., two coats, 1 cem : 3 sand, one coat, 1 cem : 1 sand. In good condition. 1 cem : 3 sand : 1 lime paste, considered best. Excessive troweling should be avoided. Finish should be kept damp for two weeks. 25 25. Thayer School expts, '02. J. B. Mclntyre and A. L. True. 25 a. Permeability. 97 expts, specimens 10" diam, 9" high, %" pipe inserted 4". Pressures, 20, 40 and 80 Ibs/Q" (46, 92 and 185 ft heads), 2 hours. All specimens with from 30 to 45 % 1:1 mortar were imper- meable. Some with 40 to 45 % of 1 : 2, and some with 1:2:4 and 1 : 2.5 : 4, were impermeable under 80 Ibs. 1 : 2 : 4 or 1 : 2.5 : 4 recommended for moderate pressures. 26 26. Bretiill4, "Experiences sur le Ciment Arme," Ann des Fonts et Chaussees, '02, p 181. 26 a. Corrosion and adhesion in water. Specimens; 4 slabs 36" X 39," 11.8" thick; respectively 1320, 1320, 1760, 2200 Ibs Port cem, 11.6 cu ft sand, 31.8 cu ft pebbles, %" to 1" diam. Rods %o" diam, placed at diff dists from the surfs of the slabs. Treatment; slabs placed in water under heads of 40 to 50 ft (17 to 22 Ibs/Q") which were transmitted undiminished to the centers of the blocks. Pressures relieved from time to time. Treatment maintained for several days. Slabs then left in air, exposed to weather. Results. The metal was found perfectly preserved; but its surf, which was bright when placed, was found dull when exposed after the expt, and adhesion was destroyed where the water had circulated. 26 b. I^uster. Bars, with bright surf, placed in cem mortar for several days, showed dull surf after removal of the mortar, indicating chemical action betw the cem and the iron. It is probably by such action that rust is re- moved from rusted bars, placed in cem mortar The iron salt, formed by this action, is dissolved by the water which penetrates to the iron surface. 26 c. Gain and loss of weight. Small pieces of sheet iron, placed in cem mortar, gained about 0.01 % in wt in 76 days. Subsequently placed in running water, such plates lost wt, indicating the solubility of the compound, the formation of which had increased the wt. 26 d. Time; adhesion. Iron plates, 35 X 70 X 5 mm (1% X 2% X 0.2 ins) were laid upon freshly laid cone, in which the mortar (500 kg Port cem to 1 cu meter sand) flushed to the surf. At diff periods, these plates showed av adhesion as follows: 27 12 17 23 27 days 0.278 0.636 0.946 1.132 1.295 1.316 kg/sq cm 3.96 9.01 13.5 16.1 18.4 18.7 Ibs/sq inch The results of Expt 26 d were not materially modified when the mortar was kept in the sun, or mixt warm or very wet. EXPERIMENT AND PRACTICE. 1151 For abbreviations, symbols and references, see p 947 1. 27 27. G. Y. Skeels, Asst City Engr, Sioux City, Iowa. E N, '02, Nov 6, p382. 27 a. Avs of 2 and 4 briquets, 1 day in air, 14 ds in water. Port cem. Under continuous mixing for 8 or 10 hrs, neat cem mortar lost about % of its tensile strength ; 1 : 2 lost about %. 28 28. Thos. S. Clark, Resident Engr in Chg of Construction of Man- hattan R R Power Station, New York. E N, '02, Jul 24, p 68. 28 a. Retempering; strength. Neat nat cem mortar mixed initially with 28 % water; sand nat cem mortar with 14 %. Retempered an hour after mixing, "enough water being added, as in practice, to bring the mass back to its original consistency." One day specimens 3 hours in air, the others 24 hours. Retempered specimens showed, in general, about half the normal strgth. Similar results were obtained when the cem was moistened every 15 mins during the hour. In such cases, in practice, the strgth is sometimes increased by adding a little fresh cem. Port cem mortars, retempered after standing an hour, failed to show marked deterioration, probably because Port cem sets more slowly than nat cem. 29 29. W. Purves Taylor, A S T M, Vol 3, p 376, '03. 29 a. Age ; soundness. Ageing of finely ground cem permits hydra- tion of the free lime, nearly always present, rendering it inert and preventing expansive action. Specimens, made with cem one wk old, were unsound; but, as the age of the cem increased , the soundness of the specimens improved until, when the cem was 5 wks old, the specimens were sound. 29 b. Fineness; soundness. The larger particles of coarsely ground cem are not readily hydrated. A cem, of which 33 % remained on a No 200 sieve and 13 % on No 100, checked and cracked in the boiling test; but became sound when reground until all passed the No 100 sieve and allowed to season for 2 weeks. 30 30. French Government Commission, Beton und Eisen, '03, Vol 5. 30 a. Ductility. Cone 1:2:4. Results similar to Considered (see Expt 16 a). Ductility greater when hardened in water than when hardened in air. 31 31. Chas. List, Assn Eng Socs, Jour, Mar, '03, Vol 30, No. 3, p 128. 31 a. Effect of sea water at Gautemala, Central America. Hollow piles, in sea water, filled with cone in which sea water had been used for mixing. Some of the mortar leaked out, and formed, with the' surrounding sand, masses of cone which adhered to the piles. When piles were removed, cone was found perfectly hard and adhering tenaciously to the piles. 31 b. Railway bridge foundation, built 1895. Lean cone mixt with and standing in brackish water. Of excellent quality in '03. 31 c. Regrinding. Cem brought from Hamburg, Germany, in bbls. Vessel sprang a leak; cem considered a loss, and value refunded. Cem stored under the floor of a warehouse with open sides and exposed to mois- ture of ground and to spray from sea. Cem caked hard enough to be used as foundations for wooden 'posts in buildings. This caked cem was broken as fine as possible, and mixt with sharp beach sand and brackish water. Cone perfectly hard in 3 days and used in bridge foundations in brackish water. 32 32. Geo. W. L,ee, Jr., E N, '03, Mar 19, p 246. Finish. 32 a. New York Central R R. Forms (2" tongued and grooved pine) coated with soft soap ; openings in joints filled with hard soap. Cone deposited and drawn back from mold with a square-pointed shovel, and 1 : 2 1152 CONCRETE. For Directory to Experiments, see pp 1135-9. mortar poured in along the molds. After removal of molds, and while cone green, surf rubbeoT, with a circular motion, with pieces of white fire- brick, or bricks, of 1 cem : 1 sand; surface then dampened and painted with 1 : 1 grout, rubbed in and finished with wooden float. 33. Wm. B. Fuller, A S C E, Trans, '03, Jun, Vol 50, p 454. 33 a. Reinforced Concrete tank at filter plant, Little Falls, N. J. 10 ft diam, 43 ft high; walls 15" thick at bottom, 10" at top; built in 8 hours; all cone placed from top, thus falling 43 ft at first. Mixt very wet; placed 5 cu ft (wheel-barrow-load) at a time, and merely joggled into posi- tion. Tight against both inflow and outflow; intended inside plastering omitted as unnecessary. Surfs smooth, no stones or voids showing. 34 34. Prof. C. E. Sherman, E N, '03, Nov 19, p 443. 34 a. Clay and loam ; Strength. Dyckerhoff (German) and Lehigh (American) Port cems, with sands containing from to 15 % of clay and loam. Strgth in general in- creased materially with the percentage of clay and loam. With 10 and 15 %, the strgth, at 12 mos, was from 15 to 50 % greater than with clean sand. 35 35. Tests of Metals, '04, pp 345-387. 35 a. Concrete columns, plain and reinforced; ultimate comp strength, s, Ibs/sq inch and elastic modulus, E,* Ibs/sq inch. Specimens. Port cem and sand; agg, pebbles and broken trap, Y^ to 1 /^ and cinders. Cols approx 123^" X 12 W X 8 ft. Reinforcing rods; "Tw," %" twisted; "Cr," 5/8* corrugated; "Th," %" Thacher. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 suits. Atrp Reinforcement f. Age * . No. & Mix Agg Waterf mos days Kind % t s 0.001 E* 1 : 1 : 2 Pebbles 42.5 8 4Tw 1.46 2890 2660 7 28 None None 1720 2500 1:2:3 7 28 4Tw 1.44 2010 2273 53.1 7 25 None None 1769 2155 1:2:4 56.7 3 13 4 Tw 1.43 1990 1938 3 16 4Cr 0.97 2180 2212 3 14 4Th 1.03 1990 2315 3 15 8 Tw 2.86 3160 2500 " 3 14 8O 1.94 2830 3049 " 3 12 8Th 2.09 2760 3086 " 7 26 4Tw 1.45 1820 2381 " 3 17 None None 1710 2358 Trap "wet" 5 10 None None 1750 2809 Cinder 5 16 4Tw 1.45 2095 1404 " 5 16 None None 871 1000 1 : i : 6 Pebbles 74.4 7 24 4Tw 1.44 1370 1036 7 None None 462 1442 Trap 5 10 8Cr 1.94 2290 3086 57.6 7 None None 471 2208 36. F. E. Turneaure, A S T M, Trans, '04, p 504. 36 a. Ductility. Reinfd cone beams. Unit stretch of cone, on first appearance of cracking, 0.00010 to 0.00035, made up of sum of many small cracks, appearing when stress in steel > 5000 lbs/O". Plain beams rup- tured (without preliminary cracking) with equal unit elongation. The *E taken betw limits of comp stress as follows, Ibs/D": Nos 15 and 17, 100 to 600; 16, 600 to 1000; 19, 100 to 471; all others, 1000 to 1500. J% of cross sec area EXPERIMENT AND PRACTICE. 1153 For abbreviations, symbols and references, see p 947 1. cracks, corresponding to the lowest unit stretches, were invisible on dry cone, but were detected, in moist cone, by the appearance of narrow wet streaks about %" wide. A little later, they showed as dark, hair-like cracks. 37 37. Prof Bauschinger, "Beton und Eisen," '04, Vol IV, p 193. 37 a. Corrosion : adhesion. Fragments of reinfd cone plates, broken, in testing, '87; exposed outdoors until examined in '92. Adhesion; cone broken off by hammer blows, breaking only in immediate vicinity of blows. Corrosion; steel rust-free, even close to the exposed surfs of fracture. 37 b. Tank, injured by rough treatment; cracked; reinfmt laid bare in places. Rust only where so exposed. Adhesion as in 37 (a). 37 c. Fragments of Monier plates 6 to 8 cm thick. Exposed, at inter- vals for about 4 yrs, to sewage-polluted water. Cone remained hard; reinfmt rust-free 1 cm from exposed surface ; adhesion excellent. 38 38. A. Kleinlogel. Beton und Eisen, '04, 'Vol 2. 38 a. Ductility. Reinfd cone beams 15 X 30 cm, 220 cm long. 1:1:2, cem, sand, limestone screenings. Kept under moist sand 6 mos. Bendg mom constant thruout measd portion. Unit stretches in cone; reinfd, 0.000148 to 0.000196; plain, 0.000143. 39. Clarence Coleman ; Report, CM of Engrs, USA, '04. Part IV. Universal Port cem made from blast furnace slag. Av tensile strgth, Ibs/H" Sand* Mix WaterJJ 7 28 6 1 3 39 a. Q Q Q S s S s s s s s stt stt 1:3 1:3 1:3 1:3 1:3 1:10 1:10 1:10 1:10 1:3 1:3 1:10 1:10 1:3 1:3 12.5 12.5 12.5 12.5 12.5 Random Random Random Random 8.25 9.25 Random Random 8.25 8.25 da 176 173 199 1.00 t 1.17f 134 253 262 222 254 244 164 184 183 183 da 298 260 274 1.00 t 1.09 t 211 274 366 388 289 317 275 314 259 272 mo 424 411 424 yr yr Cem exposed in sacks to ciamp- Caked hard. Not set. Regrouncl 39 b. Cem as received on works Cem after 4 to 10 mos in sacks in 39 c. Cone haiid-mixt on platform t Cone mixt in cubical bateli- mixeriS .' 324 385 420 415 380 398 446 458 361 392 343 391 462 643 399 437 445 464 340 359 394 834 39 d. As in laborat'y, 24 hours in damp closet, then immersed As on work, 10 days under damp cloth, then in air until 39 e. 8.25 % water** 9 25 % water ** 39 f. I'ebbles Vie to 34 inch Pebbles % to % inch 99 g. Sand with small % clay * Q = Standard crystal quartz. S = Superior Entry sand; passingsieve No. 4 10 20 30 50 % 100 72.3 46.1 26.5 5.1 t Relative strgths. t Briquets made of cone taken from the works. A batch of very perfectly mixt cone in 80 sees. 1[ Cone taken from mixing platform Stones larger than %" removed. ** In order to approx working conditions, the mortar was allowed to stand 30 mins longer than under ordinary treatment. ttPassing No 10 sieve. tt Water in percentage of dry agg C9 1154 CONCRETE For Directory to Experiments, see pp 1135-9. 4O 40. Prof < has. L,. Norton, EN, '02, Oct 23, '04, Jan 14. Corrosion. Several hundred briquets of various mixes and consist- encies, with steel imbedded, subjected to air, steam and carbonic acid. 4O a. Steel clean when imbedded. 3 wks exposure. Steel perfectly protected by neat cem in all cases, and where the mortar was mixt wet, so as to cover the steel with thin grout. In cone, rust found only where voids or other defects existed. 40 b. Steel rusted when imbedded. 1 to 3 mos exposure. Changes, in size of steel, occurred only where cone had been poorly applied. 41 41. John S. Sewell, on Baltimore fire, E N, '04, Mar 24. 41 a. Results. "Concrete undergoes more or less molecular change in fire; subject to some spalliiig. Molecular change very slow. Calcined material does not spall off oadly except at exposed square corners. Efficiency, on the whole, is high. Preferable to commercial hollow tiles for both floor arches or slabs, and col and girder coverings." 41 b. Reinfd cone cols, beams, girders, and floor slabs, at least as de- sirable as steel work protected with the best commercial hollow tiles. 41 c. *' Stone cone spalls worse than any other kind, because the pieces of stone contain air and moisture cavities, and the contents of these rup- ture the stone, when hot. Gravel is stone that has had most of these cavities eliminated by splitting through them, during long ages of exposure to the weather. It is therefore better than stone for fire-resisting cone." 41 d. " Broken bricks, broken slag, ashes and clinker all make good fire-resisting cone." 41 e. *' Cinders, containing much partly burned coal, are unsafe, be- cause these particles actually burn out and weaken the cone. Locomotive cinders kill the cem, besides being combustible. Cinder concrete is safe only when subjected to the most rigid and intelligent supervision; when made properly, of proper materials, however, it is doubtful whether even brickwork is much superior to it in fire-resisting qualities, and nothing is superior to it in lightness, other things being equal." 42 42. Kinile Low, A S C E, Trans, June '04, Vol 52, p. 96. Buffalo Breakwater. 42 a. Shrinkage. Cement 258 cu yds Sand 365 Pebbles 1175 Broken Stone 972 Total Materials. . . 2770 Blocks made 2054 Shrinkage 716 " = 25.8 % 43 - 43. Alex. B. Moncrieff, Engr in Chief, South Australian Govt Letter to authors, June 7, '04. 43 a. Permeability. Specimens. Cone blocks, 2 ft cubes (8 cu ft), for expts in connection with construction of Barossa dam. Ingredients same as used on dam. Agg %" to 2", with varying voids. Preparation of aggs very carefully watcned. Treatment. Water brought to cen of block in Yj' wrought iron pipe terminating in a T piece, wrapped with hemp which formed a bulb abt 4" diam. Results. All the blocks became practically tight. Cone used in dam ' ' was based upon the results of the expts principally with blocks EXPERIMENT AND PRACTICE. 1155 For abbreviations, symbols and references, see p 9472. Nos 7 and 8." There is "practically nothing that could be called a leak" thru the dam.* Q = vol of mixing water, % of volume of cone; ._ vol of mortar vol of voids X = excess mortar = 100 - vol of voida ~> A = age of block, in weeks, when subjected to pres; / = interval in mins, betw application of pres and appearance of water on surf of block; Head = 100 ft = 43.4 Ibs/Q." Under 200 ft (86.8 Ibs/Q") "the effect closely resembled the results obtained from the head of 100 ft." Observed Leakage* No. Cem. Sand Agg * X A % Weeks I Mins. Mean rate Pints U. S gals /mo 1 1 1.84 5.26 16.65 5 11 t t t 2 1 1.84 5.26 15.45 5 11 34 % in 7 wks. 0.065 3 1 1.50 4.63 16.04 5 10 18 Vso 4 " 0.005 4 1 2.00 4.50 16.04 15 10 14 14 " 2 " 4.000 5 1 1.75 4.13 16.65 15 9 12 27 " 7 " 2.353 6 1 1.50 4.12 16.04 10 8 35 y 50 " 2 " 0.006 7 1 1.50 3.90 14.26 12.5 6 28 % " 2 " 0.037 8 1 1.50 3.70 13.68 15 5 30 Ho " 2 " 0.006 44 : 44. Edwin Thacher, A S C E, Trans, '05, Vol 54, pp 425, &c. 44 a. Effect of cold. Jlelaii arch bridge, at Mishawaka, Ind, 3 spans, 110 ft each, built in temps ranging from to 55 F. Hot water admitted to mixer. Cone laid at blood heat; warm enough to melt snow 48 hours later. Center arch completed with temp about 25 F. The next day, temp fell to F. Two wks later, an ice jam carried out the centering and left the a roll unsupported. No bad effects observed; settlement but little greater than with the other arches, centering under which was removed later and in the usual way. 44 b. Finish. Bridge at Oconomowoc, Wis. Mortar face, 1 cem : 1 granite screenings : 1 torpedo sand. On the second day after completion, molds removed and surf rubbed with a soft stone and water. Inman arch, Hohenzollern. 1 cem : 5 broken limestone. After setting 12 hrs, the loose cem was removed by water and brushes. Pacific Borax Co's factory, Bayonne, N. J. Finished to represent coursed ashlar, by inserting wooden strips in the molds and dressing the faces with a pneumatic hammer. One man could dress from 300 to 600 sq ft in 10 hours by machine, 100 to 200 by hand. Good effect. "Mr. Cummings produced a good finish by going over the surf with a wire brush while the cem was still green." Utica & Mohawk Valley Ry viaduct, Herkimer, N. Y., and viaduct over rys at Jacksonville, Fla. "A very superior finish." For a hard wall, wet the surface and apply a thin 1 : 2 mortar with a brush. Rub surface with a piece of grindstone or carborundum, removing board marks, filling pores and producing a lather on the surf. Go over this lather, before it dries, with a brush dipped in water. For a green wall (molds removed in less than 7 days,) use a thin grout of neat cem, instead of the 1 : 2 mortar. Remainder of process as above. Use smooth molds, deposit wet cone directly against them. After re- moving molds, float the surf with a wooden float, using only sufficient mortar to fill the pores and give a smooth finish. 44 c. Corrosion. Chicago. Iron rods, in limestone cone slabs which had covered sidewalk vaults for 8 or 10 yrs, rust-free. E. L. Ransome. * See H 4, p 1103. t Unreliable. 1156 CONCRETE. For Directory to Experiments, see pp 1135-9. Obelisk, Central Park, New York, small piece of iron set in mortar taken from the base. Bright after 2300 yrs. Iron drift bolts, from bed of cone at a lighthouse in the Straits of Mackinac, rust-free 20 years after laying, Wm. Sooy Smith. Osage River bridge, Mo., Iron cyl piers filled with Louisv cem limestone cone. Iron absolutely free from rust after 7 yrs service. Albert A. Tro- con, E R, Vol 38, p 273. Steel rods, sheet steel and expanded metal, embedded in cone blocks 3" X 3" X 8", and unprotected steel, all enclosed in tin boxes, and exposed, for 3 wks, one portion to steam, air and carbon dioxide, one to air and steam, one to air and carbon dioxide, and one to atmosphere of testing room Conclusions : Cone must be dense, and be mixt wet. Neat cement a perfect protection. With cinder cone, corrosion due mainly to iron oxide, not to sulfur. Cinder cone, if dense and well rammed, about as good as stone cone. Steel must be clear when imbedded. Steel must be coated with cem before being imbedded. Otherwise there will be more rust than steel in the result. Prof. Chas. L. Norton, Rep No. 2, Ins. Engng Expt Sta., Boston. Grenoble, France. Reinfd cone water main, Monier, 12" diam, 1 %o" thick, steel framework of ^ and Vie" steel rods. 15 yrs in damp ground. Adhesion perfect. Metal absolutely free from rust. Berlin. Reinfd cone retaining wall. After 11 yrs use, metal found free from corrosion, "except in some cases where the rods were within 0.3 or 0.4" from the surf." Effect of the cone, in preserving metal, not due to the exclusion of air. "Even thq the cone be porous and not in contact with the metal at all points, it will still filter out and neutralize the carbonic acid and prevent corrosion." S. B. Newberry, E N, Vol 47, '02, Apr 24, p 335. Links from anchorage of a suspension bridge partly built by Roebling in '55. Removed '75. Perfect. G. Bouscaren, E R, Vol 38, p 253. Niagara suspension bridge anchorage. No rust where limestone was not in contact with metal and where no movement had taken place. Perfect after 25 yrs. L. L. Buck. 45 45. Wm. B. Fuller, A Treatise on Concrete, by T and T, '05. 45 a. Moisture ; effect of tamping : Moisture Dry 6 % Saturated Reduction of vol, %, by tamping 9.6 18.8 8.8 Max volume in sands, when water is betwn 5 % and 8 % by wt. 45 b. Voids, between spheres of uniform diam ("large masses of equal sized marbles") could not be reduced, by pouring and tamping into a vessel, to less than 44 % of the mass. See f 30, p 947 b. 46 46. National Fire Protection Assn, Rept of Comm, '05. 46 a. Fire tests. Specimens. Beams 8" X 1 1 M" X 6 ft, each with 3 plain round steel rods, 6 ft 6" long, imbedded 1", 2" and 3" from bottom of beam. Port cem, Aggregates Mixtures Voids, % Screened coarse gravel 1: 2:3, 1: 2.5 : 5, 1: 3.5 : 7 35 Limestone, < 1M" " 42 Screened red granite, < 1 H" " 4 Ordinary cinders 1:2:5, 1:2:6 .... .... Wet mix. Specimens 45 to 48 days old. Treatment. 3 hours^n furnace; temps 1900 to 2000 F. Results. 46 b. Conductivity was lowest in the cinder concrete and in the richer cones. Otherwise materials had no important effect. 46 c. Strength of rods impaired 25 % at 770 F. Av time reqd to reach 770; 1" imbedment, 1 h; 2", 2 hs; 3", 2.5 hs. EXPERIMENT AND PRACTICE. 1157 For abbreviations, symbols and references, see p 947 1. 46 d. Clone did not break or ehip under fire; but lost practi- cally all strgth to a depth of 4" from sides and bottom, and softened per- ceptibly thruout. The cem and most of the stone were thoroly calcined at surf, and, to a diminishing extent, to a depth of 4". In all cases, a little water appeared in cracks running across the beams, especially with the richest mixtures and with temp at 212 F. 46 e. Recommendations. Materials should be well mixt, wet, by machine, and well tamped. Imbedment should be < 2"; in important cases, 3". 47 47. John H. Quinton, U. S. Geol Surv, " Expts on Steel-cone Pipes on a Working Scale," U. S. Water-Supply and Irrigation Paper 143, '05. 47 a. Permeability. To determine availability of such pipes under pres, for U. S. Reclamation Service. Specimens. Seven reinforced hand-mixed cone pipes, 5 ft diam, 6* thick, 20 ft long; each made in one section; one, same dimensions, in 4 sees. Skilled workmen. In 3 of the 7 pipes, and in 3 of the 4 sees of the 8th pipe, lime was used in the mixture. The pipes varied greatly in texture. One of them "seemed to be of a crumbly nature, and it would have been easy to cut a hole through it." Another was "exceedingly hard." Treatment. The pipes were tested with and without inside linings of cem and sand, etc, with and without lime paste. The Sylvester soap-and- alum wash (p 928), P and B waterproof paint, and other paints were tried; and clay was stirred up in the water within the pipes. Pressures up to 70 Ibs/Q" = 161.5 ft. head. Results. 47 b. In spite of all precautions, the pipes leaked, especially along tamping seams, leakage decreased greatly under pres, as percolating water filled the pores with laitance; but in the mean time the leakage may be sufficient to damage foundations of pipe. 47 c. Dry mixtures gave the more permeable cone. 47 d. With carefully graded gravels, it was found difficult to secure uniform distribution of the din sizes. 47 e. Keep cone shaded while mixing and placing. 47 f. Interruptions to work are least dangerous with wet mixtures, in tamping, avoid displacement of reinforcement. 47 g. Make reinforcemt strong enough to protect cone against ten- sile stress. 47 h. Soap and alum mixture of advantage in making cone; but %" plaster found advisable on inside, in two coats, the first with lime paste, to retard setting; the second (applied when the first is dry) to be troweled smooth. When dry, apply thick neat cem wash. 47 i. Reinfd cone pipes not recommended for heads over 70 ft (30 Ibs /Q''). For short dists, special precautions may justify 100 ft (43 Ibs/Q"). 47 k. Cone pipes liable to crack, especially along tamping seams; but, even if cracked, probably drier and more durable than other kinds. 47 1. When the pipes were broken up, rust appeared upon only 1 rod, which was rusted all around for a length of about 1 J^", where a large and long-continued leak had occurred. The pipe had been lined with a mortar containing sal ammoniac (ammonium chloride) and iron filings. 48. Considere. Beton und Eisen, '05, Vol 3 48 a. Ductility. Specimens. Mixture, 400 kg Port cem, 0.4 cu m sand, 0.8 cu m lime- stone screenings. Beams 15 X 20 cm, 3 m long. Tension side reinfd with 2 iron bars 16 mm round, and 3, 12 mm rd. Bendg mom constant thruout measd length. Treatment. One beam kept in water, one under damp sand, 6 moa. 1158 CONCRETE. For Directory to Experiments, see pp 1135-9. Results. Max unit stretches kept under water 0.00107 damp sand 0.00050 No cracks discovered, altho the surf was smoothed with cem. Strength unaffected. 49 49. It. Feret, "A Treatise on Concrete, Plain and Reinforced," by Taylor and Thompson, '05. 49 a. The injurious action of sea water is due chiefly to the siilfuric acid of the dissolved sulfates; hence, the cem should contain as little gypsum (lime sulfate) as possible. Port cem should be low in aluminum and in lime. The presence of puzzolanic material is advantageous. The jonc should be dense and impervious. 50 50. Prof Ira H. Woolsoii, Report to Astoria Light, Heat and Power Co., '05. 50 a. Character; strength. Strengths in Ibs/D" Tensile Compressive Port Cem, 1:2:4. Max Av Min Max Av Min Sand & broken limestone 176 161 153 2000 1753 1441 Crushed* & broken limestone 282 194 138 3400 2449 2040 50 b. Sand contained < 1 % loam; all past >" sieve; 75 % past 20 mesh sieve. Hudson R bluestone (limestone) passing 1 M" screen, retained on %" screen. Cone tampt wet in molds, 1 or 2 days in air, 5 or 6 in water. Air dried 4 to 7 wks. Results, see 50 a. 51 51. Prof R. C. Carpenter, Cornell Univ, Sibley Jour of Eng*g, Jan, '05. 51 a. Retardation of setting ; gypsum (lime sulfate) CaSO 4 , and calcium chloride, CaCl 2 . Both ground dry with the clinker. Initial set; paste bears a rod Via inch diam, loaded with M lb. Final set; V 34 " " " 1 lb. Time, in both cases, reckoned from time of mixing, and given in mins. Results. Percentage by weightf 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 5.0 6.0 7.0 Time in minutes Initial CaSO 4 2 6... 80 24 29 30 2728 27 1918 CaCl 2 2 115 160 167 127 103 45 97 .. 73 68 .. Final CaSO 4 52 87 ... 157 114 79 69 72 45 59 37 59 ' CaCl 2 52 274 272 234 212 180 182 185 .. 160 145 .. 51 b. E. Candlot (Ciments et Chaux Hydrauliques) found that concen- trated solutions of CaClo (such as 100 to 400 grams per liter) accele- rated setting and hardening. 51 c. Addition of slaked lime to a cem containing gypsum which, with time, has lost its retarding effect. Initial, mins Final, mins 2 % gypsum, no lime 12 15 " " + 5 % " 120 300 2 to 5 % of lime is useful in this respect, but not without the gypsum. The lime does not diminish the strgth. 52 52. Jas. C. Ilaiii. Chic, Mil and St P Ry. E N, '04/Apr 28, p 413 E R, '05, Jan 28, p 103. Sand; size and cleanliness. *%" crusher screenings; 87 % past H" sieve, 40 % past %" sieve- t 1 % = about 4 Ibs CaCl 2 to a barrel of Port cem. EXPERIMENT AND PRACTICE. 1159 For abbreviations, symbols and references, see p 947 1, Specimens. 52 a. Impure sands. 1 : 3 Port cem mortars, made with (a) sand of smooth rounded quartz grains, mixt with larger fragments of limestone shells, 92 % past No 24 sieve, 28 % past No 50; (b) "St Paul standd sand," 54 % past No 24; 11 % past No 50; (c) "Ottawa standd sand." Results : Relative tensile strgths (a) 100; (b) 137; (c) 107.5. Sand (a) made excellent cone in a draw-span center pier. 1 : 3 Port cem mortars, with sand containing 3.2 to 15 % clay; strgths < with clean sand. With nat cem 1 : 3, and Port 1 : 2, the results were generally favorable to the cleaner sand. Sand with 6 % clay gave stronger mortars before than after washing. Sands, to which 2 to 20 % rich loam had been artificially added, gave mortar testing somewhat irregularly but in general higher than those with clean sand. 52 b. Fine sand, with clay. A sand, all passing No. 100 sieve, 93.2 % passing No. 200 (therefore finer than most cem. See Specfs), and containing 12 % clay, gave a 1 : 3 Port cem mortar showing, at 6 mos and 1 yr, nearly the same tensile strgth as similar mortar made with "Ot- tawa standard sand," but the mortar was weaker at shorter periods. 53 53. Jas. C. Haiti, Engr of Masonry Constn, Chic, Mil and St P Ry, E N, '05, Mar 16. Oil. Tests by Oeo. J. Oriesenauer. 53 a. A neat Port cem briquet. 2 yrs old, exposed to occasional drippings of signal oil, began to disintegrate in 10 mos; but no recent cone structures were found perceptibly injured by oil. A cone floor, upon which lubricating and lighting oils had been stored for 6 yrs, was apparently unaffected. Oil penetrated about Ha". A piece of this floor, in oil 10 mos, still sound. 53 b. Port cem; neat; 1:3 sand; 1:3 limestone screengs; 18 bri- quets each; 4 days in air. Then saturated daily with signal oil; later less frequently. Cracks appeared in the 1 :3 specimens in 2J^ mos; in neat specimens in 5 mos. All the briquets disintegrated eventually. 53 c. Port cem ; 54 briquets, neat; 36 briquets 1 : 3 sand. 7 d in air. Then saturated daily with oil; later, less frequently. Oils used; extract lard, whale, castor, boiled linseed, crude petroleum, signal. Cems made from limestone and clay, marl and clay, limest and slag. Lard oil disintegrated most of the briquets in from 2 wks to 2y% mos, but some re- mained sound for 9 mos. Signal oil (animal and mineral mixt) had nearly the same effect. Whale and castor oil affected only a few briquets; while petroleum and boiled linseed disintegrated no briquets. Petroleum di- minished strgth somewhat. Boiled linseed formed a protective coating and did not affect strgth. As a rule, the neat briquets yielded first. In general, briquets of limestone and slag yielded most; those of limestone and clay least. 53d. Silica cem; neat, 1:1, 1:2, 1:3, sand. 1 briquet each. 2 yrs in water; 20 days in warm air. Signal oil 2 yrs. First 3 briquets sound; 1 briquet (1:3) disintegrating. 53 e. Linseed oil, Sylvester's process (p 928), paraffine, and water glass (soda silicate) were applied, as coatings, to the briquets, but all failed to protect them against the action of the oils. 53 f. Rich cone, well made of good materials and well set and sea- soned, is best for resisting oil. In practice, cone structures are rarely, if ever, saturated with oil, as were these specimens. 54 54. Chas. A. Matcham, Nat Builders' Supply Assn, E R, '05, Apl 15, p 435. 54 a. Corrosion. 1160 CONCRETE. For Directory to Experiments; see pp 1135-9. Specimens and treatment. 6-inch cone cubes, 3 yrs old, with 3* steel cubes embedded. Two cubes, with mi painted 3" steel cubes embedded, exposed to Bummer and winter weather, and sometimes covered with snow ami ice. Results. Steel uninjured. Crushing strgths, 2920 Ibs and over 4166 Ibs/d*. One 6" cube, with 3" steel cube (painted with metallic paint) embedded, placed in bottom of river. Steel uninjured. Paint disappeared. Crushing strgth, 2907 Ibs/D". 55 55. Prof Ira H. Wool HO 11. E N, '05, Jun 1. 55 a. Absorption. Specimens. 8" cubes, 1:2:4, 3 weeks old, kiln dried 13 days at 120 F. Part with sand with < 1 % loam; all past 0.125" screen ; 75 % past 20-mesh sieve. Part with %" limestone crusher screenings; 87 % past M" screen; 40 % past 0.125" screen; sand and dust, enough to fill voids. Stone past 1 y? ring. Results. Av absorption ; 4 hours, 2.87 % ; 24 hrs, 2.95 % ; 48 hrs, 3.33 %. No marked diff betw sand and screenings. 56 56. W. C. Hoad, Univ of Kansas. E N, '05, Aug 10. < lav and l-oani; strength and absorption. 56 a. Port cem with (a) staodd Ottawa sand, 1 : 3; (b) 2 to 20 % of the sand replaced by clay or loam. At 90 days, relative strgths; in general: (a) 100; (b) 94 to 125. 56 b. Up to 6 or 8 % clay or loam, there was no increase of absorption, with loam; and about 10 % decrease, with clay. With higher per- centages, the absorption increased somewhat. 57 57. Eng' News, '05, Sep 28. 57 a. Permeability. Reinforced concrete cistern, 75,000 gals. 1:2:4, Port cem, river sand, gravel. 1" layer of 1 : 1 mortar on bottom. Walls washed with 3 coats neat cem grout, cream consistency, put on with whitewash brush after walls were well wetted. Each coat dried for 24 hrs. If too wet, the coating crackt. If too dry, it could not be brusht on. For a few days after filling, lost %e" in depth per day. Perfectly tight since. Cistern built with outside air at temp below 2O F ; but was covered with boards, and two coke salamanders were used. 58 58. Prof Ira H. Woolson, E N, '05, Nov 2. 58 a. Flow. Specimens. Cols, 4" diam, 12" long, formed in steel tubes, 1 A" to M" thick, and allowed to set and remain there for 17 days, when the cone appeared very hard. Cone remained in tubes during tests. Results. Under loads of 150,000 Ibs, the cols in the stouter tubes were merely shortened < M"; but under loads of 120,000 to 150,000 Ibs, the cols, in some of the lighter tubes, were bent out of shape and shortened by 3 }4", their diam increasing from 4" to about 5". Upon removal of the tubes, the cone was found unbroken, solid and perfect ! 59 59. J. Itt. Braxton, U. S. Asst Engr. Reports, '05-6 E N, '08, May 14, p 525. Corrosion in sea water. EXPERIMENT AND PRACTICE. 1161 For abbreviations, symbols and references, :-;ee p 9472. 59 a. Yi' steel rods imbedded in 4 cone blocks made with coral sand and broken brick. 2 blocks in 4 ft of sea water; 2 in a dry closet, both for more than a yr. The rod in one of the dry blocks showed signs of rusting. The others were as bright and smooth as when placed. 59 b. 30 blocks, 12" X 12" X 6"; Port cem, 1:3:5, broken brick. Made under usual working conditions. %" twisted steel rod, 8" long, in cen of each block. 20 blocks with coral sand, 10 with ordinary quartz sand. Half of each placed in ocean, half in air without roof. Broken after 1 yr, 3 wks. In all the blocks placed in the ocean, the rods were found in perfect condition. All the others were more or less rusted. 6O 60. Wm. R. Baldwin- Wiseman, Instn C E Procs, '06, Vol 163, p319. 60 a. Puddling- effect of water flowing thru cone discs, 13" diam, 6" thick, 1 : 4 Port cem, crushed gravel passing 1" ring. Sp gr of cone 2.23, 140 Ibs/cu ft. In wooden molds 10 wks. Water, for pres, pumped from chalk formation, hardness reduced from 18 to 6. Air temp 12 to 15 C = 54 to 59 F. Pressures, 24 to 60 Ibs/Q" = 55 to 139 ft. Leakage as per Fig 4. Toward the close of the expts, small stalactitic growths 100 ' C ^ou 1" 20 \ \ ^v, I -- - I 2 i *- 46 Days Fig 4. Puddling. formed on bottom of test piece, and leakage was absorbed by evaporation. Near the surf, the water, under high pres, dissolved out some of the material, but deposited it in the pores farther on, where the pres had been reduced by passage thru the block. 61 61. San lord E. Thompson. A S T M, Procs, Vol VI, 1906, p 379. 61 a. Consistency ; effect upon density,* permeability and compressive strength. Density and permeability specimens, 21 days old; comp strgth specimens 5M mos. Specimens. Atlas Portland cem; Newburyport sand, sp gr = 2.65; trap, sp gr = 2.78. 1 : 2.3 : 4.6 by vol; 1 : 2 : 4 by wt. Consistencies used. Water, % } Dry. Like damp earth; water glistened on surf under hard ramming 5.4 Medium. Looked wet when mixed. Did not flow in mixing box. Slightly quaking. ... 6.9 Wet ....;.. .--.: 9-2 Very w r et. Like thick soup. Settled to a level in mixing box. Required scoop shovels for handling. Slightly wet- ter than usual in building work 11.0 Extremely wet 13.7 * Density = vol of solid particles in unit vol of cone, t Percentage of weight of cem, sand and stone. 1162 CONCRETE. For Directory to Experiments, see pp 1135-9. Results. See Fig 5. ^ 0.850 0.800 0.750 Q 0.700 2000 e Stren f! | S -SJ4003 I Oo er m M 5.4 6.9 9.2 11.0 Water, Percentage of Dry Materials by*Weight. Fig 5. Consistency. 13.7 For a given consistency, the percentage of water depends upon the nature of the cem, and upon the size and dryness of the sand grains. A fine sand, or one with many fine grains, may require twice as much water as coarse sand requires. 61 b. Elastic iiio? mesh 90.8 % B, Cowe Bay sand, much used in and about New York . . 95.8 % C, fine clean silicious sand 95.5 % Results. In 7 and 28 days, 1 : 2 and 1 : 3 mortars, A and B gave, in general, from 20 to 50 % greater tensile and comp strengths than C. In general, the stronger mortars showed the higher absorptions. 63 63. Alex. B. Moncrieff, E N, '06, Aug 30, p 227. 63 a. Briquets in water 2 yrs, in air 7 days arid in oil 6 mos. In general, neat cem lost from to 36 % strgth, while 3 : 1 gained from to 65.5 %, by air drying and immersion in oil. 63 b. Briquets in air 7 days; then 6 mos in either oil or water. The neat cem briquets in oil were from to 55 % weaker than the neat cem in water; the 3 : 1 briquets in oil were 49 to 79 % weaker than those in water. EXPERIMENT AND PRACTICE. 1163 For abbreviations, symbols and references, see p 947 1. 63 c. Briquets in water 9 wks; others in water 4 wks, in air 1 wk and in oil 4 wks. With few exceptions, the neat cem briquets in oil were from abt to 40 % stronger than like briquets in water, while the 3 : 1 briquets were from abt to 63 % stronger than like briquets in water. Many of the oil- treated briquets "snapped like flint." 64 64. Prof Arthur ST. Talbot, Univ of 111. Bull, Vol IV No. 1. '06, Sept 1. 64 a. Adhesion and friction. '04. Specimens and results. Mix, 1:3:6. Pull, in Ibs/D" of net section; Elastic limit, in Ibs/D"; Adhesion, in Ibs/Q" of imbedded surf: Johnson bars Round bars Square bars ^2" %"~* H" W~^ %" 1 A" %"~* Pull 71,412 34,500 31,500 21,500 35,656 26,510 20,860 Elaslim 60,000 58,300 42,500 40,500 45,000 33,300 35,000 Adhesion 595 420 249 315 297 286 325 With all the Johnson bars, the specimens split or broke. All the plain rods slipped. 6 of the 11 Johnson bars, and 4 of the 11 bars %" square, were "struck 6 quarter-swing blows with a 10-lb sledge," reducing their adhesion by abt 5 to 20 %. Specimens. 64 b. '05-6. Cylinders, 6" diam, 6" and 12" long; 60 days old. Mixture of Am Port cems, tensile strgth, neat, 723 Ib/Q" at 7 days; 1 : 3, 354 at 7 ds, 533 at 75 ds; coarse mortar sand; broken limestone, screened thru 1' and over 38,000; Flat, 45,000; Cold 53,000. Results. No. of tests Steel Size Metal, elas lim, Ibs/Q"; Mild steel (M), Round. rolled shafting (C), 87,000; Tool steel (T). Mix 6 1\ 1 1/3" round 1 :3 5.5 6 " 1 : 2 4 6 %" round 1 :3 5.5 4 " 1 : 2 4 3 %" round 1 :3 5.5 4 " 1 : 2 4 3 %" round 1 :3 5.5 3 " 1 : 2 4 3 ' i m x %" 1 :3 5.5 3 < D 1" round 3 W round ' 3 T %" round 1 :3 6 Imbedded length, *- ins. Adhesion 372 412 355 465 373 404 402 414 125 136 157 147 Lbs/Q" im- bedded surface Friction f/a 12 210 227 227 297 268 266 228 223 84 67 50 0.57 0.55 0.64 0.64 0.72 0.65 0.57 0.54 0.67 0.49 0.32 Rich mixture generally superior. Cold rolled shaftg and tool Steel generally inferior, owing to uniformity of sec and smoothness of surf. 65 65. Jos. W. Kl Ims. Chemist, Commissrs of Water Works, Cincinnati. E R, '06, Oct 27, p 487. 65 a. Permeability. Specimens. Port and nat (Louisville) cem; Ohio River quartz sand, clean, rather fine, quite uniform in size; limestone screenings, with much very fine dust. " cubes; Port cem; (a) 1 cem : 2 sand, 10 % water; (ft) 1 cem : 1 sand : 1 screen- ings, 11 % water; (c) 1 cem : 2 screenings, 14 % water. 77 1164 CONCRETE. For Directory to Experiments, see pp 1135-9. Nat cem; (d) 1 cem : 2 sand, 15 % water; (e) 1 cem : 1 sand : 1 screen- ings, 15 % water; (/) 1 cem : 2 screenings, 17 % water. Hollow Cylinders; 6" diam, 8" long, 2" hole; Port cem and sand, 1 : 1, 10 % water. Treatment. Water (clear) brought to centers of specimens. Cubes, 1 day in air, 6 in water. Cyls, 1 d in air, 27 in water, 4 in air. Results. Leakage past thru mortar 1 W to 2" thick. Cubes ; under 50 Ibs/D" (115 ft head) maintained from 3 to 16 hrs, little or no water (max = 0.16 gal/hour per Q ft) past thru the Port cem cubes; from 0.29 to 2.40 gals /hour /D ft thru the nat cem cubes. Portland, leakage became appreciable at 60 to 75 Ibs/Q" (138 to 173 ft); nat, at 15 Ibs (35 ft). The 1 : 2 sand cubes were the most permeable. Cylinders, 15 to 30 Ibs/D" (35 to 70 ft); leakage 0.00023 to 1.228 gals/hour /Q ft. Leakage diminished very noticeably with time. 66 66. W. J. Douglas, Engr in Charge of Bridges for Wash, D. C., E N, '06, Dec 20, p 649. 66 a. A bridge, painted with a cement rich in free lime, showed afterward a mass of blotches of different colors. 67 67. Prof C. von Bach, Zeitschrift des Vereins Deutscher Ingenieure, '95, '97. 67 a. Relation between unit stretch and unit stress. " Potenzgesetz " (Law of powers). Specimens. Cone cylinders, 25 cm diam, 1 m long. Deformations measd on a length of 75 cm. Treatment. Load of 8 kg/sq cm alternately applied and released until the deformation no longer increased. Then similarly with 16 kg/Q cm, and so on to 40 kg/Q cm. Results. From the beginning, the deformations increased faster than the loads. Let s = unit stress = stress per unit of cross-section area; L = original measd length of 75 cm; I = reduction of L under compression; e = l/L = unit deformation; c = a coefficient, depending upon character of material; m = an exponent, Then, e = l/L = c . a Approximate Values Mixture 1 /c Cem Sand Gravel Stone For sin kg/Q cm. For sin Ibs/Q". m 1 2.5 5 298,000 6,147,000 1.14 1 2.5 5 457,000 9,940,000 1.16 1 3.0 315,000 6,672,000 1.15 1 1.5 356,000 6,781,000 1.11 (1/c for in Ibs/Q") -H (1/c for s in kg/Q cm) = 14.2234 m . 68 68. R. C. Carpenter. A S T M, Procs, '07, Vol 7, p 398. Unseed and engine oil ; soundness and tensile strength. Neat cem briquets, some with 2 % of linseed or of engine oil added to the mixing water; the others without oil. No. of briquets not stated. 68 a. Soundness. 24 hours in moist air. Briquets, mixt without oil, S9und after 8 days in either oil. Briquets mixt with and without oil, remained sound after boiling for 3 hours. EXPERIMENT AND PRACTICE. 1165 For abbreviations, symbols and references, see p 947 1. 68 b. Tensile strength. Oil in mix Tensile strength, Ibs/Q" 1 day 7 days 28 days None 430 696 743 2 % linseed 180 493 572 2 % engine 332 689 696 69 69. M. R. Barnett, Inst C E, Procs, '07, Vol 167, p 153. 69 a. Action of soft water upon limestone cone. Thirlmere aqueduct, water supply of Manchester, Eng. Section of aqueduct, made with limestone cone. Floor, 9" thick, reduced about M" in thickness, honeycombed, eaten thru in many places, and leaking badly. 69 b. Samples of the limestones, from which the cone was made, were kept, for 6 mos, in running soft water, in the aqueduct, and were found to lose wt at rates ranging from 6.8 to 18.1 % per year, while sample blocks of neat and 1 : 1 Port cem mortar, gained 5.5 and 3.6 % respectively. Deg of hardness of water, 2.18. 70 70. Prof Ira H. \Voolson, AS T M, Procs, '05, p 335; '07, p 404. High temperatures and thermal conductivity. 70 a. Mixture, 1 : 2 : 4; with cinder, 1:2:5. Cem, an equal mix of 3 Portlands. Sand, sharp, fair qual, "not especially clean"; 90 % past a 12-mesh sieve. Agg, fair quality boiler cinder, with most of the fine ashes removed; %" clean quartz gravel; crusht trap. Mixt moderately wet; tampt in molds until water flusht to surf. 2,000 1,000 1,500 Temperature, in degrees F. Fig 6. Heat Resistance. 2,000 c 2,500 7O b. High temperatures. '05, p 335. Fig 6. Specimens. For comp strgth, 4" cubes; for elasticity, prisms 6" X 6" X 14". 3 cubes and 3 prisms tested without heating; 3 cubes and 2 prisms of each agg (trap and limestone) at each temp. Results. 7O c. Elastic modulus, E. For E, the trap and limestone curves nearly coincided. 7O d. After heating to 2000 and 2250 F, the limestone cubes appeared sound while hot, but disintegrated when cooled. 1166 CONCRETE. For Directory to Experiments, see pp 1135-9. 7O e. After cooling from 750 F, both trap and limestone prisms were covered with minute cracks. Under higher temps, these cracks in- creased in number and in size, and the prisms warped and disintegrated after cooling from 1500 F. 7O f. The trap and cinder cone specimens remained sound, while the gravel cone specimens cracked and crumbled in pieces, probably owing to high expansion coeff of quartz, and to the fact that this coeff in one direction, is double that in the perp direction. Heated Face A5 il !! |! ! ILJ j 5 9 o o o o o * 3- ->i *-- 3 > Fig 1 7. Thermal Conductivity. Dimensions in inches. 1,400 1,200 fc - 1,000 800 100 200 JL, 10 20 30 40 50 60 70 80 90 100 110 120 Time, in Minutes. Trap. Fig 8. Thermal Conductivity. 70 g. Thermal conductivity, '07, p 404. Figs 7 and 8. Specimens. Cone blocks, with holes as in Fig 7. Dimensions in inches. Thermo couple in each hole. Mixture as in 7O a. Treatment. Specimens in molds 24 hrs, in water 48 hrs, kept moist 2 or 3 wks, allowed to dry well. Age, at test, about 2 mos. Blocks placed in furnace doorway. Results. Fig 8 shows, for one of the trap cone specimens, the times, in mins, reqd to transmit the furnace temps thru diff thicknesses of cone. Each curve is marked with this thickness in ins. Drop of curves, at and near 200 F, attributed to steam generation. EXPERIMENT AND PRACTICE. 1167 For abbreviations, symbols and references, see p 947 1. 7O h. 2 to 2 W of cone (if it remains in place) will protect reinfg metal during any ordinary conflagration. 7O i. Exposed reinforcing metal will not conduct heat injuri- ously to imbedded portion. 7O.5. Win. B. Fuller and Sanford E. Thompson, " The Laws of Proportioning Concrete," A S C E, Trans, '07/Dec, Vol 59, pp 139-143. Elastic modulus, E, under compression. Specimens. 6" sq cone prisms, 18" long ; age, abt 140 ds. Giant Port cem. Agg : Cowe Bay sand (CS), Jerome Park screenings (JSc). Agg : Cowe Bay gravel (CG), Jerome Park stone (JSt). Results. Effect of maximum size of stone. Mix. .............. 1 : 9* 1:3:6 1 : 2.81 : 5.62 1 : 2.92 : 5.88 Stone Elastic modulus, E, in millions of pounds per square inch. 2.25 ins 2.1 2.4 3.3 3.0 1.00 " 1.7 1.8 3.1 2.6 0.50 " 1.4 0.9 ... - 2.2 Effect of quantity of cement, in % of total dry material.* Elastic modulus, E, in millions of pounds per square inch. Cem.. E.. With JSc and JSt. 8 10 12.5 15 1.8 2.1 2.3 4.7 With CS and CG 8.5 10.6 13.25 15.9 2.3 3.9 3.7 4.3 With JSc and CG 10.2 12.75 15.3 3.5 3.8 3.5 71 71. Richard I,. Humphrey, U. S. G S Bull, No. 324, '07. Report on San Francisco fire of Apr 18, '06. Results. 71 a. Cone probably the best material for fireproofing cols. Its stiffness supports the steel within, softened by the heat. 71 b. "Cone proved superior to brick as a fireproofing medium." 71 c. At high temps, cone loses its water of crystallization. 71 d. Cone, especially when reinfd, resisted both earthquake and fire. The coiic dam, at San Mateo, altho within a few hundred yds of the fault, was uninjured. Solid cone floors, altho of very poor quality, proved satisfactory The cinder cone used, in floors and elsewhere, was high in sulfides, and injurious to reinfmt. 72 72. Wm. B. Fuller, NatI Assn of Cem Users, Procs, '07, pp 95-7. Grading and proportions. 72 a. Tests of 6 beams, 6" square, 6 ft long; 1 cem to 8 of sand and stone; rupture moduli in Ibs/D": 1:2:6, 319; 1:3:5, 285; 1:4:4, 209; 1:5:3, 151; 1:6:2, 102; 1 : 8 : 0, 41. 72 b. With a given percentage of cem, the densest mixture of sand and agg gives the strongest, the least permeable and therefore the most durable cone, and that which works most easily and therefore best fills up voids and corners. 73 73. Commission du ciment arm, Paris, '07. 73 a. Shrinkage and expansion. Cone shrinks while hardening in air, and expands under water. * Material, larger than 0.2" diam (abt 62 to 68 % of total) graded in accordance with the recommendations of the authors. See Plain Concrete, 11H 23 to 25, p 1089. 1168 CONCRETE. For Directory to Experiments, see pp 1135-9, 74 - 74. T. 1^. C 'on (Iron, of Condron and Sinks Co., representing Expanded Metal & Corr Bar Co. Jour, Western Soc of Engrs, '07, Feb, Vol 12, No. 1. Experiments by Prof C. E. De Puy, Lewis Inst., Chicago. 74 a. Adhesion ; plain and deformed bars. Specimens. Cone cylinders, 6" diam, 8", 12", 16", 20", 24" long. Hand mixt, accu- rately proportioned; 1:2:4, Port cem, coarse sand, broken limestone, W and under, without dust. Fairly wet, so as to enter molds easily and be churned with a small rod. All the cone mixt in one batch. The 8" and 16" blocks were 25 days old when tested, the others 31 ds. The rods past en- tirely thru the blocks. Results. Stress, Ibs/D" of imbedded surf Slip > 0.01" Slip > 1/32" Diam > . . in Imbedded Imbedded inches 12" 24" 12" 24" Adhesion, Ibs/D" Round iVie 269 178 289 190 Square K>Ae 316 229 341 242 Twisted, Buffalo " 334 291 357 306 Twisted, Ransome* " 324 332 366 350 Johnson.f New " 474 471 612 506 Johnson, Old* 12/16 651 535 786 535 75 75. A. A. Knudson, Am Inst Elec Engrs, Procs, '07, Feb, Vol. 26, Part I, p 231; E N, '07, Mar 21, p 328. 75 a. Electrolysis. Specimens. 1 : 1 cem and sand, Port and Rosendale. Blocks molded in metal water pail; positive electrode, a short 2" wrought iron pipe in axis of block, im- mersed about 8". Treatment. Blocks placed in water (one in fresh, one in salt) in tank; negative electrode, a piece of sheet iron, immersed in tank. Current 0.1 ampere. Results. After 30 days, Portland blocks (which had cracked under current) were easily broken, and showed yellowish deposits (ap- parently iron rust) and softened cone, in the seams. Pipes lost more than 2 % by corrosion. Final electrical resistance = 10 X initial resistance, and about = resistance of dry cone. Rosendale, cracks ap- peared in 6 days. One of the pipes eaten thru. 76 76. J. TL. Van Ornum, A S C E Trans, Vol. 51, p 443, '03/Dec, and Vol 58, p. 294, '07/Jun. 76 a. Fatigue. Neat cem blocks in comp. Repeated loadings cause failure if the load is > abt half that reqd to crush with one application. Vol 58, p 294. 76 b. Fatigue. About 600 tests. Specimens. Blocks 5" X 5", 12" long, in cqmp, and beams, 4" wide, 6" deep, 6 ft span, reinfd by 2 plain steel bars, W in square. Each batch made 8 blocks or 4 beams. Mix, 1 : 3 : 5 by vol. Standd Am Port cem, tested by A S C E specifications (p 942). Sand from Mississippi R, water-worn, rather fine, 99 to 110 Ibs/cu ft; voids 30 to 38 %. Broken limestone from near St. * Covered with thin coat of rust, but without scales. The others fresh from the rolls and free from rust. fA. L. Johnson's corrugated bar, Fig. 2d, p 1130; Expanded Metal and Corrugated Bar Co. EXPERIMENT AND PRACTICE. 1169 For abbreviations, symbols and references, see p 947 1. Louis, 80 to 95 Ibs/cu ft, passing 1%" screen; abt half the stones larger than 1", about one-tenth of the stones less than^"; voids 42 to 48 %. Voids, in 3 sand + 5 agg, 16 to 19 %. Treatment. Comp specimens left in molds in air 1 day, beams 2 ds; then all in water 2 wks; then in air, protected from drafts, until tested. Comp specimens, 1 mo and 1 yr old, loaded 4 to 8 times per min; beams, 1 mo, 6 mos and 1 yr, loaded 2 to 4 times per min. Results. Effect of rate of repetition insignificant; but be- lieved to increase rapidly with rates above 10 per min. oeated load-i-max. strength P P P P t- O to rf*. OS OO c V ^No. of Thousands of Repetitions necessary to produce failure. Fig 9. Fatigue. Fatigue. The curve, Fig 9, fairly represents the results obtained under these varying conditions. 76 c. Cone, repeatedly stressed, below the fatigue limit (i. e., below about half max strgth, see Fig) "has imparted to it a definite elastic limit, within which stresses are proportional to strains" (i. e., within which the elastic modulus, E, is constant). 76 d. Fatigue and Adhesion. Specimens. Plain %" square steel bars imbedded in cone as above. Specimens made with great care and very thoroly tamped. Treatment. In molds 2 days, in water 7 ds, in air 3 wks. 30 fatigue specimens subjected to "a combined blow, pressure and the accompanying vibration"; 150 blows per min, each blow = 740 inch-lbs. Av, 50,000 blows to each specimen. Results. Av initial adhesion, 125 Ibs/D" of imbedded surf; friction (after slip) 90 Ibs/Q". Uiifatigued specimens, 150 and 100 Ibs/Q" respectively. 76 e. Fatigue under continued load, p 318. 2 cone prisms remained unaffected for a month under 90 % of their crushing strgth. "A few cone blocks failed in comp in a few hours under constant pres of higher 77. Henry S. Spackmau. 07, Dec. Assn Am Port Cem Mfrs, New York, 77 a. Mortar reground after hardening. Briquets of Port cem, broken in testing. Reground and made into new briquets. These showed, in general, about half the tensile strengths of the original briquets. Of the original cem, 91.5 % past a No. 100 sieve, 76.2 % past No. 200. The reground material had abt the same fineness. 78. R. Feret, A S C E, Trans, '07, Dec, Vol 59, p 152. 78 a. Permeability. " Experiments give in general uncer- tain results. It is not unusual to see many blocks of the same cone CIO 1170 CONCRETE. For Directory to Experiments, see pp 1135-9. which, altho treated in an identical manner, permit very diff quantities of water to filter thru them." 78 b. Age of block, days 5 29 30 365 Flow, in grams/min per Ib/Q* Presfrom71 to2841bs/D*; Avge 0.554 0.044 0.159 0.294 After remaining under 284 Ib/Q* 2 hrs 0.349 0.034 0.133 0.278 78 c. Percolation "very nearly proportional to pressure." 78 a. 3 blocks, 1 year old. Block ABC Flow, in grams/min per lb/D" At2841b/sqm 0.067 0.111 0.108 Raised to 412 lb/D* 0.077 0.114 0.126 Reduced to 284 lb/D* 0.068 0.114 0.111 "as if the effect of the momentary increase of pres had been to open new passages for the water, or partly to clear out the passages already existing." 79 79. Wm. B. Fuller and S. E. Thompson. A S C E, Trans, '07, Dec, Vol. 59, p 67. Strength, density and permeability, as affected by propor- tions and character of sand and agg. Expts at Jerome Park Reservoir, New York. 79 a. Specimens. Port cem, as received for use on the reservoir; agg (1) stone and screenings from crushers at reservoir, mica schist, 35 % mica, which, in mortar or cone, "does not form planes which affect the strgth seriously." (2) Cowe Bay gravel and sand, dredged from river ("water- worn rounded bank gravel and sand, thoroly clean, and consisting almost entirely of quartz particles." Sp gr abt 2.65). Max size of stone, 2M", I", y z ". 30 10 20 40 60 808.5 1010.6 12 13 Lt 15.9 Pressure, IBs. iper sq. in. Cement, per cent of total dry material. Fig- 1O. Permeability. Tests were made with " graded mix " (proportions giving max density of agg) and "natural mix" (1 : 2.5 : 6.5, 1:3:6, 1 : 3.5 : 5.5). Results. 79 b. Size of aggregate; strength and density. Max stone size, inches 2H 1 Relative strength. Compression 1.00 0.83 Transverse 1.00 0.91 Cem reqd for equal strgth, relative 1.00 1.17 Relative density 1.00 0.96 1 A 0.72 0.75 1.33 0.93 EXPERIMENT AND PRACTICE. 1171 For abbreviations, symbols and references, see p 947 1. 79 c. Kind of aggregate. Sand vs screenings. Relative strengths and densities. Comp strgth Transv strgth Density Sand and stone 100 100 100 " " gravel 94 89 102 Screenings and stone 67 85 79 d. Graded mix gave density = 1.14 X density with natural mix; for equal strgth, graded mix reqd 0.88 X the cem reqd with nat mix. (This means an av saving of about 25 cts per cu yd of cone. Allen Hazen, Trans, A S C E, Vol 59, p. 150, Dec, '07.) 79 e. An excess of fine or of medium sand, or a deficiency of fine sand in a lean cone, diminishes strgth and density. 79 f. Strength and density max when mortar just fills voids. 79 g. Permeability. See Fig 10. " Little is known of the action of cone in resisting the flow of water." As betwn "diff proportions and diff sizes of the same class of materials, the laws of watertightness are somewhat similar to those of strgth." With given percentage of cem, the densest specimens are usually most watertight. With equal densities, the richest specimens are most watertight (See Fig). The ratios, how- ever, are very diff from those of either density or strgth, a slight diff in the composition producing a great effect upon the watertightness. ** IMflr kinds of agg produce very diff results in watertightness." Fig shows effect of pressure upon permeability. 79 h. Cone with Jerome Park stone and screenings gave very much higher rates of percolation thruout (max, 369 grams per min) than that with Cowe Bay sand and gravel. Cone with stone and sand gave about half the rates shown in Fig 10. 79 i. Permeability is sometimes greater with large and sometimes with small stones. Results especially erratic with the Jerome Park reservoir broken stone and screenings. 79 j . " Permeability decreases materially with age ; " increases much more rapidly than the thickness of the coiic decreases; less with sand and gravel than with stone and screenings; " sand ; " " " " stone " " screenings ; 80 SO. Richd H. Oaines, New York Board of Water Supply, A S C E, Trans, Vol 59, '07, Dec, p 159. 8Oa. Permeability and strength; Clay and alum. Specimens. Mortar, 1 : 3, Portland, Cowe Bay sand. Tensile testa on standard briquets; comp and tensile tests on 2" cubes. Age of specimens, 28 to 30 days. Pressures, 40 and 80 Ibs/Q". Results. (1) Replacing the mixing water with a 2.5 to 5 % (1 to 2 % sufficient) alum solution gave nearly complete impermeability. (2) Replacing 5 to 10 % of the sand with dried and finely ground clay, and (3) combining (1) and (2), gave still better results. The clay specimens (with and without alum) showed from 12 to 18 % gain in strength over those without clay. The process is based upon a theory of physico-chemical action between ions of the electrolyte (alum) and the colloid (glue-like) molecules of the clay. None of the processes hitherto in use, and examined, were found suitable for extensive use. Slaked lime slightly decreases permeability, but this advantage is more than offset by loss of strength. There is no chemical reason why this should be otherwise. 1172 CONCRETE. For Directory to Experiments, see pp 1135-9. 81 81. Prof E. Morsch, Zurich; forWayss and Freytag A.-G., Neustadt. "Der Eisenbetonbau, " Stuttgart, Konrad Wittwer, '08, to which the pages given refer. 81 a. Elastic relations, pp 27-32. Specimens; Square prisms; measured length, 35 cm (13%"). 1 part Mannheim Port cem, with 3 parta of a mixture of Rhine sand and gravel consisting of 3 parts sand, 0-5 mm; 2 parts gravel, 5-20 mm. (0.197"-0.78"). Water, 14 %. Each stress main- tained 3 mins. Some of the specimens tested in tension; the others in comp. Compression) in millionfhs of original length. ( 3 50 100 150 200 250 300 Zl S 1400 g 1200 | 1900 | 800 | 600 400 | 200 | ^ ^ 9 oV*>^ _.. J)rij |S ^' T5 ^- '' ^ x^ -60 Elongation Fig 11. Stress and Stretch. tf> Deformation, in millionfhs of original length'. 50 100 150 200 250 300 2.5 -50 50 100 150 200 250 300 Deformation, in millionth* of original length^ Fig: 12. Elastic Modulus. Results. I'll it stresses and stretches as in Fig 11. Ult ten- sions, Ibs/Q" : 3 mos, 149; 2 yrs, 224. Elastic Modulus, E, See Fig 12. With mix 1:4, for a given stress in comp, E was in general from 15 EXPERIMENT AND PRACTICE. 1173 For abbreviations, symbols and references, see p 947 1. to 20 % less than with 1:3. In tension, E was more nearly the same for both mixes. With water 8 %, for a given stress, E was in general from 10 to 20 % higher than with water 14 %. 81 b. Shear. Fig 13. Dimensions in centimeters. Prisms, 18 cm square, 40 cm long, p 40. Mixture of sand and gravel as in Expt 81 a. Fig 13. Shear. Plain. Specimen first cracked, as beam, at a. Pres then increased until shearing crack, 6, appeared. Ult av shear, Ibs/D"* No. of Mix 1 :3 1 :4 Water % 14 14 Age 2 yr 1.5 m Specimens 3 3 Observed 936 530 Calculatedf 980 550 Reinforced. The bars (1 cm diam) served merely to hold the speci- mens together, so that the pres could be increased as desired. The cone sheared first. Ult Av shear, Ibs/D" Mix 1 :4 1 : 4 Age 1.5 m 1.5 m specimens 2 3 Concrete 522 484 Steel 46400 50800 Water % 14 14 81 c. B'orsioii. p 45. Mix, 1 : 4. 4 solid cylinders, 79 to 98 days old; 26 cm diam; length under exp, 34 cm. Hexagonal heads. M = torsion al moment; R = radius of cyl; t torsional stress in extreme fibers (see p 500, this book) = 2 M/ir R3 t, in Ibs/D"; max, 275; mean, 243; min, 189. 3 hollow cyls, as above, 52 to 55 days old; inner diam abt 15 cm; r = inner radius. t = 2 M R/it (R* r), Z,.in Ibs/D"; max, 134; mean, 126; min, 112. The much higher unit strength of the solid cylinders as given by the formulas, is attributed partly to their somewhat greater age, but chiefly to the increase in unit stress from the circumf inward, owing to which the material near the center transmits more than its share of the torsional stress, and thus relieves the outer portions. * = J/ total force applied -f- area of one shearing surf, t From ult tensile strgth, t, and ult cornp strgth, c, of test pieces of same mix and age, and formula, shear = j/ t c. 1174 CONCRETE. For Directory to Experiments, see pp 1135-9. 81 d. Adhesion, p 49. Figs 14 and 15. Specimens. Cubes, 20 cm. Mix, 1 : 4; 10 to 15 % water; age 4 wk& Round bars 2 cm diam, Fig 15, spiral 10 cm diam ; wire 0.45 cm diam. Fig 14. Adhesion. Fig 15. Treatment. Bars pushed out. Pres rapidly increased to max. Results. Adhesion, means of 12 tests each, Ibs/D"; Fig 14, adhe- sion = 518 ; Fig 15, adhesion = 713. After overcoming the adhesion, considerable frictional resistance remained. 81 e. Ouctility and shear in reinforced concrete, p 00. Specimens. 4 reinforced hollow cylinders in torsion, as in Experiment 81 c, reinforced with spirals in the middle of their wall thick- ness. Spirals at 45, so placed as to be in tension under the twisting moment.. 2 cyla each with 5 spirals of 7 mm round iron, two cyls each with 10 spirals of 10 mm round iron. Diam of spiral, 21 cm. Stresses in iron, at instant of first cracking in cone, Ibs/Q"; max, 8960 ; mean, 8300 ; min, 7700. Stretch of iron and of cone at instant of first cracking in cone, av: 0.00027 X original length. Foregoing deduced from comparison with results obtained with plain cyls in torsion, Expt 81 c. Shear, Ibs/D" Max Mean Min At first cracking . . 620 480 347 At rupture 767 624 430 81 f. Specimens. 6 reinforced beams, 15 X 30 cm, 2 m span, p 62. Fig 16, p 1175. Dimensions in centimeters. Thickness of reinfg bars as below. 2 concentd loads, P P, equidistant from cen and 1 m apart. Mix 1:4; age 3 mos. Measurements on central length of 80 cm. Bendg mom constant thruout this length. Stretch of steel observed by means of two projecting lugs, at A, A, screwed into the bars. Stirrups provided near ends of beams. Beams kept wet, but tested dry. EXPERIMENT AND PRACTICE. 1175 For abbreviations, symbols and references, see p 947 1. !<-15->i Fig 16. Ductility. Results. Stretch per unit of length at instant of first cracking of cone: Cone, under Bars 10 mm (0.39") diam = 0.4 % " 16 " (0.63") " = 1.0 % " 22 " (0.86") " = 1.9 % Steel 0.00042 0.00033 0.00030 tension, max 0.00050 0.00040 0.00038 81 g. Steel and concrete stresses, p 97. Specimens. Flat reinforced beams, Fig 17. A, 3 beams B, S beams Fig 1 17. Stresses. Dimensions in centimeters. Bendg mom constant betw loads. Mix 1 : 4. Length, 2.2 m; span 2 m. Results. Failed by crushing of cone near and betw the 2 loads. Steel, 10 mm diam. Unit stresses, s, in steel, and c, in cone, in Ibs/D", deduced under the assumption of n = E g /E c = 15. After appearance of first cracks At rupture Age Steel s C 8 c 3 beams A Fig 3 " B " 17 13 mo 1.4 % 17 13 " 3.3 % 22300 20900 1315 54000 2250 39100 3180 4210 3 " A " 3 " B " 17 2 " 1.4% 17 2 " 3.3 % 18600 17000 1095 44800 1820 28000 2630 3000 , ' CO i 1. = t-j : 1- i s ! i 25 i u i U Fig 18. Shear. Dimensions in centimeters. 81 h. Shear in beams. 12 specimens, each consisting of a flat plate with two similarly reinfd ribs, Fig 18. Ribs of 2.7 m span normal t? the paper. Der Eisenbetonbau, p 158. 1176 CONCRETE. For Directory to Experiments, see pp 1135-9. Types of web reinforcement, neglecting slight variations. Fig 19, and 3d col of table below. c 4,6,7,10,12 Fig 19. Shear. Stirrups: 4th col, table below: a, thruout span; b, in one half of span; c, no stirrups. Bars: diam in mm: a, 18; b, 16; c, 3 bars 15, and 1 bar 18; d, 2 bars 15, and 2 bars 16. Beam No. 3 had 3 straight Thacher bars, 18 mm diam. Ends; 6th col, table below: a, hook; b, plain; c, 3 bars 45, 1 hooked ; d, 2 bars bent, 2 hooked; e, 3 bars 45, 1 plain. In No. 2 the webs were 0.28 m wide; in No. 8, 0.10 m; in the others, 0.14m. Age, about 3 mos. Heidelberg cem 1 : 4.5 (72 % Rhine sand 0-7 mm; 28 % gravel, 7-20 mm). Results. Stresses, in, Ibs s = tensile, in at support. 1 ,! /D". steel ; c = comp, in cone ; a At appearance of diagonal cracks which lead to = adhesion; v shearing, 1 S w rupture "o At rupture g | o 5 > :s * a * _3 PQ H w W W a V c s a V . 1 a b a a 17900 123 149 540 29300 198 239 1 S 2 a b a a 34300 234 142 824 44800 302 183 ?, a b .. b 19500 103 132 398 27800 146 187 3 "g 4 c c c c 36600 382 309 881 46300 476 384 4 ^ p 5 d b d d 17900 205 146 686 37000 418 299 5 "6 c a c e 232 186 795 42000 432 348 6 1 a b c 924 48600 448 318 7 *r> 8 8d b b d 15800 152 152 676 34800 324 324 8 g 9d b b d 22500 216 141 742 38200 352 251 9 I \ > ^ \ ' v ^- ^ "- 5 10 15 Percentage of hydrated lime to weight of cement. Fig 21. Permeability; Lime. 82 b. Coarser sand requires more lime, and vice versa. 82 c. If pressure is to be applied within a month, it will be better to use say 10 %, 15 % and 20 % respectively, instead of 8 %, 12 % and 16 % as recommended under Expt 82 a. 82 d. Lime paste occupies about 2% times the bulk of paste made with equal wt of Port cem, "and is therefore very efficient in void filling." The cost of large waterproof work may be reduced by using, with lime, a leaner cone than would otherwise be suitable. 83 83. Richard 1^. Humphrey, plain cone beams, cubes and cylinders, comp and transv strgths and the elas relations. "The Strgth of Cone Beams," U S G S Bull No. 344, '08. Tests to determine the effect, upon transverse and compressive strength, of (1) age of specimen, (2) consistency of mix, (3) character of aggregate. 83 a. Specimens. Unreinfd cone beams, cubes and cyls. Cem, a mix of 9 Port cems. Meramec R sand, "composed of flint grains having com- paratively smooth surfs." "The granulometric analysis, p 1178, shows the sand to be rather finer than desirable." 1178 CONCRETE. For Directory to Experiments, see pp 1135-9. Properties of sand and aggregates used. Meshes per inch of screen Size of mesh, ins 200 100 50 30 10 ' H % " 1% Sp Ibs/ voids Percentage passing sieve or screen Kr cuft % . , 47 51 2.84 4.17 6.5 10.5 21.1 37 60 81 100 41 1.59 2.29 3.2 4.4 8.5 20 58 99 100 33 1.0 43 79 95 100 Cinders 1.53 Granite 2.59 95 Gravel 2.45 102 Limestone 2.49 98 Sand 2.60 101 37 38 2.96 3.48 4.2 5.2 10.7 29 61 96 100 0.20 1.30 13.9 64.0 97.0 100 . Proportions, 1 : 2 : 4, by vol, except the cinder conc.which was nearer 1:2:5. All cone mixed in a mortar-driven cu-yd mixer, equipped with charging hopper. Mixed 2 rains dry, 3 mins wet; then dumped on cem floor, shoveled into barrows and wheeled to molding floor. Each batch sufficient for 2 beams, 8" X 11", 12 ft span, two 6" cubes and 2 cyls, 8" dia, 16" long. "Wet:" smooth and somewhat viscous immedy before dumping. Flows back from ascending side of mixer without tendency to break at top. When dumped, shows neither voids nor individual stones. Splashes when tamped. When finished, water stands M" to yf deep over surf of mold. ** Medium " : smooth, but tending to lump. Flows less smoothly than "wet," part flowing back smoothly and part breaking over in lumps. When dumped, looks somewhat lumpy, showing stones, but no voids. Stones evenly coated with mortar. No water collects on surf in mold. Surf easily finished with trowel. " Damp " ; granular. But little tendency to lump. Carried to top of mixer on ascending side; falls in individual stones and fragments of mor- tar. When dumped, shows stones and voids. Resists tamping. Compacts under hand tamping. Cannot be finished smooth with trowel. Cone placed in oiled steel molds, in 3 nearly equal layers, and hand- tamped. "Great care was taken to tamp all the cones in the same manner. " Treatment. All molds were removed at end of 24 hrs, and pieces trans- ferred to moist room. Sprinkled 3 times daily. The beams were so supported, just prior to test, that the sums of moments and stressed, then existing in the measd length, were equalized, so that all fibers, in that length, then had same length as when unstressed, and the deformations, within the measd length, were thus measd from zero. "0 0.5 1.0 1.5 2.0 2.5 G 1000 x Deformation per unit of length. Fig 22. Stress-stretch curves for different aggregates. Results. Stretches and comp stresses as in Fig. 22. Medium consistency. Age, 26 weeks. EXPERIMENT AND PRACTICE. 1179 For abbreviations, symbols and references, see p 947 I. Strength of Concrete. Results, in general, averages of 3 specimens. Beams, 8" X 11", 12 ft span Max comp strgth, Ibs/Q* Cylinders Neut Rupt modf 6 in cubes 8" dia, 16" long Water axis* > " > " > % 100 m 4 wks 26 wks 4 wks 26 wks 4 wks 26 wks Cinder Wet 219 43.3 175 246 1,256 2,320 1,081 2,021 Medm ..20.6 39.9 198 277 1,191 2,765 1,201 2,203 Damp . . Granite Wet Medm . . Damp 18.9 38.2 198 250 1,378 2,488 1,118 1,945 . 9.0 49.9 375 539 3,156 4,753 2,683 3,966* . 8.3 47.2 475 566 4,089 4,949 3,480 3.972J . 7.0 48.3 499 618 4,518 5,465 4,000 3,969t Gravel Wet . . . 9.7 49.9 391 435 2,299 3,814 2 060 3,486 Medm 8.9 48.4 451 520 3,547 4,808 2,961 3,972* Damp 7.9 47.5 426 496 4,612 4,884 3,407 3,969i Limestone Wet.. ..10.9 48.8 422 507 5,141 3,460 3,072 3,216 Medm 10.0 50.7 458 566 2,975 3,896 2,910 3,691 Damp 8.5 48.1 537 589 4,367 5,025 2,894 3.942J 84 - 84. R. G. Clark, Inst C E, Procs, Vol 171, '08, p 115. 84 a. Time of setting- increased by aeration and by addition of agg. A cem, which, neat, sets in an hr, will make a cone requiring 4 or 5 hrs to set. 85 85. Hanisch and Spitzer, Morsch, Der Eisenbetonbau, '08, pp 32-33. 85 a. Rupture modulus, 6 M /b d 2 , and direct compressive and tensile strength. Specimens. Cone, 1 : 3.5. Six plates, 268 days old, 60 cm (24") wide, 7.8 to 11 cm (3 to 4.5") thick; span, 150 cm (60"). Treatment. Plate broken transversely; comp and tension test pieces made from the fragments. Results. Stresses in Ibs / D". Rupture modulus compression tension max 775 5000 412 mean . . . . .682 4380 356 min 614 3640 284 Comparison of the values for tension with the rupture modulus shows that the formula, rupture mod = 6 M / b d 2 , is not applicable to materials in which, as in cone, the elas mod varies widely, and that the rupture moduli, obtained by means of the formula, are to be used only as a means of compari- son. 86 86. Richard L. Humphrey and Wm. Jordan, Jr., U S G S, Bull No. 331, '08. Results of Tests made at the Structural-Materials Test- ing Laboratories, St. Louis, '05-7. 86 a. Gravel screenings. In general the tensile and comp strgths of mortars seem to increase with density of screenings. *m = (depth of neut ax below top of beam) -=- (total depth of beam), t "Rupture modulus" = 6 M /bd 2 , Ibs / D"; M = moment under max load. t Cylinder did not break, 78 1180 CONCRETE. For Directory to Experiments, see pp 1135-9. 86 b. Stone screenings. In general, strgth of mortar was greatest with screenings most nearly uniform in grading. The strength of the stone itself, from which the screenings are derived, has an important bearing on the strgth of the resulting mortar. 86 c. Density of mortars is greatest with densest sand. 86 d. Sand mortars. Tensile, cpmpressive and transverse strengths were invariably much greater with dense sands than with those having a larger percentage of voids. 86 e. Greatest strgth obtained when sand is uniformly graded. 86 f. A "typical mix" of 7 Port cems, like the separate brands, reached max tensile strength in 90 days. Like the best of these, it maintained this max to 180 els, and its subsequent loss, at one yr and later, was no greater than for the best of the separate brands. 86 g. Age of briquet. Tests after 180 .days showed greater uni- formity than at 90 days and shorter periods. 86 h. After the 180 and 360 day tests, the strgths of all the sand mprtars were reasonably close to one another, showing that considerable variation in early strength does not seriously affect the later strength. 1000 180 Age, Days- Fig 24. 86 i. Tensile and Compressive Strengths of Portland Cement Mortars, neat and 1 : 3 standard Ottawa sand. See Figs 23 and 24. Each curve represents an av of 10 tests. EXPERIMENT AND PRACTICE. 1181 For abbreviations, symbols and references, see p 947 1. Specimens. The cem was a mixture of equal parts of 7 diff brands. See Expts 86 f, 86 g and 86 h. Test pieces, in molds, stored in moist closet 24 hrs; then kept in running water, abt 70 F, until tested. Tension briquets 1 sq inch section. Com- pression specimens, 2" cubes. Results as in Figs 23 and 24. 87 87. W. X. Willis, South & Western R. R. E R, '08, Jan 18; E N, '08, Feb 6, p 145. 87 a. Mica; water required; strength. Specimens. Sieve No 10 20 50 100 % of mica passing 100 29 10 4.5 Sand, Ottawa standd. Mortar 1 : 3 sand, or 1 : 3 sand and mica by wt. Results. Mica ; % of weight of sand 5 10 15 20 Voids, % in Ottawa sand 37 67 Relative sp gr of Ottawa sand 100 ... 80 Mixing Water required; relative. . 100 300 Tensile strength, 6 mos, relative . 100 64 62 59 40 The smoothness of surf of the mica particles renders their adhesion low. 88 88. Prof J. 1^. Van Ornum, Washington Univ, St. Louis; for Reinforced Concrete Constr Co., St. Louis. E N, '08, Feb 6, p. 142. 88 a. Adhesion. Specimens. Plain round steel rods, diams, }/% to 1 M",_ imbedded in 12" X 12" prismatic blocks of 1 : 2 : 4 cone, 90 days old. Medium steel rods imbedded 25 diams; high carbon steel rods, 40 diams. Results. See table below, in which, for Steel : s = Ult strgth, in thousands of Ibs/D"; s e = Elastic limit, in thousands of Ibs/Q"; e = Elongation, %; E = Elastic mod, in millions of Ibs/Q". for Steel and concrete: a = Area of imbedded surf, Q"; B = Adhesion, Ibs/D" of a; F = Friction after flipping, Ibs/D". Steel Steel and Cone. Steel s , e E a B F F/B Medium Max Av . 60.9 . 58.6 40.5 39.1 29.0 26.1 29.9 29.5 126.8 62.1 460 408 380 342 0.826 0.838 Min High Carbon Max Av 55.6 . 109.6 . 92.6 38.4 60.7 56.1 22.5 20.7 17.6 28.6 30.6 29.8 21.7 198.3 92.1 370 470 392 310 280 240 0.838 0.596 0.613 Min 83.9 53.1 15.7 28.9 32.7 330 200 0.606 In all cases, the total pull which overcame the adhesion exceeded that which brought the steel to its elas lim. 89 89. W. S. Reed. Engrs' Club of Phila., Procs, Vol 25, No 3, p 290, '08, Jul. 89 a. Friction of sand. Exp by More and Harris Tabor. Top pres, Ibs/Q", reqd to give 10 Ibs/Q" at bottom of box. 1182 CONCRETE. For Directory to Experiments, see pp 1135-9. Box 4" X 4" 6" X 6" Depth of sand, ins 2.5 5 7.5 10 Top pressure, Ibs / D" 12.5 17.5 34 42 11-5 .... 26 89 b. Fusing point of quartz samls. Exp by Prof Heinrich Ries, Cornell Univ. 3254 F. 9O 90. Eng News, '08, Aug 27, p. 238. 9Oa. Sea water. Charlestown, Mass, Navy Yard. Nonrein forced arches, built '01, by Bureau of Yards and Docks Tidal salt water, not highly polluted, but often freezing; range of tide 10 ft. Specification called for "continuous construction from pier to pier of the arch rings. " 3" mortar face, 1:1. Mass cone 1 : 2 : 4 for 2 ft back from face, 1:3:6 interior; "a standd cem and a local gravel." Probably porous. No special effort toward density or waterproofing. Specfn provided: "The contractor must furnish satisfactory evidence of the dura- bility in sea water of the brand of cem he proposes to furnish." The show- ing spandrel walls weie built after completion of arch ring. Dry, well- tamped. Serious disintegration. Damage mainly betw H W and L W. Cone backing considerably affected. 91 91. U. James Nicholas, Melbourne, Victoria. E N, '08, Dec 24, P710. 91 a. Electrolysis in cement mortars. Specimens. 16 cylinders, 8" diam, 8" high. Standd Port cem ; coarse sand, voids 51 %. Mortar tamped in 1 Yi" layers until a little water flushed to surf. Positive electrode, normally a 1" steel pipe, 12" long, lower end corked, immersed, in axis of cyl, to depth of 5" in cone. Treatment. Cyls set in fresh water < 28 days. 8 cyls tested with constant cnrrent of about 0.1 ampere; 5 with constant potential of about 115 volts (higher currents, one with reversed current); 3 not sub- jected to current. For current, cyls placed in 3 % salt solution in separate metal pails (which normally formed the negative electrodes), and con- nected in series. Cyls from 29 to 57 days old at beginning of test. Results. All cylinders, under current, cracked. Cracks attributed to accumu- lation and pres of liberated gases. Cracks at first hair-like, exuding mois- ture, which dampened adjacent surf. Cracks widened under continued current. With constant current, cracks appeared when resistance reached max. Resistance in general inversely proportional to percentage of sand. Cyls Nos 1 and 2 easily pried open. In Nos 2 and 9, steel pipe was rusted and pitted on outside, adjacent to crack. With (const potential) reversed current (No 12), no rust or pitting. Cyls not subjected to current were not cracked. They reqd about 20 blows, with heavy hammer and cold chisel, to break them. No rust. Constant Current, 0.1 ampere No of Specimen. Constant Potential, 115 volts No of Specimen. 1 2 9 10 13 14 5 6 3 11 12 15 7 Mix .. Sand,%.. Days* . . . Mins* . . . Ohmsf . . 1 :3 75 7 80 1 :3 75 7 90 1 :1 50 10 420 1:1 50 16 270 15 230 15 270 1 :0 28 2900 1 :0 15 1080 1:3 75 '5' 120 1:1 50 19 130 1:1 50 20 240 25 8 '9' 163 1:0 V 190 * To first crack. t Approximate maximum resistance. EXPERIMENT AND PRACTICE. 1183 For abbreviations, symbols and references, see p 947 I. 92 92. H," of Lafayette, Ind. Clay. In cone f to top in churning, and left Letter in E N, '08, Dec 31, p. 751. gravel contained 5 % clay, which worthless material near top of col. 92 a. Clay. In cone for cols, gravel contained 5 % clay, which floated of w 93 93. A. Q. Campbell, Ogden, Utah. E N, '08, Dec 31, p 751. 93 a. Grading and impermeability. Finish. 2 million gal rectangular reinfd cone water tank, 20 ft deep. Floor, 6" thick; walls 8 to 18". 1 cem, 2 ordinary sand, 4 stone (quartzite boulders, porphyry and flinty limestone) crushed to 1", with dust; "a heavy percentage of crushed dust and sand" ; machine mixt; "consistency that would almost pour." Floor laid in blocks about 15 ft sq, "allowing a half-lap of 2 ft;" walls in continuous 20* layers. Finish of 1 : 1 cem and crusher dust, applied with ordinary broom trimmed short. Clear water. No perceptible checking in surf. Apparently no seepage. - 94 - 94. John C. Trait twine. Jr. '09. 94 a. I>ensity of sand; shape of grain. 1 00 measures of rounded sand grains, or of angular crushed quartz grains, poured very slowly into 60 measures of water. Exps Nos 1 and 2 were made with sand grains; Noa 3 and 4 with crushed quartz grains. The left side of each diagram, Fig 25, represents the bottom of the vessel; and the numerals, 94, 121, etc., show the elevations of the surfs of sand and of water respectively, after the sand grains had been poured into the water. 121 Sand ii I 98 m 1 1 106111 H3 1 96 Mi 3 20 40 60 80 100 120 Elevation of sand and water surf aces above bottom of vessel. Fig 25. In No 4, the crushed quartz, in the water, was stirred, from time to time, during the pouring, in order to liberate any air which, in spite of the slowness of pouring, might have been carried into the water with the sand grains. The fact that the water stands at practically the same ht in 4 as in 3, indi- cates that no more air was carried down in 3 than in 4, and that the stirring merely brought the grains into closer contact than when left to themselves. 1184 CONCRETE. DIGEST OF SPECIFICATIONS, ETC. FOR GENERAL CONCRETE WORK, Pages 1186 to 1201. LISTS OF SPECIFICATIONS, ETC, USED. Alphabetical List. See Classified List, p 1185. (For additional abbreviations, see also p 947 Z.) AH, Algoma Harbor, Wis., Caisson breakwater, etc, U. S. Engrs, '08, Jan 24. BB, Breakwater, Buffalo, N. Y., Emile Low, U. S. Engrs A S C E, Trans, '04, Jun, Vol 52, p 73. BR, Black Rock Harbor and Channel, Buffalo, N. Y. Ship lock walls. U. S. Engrs, '07, Dec 19. Bn, Burlington, Vt., Mechanical filter plant, Hering and Fuller, '07. Ch, Chicago, '08; proposed amendments to Building Code of '05-6. Cl, Cincinnati, O, Geo. H. Benzenberg; a, Filters, etc, '05; b, Head-house, etc, '06. Co, Columbus, O, John H. Gregory; a, Filters, etc, '05; b, Pumping station and intake, '06. CR, Columbia River impvmts, Ore. and Wash., Canal. U. S. Engrs, '08, Aug 1. CS, Concrete-Steel Engineering Co., Edwin Thacher, genl specfns; Melan, Thacher and yon Emperger patents, '03. F, Wm. B. Fuller, Filters, specification received, '08. FP, Pensacola, Fla., repair and protection of sea walls. U. S. Engrs, 08, Apr 18. FW, Fort Williams, Me., Wharf, Ship Cove. U. S. Engrs, '08, April 14. O, General practice. lib, Harrisonburg, La., Lock and dam No. 2. U. S. Engrs, '08, May 13. IM, Illinois & Mississippi Canal, Locks, Eastern Section. U. S. Engrs, Jas. C. Long, Western Soc of Engrs, '01, Apr, Vol 6, No. 2, p 132. JC, Recommendations in Report of Joint Comm of A S C E, A S T M, Am Ry Eng& M W Assn, and Assn of Am Port Gem Mfrs, '09, Jan. L, Louisville, Ky., Building Ordinance, '07. JLp, Liverpool Harbor Improvement, Geo Cecil Kenyon, A S C E, Trans, '04, Jun, Vol 52, p 36. Lv, Louisville, Ky., Southern Outfall Sewer, '07. Me, McCall Ferry dam, Susquehanna River, Pa., '08. Mh, Manhattan, Borough of , Regulations of Bureau of Bldgs, '03, Sep. Ms, Massachusetts Legislature, Acts and Resolves of the , '07. NO, New Orleans, La., Water Purification Stations, '06, Sep 5. NY, New York. Building Code approved '99, Oct 24, with amendments to '06, Apr 12. OD, Ohio R below Pittsburg, Pa., Dam No. 19, Abutment. U. S. Engrs, '08, Jul 25. Ph, Philadelphia. Regulations of Bureau of Bldg Inspection, approved '07, Oct 8. Engrs' Club of Phila., Oct '07, Vol 24, No 4. SE, Superior Entry, Wis., South Pier, Clarence Coleman, Asst Engr. Report. Chief of Engrs, U. S. A., '04, Part 4, pp 3779, etc. TR, Tennessee R, below Chattanooga, Tenn., River wall. U. S. Engrs, '08, May 27, TAT, Taylor and Thompson, "Concrete, Plain and Reinforced," publisht by John Wiley and Sons, New York, '05, pp 33-37. Un, Underwriters, National Board of Fire , Building Code recommended, New York, '07. WII, Waddell and Harrington, general specifications, received '07, Dec. Wv. Wellsville, O., Navigation pass, Dam No. 8, near . U. S. Engrs, '08, To, Yonkers, N. Y., covered masonry filters, '07. CONCRETE SPECIFICATIONS. 1185 Classified List. See Alphabetical List, p 1184. U. S. Govt work, AH, BB, BB, CB, FP, FW, Hb, IM, SE, Wv. Breakwaters, AH, BB, SE. Sea walls, FP, SE, TB. Locks and canals, BB, CB, Hb, IM. Harbor improvement, Ip, SE. Wharves, FW, tp. Dams, Hb, MC, O, Wv. Pumping stations, etc, Ci b, Co b. Filter plants, Bu, Ci a, Co a, F, NO, Yo. Sewers, Iv. Bridges, CS. Building codes, Ch, L,, Mh, Ms, NY, Ph, Un. General, CS, JC, T & T, WH. Outline of Contents. Subject Parag. Cement 1 Brand 1 Requirements 2 Shipment 3 Storage 4 Sand 5 Size . 6 Screenings 7 Aggregate Kind 8 8 Requirements 9 Sizes 10 Storage 11 Cinder concrete l: Large stones 15 Proportions, see p 1086. Measurement of ingredients .... 21 Consistency 22 Mixing 28 Hand vs machine 28 Forms 34 Lagging 34 Tie rods 36 Placing, churning & ramming . . 37 Layers 40 Joints 46 Under water 52 During rain 54 During freezing weather 55 Moistening 59 Forms, removal 61 Freezing weather 65 Surface finish, etc 66 Waterproofing 78 Artificial stone 80 Strength, etc required 81 Ultimate compressive 81 Ultimate shearing 82 Max allowable loads 83 Compression 84 Tension 91 Shear 92 Elastic modulus 93 Adhesion, see p 1111, and p 1196, H 113. Subject Parag. Safety factors 95 Reinforcement 96 Bars, condition 96 Shape 97 Twisted 98 Round, corrugated, etc 99 Iron and steel, requirements. . 100 Ult tensile strength 102 Ult compressive strength .... 103 Fracture 104 Elastic limit 105 Elastic modulus 106 Elongation 108 Bending test 109 Max allowable stresses 110 Adhesion 113 Length and lapping 116 Protection 117 Permits 118 Clearance 119 Fireproof bldgs 120 Girders and columns 122 Cinder concrete 127 Columns 129 Rods tied together 133 Requirements 136 Cross-section area 138 Eccentric loading 142 Attachment to girders 143 Hooped 144 With structural steel 150 Beams and floors . v 151 Assumptions, theory 151 Stresses 155 Adhesion 156 Span.. 158 Shrinkage, etc 159 Shear . 160 Cement finish 163 Web reinforcement 164 Steel in comp side 165 Slabs acting as flanges 167 Moments 174 Continuity 176 Tests.., ..183 Cll 1186 CONCRETE. For lists of Specifications for Concrete, see pp 1184, 1185. In order to compare intelligently the requirements of diff specfns, the character of the work involved must of course be taken into account. DIGEST. Cement. 1. Brand. Portland or natural, NY ; Port just under lower miter sill, nat elsewhere in foundations, Port in lock walls except for a backing, 2 ft deep, at base, Port and nat bonded together, IM ; for reinforced work, Portland, G; Am Port, CS, BB, Hb, FW; "Universal" Portland cement, SE ; cem made by mfr of established reputation (in successful opera- tion not less than 2 yrs, F), brand in continuous successful use (in America, F) for the last 5 yrs (3 yrs, CS) G ; in satisfactory use in similar quantities by U.S. Engr Dept at Large, TB; of tried uniformity, in use not less than 3 yrs in similar climate, CB, Hb; only one brand to be used, G; except for good reasons, F ; only one brand in any monolith, FP. Portld in reinfd work and where subject to shocks or vibrations or to stresses other than direct comp; nat in massive work where weight is more important than strgth, and where economy is the governing factor; puzzolan only for foundations underground, not exposed to air or to running water, JC. 2. Beqniremeuts. For Strengths, etc., see Digest of Specfn for cem, by A S T M, p 940, Report of Board of U. S. Engr Officers, Prof'l Papers No 28, Corps of Engrs, U.S.A., '01, p 937, and Digest of Specfn by Engng Standards Comm of Great Britain, p 940. For tests, see Digest of Specfn of A SC E, p 942. Slow setting, FP; must have been tested < 6 mos, > 12 mos, prior to issue of permit, Ii;must meet requirements of Prof'l Paper No. 28, Corps of Engrs, U.S.A., '01, p 940, BB, AH, TB, CB, FW, Wv, FP, HD. 3. Shipment. Packages to "contain either 380 Ibs or some even division of 380 Ibs, " I^v ; in cooperage or in cloth bags, NO ; bag, 93 Ibs (94 Ibs, Co) net, bbl = 4 bags, NO ; in bbls, lined with paper, CB, WH ; in cloth bags, Ci ; may be delivered in paper bags, Wv. 4. Storage at site of work. In weather-tight bldg, with floor raised (< 6", T & T) above ground, G ; and holding < 2 wks' supply under ay con- ditions of work, Ci ; cem in bags may be used after 3 mos storage, rejected if it becomes lumpy or otherwise deteriorated within that time, BB ; cem, kept over winter, re-tested before using, Wv. Sand. 5. General. Silica, hard, clean, sharp, G. Reasonably clean, coarse, F ; water worn, voids = 35 %, SE. "Sharpness'^purposely omitted, TAT. River sand, Ci, a. 6. Size. Well graded, with fine, medium and coarse grains, F, l,v, NO, Co. Coarse, or coarse and fine, mixed, CS, T & T. Coarse pre- dominating; coarse preferred at double or treble cost, T fc T. Medium, Ci, a. Largest to pass screen of %" mesh, G. > 10 % coarser than %", NO ; < 50 % retained on No. 30 sieve (holes 0.022" Q),WH. > 40 % to pass No. 50 sieve (2500 meshes / D"), Hb. > 3 % very fine, NO, Co, Ci, a. > 5 % very fine, Bu. Foreign matter (clay, loam, sticks). None, CS, T&T; > 2% NO, > 3 %, Co, I,v ; > 5 %, Wv, OI>, TB, CB, Bu. > 10 % clayey, AH. > 3 % clay, etc, > 2 % mica, F W ; > 4 % free loam, Hb ; sand may be moist, not wet, TB ; stored on a board platform, CB ; or in bins, Wv. 7. Screenings. Crusher dust, passing Y\' screen, from broken stone, may be substituted for part or all of the sand, T fc T ; "screenings & crusht stone may be substituted for sand and gravel under special conditions," F; screenings permitted, BB, CB; if passing M" screen, TB; screenings preferred to sand, AH. Aggregate ("Ballast"). 8. Kind. Sand grit, gravel or broken stone, BB ; gravel or broken stone, G; or both, BB; gravel, I/v; (see Screenings); sea-washed gravel, Lp; water-worn pebbles of igneous rock, SE; clean stone, gravel, broken hard bricks, terra cotta, furnace slag or hard clean cinders, Un ; broken stone referred, gravel permitted for interior of piers, pedestals and abuts, WH ; in stone, AH. prefer] broker CONCRETE SPECIFICATIONS. 1187 For abbreviations, symbols and references, see p 947 I. 9. Requirements. Clean, hard, durable; free from dust, loam, clay and perishable matter; washed or screened if reqd, CJ; approx cubical, CS, AH? free from long thin pieces, BR, WO, CS; < 125 Ibs/cu ft, FP; < 130 Ibs/cu ft, Hb ; voids = 31 %, SE ; drenched before using, ; but not to carry water, Wv; kept thoroly sprinkled, IM, Hb. 10. Sizes, inches: min, X, G; Ys, FW, Me; max. %, Iln ; 1 J^, Bii; 2, G; 2 1 A, Hb; 3, XO, Co, Ci, a, FP, SE; gravel, 3, F; stone, run of crusher, F, Me, AH; 1 to 2^, according to grade of work, AH; for foundations, 2 ; for superstructure, \% ; for beams, cols and girders, 1, I; gravel, < 90 % over IK, > 10 % sand, Hb. 1 cubic foot of stone, gravel or sand grit contained Agg cu ft Ibs cu ft Ibs cu ft Ibs Stone;., .coarse, 0.63 53.8; fine, 0.33 30.4; dust, 0.11 11 Gravel;. .. pebbles, %", 0.80 81.5; sand, 0.29 29.2; Sand grit; gravel, l / 8 " to %", 0.47 47.2; sand, 0.59 59.3; BB. 11. Storage. Stored on wooden platforms, CR, Wv ; or in bins, Wv. 12. Cinder concrete. Allowed only for floors, roofs and filling, Ms. Reinfd cinder cone to be used only upon special permit of Inspector of Bldgs, Lu 13. ' ' May be used for all bldgs in which fireproof construction is mandatory by this Chapter, or where ordinary constr, mill constr or slow burning constr may be used," not for cols, piers or walls. Clean, thoroly burnt steam- boiler cinders; mix, Port cem, not poorer than 1 : 7. Cinders must pass 1" sq mesh, Ch. 14. "All other special requirements and methods of calculation for reinfd cone as reqd in this Chapter shall modify and regulate the use of cinder cone in bldgs, " Ch. 15. Large Stones. Hard, sound, durable, as large as can be conveniently handled; washed clean; placed wet; one dimension < 12"; no dimension less than 4"; no stone less than 2" from faces exposed in finished work, cone joggled into place with light rammers, Co. 16. > 100 Ibs, < 3" from forms or from other large stones. (From Specfn for a Soldiers' Home.) 17. Permitted in walls > than 18" thick, diam > quarter of the thick- ness of wall, vol of stone > one-fifth vol of wall, Yo. 18. One-man stones and larger, roughly cubical; long flat pieces to be broken or rejected; stones somewhat uniformly scattered thruout the work; < 8" apart, < 2 ft from crest or down-stream face; dropped separately into bed of wet cone, pounded down if necessary; if necessary, cone spaded under and around the stones; each stone to be covered with cone before other stones are deposited. Use as many stones as possible without violating these conditions, Me. 19. "Plums." Stones, from one-man to several tons (sometimes from old masonry), aggregating abt 30 % of the finished work < 1 ft from wall surf. Set in top layer of cone and so as to form bond with next layer by projecting upward into it, L: by machine when amount of work exceeds 1000 cu yds, S; by machine in general, TR, lib, WH ; "preferably by approved mixers of the continuous type which automatically measure and feed the correct proportions in small streams into the mixing chamber, " F; by batch machine, Bu, Ci, b ; " mechanical batch mixer . . , except when limit- ed quantities are reqd or when the condition of the work makes hand mixing preferable; hand mixing. . .only when approved by the Bureau of Bldg Inspection," Ph; batch mixer, Hb, R, Wv, FW; < 100 cu yds per 8 hour day.'FW ; batch mixers preferred, continuous mixers only by special written permission of engineer, WH. Method. Materials mixt dry before adding water, C5S, JfY; turned _< 100 times, Ci, b. "In all mixing the material shall be measd for each "batch;" agg, if hot and dry, to be wetted before going to mixer, Ph. One batch completely discharged before the next is introduced. Not less than 25 revolutions for each batch, turning cone over not less than once each revo- lution, Un ; order of charging, 1st gravel, 2d cem, 3d stone, 4th water, each batch turned < 2 mins, > 9 revolutions per min, extra turns to be given when time permits, IM. 29. Batch mixing. Cem (2 cub ft per batch) mixt into a rough paste on platform. First pebbles, then sand and cem paste, then broken stone, dumped, thru hole in platform, into box on car below. Box dumped into mixer; 5 to 10 revolutions; 7 to 14 batches per hr. With 14 batches, 12 men reqd for ramming, BB; first sand, then cem, then agg, then water. TR, Ol. 30. Hand mixing. Cem and sand mixt dry; wet stone added; water added, S. Cem and sand mixt dry, water added, agg spread not more than 6" thick, sprinkled, mortar spread over agg and mixt, Ph. Cem and sand mixt dry, water added, mortar mixt, agg (wetted) added, all mixt, Hb; mixture of sand and agg first spread in thin layer on a timber platform, cem spread on top, mixt dry, turnd over as water is gradually added; broken stone, if used with gravel, is added wet to the wet mass, WH. 31. On tight platform, large enough for 2 batches of not over 1 cu yd each. Cem and sand spread in thin layers and mixt dry until of uniform color. Then use either one of 3 optional methods, as follows : (1) Mixture of cem and sand spread upon layer of stone; CONCRETE SPECIFICATIONS. 1189 For abbreviations, symbols and references, see p 947 I. (2) Stone shoveled upon mixture of cem and sand. In (1) or (2), turn 3 times, adding water in first turning. (3) Mixture of cem and sand made into mortar and spread upon stone. Mass of mortar and stone turned twice, T & T. 32. In any case, result must be a loose cone of uniform color and appear- ance, stones thoroly incorporated into mortar. Consistency uniform thru- out, T & T. 33. "As the gravel box was being rilled, the cement was added to it gradually, so that, when the gravel box was full, the cement box was empty. The box was then removed, and the heap leveled off to a uniform thickness of > 1 ft, and was then mixed by casting backward and forward twice," water added at time of second casting, Lp. Forms. 34. Lagging. Of well seasoned boards, 2" thick, drest all over, tongued and grooved, Co, b ; 2" X 6" pine, drest on all sides, Hb ; boards planed on one side and two edges; one edge slightly beveled and placed against the square edge of the next plank, Yo ; boards preferably 2" X 6", dressed -and- matched flooring, WH ; forms for exposed faces, of planed lumber, tongued and grooved or beveled; wall forms to be braced, and, where possible, to have their sides wired together, i ; butt joints square, and either on posts or reinfd, lib; joints, showing spaces, to be filled with stiff clay immedy before placing cone, lib. Used lagging, if not scarred, may be used again; but, for exposed work, must be cleaned and oild, Hb. Posts. Generally 3" X 8" pine, drest on both edges, of full height of wall, > 4 f t apart, Hb. Centers and forms to be wet, IM ; if reqd, before laying, XO, Ci, b ; or oiled, XO. According to circumstances, forms to be wetted (except in freezing weather) or greased with crude oil, before placing cone, T & T ; oild just before use, Hb; painted or oild before re-using, CB; dampend just before placing cone and kept damp until work has hardened, TK, Wv. For removal of forms, see p 1191. 35. On up-stream face of dam, molds need be only smooth enough to give good substantial work, free from voids. On crest and down-stream face, molds must have planed surfs, so as to leave the finished work smooth, Me. 36. Tie rods, left in cone, must not come nearer to cone surf than 2", CB; projecting ends of iron bolts and rods to be cut off smooth and flush with cone face, I$K. AH ; not chiseled, but sawn or otherwise removed without jarring the work, AH; aids for holding molds not to be inserted within 4 ft of top of walls, BB ; no bolts, etc, to show in the completed work, OI>. Placing, Churning and Bamming. 37. IXIght work prohibited in general, TB. Time of placing ; cone must be placed within 30 mins after mixing, AH, XO, Ci, b ; > 30 mins ' ' betw wetting the cem and the undisturbed cone in final place," F ; before initial set, TB, O, CB, Wy, FW, Hb, Bu ; after mixing, mass kept in motion until placed in vehicle for transportation, TB. No s'etempering or rehandling permitted, TB, CB, WO, Bn, Co, Ci,b, JC. Cone, in which the materials have separated, must be remixt (by hand mixing, BB, AH); before laying, T fc T. Manipulation. In very wet cone, air must be churned out, stones workt back from face, and cone workt under rods, etc., CJ; by means of thin steel or iron blades, about 4" X 6", with handles of adjustable length, so that workmen need not stand in cone, 5fO, Ci,b. Cone to be joggled or worked into place by light ramming, Bu, Co ; ram until mortar comes to surface, AH, BB ; until all voids are filled and water flushes to the surf, CS; one tamper to not more than 2 cu yds per hr, BB; rammers with striking area not less than 36Q", weighing not more than 10 Ibs, Co; face 6" sq, weight, with handle, about 20 Ibs, CB ; 30-lb iron-shod rammers, face area not more than 30Q", IM ; 40-lb rammers, SE ; cone placed without ramming, FP. 1190 CONCRETE. For lists of Specifications for Concrete, see pp 1184, 1185. 38. Dry cone moistend by sprinkling, not pouring, R. 39. Cone must be continuously worked around reiiifmt, with suitable tools, as put in place. Complete filling of forms, and subsequent puddling, prohibited. Partly set cone must not be subjected to shocks, Ch. 40. Placing-, in layers. Care taken to remove all scum, arising from the cem, before laying the next layer, lp, JC. 41. Cone dumped from receiving box or car, or shoveled directly into place, use of slides and shutes forbidden, OD, Wv, FP, TB, CB : not dropt further than 6 ft, FP ; 3 ft, Wv. 42. No walking on finished wall until set, OD, Co. 43. Thickness of layers. Not over 6", Wv, BB, OD ; about 6", CB; about 6" after ramming, TB: 6 to 8", CS; > 6", F; > 4", SK: with dry mix, on slopes, > 4", F ; > 4" in foundations, about 6" in back walls, IM; > 9", Hb; > 12", WH; such that each layer can be incor- porated with the preceding one, T fc T. 44. No layers permitted, Bu, Co ; layers not run out to thin edge, FP ; each layer completed (rammed, CB) before the next is laid, FP, CB; each layer of a day's work laid before the layer next below has set, TB. 45. On rock foundation. Rock cleaned and washed with wire brooms, roughened if reqd, covered with thick neat cem grout, CB : bed of wet mortar, FW; }/< thick, TB; cone anchored to rock with steel rods, if reqd, CB. Joints. 46. Avoidance of horizontal joints. Walls, etc, built in alter- nate sections, so short that they can be constructed as monoliths; these sections keyed together by vertical tongue-and-groove joints, O for gov't specfns; joints continuous from foundation to coping, CB ; " joints shall be formed betw adjoining sections of cone for 4 ft down from the deck, by a layer of tarred paper," BB ; dovetailing to have a thin coat of mortar, 1 : 5 or weaker, to set before new cone is placed against it, Hb. 47. Joints between old and new work. Exposed surfs shaded and kept moist until work is resumed, CB ; chipped or broken edges cut away, CB ; old surf to be left stepped, to form bond, and to be cleaned and wet before adding new work, FW, O ; cleaned with stiff wire brush and stream of water, FP, BB, Hb ; if reqd, F,L 32 F., IJii, AH, BR, < 32 F, O; < 30 F, CR, < 34 F., TR, FP ; when likely to freeze before set, Wv ; before final set, OI> ; before set sufficiently to prevent injury, BR, CR. Cone, frozen in place, to be removed, Uii. No cone to be laid when temp is below 20 F; water to be heated when temp is below 35 F, Me. Use of icy materials prohibited; placed cone must be protected against freezing, Ph. 56. Natural cement concrete must never be exposed to frost until thoroly hard and dry, T & T. 57. "No cone, except that laid in large masses, or heavy walls having faces whose appearance is of no consequence, shall be exposed to frost until hard and dry. Materials employed in mass cone in freezing weather shall contain no frost. Surfs shall be protected from frost. Portions of surf cone, which have frozen, shall be removed before laying fresh cone upon them." T & T. 58. Forms, under cone placed in freezing weather, " to remain until all evidences of frost are absent from the cone, and the natural hardening of the cone has proceeded to the point of safety ." Cli, Ph. Moistening. 59. Moistening 1 . Freshly laid cone to be protected from the sun (by boards or tarpaulins, FP, Hb, IM;) and kept wet, Me, IM ; < two weeks, or until covered with earth, F ; < 10 days, SE, AH ; 6 ds, CR ; 3 ds, FW ; 48 hrs, BR ; until set, Wv ; until hard set, Hb ; unfinished surfs until work can be resumed, CR; with wet tarpaulins < 3 days, CR. When a section of wall is completed, coping to be covered with a thick layer of wet sand, mass'of wall kept sprinkled until cone is thoroly set, IM ; cone to be drenched twice daily, Sundays included, for a week after placing, in hot weather, Ch, Ph. 60. Moisten by sprinkling with fine spray at short intervals or by covering with moistened burlap, or etc, O. Removal of forms. 61. Forms must be left in place < 4 days, IM ; < 7 ds; longer if reqd by engineer, I,v ; 72 hrs, OI> ; 48 hrs, AH, BR ; until cone has stood at least 36 hrs, WH ; until renwval is authorized by engineer, or until cone has become hard, Ci,b ; until cone can carry its load safely, Ms; forms removed after 48 hrs, SE. 62. Props, under floors and roofs, to remain in place < 2 weeks. Forms, for cols, < 4 days; for slabs, beams and girders, < 1 wk and at least until the floor can sustain its own weight. "No load or wt shall be placed on any portion of the constr where the said centers have been removed." Ch, Ph. 63. Time for removal of forms and centering, 24 hrs to 60 days, depending upon temp and other atmospheric conditions and upon the commissioner of bldgs, Un. 1192 CONCRETE. For lists of Specifications for Concrete, see pp 1184, 118d. 64. Not until cone is hard. Min time, days: Apr 1 to Dec 1 Dec 1 to Apr 1 Slabs and lintels, cols and monolithic walls 10 15 Posts and bottom supports for joists, beams and girders 14 21 Li. 65. Forms, under cone placed in freezing weather, "to remain until all evidences of frost are absent from the cone and the natural harden- ing of the cone has proceeded to the point of safety." Ch, Ph. Surface finish, waterproofing-, etc. 66. Finish kept smooth by manipulation during placing, not by subse- quent plastering, etc. Cone, free from large agg, to be placed next the mold, and prest back from mold by means of a flat shovel, inserted betw cone and mold (mold sprinkled with water, II 11), cone rammed with an iron rammer, lower face 2" X 6*, AH, BR ; finish by working gravel back from face by means of forks, lib: or shovels, FP; faces rubbed smooth, Tit. lib: with a piece of wood or soft stone, TR ; voids filled up with mortar, lib. TR, CR; plastering permitted only for an occasional and accidental cavity where the plastering is not apt to be disturbed by frost, CR. See p 1193, If 79. 1 : 3 Port cem mortar, placed simultaneously with backing, R. For wall, 1 : 2 Port cem mortar, very dry, 1 >#" thick, TR. 67. For exposed faces, forms to be removed before cone has hardened; surf (1) rubbed with mortar of 1 vol Port cem, 2 vols sand, applied with a burlap swab and brushed down with a plasterer's brush, or (2) rubbed with stiff wire brush and a thin coat of neat Port cem grout, brushed down with plasterer's brush, NO, Co ; smooth finish of sides produced by thoro ramming against inside surfs of molds, &E. 68. Surfs, not built against forms, screeded and troweled to smoothness, NO. 69. Voids or other imperfections, appearing upon removal of forms, to be corrected at expense of contractor, who shall remove and replace unsatis- factory work if reqd, F. 70. For floors and roof of mixing tank. Stiff mortar, of 1 vol Port, 1 vol sharp stone screenings to pass %" ring, free from dust, loam, etc, 1" deep, laid before cone has initial set. Screeded, floated and troweled to smooth surf. Covered and sprinkled 3 days, Co. 71. Pronienades and tops of parapets finished with a layer of mortar ~> %" thick, consolidated with the cone "by superimposing heavy planks 4" thick and ramming them with 40-lb cast iron rammers until their ends are in contact with the ends of the molds," SE. 72. For piers, pedestals, abutments. Surfs exposed to air or water, 1 J^" Port cement mortar, 1 cement, 2 sand, carried up simultane- ously with the cone, 10 or 11" in depth at a time, by means of W steel plate forms, 12" wide, 4 to 5 ft long, placed around the work, 1 ]/y from the forms, and blocked out every 12" by wooden blocks, the ends of the plates lapping slightly, WH. 73. For inverts, 1 cem, 2 sand, not more than }/(? thick, laid at same time as cone, I.V. 74. Moldings, cornices, etc. Plastic mortar placed against finely constructed molds, as cone is being laid; no exterior plastering permitted, SE, T & T; no plastering to be done unless expressly permitted, F. 75. Top finish. Cone brought up to 3 J^" from reqd elevation; while this is still unset and plastic, 3" of finer cone added, tamped and kneaded to form a monolith with the underlying cone; then Y loaded area 0.325. s*= 650 in columns, length > 12 diams 0.225 . = 450 with longitudinal reinfmt only 0.225. =450 hooped 0.270. = 540 , with 1 to 4 % long'l bars . . .0.325. = 650 with structural steel col units thoro- ly encasing cone core 0.325. = 650 Rupture modulus (elas mod, E, constant) 0.325. = 650 adjacent to supports, (E constant) 0.375. = 750 Pure shear (no comp normal to shearing surf; reinfmt tak- ing the normal tension) 0.060. = 120 Shear, combined with equal comp 0.162. = 325 Adhesion, plain bars 0.040 . = 80 drawn wire . ...0.020. = 40 JC. 84. Compression. See also II 146, p 1198. A, exclusive of temp stresses, B, including stresses due to temp changes of 40 F In arches for bridges, Ibs / Q": A for highways and electric railways 500 600 for steam railways .400 500 85. On first-class Port cem cone, with agg properly graded: 1 : 6 or less, 60,000 Ibs / sq ft = 417 Ibs / D"; 1 : 5 or less, in beams or slabs 500 "In case a richer cone is used, this stress may be increased with the ap- proval of the commissioner to not more than" 600 Ibs / n", Ms. * s = ult comp strgth in Ibs / D" at 28 days when tested, under labora- tory conditions, in the form of cyls 8" diam, 16" long, of same consistency aa used in the field. t When s = 2000 Ibs / Q". 1194 CONCRETE. For lists of Specifications for Concrete, see pp 1184, 1185. 86. Portland, 1:2:4.. 230 Ibs / FT , 1:2:5 '.'.'.'.'.'.208 " Rosendale or equal, 1 :2:4 125 1:2:5 Ill " N Y.* 87. Portland, Ibs / Q". Mix, 1:2:4 1:2.5:5 1:3:6 machine-mixed 400 350 300 hand-mixed 350 300 250 Natural 150 Cinder, 700 ; Port, in reinfd cone; direct, 0.2 X ult; in bending, 0.35 X ult. Oh. 88. Port, direct, 350 Ibs / Q"; in reinfd work, 350 Ibs / G" simultane- ously with 6000 Ibs / D" tension in steel, tin. 89. Port, direct, 350; in bending, 500, Mh. Aggregate 90. Port, Stone or gravel Slag Cinder In bending 600 400 250 Ibs / Q* Direct, in cols length > 15 diam 500 300 150 In hooped cols, 1000 Ibs / D" on area within hooping, Ph. 1:2:4 1:2:5 1:3:6 Port 700 650 600 Ibs / D" Nat 400 ... ... "I* 91. Tension, Ibs / D". A, exclusive of temp stresses, B, including stresses due to temp changes of 40 F. A B In reinforced arches 50 75 In reinforced slabs, girders, beams, etc OS. On diagonal plane, 0.02 X ult comp strgth, Oh. ~~ 92. Shear. Ibs / D". 75, CS ; 50, Mh ; 60 when uncombined with comp upon the same plane "unless the bldg commissioner with the consent of the board of appeal shall fix some other value," Ms; stone or gravel cone, 75; slag, 50; cinder, 25, Ph. Elastic modulus. 93. 1,500,000 Ibs / D", CS. Adhesion. 94. See p 1111, and p 1196, H 113. Safety factors. or. , , ultimate load Safety factor = - -5-^ T . allowed load 95. At end of 1 mo, in subways and girder bridges for highways and electric rys, also bldgs, roofs, culverts, sewers, 4; in subways and girder bridges for steam rys, 5, OS. Port, in reinfd cone, comp, direct, 5; in beams, 1/0.35; Oh. In reinfd beams, 1 for dead load, plus 4 for live load, = 5; In iron or steel in latticed or open work cols, beams or girders, encased in cone which extends < 2" beyond metal (with no allowance for the cone), 3 It. Reinforcement. 96. Bars, unpainted, but free from scale, rust and grease, r. 97. Shape. Plain round or square, or corrugated, I 1P 0t " 00 ,, , T & T. tensile strgth 109. Bending test. Cold, F, I^v, Bu, CS ; hot, cold or quenched, NO, Co,a; 180 about a diam = the thickness of the bar, F, WO, Bu, Co, CS; (before deforming, F); about a diam = twice the thickness of the bar, IiV ; (after deforming, F) ; soft steel, flat, CS ; cold, 90 over a diam = twice the thickness of the bar in steel > %" diam; over a diam = 3 X thickness of bar in steel > %" diam, Ch. Maximum stresses allowed in steel. Stresses in Ibs / Q" unless otherwise stated. 110. Tension, 16,000, Mh, Ph, .1C; (iron, 12,000, Ph); one-third elas lim, but not over 18,000, Ch ; mild, 12,000; medium, 15,000; high carbon, 18,000, L. 111. Shear, 10,000, Mh ; 12,000, Ch. . . elas mod in steel __ 112. Comp = comp in cone X - , Ch. elas mod in cone "In arches, the steel ribs under a stress not exceeding 18,000 Ibs per square inch must be capable of taking the entire bending moment of the arch with- out aid from the cone, and have flange areas of < the 150th part of the total area of the arch at crown. The actual stress when imbedded in and acting in combination with cone shall not exceed 20 times the allowed stress on the cone." 79 1196 CONCRETE. For lints of Specifications for Concrete, see pp 1184, 1185. "In slabs, girders, beams, floors, and walls, subjected to transv stress, the steel shall be assumed to take the entire tensile stress without aid from the cone, and shall have an area sufficient to equal the comp strgth of cone composed of 1 part Port cem, 3 parts sand, and 6 parts of broken stone, of the^ age of 6 mos. " "In walls or posts subjected to comp only, no allowance will be made for the strgth of imbedded steel, which will be used only as a precaution against cracks due to shrinkage or changes of temp." "In tanks, the imbedded steel under a stress not exceeding 15,000 Ibs / Q" shall be capable of taking the entire water pres without aid from the cone," Cfli Elongation in service not more than 0.2 %, Ch. 113. Adhesion between steel and concrete. Assumed > al- lowed shear on cone, Mh, Ms : < shear on cone, Un ; in stone or gravel cone, 50 Ibs / Q"; slag, 40; cinder, 15, Ph. 114. In 1 : 2 : 4 cone, max, Ibs / D": on plain round or square bars, structural steel 70 high carbon steel 50 on plain flat bars, ratio of sides > 2 : 1 50 on twisted bars, < 1 twist in 8 diams 80 on specially formed bars, 0.25 X ult adhesion as determined by test; max = 100 Ch. 115. When the allowed adhesion is exceeded, "provision must be made for transmitting the strgth of the steel to the cone," IJn, Mh, 116. Length and lapping. Longitudinal bars not less than 3O ft, if possible, Lv. In beams, rods of single length, if possible, NO, Co, Ci. If lapped Size of rod, ins Y* % Yz Ys % Ys 1 1Y S 1H Lap, ins 6 10 13 18 20 22 26 30 32 NO. 6 9 12 15 18 20 22 24 27 Co. Lap = 25 diams of rod, Bu. Lap < 20 X diam of rod, < 1 foot, Ci. In parallel rods, joints staggered, Bu, Ci. Ends, not less than 2" from any surf, Ly. Rods extend to extreme edges of unfinished surfs. " within L" of finished surfs. Co. Floor rods extend 4" beyond face of wall supporting the floor; Beam " " < 8" beyond face of wall supporting the floor, NO, Ci. See Clearance, below. 117. Protection. If work is interrupted, bars, already placed, must be protected, as with canvas or tarred paper. Ends, projecting for a con- siderable time, to be painted with heavy coat of neat cem grout, F, Lv. Permit. 118. Complete detailed plans and specfns, giving composition of cone, to be filed with the Commissioner of Bldgs, Ch, Un, Mh, Ph. Issue of permit does not involve acceptance of constr, Ch. For tests required, see pp 1194-5. Clearance. See also HU 116, 134, 144, 149. instance, t, between steel and surf of cone. 119. In cols, beams and girders, t < 1 1 / 2 ", Ch, Ms : in slabs, t < H" < diam of bar, Ch ; t < %", Ms; t < 1.5 X diam of bar, JC. Axis of rods dist from outside of cone < diam of rod, CS. For fireproof buildings, see 1J1f 120-128. Clear dist betw bars < 1.5 X max sectional dimension of bar, Ch, JC. Clear dist betw two layers of bars, < %", JC. 120. For fireproof buildings (U1I 120-128), reinfd cone constr not approved "unless satisfactory fire and water tests shall have been made under the supervision of this Bureau," Mh. May be accepted if designed as prescribed in code, provided that : (1) Agg shall be "hard -burned broken bricks, or terra-cotta, clean furnace CONCRETE SPECIFICATIONS. 1197 For abbreviations, symbols and references, see p 947 I. clinkers entirely free of combustible matter, clean broken stone, or furnace slag, or clean gravel, together with clean siliceous sand, if sand is reqd to produce a close and dense mixture ; " Un. (The other codes quoted specify fewer permissible varieties of agg.) Agg to pass % in sq mesh, Ch ; 1" ring, and 25 % of agg > half max size, Ph. (2) Min thickness, t, of cone, surrounding the reinfg members, shall be as follows, where d = diam parallel to t : 121. When d > W , t = 1"; when d > 34", t = 4 d. In any case t > 4"; t < thickness required for structural purposes plus a, a = 1" in cols and girders, a = %" in floor slabs "but this shall not be construed as in- creasing the total thickness of protecting cone as herein specified." Un. 122. In girders and columns, t = 2"; in beams, t= 1 W\ in floor slabs, t = l*i JC. 123. In monolithic cols, the outer 1 Y^' to be considered as protective covering, and not included in effective section, JC. 124. For beams and girders ; on bottom, t = 2"; on sides, t = 1 y/. Under slab rods, t = 1". In cols, t = 2", Ch, Ph. 125. "If a supplementary metal fabric is placed in the cone surrounding the reinfg, simply for holding the cone, the thickness of cone under the re- infg may be reduced by %", such fabric shall not be considered as reinforcg metal," h. 126. On floor and roof beams, t = 1"; on floor and roof girders, and on beams carrying masonry, on top, t = 1"; elsewhere, 2"; on cols, carrying only floors, t = 3"; on cols built into or carrying walls, 4", Ms. 127. Cinder concrete, for fireproof constr, t same as for stone cone; for slow-burning or mill constr, on cols, t = 2"; "on beams, girders and other structural steel or iron members," t = 1 M"- Covering to have "metal binders or wire fabric imbedded in and around" such members; binders, if of wire, not less than No. 8, not less than 16" apart, Ch. 128. Corners of cols, beams and girders, to be beveled or rounded, JC. Columns. 129. Columns must be allowed < 2 hrs for settlement and shrinkage before girders are constructed over them, JC. ISO. " Rules for the computation of reinfd cone cols may be formu- lated from time to time by the bldg commissioner with the approval of the board of appeal, " Ms. 131. Concrete and steel assumed to shorten "in the same proportion", Ms. 132. Cone and steel stressed in ratio, n, of their elastic moduli, JC. 133. Rods tied together at intervals sufficiently short to prevent buckling, Ms. See 1 136. 134. Outer 1 H" to be considered as protective covering and not included in effective section, JC. Reinforced columns. L = length; d = diameter or least side. 135. Reinfd cone may be used for cols when L > 12 d, Ch, Un, Mh ; > 15 d, JC; and where cross section area < 64 Q", Ch. If L > 15 d, allowable stress to be decreased proportionally, Ph. 136. Requirements. Rods to be tied together at intervals not more than d, Un, Mh, Ph ; not more than 12 d, not more than 18", Ch. See H 133. 137. Longitudinal rods not considered as taking direct compres- sion, Ph. 138. Combined cross section area of comp rods > 3 % of cross sec area of col, Ch. 139. When comp rods are not reqd, combined cross sec area of rods to be < 0.5 % of cross sec area of col; not less than 1 D", Ch. 140. Least dimension of smallest rod to be not less than J^", Ch. 1198 CONCRETE. For lists of Specifications for Concrete, see pp 1184, 1185. 141. Rods to extend into the col above or below, lapping the rods there sufficiently to develop the stress in the rod by the allowed unit for adhesion, Ch. 143. Eccentric or transverse loading. Max fiber stress, in- cluding (1) direct comp, (2) bending due to direct comp, (3) eccentricity and (4) transverse load, not more than allowable comp stress. Eccentric load "shall be considered to affect eccentrically only the length of col ex- tending to the next point below at which the col is held securely in the direction of the eccentricity," Ms. 143. A column, monolithic with or rigidly attached to a beam or girder, must resist, in addition to direct loads, a moment = max unbalanced moment in the beam or girder at the col, Ch. 144. Hooped columns. Cone may be stressed to 25 % of ult itrgth, provided (1) Cross sec area of vert reinfmt < area of spiral reinfmt, > 5 % of area within hooping ; (2) Percentage of spiral hooping < 0.5, > 1.5; (3) Pitch of spiral hooping uniform and > 0.1 X diam of col, > 3"; (4) Spirals so secured to verticals, at every intersection, as to main- tain form and position; (5) Spacing of verticals > 9", > H circumference of col within hooping. Hooping "may be assumed to increase the resistance of the cone equiv- alent to 2.5 X the amount of the spiral hooping figured as vert reinfmt." \Conc, outside of hooping, not considered as part of effective col sec, Ch. 145. "The working stresses will be a subject for special consideration by the Commissioner of Bldgs," Un. 146. Allowed unit compression = 1000 Ibs/D* of area within hooping, Ph. 147. Percentage of long'l rods and spacing of hoops to be such that the cone may develop this stress with a safety factor of 4, Ph. 148. "Hoops or bands not to be counted upon directly as adding to the strgth of the col," JC. 149. Clear spacing of bands and hoops > 0.25 X diam of enclosed col, JC. 150. Structural steel reinforced columns. Cone may be subjected to, M ult stress, provided (1) cross sec area of steel is not less than 1 D"; (2) spacing of lacing or battens not more than least width of col, Ch. Beams and floors. 151. The common theory of beams is applicable. In, Ch, 152. The steel is assumed to take all the direct tensile stresses, X<, I'll. Ch, Ms, Mh, Ph. Tensile stress in cone to be considered in calculating deflections, JC. 153. The stress-stretch curve of cone in comp is assumed to be a straight line, Ch, Ph. n, = E a /E c , = 15; for deflections, n = 8 to 12, JC. 154. At 2000 lbs/D" extreme fiber stress, this curve may be taken as (a) a straight line; (b) a parabola, with axis vert, and vertex on neutral axis of beam; or (c) an empirical curve, enclosing an area % greater than if curve were a straight line, and with cen of grav at same height as that of area in (b), Uu. 155. Stresses. A load, = 4 X the total working load, stresses the steel to its elas lim, and the cone to '2000 lbs/D", Un. Design "based on the assumption of a load 4 times as great as the total load, Ph. (Total load = ordinary dead load plus ordinary live load, Un, Ph.) 156. The adhesion, betw cone and steel, is assumed to be sufficient to make them act unitedly, Un, Ch, Mh, Ph. 157. Exposed metal not considered in figuring strgth, Un, Ch, Ph. 158. Span = dist c to c of bed plates or other bearings, Ms, JC. If beam is fastened to side of a col, span is measured to cen of col, Ms. Span > (clear span + depth of beam or slab), JC. CONCRETE SPECIFICATIONS. 1199 For abbreviations, symbols and re ferences, see p 947 I. 159. Shrinkage and thermal stresses to be provided for by introduction of steel, Ch, Ph. "Initial stress in the reinfmt, due to con- traction or expansion in the cone, may be neglected," JC. 160. When the shear developed exceeds the allowed limit for cone, steel must be introduced to take the excess, Un, Mh, Ph, JC. 161. Allowable values for shearing stresses: Ibs/D" (a) With horizontal bars only 40; (b) With part of the hor reinfmt in the form of bent-up bars, "arranged with due respect to the shearing stresses" >60; (c) With thoro reinfmt for shear >120, Under (c), cone may be taken as carrying % of the shear; the remaining % being carried by bent rods or stirrups (preferably both) carrying their share within a hor dist = depth of beam, JC. 162. Longitudinal spacing of stirrups or bent rods > 0.75 X depth of beam, JC. 163. Cement finish, added to the tops of slabs, beams and girders, not to be included in figuring strgth "unless laid integrally with the rough cone, " and to be allowed no greater unit stress than that on the rough cone, Ch. 161. Web reinforcement. "Where the vertical shear, measured on the sec of a beam or girder, betw the centers of action of the hor stresses, > 0.02 X the ult direct comp stress /Q", web reinfmt shall be supplied, sufficient to carry the excess. The web reinfmt shall extend from top to bottom of beam and loop or connect to the hor reinfmt. The hor reinfmt, carrying the direct stresses, shall not be considered as web reinfmt," Ch. 165. Steel in the compression sides of beams and girders. "When steel is used in the comp side of beams and girders, the rods shall be tied in accordance with requirements of vert reinfd cols with stirrups connecting with the tension rods of the beams or girders," Ch. 166. "When steel or iron is in the comp sides of beams the proportion of stress taken by the steel or iron shall be in the ratio of the mod of elas of the steel or iron to the mod of elas of the cone; provided, that the rods are well tied with stirrups connecting with the lower rods of the beams;" Ph. 167. Where slabs are used with girders and beams, the girders and beams are treated as T'-beams, a portion of the slab acting as flange; O. 168. Portion, F, of width of slab, acting- as flange. t = thickness of slab ; L = span of beam or girder ; 6 = breadth of beam or girder ; S = dist c to c betw beams or girders. F to be "determined by assuming that, in any hor-plane sec of the flange, the stresses are distributed as the ordinates of a parabola, with its vertex in the stress-stretch curve and with its axis in a longitudinal vert plane thru the cen of the rib of the T." Said portion to be reinforced with bars near the top, at right angles to the girder. Un. 169. F dependent upon hor shearing stress; F > 20 1, Ph ; F > 10 b, Mil. 170. F governed by shearing resistce betw slab and rib; F > S ( 1 j- 2 \ > L/3, > % S. To be assumed as thus acting, slab must be cast at same time with rib, Ch. F > L/3, > -S, Ms ; > L/4, > 8 t + b, JC. 171. T -beams to be reinfd against shear along plane of junction between rib and flange, Un, Ph ; using stirrups thruout length of beam, Ph. 172. Ribs of girders and beams to be monolithic with floor slabs. Un, Ph. 173. "Where reinfd cone girders carry reinfd cone beams, the portion of the floor slab acting as flange to the girder must be reinfd with bars near 1200 CONCRETE. For lists of Specifications for Concrete, see pp 1184, 1185. the top, at right angles to the girder, to enable it to transmit local loads directly to the girder and not thru the beams, thus avoiding an integration of comp stresses due to simultaneous action as floor slab and girder flange." Un, Ph. Moment, M. See also Iffl 178, 179. 174. W = load per sq ft; L = span, in ft. In freely supported slabs, L = free opening + depth; in continuous slabs, L = distance betw centers of supports. 175. With concentrated or special loadings, calculate and provide for moments and shears for critical condition of loading, Ch. For dead load; M obtained from the actual dead load") covering all ' live load, over supports; M obtained from the >- spans at actual live load j same time. between supports; M = max obtained from live load covering 2 consecutive or 2 alternate spans at same time. When all spans are equal, let M c = min live-load moment at middle of span. Then, W L 2 for intermediate spans, M = 12 W L* for end spans M C W L 2 Sum of live load moments over one support and at cen of span, < - , Ch. Continuity. See also 175. 176. Beams and girders considered as simply supported at ends ; no allowance made for continuity, Un, 51 h. 177. Beams, etc, calculated as simply supported, or as continuous, according to the facts, Ch, Ms. 178. Continuous floor plates, reinfd at top over supports, may be treated as oontinuous beams. Under uniformly distributed loads, mom, M, taken at not less than 0.1 W L; 0.05 W L with square floor plates, reinfd in both directions and supported on all sides, Un, Mh, Ph. 179. In floor slabs adjoining: walls; if slab is reinfd in one direction, M = ; if square and reinfd in both directions, M = .--; O ID Ph. 180. Floor slabs designed and reinfd as continuous over the supports. If length of slab > 1.5 X its width, the entire load should be carried by transverse reinfmt. "Square slabs may well be reinfd in both directions," JC. 181. For beams and slabs continuous for > 2 spans, bending moms at cen and at support, for both live and dead loads, as follows: In floor slabs and in interior spans of continuous beams, M = w L-/\2; in end spans of continuous beams M = w L 2 /10, w = load per unit of span; L = span, JC. 183. In continuous spans, provide, at supports, for negative mom = 0.8 positive mom at cen of a simply supported span. Pos mom, at cen of continuous span, may be taken = neg mom at support, Ms. Tests. 183. Bldg Commissioner may require tests of materials before or after incorporated into bldg, Ms. Contractor must be prepared to make load tests in any portion of bldg within a reasonable time after erection, and as often as may be reqd by engineer, Ch, Ph, Mh, Un. Tests must show that the constr will sustain loads as follows: SPECIFICATIONS FOR SIDEWALKS. 1201 For abbreviations, symbols and references, see p 947 1. load = 2 X sum of proposed dead and live loads, Ch ; = 2 X proposed live load, Ph ; = 3 X proposed load, Mb. 184. Construction may be considered as part of the test load, Ch. 185. Each test load shall cover 2 or more panels, and remain in place not less than 24 hrs, Ch. 186. Deflection of slabs not more than . oUU Deflection of girders > -~ '= X ratio of slab depth to girder depth, CJi. oUU 187. Test, 45 days after completion. Load = 1.5 X live load + 1.5 X dead load of finished area. Deflection > 0.001 X length of member, Ci,b. CONCRETE SIDEWALKS. Abstract of Specification Adopted by National Association of Cement Users Philadelphia, January, 1908. 1. Cement, Portland, to meet specification of A S T M, adopted Jan, 1906. See p 940. 2. Sand. To pass No. 4 screen. May contain > 5 % loam and clay, if these do not coat the sand grains. < 60 % of the sand to pass No 10 sieve, or 35 % to pass No 10 20 30 40 sieve, and remain on No 20 30 40 50 " , respectively. > 20 % of the sand to pass No 50 sieve, or 70 % to pass No 10 20 sieve, and remain on No 40 50 " .respectively. 3. Screenings, from crushed stone as below, and meeting sand require- ments, may be substituted for sand. 4. Aggregate. Stone, crushed from clean, sound, hard, durable rock, screened dry thru %" mesh, retained on W mesh. 5. Ciravel, clean, hard, ranging from that retained on W mesh, to that passing %" mesh. 6. Unscreened gravel, clean, hard. No particles larger than %". Proportion of fine and coarse particles to conform to requirements below for cone. 7. "Water, "reasonably clean, free from oil, sulfuric acid and strong alkalies." Sub-base. 8. Sub-base to be thoroly rammed. Soft spots removed and replaced by hard material. 9. Fills > 1 ft thick, to be thoroly compacted by flooding and tamping in layers > 6" thick, "and shall have a slope of < 1 : 1.5." "The top of all fills shall extend < 12" beyond the sidewalk." 10. "While compacting, the sub -base shall be thoroly wetted and shall be maintained in that condition until the cone is deposited." Base. 11. Voids. Cem must overfill voids in sand by < 5 %. 12. Mortar must overfill voids in agg by < 10 %. Proportions 1 : > 8 sand and agg. 13. When the voids are not determined, 1 : 3 sand or screenings : 5 stone or gravel. "A sack of cem, 94 Ibs, shall be considered to have a vol of 1 cu ft." C12 1 202 CONCRETE. Mixing. 14. Hand. Sand evenly spread on a level water-tight platform, cem spread on sand. Mix dry to uniform color. Water sprayed and mass turned until homogeneous and of uniform consistency. Drenched agg added and all mixed until agg is thoroly coated with mortar. 15. Hand. With unscreened gravel. Cem and gravel "mixed dry until no streaks of cem are visible." Water sprayed and mixed. Mortar must be equivalent to that specified above. 16. Water may be added while mixing, but cone must be turned < once immediately afterward. 17. " Machine mixing: will be acceptable when a cone equivalent in quality to that specified above is obtained. " 18. Retempering prohibited. Grade. 19. Grade of sidewalk < sufficient for drainage, > W/ft, "except where such rise shall parallel the length of the walk." Forms. 20. Lumber, clean, free from warp, < 1 %" thick. 21. Upper edges to conform with finished grade of sidewalk. 22. Cross forms. "At each block division, cross forms shall be put in the full width of the walk and at right angles to the side forms, " except as in U 23. 23. Expansion joint. A metal parting strip y? thick to replace a cross form < once in 50 ft. "When the sidewalk has become sufficiently hard, this parting strip shall be removed and the joint filled with suitable taaterial prior to opening the walk to traffic. Similar joints shall be pro- vided where new sidewalks abut curbing or other artificial stone sidewalk." 24. "All forms shall be thoroly wetted before any material is deposited against them." 25. dimensions of blocks. Size, feet 6X6 5X5 4.5X4.5 4X4 3X3 Thickness, ins : In business districts, 6 5.5 5 4 ... In residence districts, 6 5 ... 4 3 In residence sidewalks, edges may be 25 % thinner than center; min = 3". 26. Separating tool > 6" wide, W thick. Groove cut thru into sub-base; groove filled with dry sand before the top coat is spread; top coat cut thru to the sand after floating and troweling, "and a jointer run in the groove"; trowel then drawn thru groove again "so as to insure a complete separation of the block." Depositing. 27. Cone carried to forms in watertight wheelbarrows. Cone must not slop over. Barrows must not be run over freshly laid cone. 28. Cone must be deposited within 1 hour after mixing, spread evenly, and tamped until water flushes to the top. Protection. 29. Workmen must not walk on freshly laid cone. 30. Sand or dust, collecting on the base, to be "carefully removed before the wearing surface is applied." Wearing surface. 31. Minimum thickness, %". 32. Mortar, 1 : 2 sand or screenings, mixed as for base, but wet enough not to require tamping, and so as to be readily floated with a straight-edge. "A thin coat of mortar shall be floated on to the base before spreading the wearing surf." Mortar spread on base within 30 mins after mixing, and floated within 50 mins after base cone is mixed. CONCRETE BLOCKS. 1203 33. Marking. "After being worked to an approximately true surf, the block markings shall be made directly over the joints in the base with a tool which shall cut clear through to the base and completely separate the wearing courses of adjacent blocks." 34. Surface edges rounded to a radius < W. 35. "When partially set, the surf shall be troweled smooth." 36. On grades > 5 %, surf to be roughened by a suitable tool "or by working coarse sand or screenings into the surf." 37. Only mineral colors shall be used, and these shall be incor- porated with the entire wearing surf. Single coat work. 38. Proportions, 1 : 2 sand : 4 gravel or crushed stone. Blocks separated as in two-coat work. Cone to be firmly compacted by tamp- ing, and evenly struck off and smoothed to the top of the mold. "Then, with a suitably grooved tool, the coarser particles of the cone tamped to the necessary depth so as to finish the same as two-coat work." Protection. 39. "When completed, the sidewalk shall be kept moist and pro- tected from traffic and the elements for at least 3 days. The forms shall be removed with great care, and upon their removal earth shall be banked against the edges of the walk." Grading adjacent to sidewalk. 40. On curb side, 1 %" below sidewalk, slope < W/ft. On property side, "the ground should be graded back < 2 ft and not lower than the walk. " CONCRETE BLOCKS. 1. Buffalo harbor. Blocks 6 ft long, abt 4 ft sq, 88.75 cu ft = 3.3 CVL yds, made in wooden molds. Yi bbl Port, 2.5 cu ft sand, 7.5 cu ft pebbles, 7.5 cu ft broken stone, made a layer of cone, in mold, about 6" thick. Faces, 6" thick, of blocks on lake-face of breakwater, of finer material. Face placed first; backing placed before face had set. (Emile Low, A S C E, Trans, June '04, Vol LII, p 96.) 2. Zeebrugge breakwater, Belgium. Blocks 25 m (82 ft) long, 9 m (29.5 ft) wide, 8.75 m (28.7 ft) high, 2000 cu m (2616 cu yds), 4500 tons each. Outer cone shell, with cutting lower edge, three compartments, formed in iron framework and floated to place; placed between guides and block last sunk; sunk by admission of water, and filled up with cone, 1 cem: 2.5 sand : 6.1 broken porphyry, by means of skips of 10 cu m (13 cu yds). Top meter, rich in cem, placed above water at low tide. Seaward toe immediately protected by rubble rip-rap. Superstructure of 55-ton blocks, laid above water; these surmounted by cone blocks, formed in place. 3. Molds for isolated monolithic sub-aqueous concrete blocks, from 150 to 222 cu yds, forming pier of trapezoidal cross- sec. The molds are bottomless boxes of trapezoidal cross-sec, composed of two sides and two end pieces, held together by 1 W' turnbuckle tie-rods acting on beams placed outside of the mold. The tie rods have, at each end, eyes in which wedge-bolts are inserted at time of erection. To remove the molds, the wedge-bolts are removed by turning up a nut on the rods which form an integral part of the wedge-bolts. This pulls the wedge-bolt from the eyes of the tie-rods and releases the walls of the molds, which are then picked up by the mold traveller, and re-assembled on the traveller ready for re-setting. Weight of mold, 40 tons. Time reqd for removing mold from a block and re- assembling for re-setting, from 45 to 60 mins. Buoyancy of timber overcome by cast iron ballast wts. Alternate blocks placed first. For intermediate blocks only the two side pieces of a mold are used. These are held in place and at their proper batter by six turnbuckle tie-rods, each passing thru a hollow square box of one-inch plank, acting as a strut. (South Pier at Superior Entry, Wisconsin. Report of Clarence Coleman, Asst. Engr Report Chf Engr, USA, 1904, Part IV, page 3781.) 1204 CONCRETE. 4. " Lewis holes should be cast in the blocks where practicable" and so "as not to bring excessive pres on the cone, particularly near the mortar facing or near the arrises of the block." Lewises and dogs may pull out of green blocks. Provide wooden blocks and rag cushions for use in turning over the blocks, otherwise the corners may be damaged. 5. Casting: position. Blocks should be cast with the most important face down, their showing faces as nearly vert as practicable, and the back of the block on top, so that laitance, etc, rising to the surf, may appear there. HOLLOW CONCRETE III 1 1 I>l \ . BLOCKS. Abstract of Specification Adopted by National Association of Cement Users, Philadelphia, January, 1908. 1. Cement, Portland, to meet specification of A S T M, adopted Jan, 1906. See p 940. 2. Sand, silicious, clean, gritty, to pass W mesh sieve. 3. Aggregate, clean broken stone, free from dust, or clean screened gravel, passing %" mesh sieve, refused by %" . 4. Unit of measurement for cem. Bbl = 380 Ibs net; cu ft > 100 Ibs. Cem either measd in original package, or weighed; not measd loose in bulk. 5. Proportions. For exposed exterior or bearing walls. (a) Machine-made. Semi-wet, 1 : > 3 sand : > 4 agg. (b) Slush (or wet) cone (quaking or flowing), made in individual molds and allowed to harden in them, 1 : > 3 sand : > 5 agg. If stone is omitted, proportion of sand may be increased if tests show no increase in voids or in absorption, and no loss of strength. 6. Water enough to perfect the crystallization of the cem. 7. Mixing:. "Thoro and vigorous mixing is of the utmost importance. " (a) Hand. Cem and sand mixt dry. Water added slowly and workt in. Moistened agg spread upon mortar, or mortar upon agg. Mix. (b) Machine preferred. Cem and sand, or cem, sand and agg, mixt dry. Water added and workt in. With wet cone, "this procedure may be varied with the consent of the bureau, etc." 8. Molding*. Top surf of tampt blocks, after striking off, to be "trow- eled or otherwise finisht to secure density and a sharp and true arris." 9. Curing-. After molding, blocks to be "carefully protected from wind currents, sunlight, dry heat or freezing for at least 5 days," and sup- plied with additional moisture during that time "and occasionally thereafter until ready for use." 10. Minimum ag-e before using. 1 : 3 sand, 3 weeks; 1 : 2 sand, 2 weeks "with the special consent of the bureau, etc"; special blocks, for closures, 7 days "with the special consent of the bureau, etc." 11. Marking 1 . All blocks to be markt with maker's name or brand, day, month and year of mfr, and proportions, as "1 : 2 : 3," etc. 12. Mortar. "All walls, where blocks are used, shall be laid up with Portland cem mortar." 13. Maximum load, including wt of wall, 8 tons per sq ft of area of blocks. 14. Thicknesses of walls. Bearing walls "may be 10% less than is reqd by law for brick walls." In curtain or partition walls same as for hollow tile, terra cotta or plaster blocks. 15. Offsets. "Wherever walls are decreased in thickness, the top course of the thicker wall shall afford a full solid bearing for the webs or walls of the course of blocks above." 16. Under girders or Joists, blocks to be made solid for < 8" from inside face. If concentrated load, W, on block, > 2 tons, this applies to the blocks supporting the girder, etc; if W > 5 tons, it applies to blocks for < 3 courses below, and to a dist of < 18" each side of girder, etc. SPECIFICATIONS FOR BLOCKS. 1205 17. In party walls, blocks must be filled solid. 18. Bond. "Where the walls are made entirely of cone blocks, but where said blocks have not the same width as the wall, every 5th course shall extend thru the wall, forming a secure bond, when not otherwise sufficiently bonded." 19. Block facing-, on brick backing, "must be strongly bonded to the brick, either with headers projecting 4" into the brick work, every 4th course being a header course, or with approved ties, no brick backing to be less than 8"." 20. Thickness of web of block (in bearing walls) < 0.25 X ht of block. 21. Hollow space. In bearing walls, min percentage of hollow space: Buildings of 1st 2d 3d 4th 5th 6th story 1 & 2 stories 33 33 3 & 4 " 25 33 33 33 5 & 6 " 20 25 25 33 33 33 22. Sills and lintels to be "reinforced by iron or steel rods in a manner satisfactory to the bureau, etc." When span > 54", lintel "shall rest on block solid for < 8" from face next the opening and for < 3 courses below bottom of lintel." 23. Prior to use, application must be filed with bureau or with chief of proper department, giving "a description of the material and a brief outline of its manufacture and proportions used," with "name of the firm or corporation, and the responsible officers thereof," "and changes in same thereafter promptly reported." 24. Certificate of approval to remain in force > 4 mos, "unless there be filed with the bureau of building inspection, at least once every 4 mos following, a certificate from some reliable physical testing laboratory showing that the av " of < 3 comp tests and < 3 transverse tests comply with requirements; "the said samples to be selected by a building inspector or by the laboratory from blocks actually going into construction work." 25. Preliminary test. Maker to submit product to tests required, and file certificate, from a reliable testing laboratory, giving in detail the results of the tests made. Results of all tests, satisfactory or otherwise, t9 be filed in the bureau, open to inspection, but not necessarily for publication. 26. Additional tests. Maker or user or both "shall, at any and all times, have made such tests of the cems used in making such blocks, or such further tests of the completed blocks, or of each of these, at their own expense and under the supervision of the bureau of building inspection, as the chief of said bureau may require." Failure to stand these tests involves immediate revocation of the certifi- cate issued to maker. 27. Test requirements. Blocks must be subjected to transverse, compression and absorption tests, "and may be subjected to the freezing and fire tests." Freezing and fire tests not at cost of mfr. 28. Approval tests made at expense of applicant. 29. .\ot less than 12 samples to be selected by bureau, etc. 30. "Samples must represent the ordinary commercial product, of the regular size and shape used in construction. The samples may be tested as soon as desired by applicant " but > 60 days after mfr. 31. Blocks, failing; to stand tests, to be marked "condemned" by mfr or user, and destroyed. 32. "Tests shall be made in series of at least 3, except that in the fire tests a series of 2 (4 samples) are sufficient." 33. " Half samples may be used for the crushing, freezing and fire tests. The remaining samples are kept in reserve, in case duplicate or con- firmatory tests be reqd." 1206 CONCRETE. 34. "All samples must be marked for identification and com- parison." 35. Transverse test. Sample (full size) placed flatwise on parallel rounded knife-edge bearings, 7" apart. Load applied, midway between supports, thru rounded knife-edge. 3 W L Modulus of rupture = 2 ; where W = load, in Ibs; L = span = 7"; 6 = breadth of block, ins; d = depth of block, ins. "No allowance should be made. . . for the hollow spaces." At 28 days, modulus of rupture, av 150 lbs/D", min 100. 36. Compression test. "Samples must be cut from blocks, so as to contain a full web section. The sample must be carefully measd, then bedded flatwise in plaster of paris, to secure a uniform bearing in the test- ing machine, and crushed. The total breaking load is then divided by the area in compression in sq ins, no deduction to be made for hollow spaces; the area will be considered as the product of the width by the length." 37. Ultimate comp strength at 28 days, av 1000 Ibs/ D", min 700. 38. For bearing walls, min 1000 Ibs / Q". No deduction to be made for hollow spaces. 39. Absorption. Sample dried to cpnstant wt, at > 212 F. Weighed; placed in water, face downward, immersed < 2". Weighed at 30 mins, 4 hours, 48 h, and replaced in water immediately after each weigh- ing. At end of 48 h, comp strength of wet specimen to be determined as in U 36. wt of water absorbed Absorption = . Av > 0.15; max, 0.22. wt of dry block 40. Reduction of comp strength, by absorption, > %.* 41. Freezing test. Sample immersed, as in H 39, for < 4 h, and weighed. Subjected to < 15 F for < 12 h. 1 h in water of < 150 F. Operation repeated 10 times. Weigh while still wet from lasf thawing. "Its crushing strength should then be determined" as in ^] 36. 42. Loss of weight, max 10 %; loss of strength, max %.* 43. Fire test. Two samples placed in cold furnace. Temp gradually raised to 1700 F. Maintained for < 30 mins. One sample plunged in water of about 50 to 60 F. The other sample cooled gradually in air. "The material must not disintegrate." 44. Cement brick, as substitute for clay brick. 1 : > 4 clean sharp sand; or 1 : > 3 clean sharp sand : 3 broken stone or gravel passing Yi sieve and refused by W. In other respects, cem bricks to conform to specfns for hollow cone blocks. * "Except that, when the lower figure is still above 1000 Ibs / D", the loss in strength may be neglected." COST. 1207 COST. 1. The following data respecting prices and costs are compiled from rec- ords of actual cpnstruction as carried out by men presumably skilled in the art, and employing labor at ab9ut the usual rates. They afford only approx estimates of what may ordinarily be expected. The cost of materials, trans- portation, and especially of labor, varies from time to time and from place to place. 2. Not only does the rate per hour for labor vary; but the amt of work turned out in a given time varies much more widely. A well matcht gang, presided over by an efficient foreman, will produce usually from two to four times the output of an indifferent gang. Even a well-meaning worker will frequently let his efficiency drop to 75 % of what may reasonably be expected; indifferent workers will produce only 30 or 20 %. The methods of payment, the character of superintendence, and the way in which the work is arranged and handled, are all very important; and a bungler, or one unfamiliar with cone operations, would probably find difficulty in keep- ing the total costs within double those given. 3. The principal items, making up the cost of cone (plain and reinfd) may be classified as follows: Materials; Cem, sand, gravel, stone, reinfmt. Transportation to storage; Hauling, freight Storage. Screening, washing. Mixing ; Loading and transporting to mixer, mixing machine and power, labor and depreciation connected with it, auxiliary apparatus as mixing board, barrows,, shovels, etc., and transporting cone to forms. Forms; Erection, shifting, depreciation, material, labor. Depositing; Dumping, spreading and ramming. Finishing; plastering, brushing, etc. Inspection and superintendence. Plant (besides mixer and forms); Interest, depreciation, repairs, insurance. Cost of Materials. 4. For prices of cem, sand, etc, see " Price List," p 1211. 5. The cost of any one material, per cu yd of cone, varies greatly in diff cases, due to wide variations in the percentages employed for diff grades of cone, and can therefore be approximated only betw wide limits. 6. Roughly stated, the total cost, for materials alone, may be ex- pected to fall somewhere between $2.50 and $7.50/cu yd of cone. The av would probably be $4 or a little more, exclusive of reinfmt. 7. Cement. For prices, see "Price List." Per cu yd of cone, betw $1.50 and $4, $2 and $3 being the more usual limits; affected chiefly by grade of cem and richness of mixture. 8. Sand. For prices, see "Price List." Per cu yd of cone, betw 15 cts and $1, usually below 25; affected chiefly by grade, dist from bank, natural monopoly, and proportion used in mixture. 9. Oravel. In the pit, exclusive of screening, loading and hauling, from 20 cts to 75 cts per team load; affected chiefly by quality, and natural monopoly. 10. Stone. For prices, see ' ' Price List." Av price for stone, broken to reqd size, at quarry, exclusive bf cartage, about $1 or $1.50 / cu yd stone. Per cu yd cone, betw 50 cts and $1. Affected chiefly by quality, dist from quarry, natural monopoly, and proportion of mixture. 11. Reinforcement. Cost will vary with the design and type em- ployed. For iron and steel bars, see "Price List." Plain rods, 50 ton lots, at mill, cts per Ib, approx: < H", i l A; V \lsTested By Chemists Send for a free copy of 8o-page illustrated handbook "ALPHA CEMENT; HOW TO USE IT" Also Art Envelope T containing views of distinctive concrete construction ALPHA PORTLAND CEMENT CO. GENERAL OFFICES: EASTON, PA. SALES OFFICES: New York, Hudson Terminal Chicago, Marquette Building Boston, Board of Trade Buffalo, Builders' Exchange Philadelphia, Harrison Building Baltimore, Builders' Exchange Pittsburgh, Oliver Building Savannah, National Bank Building 1304 PRICE LIST. Reinforcement. 10, 11, 16, 19, 29, 40, 49, 57, 62, 68, 89. Reinforcing bars, f.o.b. warehouse, %" 2% jets per lb., to Fire-Proofing. 8, 16, 29. Mixers, Concrete . 16, 21, 28, 51, 53, 54, 56, 66, 81, 83, 98. ", 2% cte per Ib. 29. 4, 53. Water-Proofing-. Concrete Block Machines. Special Constructions. 10, 11, 27, 60, 80. Composition Floor ("Sanitary"), 12 cts per sq ft., %" thick, f.o.b. Syracuse, N. Y. 95. REC'V'G CAP., INCHES 8X14 9X16 10X18 12X24 14X36 Crushers. CAPACITY, TONS PER HOUK 10 to 15 12 to 18 16 to 24 24 to 40 45 to 60 H. P. REQUIRED. 10 to 12 12 to 15 15 to 20 30 to 35 60 to 75 PRICE. $600 800 1000 1600 4000 47, 85. Testing Laboratories. makes the Lightest Roof s and Floors It is a solid steel sheet with dovetail corrugations which are in- versely tapered, which allows the ends to dovetail with adjoining sheets. Is used for concrete roofs, floors, stairs, partitions, etc. Easily handled, quickly erected, and makes a weatherproof roof even before the concrete is applied. Ask for catalog H. THE BROWN HOISTING MACHINERY CO., Cleveland, O. ADVERTISEMENTS. 1305 Marion Bar Splicers Reinforcing Couplings as Strong as the Continuous Bar Save Steel. Give Continuous Reinforcement SURE GRIP CLIPS for square or twisted bars are unequaled for strength or holding power. Malleable base steel U Bolts cold rolled threads. Sizes: % fl ; %; %; %; %; %; %; 1"; iVs; l 1 ^. HEXAGON COUPLINGS for round bars save time; save steel; unequaled for strength and rigidity. Sizes: 1/2; %; %; 7s ; 1"; 1%; 1%. For Form Work by using Hexagon Couplings, Stud Bolts may be removed leaving no steel or wires pro- truding. Give unequaled finish. Insure strength and alignment of form at low cost. Write for prices and data. All shipments from stock. Large quantities kept on hand of all sizes ready for shipment immediately. Malleable castings of all kinds. The Marion Malleable Iron Works Marion, Indiana 1306 ADVERTISEMENTS. Up-to-the-minute in- formation on mining and metallurgy Gathered by a staff of contributors from the four corners of the earth, written in an interesting and readable style, and published weekly in MINING S L PRESS EDITED BY T. A. RICKARD In his years of experience as a practical man and as a writer, Mr. Rickard has made for himself an international name as a logical and thorough authority on mining and metallurgical practice. Since 1860 MINING AND SCIENTIFIC PRESS has been the leading paper in this field. More than two thousand pages of live reading matter are published yearly. The subscription price is but 3. Send us your order. and MINING and Scientific PRESS Service A department that keeps in close touch with new business and with changing conditions, as well as secures informa- tion for its subscribers from any part. This service goes to all subscribers. Write for more information today. MINING and Scientific PRESS 420 Market Street, San Francisco CHICAGO LONDON NEW YORK BUSINESS DIRECTORY. 1307 BUSINESS DIRECTORY. (Referd to, from Price-List, pp 1301, 1302 & 1304.) *1. JLtria Portland Cement Co.; Detroit, Mich. 2. Allentown Portland Cement Co.; Allentown, Pa. 3. Alpha Portland Cement Co.; Easton, Pa. *4. American Hydraulic Stone Co.; Concrete Block Machines; Century Bldg., Denver, Colo. 5. Ash Grove Lime and Portland Cement Co. ; Grand Ave. Temple, Kansas City, Mo. *6. Atlas Portland Cement Co. ; 30 Broad St., New York, N.Y. Also Boston; Philadelphia; Des Moines, la.; Chicago; Minneapolis and St. Louis. 7. Bath Portland Cement Co.; Newark, N. J. *8. Berger Mfg. Co.; Sheet Metal Products; Canton, O. Also New York, Boston, Philadelphia, Minneapolis, St. Louis, San Francisco and Chicago. 9. Best Bros. Keene's Cement Co., The ; Plaster for Concrete Surfaces; Medicine Lodge, Kan. *10. Blaw Steel Construction Co.; Steel Forms for Concrete Construction; Pittsburg, Pa. Also New York and Chicago. *11. Brown Hoisting Machinery Co. ; Ferro-inclave Construction ; Cleveland, O. Also New York, Chicago, Pittsburg, San Francisco and Montreal. *12. Canada Cement Co., Ltd.; Portland Cement; 273 Craig St., West, Montreal, P. Q., Canada. 13. Cape Girardeau Portland Cement Co.; Cape Girardeau, Mo. 14. Castalia Portland Cement Co.; Publication Bldg., Pittsburg, Pa. 15. Cayuga Cement Corporation; Portland Point, N. Y. *16. Chicago Builders' Specialties Co.; Concrete Mixers and Contractors' Supplies; 450-470 Old Colony Bldg., Chicago, III. Also New York. 17. Clinchneld Portland Cement Corporation; Kingsport, Tenn. 18. Colorado Portland Cement Co.; Denver, Colo. 19. Concrete Steel Co.; Reinforcing Bars; 42 Broadway, New York, N. Y. 20. Continental Portland Cement Co.; St. Louis, Mo. 21. Contractor's Machinery Co.; Concrete Mixers; 125 llth St., Keokuk, Iowa. 22. Coosa Portland Cement Co.; Ragland, Ala. 23. Crescent Portland Cement Co.; Wampum, Pa. 24. Dexter Portland Cement Co.; Nazareth, Pa. *25. Diamond Portland Cement Co.; Williamson Bldg., Cleveland, O. 26. Dixie Portland Cement Co.; Chattanooga, Tenn. *27. European Asphalts Corp.; Val de Travers naturally impregnated bitu- minous limestone Mastic Blocks, etc.; 79 Tompkins St., New York. 28. Excelsior Mixer & Machinery Co. ; Milwaukee, Wis. *29. General Fireproofing Co.; Reinforcing specialties; Youngstown, O. Also New York, Boston, Philadelphia, Washington, Chicago and London. 30. German-American Portland Cement Works; La Salle, 111. 31. Giant Portland Cement Co.; 603-610 Pennsylvania Bldg., Philadelphia, Pa. Also New York and Boston. *32. Globe Steel Co.; Concrete Hardener; Mansfield, O. *33. Goodyear Tire & Rubber Co. ; Akron, O. 34. Helderberg Cement Co.; Albany, N. Y. 35. Hercules Waterproof Cement Co.; 705 Mutual Life Bldg., Buffalo, N. Y. -*36. Hotchkiss Lock Metal Form Co.; Steel Forms for Concrete Construc- tions; Binghamton, N. Y. 37. Huron Portland Cement Co.; 1575 Ford Bldg., Detroit, Mich. 38. Hydraulic Pressed Steel Co., The; 3160 East 61st St., Cleveland, O. 39. Indiana Concrete Mold Co.; Steel Forms for Sidewalks; 266 E. River St., Peru, Ind. *40. Inland Steel Co.; Reinforcing Bars; Chicago, 111. 41. International Portland Cement Co.; Spokane, Wash. 42. lola Portland Cement Co.; lola, Kan. 43. Iowa Portland Cement Co.; Des Moines, la. *44. Ironton Portland Cement Co.; Ironton, O. 45. Knickerbocker Portland Cement Co.; 30 E. 42nd St., New York, N. Y. 46. Lawrence Cement Co. ; Philadelphia and New York. 47. Lehigh Valley Testing Laboratory; Allentown, Pa. * Names indicated by asterisks are those of firms which have favored us with verification or correction of their listings. C13 1308 ADVERTISEMENTS. BOOKS FOR THE ENGINEER, ARCHITECT AND CONTRACTOR ELEVATOR SHAFT CONSTRUCTION By H. ROBERT CULLMER Assisted by ALBERT BAUER Practical suggestions for the installation of elevators in -buildings. Elevator shaft construction in buildings has never before been technically treated. 170 Pages. Frontispiece. 47 Diagrammatic Plates. 15 Illustrative Plates. CLOTH, $3.00 BUILDING CONSTRUCTION AND SUPERINTENDENCE By F. E. KIDDER Part I Masons' Work. Ninth Edition Revised and Rewritten by THOMAS NOLAN, University of Pennsylvania. Presents the latest and best modern practice in masonry construction. 966 Pages. 7x9 Inches. 628 Figs. CLOTH, $6.00 THE HOLLOW TILE HOUSE By FREDERICK SQUIRES The book treats on the construction of the fireproof home, the most modern development of wall construction in " Texture-Tile," and the most recently devised systems of fireproof floor construction and architectural concrete work. 7^ x 10 Inches. CLOTH, $2.50 ARCHITECTURE AND BUILDING Technical articles on construction ; fireproofing, fire-prevention ; illustrations of everything from home to the skyscraper; many plans; archi- tectural detail plates 10 x 14 a feature. Issued Monthly at $2.00 a Year Send for Sample Copy and Clubbing Offer COMPLETE CATALOGUE OF BOOKS ON REQUEST THE WM. T. COMSTOCK COMPANY 23 WARREN STREET, NEW YORK BUSINESS DIRECTORY. 1309 *48. Louisville Cement Co.; Cements and Limes; 325 W. Main St., Louis- ville, Ky. *49. Lukens, Lewis N. ; Reinforcement; Real Estate Trust Bldg., Phila- delphia, Pa. *50. Marion Malleable Iron Works; Bar Couplings; Marion, Ind. *51. Marsh-Capron Mfg. Co.; Mixers; 465 Old Colony Bldg., Chicago, 111. *52. Michigan Portland Cement Co.; Chelsea, Mich. *53. Miles Mfg. Co.; Concrete Machinery; Jackson, Mich. 54. Milwaukee Concrete Mixer Co.; 762 30th St., Milwaukee, Wis. 55. National Lime Manufacturers' Association; Oliver Bldg., Pittsburg, Pa. 56. National Mixer Co.; 300 6th St., Oshkosh, Wis. 57. National Wire Cloth Co.; Ties for Reinforcing Bars; Sandusky, O. 58. Nazareth Cement Co.; Nazareth, Pa. 59. New Egyptian Portland Cement Co.; Detroit, Mich. *60. New England Column Clamp Co.; 220 Devonshire St., Boston, Mass. 61. Newaygo Portland Cement Co.; Grand Rapids, Mich. *62. North Western Expanded Metal Co.; Reinforcement; Chicago, 111. *63. Northwestern States Portland Cement Co.; Mason City, la. 64. Ogden Portland Cement Co.; Ogden, Utah. 65. Oklahoma Portland Cement Co.; Ada, Okla. 66. Olsen Concrete Mixer Co.; 302 Olsen St., Elkhorn, Wis. 67. Ottawa Silica Co.; White Sand for Facing Concrete, etc.; Ottawa, 111. *68. Page Woven Wire Fence Co.; Reinforcement; Monessen, Pa. 69. Peerless Portland Cement Co. ; Union City, Mich. 70. Peninsular Portland Cement Co.; Jackson, Mich. 71. Penn-Allen Cement Co.; Allentown, Pa. 72. Phoenix Portland Cement Co.; Nazareth, Pa. 73. Pioneer Asphalt Co., The ; Lawrenceville, 111. *74. Pittsburg Crushed Steel Co.; Concrete Floor Hardener and Facing; A. V. R. R. & 61st St., Pittsburg, Pa. 75. Portland Cement Co. of Utah; Salt Lake City, Utah. *76. Sackett Screen & Chute Co., H. B. ; Industrial Cars and Track, Screens and Elevators; 1679-1691 Elston Ave., Chicago, 111. 77. St. Mary's Cement, Ltd.; Toronto, Canada. 78. San Antonio Portland Cement Co.; San Antonio, Texas. *79. Sandusky Portland Cement Co.; Waterproof Compound, Portland Ce- ment, White Portland Cement; Cleveland, O. *80. Sanitary Composition Floor Co., Inc.; 120 Plum St., Syracuse, N. Y. *81. Schaefer Manufacturing Co.; Concrete Mixers; Berlin, Wis. *82. Security Cement and Lime Co.; Portland Cement, Hydrated Lime; Hagerstown, Md. Also Washington, Baltimore and Pittsburg. *83. Smith Co., T. L. ; Mixers; 1149 32d St., Milwaukee, Wis. 84. Southwestern Portland Cement Co.; El Paso, Texas. 85. Spackman Engineering Co., Henry S. ; Concrete and Cement Testing; 2024 Arch St., Philadelphia, Pa. 86. Standard Portland Cement Co. ; Charleston, S. C. 87. Standard Portland Cement Corporation; San Francisco, Calif. 88. Superior Portland Cement Co.; Cincinnati, O. 89. Sykes Metal Lath and Roofing Co.; Lead Coated Metal Lath; 500 Wal- nut St., Warren, O. 90. Texas Portland Cement Co.; Cement, Texas. 91. Tidewater Portland Cement Co.; Baltimore, Md. *92. Tompkins, Calvin ; Plaster, Crushed Stone, Brick, Aggregates graded at Quarry; 30 Church St., New York, N. Y. 93. Trinity Portland Cement Co.; Dallas, Texas. *94. United States Portland Cement Co.; Coors BMg., Denver, Colo. *95. Universal Road Machinery Co. ; Crushers, etc. ; Kingston, N. Y. 96. Virginia Portland Cement Co.; Fordwick, Va. 97. Wabash Portland Cement Co.; Ford Bldg., Detroit, Mich. 98. Wege Concrete Machinery Co., E. ; 118 S. Second St., La Crosse, Wis. 99. Western States Portland Cement Co.; Independence, Kan. *100. Westmoreland Chemical and Color Co.; Oxides of Iron and Venetian Reds; 925 Chestnut St., Philadelphia, Pa. 101. Wolverine Portland Cement Co.; Coldwater, Mich. 102. Wyandotte Portland Cement Co.; 1575 Ford Bldg., Detroit, Mich. * Names indicated by asterisks are those of firms which have favored us with verification or correction of their listings. 1310 ADVERTISEMENTS. MUNICIPAL ENGINEERING The World's Leading Municipal Publication Established 1890 The authority on all matters pertaining to the physical im- provement of cities and towns. Read by City Engineers, Con- tractors and heads of all mu- nicipal departments. 200 Pages Monthly ; $2.00 per Year Send for Sample Copy Engineering Publishing Company Main Office Indianapolis, Ind. Eastern Office Western Office 526 World Building 1962 Transportation Building New York City Chicago, III. BIBLIOGRAPHY. 1311 BIBLIOGRAPHY. The following list of books makes no pretensions to completeness. It aims simply to be usefully suggestiv to the general civil engineer. Abbreviations. AC Archibald Constable & Co., Ltd., 10 Orange St., Leicester Square, London, W. C. CH Chapman & Hall, Ltd., 11 Henrietta St., Covent Garden, London, W. C. CL Crosby, Lockwood & Son, 5 Broadway, Westminster, London, S. W. LG Longmans, Green & Co., Fourth Ave. and 30th St., New York, N. Y. MC The Myron C. Clark Publishing Co., 608 S. Dearborn St., Chicago, 111. McG McGraw-Hill Book Co., Inc., 239 W. 39th St., New York, N. Y. S E. & F. N. Spon, Ltd., 57 Hay market, London, S. W., England. - VN D. Van Nostrand Co., 23 Murray St., New York, N. Y. W John Wiley & Sons, Inc., 432 Fourth Ave., New York, N. Y. Strength of Materials. *American Society for Testing Materials. Index to "Proceedings," 1898 to 1912. Am. Soc. for Testing Materials, University of Pennsylvania, Philadelphia, Pa. *American Society for Testing Materials. Year Book. 500 pp. 6X9. Cloth. 1914. Am. Soc. for Testing Materials, University of Pennsylvania, Philadelphia, Pa. Bovey, Henry T. . Strength of Materials and Theory of Structures. 4th Ed., rewritten and enlarged. 981 pp. 943 figs. 8vo. Cloth. $7.50. 1907. W. Burr, Wm. H. . The Elasticity and Resistance of the Materials of Engin- eering. 6th Ed., rewritten and enlarged. 1100pp. 8vo. Cloth. $7.50. 1904. McG; W. Fuller, Charles E. , and Johnston, William A. . Applied Mechanics. Vol. II. Strength of Materials. W. Hatt, William Kendrick , and Scofield, H. H. . Laboratory Manual of Testing Materials. 135 pp. 28 ills. 7% X5M- Cloth. $1.25. 1913. McG. international Association for Testing Materials. (Foreign papers, etc., have been translated into English.) Proceedings of the Sixth Congress, New York, 1912. 2vols. 2200pp. Ill'd. 6X9. Cloth, $8.00; paper, $7.00. McG, S. Kent, William. Strength of Materials. 2d Ed. 18mo. Boards. $0.50. 1905. VN. Kidwell, Edgar, and Moore, Carlton F. . Tables of Safe Loads. 57 pp. 6X9. Paper. $0.50. McG. *Merriman, Mansfield . Strength of Materials. 6th Ed., revised and enlarged. 16th thousand. 179 pp. 54 figs. 5X7^- Cloth. $1.00. 1912. W, CH. Morley, Arthur. Strength of Materials. 3d Ed. 506 pp. 244 ills. 6X9. Cloth. $2.50. LG. Murdock, H. E. . Strength of Materials. 2d Ed., revised and enlarged. 367pp. 156 ills. 5X7^. Cloth. $2.00. 1914. W, CH. *Unwin, William Cawthorne . The Testing of Materials of Construction. 3d Ed. 490pp. 206 ills. 5 plates. 5^X8^. Cloth. $5.00. 1910. Winslow, Benj. E. . Tables and Diagrams for Calculating the Strength of Beams and Columns. 53 pp. 19 full-page plates. 12 X9, oblong. Cloth. $2.00. McG. Wood, De Volson . A Treatise on the Resistance of Materials. 328 pp. 129 figs. 8vo. Cloth. $2.00. 1904. McG, W. Concrete and Reinforced Concrete. Andrews, E. S. . Elementary Principles of Reinforced Concrete Construc- tion. 210pp. 57 ills. 5X7^. Cloth. $1.25. Ballinger, Walter F. , and Perrot, Emile G. . Inspector's Handbook of Reinforced Concrete. 72 pp. 6 folding plates. 4% X7. Flex, leather. $1.00. 1909. AC, McG. Brooks, John P. . Reinforced Concrete. 230 pp. 87 figs. 6 X9. Cloth. $2.00. 1911. McG. Buel, Albert W. , and Hill, Charles S. . Reinforced Concrete. 2d Ed. t revised and enlarged. 512pp. 357 ills. 8 plates; tables; 6X9. Cloth. $5.00. 1906. McG. * ** Belie vd to be specially useful. 1312 ADVERTISEMENTS. A combination of Cement Age, ot New York, Concrete, Detroit, and Concrete Engineering, Cleveland CONCRETE is a Monthly Magazine. It is for the man who designs or speci- fies concrete who builds with it who superintends concrete construction for every practical man who has anything to do with concrete. It covers engineering practice, architectural development, con- struction methods. It is written by men who know is the product of practical experience it gets at the nub of the matter It Tells How. It is more than a monthly magazine. It is an Institution, bent on the solution of your individual problems. The yearly subscription price is a trifle measured by its earning power in dollars. $1.50 for twelve months in the United States; 50 cts. more to Can- ada; $1.00 more to foreign countries. Ask for a specimen copy. Concrete- Cement Age Publish- Detroit ing Company Michigan BIBLIOGRAPHY. 1313 Concrete, etc., Cont'd. Cochran, Jerome . Reinforced Concrete Field Handbook. 133 pp. 27 ills. Tables. 3^X5%. Leather. $1.00. 1915. Concrete-Cement Age Pub. Co., 310 New Telegraph Bldg., Detroit, Mich. *Considere, A. . Reinforced Concrete. Translated by Leon S. Moisseiff. 2nd Ed., enlarged. 242 pp. 32 figs. $2.00. 1907. McG. Dodge, G. F. . Diagrams for Designing Reinforced Concrete Structures. 112 pp.; 43 diagrams. 14^X12%. Boards. $4.00. MC, S. *Eddy, Henry T. , and Turner, C. A. P. . Concrete-Steel Construction. Parti; Buildings. 438pp. 99 ills. 6^X9. Cloth. $20.00. C. A. P. Turner, Minneapolis, Minn. *Gilbreth, Frank B. . Concrete System. 184 pp. 220 ills. 10 folding plates. 8^X11. Flex. mor. $5.00. AC, McG, W. Gillette, Halbert P., and Hill, Charles S. . Concrete Construction, Meth- ods and Cost. 700 pp. 310 ills. Cloth. $5.00. 1908. MC. Hill, Charles S. . Concrete Inspection. 187 pp. 15 ills. 3^X6^- Cloth. $1.00. 1909. MC, S. Hool, George A. . Reinforced Concrete Construction. Vol. I; Fundamental Principles. 254pp. 88 ills. 6^ X9M- Cloth. $2.50. 1912. Vol. II; Retaining Walls and Buildings. 675 pp. 412 ills. 34 plates, etc. - 6 X9. Cloth. $5.00. 1913. McG. Marsh, Charles F. . A Concise Treatise on Reinforced Concrete. 233 pp. 67 ills. 5^X8%. Cloth. $2.50. 1910. VN, AC. Marsh, Charles F. , and Dunn, William . Manual of Reinforced Con- crete, and Concrete Block Construction. 290 pp. 113 ills. 52 tables. 4X6^. Flex, leather. $2.50. 1910. VN. McCullough, Ernest . Reinforced Concrete; A manual of Practice. 136 pp. 28 ills., and frontispiece. 5X8. $1.50. 1908. Cement Era Pub- lishing Co., Chicago, 111. Mensch, L. J. . Architects' and Engineers' Handbook of Reinforced Con- crete Construction. 217 pp. 172 ills., many tables. $2.00. 1904. *M6rsch, Emil . Translated by E. P. Goodrich. Concrete Steel Con- struction. 3rd German Ed., 1908, revised and enlarged. Over 400 pp. 350 ills. 45 tables. 2 inserts. 7^X10. Buckram. $5.00. 1909. AC, McG. Potter, Thomas . Concrete: Its Uses in Building. 3d Ed., revised and enlarged. 358 pp. 138 ills. 5^ X8%. Cloth. $3.00. 1908. VN. Reid, Homer A. . Concrete and Reinforced Concrete Construction. 906 pp. 715 ills., 70 tables. 6 X9. Cloth. $5.00. 1906. MC. Rings, Frederick . Reinforced Concrete in Theory and Practice. 200 pp. 203 ills. 5M X8. $2.50. 1910. *Sabin, Louis Carlton . Cement and Concrete. 2d Ed., revised and enlarged. 665 pp. Ill'd. 161 tables. $5.00. 1907. McG. Sutcliffe, G. L. . Concrete: Its Nature and Uses. 2nd Ed., revised and enlarged. 396 pp. Ill'd. 12mo. Cloth. $3.50. CL. Taylor, Frederick W. , and Thompson, Sanford, E. . Concrete Costs. 1st Ed. 731pp. 82 figs. 166 tables. 5J^ X8. Cloth. $5.00. 1912. W, CH. **Taylor, Frederick W. , and Thompson, Sanford E. . A Treatise on Concrete, Plain and Reinforced. 2d Ed., revised and rewritten. 848 pp. 253 ills. 6X9. Cloth. $5.00. 1911. W, CH. Trautwine Jr., John C. , and Trautwine 3d, John C. . Concrete. Re- printed from Trautwine's "Civil Engineer's Pocket-Book," 2d Issue. 200 pp. 60 figs. 4%X7^. Cloth. $1.00. 1915. Trautwine Com- pany, 257 S. 4th St., Philadelphia, Pa. **Turneaure, F. E. , and Maurer, E. R. . Principles of Reinforced Con- crete Construction. 2d Ed., revised and enlarged. 439 pp. 164 figs. 17 plates. 5H X9 1 A- Cloth. $3.50. 1909. W, CH. Warren, F. D. . Handbook on Reinforced Concrete. 2d Ed., revised. 268 pp. Tables and diagrams. 5 X7. Cloth. $2.50. 1907. VN, CL. Watson, Wilbur J. . General Specifications for Concrete Work; as Applied to Building Construction. 46 pp. 6M X9>. Stiff paper. $0.50. 1908. Wilbur J. Watson, Citizens' Bldg., Cleveland, O. Webb, Walter Loring , and Gibson, W. Herbert . Reinforced Concrete. 150 pp. 140 ills. $1.00. * ** Believd to be specially useful. 1314 ADVERTISEMENTS. The Following Technical Works on Concrete Con- struction are Free If you do not possess copies of the follow- ing books, and will address us, we will gladly forward any or all of them, carriage charges prepaid : Concrete Construction for the Home and Farm 160 Pages Reinforced Concrete in Factory Construction 246 Pares Concrete in Railroad Construction 228 Pages Concrete in Highway Construction 136 Pages Atlas White Book 62 Pages The Atlas Portland Cement Company New York Chicago Philadelphia Minneapolis Des Moines Boston St. Louis BIBLIOGRAPHY. 1315 Concrete Blocks. Rice, H. H. , and Torrance, Wm. M. . Concrete Blocks: Their Manu- facture and Use in Building Construction. 122 pp. Ill'd. Demy 8vo. $1.50. 1907. AC. Whipple, Harry . Concrete Stone Manufacture. 255 pp. Ill'd. 4 X7. Leather. $1.00. Concrete-Cement Age Publishing Co., Detroit, Mich. Cements, Limes, Plasters, etc. Butler, David B. . Portland Cement; Its Manufacture, Testing and Use. 2d Ed., revised. 406 pp. 97 ills. 5 1 A X8%. Cloth. $5.00. *Eckel, Edwin C. . Cements, Limes, and Plasters: Their Manufacture and Properties. 746 pp. 165 figs. 254 tables. 8vo. Cloth. $6.00. 1905. W. *Falk, Myron S. . Cements, Mortars and Concretes. 176 pp. Tables, plates and figs. 6 X9. Cloth. $2.50. 1905. MC. *Gillmore, Q. A. . Practical Treatise on Limes, Hydraulic Cements and Mortars. 334 pp. 56 ills. 8vo. Cloth. $4.00. 1905. VN. *Jameson, Charles D. . Portland Cement. 8vo. Cloth. $1.50. VN. *Le Chatelier, H. . Experimental Researches on the Constitution of Hy- draulic Mortars. Translated by J. L. Mack. 140 pp. $2.00. 1907. McG. Redgrave, Gilbert R. , and Spackman, Chas. . Calcareous Cements. 2d Ed. 254 pp. 63 plates. $4.50. Spalding, Frederick P.. Hydraulic Cement. 310 pp. 34 figs. 12mo. Cloth. $2.00. 1907. W. Taylor, W. Purves . Practical Cement Testing. 330 pp. 142 ills. 58 tables. 6X9. Cloth. $3.00. 1906. MC. * ** Believd to be specially useful. This book on CONCRETE is a reprint from t THE INCOMPARABLE TRAUTWINE (See Introduction to Engineer Field Manual, Corps of Engineers, U. S. Army, 1912) THE CIVIL ENGINEER'S POCKET-BOOK Thum-indext, $5.OO net SPANISH TRANSLATION (Without Thum-index), $5.OO net TRAUTWINE COMPANY Advertising Department 257 South Fourth Street, Philadelphia 1316 ADVERTISEMENTS. Building Id EACH number of The National Builder is replete with valu- able information for everyone interested in building. The topics dis- cussed in its pages embrace every feature of general buildingconstruction. Here is a veritable feast of new ideas, new plans, new materials. THE NATiqfi^L. BUILDER fliBHH^B Circulation 24,OOO has long been recognized as a sure guide to better building. It covers the field thoroughly with splendid editorials by recognized authors; no architectural or construc- tion detail is overlooked. There are interesting estimates; authoritative comparisons of cost; a splendid mass of usable data on all classes of construction. Its advertising pages are used by the best manufacturers and consequently form a splendid directory of building materials, equip- ment, tools and supplies of all kinds. Twelve Big Numbers Subscription Price, $1.50 per Year THE NATIONAL BUILDER 537 So. Dearborn St., Chicago INDEX. The numbers refer to the pages; those in parentheses, to paragraphs. In the alphabetical arrangement, minor words, as "and," "between," " in," " on," " through," etc., are neglected. See also table of Contents, p vi. Abrasion Beam. A. Abrasion, of mortar and concrete, 1136. Absorption, by concrete, 1137, 1206 (39). Accelerated tests for cements, 938, 945. Acid, in mortar, 1135, 1136, 1138. Adhesion, of concrete, 947 / (36), 947 j (67), 1090 (39), 1106 (37), 1111, 1126, 1128 (6), 1129 (9, 16), 1139, 1196 (113, etc), -unit, 1126. Aggregate, Aggregates, 1084, 1136, 1137, 1186. See also the kind in question, analysis, 946. cinder, 1084 (8), 1103 (1), 1137, 1187 (12), 1197 (127). cyclopean-, 1085, 1090 (40), 1187 (15). effect of on weight of concrete, 1103 (1). grading, 946, 1088, 1089. quartering, 946 (4). for reinforced concrete, 1110 (7). washing, 1091 (15). Alum, and clay, 1135, 1171. and soap, for waterproofing, 1105 (20), 1137. Alumina, in cement, 930. Analysis, of sand, etc, 946. Anchor plates, in reinforced con- crete, 1129. Arch, Arches, cpncrete , cost, 1210 (60). Artificial stone, concrete, 1084, 1193. Asphalt, waterproofing, 1105. B. Bag, cement, 935 (56), 940 (1). 1186 (3, 4). Ballast. See Aggregate. Bar, Bars. See Reinforcement, bars. Barrel, cement, 935 (51), 940 (1), 1186 (3). Beam, Beams, axis, neutral, 1138. concrete , C9ntinuous , 1126, 1127, 1200. diagonal stresses in , 1125. forms, 1096. max stresses in , 1125. reinforced, 1115, 1198. See also Beams, reinforced con- crete. shear in, 1123. shear reinforcement, 1124, 1126 (55-57), 1128 (3). specifications, 1198. strength of ,1115. stresses in , 1115, 1125. diagpnal , 1125. maximum , 1125. continuous , 494 g, 1126, 1127, 1200. reinforced concrete, specfns, 1200. deflections, reinforced concrete , specfns, 1201 (186). diagonal stresses in , 494 a, 494 e, 1125. floor , 1198. See also under Floors. horizontal shear in , 494 c, 494 e. loads, suddenly applied , 461. maximum stresses in , 494 a, 494 e. neutral axis in , 1138. INDEX. Beam Cement. Beam, Beams continued. principal stresses,* 494 c, 494 g. reinforced concrete , 1115, 1198. adhesion, 1106 (37), 1111, 1126, 1128 (6), 1129 (9, 16), 1139, 1196. axis, neutral , 1138. continuous, 1126, 1127, 1200. cost, 1122 (20 d), 1210 (57, 58). deflections, 1201 (186). design, 1120. diagonal stresses in , 1125. double reinforcement, 1127. forms for, 1096. investigation, 1119, 1123. maximum stresses in , 1125. moments in, 1116 (7), 1117, 1118 (14, 17), 1121, 1122 (23), 1122 (30), 1123, 1200. neutral axis, 1138. ratio of steel and concrete areas, 1116 (5, 6), 1117, 1118 (11, 12, 15, 16), 1121. shear in , 1123. shear reinforcement, 1124, 1126 (55-57), 1128 (3). specfns, 1198. stirrups, 1124, 1128 (3), 1139. spacing, 1199 (162). stresses in, 1116 (8), 1117, 1118 (13, 15, 16) 1121, (32), , , , 1122 (21-23), 1123 1125, 1127 (66). diag9nal , 1125. maximum , 1125. T-sections, 1122, 1199 (171). tension in upper side, 1127. theory, 1115 (4). shear, 494 c, 494 e, 1123. strength, strengths, 1115. stress, stresses, in , diagonal, 494 a, 494 e, 1125. maximum , 494 a, 494 e, 1125. principal , 494 c, 494 g. suddenly loaded , 461. vertical shear in , 494 c, 494 e. Blocks, concrete , 1203, 1204. Boiling tests for cement, 938, 945. Bond. See Adhesion. Brass, effect of mortar, etc, on , 1136. Brick, Bricks, incrustations, 947 j (69). -work, mortar required for , 947 d. Briquet, Briquets, cement , 941 (4), 944 (10). Broken stone, 1084, 1085, 1088, 1137, 1207 (10). for concrete. See Aggregate. Building, Buildings, concrete , cost, 1210 (61-3). C. Calcium chloride, 947 g (45 c), 1107 (56), 1135. Carbonic acid, effect on concrete, 1138. Cement, 930-945, 1086 (8), 1135. For strength, setting, etc, per- taining to mortar, see under Mortar. accelerated tests for , 938, 945 adulterants, 934 (39). age, 935 (60), 1135. analyses, 933 (32), 942 (4, 8). bags, 935 (56), 940 (1), 1186 (3. 4). barrels, 935 (51), 940 (1), 1186 (3). boiling test for , 938, 945. brand, specfns, 1186 (1). brick-dust, 931 (6). briquet, 941 (4), 944 (10). in bulk, 935 (59). calcium chloride, 947 a, 1107 (56), 1135. cementation index, 934 (38). chemical action of , 1135. analysis, 933 (32), 942 (4, 8). tests, 936, (64). chemistry, 933 (32). clay in, 930, 1135. color, 934. composition, 933 (32), 942 (4, 8). cost, 1207 (7). deterioration, 936 (60, 61). effects of on . See material or agency in question, under Cement, elements, 930 (2), 933 (32), 942 (4, 8). Erz , 933 (30). experiments, 1135. exposure, 936 (60, 61), 947 h (51), 1135, 1186 (4). factor, lime , 934 (37). fineness, 934, 940 (3), 941 (3), 943 (6), 1135. flashing, 936 (63), 947 A (51). grout, 1102 (128), 1105 (22). gypsum in, 947 g (45 a), 947 h (55), 1135. hardening, 930, 947 /, 947 h, 947 t. hydraulic index, 933 (33). lime, 933 (31). modulus, 933 (35). index, cementation, 934 (38). hydraulic, 933 (33). ingredients, 930 (2), 933 (32), 942 (4, 8). iron ore. 933 (30). lime in, 930, 942 (S). See also Lime. lime factor, 934 (37). lime, hydraulic, 933 (31). INDEX. Cement Concrete. Cement continued. lime sulphate in , 947 g (45 a), 947 h (55), 1135. loam in , 1135. magnesia in , 930 (4) , 940 (3) , 942 (8). manufacture, 931. mix, typical , 1135. modulus, hydraulic, 933 (35). mortar. See Mortar, in mortar, 947 d. natural , 1135. in concrete, 1086, 1186, 1191 (56). uses, 932 (21), 1186 (1). needle, Vicat , 947 g (43). packages, 935 (50), 940 (1), 1186 (3, 4). Portland, manufacture, 931 (14). uses, 932 (21), 1186 (1). white , 933 (29). properties, 934, 940 (3). See also the property in question. Puzzolan , 930 (4), 932. quantities required and used, 1086, 1135. requirements, 937, 940, 942. restoration, 936 (62). rock, 930 (4). Roman, 931 (12). Rosendale , 931 (11). samples, 940, 942 (1). setting. See Concrete, setting, and Mortar, setting, shipment, 935 (59), 940 (1), 1186 (3). silica, 932 (25), 1135. slag, 930, 932 (22). water required, 947 / (38). soundness. See under Mortar, specific gravity, 934 (46), 940 (3), 942. specifications, 937, 940, 942, 1184, 1186. Am Soc Civ Engrs, 942. Am Soc Testg Materials, 940. Engng Standds Comm of Gt Brit, 940. U. S. Engr Officers, 937. storage, 936 (60, 61), 947 h (51), 1186 (4). strength. See under Mortar, sulfuric acid in, 940 (3), 942 (8), 1135. testing machines for , 938. tests, 936, 937, 940, 942, 947 i, 1186 (2). typical mix, 1135. Vicat needle, 947 g (43). weight, 934, etc. white, 933 (29). Cementation index, 934 (38). Chloride, calcium , 947 g, 1107 (56), 1135. Cinder, concrete, 1084 (8), 1103 (1), 1137, 1187 (12), 1197 (127). Clay and alum, 1135, 1171. in cement, 930, 1135. in concrete, 1084 (11), 1135, 1186 (6). in mortar, 947 /, 1135. in sand, 1135, 1186 (6). test for, 947 c (32). Clearance, in reinforced concrete, 1196. Clinton, welded wire, 1132. wire lath, 1132. Clips, for cement briquets, 941 -, 944. Closet, moist , 945. Coefficient, Coefficients. See also the subject in question, expansion , in reinforced concrete, 1110 (9), 1138. safety. See the construction or material in question, uniformity , 947, 1135. Cold, effect of, on concrete, 1094 (57), 1102 (133), 1107 (44), 1138, 1191. -twisted lug bar, 1131 (22). -working of iron and steel, 1129 (9). Column, Columns, concrete, 1112, 1113, 1138, 1197. footings for , 1114. forms, 1095 (64). hooped, 1113, 1198 (144, etc), reinforced , 1112. See Col- umns, reinforced concrete, strength of , 1138. eccentric loading, 1198. footings, 1114. hooped, 1113, 1198 (144, etc), reinforced concrete , 1112, 1134, 1197. footings for , 1114. forms, 1095. formula, Rankine's , 1113 (10). hooped, 1113, 1198 (144). reinforcement, 1134, 1197 (131, etc). Concrete, 1084. For adhesion, set- ting and other properties per- taining to mortar, see also under Mortar, cement . See also under structure in question. See also Reinforced concrete, abrasion, 1136. absorption, 1137, 1206 (39). acids, effect of, 1108 (69), 1138. adhesion, 947 / (36), 947 j (67), 1090 (39), 1106 (37), 1111, 1126, 1128 (6), 1129 (9, 11, 16), 1139, 1196. age, effect of, 947 i (64), 1137. aggregates. See Aggregates, air, effect of, 1138". Concrete, alum Concrete, loads. Concrete continued. alum and soap treatment, 1105 (20), 1137. arches, cost, 1210 (60). asphalt, for waterproofing , 1105 (25). beams. See Beams, concrete ; Beams, reinfd concrete ; and Floors. behavior, 1137. blocks, hollow , for buildings, specfns, 1204. practice, 1203. bond. See Concrete, adhesion. broken stone, 1084, 1085, 1088, 1137, 1207 (10). See also under Aggregate, and Stone. building blocks, specfns, 1204. buildings, cost, 1210 (61-3). burning, effect of , 1108 (62, 63, 65), 1138. carbonic acid, effect of , 1138. cement for, 930, 1086 (8). chemical effects, 1108. churning, specfns, 1189. cinder, 1084 (8), 1103 (1), 1137, 1187 (12), 1197 (127). clay in, 930, 947 /, 1084 (11), 1135, 1186 (6). coefficient, expansion, 1110 (9), 1138. cold, effect of, 1094 (57), 1102 (133), 1107 (44), 1138, 1191. See also Concrete, freezing. coloring, 1103, (137). columns. See Columns, con- crete ; and Columns, rein- forced concrete . compacting, 1100, 1137, 1189, 1190 (44). cost, 1210 (47, 48). compressive strength, 1106 (32), 1193 (81,84,85). conductivity, thermal , 1138. consistency, 1090, 1094 (54), 1187 (22). continuous beams, 1126, 1127, 1200. contraction, 947 h (56). coping, 1192 (76). cost of , 1207. cracks in , 1108 (61). crusher dust, 947 e (25), 1186 (7). cyclopean, 1085, 1090 (40), 1187 (15). dehydration, 1108 (63). density, 1088, 1089, 1137. depositing. See Concrete, plac- ing . dry . See also Concrete, consis- tency, cost, 1210 (54). ductility, 1111 (16), 1137. dumping, 1093 (52). See also Concrete, placing . durability, 1137. Concrete continued. effect of air, etc, on . See Con- crete, air, etc. elastic limit, 1138. elastic modulus, 1106, 1110, 1111, 1138, 1194. electrolysis, 1108 (68), 1138, 1139. elongation, 1111 (16). expanded metal, 1132 (37). expansion, 947 h (56), 1108, 1137, 1110 (9), 1138. experiments, 1135. fatigue, 1138. finish, 1102, 1137, 1192. cost, 1210 (50-52). fire, effect of, 1108 (62, 63, 65), 1138, 1139. floors. See Floors, and Beams, reinforced concrete . flow of, 1137. forms. See Forms. foundations, leveling, 1086 (5). freezing, 1094 (57), 1102 (133), 1107 (44), 1138, 1191. calcium chloride, 1107 (56). forms, removal of , 1191 (58). protection, 1107. friction, 1139. frost, see Concrete, freezing, frozen , removal of , 1191 (55). gases, effect of on , 1108 (72). girders. See also Floors, con- crete ; Beams, concrete . forms, 1096. grading, 1089. gravel for . See Gravel, grouting, 1102 (128), 1105 (22). handling and mixing, 1090. heat, effect of, 1106 (40), 1107, 1108 (62, 63, 65), 1138. impermeability, 1088 (22), 1103, 1136, 1138, 1192, 1193 (78). ingredients. See also under ma- terial in question, handling, 1090. heating, 1107 (53). measurement, 1091 (10), 1093 (38), 1187 (21). required, 1087. storage, 1091 (5). inspection, cost, 1210 (49). in iron cylinders, expansion, 1108 (60). joints in, 1099, 1105 (21), 1108 (61), 1190. laitance, 947 / (36), 947 k (71), 1137. large stones in, 1085, 1090 (40), 1187 (15). law of powers, 1138. layers, 1094 (53), 1190 (40, 43, 44). for leveling foundations, 1086 (5). lifting, 1092 (24). limit, elastic, 1138. loads, allowable , specfns, 1193 (83). INDEX. Concrete, loam Concrete, stress. Concrete continued, loam in, 1084 (11). manipulation, specfns, 1189. See also Concrete, placing ; Con- crete, mixing ; Concrete, handling . and masonry, in combination, 1086 (7). mass, cost, 1210 (56). materials. See Concrete ingre- dients. -metal. See Reinforced con- crete, and Reinforcement, metal in . See Reinforcement. corrosion. 1110 (5), 1136. mica in , 1135, 1186 (6). mix, natural , 1087. mixers, 1092, 1101 (125), 1208 (27) . See also Concrete mix- ing. mixing, 1092, 1137, 1188. batch, 1188 (29). cost, 1208. hand, 1188 (28, 30). machine, 1092 (32), 1188 (28). See also Concrete mixers, measurement, 1187 (21). mixers. See Concrete mixers, for sidewalks, 1202. water, 1090, 1136, 1187. weather, effect of , 1092 (30). wind, 1092 (30). modulus, elastic, 1106, 1110, 1111, 1138, 1194. rupture , 1106 (38). moistening, 1190 (38), 1191. molded, 1204. molds for . See Forms, mortar for . See Mortar, natural cement , 1086. freezing, 1191 (56). uses, 1086, 1186. natural mix, 1087. night work, specfns, 1189 (37). oil, effect of, 1108 (71), 1138. painting, 1103 (138), 1137. paving, 1201. percolation. See Concrete, per- meability, permeability, 1088, 1103, 1136, 1138, 1177, 1192, 1193 (78). permit, specfns, 1196. picking, 1102 (129). in piles, 1101 (124). placing, 1093, 1137, 1189. See also Concrete, handling, cost, 1208, 1209. for sidewalks, specfns, 1202. underwater, 1100, 1190. in bags, 1101 (119). plain , 1086. See also other sub- heads of concrete, plants, 1090 (1), 1101 (125). plastering, 1102 (127), 1192 (66), 1193 (79). plasticity, 1137. Concrete continued. plums in, 1085, 1090 (40), 1187 (15). Potenzgesetz, 1138. powers, law of , 1138. practice, 1135. pressure, effect of , 1138. proportions, 1086, 1089. measurement, 1187 (21). in reinforced work, 1087 (13). protection, 1107. for sidewalks, 1202, 1203. rain, 1191. rammers, 1189 (37). ramming, 1100, 1137, 1189, 1190 (44). cost, 1210 (47,48). rehandling, specfns, 1189 (37). rehydration, 1108 (64). reinforced . See Reinforced con- crete, and Reinforcement, requirements, 1193. resistance to fire, 1108 (62, 63, 65), 1138. retaining walls, cost, 1210 (59). re-tempering, 1137, 1189 (37). salt in, 1107 (55), 1108 (67, 70). sand. See Sand, sea water, effect of, 947 k, 1108 (67), 1136, 1138. setting, 1090 (39), 1106, 1137. See also Mortar, setting, sewage, effect of on, 1138. shear in , 1123. shearing strength, 1106 (36), 1138, 1173, 1193 (82). shrinkage, 947 h (56), 1137. sidewalks, specfns, 1201. soap and alum treatment, 1105 1137. See also Sound- sou (20), 1137. ndness, specifications, 1184, 1186. spreading, cost, 1210 (47). steam, effect of , 1138. -steel. See Reinforced concrete, steel for and in . See Rein- forced concrete; Reinforce- ment, stirrups, 1124, 1128 (3), 1139, 1199 (162). stone for, 1084, 1085, 1088, 1137, 1207 (10). See also under Aggregate and Stone, storage, cost, 1208. strength, 1106, 1137, 1138, 1193 (81, 84, 85). compressive , 1106 (32), 1193 (81, 84, 85). required, 1193. shearing, 1106 (36), 1138, 1173, 1193 (82). tensile, 1106 (31, 36), 1138. torsional , 1173. transverse , 1106 (38). stress and stretch, 1138. INDEX. Concrete, stresses Form. Concrete continued , stresses, allowable, 1193 (83). stretch, 1111 (16). subaqueous, 1100- sunshine, effect of , 1138. superintendence, cost, 1210 (49). surface finish, 1102, 1137, 1192. Sylvester process, 1105 (20), 1137. temperature, effect of , 1094 (57), 1106 (40), 1107 (44), 1108 (62, 63, 65), 1138. tensile strength, 1108 (31, 36), 1138. tests, 1109, 1200. thawing, 1107 (46, 47). thermal conductivity, 1138. tooling, 1102 (129). torsional strength, 1173. transportation, cost, 1208. transverse strength, 1106 (38). tremie, 1100 (116). voids in , 1088, 1137 volume of mortar, 1137. excess required, 1088. walls, forms for , 1096 (68). retaining , cost, 1210 (59). washing, cost, 1208 (18), 1210 (51). in water, 947 A;, 1100, 1190. water, effect of , 1138. mixing, 1090, 1136, 1187. salt, 1108 (67). sea, 947 k, 1108 (67), 1136, 1138. waterproofing, 1104, 1192, 1193 (78). See also Concrete, per- meability, watertightness. See Concrete, permeability, weather, 1191. weight, 1103 (1). wet , cost, 1210 (54). wetness. See Concrete, consis- tency. Conductivity, thermal, 1138, 1139. Considere, hopped columns, 1113 (15). Consistency. See under Concrete and Mortar. normal, 943 (7), 947 g (43). Continuous beams, 494 g, 1126, 1127, 1200. Coping, 1192. Copper, effect of cement, mortar, etc, on, 1136. Corrugated bars, 1131 (24). Crusher, Crushers, dust, 947 e (25), 1186 (7). Cup bars, 1131 (25). Cyclopean concrete, 1085, 1090 (40), 1187 (15). Cylinder, Cylinders, iron , concrete in , 1108 (60). D. Deformed bars, 1110 (6), 1129 (15, 16), 1139, 1194. Depositing. See Concrete, placing. Dehydration, 1108 (63). Diagonal stresses in beams, 494 a, 494 e, 1125. Diamond bar, 1131 (26). Double reinforcement, 1127, 1199 (165-6). Dumping concrete. See Concrete, placing. Dust, crusher, 947 e (25), 1186 (7). E. Economy unit frame, 1133. Effective size, 947. Efflorescence, 947 j (69). Electrolysis, 1108 (68), 1138, 1139. Erz-cement, 933 (30). Evaporation, from mortar, 1136. Expanded metal, 1132 (37). Expansion of concrete, 947 h (56), 1108, 1137. Experiments, 1135, 1140. F. Factor, lime, 934 (37). safety . See the construction or material in question. Feret, R. , sand analysis, 947. Fineness. See Cement, Sand, etc. Fire, Fires, effect on concrete, 1108 (62, 63, 65), 1138. -proof work, reinforced concrete in , 1196 (120). Flashing, of cement, 936 (63), 947 h (51). Floor, Floors, forms, 1096 (67), 1098 (93). reinforced, 1198. Footings, for columns. See Columns. Form, Forms. for concrete, 1094, 1137, 1189. adhesion, 1099. beams, 1096. for blocks, 1203 (3). columns, 1095. cost, 1209. depreciation, 1209 (42). floors, 1096. for girders, 1096. lagging, 1096, 1189 (34). lumber for , 1097. reinforced , 1095. removal, 1099, 1191 (58, 61). shifting, cost, 1209 (42). INDEX. Form-Mix. Form, Forms continued, sidewalks, 1202. slabs, 1096. strength, 1098. tie-rods in , 1189 (36). walls, 1096 (68). Wiederholt system, 1096 (69). Foundation, leveling by concrete, 1086 (5). Frame, unit, 1133. Freezing, concrete. See Concrete, freezing. Frost, in concrete. See Concrete, freez- ing, forms, removal of , 1191 (58). G. Grading, aggregate, 1088, 1089. sand, 946. Granite, as aggregate, 1137. Granulometric analysis of sand, 946. Gravel, as aggregate, 1136, 1137. in concrete, 1084, 1136, 1137. -concrete, cost, 1210 (55). cost, 1207 (9). effective size, 947. quartering, 946 (4). screenings, 947 / (26), 946 (3), 1137. uniformity coefficient, 947. Grout, 1102 (128), 1105 (22). Gvpsum, 947 g (45 a), 947 h (55), 1135. H. Hardening, 930, 947 /, 947 h, 947 i. Havemeyer bar, 1131 (27). Heat, effect on concrete, 1107 (44), 1108 (62, 63, 65), 1138. Hooped columns, 1113, 1198 (144, etc). Horizontal shear, 494 c, 494 e. Hydraulic index, 933 (33). lime, 933 (31). modulus, 933 (35). I. Incrustation of walls, 947 j. Index, cementation , 934 (38). hydraulic, 933 (33). Iron, cement, mortar, etc, effect of- on , 1110, 1136, 1139. -ore cement, 933 (30). C14 J. Joint, joints, in concrete work, 1099, 1105 (21), 1108 (61), 1190. K. Kami trussed bar, 1133. L. for forms, 1096, 1189 (34). Laitance, 947 / (36), 947 k (71), 1137. Lath, rib, 1133. wire, 1132. Lead, effect of cement, mortar, etc, on, 1136. Lime, in cement, 930, 942 (8). factor, 934 (37). hydraulic, 933 (31). in mortar, 947 e, 947 /, 1135, 1136. quick and slack , 931 (7), 947 e (11, 12). stone. See Limestone. sulphate, 947 g (45 a), 947 ft (55), 1135. Limestone, as aggregate, 1137. in cement manufacture, 930 (4). crushed vs sand, 1135. screenings, 947 / (26). Loam, in cement, 1135. in concrete, 1084 (11). in sand, 1135, 1186 (6). test for, 947 c (32). Lug bar, 1131 (22). M. Magnesia, in cement, 930 (4), 940 (3), 942 (8). in mortar, 947 e (14). Masonry and concrete in combination, 1086 (7). incrustation of , 947 j. mortar required for , 947 d. pointing, 947 j (70). Maximum stresses in beams, 494 a, 494 e. Mechanical analysis of sand, etc, 946. Melan system, 1133. Metal, metals, effect of cement, etc, on , 1110 (5), 1136, 1139. expanded, 1132 (37). rib, 1132 (41). Mica, in mortar, 1135, 1186 (6). Mix, natural, 1087. IND^X. Mixers Mortar. Mixers, concrete, 1092, 1101 (125), 1208 (27). Mixing, concrete, 1092, 1137, 1188. See also Concrete, mixing. Modulus, hydraulic, 933 (35). Moist closet, 945. Moisture, in sand, 947 b, 1135, 1186 (6). Molded concrete, 1204. Molds. See Forms. Moments, in continuous beams, 494 g. in reinfd beams, 1116 (7), 1117, 1118 (14, 17), 1121, 1122 (23, 30), 1123, 1200. Monier system, 1132 (36). Monolith bar, 1131 (29). Mortar, abrasion, 1136. absorption, 1137, 1206 (39). accelerated tests for , 938, 945. acid in, 1135, 1136. adhesion, 947 / (36), 947 j (67), 1090 (39), 1106 (37), 1111, 1126, 1128 (6), 1129 (9, 16), 1139, 1196. aeration, 1136. age, 947 t (64), 1137. boiling test for, 938, 945. briquet, 941 (4), 944 (10). calcium chloride in , 947 g, 1107 (56), 1135. cement, 930, 947 d, 1136. cement in , 947 d. chemistry of , 947 d (2). clay in, 947 /, 1135. consistency, 947 /, 1136. effect on adhesion, 947 / (36). laitance, effect of on, 947 / (36). normal, 943 (7), 947 g (43). contraction of ,947 h (56), 1137. crusher dust in, 947 e (25), 1186 (7). density of, 1136. drying, 1108 (59). efflorescence, 947 j (69). evaporation from , ll36. expansion of, 947 h (56) 1108, 1136, 1137. experiments, 1136. finish, 947 j, 1102, 1137, 1192. freezing. See Concrete, freezing, grading, 1136. gypsum in , 947 g (45 a), 947 h (55), 1135. hardening, 930, 947 /, 947 h, 947 i. incrustation, 947 j (69). laitance, 947 / (36), 947 k (71), 1137. lime in, 947 e, 947 /, 1135, 1136. magnesia in , 947 e (14). metals, protection, 1110 (5), 1136, 1139. mica in , 1135, 1186 (6). Mortar continued mixing, 944. mixing water, 938, 943, 947 /. neat and sand , 1136. needle, Vicat, 947 g (43). normal consistency, 943 (7), 9470 (43). permeability, 1088 (22), 1103, 1136, 1138, 1192, 1193 (78). for plastering, 1136. plasticity, 1136, 1137. properties, 947 h. proportion of in concrete, 1136. proportions, 1136. quantity required, 947 d. regrinding , 1137. retempering , 1137. richness, 1136. sal ammoniac in , 1136. salt in, 1107 (55), 1135, 1136. sand and neat, 1136. sand in, 946, 947 e, 947 j (65), 1135. See also under Sand. sea water in, 947 k (72). in sea water, 1136, 1138. setting, 940 (3), 942 (5), 943 (8), 947 /, 1090 (39), 1137- acceleration, 947 o (45). calcium chloride, effect of on ,9470 (45 c). expansion during , 1137. freezing, effect on , 1107 (45). gypsum, effect of on , 947 g (45 a). initial and final , 947 g. lime, effect of on , 947 e. rate of , 1137. retardation, 947 g (45). sand, effect of on , 947 g (45). silica, effect of on , 947 g (45). speed, 947 g. temperature as affected by , 947 g (46). sewage, effect of on , 1138. shrinkage of, 947 e (21), 947 h (56), 1137. slag cement, 947 / (38). soundness, 937, 938, 940 (3), 942 (6), 945 (16), 947 e (13), 947 h (53), 1136, 1137. lime, effect of on , 947 e (13). strength, 940 (3), 941 (4), 945 (15), 947 / (34), 947 h (52), 947 i, 947 j, 1136. age, effect of on , 947 i (64). compressive , 947 j (66). consistency, effect of on , 947 / (34). sand, effect of on , 947 j (65). shearing , 947 / (66). sulphuric acid in , 1135, 1136. tests, 937, 940, 942, 947 i (61). Vicat needle, 947 g (43). INDEX. Mortar Reinforced. Mortar continued, in water, 947 fc, 1136. water, mixing, 938, 943, 947 /, 1136. salt in, 1136. Mushroom system, 1134 (51). N. Natural cement. See under Cement. mix, 1087. Needle, Vicat , 947 g (43). Normal consistency, 943 (7), 947 g (43). o. Oil, effect of on concrete, 1108 (71), 1138. P. Painting, on concrete, 1103 (138), 1137. Paving, concrete sidewalks, 1201. Permeability. See under Concrete. Piles, concrete in , 1101 (124). Placing. See Concrete, placing. Plaster of Paris, 947 a (45 a), 947 h (55), 1135. See also Gypsum, effect of on metals, 1136. Plastering, mortar for , 1136. Plums (cvclopoan concrete), 1085, 1090(40), 1187 (15). Pointing, 947 j (70). Portland cement. See under Ce- ment. Pozzuolano, 930 (4), 932. Preservation of metals, 1136. Priddle internal-bond bar, 1131 (28). Principal stresses, 494 c, 494 g. Protection of metals, 1136. Puzzolano, 930 (4), 932. O. Quartering of sand, gravel etc, 946 (4). Quartz, as aggregate, 1137. weight, 947 o (19). Quick lime, 931 (7), 947 e (12). R. Ramming, 1100, 1137, 1189, 1190. cost of, 1210 (47,48). Rankine column formula, 1113 (10). Ransome bar, 1130 (21). Rehydration, 1108 (64). Reinforced concrete, 1110, 1139. See also under the structure in question, and name of type of reinforcement in question. See also Reinforcement. Reinforced concrete continued. adhesion, 1106 (37), 1111, 1126, 1128 (6), 1129 (9, 15, 16), 1139, 1196 (113, etc), -unit, 1126. aggregate for , 1110 (7). See also under Aggregate. anchor plates, 1129. bars. See Reinforcement, bars. beams. See Beams, reinforced concrete . clearance, 1196. coefficient, expansion , 1110 (9), 1138. columns, 1112, 1134, 1197. See also Columns, reinforced con- crete . conductivity, thermal , 1138, 1139. continuous beams, 1126, 1127, 1200. contraction, 1110. cost, 1210 (57-8). elastic modulus, 1110, 1195 (106). ratio, n, of, 1111 (14), 1195 (107), 1198 (153). electrolysis, 1108 (68), 1138, 1139. elongation, 1111 (16). expansion, 1110, 1138. .experiments, 1139. fire, effect of on , 1108 (62, 63, 65), 1138, 1139. in fireproof work, 1196 (120). forms, 1095, etc. See also Forms. friction, 1111 (18), 1139. floors, 1096 (67), 1098 (93), 1198. forms for, 1098 (93). initial stresses in, 1199 (159). methods of reinforcement, 1127. moments in, 1116 (7), 1117, 1118 (14, 17), 1121, 1122, 1123. permit, 1196. pillars. See Columns, reinforced concrete 1 . proportions, 1087 (13). reinforcement. See Reinforce- ment. See also name of type in question. shear, 1123, 1139. shearing stress, permissible, 1199 (161). shrinkage stress, 1199 (159). slabs, 1122, 1123, 1128 (5), 1199 (167), 1200, 1201. steel in, 1110 (5, 6), 1139. corrosion, 1110 (5), 1139. stirrups, 1124, 1128 (3), 1139, 1199 (162). strength, 1110-1123. stresses in, 1116 (8), 1117, 1118 (13,15,16), 1121, 1122 (21- 23), 1123 (32), 1125, 1127 (66), 1139, 1198, 1199. stretch, 1111 (16). tests, 1200. thermal conductivity, 1138, 1139. thermal stresses in , 1199 (159). unit adhesion, 1126. INDEX. Reinforcement Sand. Reinforcement, 1127, etc, 1139, 1194. See also name of type in question. adhesion, 1106 (37), 1111, 1126, 1128 (6), 1129 (9, 15, 16), 1139, 1196 (113, etc), bars, 1110, 1128-1131, 1139, 1194. corrugated , 1131 (24). cup, 1131 (25). deformed, 1110 (6), 1129 (15, 16), 1139, 1194. diamond, 1131 (26). lug, 1131 (22). plain, 1129 (10), 1139. supports for , 1131. trussed, 1133. clearance, 1196. in columns, 1112, 1134, 1197 (130, etc). conductivity, thermal , 1139. corrosion of , 1139. cost, 1207 (11). disturbance of, 1139. double, 1127, 1199 (165-6). electrolysis, 1139. expanded metal, 1132 (37). friction, 1111 (18), 1139. lapping, 1196 (116). lath, rib, 1133. length, 1196 (116). metal, expanded, 1132 (37). metal, rib, 1132 (41). methods of, 1110, 1127, 1139, 1194, 1199. mushroom system, 1134 (51). percentage of, 1139, 1207 (12). placing, cost, 1209 (45). proportions, 1139, 1207 (12). protection, 1196 (117). rib lath, 1133. rib metal, 1132 (41). rods, supports for , 1131. shapes, structural , 1133. shear, 1124, 1126 (55-57), 1128 (3), 1139. steel for, 1139, 1195 (100, etc), stirrups, 1124, 1128 (3), 1139. spacing of , 1199 (162). strength of, 1139. max allowed, 1195. structural shapes, 1133. supports for , 1131. tension in top of beam, 1127, 1199 (165-S). thermal conductivity, 1139. trussed, 1128 (2), 1133. types of, 1110, 1127, 1139, 1194, 1199. web, 1132, 1199 (164). welded wire, 1132 (40). wire lath, 1132. Retaining walls, cost, 1210 (59). Rib lath, 1133. Rib metal, 1132 (41). Rod, rods, for reinforced concrete, 1110, 1128, etc, 1131, 1139, 1194. Roman cement, 931 (12). Rosendale cement, 931 (11). Safety factor. See the material or con- struction in question. Sal ammoniac, in mortar, 1136. Salt, in concrete, 1107 (55), 1108 (67, 70). in mortar, 1107 (55), 1135, 1136. in water for mortar, 1136. Sand, analysis, 946. in cement mortar, 947 e. character of , effect of , 1135. clay in, 1135, 1186 (6). test for, 947 c (32). coefficient, uniformity . 947, 1135. compacting, 1135. composition, 946. in concrete, 947 e. for concrete sidewalks, specfns, 1201 (2). cost, 1207 (8). vs crushed limestone, 1135. definition, 946 (1). density, 947 a, 1135. moisture, effect of , on , 947 b. dirt in, 947 c, 1186 (6). strength of mortar, 947 e (23), 1135. effective size, 947. fineness, 947 e (18), 1135. shrinkage of mortar, 947 e (21), 947/i (58). foreign matter in , 947 e (23), 1135, 1186 (6). friction of , 1135. fusing point, 1135. grading of , 1135. grains, shape of, 947 b, 1135, size, 946, 947 6, 1186 (6). granulometric analysis, 946. impurities in , 947 e (23), 1135, 1186 (6). vs limestone, crushed , 1135. loam in, 1135, 1186 (6). test for, 947 c (32). mechanical analysis, 946. mica in, 1135, 1186 (6). moisture in, 947 6, 1135, 1186 (6). in mortar, 946, 947 e, 1135. See also Mortar, properties, 946, 947 c. See also Property in question, under arid. proportion of , in mortar, 947 d (4). INDEX. Sand Tangential. Sand continued. quantities required in mortar, 947 d (4). quartering, 946 (4). . vs screenings, 947 e (24), 947 / (27), 1135, 1186 (7). shape of grain, 947 b, 1135. sharpness, 947 e (22), 947 c, 1186 (5). silt in, 947 c (32). size, effective , 947. size of grain, 946, 947 b, 1186 (6). specific gravity, 947 a (19). specifications, 1186. standard, 944 (9). -stone as aggregate, 1137. storage, 1186 (6). strength of mortar, 947 j (65). uniformity coefficient, 947, 1135. voids in , 947 a, 1135. washing, 947 c (34). weight, 947 a (19), 947 e. Screening, Screenings, 946 (3), 1208 gravel, 947 / (26), 946 (3), 1137. vs sand, 947 e (24), 947 / (27), 1135, 1186 (7). stone ,947 / (27), 1137. Sea water effect on concrete, 947 k, 1108 (67), 1136, 1138. in mortar, 947 k (72). Set, 456, 459. permanent , 456, 459. Setting. See Mortar, and Concrete. Sewage, effect on concrete, 1138. Shale, as aggregate, 1137. Shapes, structural , for reinfmt, 1133. Shear, in concrete beams, 1123. horizontal , 494 c, 494 e. in reinforced concrete beams, 1 123. reinfmt, 1124, 1126 (55-7), 1128 - (3). unit, 494 e. in reinfd cone beams, 1125. vertical , 494 c, 494 e. Shearing, stress, 454. Sidewalks, concrete , 1201. Silica cement, 932 (25). Size, effective , 947. Slabs, reinfd cone, 1122, 1123, 1128, 1199 (167), 1200, 1201. Slacking, 931. Slag cement, 930, 932. Slaking, 931. Soap and alum process, 1105 (20), 1137. Soundness, 937, 938, 940 (3), 942 (6), 945, 947 e (13), 947 h, 1136, 1137. Specific gravity, test, LeChatelier method, 942. Specifications for cement, 937, 940, 942. for concrete, 1184, 1186. blocks, 1204. sidewalks, 1201. Steam, effect on concrete, 1138. Steel, bending tests, 1195 (109). in concrete. See Reinforced con- crete, steel in , and Rein- forcement. elastic modulus, 1110 (11). in reinforced concrete. See Re- inforced concrete, steel in , and Reinforcement, steel . structural , elastic modulus, 460. Stirrups, 1124, 1128 (3), 1139. spacing, 1199 (162). supporting reinforcement, 1131 (31). Stone, stones, artificial, 1193. broken, 1137. voids, in, 1085, 1088. cost, 1207 (10). large , in concrete, 1085, 1090 (40), 1187 (15). screenings, 947 / (27), 1137. work, mortar required for , 947 d. Strength, 454. See also under Con- crete, Mortar, and Reinfd cone. Stress, Stresses, components, 454. compressive , 454. diagonal , in beams, 494 a, 494 e, 1125. maximum , in beams, 494 a, 494 e. principal, 494 r, 494 g. in reinforced concrete beams, 1115-1123, 1125, 1127 (66). shearing , 454. tensile , 454. torsional , 454. transverse , 455. ultimate , 456. unit , 456, 458. actual and nominal , 456. Stretch, 454, 455, 459. unit , 458. Structural shapes, for reinfmt, 1133. Suddenly applied loads, 461. Sulphuric acid, in mortar, 1135, 1136. Sulphate, lime, 947 g (45 a), 947 h (55), 1135. Sunshine, effect on concrete, 1138. Sylvester process, 1105 (20), 1137. T. T-beams, 1122, 1199 (171). Tamping, concrete, 1100, 1137, 1189, 1190, 1210 (47, 48). Tangential stress, 454. INDEX. Tensile Zinc. Tensile strength, 454. stress, 454. Tension, 454. Test, Tests, of cement, 936, 937, 940, 942, 947 i (61, 62), 1186 (2). of concrete, 1109, 1200. Testing machine for cements, 938. Thacher bar, 1131 (23). Thermal conductivity, 1138, 1139. Tie-rods, in forms, 1189 (36). Torsion, 454. Tremie, 1100 (116). True elastic limit, 459. Truss reinforcement, 1128 (2), 1133. Trussed bar, 1133. reinforcement, 1128 (2), 1133. Turner, C. A. P., mushroom system, 1134 (51). U. Ultimate stress, 456. Uniformity coefficient, 947, 1135. Unit, Units, adhesion, 1126. frame, 1133. shear, 494 e. in reinfd cone beams, 1125. V. Vertical shear, 494 c, 494 e. Vicat needle, 947 g (43). Voids, in broken stone, 1088. in concrete, 1088, 1137. in sand, 947 a, 1135. Volume, constancy of (soundness), 937, 938, 940 (3), 942 (6), 945 (16), 947 e (13), 947 h, 1136, 1137. W. Wall, Walls, concrete, forms, 1096 (68). retaining , concrete , cost, 1210 (59). Washing concrete, cost, 1208 (18), 1210 (51). Water, sea , effect on concrete, 947 k, 1108 (67), 1136, 1138. mortar, 947 k (72). Web reinforcement, 1132, 1199 (164). Welded wire, 1132 (40). White efflorescence on walls, 947 j. " Portland cement, 933 (29). Wire, lath, 1132. welded, 1132 (40). Y. Yield point, 455, 460. Z. Zinc, effect of cement mortar on , 1136. THE END. YB 51896