UC-NRLF HE ASSOCIATED 1900) p fl.la.nd THE EVERYDAY USES of PORTLAND CEMENT THE EVERYDAY USES of PORTLAND CEMENT Presented by THE ASSOCIATED PORTLAND CEMENT MANUFACTURERS (1900) LTD. Portland House Lloyds Avenue London E.G. THIRD EDITION, 191.3, Published by THE ASSOCIATED PORTLAND CEMENT MANUFACTURERS (1900), LIMITED, AT PORTLAND HOUSE, LLOYDS AVENUE, LONDON, E.G. PRICE: Paper Covers, 1/6 net; Full Botad Cloth Covers, 2/6 net, Copyright. ALL RIGHTS RESERVED. First Edition, January, 1909. Second Edition, Ja-nttary, 1912. Third Edition, March, 1913 PREFACE. Tin; use of Portland Cement has been extended in the last few years to a wide range of different purposes, and there are a multitude of examples of its everyday use in ways that were never contemplated a few years ago. This has been brought about chiefly by the cheapening and improvement of the manufacture, though, of course, time has also had some influence in making better known the good qualities of the product and its possibilities. In a treatise on Portland Cement, the subject could be dealt with from several aspects. The aim of this book is to furnish what may be called the lay-user of Portland Cement i.e., the farmer, estate owner, manufacturer, and the householder with some account of the many uses to which the material can be put with advantage, as well as to provide the members of the technical professions and trades with a comprehensive summary of certain aspects of the subject, upon which, hitherto, there has not been much reliable information available. It is our purpose to point out the wide possibilities which exist for the useful employment of Portland Cement. Examples are given to show what use is being made of the material, with the hope of affording instruction and advice to those unfamiliar with Portland Cement and its applica- tion, and to serve as a reminder and reference book to those who are more conversant with both. As this work is intended for the lay-user as well as the expert, we have endeavoured to convey the information as simply as possible. Portland Cement will be assured of still wider adoption in substitution for, or in conjunction with, other materials when it becomes recognised that good work depends as much upon the user as upon the cement. Care, practice and supervision are essential, and this work is intended 272837 vi. PREFACE. to assist users in avoiding mishaps from causes which have nothing to do with the quality of the cement, as well as to serve as a guide to the many purposes for which Portland Cement is suited. The favour with which the first edition of this book was received led to the preparation of a second edition much earlier than was anticipated ; and the success of this issue has been even greater than that of the earlier one. The third edition is now presented and it is hoped will meet with a similar reception. The ever increasing popu- larity of Portland Cement, and the application of it to fresh uses, called for the addition of two hundred pages in the second edition descriptive of and illustrating these develop- ments ; thus, in two years we found it necessary to more than double the size of the book. The light of experience has led to the revision of some chapters in the present edition and to the incorporation of new matter in others. This is notably the case in con- nection with reinforced concrete, the use of which has steadily continued and grown. The inclusion in this edition of a glossary of technical terms and an index will add, we trust, to the usefulness of the book. Our thanks are due to correspondents, not merely for complimentary letters recording the help that they have received from the work, but also for suggestions which have been found valuable and have, as far as possible, been utilised in the present edition. For such suggestions we are always grateful. It should be borne in mind that the price of Portland Cement, as of other materials, fluctuates from time to time, and that the cost of concrete and all other work executed with cement must of course vary in proportion. The calculations or statements of cost given in various places in this book cannot therefore be regarded as applicable under all conditions, but as the cost of the cement itself forms but a minor pnrt of the total expense the variation in actual, practice will probably not be serious. As we anticipate that this book will see the issue of further editions, we shall welcome any expressions of opinion, or any fresh data that may enable us to improve PREFACE. vii. it ; and we would thank readers in any event to inform us, by use of the form to be found at the end of the booklet, or by letter, whether any fresh editions or other pamphlets referring- to new uses or changes in practice that we may be issuing from time to time are to be forwarded to them. In conclusion, we wish to express our thanks to " Concrete and Constructional Engineering," of 8, Waterloo Place, S.W., for a good deal of most useful information included in the following pages and for the loan of numerous illustrations. THE ASSOCIATED PORTLAND CEMENT MANUFACTURERS (1900), LIMITED. Portland House, Lloyds Avenue, London, E.C. March, INDEX. Page Acids, action of, on concrete ... ... 254 Adhesive strength of concrete to steel 340 Advertisement boards ... ... ... 324 Aeration of cement ... ... ... n 13 Aerial transporters ... ... ... 321 Aggregate ^ 14 Aluminium, weight of ... ... ... 344 American ash, weight of ... ... 344 Anchors ... ... ... ... ... 326 Annual output of Portland Cement ... 3 A.P.C.M. (1900), Ltd. Some notes concerning the ... ... 351 List of companies comprising the ... 351 Brands owned by the ... ... 360 Aquarium ... ... ... ... 274 Aqueducts ... ... ... ... 182 Arks 256 Artificial stone ... ... ... ... 109 Asphalt Rock, weight of ... ... 344 Ballast as a coarse material ... ... 16 ,, burnt, as an aggregate ... 19 ,, weight of ... ... 344 Barges ... 326, 327 Barns 218, 238 Barrows ... ... ... 7 Bearing power of soils ... ... ... 343 Beater, wooden, use of ... ... ... 108 Benches, garden ... ... ... ... 286 Benching 243 Benders, use of ... 108 Bitumen, weight of ... 344 Blackboards 335 Blocks 109 119 ,, cost of making ... ... ... 116, 117 ,, machines for making ... ... 114 119 ,, waterproofing ... 116 Boards, 'name and notice ... ... 320 Boats ... ... ... ... ... 326 Boiler ... ... ... 237 Boiler ashes as a coarse material ... 14 15 Illustration Fig. No. 3 2 5. 326 266 328, 331, 332, 333 183, 213, 214 27 82 267, 268 223 8690 9294 x. INDEX. Illustration Page Fig. No. Boundary stones ... ... ... 267 Brass, cast, weight of 344 Breeze ... ... ... 14 Brick, broken, as a coarse material 15, 18 ,, weight of .... 344 Bricks 119121 95, 96 Brickwork, weight of 344 ,, cement mortar for ... ... 341 Bridges 290297 284289 Buckets 72 3i Buildings, various 196211 153 159, 161, 163171, 173175 Bungalows J 94 *55 J 57 Bunkers 249, 314 229, 315, 316 Byres, cattle 226 J 95 Cabinet 333 335 Caissons 156-158,30", 113,114,296 301 297 Canals 2 9 8 Canal basin ... , 2 9 294 Carts 7o 28-29 Cathedrals 93, 204 Cellars - . -". 2 ^ 2 ' 2 ^ 224 ' 225 Cement, painting Cement, weight of ... 344 Centering (see forms) Cesspools I8 ' > 8 < '*' Chalk, weight of Channel blocks for roads ! 7 6 Chemical composition of Portland Cement ' Chicken-houses 237 Chimney caps ... ... ... 197 162 Chimney piece Jl Chimney shafts 2 ? 2&2 ' 28 3 Churches 2 4 l68 ~ I 7 Cisterns 2 49~ 2 54 230,231,237 Clay, bearing power of ,, weight of ... 344 Clinker as a coarse material J 4 I 5> l ~ 2 Closet, moist 3 2 7 334 Coal bins - 2 49 229 Coal, weight of 344 Coaling station 39 37 Coarse material ,, breaking the 20 5, 6 ,, fire resistance of various -4 26 INDEX. Page Coarse material, grading of various ... 28 ,, ,, quantities required for dense concrete ... 37 ,, ,, selecting a ... ... 28 ,, ,, suitable and unsuit- able ... ... 14 i ^ Coke breeze as a coarse material ... 14 15, i Coke, loose, weight of ... ... ... 344 Colouring concrete ... ... ... in 112 ,, ,, bricks ... 120 ,, ,, tiles ... 123 ,, effect of, on the setting time of Portland Cement 112 ,, Portland Cement plaster ... 85 Compactness, to test sand for ... ... 36 Concrete Age, The ... ... ... 4 Concrete ... ... ... ... ... 27 56 ,, adhesive strength of, to steel 340 ,, average weight of, with various coarse materials... 337 ,, approximate percentage of strength of 338 ,, resistance of, to crushing ... 338, 339 ,, cost of, diagram for ascer- taining the ... 55 ,, cracking and crazing of ... 49 52 ,, cracks in, prevention of ... 78 ,, essentials of good ... ... 40 ,, importance of care in pro- portioning ... ... ... 38 ,, insoluble substances for filling the pores in ... ... 82 ,, material for i cubic yard of 54 ,, method of proportioning material for ... ... ... 31 ,, mixing of ... ... ... 40 44 ,, placing in water ... ... 70 ,, putting in place 69 70 ,, quantity obtained from various proportions ... 39 ,, reinforced, average weight of 337 ,, some uncommon uses of ... 320 324 ,, special tools required ... 100 ,, surface finish of ... ... 72 78 testing 4447 ,, to make good ... ... ... 27 28 ,, users, memoranda for ... 337 346 ,, water for mixing ... ... 39 we 'gnt of 337, 344 XI. Illustration Fig. No. 3344 46-89 3344 xii. INDEX. Illustration Page Fig. No. Concrete, waterproofing ... ... 78 84 ,, \vet v.. dry mixtures ... 110 111 ,, work, estimating cost of ... 53 56 Condensers ... ... ... ... 290 Conduits ... ... ... ... ... 182 190 147 Conservatory, concrete in 196, 274 265 Contraction of Portland Cement ... 9, 51 2 Cooling tower 290 314 Corrosion, protection against ... ... 4, 5> I 5 I l & 2 Cottages 194. 217 158, 161, 183 Cow-houses ... ... ... ... 226 194, 195, i ( ; 199 Cracks in concrete ... ..>.' ... 49 5 2 > 7 Crazing of concrete ... ... ... 49 Crazing of tiles, prevention of ... 214 Crushing resistance ... ... ... 338, 339 Culverts 190, 191, 292 149, 152 Dairies ... 240 216 Dams ... 298 295 Darby, use of 86 49 Dasher (rough cast), use of ... ... 88 50 Depeter ... 89 Diagram i, ... ... 55 (For ascertaining the cost of concrete) Diagram 2, facing 134 (For calculating- reinforced concrete slabs) Diagram 3, ... ... '4 1 (For calculating reinforced concrete beams) Difference between genuine Portland Cement and " natural " cement ... 5 7 Docks 298 ,, floating 327 327 Dog kennels 238 Drain pipes 124 08 Drains, joints in 179, 180 Dust and dirt, effect of, upon concrete 29 " Dusting " concrete surfaces 174 " Dusting " tile surfaces 123 Dykes 33 35. 3<> Earth, weight of ... 344 Efflorescence on concrete 96 98 Electric light standards 320 320, 322 Kim. dry, weight of ... ... ... 344 Engine bed 158 INDEX. xii Illustration Page Fig. No. Essentials of good concrete ... ... 40 Estimating cost of concrete work ... 53 56 Expansion of Portland Cement ... 9, if), 50, 51 3 Expansion of Sle-el and Co Hivtc ... 290 Farm, concrete on the ... 216 224 Farmyard pavements ... ... ... 224 226 Fences and fence posts ... 232, 262 270 ,, ,, COSt of ... 267, 2 TO " Ferrocrete " Portland Cement ... 24, 262 Ferry tower ... ... ... ... 205 174 Fire resistance of various coarse materials ... ... ... ... 24 26 Fire stations ... ... ... ... 205 173 Fives courts ... ... ... ... 214 180 Flats, steel, widths, etc., obtainable ... 346 Flint, weight of ... ... 344 Float, the use of 86, 88 48 Floors, feeding 224, 225 193, 194 ,, interior ... ... ... ... 60, 168, 169 21, 22 ,, materials required ... ... 342 ,, superimposed loads on ... 343 Flower boxes 286 278 Forms or centering, construction of... 58 ^9 16 2^ ,, boarding and battens for ... 57 r,8 ,, circular 68 24, 25 ,, for girders, floors and posts... 60,167 2123, ! 2 5 ,, kind of timber required for... 64 ,, time to leave in place ... 66 68 ,, for walls ... ... ... 59 60 16 20 ,, weak ... ... 66 Formulae for calculating section of circular form ... ... ... ... 69 26 Foundations 153159 108 110,113 191 1 15, 1 1 6 ' Fountains 285 271, 272 Forestry, employment of concrete in 286 290 280 282 Frame, impression, use of ... ... 103 66 Frames, garden ... 222,243 221,222 Freezing of concrete, prevention of... 47 49 Frost, effect of, upon concrete ... 47 49, 68 Fruit houses ... ... ... ... 242 Furniture 327 334 336 Gable, stuccoed ... ... 223 192 Gantries 314 31 -, 316 Garage, motor ... ... .;. ... 20^ 171 XIV. INDEX. Page Garden benches ... ... ... ... 286 ,, frames 222, 243 ,, roller 274 ,, seats ... ... ... ... 286 ,, steps ... 271274 ,, uses of concrete in the ... 271 286 vases ... ... 286 Gasholders ... 256 Glass, weight of 344 Glossary 347, 348 Grain, weight of ... ... ... 344 Granite as a coarse material ... 17 18 ,, Scotch, weight of 344 Gravel 16, 17 Gravel, weight of 344 Gravel soil, bearing power of... ... 343 Greenhouses 223, 242 Grout, cement ... ... 029:5 Grouting granite setts ... ... ... 179 Grouting machine, use of ... ... 94, 9.- Groynes 302308 Gutters ... ... ... 176 Hair cracks in concrete ^9 52 Hammer, lath, use of 87 ,, bush, use of ... ... 105 Harbours 298 Harling 88 Hawk, use of 86, 88 Hemlock, dry, weight of 344 Hitching posts ... ... ... ... 270, 271 Hoops and bands, sizes, etc., obtain- able 345 Houses 191 205 Ice, weight of ... 344 Initial setting and hardening of Port- land Cement ... ... n Introduction i 2 Inventor of Portland Cement ... ... 3 Iron and steel, protection of, against corrosion 4 5, 151, 182 Iron-oxide, effect of, on strength of Portland cement ... ... ... 23 Iron, weight of 344 Iron wires, sizes, weights, etc., of ... 346 Illustration Fig. No. 267, 268 221, 222 262 268 260, 26l 260 264, 267 272 273, 274, 275, 2~7, 279 241, 242 219, 220 45 45 46 74 292 47 250 153 ' INDEX. xv. Illustration Page Fig. No. Jetties 157, 297 290 Jointer, use of ... ... ... ... 100 52, 59 Joints in drains ... ... ... ... 179, 180 Keene's cement, effect of, upon Port- land cement ... 18 Kerbs 175 135, 136, 137 Landscape gardening ... 274 286 Larry, use of ... ... 105 79 Laths, widths, etc., of ... ... 87 Lath hammer, use of ... ... ... 87 46 Laundries ... ... ... ... 218, 240, 241 218 Lavatories, underground ... ... 208 179 Lead, weight of... ... ... ... 344 Le Chatelier test ... ... ... 10 4 Lifeboat slipway ... ... ... 298 293 Lighthouses ... ... ... ... 302 298, 299 Lime putty ... ... 92 Lime, slaked, weight of ... ... 344 Limestones, weight of ... ... ... 344 Lockers ... ... ... 241 217 Macadam ... ... ... ... 178 Machines ... 114 124 45,90,92,93, 94. 95. 9 6 > 97, 98 Mains ... 182 190 142 Manholes ..." 180, 181, 182 138, 139 Manila Cathedral ... ... ... 204 167 Marble, weight of 344 Marl 6 Masonry, weight of ... 344 Masts 320 321 Memoranda for concrete users ... 337 34^ Mexico City waterworks J 9 I 5 I 5 I Mines, concrete in ... 3 X 4 3 J 3 3 J 8 Mixers, concrete... ... 40 44 10 15 Mixture for fixing glass, tiles and other facings 214 Moist closet 327 334 Mortar, cement 9* 9 2 ,, hardened, weight of 344 Mortars with ordinary sand ... ... 343 Motor house 205 i? 1 ,, pits 205 172 ,, tracks 17, 296 287 Moulded concrete 109 124 91 98 Moulds for artificial stonework ... 110 xvi. INDEX. Illustration Page Fig. No. Moulds, to prevent concrete sticking to 65, 265 Mud, weight of 344 Nails, double-headed ... 58 Name and notice boards ... ... 320 " Natural " cement ... 5 7 New concrete on old concrete surface 252 Oak and concrete posts, comparative cost of 270 Oak, dry, weight of 344 Oil, effect of, on concrete ... ... 254 Oil, effect of, when mixed with con- crete ... 82 Painting cement and concrete surfaces 98, 100 Park work, fancy ... ... ... 274 286 Partition slabs 121, 122 Passage ... ... ... ... ... 220 189 Paths 172175 132, 133, 134 Pavements 172 175 Paving, interior 168, 169 ,, farmyard 224 226 Pebbles as a coarse material 29 Pebble dashing 88 Pens, cattle 222, 232, 237 191, 203 Pergolas 285 264, 272 Peterborough cathedral 93 Petrol, effect of, on concrete ... ... 254 Petroleum, weight of 344 Piers 167, 168, 290, 291 297 Piggeries 218, 226 186, 196, 200 Piles ... ... ... 153, 155 in, 112 Pine, weight of ... 344 Pipes 124, 147, 182 98, 142, 144, 190 145 Plastering, Portland Cement 8488 ,, quantity of cement and sand required to plaster a given area ... ... 341 Plaster of Paris (cast), weight of ... 344 Platforms, railway 308 308 Pontoons 326, 327 329 Portland Cement, annual output of ... 3 ,, ,, aeration of ... ... n 13 ,, ,, as a protection for iron and steel against corrosion... 4 5, 151, 182 INDEX. XVll. Portland Cement, chemical composi- tion of ,, ,, derivation of name ,, ,, difference between genuine "artificial" and " natural cement ,, ,, initial setting and Page 6 3 Illustration Fig. No. hardening ot ,, ,, inventor of ... 1 1 3 ,, ,, its lasting quality... 4 ,, ,, medium setting 8 ,, ,, quality of modern... 5 ,, ,, quantity required for various purposes... 34. 34 1 ,, ,, quick setting 8 1 , 1 09 ,, ,, setting of 96 ,, ,, slow setting 8,9 ,, ,, specific gravity of... 54. 337 ,, ,, storage of 3 ,, ,, test for soundness... 9 ,, ,, testing of 8 10 i 4 ,, ,, weight of 337 Posts clothes ... ... ... ... 270 2^8 ,, fence 232, 262 270 246 25 2 57 ,, forms for ... ... ... ... 60, 167 12^ hitching 271 2 ^9 signal 72O Potato, specific gravity of a ... vi 47 Presbytery 2 O I I 6 ^ Pumice as a coarse material ... :-5. T 9> I2 i Pumice stone, weight of 344 Puzzuolana ... ... ... I Q Quartz, weight of J 344 Quay walls T ~*~ T " ^ Quick lime, weight of ... J O/ i 344 Quick setting Portland Cement 81, 109 Racquet courts ... ... 214 180 Railway, concrete on the 308 314 307 312 Railway sleepers ... 314 311,312 Rake, use of ... ... 105 78 Rammers and ramming ... ... 108 80, 81 Red lead, weight of ... ... ... 344 Reinforced concrete ... ... ... 4, 125 152 ,, average weight of 337 xviii. INDEX. Illustration Page Fig. No. Reinforced concrete, books recom- mended ... ... 147 ,, ,, calculations ... 12(1 129 ,, ,, construction, sim- ple types of form for 6 1 21, 22 ,, ,, the fundamental principle ... 125, 126 ,, ,, sizes of steel bars 345 >, weight of ... 337 Reservoirs 253, 261 232, 243, 244 Rick stands 240 215 Rifle range ... ... ... 324 324 Roads, concrete for ... ... ... 175 179 Rock soil, bearing power of ... ... 343 Rockeries 274 266 Roller, garden 274 262 Roofs 108, 208 179 Roofs, superimposed loads on ... ... 343 Root cellars 242 224, 225 Rough cast 88, 89 50, 65 Round-house 309 310 Safe 216 182 Salt water, action of, in setting of Portland Cement 23, 24, 39 Salt and water, specific gravity of ... 47 Salt, weight of 344 Sand, suitable and unsuitable ... 22 24, 30, 31 ,, solids and voids in 34 l ,, to test for compactness ... 36 ,, washer ... 21 7 8 ,, weight of 344 ,, and coarse material ... ... H 2 ^> 3 1 ,, proportions usually adopted for concrete 3^ ,, Sifting 22 9 ,, To determine proportions ... 31 ,, Washing 21 7, 8 School-house 201 166 Scow 327 330 Screeds 86 Sea water, specific gravity of 47 Setts, granite, grouting of 179 Setting of Portland Cement 96 Setting (initial) and hardening of Portland Cement n INDEX. XIX. Illustration Page Fig. No. Sewers ... ... ... ... ... 182 190 M3 J 45> 14^ 148 Sgraffito ...< 89, 90 Shafts, chimney 290 282, 283 Shale, weight of 344 Sheds 219, 222, 238, 188, 190 3 08 Sheep dipping trough 222 191 Shipbuilding, uses of cement in 324326 Shingle 16 Shore protection 3- 3S 300 306 Shovel, use of 105 77 Shower baths 241 217 Sifters ... " 22 9 Silos 246, 248 226, 227, 228 Signal box 309 309 ,, posts 320 Skating rink 2OI 164 Skips 72 31, 32 Slabs, concrete ... ... ... '.'. I I I ,, pickle for hardening ... *.. III Slabs, partition ... ... ... '-.*.. 121, 122 Slag cement 7 Slag as a coarse material I 5 , 19, 20 Slates 122 Slate, weight of 344 Slip 256 Sleepers, railway 3M 311, 312 Steel bars, sizes, etc., of 345 Snow, weight of 344 Soils, bearing power of 343 Solids and voids in various coarse materials ... ... ... ... 341 Soundness of Portland Cement, to ascertain the 9 Spade, Ross concrete ... ... " ... 103 "2 Spar, calcareous, weight of ... 344 Specific gravity of a potato ... ... 47 ,, ,, of Portland Cement... 54. 337 ,, ,, of salt and water 47 ,, ,, of sea water 47 Speltzer, weight of 344 Spruce, dry, weight of 344 Stables 218 185 Stairs 169 172 126 131 Stalls 226 197, 199, 201 Stands, football and racecourse 208 202 1, INDEX. Standards, railway ... ,, electric light Stations, coaling and sand Statue, monumental Steel and iron, protection of, against corrosion ,, strength of ,, weight of ... Steps, garden, construction of... ,, interior, construction of Stone, artificial ... ... ,, breakers ,, broken, as a coarse material... ,, ,, solids and voids in ... ,, screenings, solids and voids in ,, weight of ... ... Storage of Portland Cement ... Strength of concrete at different ages Strong-rooms Struts for floor forms, safe strength of Stucco, Portland Cement Sugar, effect of, on concrete Sulphur in bricks ;.. ... Sundial ... ... Surface finish of concrete Surfaccr, pavement, use of Surfaces, coated ... ... ... Swimming baths ... ... ... ,, pond Page 320 320 309 335 45, 151 34" 344 2? 1 . 274 169 172 109 20 7 34 1 34i 344 13 338 216 66 35, 223 255 120 274 7 278 100 9 1 261 261 lS2 Illustration Fig. No. 320, 322 181 192 263 3344 60 2 45 )S MS 286, -m 276, T*6 eight of 344 / W > v?x) use of 105 73 irons, use of ... ... ioS 8385 ... 219, 249, 262 234, 238, 240 of, en Table for designing concrete beams and slabs Tables Tallo Tamp Tampi Tanks Tanning solutions, action concrete ... ... ... ... Tar, weight of ... ...... ... Telegraph poles ............ Temperature at which the setting of Portland Cement is arrested ... Tennis courts ... ......... Terraces, garden, construction of ... Testing of Portland Cement ... ... Theatres ............ 254 344 3 20 49 214 271 274 8 10 208 3 J 9> 3 22 176 INDEX. Tiles, colouring ... Page 123 glass, etc., mixture for fixing 214 XX!. Illustration Fig. No. ,, roofing ... ... ... ... 122, 124 weight of .... ... 344 Timber most suitable for forms ... 64 ,, weight of ... ... ... 344 Tombstones ... ... ... ... 335 Tools, special ... ... ... ... 100 ,, surfacing, use of ... ... 105 ,, twisting, use of ... ... 108 86 90 Torpedo station ... ... ... ... 300 -96, 297 Transporters, aerial ... ... ... 321 323 Trass, as a coarse material ... ... 19 Trowelling ... ... ... ... 87, 174 Tree dentistry ... ... ... 286 290 280 282 Trough, bottle washing ... ... 2.|o 216 ,, sheep dipping ... ... ... 222 191 ,, watering and feeding ... 232 237 194,198,204 210 Truck, tipping ... ... ... ... 70 30 Tuff 19 Urinal stalls ... ... ... ... 212, 214 Vases, flower ... 286 273, 274, 277 2/9 Vats 255 239 Vaults, burial ... ... ... ... 335 Village hall ... 196 163 Villas 194 153 Voids and solids in various coarse materials ... ... ... ... 34,341 Walls 153, 159, 167, 117 124, 184 218 ,, concrete, to prevent damp rising 79 ,, forms for ... ... 59, 60 16 20 Water for mixing concrete ... ... 39 ,, placing concrete in ... ... 7 tanks 219, 249, 262 234, 238 towers 219, 253 187, 233, 235, 236 weight of 337. 344 Watering troughs ... ... ... 232 237 194, 198. 204 210 Waterproofing concrete... ... ... 78 84 ,, ,, blocks ... 116 ,, compounds ... ... So 83 xxii. INDEX. t {lustration Page Fig. No. Weights of various substances ... 344 Wells 25 8, 26 i Well kerbs 258 Wheelbarrows, capacity of 338 Windmills, foundations for 158 11-, M 6 Wire (iron) sizes, weights, lengths and breaking strain of 346 Wood most suitable for various purposes 64 Zinc, weight of ... ... ... ... 344 INTRODUCTION. PERHAPS the most striking feature of the modern use of Portland Cement is the erection of buildings and all kinds of structures in reinforced concrete. And scarcely less notable is the way in which it has been satisfactorily applied in the construction of walls with hollow concrete blocks. The variety and magnitude of the applications of reinforced concrete are really surprising, as the following pages bear witness. The whole aspect of modern building and engineering construction has been changed by its advent. The design of reinforced concrete is a subject upon which, in the majority of cases, the advice and assistance of experts are required, but there are many simple ways in which the fundamental principle of strengthening con- crete by the embedding of steel can be utilised by anyone without professional knowledge. Concrete blocks are readily made by means of one or other of the several machines on the market, or, indeed, can be made in ordinary wooden moulds, and they have been found con- venient and economical for the erection of agricultural labourers' cottages, farm buildings, village halls, etc., as they can be manufactured on the site with materials obtained in the immediate neighbourhood of the work to be done. Portland Cement concrete, plain or reinforced, made in situ or brought to the site in the form of moulded blocks, slabs, posts, etc., has been used with excellent results for a great many purposes by agriculturists and stock-breeders, where formerly, for the sake of economy, it was customary to erect farm buildings of timber. It has now been recognised that not only can such buildings often be erected in concrete as cheaply, and sometimes at less cost, than in other materials, but that from the point of view of lasting quality, economy in upkeep, and cleanliness, it is infinitely superior. Modern sanitary investigation has led us to a better understanding of the vital importance of cleanliness in keeping stock and handling farm products. Badly ventilated, badly lighted and unclean stables, byres C 2 INTRODUCTION. and styes, are now known to foster disease, and to result in loss in the rearing of live stock. Further, timber is subject to fire, whereas suitably prepared concrete is one of the most fire-resisting materials known. The depopulation in rural districts which has been going on for many years past, and about which there has been much agitation, renders it of increasing importance to carry out the work of a farm with the least expenditure of labour, and from this aspect concrete offers a solution to many difficulties. A concrete building is not subject to deterioration ; it is fire-resisting, clean, free from vermin, and will withstand the severest w r eather and the roughest usage. Needing no repair, it seems, indeed, to get stronger with age, and almost requires dynamite to remove it. The first cost is the last cost. So much for the business aspect. From the sanitary point of view a concrete building can be washed down, scrubbed, disinfected, steamed or sterilised so as to destroy all germs, while it can be kept clean with the least expenditure of labour. Portland Cement concrete is therefore an attractive material from all standpoints. PORTLAND CEMENT. PORTLAND Cement is essentially a British invention. It was originally patented by Joseph Aspdin, a bricklayer, of Leeds, in 1824, though it has been stated that it was invented by him in 1811. It was first used, on any exten- sive scale, by Brunei in the construction of the Thames Tunnel in 1828, being supplied from Aspdin 's works at Wakefield. It took some time for the cement to make headway against prejudice, and for the professional and lay public to appreciate its advantages. The name " Portland Cement " was given to the material by its inventor because of its resemblance, when set hard, to the well-known building stone quarried at Portland on the south coast of Dorsetshire, and used for many important buildings, such as St. Paul's Cathedral and Somerset House. Portland Cement was first made on a truly commercial scale at Swanscombe, Northfleet, Faversham, and Cliffe, all in the County of Kent, at the works of " J. B. White & Brothers," " Robins & Co.," " Knight, Bevan & Sturge," 11 Hilton, Anderson & Co.," and " Francis & Co.," all of which firms were pioneers of the cement industry and have now been incorporated with others in " The Associated Portland Cement Manufacturers (1900), Limited." Portland Cement has therefore been used in this country and throughout the world for just upon ninety years, and the production has increased by leaps and bounds, especially in recent years. It is now manufactured in almost every country, and the amount of capital invested in the production of cement represents many millions of pounds sterling, while the world's annual output may be estimated at over 20,000,000 tons. 4 PORTLAND CEMENT. ITS LASTING QUALITY. Concrete made with hydraulic lime has been known for some hundreds of years. The Romans used lime concrete that has stood for centuries and is doubtless better to-day than when it was first made. Roman aqueducts, .baths and temples remain to show its enduring qualities. The Pantheon at Rome, built with a huge concrete dome, is one of the world's greatest buildings and is perfectly ser- viceable to-day, and the concrete domes and vaults of the Baths of Caracalla and Diocletian are among the chief sights of Rome. But concrete made with hydraulic lime, or special cements largely composed of lime, such as Roman cement, was nothing like so serviceable a material as Portland Cement concrete. We refer to it merely because it shows the remarkable resistance and life possessed by concrete. If lime concrete has stood unharmed throughout the ages, Portland Cement concrete, which is infinitely superior, must be imperishable. THE CONCRETE AGE. We have passed through what has been termed the steel age, and are now in the concrete age. Many of the greatest engineering works of modern times could never have been carried out without Portland Cement con- crete. It is now used in substitution for stone, brickwork, timber, steel- and iron-work. With steel and iron embedded in it, Portland Cement concrete produces the most fire-resisting buildings. This style of construction is called reinforced concrete. The name indicates the purpose for which the metal is em- bedded namely, to add its own special qualities to strengthen the concrete, and to enable it better to resist any destructive forces to which it may be subjected. Reinforced concrete has not only great strength but a considerable amount of ductility ; therefore, it can be safely subjected to higher stresses than plain concrete. It has been found to resist shock and remain uninjured by continual vibration. Portland Cement has the remarkable property of thoroughly protecting steel and iron from corrosion or PORTLAND CEMENT. 5 rusting. This is due to the chemical nature of the material and an intimate chemical action which need not here be demonstrated. That it provides a better means of pro- tecting steel and iron from rust than any other anti- corrosive, has been proved up to the hilt. Steel and iron embedded in concrete have been found uninjured under the most adverse conditions. We need refer to one instance only to prove this. Some reinforced concrete water pipes (if in. thick) were constructed in Grenoble twenty-two years ago. After fifteen years, two lengths of pipe were raised for inspection, and it was found that although the water had been flowing through them and they had been embedded in soil for all those years with only in. of Portland Cement concrete protecting the steel, the metal was as bright as on the day it had been put in. QUALITY OF MODERN PORTLAND CEMENT. Portland Cement was formerly manufactured by a somewhat rule of thumb method, but it is now in the hands of trained and experienced chemists who watch and check every stage of its manufacture. The good quality of modern Portland Cement from the best works is so well assured that the user has little cause for attributing mis- haps to the Cement, but should attribute a failure to some other cause. Provided the Portland Cement be obtained from makers of repute in this country, cases in which it will not make good work, if properly treated and used, are extremely rare. In the English Colonies and in most markets abroad the best English brands of Portland Cement are obtainable and should always be demanded. THE DIFFERENCE BETWEEN GENUINE PORTLAND CEMENT AND "NATURAL" CEMENT. Though much good Portland Cement is now manufac- tured abroad, very little of this comes into the United Kingdom. A large quantity of " Natural " cement, how- ever, is imported into this country and into the British Colonies, almost entirely from Belgium. It is sold as 6 PORTLAND CEMENT. " Portland Cement," or even as " Best Portland Cement," but is very inferior, and should be carefully avoided. To explain the difference between this material and the genuine article it is necessary to say a few words concerning the composition and manufacture of Portland Cement. Chemically, it consists of lime, silica, and alumina in certain proportions, which experience has shown must not vary beyond certain limits. The Standard Specifi- cations define Portland Cement as resulting from an intimate mixture of " calcareous and argillaceous materials," which in ordinary language and practice means that chalk or limestone is mixed with clay or shale, or that marl (which is a mixture of chalk and clay in very varying proportions) is mixed with either of these in such proportions as are necessary to produce a uniform chemical composition of the resulting cement. Only by the use of separate raw materials, and by controlling their proportions from day to day, and even from hour to hour, and intimately mixing them prior to calcination, is it possible to secure a uniform chemical composition in the finished Cement. Cement pro- duced in this manner is alone entitled to be considered genuine. To distinguish it from the inferior product here- after described, it is technically known as " Artificial " Cement, and when the buyer is in any doubt he should demand a guarantee that the Cement offered to him as "Portland Cement" is "Artificial." Now, in certain parts of the world, including Belgium, there are large mineral deposits, chiefly in the form of rock, in which Nature has, in a very rough and uneven manner, mixed together the limestone and the shale. The chemical composition varies greatly in the same quarry, and the percentage of rock of even fairly accurate com- position for cement-making purposes is very small indeed. Some of it contains too much lime, but more contains too little. As it would cost too much to select only the rock of correct composition and throw away the remainder, the material is taken just as it comes, and without preliminary grinding and mixing, is thrown into the kiln and burnt, after which it is ground in the usual way. In other words, it is merely Ground Lime, and is in fact frequently sold under that description in Belgium, although more often PORTLAND CEMENT. 7 palmed off on an unsuspecting public as " Best Portland Cement." To distinguish it from the genuine artificial product it is known in the trade as " Natural " cement, but the producers and vendors are usually very careful to avoid that description and to conceal its true character whenever possible. Many serious failures have occurred from its use, and the money loss arising therefrom has sometimes been very great. Though it may sometimes turn out all right, the composition is so variable that no reliance can be placed upon it. Its specific gravity is never equal to the standard demanded for first-class cement. It is often very unsound. It will never comply with all the requirements of the British Standard Specification. Its cheapness is its only attraction, and if any failure should occur, the user will inevitably suffer a pecuniary loss far greater than any saving in first cost. For concrete work; as for other things, the best is the cheapest in the long run, and nothing but genuine artificial Portland Cement should ever be employed. 44 Natural " cement is not allowed to be supplied under the name of Portland Cement either in Germany or in the United States, where, as in Great Britain, what is to be accepted as Portland Cement is strictly defined. The user is therefore recommended in all cases to ask for English Portland Cement and to see that he gets it. The sacks or casks he receives should clearly convey this information. Any material supplied in sacks having only initials or marks, instead of the full name of the actual manufacturer, should be regarded with suspicion, as this form of marking the sacks is usually expressly adopted in order to avoid the necessity under the Mer- chandise Marks Act of marking the package " Made in Belgium," and of thereby disclosing the real nature of the contents. SLAG CEMENT. Another material to be avoided is cement manufactured from blast furnace slag. Such a cement is cheaply pro- duced, and is widely different in its composition from Portland Cement, so that it cannot be relied upon to yield durable work. Moreover, it must be used quite fresh, as it quickly deteriorates with storage, and there are many 8 PORTLAND CEMENT. instances of concrete made from slag cements disintegrating in course of time. THE TESTING OF PORTLAND CEMENT. The practical user of Portland Cement on a moderate scale is generally without the appliances necessary for carrying out the tests specified by engineers. 1. Sound neat cement pat Under any circumstances these can only be con- ducted satisfactorily in a well-equipped labora- tory and testing room, and should be entrusted only to those who have had considerable ex- perience ; otherwise the results are misleading. Except for special work, which will be hereafter referred to, b'lg. 2. Contraction cracks. the user is advised to ask either for a " medium " or " slow " setting Portland Cement. The former has been defined by the En- gineering Standards Committee as a cement which sets, when gauged neat, in not less than half an hour nor in more than two hours at nor- mal atmospheric tem- perature ; the latter is Fig- 3. Expansion cracks. PORTLAND CEMENT. 9 one which takes not less than two, nor more than seven, hours to set. To ascertain the soundness of Portland Cement in a rough and ready manner, a pat of cement half an inch in thickness should be gauged with about 22% by weight of clean fresh water and placed on a piece of glass, iron, or slate. At the end of twenty-four hours the pat on the glass should be placed in still water and left there for inspection during the progress of the work. Figs, i, 2, and 3 illustrate the difference between contraction and expansion cracks in such neat cement test pats. The pat shown in Fig. i was gauged with a perfectly sound cement, and was kept in a moist atmosphere at normal temperature (58 to 64F.) away from draughts or heat during setting. The pat was then boiled for six hours, remaining absolutely sound as shown. Fig. 2 shows a pat gauged with the same cement as Fig. i, but exposed to the sun's rays and a drying wind during setting. The cracks shown are contraction cracks and do not indicate anything wrong in the cement. Fig. 3 shows a pat gauged with an unsound cement. The cracks shown are expansion cracks. If the cement continues to increase in hardness, and its appearance is satisfactory, the user should look to other causes if the work is not good. Some years ago, when not so much was known about the chemistry of Portland Cement, there was more variation in the composition, and the cement was not ground so finely as it is to-day. There has been a steady increase in the last few years in the fineness of grinding due to (i) the appreciation of the engineering profession that this fineness of grinding is essential to produce great strength in the concrete, and (2) the improved machinery for grinding. A very finely ground Portland Cement will go further than a coarsely ground Portland Cement. The variation in the composition was attributable to inadequate methods of mixing the raw materials, and to the want of proper super- vision by chemists over every stage of the manufacture. It is customary nowadays for the composition to be tested by the analysis of samples taken at every stage of the manufacture, whereby a uniform composition is maintained, while at the same time increased knowledge of the chemistry 10 PORTLAND CEMENT. of cement has led to a better comprehension of the pro- portions necessary to give the best results. Often the old cements were over-limed ; but the imposition of standard tests now compels the manufacturer to see that practically no free lime is present, and the fineness of grinding and the hydration of cement in the process of grinding prevents any material expansion in the actual work. The Le Chatelier test is the easiest for testing the expansion of cements. This test is carried out by placing a portion of gauged neat cement within a small split cylinder of spring brass which has pointers attached, as shown in Fig. 4. The mould is placed on a small glass plate, the cement is filled in, care being taken to keep the edges of the mould gently together whilst this operation is being performed ; the mould is then covered with another glass plate, a small weight is placed on this and the mould is immediately placed in water, at a temperature of 58 to 64F., where it remains for 24 hours. It is then removed and after the distance separating the pointers has been measured, is put into a suitable tank or saucepan containing cold water, which is brought up to the 4. boil in 25 to 30 minutes and kept boil- The Le Chatelier Mould. j n g f or s j x hours. Upon removing from the boiling water it is allowed to cool, the distance separating the pointers is again measured, and the difference between this and the previous reading represents the expansion of the cement, which according to the British Standard Specification should not exceed 10 millimetres when the cement has been aerated for 24 hours, or five millimetres after seven days' aeration. It is customary now for the best manufacturers to produce a cement which does not show a greater expansion than one to two millimetres. But even if the expansion be slightly more than ten millimetres the cement in practice would probably prove satisfactory because it is not used neat. PORTLAND CEMENT. 11 INITIAL SETTING AND HARDENING. A distinction should be recognised between the initial setting and the hardening. The initial setting is the commencement of the chemical action which is set up when the water combines with the cement ; the hardening process is a much slower one. If the initial setting be interrupted the cement will take a long time to harden, and may, indeed, never set properly. For this reason the work must not be disturbed. The initial period of setting is materially affected by the atmospheric temperature at the time the cement is used, and by the temperature of the water. The warmer the weather and the water, the more rapidly will the setting take place. If it be found, after some days, that the work is still soft or setting slowly, some further time should be given, especially in cold weather ; a temperature which is little above freezing point practically arrests the chemical action which causes the Portland Cement to set. Work should not be broken up because it is thought that the cement will not set ; there is always the sample pat to be referred to. Various causes may retard the setting, but if the precautions recorded in the second chapter with regard to the making of good concrete be observed, ultimate setting may be depended upon. AERATION OF CEMENT. For many years it has been the custom of some en- gineers to aerate cement before using it on important work, by spreading it out and turning it repeatedly in order to expose it to the action of the air. This " air slaking " was a very necessary precaution with cements manufactured years ago, which were coarsely ground and often imperfectly calcined, and, as a consequence, were liable to " blow " or expand when made into concrete and deposited in position. With modern Portland Cements, manufactured under improved conditions and under skilled chemical con- trol, such process of aeration is not only antiquated and unnecessary, but is positively injurious to the strength. The value of cement as a constructional material depends entirely on its property of combining chemically with a certain amount of water, thereby forming a hard compact mass, and the finer the cement is ground the more 12 PORTLAND CEMENT. active it is. Consequently when such finely ground cement is exposed to the atmosphere it absorbs moisture with avidity, which combines with the silicates and aluminates, liberating calcium hydrate. This in turn abstracts carbonic anhydride from the air, being converted into calcium car- bonate, and a portion of the cement is thus rendered inert. If this process be continued for a sufficient length of time the whole of the material will be gradually hydrated or " killed " and will cease to have any value. Experiments have shown that exposure in a thin layer to a humid atmosphere for a period of three to four months is sufficient to render cement quite useless as a constructional material. Hence it follows that if excessive aeration destroys the whole character of the cement, partial aeration must deteriorate it to the extent to which such aeration is carried. It is simply a question of degree. With the coarse, imperfectly calcined cements of former times this deterioration was not so marked, owing to the lesser activity of such cement ; and, in any case, was of infinitely less consequence compared with the advantage derived from the cement being rendered sound, or free from the tendency to expand in the work. The best Portland Cements of to-day are quite sound, and free from any tendency to expand, when sent out from the works. The engineer can satisfy himself as to the soundness of the cement he receives by the tests^ laid down in the British Standard Specification, and if these tests are passed satis- factorily he need have no hesitation in using the cement direct from the sacks or casks without any laying out or turning whatever. The partial hydration of cement by absorption of mois- ture has the effect of retarding the setting time, and this is sometimes given as a reason for aeration, as by its means an unduly quick cement can be rendered slower setting. This, however, is a very crude and haphazard method, because although absorption of moisture lengthens the setting time, on the other hand the absorption of car- bonic anhydride results in a quickening of the setting time, and as both moisture and carbonic anhydride are always present in the atmosphere, the ultimate effect of aeration is dependent on the relative amount of each of these sub- PORTLAND CEMENT. 13 stances which the cement absorbs. This is entirely governed by the local conditions, and the setting time of a cement which has been aerated may thus be either slowed or quickened. This has not been understood by the great majority of engineers and other users of cement, and the unexpected effects on the setting time brought about by spreading and turning have usually been ascribed to some imaginary defect in the cement itself. By the patent hydrating process invented and used by the Associated Portland Cement Manufacturers (1900), Ltd., cement is scientifically matured and its setting time regulated during the process of grinding the cement clinker to powder. By this process the particles of cement are surrounded by an atmosphere of steam during their attrition and pulverisation, thus enabling every particle of the material to absorb and combine with a regulated quantity of water in the absence of carbonic anhydride. By this means the setting time can be largely controlled ; and owing to the absence of carbonic anhydride during the process, the cement particles are not rendered inert, as is the case when they are exposed to the air. When it is necessary to hold a large stock of cement, it is preferable to store it in bulk rather than in sacks. The storage shed should be thoroughly water-tight, and a timber construction, with felt or asbestos tile roof, should be adopted in preference to iron, as with the latter con- siderable condensation takes place under certain conditions of the atmosphere. The floor of the shed should be of concrete or wood. In the latter case the timber should be well seasoned and laid as close as possible, and raised at least 6 in. above the ground level to prevent absorption of moisture. As already stated, aeration of modern Portland Cement is unnecessary. 14 SAND AND COARSE MATERIAL. CONCRETE is made by mixing Portland Cement with sand (this mixture being sometimes called the matrix), and with large or fairly small particles of hard material (these latter being sometimes called the aggregate). The London Building Acts more accurately define the ingredients of concrete as cement, sand and coarse material. As coarse materials suitable for use with Portland Cement, almost any hard and fairly clean material is ser- viceable. The following are those more generally used : 1. Coke-breeze 4. Broken stone 7. Broken brick 2. Clinker 5. Slag 8. Burnt ballast 3. Shingle 6. Crushed granite and 9. Pumice and volcanic rocks trass COKE-BREEZE AND CLINKER. What is known generally under the term " breeze " is extensively used as a coarse material because of its cheap- ness, but it requires careful selection, for the term includes pan-breeze and ashes, which are entirely unsuitable, con- taining as they do small unburnt or partially burnt pieces of coal and coke and other deleterious substances such as sul- phur or sulphurous compounds, as well as being full of dust. Breeze is commonly confused with coke-breeze which is generally a suitable material, being composed of small pieces of coke and costing much more than " breeze." Coke-breeze itself should not be dusty, and it should be free from organic impurities and from ammonia or sulphur, but sometimes is not, and bad cases of expansion have been traced to inferior coke-breeze- -or rather coke-breeze con- taining pan-breeze or other unsuitable matter the probable cause being a combination of the sulphur contained in it with the lime in the cement, and the formation thereby of sulphate of lime. Scotch coal generally contains an excess of sulphur, and coke-breeze obtained therefrom should be treated with suspicion. Boiler ashes obtained from railway locomotives and SAND AND COARSE MATERIAL. 15 stationary engines are very absorbent and dangerous, as they very often contain a considerable quantity of unburnt fuel. Moreover, the fuel itself often contains a considerable quantity of limestone, and this, becoming calcined in the burning, results in quicklime, the presence of which is highly deleterious to the cement and frequently disastrous to the concrete work. Proper furnace clinkers, however, which are vitrified ashes, as a rule form excellent coarse material, except that they are porous. Both coke-breeze and clinker are light and produce concretes that are neither so heavy nor so strong under compression as those made with heavier and denser coarse materials such as stone, ballast, etc. Coke-breeze has been shown by tests not to spall and splinter under heat, though if water be applied as from a fire-engine, it will wash away the surface of the coke-breeze concrete. Water will, however, do much greater damage to heated shingle concrete when composed of particles larger than J in. maximum size. Coke-breeze, broken brick, slag and pumice are really the best coarse materials from a fire-resisting point of view. The last, however, is open to the same objection as coke- breeze namely, that it is porous. Unless great care is taken this is detrimental in certain situations, for it allows moisture to penetrate the concrete, and may after some years result in the corrosion of any embedded steel work ; but where there is no steel work this objection does not apply. For reinforced concrete, however, coke-breeze needs to be used with great care. It can be mixed in a small proportion with other coarse materials and sand, so that its porosity be considerably reduced, when it will be found advantageous under many circumstances. Even then, in connection with steelwork it is looked upon with disfavour by some persons, for, as noted above, it sometimes contains a small amount of sulphur and other substances which act upon the steel even if they do not disrupt the concrete. It suffers, how- ever, from being falsely accused by being confused with " breeze." If used in connection with steel, coke-breeze concrete should be made into a thoroughly wet mixture. A good deal of clinker from refuse destructors is now used for concrete, but it is a dangerous material, as it may 16 SAND AND COARSE MATERIAL. contain deleterious substances. It should not contain much iron if it is to be used for reinforced concrete, and it should in any case be washed. SHINGLE. Shingle forms a concrete that has very great strength as regards crushing action. For floors it should be broken fine namely, not larger than will pass a mesh j in. sq., and should be screened of particles below J in., which may be regarded as sand. For foundations, retaining walls and mass work generally there is no need to reduce the size of the particles so small; i in., ij in., 2 in. and 2\ in. may be used, mixed with plenty of smaller particles. To obtain the greatest strength from shingle it should be perfectly clean. When ballast is obtained from a river it is often fairly clean, while that obtained from the sea- shore is as a rule entirely free from loam ; very often ballast or gravel from pits contain a large quantity of loam or clay that coats every particle of the aggregate. In such cases, unless the concrete is only required to be of a poor consistency, and more for the purpose of covering an area than to develop great strength, the gravel should be washed. The reason for this is that if the particles of shingle are coated round with a firm of clay, the cement in setting does not bind these particles together and therefore homogeneity is not obtained ; in other words, there is no adhesion between the cement and the stones consequently, under a crushing load, at a certain point slipping of the surfaces, one on the other, occurs, and the concrete fails, exhibiting a much lower strength than would otherwise be developed. The presence of clay is, however, not so deleterious in sand. An angular coarse material generally gives a concrete of greater strength ; for instance, crushed shingle is superior to water-worn stones used unbroken, such as would be obtained from a pit. Formerly ballast concrete was often made without any screening and proper proportioning, but this is poor prac- tice, as a dense concrete cannot thereby be obtained ; the ballast either contains too many or too few finer particles to fill the interstices between the larger stones. Ballast is often termed gravel, though that term SAND AND COARSE MATERIAL. 17 is generally applied to fine screened pit ballast with all the loamy sand left in. When it is desired to signify that screened broken material is required it should be stated as " clean, crushed shingle, graded from f in. to J in." Shingle concrete is inclined to splinter at a high tem- perature when composed of stones of large size, especially when water comes upon it, and therefore care should be taken in its use for fire-resisting floor construction, to see that the stones are broken to a small size, not exceeding f in. BROKEN STONE. Some hard limestones form extremely strong concrete. Such, for instance, is the case when Portland stone chip- pings are used. Generally speaking, limestones should be clean and free from dust, for if dust be present the setting of the cement will be materially interfered with and the strength reduced. Limestone cannot be termed fire-re- sisting, being calcined at a high temperature; but, on the other hand, fire does not penetrate far into concrete, so that if the limestone be broken small enough it will be sufficiently satisfactory. Sandstones when broken do not as a rule afford such strong concretes as limestones ; this is perhaps partly due to the presence of fine, dusty sand, for if they are washed clean they are not greatly inferior in strength, and in most cases afford excellent concrete. Crystalline rocks, known geologically as diorites, such as in many parts are used for roads, are also excellent for concrete, and yield some of the strongest concretes. They take an intermediate place geologically between limestone and sandstone on the one hand and granite on the other. CRUSHED GRANITE. Crushed granite being of crystalline nature forms a very good coarse material for concrete. Finely crushed in the form of granite chips, it is much used for floor finishings and provides an excellent wearing surface. It must not be supposed that because granite is an extremely hard material a concrete made therewith will be superior in strength to that made with other materials that have a less crushing resistance ; for instance, clean crushed D 18 SAND AND COARSE MATERIAL. shingle has given better results than crushed granite, though the latter is generally better than unwashed gravel. Granite is composed in large proportion of mica and felspar, and, when crushed or broken, seems to contain a quantity of this in the form of fine dust, which reduces the strength of the concrete, unless it is washed. In the category of granite may be included other hard volcanic rocks such as basalt, quartzite, trap, whinstone and dense lavas. BROKEN BRICK. Broken brick is generally a good material for concrete. It is a fire-resisting material, having no tendency to splinter at high temperatures, and the small amount of porosity it possesses seems to afford plenty of adhesion. Care should be taken, however, that in breaking the bricks into small fragments too much dust is not produced, for this will be as deleterious as with granite or other materials. Some bricks contain sulphur and unslaked lime and others have been found by practice to possess qualities that render them unsuitable for concrete, so great care needs to be exercised in the choice of bricks. The greatest care should be taken in using old bricks for the making of concrete. Often sulphate of lime has been used in the form of plaster on the walls of old buildings, and if this gets in with the concrete it will result in disintegration. There have been several instances of this, and old bricks with mortar or plaster adhering to them should never be used. There have been cases of serious trouble where Keene's cement has been used on the surface of the bricks. Although it is an excellent material in itself, it is a totally unsuitable substance to mix with Portland Cement, being largely com- posed of calcium sulphate, which, in presence of water, reacts chemically with the aluminates of Portland Cement, forming sulpho-aluminate of lime, which is attended by an increase in volume. The expansion so caused may be only slight, or on the other hand, may be very considerable, depending upon the proportion of sulphate of lime present, the amount of water and its character, and other circum- stances. For instance, the same percentage of calcium SAND AND COARSE MATERIAL. 19 sulphate might be practically harmless in concrete which, after setting, remained perfectly dry, and yet be disruptive if the concrete were deposited in a wet situation and re- mained constantly damp. BURNT BALLAST. The ordinary burnt clay-ballast, as a rule, is not burnt hard enough, and produces a concrete of indifferent quality. If, however, it is well burnt it becomes brick-like and is suitable for concrete. A clay suitable for brick-making should be used, and the fuel used should be slack, i.e., small coal, or coke free from sulphur or other deleterious substances. The lumps of clay are arranged with layers of slack every 6 ins. thickness. About ij cwt. of fuel should be allowed to every cubic yard of clay. The remarks in reference to broken brick as a coarse material for concrete apply equally to burnt clay-ballast. PUMICE AND TRASS. Pumice is another fire-resisting material. It is a porous volcanic product that has undergone the ordeal of fire and is silicious, and though, being naturally light and porous, it does not give such a strong concrete as a denser material would, still it affords a greater strength than coke-breeze or clinker. Trass, tuff or puzzuolana is also a volcanic scoria, consisting of consolidated volcano ashes, and was used years ago for mixing with lime concrete to increase the strength. This it did, apparently, because it was able to combine chemically some of its silica and alumina with the lime, resulting in a compound somewhat like Portland Cement. SLAG. Slag obtained from ironstone needs to be very carefully selected. It must not contain a large amount of sulphur, as this causes expansion and the cor- rosion of metal work. It is quite insufficient, generally, to wash slag once to remove this sulphur long exposure to the air and frequent washings are necessary. Twice- 20 SAND AND COARSE MATERIAL. burnt slag, which is supplied for concrete work, consists of slag broken to the specified gauge i.e., generally about f in., and then burnt in heaps to free it from sulphur. It should afterwards be well washed and weathered in the open air. Slag obtained in the Siemens-Martin process of steel manufacture contains little sulphur, though rather a high proportion of magnetic iron oxide which may prove harmful in reinforced concrete by combining with oxygen and water, thus becoming converted into hydroxide of iron with consequent expansion, and by electrolytic action in the presence of moisture. BREAKING THE COARSE MATERIAL. Throughout this description of the nature of coarse materials for concrete work we have been referring to broken materials. The breaking is done either by hand or machinery. The former is expensive, although the results are generally superior to those obtained from machine- broken materials, for the reason that there is no crushing action to damage them. Stone-breakers that imitate the breaking of stone by hand, obtained by a knapping action given by the move- ment towards each other of two breaking jaws, are the best. The crusher form of stone-breaker has a tendency to pulverise the material over much, with the re- sult that a good deal of fine dust is pro- duced Which is harm- ffig 6 Gyratory Crusher. Fig. 5. Stone-breoTcer with knapping action. SAND AND COARSE MATERIAL. 21 ful to the strength of the concrete, as well as causing the aggregate to be damaged by the pressure exerted upon it. The crushers which have a gyratory motion given to them, so as to combine a kind of knapping motion with the crushing, overcome the above disadvantages to some extent, and if the material is washed after crushing there is no objection to their use. Fig. 5 shows a stone-breaker with knapping jaws, while Fig. 6 illustrates a gyratory crusher. WASHING THE SAND AND COARSE MATERIAL. Machinery is also used for washing the sand and coarse material, and those forms of washers in which the material Fig. 7. Mechanical sand washer. travels up a slight incline in a rotatory drum or in a station- ary drum containing a screw conveyor, with a stream of water washing down and over it, are the best, because there is no possibility of sediment. The material is shot in at the lower end, and the rotatory motion of internal screw-blades causes the material to work up the drum and to fall out at the top. Such a machine is illustrated in Fig. Another way in which the sand is often washed is by throwing it on a Fig. 8. Trough for washing sand. 22 SAND AND COARSE MATERIAL. vibrating screen having a stream of water flowing over it or suspended horizontally in a tank of water. Where mechanical washing is not available a good method is to put the material in a trough shaped as shown in Fig. 8, and keep the water running into it and over- flowing. By puddling the material the loam is removed by the running water, the heavier particles remaining behind. SIFTING THE SAND AND COARSE MATERIAL. The sifting of the sand and coarse material into various sizes is also sometimes carried out in the same manner as washing in a rotatory drum, except that the material travels down and not up the cylinder. Fig. 9 shows a form of rotatory sifter in which it will be seen that there are screens of different sizes arranged so that as the material travels therein it falls into two, three or four compartments, ac- cording to its size. For concrete, however, it is not neces- sary as a rule to have the material sifted, this being necessary only when it is to be used for special moulded work, for the small stuff, pro- vided it is not fine dust, serves to fill up Fig. 9. Rotatory sifter. ^e interstices be- tween the larger particles of the aggregate in the same manner as sand, but the proportion of the different sizes should be known. SAND. It is for the purpose of filling the interstices or voids that sand is mixed with nearly all coarse material in making a concrete. It has been proved that if sand be added sufficiently to fill up the voids between the coarse material and only just sufficient Portland Cement added to fill the interstices between the sand, a much smaller quantity of cement is needed than if the sand be omitted, while at the same time a stronger, heavier and more impervious concrete is obtained. SAND AND COARSE MATERIAL. 23 Sand of even size tends to weaken the concrete, as does also sand that is so very fine that it approaches dust in con- sistency. Evenness in size means a greater proportion of voids and either a larger quantity of Portland Cement has to be used to fill up the interstices or some remain unfilled to weaken the strength of the concrete. A well graded sand has therefore to be striven for, and when varying in size, coarse sand is the best. As a rule, a clean sand is preferable to a dirty or loamy sand, for it is dangerous to use a loamy sand unless experi- ence has shown that it is suitable for concrete work. The loam in many sands consists in great part of organic matter which is most harmful to Portland Cement. In other cases it consists of fat clay or mica not less detrimental, as these seem to reduce the strength of the Portland Cement, just as does the mixing of earthy colours, such as iron oxide, which is used for the production of red and yellow coloured concrete. But if the loam be in the nature of a sandy clay it is not so harmful ; in fact, in some instances it has been shown that a sand containing such loam will, with the same proportion of Portland Cemeint, render the iconcrete ofi greater strength than that made with the same sand washed, this being due to the fact that the fine clay particles in the sand serve the purpose of a fine sand in filling up the inter- stices between the larger particles of the sand, so producing a denser concrete ; but this is only where the proportion of cement added is insufficient to fill the voids in the sand alone, as in a proportion of 1:3. When i : 2 is the pro- portion the loam reduces the strength. As a rule, however, a loamy pit-sand requires washing to obtain a concrete of the greatest strength, though with the majority of sands it is unnecessary to do this. Fresh-water river or lake sand is preferable to pit-sand as a rule, as it is freer from particles of clay and dirt and consists wholly of silica. This also applies to sea-sand, which is perfectly suitable for concrete except that the salt in the sand results in efflorescence on the surface of the concrete. This, however, may be removed by washing the surface of the finished work with a solution of sulphuric acid, con- siderably diluted with water. The presence of salt does not affect the strength of the Portland Cement after a short 24 SAND AND COARSE MATERIAL. interval of time, though in the earlier stages it retards the setting and the hardening. After about three months no material loss of strength is noticeable, and, therefore, salt water is often used in mixing concrete in marine works: In using stones and sand from the sea-shore they should be taken from below high-water, otherwise it is probable that they will contain an undue proportion of salt, due to the spray from the waves drying upon them and so de- positing a large quantity of salt. Glacial sands (i.e., those produced by the grinding of rocks due to the action of glaciers) are found generally in the interior of countries, and are very inferior to ocean or lake sands, because they contain considerable admixture of hornblende, felspar, carbonate of lime, etc., which are soft and friable substances, decomposable by the atmosphere and deleterious to Portland Cement. Such are, of course, pit sands. FIRE RESISTANCE OF VARIOUS COARSE MATERIALS. In order to arrive at the relative fire resistance of con- cretes made with various coarse materials a series of tests were undertaken by the British Fire Prevention Committee with concrete floor slabs in which the coarse material was respectively slag, broken brick, granite, burnt ballast, coke-breeze, clinker, and Thames ballast, the Portland Cement used being the " Ferrocrete " Brand of the As- sociated Portland Cement Manufacturers (1900), Ltd. The results of tests are to be found in Report No. 101 of the British Fire Prevention Committee, but the following " Object of Test " and " Summary of Effect," with table, give a very clear view of the relative efficiency of the different coarse materials from a fire point of view. I.- Object of Test. The object was to record the effect of a fire of 3 hours' duration, the temperature to reach 1800 Fahr. (982.2 C.), but not to exceed 2200 Fahr. (1204.4 C.), followed by the application of water for two minutes. The area of the floor under investigation was divided into seven equal bays of different coarse materials, the SAND AND COARSE MATERIAL. 25 ce " KH;?I il o I *- 2 a a ' .22gr SS^^ 'Jc'Sco^, g-l|=i Illl u c C o 26 SAND AND COARSE MATERIAL. quantity and quality of Portland Cement used being iden- tical for each bay, and the nature of the concrete used being as follows : No. Parts by volume No. Parts by volume Blastfurnace IV. Burnt Ballast /Burnt Ballast 5 I. Slag Concrete -L slag " 3 Concrete jCement ... I Clean sand... 2 v . Coke-breeze (Coke-breeze 5 I Cement ... I Concrete (Cement ... I II: Broken Brickf ^ roken brick 3 VI Clink (Furnace clinker 3 Concrete lean sand - 2 Concrete Clean sand " 2 (Cement ... i ( Cement ... i III. Granite (Broken granite 3 vn ThamesBa l- (Thames ballast 3 * \ The total area of the floor under investigation was 200 ft. sup. (18.58 m. square). The soffit of each bay exposed was about 10 ft. by 2 ft. 7 in. (3.04 m. by .787 m.), the thickness being sl ins. (.139 m.). The floor was loaded with 224 Ib. per ft. sup. (1093.76 kg-, per sq. m.). The centering was struck 14 days after completion of the floor. The time allowed for drying was 40 days (autumn). II. Summary of Effect. In ten minutes after the gas was lighted the plaster began to fall off the beams and continued to do so until the end of the test. Towards the end of the test it was observed from the top of the hut that the edges of Bays Nos. I., VI. and VII. were red hot, No. VII. being the worst. On the application of water more plaster was washed off the beams than had fallen during the fire test, and some of the concrete from the underside of Bays Nos. III., IV., V., VI. and VII. was washed off. All the slabs remained in position. Bays No. IV., V. and VI. were flat on the soffit; the others were convex on the underside, No. VII. (the worst) to the extent of ij in. On the removal of the load it was found that Bays Nos. I., II., III., VI. and VII. were cracked across, No. VII. being worst. 27 CONCRETE. FOR the making of good concrete, then, a clean coarse material is required which shall be varying in size, together with the Best English artificial Portland Cement, as finely ground as it can be obtained, and a clean sharp sand of medium coarseness to fill the voids between the aggre- gates. The Portland Cement must be of sufficient quantity to fill the interstices between the sand with just sufficient over to adhere adequately to the larger aggregate. The ideal of good concrete is to make it strong enough for the particular purpose in view, but not to incur expense to make it of any better quality than is absolutely required. Concrete, therefore, should be so proportioned as to afford the necessary strength with the greatest economy. The proportioning is a matter that only requires careful treat- ment ; no special expert knowledge is necessary. In this respect the majority of work as customarily executed is not dealt with properly, and the treatment of the various materials to be used for making any concrete is determined as a rule from some set formula without regard to the qualities of the materials available, and without making a gradation according to the necessities of the case. A little preliminary forethought and careful study of the matter of proportioning will repay itself, for not only will the concrete generally be of far better quality, but great economy can often be effected by reducing the quantity of cement to a minimum, and sometimes replacing it by other materials which the old rule-of-thumb methods would have required. Strength in concrete is obtained by securing maximum density, rather than by increasing the proportion of Port- land Cement. One concrete may be made with a much larger proportion of Portland Cement than another concrete, but yet be much weaker by reason of cavities dud to not having a well graded mixture of different sizes of material to fit into each other. When once the Portland Cement fills all the cavities and adheres to each particle of the coarse material an increase in the proportion of the Portland Cement in a mixture will increase the strength 28 CONCRETE. proportionately, but the first essential is to secure the maxi- mum density, and this must be striven for at all costs. Having obtained it, we may consider the question of the different qualities of material, and the desirability of in- creasing the proportion of the Portland Cement in order to increase the strength for any desired purpose. Therefore, to secure a perfect concrete the coarse material must be so proportioned and graded in its sizes as to reduce the per- centage of voids to the minimum ; there should be sufficient smaller stones to pack between the spaces of the larger ones, then still smaller stones to pack between these, coarse sand to fill the voids between the latter, and finally medium sand to fiH the voids in the coarse sand. The Portland Cement should be called upon merely to fill the voids in the fine sand, with sufficient over to coat every particle of the coarse material, and so bind the whole toge- ther. By reducing the voids in the mixture of stones and sand we make the cement go further, which is of course on the side of economy. SELECTING A COARSE MATERIAL. In selecting a coarse material for any particular work, regard should be paid not only to its toughness, hardness and cost, but to the grading of the material with a view to obtaining the maximum density. In regard to this last, we may briefly refer to the character of coarse material to be striven for. If stone is to be used, it is best when it breaks in a cubical form ; a stone which breaks in flat layers, such as shale or slate, does not make so dense and compact a concrete as a stone with a cubical fracture, for the former laminated material cannot be rammed or tamped so closely as the latter. The size of the coarse material should be varied according to the purpose for which the concrete is to be used. In mass concrete, stones up to 2\ ins. in diameter may be used, but in walls up to, say, 12 ins. in thickness, and for floors, the stones should not be larger than f in. in diameter. In fine work, such as reinforced concrete, a finely crushed ballast or stone is preferable. Concrete of small coarse material is more fire-resisting, and the fine material will easily penetrate into all crevices and round all reinforcements. CONCRETE. 29 As before mentioned, it is not necessary to sift the finer portions of broken stone from the larger, because these smaller stones go to fill the voids between the larger ones. We must, however, examine the material as supplied to determine the proportion of voids, and what size and quantity of materials should be added thereto to fill the cavities and secure maximum density. Each fragment of stone may be looked upon as being proportionately as strong as a large solid block ob- tained by quarrying, unless it has been materially weakened by crushing, as sometimes occurs with granite, sandstone, or similar material when broken by a crushing action rather than by a knapping action such as is referred to on page 20. DUST AND DIRT. We have before referred to the weakening effect of dust upon concrete, and in any coarse material the quantity of dust should be determined, for if there be more than 10 per cent, of the sand small enough to pass a screen with 50 by 50 square meshes to the inch there will be a material reduction in strength. The dust tends to coat the larger particles and prevent the cement mortar coming in contact with and adhering thereto, and even if by thorough working up in the mixing it reaches every portion of the surface of the stone, its richness and strength are reduced by the dust, which should be estimated as part of the sand in the mortar. Coarse material should never be dirty, but it should be noted that, by thoroughly well mixing, the dirty coating may be washed off the material and so mixed in the mortar that the strength of the concrete may not be much reduced. ROUNDED AND CRUSHED PEBBLES. Some authorities argue that clean rounded pebbles make a superior concrete to broken stone, and that the roundness of the pebbles assists in arriving at compactness, being less likely to bridge and leave cavities in the concrete. It is true that in pebble or shingle concrete the percentage of voids is usually less than in a broken stone concrete where the material is not carefully graded, but when care is taken to grade the particles of the coarse material a better concrete can be made with the 30 CONCRETE. broken material than with the other, and broken shingle or stone must be accorded the preference as it is cleaner and will wedge together better if properly worked. It is some- times imagined that because broken shingle or stone is rougher than pebbles the adhesion of cement to the former is greater than to the latter, but this is an error, for if adhesion depended solely upon roughness, the cementing together of two pieces of glass would be impossi- ble, whereas we know that this can be done. It should be understood that dense concrete may be made with a coarse material containing a considerable proportion of voids and without any sand, if only sufficient ramming and tamping be employed, but as this would be extravagant only a moderate amount of labour is usually employed and the materials are carefully graded and a fair amount of water employed in view thereof. SAND. The quantity of Portland Cement required varies with the character of the sand. We may place in the category of sand all particles of aggregate up to | in. in size. There has been some discussion among experts as to the use of stone-dust for making mortar for concrete, and some assert that good results can be obtained when as much as 33 per cent, of stone-dust is present in the mortar, and that, moreover, it is superior for waterproofing purposes because it is denser. Artificial stone is often made with as large a proportion as this, but in the opinion of most authorities it is too great to secure sufficient strength for ordinary purposes. It all depends upon the kind of stone from which the dust is derived. Portland stone is excellent, but the mixed dust from masons' yards, varying in size from J in. down to the finest dust, will often give a weak mortar. Although, however, there is not much to choose between the two if the sand is well graded and clean and the stone dust is from a hard kind of stone, ordinary sand is to be considered more reliable. In selecting a sand for mortar, not only is a very fine sand dangerous because it may contain a large quantity of fine particles in the nature of loam or dust, which, as stated before, materially weaken the concrete, but a fine sand contains more voids and consequently more surfaces have to CONCRETE. 31 be coated, and thus the use of more Portland Cement and more water is involved. It is often stated that the grains of sand should be " sharp," but the term is loosely used, having more reference to cleanness than to the actual sharp- ness of the grains ; but the word generally signifies a silicious sand, for a sand which is really clean is as a rule silicious, and is better than any other kind. There is no great value in the sand being truly sharp, and, as a matter of fact, sand is seldom to be obtained of this character except from broken stone, for most sands, even when ob- tained from pits, have been water-worn and are therefore rounded. Portland Cement will adhere to the surface of a clean rounded grain as well as to a sharp grain. TO DETERMINE PROPORTIONS. To make the best concrete we should so proportion the materials as to obtain a concrete of the maximum density. To determine the correct proportions of the materials various methods may be adopted. The following is a rough one that is generally used, but there are more ac- curate methods which require very little extra trouble : take a quantity of the coarse material, place it in a vessel of known capacity ; shake it down and level it at the top care- fully ; now add water from a receptacle containing a known volume until it reaches the top surface of the material in the vessel ; then, by deducting the water not used, deter- mine the amount of water necessary to fill the voids. Sand to this amount has to be added. The quantity of voids in the sand can be only roughly ascertained by similar means, as it usually contracts in bulk when water is added, which is the condition of practice. The proportion of voids in the sand gives the proportion of cement that must be added. A porous coarse material will take up a certain amount of water and consequently the quantity added is not a true measure of the voids between the particles. A porous material should therefore be wetted before it is placed in the measure. Another fairly accurate method of proportioning is as follows : determine the proportion of voids in the coarse material by filling a measure therewith and pouring in water as described above. Also determine the percentage of voids in sand by weighing a c.ft. of packed sand and 32 CONCRETE. subtracting from 165 Ibs. (the weight of a c. ft. of quartz), multiplying by 100 and dividing the product by 165. Then proportion the cement and sand so that the cement paste will be 10 per cent, in excess of the voids in the sand, and allow sufficient of this mortar to fill the voids in the large aggregate with an excess of 10 per cent. Thus : Suppose a sand contains 38 per cent, voids and the coarse material 48 per cent, voids, then cement paste required per c. ft. of sand = 0.38 + T i_ x 0.38 = 0.42 c. ft. approximately. By trial i c. ft. of loose cement, lightly shaken, makes 0.85 c. ft. of cement paste, and requires 'ff, or approximately 2 c. ft. of sand, producing an amount of mortar equal to 0.85 + 2 (i 0.38) = 2.09 c. ft. Mortar required per c. ft. of coarse material = 0.48 + 1% x 0-48 = 0.528 c. ft. Therefore 2.09 c. ft. mortar will require tn?| = approxi- mately 4 c. ft. of coarse material. The proportions are therefore i part cement, 2 parts sand, 4 parts coarse material. The inexactitude of the foregoing methods is due to the fact that the materials differ in compactness under different methods of handling. The actual volume of voids in a coarse material may not, and usually does not, correspond with the quantity of sand required to fill the voids, chiefly because the grains of sand thrust the particles of stone apart, and a portion of the sand is, with most coarse materials, too coarse to enter the voids of the latter. With most coarse materials some of the voids are smaller than the particles of sand, which therefore get between the stones and increase the bulk of the mass. Even with thorough mixing, more sand is required than the actual volume of voids of the coarse material. It may be stated generally that the volume of sand re- quired is generally five to ten per cent, in excess of the voids as determined by the water necessary to fill them ; that is, suppose we find that a gravel has 40% of voids, we shall require to use 45% to 50% of its volume of sand. In measuring the sand, regard should be paid to the volume which it will assume when mixed with the concrete. Thus, the proportions which have been determined by the above method have reference to a sand which has been wetted to approximately the condition in practice, but if a CONCRETE. 33 sand is measured unwetted (i.e., as bought) it should be ascertained if this will reduce in bulk when wetted, and, if so, how much. The most satisfactory method, therefore, is to proportion by trial mixtures. A pair of scales is required and a piece of wrought iron pipe sealed at one end. The materials to be used for the concrete namely, the coarse material, sand and Portland Cement should be carefully weighed out and mixed to the same consistency as it is intended to employ in the work, in proportions (by weight) which seem likely to be suitable. The whole of the mixture should then be placed in the pipe and rammed or tamped therein. The height to which this certain specified weight of concrete rises, should be noted. Before the mixture has time to set it should be thrown away and the pipe cleaned. Now, another batch, using the same weights of Portland Cement and water, and the same total weight of sand and stone, but with a ratio of the weights of the sand and stone slightly different from the first mixture, should be placed in the pipe and tamped as before. The height should be again noted, and if it is less or more than in the first case, it will be a guide to further mixings. In this way after a few trials a proportion is found which gives the lowest height in the cylinder, and at the same time works well while mixing, all the stones being covered with Portland Cement. The following table is fairly reliable as regards the per- centage of voids in various materials, and may be used where it is not convenient to determine the exact percentage of voids. A box, whose weight has been ascertained, of any convenient dimensions say, i ft. by i ft. 6 in. by 2 ft. (i.e., containing 3 c. ft.) should be filled with the coarse material after it has been heated to 212 F., to drive off any moisture. The material should be put in the box loosely and the top levelled off with a straight-edge. The box should now be weighed when full. Deduct the weight of the box to ascertain the nett weight, and divide this by the number of cubic feet in the contents (i.e., by 3 in the case of a box of the dimensions suggested above). The result is the actual weight of i c. ft. of the coarse material. By reference to the following table, the percentage of voids may be ascertained. 34 CONCRETE. PERCENTAGE OF VOIDS. Weight per c. ft. Ballast Sand- stone Lime- stone (medium soft) Lime- stone (medium hard) Sandstone (hard) Granite, J31ue Stone, Lime- stone (hard) Granite (hard) Trap Rock (medium) Trap Rock . (hard) Ibs. % % % % %' % %" 70 57 53 55 57 5 60 61 75 54 5o 52 54 55 57 59 80 5i 47 49 5i 52 54 56 85 48 43 45 48 50 5i 53 90 45 40 42 45 47 48 50 95 42 37 39 4i 44 46 47 IQO 39 33 36 38 4i 43 45 f5 36 30 33 35 38 40 42 no 33 26 29 32 35 37 39 "5 30 23 26 29 32 34 36 120 27 20 23 26 29 3i 34 125 24 16 20 23 26 28 3i I 3 20 13 17 20 23 26 28 135 17 10 13 17 20 23 25 140 14 6 10 14 17 20 23 This table does not apply to fine materials such as sand, or particles fine enough to pass a J in. mesh sieve, and therefore a material that contains fine parti- cles must be sifted before its percentage of voids can be determined by the table. The finer particles must be figured as a portion of the mortar, with which we shall deal later. As the stones have been measured loose, the percentage of voids is really slightly more than would be the case in actually rammed or tamped concrete. This is due to the lubrication of the stone by the mortar, and to the wedging of the stones together under the action of tamping. This will mean that there is a slight excess of mortar which will, however, offset any unevenness in the mixing. For the purpose of ascertaining the proper proportions to use for the making of mortar we cannot determine the voids in sand by such means with any degree of accuracy. For instance, if the sand is first weighed dry and then CONCRETE. 35 water is added and its weight obtained and divided by the specific gravity so as to obtain the quantity, this will not give the actual volume of voids in the sand ; for when sand is wetted it occupies less space, though if merely damped it may be said in practice to swell in volume by reason of the particles having more adhesion and not shaking down so tightly as when quite dry, so that there are more voids in a c. ft. of damp sand than in a c. ft. of dry sand, while at the same time the available voids of the damp sand differ from the available voids of the dry sand. Fine sand takes up more moisture than coarse and swells in volume considerably more, but when it is wetted it contracts again in bulk to about the same volume as dry sand, so that it is accurate enough to ascertain the proportion of voids in sand by determining the specific gravity and volume of the sand in the dry condition. Again, water added to Portland Cement so as to form a thick paste reduces the volume, so that a c. ft. of packed dry Portland Cement will not make a c. ft. of paste. Generally speaking the finer the sand the larger the bulk of mortar it will make in any fixed proportions. At the same time and to a greater degree the finer the sand the weaker the mortar. It is much worse, therefore, to increase the bulk of concrete by substituting fine sand for coarse with the same cement and stone than it is to use a stone with fewer voids for the same purpose of increasing bulk. Fine sand should thus never be used if it can be avoided ; if it must be used then the proportion of cement should be increased to give the required strength. Economy is effected by selecting sand of the best quality, i.e., coarse sand but graded in size, sand which will produce the strongest mortar with the given proportion of cement, and then adjusting the proportion of cement to sand so as to produce concrete of a strength just sufficient for the pro- posed work. Reference has been made to the manner of determining the correct proportions by finding what produces the least volume of concrete. The same method should be applied to sand, the best being that which, when mixed with Portland Cement and water of the required proportions by weight, produces the least volume of 36 CONCRETE. mortar. Two or more sands may often be mixed together to give the desired result. In testing sands for compactness, the Portland Cement should be added, for it serves as a kind of lubricant, allowing greater com- pactness than can be obtained from the sand alone. The manner of testing the quality of the sand, or the propor- tions in which several sands should be mixed together, is to take a glass graduated measure and measure off certain quantities of the different kinds of sand so mixed together as always to give the same quantity. For instance, sup- posing we decided upon 100 c.c, of sand as the total quantity, we take 70 c.c. of coarse and 30 c.c. of fine sand, or 60 of coarse and 40 of fine. We then mix one part of Portland Cement to three parts of sand, by weight, and, after observing whether the mortar works smoothly, place it in the graduated glass, tamping it slightly therein. The volume is now read from the scale, and other mixtures made and similarly recorded. By such means we can readily deter- mine the proportion which gives the densest mortar. If the concrete requires a dense strong mortar, samples should be used which contain the most Portland Cement, taking care to stop short of causing an increase in the volume of mortar. Should, however, a very dense or strong mortar not be required for the concrete, the proportions are determined by one of the samples which contains the least Portland Cement, that is sufficiently plastic to give a good bond in the concrete. Dense mortar must be used to produce a concrete that shall be impervious to water. Having, by the foregoing method, determined the pro- portions of the mortar, the table on page 37 may be used to show the proportion of coarse material which will give the maximum density with the minimum of mortar. Thus, suppose our mortar is proportioned i part cement to 2 of sand and that our coarse material contains 48% voids, we see that to every i c. ft. of cement and 2 c. ft. of sand we shall require 4 c. ft. of coarse material. We should, how- ever, always add the cement by weight, the unit of measure- ment being that i c. ft. of Portland Cement weighs 90 Ibs. The figures given in the table for the proportions of mor- tar, such as i : 3, signify i Portland Cement, 3 sand. Concrete proportioned in this way will not only show CONCRETE. 37 Voids in Coarse Mater- ial. UUAW 1 1 1 IE.9 UP OUMW5>t IVIM I t-KIML. required (to 1 c, ft. of cement) to give a dense Concrete with mortar made of cement and sand proportioned as stated. (All Quantities Expressed in c. ft.) Proportions of Mortar. 01 lo I : I I : 2 r :2J I :3 I :3i I 14 I : 4 | I :5 :54 I :6 20 5 10 T2l T5 17-1 20 22] 2=; 27^ 30 21 4! 9^ 12 Hi I6| 19 21 2 ^ 22| 26^ 284 22 4i 9 Hi I3 16 ii 20^ 221 25 27* 23 4^ 81 10| n i5i 174 195 2l| 24 26 24 4 8^ ro| I2j Hi i6| 1*1 20| 23 25 25 4 8 10 12 14 16 18 20 22 24 26 3f 71 91 Hi *3i i54 ; 174- 191 N 23 27 34 7* gl ] I 13 14^ i6J li 201 224 28 3j 7i 9 I0f 12.) Hi : 16 i7l 19! 21) 29 3) 7 8| I0j 12 131 154 171 19 20.4 30 3^ 6| 8| IO III 134 15 i6j| 18.1 2O 31 3f4 ^ 8 9-! ui 13 H4 16 17! 194 32 3 6* 7! 9i 11 12* H 154 171 18| 33 3 6 7^ 9 ro| 12 I3 J5l i6i| i8| 34 3 6 7^ 8f ioi "I 13i H 3 r 164 171 35 2f 51 71 8^ IO "I 12| Hi !5f 174 36 2f 5^ 7 81 9f 11 I2 14 i5i i6| 37 2| 51 6| 8 94 io| I2i i3i Hf 164 38 2| si 6| 8 9i io| Mi i3i I4i i5f 39 2* 5 6i 71 9 I0| ii| I2j H I5J 40 2 5 61 7* 8| 10 ii* 12} J3f 15 4t 2 4t 6 7^ 84 9f H I2| 13* Hi 42 2i 41 6 71 H 94 I0| 12 13 Hi 43 2| 41 51 7 84 9i 10| U| I2| H 44- 2 i 44 51 6| 8 9 IOJ i I2J I3f 45 2^ .. 4* 52 1 6 71 f 10 H 12J I3i 46 2j; 4^ 5^ 6i 71 8| 9f icf 12 13 47 2 i 4i 5^T ^ 7* 8* a Id| Il| 12| 48 2 4 5i ^ 7J H 9i IOJ Il| i*4 49 2 4 5 &1 7i i 9i Ii i-it I2i 50 2 4 5 6 7 8 9 IO ii 12 5t 2 3t 5 6 6| 71 8| 9l I Of 1 ] f 52 2 2| 4| 5f 6 I 7 8| 9 io| IlJ 53 2 3S 41 5 6| 7i 84 9^ IOJ lit 54 It 3i 4i 54 , 6i 7i 8| 94 IOJ II 55 If 3i 4^ 5i 6 7i 8i 9 10 II 56 If 34 4^ 54 6A- 7i 8 9 9! ioi 57 - n 3 3i 4i si 6^ 7 8 8f 91 ICfJ 5* :?| 3-i 4i 54 6 7 7! 8 9* 10) 59 ]2 3i 4i 5 6 6| 7:1 8i 91 i6| 60 l| 34 4 5 5! 61 71 8| 94 10 38 CONCRETE. greater strength than by a haphazard system of specifying arbitrary proportions, but will also require far less Port- land Cement. As the strength of concrete depends chiefly upon securing maximum density the variations in strength are not very great when concretes are uniformly dense ; thus a concrete made with proportions i part Portland Cement, 3^ parts sand, and 10 parts coarse material, may, if the quantities of material are carefully graded, be as strong as a concrete made with i part Portland Cement, 3 parts sand, and 6 parts coarse material, not so carefully graded. Good mixing is absolutely essential, and it is best to use a machine mixer wherever the work is large enough to warrant it. IMPORTANCE OF CARE IN PROPORTIONING. That care should be exercised in proportioning con- crete is shown by the following data. The use of too much sand is as bad as the use of too little. Suppose, for instance, we have a sand with 45% voids, and a stone having 40% voids, if we just fill the voids of the stone with sand it is easy to calculate that the resultant mass would have 18% of voids; but, supposing we have 10% excess of sand, there will be 10% of material having 45% of voids and 90% having 18% of voids, which will mean that there will be 2.7% more voids in the resultant mass. It will be found in some cases that by carefully proportioning the ingredients of a concrete, an excellent admixture can be obtained with proportions of about i cement, 3 sand and 7 of coarse material, whereas the usual admixture, which in certain circumstances would serve no better purpose, would be, i cement, 2 sand and 4 of coarse material. This would mean that 30% more cement would be required, and, as the Portland Cement is the most ex- pensive ingredient, the deduction is obvious. PROPORTIONS USUALLY ADOPTED. Much of the concrete work in England is done with predetermined proportions. For reinforced concrete work where very good concrete is required, the proportions are usually i of Portland Cement to 2 of sand to 4 of coarse material. For a medium quality concrete, such as is used for foundations, walls, arches, ordinary floors and stairs, the proportions should be i : 2\ 15. For heavy walls, CONCRETE. 39 retaining walls, piers and abutments which are subjected to considerable strain, the concrete can, however, be poorer, i 13 : 6. Wherever concrete is employed in large masses and is subjected to simple compression of small intensity, or is used for a backing for brickwork or ma- sonry, or for covering the site of a building 1 to prevent the damp rising from the soil, a still poorer concrete can be used of i 14:8. In such work and in foundations large stones (commonly called " plums ") can often be placed by hand in the mass some little distance apart so as to allow them to be surrounded by the concrete ; these economise considerably without reducing the strength. QUANTITY OF CONCRETE OBTAINED FROM VARIOUS PROPORTIONS. In estimating the quantity of materials required to make a good quality of concrete, the uninitiated often think that by mixing say i part Portland Cement, 2 parts sand, and 4 parts ballast, they will obtain 7 parts by volume of concrete. They forget that trie sand goes to fill up the voids in the coarse material, and the cement to fill the voids in the sand, with the result that we are left with very little in- crease of volume. There is, however, some slight increase on the quantity of the coarse material that is to say, the quantity of concrete obtained is slightly more than the quantity of the coarse material entering therein. This varies in amount, but may generally be taken to be about one-fourteenth, or 7 per cent, increase upon the bulk of the coarse material when the proportions are rich, say i : 2 14; and one-fortieth, or 2.5 per cent, increase when the proportions are poorer, say i : z\ : 5. With very poor proportions, i.e., i : 2 : 8 and weaker, there is no increase on the bulk of the coarse material. Some values for various proportions will be found on p. 54. WATER FOR MIXING. Water used for admixture with the materials should be clean and free from acids or strong alkalis. It should also be free from organic impurities. Salt water causes Portland Cement to harden very slowly, but there is little difference in strength after a time. Very often the bad quality of the water affects the strength of the concrete. The average quantity of water required for making concrete is from 21 to 24 gallons per c. yard of dry materials. 40 CONCRETE. THE ESSENTIALS OF GOOD CONCRETE. To obtain success in concrete work only the best quality artificial Portland Cement should be used. The, further great essentials are (i) that the materials be perfectly clean and sharp, the best of their respective kinds ; (2) that they be thoroughly mixed in proportions carefully determined, and (3) that the cement be used fresh, or if it must be stored, that it be not exposed to the passage of moist air. MIXING. The mixing of concrete should be thorough ; this is as important as the proper proportioning of the concrete and the use of good materials. All ingredients should be carefully measured or weighed. A convenient form of measure for the sand and broken stone is a box without top or bottom, or a barrel with the bottom and top knocked out may be used. It is better to apportion the cement by weight, though the size of the measures used for the coarse material can be so adjusted as to permit a sack of the cement to be taken as the unit for that material. A wheelbarrow of known capacity is another unit of measure on small jobs. Water may be measured by a pail. To use a hose requires some little experience and care on the part of the person handling it, lest the Portland Cement and sand be washed away from the larger parts of the coarse material ; more- over the water cannot be measured. The concrete should be mixed as near to the place where it is to be used as practicable, for if left standing for any length of time it may set and become useless. No concrete which has begun to set should be allowed to be beaten up and re-used under any circumstances what- ever. Nevertheless, concrete that has begun to set may be treated as a coarse material if mixed with a fresh propor- tion of sand and Portland Cement. The measured materials should be spread out on a clean wooden bench or stage if the mixing is to be done by hand. If much mixing is to be done the stage should be covered with a thin piece of sheet iron or zinc plate. The sand should first be measured and then spread in a layer of even thickness. The Portland Cement should next be distributed over the surface of the sand and the whole turned over dry with CONCRETE. 41 the shovel until the two materials are seen by the uniform colour to be thoroughly mixed. The coarse material should now be thrown over the mixture and the whole turned at least three times dry and three times after wetting. It is better to add the water a little at a time until the right consistency is obtained than that it should be thrown on all at once. The best manner in which to apply the water is by means of a rose-head to a watering-can which must be filled from the measured pails. It is inadvisable to lay down any definite rule as to the percentage of water to be used in mixing concrete owing to the varying conditions which obtain, such as weather and the nature of the coarse material and sand used in each particular case. The strength of plain con- crete increases as the amount of water used in mixing is decreased, this being more particularly the case during the earlier stages of the maturing of the concrete. Eventually the wetter of two mixtures will approach more nearly to the drier in strength. Therefore for mass concrete it is usual to require that the quantity of water added to the other constituents shall be only just sufficient to bring water to the surface after thorough ramming, which ramming should make the mass quiver. In reinforced concrete, particularly in such portions as may contain a large amount of reinforcing bars or the like placed closely together, it is essential that the concrete should be sufficiently wet to pass between the reinforcing bars and to thoroughly surround every portion of the steel, though not so wet as to allow any dripping of the cement, water and sand. This should be ensured even at the expense of having the concrete wetter than would otherwise be desirable. Where the reinforcement is not very closely spaced it is unnecessary for the concrete to be so wet. In dry or hot weather the quantity of water should be increased in order to allow for evaporation. Other conditions being the same the drier the concrete the more quickly will it set and mature. This is of .import- ance when there is any danger of green concrete being attacked by frost. The wetter the concrete the greater is the tendency to contract during the process of setting and maturing. Appreciable contraction may sometimes con- tinue for a period of years. 42 CONCRETE. When the job is sufficiently large to warrant the out- lay, concrete is much better and more economically mixed by machines than by hand. There are several of these on the market, six of which are illustrated in Figs. 10 to 15. The best mixers are those known as the " Batch " type, name- ly, those in which the concrete is mixed in separate batches. The mixers shown in Figs. 10 to type, mixers are 14 are of this " Continuous " generally Fig. 10. Ransome hand-power mixing machine. Fig. 11. Hand-power mixing machine. of the form shown in Fig. 1 5, but there are also mechani- cally operated mixers of this kind which may also automati- cally measure the ingredients so as to keep them of the desired propor- t i o n s. The batch mixers do, however, allow of better control, though they also require CONCRETE. 43 Fig. 12. Taylor's rotatory mixer. to be properly oper- ated. There is a tendency for some of them to be used for heavy mass concrete work without giving the material the pro- per number of turns, so as to get the work out faster. The material in that case is shot in on one side but thrown out of the other almost immediately. To overcome this the type of mixer shown in Fig. 14 has been devised which cannot discharge the materials until the machine is stopped and its motion is reversed from the direction in which it is mixed. Fig. 10 shows a hand mixer, the drum of which has a capacity of 2 c. ft. The concrete is mixed by means of paddles set at an angle to ensure the material being always delivered towards the centre of the drum, so that the batch is mixed not only longitudinally but laterally as well. A special arrange- ment of flat steel springs is pro- vided to prevent any possibility of jamming of stones between the blades and the drum. Fig. 13. Ransome rotatory mixer. The shaft' is geared in such a manner that one man can easily revolve the paddles when the full batch is in the drum. The drum 44 CONCRETE. Fig. 14. Barker in - (c) The proportion of each grading to the whole. (d) The specific gravity of the coarse material and sand. (e) The exact dimensions of specimen cubes. (/) The weight per cubic foot of all specimens immedi- ately before testing. (g) The testing of concrete specimens shall be con- ducted on three laboratory specimens, and three specimens made on the work (see previous Clause), and shall be tested at the following periods : CONCRETE. 47 Minimum Tests. Medium Tests. Maximum Tests. (Recommended as the (Recommended to (Recommended for least that should be undertaken extensive structures be undertaken). wherever possible). and research). 7 days 7 days 7 days i year 28 28 28 ,, 2 years 56 56 56 3 90 9'o 90 4 n 6 months 9 months 6 months 5 ,, 12 ,, i year 9 2 years All specimens shall be kept in air after mixing and slightly damped for the first seven days. All cubes made up on the works shall be forwarded to the laboratory on the fifth day. After the expiration of 7 days specimens shall be kept under cover for the purpose only of protection from the direct action of rain and direct sunrays. The Committee is of opinion that for the purpose of providing for the cost of testing a provisional sum should be included in all contracts where such testing will be required, this being the most satisfactory and fairest way to all parties concerned. EFFECT OF FROST AND PREVENTION OF FREEZING. The execution of concrete work in frosty weather should be avoided as far as possible, as frost prevents the bonding of the different layers, and often causes a thin scale to peel off the surface. When the work is urgent and cannot be delayed an expedient that is often adopted is to add to the water i % by weight of salt for every degree Fahr. below the freezing point. On some jobs in the United States the man regulating the quantity of the salt carries a potato in his pocket and mixes the salt with the water for gauging until the potato just floats, when he knows the proportion is correct. A potato has a specific gravity of about 1.08, and an 8% solu- tion of salt and tap water has a specific gravity of 1.082, which will float a potato. The specific gravity of sea water is about 1.027. Salt, however, delays the hardening and retards the development of strength. In connection with reinforced concrete exposed to the weather and where there 48 CONCRETE. is risk of electrolytic action fresh water should always be used to avoid the hygroscopic action of salt which keeps the concrete damp. Another method is to mix warm sand and stone with the cement and water in such manner as to bring the temperature of the entire mixture to about 75 deg. Fahr., protecting it from the air in the early stages of the setting. The water may be heated also. During the erection of a building for the Foster-Armstrong Company, Ltd., at Rochester, N.Y., the water was heated to about 90 deg. Fahr., and salt added in about the proportion of 1.6 Ibs. per c. ft. of Portland Cement. The water was heated by passing live steam through perforated pipes in storage tanks, and the sand and gravel were heated in the storage bins by means of steam pipes and hot air pipes. Each part of the building too, as it was constructed, was housed in by a temporary structure of timber and canvas, the open sides being enclosed by canvas curtains, and the floors covered with timber shutters. The space enclosed by this housing was heated by coke fires and braziers, and by means of steam pipes from a central boiler, live steam being discharged into the spaces between the housing and the concrete. The temperature in the enclosed spaces was kept to about 80 deg. Fahr. below the floors, and about 40 deg. Fahr. in the spaces between the top of the floor and its board covering. The temperature of the concrete should, however, not be raised beyond summer heat or permanent injury may be done. In the United Kingdom it is not often that frost is so severe or so prolonged as to necessitate the extra cost of such arrangements. It is usually possible to wait ; but in urgent cases the adoption of these or similar measures will permit the work to be carried on during frost. When they are adopted, however, it is wise to assume a reduction of 25% in the normal strength. Where concrete has been exposed to the action of frost, the frost being so severe as to cause expansion of the concrete through the swelling of the water contained therein, this concrete would not again return to its original position, nor would it make a satisfactory job, and under these conditions there would appear to be no alternative CONCRETE. 49 but to remove the faulty portions, replacing with a fresh batch. In the ordinary course, however, where proper care is taken to protect the concrete, the effect of low temperatures is not likely to be permanent, and the concrete will develop its normal hardening upon the return of more favourable temperature conditions. It should be noted that any temperature below 39 degrees Fahr. practically arrests the setting action of cement, that is, even when 7 degrees above freezing point. CRACKS IN CONCRETE. The appearance of concrete surfaces is often some- what disfigured by a number of small cracks^ known as hair-cracks, this name being given because of their fineness, resembling mere lines the width of a hair on the surface. A mistake is often made in calling these " air " cracks. The mere fact of concrete drying in air does not always produce cracks. Hair-cracks are entirely on the surface, and do not indicate weakness in the concrete ; they are more apparent on a cast or finely trowelled face than on a rough floated surface, that is to say, upon a surface that has been smoothed over finely with a metal trowel than upon a surface that has only been rubbed over with a wooden or cork trowel-like tool called a float. The crazing of the surface in this way appears to be due to the cement skin which is brought to the surface by this fine trowelling with a metal trowel. Cast concrete which has been mixed fairly wet is likewise more apt to show hair-cracks than a dry mix- ture, the reason being that in wet concrete a portion of the flour or very finest particles of the cement is carried to the surfaces by the action of excess moisture so forming a richer mortar on the surfaces than is obtained in the body of the concrete. The coating of practically neat cement that is obtained in these ways, exhibits the same characteristics as neat cement mortar, which is much more liable to crazing than mortar containing a proportion of sand. Neat cement if made into test pats for laboratory pur- poses, and exposed to a current of air, will sometimes exhibit these hair-cracks, whereas, if protected in a moist closet during setting, and afterwards immersed in water for a period of at least 28 days, no hair-cracks will result. A somewhat 56 CONCRETE. similar treatment for keeping concrete wet for some time would have the same effect in eliminating hair-cracking. If the concrete be exposed to the sun it will craze if it has a very fine finish, the reason being unequal expansion between the surface and the body of the concrete under sudden changes in temperature ; the sun, for instance, will warm the blocks of concrete considerably and then suddenly when the sun is hidden and a cold wind is blowing, or possibly at nightfall when there is a sudden drop in temperature, the interior remains for a time unaffected. Naturally the surface must crack under such conditions, but the crazing is only in the neat cement finish, and does not penetrate to any depth, only the depth, practically, of a hair. Another method is to remove the thin cement skin from the face; this may be done either (i) by brushing the surface with a stiff steel wire brush, (2) by scrubbing the surface with a block of concrete and wet sand, (3) by using a sand blast, or (4) by washing with a 20 per cent, solution of hydro- chloric acid (known commonly as " spirits of salts "). The brushing or scrubbing, although it is of considerable as- sistance, requires to be supplemented by keeping the surface thoroughly and continuously wet for as long as possible. This is one of the troubles in laying cement pavements in situ where traffic is to pass over in a short period ; such pavements may exhibit a great deal of contraction after hardening in air, as it is difficult to keep the surface wet. The hair-crack trouble, however, does not matter in con- nection with concrete pavements, because the cement skin is soon removed, but the joints in the slabs will open wider, and the edges of the slab may, perhaps, rise. The surface in many cases can be kept damp by putting a layer of sand over it, or by hanging cloths over vertical surfaces, the sand or cloths being kept wet. Cracks larger than those above referred to are caused by expansion and contraction, and in long walls or large surfaces of concrete they should be prevented, either by providing joints or by reinforcing the walls with steel rods or wire. A joint may easily be formed by placing a board between the two sections of the concrete. This board may be greased and withdrawn just as the concrete is setting and the cavity filled with sand. CONCRETE. 51 Another method is to insert two or more * thicknesses of tarred paper between the sections of the work, this being left in the concrete. In plain concrete it is advisable for joints to be not further apart than 4 ft. in paving, 10 ft. in curtain walls, 15 to 20 ft. in exposed retaining walls, and 50 ft. in unexposed ' retaining walls, dock walls and dams. Experiments have proved conclusively that neat cement slightly contracts when hardening in air, and that neat cement when hardening in water shows a slight expansion. Mortars of cement and sand show the same effects, but in a much less degree. The following results have been ob- tained from experiments on expansion and contraction of neat cement, mortar and concrete : Neat Portland Cement hardened in air at the end 'of sixteen weeks shows a 0.15 per cent, contraction. One to three mortar hardened in air at the end of sixteen weeks shows a 0.05 per cent, contraction. 1:2:4 shingle concrete hardened in air at end of 21 weeks shows a 0.05 per cent, contraction. Neat Portland Cement hardened under water at the end of sixteen weeks shows an expansion of 0.05 per cent. One to three mortar hardened under water at the end of sixteen weeks shows an expansion of 0.015 per cent. 1:2:4 shingle concrete kept mc^t at end of 21 weeKS shows a 0.02 per cent expansion. For shorter periods than sixteen weeks the figures would, of course, be reduced, and the expansion and con- traction would be a trifle greater if a longer period ensued, but the chief movement occurs in a period of thirteen weeks. The contraction of concrete in hardening and under changes of temperature is considerable, and may cause the concrete to crack at irregular distances and open up widely. If a concrete surface is required to appear mono- lithic it needs a certain amount of steel or iron, not for the purpose of resisting the tension caused by contraction, but to overcome the tensile strength of the concrete and crack it uniformly throughout the length, in which case the cracks 52 CONCRETE. will be so small as to be invisible to the unaided eye. The whole of such reinforced surface should be laid at one operation. The ratio of steel introduced should be at least .005 of the sectional area of the concrete each way, and the more this is distributed throughout the concrete, the more efficient service does it render. For this reason it is preferable that the metal should be in small sections and arranged in meshlike form, a layer being placed near each face. Where the length is the only direction in which trouble may occur, vertical reinforcement is not required, so that rods placed longitudinally in the wall suffice, and are more economical. In arches and paving slabs of large area, linings to reservoirs, etc., meshw r ork or a lattice formed with rods of small section is needed. Perforated metal is also used for such purposes. Sharp angles should be avoided, or if used well reinforced by bars placed diagonally across them. There is very frequently more reason to ascribe cracks to the permanent contraction of the concrete referred to above than to temperature changes, but in some climates the variation in temperature is suffi- cient to cause cracks, and even if reinforcement be pro- vided it would be well to insert expansion and contraction joints every 50 feet. Concrete exposed to water does not shrink in setting and hardening, so that concrete linings and walls of ponds, tanks, etc., are only cracked by changes of temperature between summer and winter. If they be of plain concrete joints every 15 ft. are desirable ; if of reinforced concrete the joints may be 50 ft. apart, though it would be preferable to have them closer. Asphalt dowels may be inserted in the joints in order to prevent percolation. Cracks sometimes occur by weakness in design and construction, such as by settlement in the foundations, too high a stress in the reinforcement, too shallow beams of reinforced concrete resulting in excessive deflection, too early and careless removal of forms, weak forms and early drying of their timber resulting in straining the work by shrinkage, insufficient allowance for the monolithic nature of concrete and reinforced concrete work and the effects of irregular loading, and inadequate bond between concrete and steel due to spacing the reinforcements too CONCRETE. 53 close, using too dry a mixture and insufficient tamping, and omission of hooks to ends of rods. ESTIMATING THE COST OF CONCRETE WORK. In estimating the cost of concrete work, many factors have to be considered. The cost of timbering for the centering is one. Forms or moulds may be expensive, while the value of labour may be low, and, of course, on the other hand, in another district the opposite may be the case. Then, again, the nature of the work differs so greatly in the amount of labour necessary for placing the concrete in position and in the purpose which the work is to serve, that it is impossible to give any, even approximate, figures which would be serviceable. It can be pointed out generally, however, that concrete buildings compare very favourably in first cost with those of timber, stone, or brick, and if their lasting qualities and freedom from the expense of repairs and upkeep, as well as their hygienic value, be taken into consideration, they will be found much more economical. The cost of labour in concrete work is small in com- parison with other forms of building, as unskilled labour only is generally required, under the direction of a skilled foreman, or someone who is intelligent enough to follow and carry out instructions. In the more elaborate work carpenters are the only skilled workmen needed, except for the making of moulds for artificial stone, when joiners take their place. The cost of labour on making the concrete for a rein- forced concrete silo belonging to the Associated Portland Cement Manufacturers (1900), Ltd., at Swanscombe, in- cluding unloading, handling of shingle and cement, receiv- ing and discharging from the machine mixer, worked out at is. yd. per yard cube of solid concrete. The timber used for the forms or centering can be employed over and over again, and can be finally made use of for building roofs, partitions, etc., as the Portland Cement that will have filled the pores of the wood and adhered to the surface is no detriment. A special diagram, No. i, p. 55, has been prepared, enabling- the cost of the ingredients of concrete to be 54 CONCRETE. easily ascertained. The basis cost of the materials is expressed in the right and left-hand margins, and the cost of each ingredient per c. yard of concrete is given at the head and foot of the diagram. Thrae proportions of two kinds of concrete, namely, shingle and broken stone con- cretes, are dealt with. From the Table given below the cost of materials per c. yard of concrete for various mixtures can be ascertained. MATERIALS FOR i C. YD. OF CONCRETE. Based on loose cement weighing 90 Ibs. per c. ft. with an average specific gravity of 3.12 and a c. ft. of loose moist coarse sand weighing 89 Ibs. when dried. Proportions. Kind of Coar.e Ma:er al. Lbs. Ton land Cemen t in 1 c. yd. Sand c. yds. inlc yd. Coarse material c yds. in 1 c. yd. i : ij : 3 Shingle (40% voids) ... 666 4 I 82 Do. Broken Stone (45% voids) 697 '43 86 I : if : ' 5J Shingle ... 610 42 84 Do/ Broken Stone ... 640 '44 88 1:2: 4 Shingle ... 520 '43 86 Do. Broken Stone ... ... 548 45 90 1:2^: 5 Shingle... 43 "44 88 Do. Broken Stone ... 45 4 6 92 1:3: 6 Shingle... ... ... 364 '45 90 Do. Broken Stone 383 '47 '94 1:4: 8 Shingle ... 280 4 6 92 Do. Broken Stone ... ... 294 48 '97 Note. One of our readers, after the publication of the first edition of this book, raised the point that according- to the above 1.5 cubic yards of dry materials are required to make i cubic yard of concrete, and if such a large quantity is required, he failed to understand how contractors could price concrete 4 : 2 : i, using Thames ballast, at igj- and less per cubic yard and make a profit. His practice was to assume i yards of Thames ballast for i cubic yard of concrete, and about i cubic yards of coarse material consisting of broken stone or screened ballast. The explanation is that the Thames ballast con- crete which was referred to is not really proportioned 1:2:4 but i : 4, and the ballast has none of the sand sifted out, so that the voids in the shingle are filled, and there is little shrinkage in bulk on admixture of cement which merely goes to fill some of the voids in the sand. There is, however, too much sand in unsifted Thames ballast, and the resulting concrete is poor, the voids not being filled in a i : 4 mixture as there is insufficient cement for the purpose. We have explained above the effect of an excess of sand. The manner in CONCRETE. pjo/Cno jscj |Di.j?jD[Aj SSJDOQ puo puog p 56 CONCRETE. which some London contractors were able to make a profit at lS/- per yard cube is shown from the following method in which they worked up the price. The assumption of no shrinkage made in this estimate is, however, not strictly accurate. 4 yards Thames ballast @ 6/-... .... 24/- i ton Portland cement @ 36/- ... 36/- Divide by 4 to obtain cost of i yard ... 4 | 6o/- *s/* Add labour at 2/- per yard 2/- !7/- IVofit 10% 1/8 18/8 Where prope-r scientifically proportioned concrete is employed, as should always be the case, the values given in the table on p. 54 are accurate and obtained from experience. 57 WORKMANSHIP. FOR retaining concrete in place and giving it shape, timber centering or moulds are required. These are generally known by the term " forms/' THE BOARDING AND BATTENS, The forms are constructed of timber boards and battens of small scantling, the battens forming the framing to sup- port the boards. The boarding is usually i in., i| in. or 2 in. thick. The distance apart of the battens is governed by the Fig. 16. Forms for low wall and cellar wall. thickness of the boarding selected. The battens should be securely braced to withstand the pressure of the soft con- crete, and the stress of the ramming and tamping. Tongued and grooved or bevel-edged are better than square-edged boards, and the first-named is the best for giving a close centering, but is seldom used because the tongues and grooves are damaged in removing the centering. The ij-in. boards are satisfactory for walls, though for heavy construction 2 in. is preferable, i-in. boards should only be used for small panels of walls, i-in. boards are often used for floor centering. For the sides of girders or 58 WORKMANSHIP. beams i-in. or ij-in. boards are sufficient; for the bottom of girders 2-in. boards are preferable. The forms for columns or pillars are usually made of 2-in. plank. In many cases shutters, moulds, ties and struts, and collapsible moulds can often with advantage be used again and again for a great deal of the work, and forethought in this direction is well repaid. Timber ends may be run beyond the work they enclose so as to save the waste en- tailed by sawing. CONSTRUCTION OF FORMS. Figs. 16 to 25, 116, 125, 127, 136, 210, 223, 231 and 261 show examples of forms for various purposes. In constructing such forms the nails should not be driven home, but the heads should be left out so that it is possible to withdraw them with a claw- hammer, for the less hammering there is in con- nection with removing the forms from green con- crete the bet- ter, and there '////////"<'/////' ' injury to the timber in re- moval if this precaution is taken. There are double- headed nails now on the market which may be used. Cracks and crevices in the forms should be Fig. 18. Form for hollow irall. |^Uf- "^ J24 avoided as much as possible; if they exist, the concrete will force itself will less Form for low wall. Fig. 17. WORKMANSHIP. 59 AS23 Fig. 19. Form for solid wall. therein so as to form projections and roughnesses on the surface of the finished work. FORMS FOR WALLS. Figs. 16 and 17 show forms for the construc- tion of a low foundation or cellar wall, while Fig. 18 shows a form suit- able for the construction of hollow walls. Solid walls of con- crete can be built with various types of forms. Fig. 19 shows a useful type. As soon as a section is completed the bolts are loosened, and the slotted form of clamp or brace permits it to be readily moved up- wards. The bolts should be well / greased each time they are used so that they may be easily with- drawn. Fig. 20 shows a form suitable for the con- struction of a heavy wall, AJ2/ the ties con- Fig. 20. Form for heavy solid wall. 60 WORKMANSHIP. sisting of wire twisted to hold the side of the forms in place. Two holes are bored on each side of the form and a wire passed through them and the ends tied together. A piece of wood or a large nail is then used to twist the twp strands together. To remove the form, the wire is cut at the sides and afterwards trimmed off even with wall. If the forms for a wall get out of square and the wall becomes much out of the perpendicular there is no remedy ; it must be rebuilt. FORMS FOR GIRDERS, FLOORS, AND POSTS. In constructing forms for girders it is preferable to use hard wood wedges at top of each strut, as these can be loosened for testing if there is any deflection. The wedges should be loosened 24 hours in advance of the struts if possible. As a rule it is better to use light joists, such as 2 in. by 8 in., or 2 in. by 10 in., with frequent shores rather than timber which is heavy to handle. In ordinary conditions where the concrete is placed in layers, experience has shown that the maximum unsupported dis- tance for i-in. boards is 2 ft., for i|-in. planks 4 ft., and for 2-in. planks the studding usually varies from 3 ft. to 4 ft. 6 in. apart, according to the character of the work and the distance between the braces or walings. CENTERING. Simplification and standardisation are the ideals to be striven for. The constructions should be such as to permit the various parts of the forms to be moved independently ; thus it should be possible to remove the beam boxes without affecting the centering for the slabs in between the beams, and it should be possible to remove the column boxes without affecting any other part of the structure. This can be easily arranged as a rule, by providing sufficient struts or upright timbers ; it is a mistake to cut these down very much. The centering for the slabs is often carried on the beam boxes, and these latter in turn on the column boxes, but in this case all the parts are dependent on each other, and cannot be removed separately. The centers for different parts require to be in position for different periods of time, which gives the necessity for separation. The up- WORKMANSHIP. 61 rights can be used over and over again, so that there is no need to cut these down to a minimum ; carefulness or ingenuity in the centering should not be displayed by reducing these to a minimum so as to provide an un- encumbered space below the floor which is in course of construction, and if any elaborate work is put into the centering the labour cost will be excessive. A simple type of form for reinforced concrete construc- tion is illustrated in Figs. 21 and 22 ; it will be seen that the slab centering is separate, quite independent of the beam boxes, and that the column is independent also. By striking the folding wedges on top of the crossbars on the uprights, which are placed at either side of the secondary beam boxes, the slab centering may be removed without affecting the beam. The sides of the beam can be taken away indepen- dently of the bottom, this being advisable because it enables the concrete to dry and harden quicker. The bottoms of the beams are carried separately. The uprights are stiffened by the bolts, although it should be observed that cross bracing is necessary to prevent any movement. The column box may also be taken away before the rest of the work to enable the mass of concrete at this point to harden quicker. Fig. 22 shows how the side boards of the beams may be made to standard sizes and inserted as fillers to make up any required width ; this will save a great deal of waste in material and labour. Standardisation should not only be attempted in framing up the centering, but also in the detailing of the beams and other parts ; for instance, the sizes of beams should be varied as little as possible from floor to floor, so that the same boxes may work in over and over again, and likewise with the column boxes. It is also well if floor panels and wall panels can be made of uniform size, so as to save the cutting of the timber as much as possible, which not only means labour, but wasted material. There is often too much labour put into the centering, carpenters being particularly fond of doing elaborate work ; it not only increases the cost of the erection, but also entails unnecessary labour in removing. In designing centering the great point to bear in mind is the removal and re-erection ; it is no use putting up the 62 WORKMANSHIP. Cross section through main learn showing elevation of secondary learn. tfton CLAMP ' 4X4 4*X2" 4X4 i I [J ' | Plan of uprights and column box. Fig. 21. A standard typo of form for a concrete floor and columns. WORKMANSHIP. . FLOOR LINE . 63 1 - wovctWr / 4'X2"~ 4 ( X k 4 1 GROUND FLOOR LINE Section through secondary beams. Detail of framing to main beam and head of column box. s Side "board for Lcam (made in various sizes). Column box. Detail of iron clamp. Fig. 22. A standard type of form for a concrete floor and column. 64 WORKMANSHIP. centering so that it cannot be easily removed. Extra strength may easily be given by knocking in a few nails here and there, but these nails will cause extra labour when the centering is removed, and will damage the timber which is required to be used again. Occasionally metal moulds are employed, or wooden moulds metal faced ; in the first case they are expensive, and require standard construction so as to render them economical by permitting repetition. If thin sheet metal is employed there is the great danger of it becoming dented or bent or otherwise defaced, so as to give an imperfect surface to the concrete, while if the sheet metal is thick and strong enough to resist damage, it becomes too heavy and unwieldy or expensive to handle in practice. The kind of timber employed for forms depends on the character of the work, the kind of timber available in the locality, and its market price. White pine is the best because it is easily worked, and retains its shape when exposed to the weather, but as it is somewhat expensive, spruce or fir is generally employed, and for very rough work hemlock may be used. Timber can be of cheap quality, and need not be too well seasoned, because it is likely to swell and warp with the application of wet concrete or pre- liminary spraying with water ; however, one should not err on the other side by having timber too wet, in which event joints might open by exposure on the works, and allow the cement to wash out if the concrete be rather wet and slushy. The timber is best moderately green or partially dry. Though stiffness and rigidity in form work is to be striven for, it is unnecessary to use heavy boarding, because this will require some handling and is expensive; i-in. boards are ordinarily sufficient, though they require more strutting with supports placed more closely together, but these are preferable to employing i^-in. or 2-in. boards in an ordinary way. Special circumstances, of course, require different treatment. In a large building the centering can be used over and over again, and it may be only necessary to center one floor completely all over at a time ; when one end is finished, the part first constructed may be sufficiently set to enable the timber to be removed and re-erected. Any holes in the centering should be stopped; this can WORKMANSHIP. 65 be done with clay. If this is not done, not only will there be blemishes in the finished surface which will require to be chipped off or stopped after the centering is removed, but there may be serious loss of strength occa- sioned by the cement mortar escaping. Where work is required to show a good finish, the boards must be planed, but for ordinary work, especially where the surface will be plastered afterwards, it is customary to use rough boards. To get the timber to come away from the concrete readily, the forms are often painted with oil, but this is dangerous where steel reinforce- ments are employed, because if the oil should get on to the steel it will destroy the adhesion between it and the concrete. In moulds soft soap, linseed oil, or crude petro- leum oil are often employed. For larger finished work executed in situ the best plan is to either whitewash the boards or lay sheets of oiled paper over them. In an ordinary way it is only necessary to wet the forms with a hose before putting the concrete in place ; the water causes the wood to swell and closes the pores, and prevents the wood becoming absorbent so that the cement does not work into the timber and cause it to stick to the concrete so as to increase the labour of removal. Whatever form of protection be adopted it should be done each time the boards are used. In beams and other surfaces it is well to allow a little camber or reverse curvature to allow for the deflection or settlement when the concrete is applied and later when the forms are removed. J in. camber for every 10 ft. of span might be allowed in beams. The timber supports between bearings may deflect slightly when the concrete is applied to them. The very greatest care should be paid to seeing that all debris is removed from the forms before the concrete is put into place. One often finds an amount of sawdust left on the centering for floors, and even if swept away it will very often be found inside the column boxes. Sometimes a carpenter, if he cuts his timber wrongly or has any short pieces over, will throw them down the column boxes, which appear to him convenient receptacles ; therefore very special care should be taken to see that these column boxes are 66 WORKMANSHIP. quite clear, and every trace of sawdust, shavings, and chips removed. This can be done by leaving out a board at the bottom of the column box and putting a hose down from the top and washing away any dust, etc., through the opening thus provided. A hole is often provided in the centering of every bay of flooring so that the sawdust may be swept through. As regards struts for floor forms the following may be taken as the safe strength in Ibs. per sq. in. of cross section for different sized timber : Length of Strut. 3in.X4in. 4in.X4in. 6in. x6in. Sin. x8in. 14 ft. 500 700 900 12 ft. 6OO 8OO I,OOO 10 ft. 700 900 1,100 8 ft. 850 1,050 1,200 6 ft. 1,000 1,200 1,200 Bracing both ways will, of course, reduce the unsup- ported length in a long strut. In constructing such studding upon a concrete floor which is somewhat green, timber blocking or planks should be laid underneath the ends of the struts. The same precaution should be taken in strutting from the soil. As the wood may be crushed if the compressive stress be above 700 Ibs. per square inch, brackets must be inserted or a hard wood plate used when this figure is reached. Fig. 22 shows a post form, and Fig. 23 is a photograph of post forms in place. WEAK; FORMS TO BE AVOIDED. It should be recognised that failures may often be attributable to weak forms, and to their too speedy removal before the work has hardened. Failure may result as readily from such a cause as from imperfect design. As any settlement which may take place when the concrete is newly made might very probably prove disastrous, the forms should be very rigid. TIME iTO LEAVE FORMS IN PLACE. The time for which forms should be left in place de- pends upon the nature of the work and the conditions under which the concreting has been done. If the atmosphere be damp and the weather rainy and cold, the concrete takes WORKMANSHIP. 67 a longer time to set and harden. The time during which the form should remain in place for a floor will therefore vary from one week under the most favourable circum- stances, to six weeks or even longer. In warm weather where a floor can be concreted in a day or two it would be possible to remove the centering in a fortnight, so that one storey every two weeks could be completed from the same centering ; this would often be quite fast enough to keep pace with the con- struction of the walls and other work, but in most cases suffi- cient timber will have to be provided to center two floors. The speed at which the work can be executed depends chiefly upon the amount of timber employed for cen- tering, and if one can afford the cost o f centering the whole of a building at once, concrete, plain or reinforced, beats almost any other form of con- struction for speed. As a general rule the centering for Fig. 23. Forms for posts in position. floors, p O S t S , O r retaining walls, especially where subjected to pressure from earth or water, should not be removed under three weeks, and it is safer in any case of doubt to let it stand for four weeks. Where there is no strain upon the concrete, 24 hours may be sufficient time to leave the centering, or until the con- 68 WORKMANSHIP. crete will withstand the pressure of the thumb without indentation. Very cold or freezing weather will delay the hardening of concrete, so that in ascertaining when to strike centering the time of duration of days when the temperature was below 39 Fahr. should be deducted from the total number of days the concrete has been in place. Ordinary cold and rainy weather usually delays the work by about two to three weeks. CIRCULAR FORMS. Fig. 24. Circular form. Fig. 25. Setting-out form. A circular form may be only touched by the concrete on one side, as for a solid column or post, or there may be an outer and an inner form, one touched on the outside and the other on the inside. Fig. 24 shows the latter case namely, a form such as would be used for the construction of a silo or cistern. The outer form in this illustration would serve alone to construct a solid circular section of concrete. The way in which the parts of the form frame together is clearly shown. The simplest way in which to make this WORKMANSHIP. is to draw a circle of the size of the form desired, lay boards round its circumference as shown in Fig. 25, then lightly tack these boards together and, using the same radius, mark a circle upon them as shown. The boards may then be knocked apart and sawn out along the lines marked, the pieces being fastened together with fillets as shown in Fig. 24. After making two or three of these clamps, the boards to give the finished surface are fastened to them, these boards being known as lagging. Should it be more convenient a section of the circular form may be calculated by the following formulae (see Fig. Fig. 26. The first formula should be used when the width of board is given. The second formula should be used when the length of board is given. PUTTING CONCRETE IN PLACE. There are several points to be observed in putting the concrete in place in the forms. General directions re- garding the wetness of the concrete have already been re- ferred to (see pp. 41 and 42). The concrete should be neither very wet nor very dry; if the former, the Portland Cement will be liable to run away from the mixture through the cracks between the boarding and leave honeycombed holes between the stones ; if the latter, the concrete will be poor in quality. The con- crete should be of just the right consistency for placing in layers of not more than 8 in. depth, and tamping lightly with a wooden or iron rammer, until the water shows On Fig 27> ordinary iron barrow. 70 WORKMANSHIP. Fig. 28. Ransome concrete cart. the top and none of the stones are left uncovered with mortar. In placing concrete in posi- tion it should not be thrown from a height, as there is then a tendency for the larger and heavier parts to become s e p a - rated from the remainder o f the materials, and the presence of the air renders it less compact. Figs. 27, 28, and 29 show barrows that will be found convenient for hand- ling the concrete, while Fig. 30 shows an ordinary tipping truck that runs upon rails, and will be found advantageous on large jobs, but in the majority of cases the barrow is preferred. Fig. 29. The Anderson hand tip-cart. PLACING CONCRETE IN WATER great many engineers set their faces laying Fig. 30. Tippina truck. against concrete in water, but good work can be done in this way if care be exercised. The con- crete is often deposited through a long tube with its upper end in the open air at some height above the sur- face of the water, and WORKMANSHIP. 71 Fig. 31. Bottom opening bucket its lower end at the point where the concrete is to be laid. Concrete put in place by such methods is forced under a pressure far greater than is possible with ordinary hand ramming. There is no space for voids, and no opportunity for the entering of air, but there is a danger of sepa- ration of the cement from the other materials unless care is taken. The concrete never dries out in the process of hardening, so that concrete laid in this way can be of high quality. To lay concrete success- fully under these conditions the water should be quite still, and any movement in the water should be Ransome side tipping skip. 72 WORKMANSHIP. stopped by sheeting, so as to divide into compartments the place where the concrete is being deposited. Concrete is more usually deposited under water by employing a bucket with doors automatically opening at the bottom, as shown in Fig. 31. These doors become unlatched when the bucket lies on the bottom, and as it is pulled up the doors open and the material contained in the bucket falls gently into place. Fig. 32 shows another type of skip, in which the materials are discharged at the side by the withdrawal of a door (D) by the release of rings (A) from hooks (B), the various stages of the operation of depositing the concrete being shown in the views. The materials for such concrete work are often put in the buckets quite dry, but of course properly mixed. It is, however, better to use what is known as a " dry " mixture, the materials being mixed with a very small amount of water. If the water is much agitated top covering doors should be provided. SURFACING THE CONCRETE. In order to obtain a smooth face on the concrete one method is to work a spade or thin paddle between the con- crete and the sides of the form, moving it to and fro and up and down. This forces the large stones of the coarse material away from the boarding and brings a coating of mortar next thereto, which gives a smooth surface. The extra care required in doing this adds a little to the cost of the labour, but the trouble and time is generally repaid by the better finish of the work, and, indeed, in the saving of time and expense otherwise rendered necessary in plas- tering cavities and smoothing rough places. Another method sometimes adopted is to flush the centering with a thin coat of Portland Cement mortar proportioned about i part Portland Cement to 2 parts sand. SURFACE FINISH. The surface finish given to concrete is a matter which requires consideration. We have referred to the way in which a smooth surface can be obtained by working a paddle against the sides of the forms when the concrete is placed in position. Some persons, however, object to this smooth finish and like to see the coarse material, which is WORKMANSHIP. 73 not so monotonous as the plain surface. Figs. 33 to 44 illustrate surface finishes for concrete, in which the coarse Fig. 33. Concrete, with scrubbed surface, composed of 1 part Portland Cement, 2 parts yellow bank sand, and 3 parts f in. screened stone. Actual size. material appears upon the surface. The process consists, briefly, in removing the forms as soon as possible while the Fig. 34. Pebble and sand concrete, with scrubbed surface, composed of 1 part Portland Cement, 2 parts sand, and 3 parts A in. white pebbles. Actual size. material is still green and friable, and washing and rinsing the surface with water ; the film of cement which is formed 74 WORKMANSHIP. against the form is thus removed, and the effect depends, of course, upon the character of the coarse material in the Fig. 35. Sand and yellow pebble concrete, composed of 1 part Portland Cement, 2 parts sand, and 3 parts screened yellow pebbles. Actual size. concrete and the uniformity of its distribution in the mix- ture. If the concrete has been well mixed the Portland Fig. 36. Granite chip concrete, composed of 1 port Portland Cement, 2 parts sand, and 3 parts i in. granite chips. Actual size. Cement fills the voids between the grains of sand, and the sand fills the voids between the pebbles or pieces of crushed WORKMANSHIP. 75 stone, and the cement itself is almost invisible on the sur- face and has little influence on the colour of the work. Fig. 37. Yellow bar sand mortar, composed of 1 part Portland Cement and 3 parts yellow sand. Actual size. A special surface finish can be made quite thin, and may differ from the body of the concrete. Fig. Sand mortar composed of 1 part Portland Cement and 2 ports sand. Actual size. For instance, it may be made with crushed coarse material not exceeding f in. in size and applied to the face of the 76 WORKMANSHIP. _ < Fig. 39. Concrete, with scrubbed surface, composed of 1 part Portland Cement, 2 parts broken blue granite, all through f in. mesh and retained on i in. mesh 1 part fine blue granite chippings all through s in. mesh with fine left in. Actual size. Fig. 40. Concrete, with scrubbed surface, composed of 1 part Portland Cement, and 3 parts fine blue granite chippings all through J in. mesh with fine left in. Actual size. Fig. 41. Concrete, with scrubbed surface, composed of 1 part Portland Cement, 2 parts washed pit ballast, all through $ in. mesh and retained on i in. mesh, and 1 part pit sand all through i in. mesh with fine left in. Actual size. WORKMANSHIP. 77 Fi0. 42. concrete, writ/i scrubbed surface, composed of 1 port Portland Cement, 2 parts broken flint, all through J in. mesh, and retained on i in. mesh,, and 1 part flint grit all through $ in. mesh with fine left in. Actual size. Fig. 43. Concrete, with scrubbed surface, composed of 1 part Portland Cement, 1 parts large pit ballast, all through 1 in. mesh and retained on i in. mesh, 1 part smaZi pit ballast, all through i in. mesh and retained on in. raesTi, and part pit sand, all through J in. mesh with fine left in. Actual size. Fig. 44. Concrete, with scrubbed surface, composed of 1 part Portlanc. Cement, 2 parts broken white marble, all through 5 in. mesh and retained on i in. mesh, and 1 part fine marble chips, all through i in. mesh with fine left in. Actual size. 78 WORKMANSHIP. form with a trowel just in advance of the body concrete which is rammed into it, so as to ensure an intimate union. This finer finish can be made with materials of various colours, or coloured by the addition of mineral oxides, according to the colour scheme desired. To wash such a surface clean a good stiff wire brush is required, and the labour will be considerable unless the concrete is very green. If it should happen that a part of the face has become too hard for washing with a brush, the Portland Cement film may be rubbed with a small block 'of wood or sandstone. Another method, however, of very nearly imitating the washed sur- face is to chip with a sharp hammer and wash off with spirits of salts diluted with four times its quantity of water. The acid should be well rinsed off afterwards. It may be advisable to use acid even when the concrete is green enough for a wire brush to be effective. Where the job is of sufficient size a sand-blast jet machine may be used to dress the surface. One advantage of such rough surfaces is that no hair- cracks appear. If a rich concrete be made with broken granite and granite sand it can be polished the same as granite and to look just like it. CONCRETE SHOULD BE KEPT DAMP. The concrete when it is in the forms should be pre- vented from drying too quickly if the weather be dry or windy or the work be done in the sunshine. The surface should be protected by a layer of sand, sawdust, straw, grass or other material, or in the case of vertical work, by hanging- cloths kept continually wetted with a hose. Not only is this most advantageous to the strength of the concrete, but it prevents scaling or cracking, which may occur if the interior parts of concrete structures do not dry uniformly with the exterior. Concrete should always be kept damp as long as possible namely, throughout the progress of the job. Pavements should often be wetted even if ap- parently quite hard, and this wetting may advantageously be continued once a week for, say, six months. WATERPROOFING. The waterproofing of concrete consists either in ren- WORKMANSHIP. 79 dering the material itself impervious to water, or in the application of some other waterproof material. Concrete is often required to retain or keep out water, as in the case of water tanks, or the basement walls of buildings. If there is any tendency for the concrete to crack, owing to changes in temperature, the only way in which we can satisfactorily waterproof the concrete is to provide some covering material which is elastic. For waterworks and similar structures it is best for the flexible and elastic waterproofing compound to be embedded in the interior of the concrete. There are various flexible water- proofing materials. Some consist of a sheet of tar or bituminous composition, the bitumen or tar being applied to the surface, or impregnated into some fibrous material. Another material is thin sheet lead, which is generally protected by a covering of fibrous material. To prevent the damp rising in a concrete wall roughly made with cavities which ought not to be there if the work were properly done, layers of slates or tiles are often provided, but as these are brittle the cracks will extend right through them as the work settles. A layer of neat cement, or one of cement to two of sand, is a better damp course, but flexible materials are still better, and if sheet materials be not used, asphalt may be applied as a layer, which is done by plastering the heated asphalt to the part to be pro- tected. Where proper provision is made to prevent cracks, namely, by using high elastic limit steel reinforcement (drawn steel wire conforms to this description) in a ratio of .005 of the sectional area of the concrete, we can for general purposes do without the use of a flexible coating. In calculating the reinforcement, suppose we have a wall six inches thick, then, per foot in height of the wall, we have a sect ; onal area of 6 x 12 = 72 ; the ratio of .005 of this is 72 x. 005 .36 sq. in. of steel required for every foot in height of the wall. The steel has the effect of neutralising the resistance of the concrete, the adhesion being greater than the tensional strength of the material, and the concrete hangs or sticks on to the steel, instead of holding together for some distance and then cracking at intervals. In such a case it is only necessary to see that the concrete 80 WORKMANSHIP. is uniformly dense, and in the section relating to the mixing of the concrete, we have dealt with this point already. There are various waterproofing compounds sold for admixture with the cement or concrete, but nearly all of them have the effect of reducing the strength of the con- crete, and are in that respect disadvantageous ; their action is merely to fill the cavities in the concrete, but if the concrete be properly proportioned and made, these cavities should not exist. Many of these materials are finely divided lime with the addition of fat in the form of lime soap or tallow. The latter, when brought into contact with the lime or other alkali in the cement, becomes saponified, and this saponified scum fills the pores or cavities in the concrete, but such soap can be dissolved by water in time and its lasting properties are doubtful. Water tanks are often treated with a wash of soft soap, which prevents the water oozing through the concrete at first, but after having been in use for a short while it is found that the water either deposits vegetation or some other substance within the pores which takes the place of the temporary provision of soap, or else the continued setting of the cement in the presence of water causes internal crystallisation which chokes up the pores permanently. Some of the compounds, instead of slaked lime, con- tain very finely ground Portland Cement with tallow. The only function of this substance is to fill the pores in an imperfectly proportioned and mixed concrete ; it would be cheaper to employ slaked lime or more cement. The former has a tendency to produce efflorescence on the con- crete. There is another substance, if added in a dry state, which may be used, namely, china clay ; as already stated, a certain percentage of clay is not always a disadvantage, because it serves to fill the pores, and so produce a denser concrete. It should be noted that the clay is added and therefore does not exist as a coating round the coarse material and sand, which has been shown to be harmful. If we strive for maximum density in the concrete, which, as we have shown before, is the way to obtain maximum strength, then we naturally obtain a waterproof concrete. It is better to fill the pores with cement than with any other substances, because by so WORKMANSHIP. 81 doing the increased strength of the concrete more than offsets the difference in price. If slaked lime or china clay be employed, it should be mixed with the cement in a dry state so as to thoroughly permeate the mass. The water repelling substances found in the water- proofing compounds on the market are deleterious by reason of their very nature, which also militates against their successful application. When water is added the natural tendency is for the particles to be expelled from portions of the concrete, and collected into little masses here and there ; uniform distribution in such circumstances becomes prac- tically impossible. Sometimes an endeavour is made to over- come this by mixing the substances beforehand and adding them in the form of paste or liquid to the mixed concrete, but the same objection applies with even stronger force in this case, for the particles of solid matter mixed with the water do not enter into solution with it, but are merely suspended therein ; the liquid, therefore, acts only as a vehicle for conveying them into the concrete where they become irregularly deposited. There have been a few cases of disintegration of con- crete by sea water, though there are many examples where no such trouble has occurred even when it has been deposited under it before setting. The real trouble seems to have been a want of density in the concrete so that the sea water could penetrate into it, and enable the sulphates in solution to react with the lime in the cement and form calcium sulphate, which has resulted in a gradual breaking down of the concrete. By properly proportioning the concrete to secure maximum density this deleterious action can be prevented. The evidence of this is conclusive, because everyone knows that numerous works have been constructed such as docks, and harbours, foreshore protection, promenades, etc., rouncj the coasts of countries in all parts of the globe, and the cases of any damage or decay are extremely few and far between. Where concrete work must be done in situ and exposed almost immediately to sea water, or where deposited under water, a quick setting cement should be employed. A special cement is now being made for this class of work by the Associated Portland Cement Manufacturers (1900) Ltd. Maximum density is the proper method for rendering H 82 WORKMANSHIP. concrete waterproof, and this depends on proper propor- tioning. As has been shown in the chapter dealing with that branch of the subject, there is often a considerable proportion of voids in the concrete, and if these be filled, the percolation of sea water into the mass is prevented. No concrete is absolutely impervious to water, but it can be made very nearly impervious, and if sufficient thick- ness be provided, very little water will penetrate even under considerable pressure ; but if the water does percolate the pores generally become choked by the continued chemical action on the cement, or by the deposit of sub- stances originally in solution in the water. If concrete should not in itself be impervious, the expansion of the water in the pores would injure the concrete in case of frost. It should therefore be made as impervious as possible for this further reason. The addition of small quantities of insoluble substances to the concrete in order to fill the pores has been recommended by various authorities. Prof. Hatt advises the use of a mortar composed of i part Portland Cement to 2\ parts bituminous ash, one half of the water used for gauging being a 5% solution of ground alum, and the other half a 7% solution of soap, the alum solution being used first. Cunningham uses powdered alum equal to i% of the combined weight of sand and Portland Cement and adds i% of yellow soap to the water. Hawley uses a stock solution of 2 Ibs. extract-potash, 5 Ibs. powdered alum, and 10 quarts of water, the finishing coat being made with three quarts of the solution to each batch of mortar containing two bags of Portland Cement, the mortar being proportioned 2 sand to i Portland Cement, and the thickness of the mortar coating being \ in. Marsh advises 21 Ibs. soft soap and 12 Ibs. alum to 30 gallons of water per c. yard of mortar. The principle of using alum and soap for mixing with the concrete, or applying them in the form of a wash after- wards, depends upon the precipitation of an insoluble alum soap or hydrate of alumina, or both together. Recommendations have been made occasionally that oil should be mixed with the concrete for the purpose of waterproofing it, but experiments made with 10 per cent. WORKMANSHIP. 83 of vaseline, cylinder oil, lard, colza, and cotton seed oil, show that the crushing strength is greatly reduced by the same, and addition of oil or grease does not produce a permanent waterproof concrete. Ten per cent, of some animal and vegetable oils will destroy concrete entirely. According to Dyckerhoff, the following mixtures will be found watertight as soon as set : Portland Cement i ; sand i Do. i ; do. 2 ; lime paste Do. i ; do. 3 ; do. i Do. i ; do. 5 ; do. ij From the above mixtures one may be chosen which offers the required strength and hardness. The addition of a small proportion of slaked lime to concrete is often made, especially in districts where cement is costly and lime is cheaply and readily obtainable. This addition in comparatively small quantities has no deleterious effect upon the concrete, except as regards strength, pro- vided the lime is thoroughly broken down and free from unslaked lumps. It makes the mortar or concrete work "fatter" or freer, and results in a somewhat lighter coloured concrete which is desirable for some purposes, and renders the concrete more waterproof at early dates. In India a mixture often used for floors is ^ part of slaked lime, z\ parts Portland Cement, 3 parts sand, 4! parts of ^-inch broken stone, and 4! parts of |-inch broken stone. The sand in this case contains 44 per cent, of voids, and the ^-inch and ^-inch broken stone 48 per cent. Another method of waterproofing is to plaster the sur- face of the concrete while it is yet very green with Port- land Cement mortar, proportioned i cement to i or 2 of sand, using a trowel, and not a wooden float. The metal trowel gives a glassy finish, and prevents external pores. Water tanks and flat roofs of concrete which appear to be somewhat porous can often be rendered quite water- tight by applying a couple of coats of pure Portland Cement and water mixed as thick as cream, and put on with an ordinary whitewash brush. On a flat roof, however, this wash could be poured on and swept over with an ordinary broom. In a few exceptional cases, perhaps, a third coat might be required. 84 WORKMANSHIP. The concrete is sometimes painted with an impervious material such as pitch, tar, and asphalt or rubber paint. Another class of waterproofing consists of a kind of indurated and coated felt that is flexible and yet impervious to water. This may be stuck to the surface of the concrete with a bituminous paste, or it may be embedded in the concrete. The joints of such sheeting are overlapped and stuck together with a paste similar to that used for sticking the sheeting to the concrete. Such sheetings are much used now for the covering of roofs and the coating of elevated water tanks and reservoirs. They are often known under the general name of sheet roofings. Under the category of sheet coverings, we may also refer to the combination roofings much used in the United States, consisting of layers of tarred felt or tarred paper applied one on top of the other to the thickness of half-a- dozen or more layers, each being lapped over the other and pasted thereto with pitch or soft bituminous mixtures or solutions. Another form of lining for reservoirs, covering roofs, etc., is to apply asphalt to the surface of the concrete. This, however, has to be used hot, and the concrete must be dry to prevent the asphalt blowing. The process is thoroughly satisfactory. PORTLAND CEMENT PLASTERING. In connection with the surface coating of concrete, to which reference has already been made, it is necessary to further allude to Portland Cement plastering. This may be applied either to brickwork or concrete. In either case, the surface to which it is to be applied should be somewhat rough so as to allow the plaster to adhere. For this purpose all the joints of brickwork should be scraped out and the surface of the bricks well chipped over with a chisel or pointed hammer before plastering. The surface of concrete should likewise not be too smooth, and if it is not rough and has become hardened and dry it should be chipped over with a chisel or hammer. The walls should be thoroughly wetted before the plaster is applied, otherwise the cement will be deprived of necessary moisture and the plastering will be imperfect. Brickwork will re- quire more water than will concrete, because it is more WORKMANSHIP. 85 porous and more absorbent. The mortar should be mixed with as little water as possible, and well worked to produce plasticity. It is most important that the plaster shall be kept moist until it has thoroughly hardened. Neat Portland Cement should not be used for plas- tering ; it should be mixed with not less than one part and up to four parts of sand ; shrinkage cracks frequently appear in a mortar very rich in Portland Cement. A weak proportion is preferable to a rich one, so that 3 to i is less liable to show cracks and crazing than a mixture of 2 to i. Where the surface is always damp, and has to sustain pressure of water, it may, perhaps, be advisable to render the surface with a mixture of i of cement to i of sand, but in ordinary circumstances where the plaster dries out, i to 3 is the best proportion. A cheap form of stucco, which is serviceable enough, is made with one part Portland Cement, four parts clean sand, and a J part of lime putty. Portland Cement plaster may be coloured red by the admixture of a small quantity of red oxide of iron, and yellow by yellow ochre. To obtain a white plaster, silver sand should be used, and a small quantity of powdered whiting added namely, about one-eighth to two parts sand and one part Portland Cement. (See " Colouring of Concrete " p. 112.) Hair-cracks, or crazing, as they are technically termed, which are too frequently seen on the surface of plastering, are often attributable to the Portland Cement being mixed with an insufficient proportion of sand. This is dealt with in a separate section on p. 49. The trowelling of Portland Cement work, although advantageous from the point of view of rendering the coating waterproof, has a tendency to bring the Portland Cement to the face, and it is this thin Portland Cement film which crazes. Where possible it is better to leave the plas- tering with a surface such as is obtained by the use of a wooden float (see Fig. 48). The Portland Cement on the face of any plaster work may be removed by a strong solu- tion of hydrochloric acid (half water, half acid) applied by means of wire brushes. All traces of the acid should be afterwards washed off. In plastering with ordinary lime plaster, or the special 86 WORKMANSHIP. plasters which are now made with Plaster of Paris, it is customary to employ a rough layer for the first coat con- sisting of a weak mixture of lime and sand, and to finish off with a coat of neat plaster to give a fine surface, but with cement plaster it is preferable not to finish with cement, or, indeed, to trowel the surface so smooth as to bring a cement skin to the face. It is best to employ the same proportions throughout, consequently, the whole surface of the plastering can be brought up at one operation, and only one coat is necessary. Provided there is a good key to the surface upon which the plastering is to be placed, there is no necessity to have the plastering coat of much thickness, it can be J inch thick in many cases, though it is often made f inch thick. In plastering a surface it is usually desired that the work should be perpendicular and level throughout so that it is necessary to have some guide to which the plaster can be worked. This is obtained by constructing what are called screeds. The screeds are bands of plaster which are first of all put on the wall ; a dab of mortar is just put at points, and a plumb rule laid against it and these dabs adjusted to get the plumb vertical, then between these dabs a band of mortar is applied with a trowel, and the plumb rule scraped against it to make it quite accurate. These screeds are continued round the walls, and those first done will have set by the time the plasterer is ready to fill in between the screeds ; the screeds are placed about 6 ft. apart. The plaster is then quickly applied with a trowel shoving the material off the hawk, and surfacing it down with a darby, both of which tools are shown in Figs. 47 and 49. The darby is worked in all directions, lengthwise, cross- wise, and diagonally, finishing up with a circular motion. The surface is best finished with a wooden hand float (Fig. 48) so as to remain rough and not have the cement worked to the face, but where water is to be resisted the surface is generally worked with a metal trowel (Fig. 51). The same procedure is employed upon ceilings and floors, that is to say, screeds are first put in position and levelled, and then the intermediate spaces are filled and worked over with a straight-edge. With floors, however, these screeds often consist of straight or shaped wooden WORKMANSHIP. 87 battens, upon which a straight-edge is worked to level the material in between these wooden screeds ; these are par- ticularly useful in road construction where the surface is required to be cambered to give a fall for the removal of surface water. It is very harmful to endeavour to obtain a glassy finish by repeated trowelling which breaks up the initial set of the cement (see notes on paving, p. 174). Often cement plaster has to be done on lathing ; the lathing may be the ordinary wooden laths or metal lathings, of which there are several on the market. The timber laths should be nailed to studding spaced fairly closely together, that is to say, not more than i ft. 6 ins. or 2 feet apart, and the laths should, if possible, be nailed so as to overlap, but very often they are simply nailed with joints butting, or the ends are nailed one over the other so as to give a straight joint. This, however, may cause a crack right along the length where the laths butt. Sawn laths give an easier working surface than riven laths, but a lath that is riven is stronger because the fibres of the wood which are twisted are not divided as in the sawn lath, which is often rather short and brittle. For nailing these laths, the lath hammer shown in Fig. 46 is employed ; the hatchet portion is used for chopping the laths off to length, while the notch is for the extraction of nails, and the hammer head is for driving the lathing nails. A space of about J in. is left between the laths to provide a key for the plaster. Stronger laths are required for ceilings than for partitions. A bundle of laths contains, nominally, 500 feet. Single fir laths arte about T ^ in. thick. Lath-and-a-half laths are J in. thick. Double laths are about in. thick. Laths are about ij inches broad. A bundle of 3-feet laths and 670 nails, or a bundle of 4-feet laths and 625 nails will cover about 5 yds. super. Metal lathings have the advantage of being fire resisting. Wooden construction such as the framing in cheap country dwellings, and timber joist floors, can be protected against fire by metal lathings. In such cases the laths should be kept at least f in. away from the woodwork by an iron furring, and i in. is much better. The lathing is set off from the wood by means of special attachments, generally by bars woven into or at- 88 WORKMANSHIP. tached to the lathing or by means of iron furring consisting of bands run through straight or corrugated, | in. or f in. wide, set on edge and secured to the woodwork by narrow staples driven so as to keep the iron in a vertical position, and generally put up before the lathing is applied. The furring should be placed at about 12 inch centers unless a very stiff lathing is used. Where expanded metal is adopted the lathing should be placed so that the long way of the mesh will be at right angles to the studding or furring strips, as this ensures the greatest rigidity. The lathing is secured with staples i in. long, driven about 5 ins. apart on the stud or joist, or is wired to the metal furring. ROUGH CAST. There has been a revival of recent years in the use of what is known as rough cast for the external finish of buildings built of brick. The name is derived from the fact that the material is cast or dashed on the wall, leaving a rough surface. In some districts rough cast is known by the name of pebble dashing, and in Scotland it is called harling. There is some little distinction, however, between pebble dashing and rough cast, as will be explained later. Rough cast in the general sense is one of the oldest forms of external plastering, and many old houses of the Tudor and Stuart periods have the spaces between their timbers filled in with rough cast, often upon lathing. These tim- ber frame buildings are known generally as of half-timber work. Rough cast is a form of plastering that is very durable, and many of the old examples are in good preservation. In the stricter sense rough cast is done by mixing up fine shingle with Portland Cement in the proportion of about 3 parts to i, and using a small wooden implement shaped as shown in Fig. 50 to pick up the material and throw it on the wall, or it may be applied by means of a plasterer's trowel or wooden float similar to Figs. 48 and 51, with which the material is scraped off a plasterer's hawk (shown in Fig. 47). The danger of using a trowel for the finishing coat is that the work may look smeary and too smooth. The alternative method of pebble dashing is perhaps superior- Pebble dashing is somewhat distinct from rough WORKMANSHIP. 89 cast in this respect, that instead of the whole of the material being mixed up and thrown on to the wall, the wall is first plastered, and then when the plaster is soft pebbles are quickly and evenly thrown or dashed upon it with a scoop or hollow trowel, and then brushed with cement grout to give a uniform tint. It is not necessary that the pebbles should be coated with the cement in this process of working, although they generally are or else are white- washed afterwards. If the surface is required to be white and weather resisting which ordinary white- wash is not powdered chalk or barium sulphate should be mixed with the cement grout in the propor- tions stated in notes on the colouring of concrete, on page 112. The dashing should be done gradually, working down- wards, taking in all angles and sides of panels. Instead of gravel or shingle, other materials may be used for the dashing where this is not grouted afterwards and the rough material is required to exhibit its own colour, as, for instance, coloured glass, broken pottery, spar, and flints, which have all been used with good effects. The materials for the dashing should range from J in. to J in. in size. The rough-cast can, of course, be coloured by mixing colours with the cement, as referred to on page 112, and the first coat, where pebble dashing is employed, may be coloured also. DEPETER. Depeter is similar to rough cast in so far as it consists of forming an even surface with Portland Cement mortar and applying rougher materials thereto, but the first coat is surfaced with a hand float to give an even and uniform surface, and into the soft material are then placed by hand small pieces of stone, broken flint, pottery, spar, glass, marble, or sea shells. In depeter work bands of ornament and panels are often picked out in this way with inter- mediate plain surfaces. Good effects can sometimes be obtained by combining rough cast and depeter work. Margins and panels may often be satisfactorily treated by stamping them with special ornamental devices, or by stabbing with the stump of a nearly worn out birch broom. SGRAFFITO. Sgraffito is an Italian word meaning scratched, ancj 90 WORKMANSHIP. the simplest form of sgraffito work is the ornamentation of plaster by scratching or incising the surface with tools before it is set. The term is, however, more applied to the modern use of sgraffito which consists of modelling the cement plaster generally in low relief, though there are many examples of satisfactory treatment in high relief; the latter, however, is more in the nature of modelled work and hardly belongs to the category of sgraffito, which should be very flat in treatment though it is often combined with true sgraffito. This form of ornamenting a surface is extensively used abroad, but is not used as much as it might be in this country. In executing sgraffito, a rough coat of i part Portland Cement to 3 parts of sand is applied and finished with a roughened surface by stabbing with an old birch broom ; this coat should be brought to within about J inch of the finished face. When dry, a thin coat of cement mixed with the desired colouring matter for the background is floated over it (bone black is often used for colouring the back- ground black, and red ochre and yellow ochre and Antwerp blue are also frequently employed). When this surface coat is nearly dry, a thin skin of a different colour is applied, and where required, cut away quickly to expose the back- ground. Sometimes the background is not obtained in this way, but the surface coat is put on and the ornamenting is applied on the smooth surface, and the background is after- wards coloured by a distemper ; the first method is, how- ever, the more lasting. The outlines of the design are generally given by having a cartoon upon which the outline has been pricked through. Through the holes in this cartoon the outline is then ob- tained by pouncing ; then the cartoon is immediately re- moved and the work cut in. It is possible to put two or three coloured layers on and cut through to the different backgrounds so as to gain differently coloured effects. The top coat or coats are generally proportioned ij parts of Portland Cement to i part of colour, and laid about J in. thick. It will be seen that the sgraffito work, strictly, is not modelled, but the surface coat can be modelled if desired and even brought out in some relief. WORKMANSHIP. 91 COATED SURFACES GENERALLY. The foregoing methods of treating brickwork and walls of other materials are particularly serviceable for increasing the resistance to weather, these methods forming surfaces that are much less porous than ordinary stones or bricks. The surfaces, too, can be washed, and if much begrimed by smoke or fog, can be distempered or limewashed. As decorative methods of treatment they are cheap. In all three methods where stonework or bricks are to be coated with these kinds of cement plastering, the mortar joints should be well raked and swept out, and then the walls given as much water as they will drink, other- wise the moisture will be absorbed from the first coat of cement mortar, and it either will not set or will be lacking in strength, and come away like so much dry mud or sand. The surface of the coarse coat may be well roughened to give a good key, and, as mentioned above, this may be done by scrubbing with an old broom, though in the ordi- nary way it can be scratched over with a piece of stick, and if the final coat be put on before the first coat has hardened and dried out, a good result may be depended upon. CEMENT MORTAR. For building strong brickwork and stonework, and for making it waterproof, mortar made of Portland Cement and sand is used. The remarks made in connection with mortar entering into concrete apply to the making of Port- land Cement mortar for building brick and stone walls. For laying bricks or for grouting* the sand should be comparatively fine, while for concrete or coarse mortar it should range from fine to coarse. The usual proportions for mortar are i part Portland Cement to 3 sand, but sometimes i : 2 is used for stronger work, and i : 4 for weaker work in brickwork or masonry. If a large quantity of sand be added to the Portland Cement the mortar will be " short " and brittle so that it will not work well. For many kinds of work a quickly- hardening mortar is required, of no great strength, and if the mixture only worked well, i of Portland Cement to 5 of sand would be sufficient ; but, as such a mortar would be * See page 92. 22 WORKMANSHIP. short and adhere imperfectly to the stone or brick, the difficulty is overcome by mixing slaked or hydraulic lime with the Portland Cement to correct the faults of a mixture poor in Portland Cement. Such a mortar is cheap and very satisfactory; it hardens rapidly, possesses marked hydraulic properties, and obtains great strength on exposure to air. For face work, where Portland Cement mortar is being used, a little lime " putty " (made by mixing lime with water, passing it through a sieve and leaving it to settle and take a thick paste-like form), if added to the mortar, will make it work smoothly. The addition of lime to Portland Cement mortar increases its adhesive qualities and impermeability to water. The following proportions by volume are suitable for mortars : i Portland Cement, 5 sand, J lime paste i ,, ,, 6 to 7 sand, i ,, 1 8 ,, ij ,, 1 10 ,, 2 ,, The method of preparing Portland Cement and lime mortar is to mix the sand and cement dry, then prepare milk of lime with the necessary quantity of lime paste and water, and thoroughly mix and work it up with the mixture of sand and cement. A mistake frequently made is to mix mortar for brick- work very wet, relying upon the bricks to absorb the excess of water. It is better to wet the bricks thoroughly and use a stiff mortar. CEMENT GROUT. Pure Portland Cement and rich mixtures of sand and cement are used in the form of a watery paste for very many purposes ; in that form they are known as grout. Brickwork is often specified to be grouted in ; paving stones, setts, wood blocks and the like are also generally grouted. This grouting consists of the filling of the cavities, cracks, joints, etc., by pouring in, brushing in, or otherwise forcing such a liquid mixture of cement and , and occasionally sand, into every part. The amount WORKMANSHIP. 93 of water which should be used with the cement to make the grout, will, of course, vary with the climatic conditions, the absorptive nature of the materials it is to be used in connection with, and the general nature of the work, so that no hard and fast line can be drawn. One need only know that it is best to use as little water as possible, having regard to getting the grout to penetrate everywhere. One can do many useful things with cement grout ; for instance, one can take a heap of loose stones and pour neat cement grout into them so as to make the heap into con- crete, it does not matter, even, if the stones are damp or partially in water. It may be impossible or inadvisable to remove material in an excavation, such as a trench or pit in water-logged ground, and in such cases cement grout can be poured in, or if there is a great deal of water about, the cement sacks may be emptied directly when the water will mix therewith and form a grout ; very often this latter remedy is adopted by contractors in digging in loose ground. It is a really cheap and efficient method of over- coming many difficulties of this nature. A few tons of cement dumped into a large excavation will stop water trouble, the flooding of the excavation and, perhaps, serious destruction of already executed work. There is another application of neat cement grout which must appeal to anyone who is at all interested in archaeology, and in the preservation of ancient monumental works of architectural beauty and historical record. Our poets have assured us that old medieval builders in the Gothic period of architecture worked thoroughly and well, doing both the seen and unseen with equal care, but facts have come to light which show that economy was studied in the past even as to-day, and if there were no " jerry builders " in the past some examples show an undue striving for economy. The most noteworthy recent example is Peterborough Cathedral, where the beautiful west front was a mere facing or outward shell of stone with a backing composed of very weak mortar, practically sand. When in the reparation of that building stones were removed from the front, the sand would often run out of the holes for hours. The materials have been cemented together and the cavities filled by cement grout 94 WORKMANSHIP. pumped in with a force pump. The grouting machine, as it is called, has been largely used in this way for the repair of many ancient structures. The Auld Brig of Ayr, about which Robert Burns wrote so charmingly, was repaired recently by its atd, and other noble old stone structures have been kept in place by the same means, their weakened core or inner construction being strengthened by forcing in cement grout. The grouting machine has also been used extensively in connection with the underground railways. These are excavated by means of a steel shield, which is gradually forced forward while men take away the material in front of it. The radius of the shield is smaller than the cutting ring on the face so as to permit the insertion of cast-iron sections as the cutting face is carried forward. In putting these sections of iron tube in place cavities are left between them and the surrounding earth which, if not filled up, would be likely to cause settlement in the soil by letting water find its way round the tunnel, so gradually wearing the hole larger until the material above subsided, and, perhaps, caused serious cracking and disturbance to the buildings in the streets overhead. To prevent this, cement grout is forced into the cavities behind the section. Sewers and tunnels are now mainly driven by the use of such shields, and in all of them liquid cement grout and the grouting machine are employed. An interesting application of cement grout was the repair of a well in Germany, the water in which was pol- luted by infiltration from the upper levels. A drum of sheet iron, nearly equal in diameter to the well, was lowered to the point where the lining was needed. The annular space between the drum and the well shaft was securely caulked at the top and the bottom, and liquid cement was forced into the space and allowed to set. In this way a water-tight lining was produced at very small expense, and with great rapidity. The damaged masonry in a tunnel has also been re- paired in a similar manner by the injection of liquid cement under pressure. In the case of the well a simple pump was used for forcing in the liquid mixture of the cement ; in the case of WORKMANSHIP. 95 the tunnel, however, the cement mixture was contained in a closed vessel fitted with a delivery pipe, and an inlet, and the cement was forced through the former by means of air pressure applied to the latter at 78 Ibs. to the square inch. Fig. 45 shows a grouting machine being used for filling cracks in old masonry walls ; it will be seen to consist of an iron cylinder which acts as a receiver or reservoir, and by means of pumps, air can be forced under any pressure up to 100 Ibs. per square inch. This air receiver is connected by a flexible tube to the second portion of the apparatus called the grouting pan ; this consists of another cylinder furnished with a handle and spindle to which are attached arms or beaters so as to convert it into a churn, the object being to keep the cement and water, and some- times sand, which are introduced through the manhole at the top, in motion so as to prevent sedimentation and separation. The materials are, of course, placed in the cylinder in the proper proportions, with sufficient water to give the consistency of cream, and the lid is then screwed down. This done, the contents are then ready to be forced Fig. 45. The grouting machine in operation. 96 WORKMANSHIP. into the crack, the mouth of which on either side of the wall has been clayed up to prevent the grout escaping. Compressed air is then admitted to the grouting pan, and as soon as the necessary valve is opened, the contents ar.e discharged into the wall. EFFLORESCENCE ON CONCRETE. The most common form of efflorescence on concrete walls consists simply of a deposit of calcium carbonate either on the surface of the work generally, or, more fre- quently, in patches or streaks, particularly at places where hair-cracks or minute fissures occur. It has been assumed that this form of efflorescence is due to some inferiority of the cement, and that it is indicative of underburnt clinker, or the presence of free or uncombined lime in the cement. This view is quite erroneous, the real cause being simply percolation of water into, or through the concrete, whilst the latter is still " green," and it is strictly local in its action. The " setting " of Portland Cement is the result of chemical reactions, the chief of which is the decomposition of a complex calcium silicate which forms the main con- stituent of Portland Cement clinker. This compound in combination with the water employed for making the mortar is converted into a simpler calcium silicate with the formation of calcium hydrate, both of which salts crystallise to a solid mass, and so determines the " set." The calcium hydrate thus naturally formed in the ordinary setting of Portland Cement is a highly soluble salt, and any water percolating through the mass, or trickling along small fis- sures in the " green " concrete, carries with it to the sur- face some of the hydrate in solution. On exposure to air this absorbs carbonic anhydride (which is always present in the atmosphere), and is converted into calcium carbonate, which is deposited on the surface of the work. The percolation of water thus described seldom occurs after the concrete has aged sufficiently to allow of the crystallisation of the hydrate form, because the mass is then rendered more dense and impermeable. Even with 11 green " concrete the efflorescence does not, as a rule, proceed very far, because the calcium carbonate deposited WORKMANSHIP. 97 on the surface soon fills up or closes the pores in the work and thus prevents further action. Apart from the question of unsightliness, this form of efflorescence is of no consequence, and produces absolutely no ill effect on the work. There are occasionally other salts which ' effloresce on the surface of concrete, chiefly alkali salts, as, for instance, when silicate of soda has been mixed with the cement. In this case the water glass may react with the calcium hydrate to form calcium silicate, as the liberated alkali becomes carbonated on exposure to air. This form of efflorescence usually makes its appearance as the con- crete dries out, especially on surfaces exposed to the sun's rays. Efflorescence of alkaline chlorides and sulphates may also occur by direct solution of the salts contained in the coarse material, and more especially the sand employed. These salts are carried to the surface of the work by capillary action and are there deposited by evaporation of the w r ater. Walls of brick set in cement mortar often effloresce, and, in these cases, the trouble is seldom or never due to the mortar, as good sound mortar is usually dense enough to resist much percolation. Ordinary clay bricks are pecu- liarly liable to effloresce, the soluble salts being contained in the clay used in manufacture. The commonest forms of efflorescence on bricks are sulphates of lime or magnesia derived from the clay ; sulphates of soda and potash possibly formed by the reaction of alkaline carbonates with native gypsum in the clay ; common salt ; and carbonate of soda. In some cases where the bricks are of a specially spongey or absorbent nature, the soluble salts may even be derived from the soil lying against the foot of the wall. To remove white* efflorescence from the surface of concrete, which may be caused by using unwashed gravel or sand from the seashore, the salt in which is carried to the surface by the exosmose action of the moisture in the process of drying out, it is only necessary to wash the surface with water. Should the efflorescence reappear, the use of a solution of sulphuric acid instead of water will make the removal more permanent. This is brought about by the acid combining with a portion of the lime salts of 98 . WORKMANSHIP. the concrete, producing calcium sulphate which would par- tially close the surface pores, and thus prevent further salt solution being brought to the surface. The extent of the application of such acid solution to be efficacious will depend upon the character of the concrete and the degree of efflorescence, but for general purposes a solution of i volume of sulphuric acid (oil of vitriol) in 20 volumes of water, equivalent to about \ Ib. acid in i gallon of water, may be recommended. The acid must be added to the water very cautiously, with constant stirring, as the heat generated is very great and serious accidents may happen if the two liquids are carelessly mixed. When cold the solution may be used as a wash to remove efflorescence, but to obtain the best and most permanent results the treatment should not be applied until the concrete has thoroughly hardened some months after the completion of the work. PAINTING CEMENT AND CONCRETE SURFACES. The difficulty in painting cement or concrete walls and other surfaces arises from the fact that Portland Cement during the purely chemical action of setting, undergoes a change which results in the liberation of free alkali in the form of calcium hydrate; the solution of which salt has a powerfully destructive action upon colouring matters of an organic nature, and even upon many of the mineral pig- ments used in the manufacture of paints. In addition to this action upon the colouring matter or pigment, by which the colour may be wholly or partially discharged or decom- posed, calcium hydrate also saponifies the linseed or other vegetable oil employed as a vehicle for the pigment ; gradually converting the oil into soap and thereby rendering it soft and easily removed from the surface of the cement wall by accidental abrasion or the effects of dampness. Cement or concrete which has become thoroughly indurated has little or no effect upon paints, owing to the calcium hydrate having become carbonated to a considerable extent, and thus rendered inert ; but in the large majority of cases the work requires to be painted long before indura- tion can take place, with the result that the colour is destroyed in patches and the work rendered unsightly. Numerous methods of overcoming the difficulty have WORKMANSHIP. 99 been suggested, some of which are obviously useless, not being founded on a true conception of the conditions. Two lines of procedure offer the best promise of success, and various methods of working in these two directions have been submitted to practical trial. The broad lines of procedure are (i) coating the cement surface with an impervious or waterproof substance before applying the paint; and (2) filling the surface pores of the cement or concrete with an insoluble deposit produced by chemical action, at the same time neutralising the alkali on such surface. The first method was found to be unreliable. Various varnishes composed of resinous and fatty substances, although fairly satisfactory when the painted surface was kept dry and not exposed to damp or damp air all failed to withstand the action of moisture when exposed for 2 or 3 weeks to the outer air. The use of water-glass and other silicates gave no better results, whether the silicates were mixed with the cement, or applied to the surface after setting ; and a week or two in the open air in all cases resulted in the paint being damaged by the discharge of the colouring matter in patches. Attacking the problem by the second method mentioned, a series of experiments was made in which the cement sur- face was treated with a 20 per cent, solution of sulphuric acid, as is sometimes practised in America. This treat- ment neutralises any alkali with which the acid comes in contact, at the same time depositing calcium sulphate within the pores of the concrete. The method was entirely successful with paints made with white lead, red oxide, etc., but failed with fugitive colours like greens and blues both when exposed to damp air and when kept per- fectly dry. It cannot therefore be relied upon in all cases. A further series of experiments was made using a wash of zinc sulphate in place of dilute acid, with much more satisfactory results. The method consists in painting the cement surface 48 hours after rendering with a 50 per cent, solution of zinc sulphate in water, allowing 48 or more hours to dry, and then applying the paint in the ordinary way. The excess of zinc sulphate is not washed off with water as is necessary with acids. The action 100 WORKMANSHIP. which takes place results in the combination of zinc sulphate with calcium hydrate forming zinc hydroxide and calcium sulphate, and when dry the surface pores of the concrete are filled with a mixture of calcium sulphate and zinc oxide, neither of which have any action whatever upon the colours commonly used in paints. Treated in this way, duplicate tests exposed for some weeks to damp in the open air, remained unaffected, except in one case where a chrome green paint was slightly damaged. For inside work the method gave entirely satis- factory results. It is noteworthy that mixtures of cement and sand (i : i and i : 2) gave in all tests, better results than did neat cement. TOOLS. Very few special tools are required for making con- crete. Figs. 46 to 51 show plasterers' tools. Fig. 46 is a lath hammer, Fig. 47 a hawk, Fig. 48 a float, Fig. 49 T darby, Fig. 50 a rough cast dasher, and Fig. 51 a steel trowel. The uses of these tools are described on pp. 79- 82. Fig. 52 shows a jointer used for dividing paving in situ into sections. The projecting edge shown on this tool cuts deeply into the concrete, which is easily divided by such a tool into sections or oblongs. Fig. 59 shows a roller used for a similar purpose. Fig. 53 shows a somewhat similar tool to Fig. 52, used for rounding the edges of concrete paving. Figs. 54 and 55 show other trowel-like tools for forming round corners, while Figs. 56 and 57 show square corner smoothing trowels. Fig. 58 shows a boat-pattern tool for grooving or forming a gutter in a concrete flat or pavement. For trowelling the surface of concrete paving it is very often customary for the men to kneel, but a special tool is supplied whereby this work can be done more conveniently, and speedily, without the necessity for kneeling and bending over the work ; the tool consists practically of a trowel on the end of a long handle, and is shown in Fig. 60. It tilts so as to be in action both when pushed forward and pulled back. An indented roller (Fig. 61), for forming a series of indentations in the surface to give a foothold, is also used WORKMANSHIP. 101 Fig. 46. Lath Hammer. Fig. 47. Hawk Fig. 48. Float. Fig. 49. Darby. Fig. 50. Rough-cast dasher. Fig. 51. Plasterer's trowel Fig. 52. Jointer for dividing paving Fig. 53. Tool for rounding edges Fig. 54. Tool for rounding corners. Fig. 55. Tool for rounding corners. O- 66 - Fig 57 lool for smoothing square corners. Tool for smoothing square corners. 102 WORKMANSHIP. Fig. 63. Diagonally fluted roller Fig. 64. Border indenting roller. Fig. 65. Rough-cast roller. (I) Cross-rolled finish WORKMANSHIP. 103 for finishing concrete paving or floors. Fig. 62 shows another type of fluted roller for impressing straight indenta- tions in the concrete, while Fig. 63 shows a smaller roller with diagonal flutes for cutting diagonal lines round a border. Fig. 64 shows a further development, a border roller which cuts two straight crimps and three beads, and is used for giving some ornamental finish; the other rollers can, of course, be used for the same purpose. Fig. 65 shows another style of indenting roller, which gives a surface like Fig. 65 (a), or if used in cross-rolling gives a rough cast appearance, as seen in Fig. 65 (b). Fig. 66 is an impression frame for marking small squares in the surface of concrete carriage- ways, stable-yards, or coach-house floors. Instead of using such an impression frame the tool shown in Fig. 67 may be used which gives indentations some little distance apart, or Fig. 68 shows closer spacing, this being known as a corrugated roller. By the use of one or two rollers of the foregoing patterns with differently spaced ridges, oblongs as well as squares may be formed, and also diamonds by using the rollers diagonally. Instead of using the indented roller with pyramidical teeth, a kind of impression frame or block is often employed, such as shown in Fig. 69, which is a close pyramid, or Fig. 70, which is more open, and Fig. 71, which marks the surface out into an octagonal division with indents within the interior of the octagon ; the edges of the octagon may be cut in deeply by the use of either a jointing trowel or rotatory jointer, as shown in Fig. 59, which is intended for use in places too small for the ordinary trowel-like jointer. Of course, stamps are made with reverse lettering so as to enable an impression to be made in the concrete paving of the name of the firm executing the work or any other description. On page 72 we referred to the manner of getting a fine finish to vertical work, by means of a wooden blade ; a special improved form of such a tool is now made, and known as the Ross Concrete Spade, the form of which is shown in Fig. 72. The projections on the surface of this spade work the larger particles of the coarse material into the centre of the wall, allowing the finer material to come to the face; the other side of the tool is quite flat 104 WORKMANSHIP. Fig. 66. Impression frame. Fig. 69. Close pyramid imprefsion Uock. Fig. 70. Square Impression -block. Fig. 67. Impressing roller. Fig. 68. Corrugated roller. Fig. 71. Octagonal impression Uock. Fig. 73. A ndrews concrete tamper. Fig. 72. Ross concrete spade. Fig. 74. Bush hammer. WORKMANSHIP. 105 and works against the centering. A tool that is somewhat allied to this is the Andrews Concrete Tamper, shown in Fig. 73. This is for finishing a horizontal surface, and the teeth upon it press the larger particles of the coarse material inwards and leave the finer material to come to the surface, which is what is wanted for concrete floors, pavements, or other horizontal surfaces, especially when the surface is to be scrubbed with a wire brush to expose the coarse material. Fig. 74 shows a tool for dressing the surface of con- crete ; it is called a bush or tooling hammer. The roughening of the surface by dressing with such a hammer gives a pleasing appearance to concrete walls and removes the marks of the forms. Fig. 75 shows hand tools, and Fig. 76 pneumatic tools for giving various finishes to concrete. The labour of mixing concrete adequately by hand is considerable because the material must not only be lifted in the shovel, but the shovel turned over, and often labourers to save work will merely lift the material and throw it aside without turning it over. The ordinary square-ended tvpe of shovel employed is shown in Fig. 77. To secure a fairly uniform mixture the material must be turned a considerable number of times to get the cement and sand evenly distri- buted throughout, and this process is expedited by the use of a rake such as shown in Fig. 78. This is used for puddling the materials about when mixing is performed by hand ; the tines of the rake are wide apart so as to allow the larger particles of the coarse material to pass between, but the spacing is such as to give some little resistance to the immediate passage and the stones are pulled about from place to place in the mass, thus causing them to take a more even distribution. When making cement mortar the ordinary larry as shown in Fig. 79 is equally serviceable ; a rake in such a case would not puddle the material from one part of the mass to the other, for, being fine, it would escape through the tines ; a solid plate is therefore provided with a hole to let the material pass. If the material could not escape the labour of hauling the material through the heap would be excessive, and thus the mixing would be imperfect. 106 WORKMANSHIP flmfmyi Fig. 75. Hand surfacing tools I Fig. 76. Pnewnotic surfacing tools. Fig. 77. Square Fig. 78. Jia/ce. enrfed shovel. Fig. 79. Larry. WORKMANSHIP. 107 Figs. 83, 84, 85 Tamping irons Fig. 90. Kennedy rod "bending machine. 108 WORKMANSHIP. A convenient form of rammer is made by using a short piece of joist, but Fig. 80 shows a better one, which is easily made. Fig. 81 shows an iron rammer. These rammers are only of service where the concrete is mixed fairly dry, and is placed in thin layers. When the concrete is wetter they are not very effective, because their use simply presses down the material at the point of application, causing it to swell up in the parts adjoining, and they do not eliminate the voids. The proper forms of rammers to secure this are more in the nature of tamping or puddling irons such as shown in Figs. 83, 84, and 85, which are specially useful for tamping between closely-spaced rein- forcements. In shops which lay themselves out to do moulded work a few other tools are sometimes used ; but it is not necessary for us to refer to any here, except the wooden beater, shown in Fig. 82 and used for ramming the concrete into the moulds where an ordinary rammer could not be used. In connection with reinforced concrete a few special tools are used. Tools for twisting the steel rods in rein- forced concrete are useful, and Figs. 86 to 90 show some of a general character, the uses of which are obvious. The bending machine shown in Fig. 90 is made in several sizes, the largest bending single-handed up to ij in. dia. stcd rods cold. 109 CONCRETE BLOCKS AND MOULDED CONCRETE. CERTAIN parts of construction and articles can be moulded away from the place where they are to be used, though the bulk of concrete work is done in situ. The advantage of moulding concrete is that one mould can be used for several separate articles, with economy of labour, time and material. Some little increased expense is occasioned' by transportation, but can be overcome in great part by making the moulds conveniently near the site. Moulded work, too, is more uniform in quality and therefore better than work done in situ, owing to the experience gained by the workman through constantly working under the best conditions. ARTIFICIAL STONE. The following are a few of the articles and parts of construction which are moulded : Artificial stone blocks of all kinds for sills, cornices, string-courses, plinths, arches, lintels, columns, large pillars, capitals, paving-slabs, pipes, flower-pots, vases and steps. It is usual to make artificial stone with the best quality of artificial Portland Cement in rich proportion and with various coarse materials, usually, however, of the best kind and of superior quality. Strength, uniformity, hydrauli- city, lightness and consequent minimising of freight charges are thus secured. QUICK-SETTING PORTLAND CEMENT. A quick-setting Portland Cement is often adopted in the manufacture of moulded concrete articles, in order that the moulds may be removed quickly and so be fewer In number than would be possible with a slow-setting cement. Quick-setting Portland Cements are not, however, to be looked upon as universally or even generally advisable. 110 CONCRETE BLOCKS MOULDS. Moulds are made of wood or metal, the former being cheaper and more generally used for artificial stone- work where the blocks are large or when comparatively few are required. When, however, the moulds have to be used many times over, metal is the more lasting material. Some of the alloys which have a low melting point and a hard surface, such as Delta metal, are particularly service- able for making moulds for artificial stonework. Wooden moulds should be framed together with wooden braces tightened with wedges, and without the use of nails or latches, as these become coated with Portland Cement and get out of order. WET v. DRY MIXTURE. A wet mixture, if deposited in the moulds by hand labour, has not much strength unless properly indurated or cured, and unless a plentiful proportion of Portland Cement be used. Air-bubbles and holes are apt to form upon the moulded face and throughout the block. The surface holes may be filled with a thin Portland Cement wash, but this has a tendency afterwards to show fine hair-cracks. Sometimes the surface is rendered with a fairly thick coat of cement mortar, but both methods increase the cost. To overcome these disadvantages of moulding with a wet mixture, the moulds are often shaken by machinery with the object of causing the particles of the coarse ma- terial to pack themselves more closely and to allow the air bubbles to escape. If, however, the mould is shaken at the ends, or from all sides, with an up-and-down motion, the coarse material and the Portland Cement tend to sift them- selves out of their respective places. Shaking tables, which oscillate in all directions, but do not cause the material to move other than vertically, have been found successful in wedging particles of coarse material together so as to pro- duce a very hard and compact concrete without voids. The coarse material, too, is forced to the face of the block and all air bubbles are removed so that the face is smooth and does not need finishing by hand afterwards. This process of moulding also enables the concrete to be removed about two hours after moulding, so that the moulds can be AND MOULDED CONCRETE. 1 1 1 quickly released. The cost of this is not much greater than that of moulding dry concrete by mechanically pressing into moulds. When a dry mixture is used the concrete is tamped either by hand or compacted with a large ram. Where reinforcements are used in the mould, either the wet process must be employed or the dry process with tamping by hand labour. This tamping, too, must be very carefully done with small rammers in order to fill every interstice between and round the reinforcements. It is impossible to ram concrete into a mould with a machine rammer when rein- forcements are used. A dry mixture tamped by hand can be removed at once provided it is sustained on a base-plate of wood or metal. If metal moulds be used this base-plate consists of a thin steel or cast-iron plate which is dropped into the mould. Where mechanical pressure is used to ram the concrete within the mould a very dry mixture is desir- able, and the pressure is sufficient to cause the block to hold together so that it can be handled immediately without using a base-plate, though this is generally employed as a safeguard. Too dry a mixture for moulded concrete should be avoided, as it makes the material too short. It is as well for this reason to protect the moulds and to place them in water or wet them continually when the concrete has set. Porous material, such as broken brick, coke breeze, etc., should be well wetted before mixing, and then turned over and allowed to drain so that the surface may be damp and not wet when required for use. The hardening of concrete is often expedited by placing moulds in an atmosphere of steam at about 80 Fahr. After 24 hours the concrete is hard enough to allow the moulds to be removed even when of large size. Concrete slabs for panel walls, etc., are often hardened by pickling them in a bath of silicate of soda watered down. For paving slabs the mixture should be weak, as otherwise the slabs would be made too slippery. COLOURING OF CONCRETE. For the colouring of moulded concrete, the colouring matters, in proportions depending upon the required shade, 112 CONCRETE BLOCKS should be thoroughly mixed with the dry Portland Cement before it is added to the coarse material. The following are suitable proportions : Three parts of silver sand to one part of the following mixtures : RED. 86 parts finely- ground Portland Cement 14 ,, red oxide of iron (ferric oxide) 100 YELLOW. 88 parts finely-ground Portland Cement 12 ,, yellow ochre alternative : 90 parts finely-ground Portland Cement 100 10 ,, barium chromate BLUE. 86 parts finely-ground Portland Cement 14 azure blue or ultramarine 100 GREEN. 90 parts finely-ground Portland Cement 10 oxide of chromium 100 CHOCOLATE. 88 parts finely-ground Portland Cement 6 black oxide of manganese 4 red oxide of iron 2 black oxide of iron or copper 100 BLACK. 90 parts finely-ground Portland Cement 10 black oxide of manganese or any carbon black 100 WHITE. 67 parts finely-ground Portland Cement 33 powdered chalk or barium sulphate (common barytes) 100 PINK. 97 parts finely-ground Portland Cement 3 ,, best quality crimson lake (alumina base) 100 Experiments made to determine what effect these colours had upon the setting time of the cement showed that ferric oxide, yellow ochre, ultramarine, and chromium oxide had little effect, very slightly quickening it, but crimson lake made it quick setting and barium chromate quickened it very considerably, while manganese oxide, red ochre and Chinese red had a slowing effect. (See also remarks on the colouring of tiles, etc., given on p. 122.) AND MOULDED CONCRETE. 113 HOLLOW BLOCKS Walls have been built for many years with solid blocks, and machines for the manufacture of these were invented about thirty years ago ; but progress in the use of concrete for this purpose has been slow until the last few years, during which hollow concrete blocks have come into exten- sive use. The fundamental principles governing ordinary con- crete work apply equally to the manufacture of building blocks. To obtain strength and durability the materials must be good, and the proportioning correct. The coarse material should not be larger than in. diameter. It is important that hollow concrete blocks should not be porous. Portland Cement should be used liberally, and the mixture should not be too dry. Although some types of machines compress the concrete with a ram, hand- tamping gives the best results. The blocks are more weather resisting if they are faced with a Portland Cement mortar consisting of about 2 parts sand to i of Portland Cement, while the body of the block may be composed of poorer concrete. In order that the water in the newly-built walls may dry out and enable the building to be more quickly occupied it is well to delay plastering the walls as long as possible. To avoid the necessity of wetting the walls, should cement plaster be used intern- ally or externally as referred to on p. 84, the surface of the blocks to be plastered should be made quite rough in manufacture. Fig. 91. Types of concrete "blocks. 114 CONCRETE BLOCKS There are many varieties of shape and size for hollow blocks : we illustrate a few in Fig. 91. ADVANTAGES OF HOLLOW BLOCKS. The advantages claimed for hollow concrete block con- struction may be summarised thus : (1) Saving of material over brick or masonry. (2) Diminished cost of laying as compared with brickwork, due to the fact that the blocks are larger and require a smaller number of joints and less mortar. (3) Greater comparative strength. (4) Convenience and economy of blocks moulded to the desired form, as compared with dressed stone. (5) Resistance to fire. (6) More equable temperature of a building, making it cool in summer and easily heated in winter, while the hollow spaces provide an easy means for running pipes and electric wires, and may also be used for heating and ventilating flues. MACHINES FOR BLOCK MAKING. Machines consist, as a rule, of two main types : One in which the machinery is stationary and the concrete block is removed ; the other in which the machine is moved instead of the block. Figs. 92 and 93 show the former, and Fig. 94 the latter type. The stationary machines for moulding hollow blocks belong to either the face-down or the side-face varieties. Perfectly satisfactory blocks can be made with either form of machine provided care be taken in the manufacture. As the face-plate is generally patterned either with a rock-face, hammer-dressed face, or tool-dressed face, in imitation of stone, or with a distinctive pattern, it would not be econo- mical to use the face-plate as a base-plate. Therefore with the face-down machine the block must be turned over, so as to come away from the base-plate. Apart from this minor detail, it is substantially the same as a side-face machine, though slightly more complicated, but it is often preferred because it is a little more adapted for putting a special facing upon the block. AND MOULDED CONCRETE. 115 Concrete block machines are mostly worked by hand labour, and the tamping is done by hand. The base-plate is first dropped into t*he mould, and is usually hollowed out to allow the insertion and the withdrawal of cores which form the hollows of the block. These cores are withdrawn by means of a lever in the type of machine shown in Figs. 92 and 93. Where, however, the machine is moved and not the block, as in Fig. 94, the cores are separate, and the Fig. 92. Stationary machine for moulding concrete blocks. (The "Pioneer.") metal base-plate need not be perforated, or, indeed, a wooden base may be used. The type of machine shown in Fig. 93 is of the stationary kind, and turns out hollow blocks measuring 32 in. by 9 in. by 9 in. or several solid blocks ; it can also be used for making special angle blocks for bonding the corners of walls. The whole operation of releasing the finished blocks, i.e., removing the sides and ends of the mould and withdrawing the core, is done by the movement of one lever, while to close the mould box and replace the core ready for filling is done by a reverse movement of the same lever. Concrete blocks can often with advantage be made 116 CONCRETE BLOCKS by estate workmen in winter during frosty weather when out- side work cannot be carried on, provided the manufacturing of the blocks be carried out in some heated building where there would be no possibility of frost getting at the blocks during the first week after making. Frost is detrimental to such blocks when in the green state. Hollow concrete blocks can be built in walls seven to fourteen days after moulding. Blocks are often rendered water- proof by moulding them wetter than usual, and adding calcium hydrate Fig. 93. Stationary machine for moulding concrete "blocks. (The " Winget.") or slaked lime in the following proportions : Port- land Cement ij parts, slaked lime J part, sand 2 parts, stone chippings to pass J inch mesh and with the fine left in 3 parts. But the better method is to properly grade the materials as described on p. 28. The machines are usually adapted to making almost all sizes and shapes of irregular blocks, by inserting different moulds. The cost of hollow concrete block work for cottages varies from about 35. 6d. to 45. 6d. per yard super for AND MOULDED CONCRETE. 117 io-in. walls in comparison with 45. 3d. to 45. 6d. per yd. super for common g-in. brickwork, and often is. 6d. per yd. super has to be added to the latter figures for facing with rough-cast finish on the brickwork, which effect is, however, obtainable with the concrete blocks without any additional cost by means of the rough-faced moulds. Only a skiming coat of plaster instead of the usual three coats is required internally. Fig. 94. Movable machine for moulding concrete blocks. The style of outer face which is generally favoured is known as " rock-faced," although " chiselled " and " ashlar " are also often adopted. The face-plate is made by casting from an impression taken from an actually worked block of stone, so that the imitation of natural stone is very close, and with a little experience concrete blocks can be made which would deceive the majority of persons into the belief that they were stone, except that in a house erected with such blocks the uniformity and exact similarity of the blocks would show that they had been cast from the same mould. Whether this exact imitation of natural stone is aesthetically correct is questionable, but if the surface be somewhat in the nature of roughly dressed stone, i.e., " rock-faced," but does not exactly imitate worked stone, there is no aesthetic objection thereto. It certainly 118 CONCRETE BLOCKS gives an appearance of strength, breaks up the surface, and as all the blocks are exactly alike there is no deception as to the material ; but it is possible to avoid every objection and secure the appearance of. strength by treating the surface with a pattern. The blocks can be coloured, either by the use of mineral oxides, as mentioned on page 112, or the colour may be put upon the face by applying a first coating, in the form of mortar or stiff grout, to the side of the mould which give the outer face of the blocks. In this second method the face is often made of a richer quality than the concrete behind. This can be perfectly satisfactory, but in many cases the concrete face is not thoroughly united to the body of the block; and the difference in expansion of the two qualities of concrete is sufficient to cause trouble in crazing and perhaps flaking. Furthermore, when the blocks become wet a mottled appearance may be developed on the wall surface. SOME FINAL HINTS. A warning needs to be given to inexperienced users of concrete block machines, for failures have brought con- crete blocks into undeserved disfavour in certain quarters. Very often the materials used are unsuitable ; dirty and porous coarse materials, very loamy sand, insufficient cement, and bad mixing are fruitful causes of failure, but the chief one is the use of too dry a mixture with the desire to save time in mould- ing and handling and insufficient tamping. The con- crete should be just wet enough to hold together when squeezed in the hand. A really wet mixture can- not conveniently be used as a rule, Fig. 95. Concrete -brick-malting machine. though it makes a AND MOULDED CONCRETE. 119 denser concrete in moulds of this type. Dry- moulded blocks, and also wet-moulded ones to a lesser extent, require well curing to give good results. After the first twenty-four hours the blocks should be thoroughly wet- ted with a hose for ten minutes every mornin g and evening for a period of seven days. If the weather is at all dry they should be wetted much sooner than 24 hours. On no account should the surface of the block be al- lowed to get dry. Fig. 96. Concrete ~bricU-m2 - .888 square inches. c g a 6076 x 18 REINFORCED CONCRETE. 145 The compression taken by the steel will be .888 x 6076 - 5395 The compression taken by the concrete will be cbn 600 x Q x 7.2 __ : '9440 The total compression will be 5395 + 19440 = 24835. This is equal to the total tension, so that we shall require as tension reinforcement 248-? s = i.cc sq. ins. of steel. 16000 For our second example suppose we have a tee beam whose breadth is 50 ins., the depth of slab being 4 ins. and the maximum effective depth obtainable 16 ins. While the bending moment to be sustained is 1,280,000 in Ibs., A* 1,280,000 f then must be - = 100, and we see from ba* 50 x 16- 4 diagram that this intersects value of s 1 = -7 = .25 so as to show 680 Ibs. per sq. in. maximum fibre stress if the concrete be not reinforced in compression. Limiting this to 600 Ibs. we see that the concrete will resist a value of 86, i.e., has a moment of resistance of 86 x 50 x i6 2 = 1,100,000, leaving 1,280,000 1,100,000 = 180,000 to be resisted by the com- pressive steel. Also the neutral axis will be .36 x 16 = 5.76 in. If axis of steel be 2 in. from extreme fibre stress in steel will be- * x 600 x 14 = 5475 and area of 5-76 180000 compressive steel required = 2.35 sq. in. 5475 x 14 Compressive stress in concrete at underside of slab will be - x 600 = 183 Ibs. per sq. in. Therefore average 5-76 boo +183 compressive stress = = 391-5- lotai com- pression - 391.5 x 4 x 50 + 2.35 x 5475 = 78300 + 12870 = 91,170 Ibs. The area of steel required in tension will thus be -? = 5.7 sq. ins. 16000 Note. The stresses due to eccentric loading should be M 146 REINFORCED CONCRETE. provided for, and the algebraic sum of the stresses in any member subject to eccentric loading should not exceed the maximum permissible direct stress. The joints or connections between reinforced concrete members require close attention, as these have frequently been the weakest points. The grip or adhesion length of a bar embedded in con- crete should be measured along the bar from any given cross section to the end of the bar. Additional security should be provided by bending the ends of the bars into a J form or by mechanical bond. In the case of bars having a continuous mechanical bond it would be permissible, in calculating the grip length, to consider as the surface of the bar the periphery over the transverse projections multi- plied by the length in question. The safe grip stress is usually taken at 100 Ibs. per square inch of surface. Longitudinal bars in beams should not be less than in. diameter or thickness, and spaced not more than 6 ins. apart. All other reinforcements in beams should be at least | in. in diameter or thickness. There should be a distance of at least i in. horizontally and ^ in. vertically between the bars in beams except at joints, so as to allow the con- crete to work its way between the bars. In slabs the least diameter or thickness of steel rein- forcements should be T \y in., and the bars should be at least an inch apart, except at junctions and at parts where the bars are in direct contact and transverse to one another, and they should be not more than 12 in. apart. If the ten- sile reinforcement runs in one direction, distributing bars not less than ^in. diameter should be placed transversely not more than 18 ins. apart. Shear members, where provided, should be passed under or round the tensile reinforcement, or be otherwise secured thereto, and extend from the tensile reinforcement to the centre of pressure in the concrete. They should have a mechanical anchorage at both ends or they should have mechanical bond with the concrete throughout their length, such mechanical bond being calculated on the por- tion embedded above the neutral axis. These calculations and tables should enable any engineer or architect to check reinforced concrete designs and even design small structures. REINFORCED CONCRETE. 147 As previously stated, however, no work of any magni- tude should be undertaken without considerable previous experience. To those who wish to make a closer study of the subject the following books can be recommended : Marsh and Dunn, " Reinforced Concrete " ; Turneaure and Maurer, "Principles of Reinforced Concrete"; Faber and Bowie, " Reinforced Concrete Design " ; Taylor and Thompson, " Plain and Reinforced Concrete " ; Buel and Hill, " Reinforced Concrete Construction"; Morsch, " Concrete Steel Construction"; Rings, " Reinforced Con- crete-- -Theory and Practice." PIPES. Pipes are hooped round so as to prevent bursting unde'r the internal pressure, or being crushed by external pressure as from a load of earth and traffic over. A pipe also, if laid upon the ground or in loose earth, rests somewhat like a beam supported at the ends, and moreover has to be lifted into position. A certain number of longitudinal reinforce- ments will therefore be required. A pipe reinforcement is shown in Fig. 142. GENERALLY. Steel should always be inserted in the face where the pull will come ; thus, in a beam or slab it must be close to the bottom. In a wall built to withstand earth pressure of uniform thickness, unsupported at points, it must be in the face nearest the earth ; but if the wall is buttressed, the portion of the wall between the buttresses is called upon to act as a beam, consequently the reinforcement is inserted on the side furthest from the earth, except in the buttresses, which need their reinforcement nearest the earth. There must be only enough concrete outside the steel to protect it from rusting or fire. In floor or roof slabs of small structures the thickness of concrete below the bottom of the steel should be at least i in., for secondary beams at least 1 1 in., and for main beams at least 2 in. For columns, the thickness of concrete protecting the steel should be at least 2 in., and in important columns 3 in. 148 REINFORCED CONCRETE. 12222 - g/g il i ! 3 | il Ht g I 2| .j i* a | a 1 s~ |'^ | 3 s^^^l -r ? * I ? i i w up H- rjO V '/- |8 Sfe C II ll S TJX -*n ing XKC -*< m^ xtt ir urj^ te -*s -H icj^ r - '"H '-^ x -t^ u-l^ ; |J " eq y AVOJ seqouj saqouj spoH jo spoy saqouj oui saqouj 'UIPTAV jo uieag jo utsdg a o r^oo i^oo o t^oo o Tl-vO 00 OO TfvO 00 O 00 Tj-vO 00 00 rt-O 00 Tj-vO 00 REINFORCED CONCRETE. 149 Ij !> 8 I 8? O * % _ I* 3 1 O * The concrete of both the slabs and of the beams should always be laid as part of the same operation, and if the work must be stopped the point to discontinue should be in the slab at about one-fourth the span from one end. Fig. 107 shows a typical beam sustain- ing floor slabs, from which it will be seen that the beam reinforcement has rods run- ning lengthwise with the beam, part of these rods being bent up about one third of the distance from each end and extending over the supports, while U-shaped bars or stirrups which pass under and around the longitudinal rods up to the top of the beam are provided. The cranked-up bars and the stirrups prevent the diagonal cracks re- sulting from shearing action, and the bars over the supports at the top prevent the cracking of the beam over the support at the ends. Tests should be made of the quality of the steel, which should be in accordance with the British Standard Specification for structural steel. It is just as important to test for quality in steel as in cement, and in many cases very inferior steel has been supplied to casual users, and great risks have been run for want of taking such proper precautions as having a few check tests carried out by independent testing special- ists. The Tests Standing Committee of the Concrete Institute recommends the follow- ing tests for all steelwork for use in re- inforced concrete : (a) The steel shall attain an ultimate tensile strength of not less than 60,000 Ibs. per sq, in, 150 REINFORCED CONCRETE. (b) The steel shall withstand a stress of 34000 Ibs. per sq. in. before showing any appreciable perma- nent set. (c) The contraction of area at fracture shall be not less than 45 per cent. (d) All steel shall stand bending cold to an angle of 180 around a diameter equal to that of the piece tested, without fracturing the skin of the bent portion. (e) The steel shall be free from scabs and flaws. The same authority has issued the following report on " The Testing of Reinforced Concrete Structures on Comple- tion " : "It is frequently specified that test loads should be applied to finished structures of reinforced concrete shortly after completion. It should be recognised, however, that such tests should in no wise reduce the care to be exercised in the supervision of the work by those responsible. Since the test loads are generally applied only to specific parts of the work, such tests do not necessarily prove that the work has been properly executed either in whole or in part. " The test load should not be applied to any part until the expiry of 90 days from the last day of laying the con- crete. " The deflection of beams under a test equal to the full working load for which the beams were designed should not exceed i/i,oooth of the span. " In order to impose the full load upon a floor or roof beam under test the two bays of floor or roof adjoining require to be loaded all over, otherwise a considerable por- tion of the load is transmitted to the adjoining beams and the full load does not come upon the beam under test. " Not more than the superimposed load for which the beam has been designed, plus 50 per cent., should be applied as a test load. " When test loads are applied the materials used for loading should be put on in such a manner that no arching action whatever can take place, otherwise incorrect results will be obtained. " If systematic and thorough supervision be given by the professional adviser during course of construction the REINFORCED CONCRETE. 151 application of test loads to the finished structure is not so necessary. " Test cubes, if kept in an even temperature, which should be the same as that specified for cement briquettes, form a means of gauging under standard conditions the resistance to thrusting, and cubes kept in the open air will give the values for the concrete in actual practice. The results of these two sets of tests will be helpful in deter- mining at what age the work is strong enough to sustain the loads." The Concrete Institute some time ago investigated the question of whether rusting of steel takes place when covered by concrete, and collected a good deal of informa- tion giving the results of experience and examination. As a result of these observations and investigations the fol- lowing conclusions have been drawn : " Reinforced concrete will last as long as plain concrete in any situation provided that certain special precautions are taken during its con- struction. The precautions to be taken are as follows : " Concrete. The materials (cement, sand, and stone) must be of good quality. They must be most carefully and thoroughly mixed and scientifically proportioned, so as to be practically waterproof and airproof. The mixture must be fairly wet and must be well punned into position so as to minimise voids. The aggregate should be- as non-porous as possible, and any aggregate which is known to have a chemical action on steel should be avoided. The aggregate should all pass through a f-inch mesh. The concrete covering should in no case be less than J inch, and it is suggested that if round or square bars be used the covering should not be less than the diameter of the bar. In struc- tures exposed to the action of water or damp air the thick- ness of covering should be increased at least 50 per cent., or the size of the aggregate should be reduced so as to ensure a dense skin. In the case of structures exposed to very severe conditions, the concrete might be covered with some impervious coating as an extra precaution. " Steel. The reinforcement should be so arranged that there shall be sufficient space between one piece and its neighbour to allow the concrete to pass and to completely surround every part of the steel. All steel should be firmly 152 REINFORCED CONCRETE. supported during the ramming of the concrete, so as to avoid displacement. It should not be oiled or painted, and thick rust should be scraped and brushed off before placing. *' General. The scantling of the various members of the structures should be sufficient to prevent excessive deflec- tion. If electric mains arc laid down, very great care must be taken that no current is allowed to pass through the reinforced concrete. Fresh water should be used in mixing, and aggregates charged with salt should be washed. " These recommendations have regard only to the pre- vention of the corrosion of steel and not to fire-resistance or any other property of reinforced concrete." Due to an escape of electric current from the mains supplying the electric lamps and electric cranes on some jetties on docks at Southampton, it was found that considerable deterioration of the concrete had taken place by electrolytic action. The recommendations of the Concrete Institute, above referred to, will prevent any such deleterious action taking place in future if they are observed, but at the same time, it would be undesirable to permit the possibility of such action, and where electric mains are in conjunction with reinforced concrete a test should be conducted by making a metallic connection with the earth or water to ascertain if there is any difference in potential ; if there is, then there is an escape of current which should be put right at once. 153 EXAMPLES OF^THE USES OF CONCRETE. IN classifying the following notes on the many uses to which concrete is now put we have first dealt with the more ordinary applications in building work, and have proceeded in the order in which such structures are erected, commencing with the foundations, and going on to treat of the walls and floors, finishings and appurtenances. Completed structures are then described and illustrated, and finally special applications dealt with. FOUNDATIONS. One of the best known uses to which concrete is put in the country in connection with either the home or the farm is the con- struction of foundations and walls. Every wall should have a proper foundation that is, the base should be wider than the wall it carries, so as to press lightly upon the ground by distributing the weight upon a larger area. Further- more, the widening of the base increases the stability of the wall. The foundation should extend below the frost line, so that the excavation should be at least 2 ft. deep. Pig. 1 08 shows a form of reinforcement for a column foundation carrying a heavy load. The vertical rods in the column are turned round at the ends or bear against a metal plate or series of plates so as to distribute the pressure. In the foundation block underneath the bottom of the post or column rods are placed lattice- wise as shown, while stirrups are passed round them and hooked up into the concrete. Fig. 109 shows another reinforced concrete foundation. In this case the loads are heavy, and the subsoil weak, so that the whole area has to be brought into play, and the foundation is therefore made in the form of a raft floating upon the soil. The construction in such a case is exactly that of an inverted floor, the upward pressure of the soil being equivalent to the load upon a floor, and the downward pressure of the column being equivalent to the upward pressure of the supports as in the case of a floor. Fig. 110 shows a foundation to carry boilers. Here the resemblance to ordinary floor construction reversed is still closer, because the beams project above the raft instead of below. In the majority of cases, however, ribs on the upper surface are not permissible. The foundations of buildings consist in many cases of concrete piles. These piles may be constructed of plain or reinforced concrete, and can be built in situ or moulded and put in place. In the former 154 FOUNDATIONS. +L i i tJUppf! | | T" T" T- T*r f ^-f^T^Y (^ ^" J ^~ -~j ~t" 11 ^ttT^^^Kf ^ -*'~ T j-i T-WT ^Hr^*^ " ! iT^Xtl^^tTTT^ri T VPJ4^ f 7 -fc -F-r^ -7f-| -IT r-i -i + r . *" f ' t -'- 1- -0 JCT10N ON A~ Fig. 108. Column Foundation in Reinforced Concrete. ^ U-=H M=r 4=1-1= PL/IN Of^ VMDERS/DE SlCTJOfl A-A Fig. 109. Raft Foundation in Reinforced Concrete. FOUNDATIONS. 155 method steel sheaths like a section of steel pipe are driven into the ground, and concrete is poured down the centre of them with, perhaps, a skeleton framework of steel rods put in also to reinforce it, and the tube is then withdrawn, leaving the concrete SECTION CT U U U PLAN U LJ U in the earth, the friction of which against the sides may be sufficient to give the neces- sary resistance, or the concrete may be resting on a hard stratum below. With the moulded type of pile, however, these are always reinforced so that they can be handled, and they are pitched and driven into place, the driving being effected by means of an ordinary pile- driver, by which an ordinary ram is dropped or drives against the head of she pile and jars it into place. The machines consist of either of those in which a weight is hoisted up and dropped down again, or of a steam- hammer, which raises the weight up and down in the manner of a piston. The piles Fig. 110. Raft Foundation in Reinforced Concrete Fig. 111. Reinforced Concrete Pile. 156 FOUNDATIONS. PL/IN Fig. 112. Pile Foundation in Reinforced Concrete. may also be driven by means of a jet of water forced under pressure through a pipe passing down the centre, the water making its way out at the opening of the pile and blowing the stones away and allowing the pile to sink by its own weight or by moderate driving. This process is particularly applicable to sandy and muddy substrata. Fig-. 1 1 1 shows an arrangement for the reinforcement of a pile. Of course this skeleton, made of wire and rods, is embedded in concrete. There are various methods of arranging the reinforcement, similar to those of a post or column, rods being placed longitudinally through the length, and wrapped round with hoops or spiral winding of smaller rods. Fig". 112 shows a foundation resting upon concrete piles, as the soil in this case is not strong- enough to sustain a heavy load. In 'constructing piers for the new bridge over the River Foyle a new method of sinking the foundations was adopted. A reinforced concrete caisson was used instead of a steel one. It consisted of a number of super-imposed sections, the bottom of which had a cutting- edge. These sections were left for about four weeks to harden, when they were lifted bodily by a crane and lowered into place, each separate section being kept in position by a series of vertical rods, which ex- tended from the lowest section to above the surface of the water, thus ensuring each section resting plumb on the one below. The weight of each section was from 7 to 8 tons, and its form is shown in Figs. 113 and 1 14. In order to make the joints between the sections satisfactory a small groove was made in the upper surface of each, while the FOUNDATIONS. 157 bottom of each section was provided with a small wedge-shaped projection. A roll of cement mortar encased in linen was placed in each groove, and the projection of the section above dug into the soft mortar making a perfectly watertight joint. The cost of these rein- forced concrete caissons worked out at about half thai of steel caissons to do the same work. A jetty was con- structed at Irlam Lock on the Manchester Ship Canal, with reinforced concrete caissons which were moulded on land and Fig. 113. Caisson for new bridge, River Foyle, Strabane and Letterkenny Railway. lifted into place by a crane, and built up in sections placed one upon the other very much as bridge piers. These cais- sons had a timber topping to form the floor of the jetty. Some of the cais- sons weighed a great deal, the heaviest being 107 tons. Similar applications of reinforced concrete to harbour and dock con- struction have been car- ried out in Holland. For the quay walls at Ymui- den reinforced concrete cylinders were previously prepared, and subsequent- ly driven into the sandy bottom by means of water jets. After these had been driven to a sufficient depth, a heavy superstructure of Fig. 114. Caisson for new bridge, River Foyle, re inforced concrete Strabane and Letterkenny Railway. was fixed on top of them. 158 FOUNDATIONS. Fig. 115. Windmill Foundation. In constructing the quay walls at Rotterdam, huge hollo\v caissons of reinforced concrete were prepared in a dry dock, these caissons measuring 132 ft. in length, 33 ft. in height, and 23 ft. in width, the wall thickness being from 6 ins. to 14 ins. They were towed afloat to their places and sunk to the bottom (which had been previously levelled) by filling them with water, after which they were filled with concrete and sand. Upon the caissons, above the water level, are placed concrete blocks. The rotting of wooden wind- mill foundations causes consider- able danger, ^nd concrete car- ried by a metal framework is ; n fi n j te iy better for the purpose. Such as shown in Figs. 115 and 116 A suitable mixture for con- crete for the bed of an engine would be four p&rts coarse ma- terial, two parts sand to one of cement. The erection of the engine could be commenced as is hard WALLS. 159 set, but it would not be advisable to commence to run it in less than a month to six weeks, this period varying with local conditions. WALLS. Concrete walls may be either hollow or solid, the latter form being mostly adopted in the case of a boundary wall or a retaining wall, whereas the hollow wall is more used for walls of buildings. Concrete walls are stronger than brick walls of the same thickness. A concrete \\all may be built either in separate moulded parts in the shape of blocks put together as brickwork or masonry, or it may be cast in situ. Care should be taken in building walls that they are plumb, and they should be allowed to harden for two or three weeks before any superstructure is built upon them. Earth should not be filled in against a concrete wail for three or four weeks unless the shuttering on the side opposite to the earth is kept in place. Door or window frames should be put in position and the wall built round them. Cellar walls are usually from 10 in. to 12 in. thick for a super- structure of timber frame-work, and n in. to 16 in. or 20 in. thick to sustain a brick superstructure i.e., about 2 in. wider than the brick wall, for cotivenience in laying out the brickwork. We have before referred to the desirability of avoiding cracks due to-."expansion and contraction under changes of temperature by pro- viding expansion joints or by the use of reinforcement. , Figs. 1 6 to 20, on pages 58 to 60, show forms for constructing ordinary solid concrete walls. In Fig. 16 it will be noticed that 2 in. by 4 in. props are placed against the 2 in. by f in. upright studs so as to keep the shuttering rigid and upright. The diagram shows the footings to such a wall, and also represents on the right a solid con- crete retaining wall built against a bank of earth, the shuttering being placed only upon one side. Fig. 19 shows a type of form which is raised as the wall goes up. The bottom set of bolts which hold the shuttering the right distance apart rests upon the completed wall, the lower part of the former over- lapping the concrete as shown, this tending to keep the wall plumb. We here note that the bolts should be greased each time such a form is used, otherwise it will be difficult to remove them after the concrete has set, owing to the great strength of adhesion between concrete and steel. The holes left by withdrawing the bolts may be filled after- wards with sand and Portland Cement mortar of the same proportion as the sand and Portland Cement mortar of the concrete of which the body of the wall is built. Where there is not much strain upon a wall it is well to build il hollow. Fig. 18 shows a form for the construction of a hollow wall in situ. The core is built in sections about 2 ft. high and rests on the galvanised iron ties which bond the inner and outer faces together. These ties should be about 2 in. broad by J in. thick, and should be turned up i in. at each end, and be long enough to extend halfway through each wall. These should be laid across the wall, spaced 3 ft. 160 WALLS, Fig. 117. Ttetainintj Wall at 13 irken heart Gasworks. apart, every time the core form is raised. The ends, top and bottom of such a wall should be filled for 6 in., to enclose the air space, but the latter should be well ventilated by ventilating bricks built in at points. Another plan is to use collapsible core-boxes which run to the height of the finished wall. After the wall has been brought to its full height and becomes set the core-boxes are collapsed and lifted out. For the keeping of -earth and other materials in place what might almost be called a dam for earth is built. All materials, if not sloped at a slight angle less than their angle of repose, are liable to slide forward and exert pressure, and this slipping of the material is prevented by building retaining walls capable of resisting this thrust. Reinforced concrete retaining walls are very much more economical than brick or stone retaining walls, for the overturning action is resisted by extended outer bases, the tendency to crack which is resisted by the embedded steel, whereas brick and stone walls can only resist the pressure by the dead weight in them. In reinforced concrete walls the earth filling is often made to sustain itself by providing the weight to prevent overturning, whereas in walls of other materials the weight has to be provided by a large mass of other sub- stance. Fig. 1-17 shows such a wall constructed at Birkenhead, and WALLS. 16! Fig. 1 18 illustrates another at Salford. It will be seen that the latter wall is reinforced with expanded metal. Retaining walls are often required in the basements of buildings to sustain the earth outside ; the retaining wall at Salford is of that character, and forms the area around the /V*/Ojtpastdd Steel. J /U - ?.' Fig. 118. Retaining wall, Salford Public Baths. 162 WALLS. Fig. 119. Fence wall, Atlantic Avenue Terminal, New York. building, standing clear of the basement. The walls of basements, however, often consist of these retaining- walls themselves, the earth being close up on the outside. Concrete walls round gardens may be made of poor proportions outside, with insufficient sand to fill the voids in the coarse material, say 7 or 8 round ballast stones or large-sized coke-breeze or clinker to i of Portland Cement, so as to be very rough. Roughness, however, does Fig. 120. Fence wall, 1 mile in length, from Wabash River Bridf/c, WALLS. 163 ELEVATION. N 9 Expanded Steel U --- /?'-^" ___ J PLAN AT A A. CROSS SECTION. Fig. 121. Cemetery boundary wall. West Hartlepool. 164 WALLS. fciit Fig. 122. Gate and at Buntingford, Herts. not mean that the wall should be porous and not waterproof ; the interior of the walls should be solid and compact. If a large-sized coarse material is used, the stones not beir g crushed but roughly deposited in the forms, by simply wetting these beforehand and tamping only in the centre of the wall, it will be found when the forms are removed that the concrete has a very rough surface with plenty of holes in it for a depth of about an inch, but the interior of the wall will be solid. Figs. 117 to 124 show reinforced concrete boundary walls, examples which may serve to remove misgivings concerning the suit- ability of reinforced concrete for long monolithic walls. The reinforced concrete fence wall shown in Fig. 119 is about 3 inches thick, with posts every 10 feet, and a heavy concrete curb. The panels are rectangular slabs with a fluted outer surface formed by using sheets of commercial corrugated iron for the backing of the wooden moulds in which they were cast. The top of the slab is fprmed as shown with a rounded horizontal rail, somewhat like a hand- WALLS. 165 Fig. 123. Boundary wall to Bowling Green, Bilton. rail. Each slab was reinforced with f in. diameter steel rods placed vertically 18 in. apart, and with four horizontal lines of 3 in. and f in. diameter rods. Vertical concrete posts, rectangular in cross section, 7 in. square, each reinforced vertically with four ^-in. steel rods, were cast in place on the concrete coping. Slots in opposite sides of the posts hold the ends of the slabs in position, the slabs being cast in place after the posts have been thoroughly set. The slab is anchored to the post by projecting ends of horizontal rods, and the posts were anchored to the curb girder by two |-in. vertical projecting rods. Fig". 120 shows another type of fence wall which is about 4 feet high, and was built in sections of about 20 feet in length ; the construc- tion is clear from the view. Fig". 121 shows an external cemetery boundary wall at West Hartlepool. The wall, as will be seen from the view, is stiffened by buttresses ag-ainst the pressure of wind, and it is weighted down as it were by these buttresses being embedded in the earth, and having a heel or foundation plate. Fig. 122 is a monolithic reinforced concrete wall. Fig. 123 is a wall built of hollow concrete blocks. Fig. 124 shows a section of a boundary wan* at Borstal Institution, Feltham, constructed for the Prison Commissioners. It is 7,500 ft. long, and constructed of hollow concrete blocks 45 in. thick, with piers at intervals. The height is 7 ft. 7^ in. to the top of the coping, and 9 ft. 9 in. to the top of the barbed wire which is threaded through the 166 WALLS. Fig 124. Boundary watt at Borstal Institution, Feltham. PIERS & POSTS. 167 eyes shown at the top of the upright posts. These are placed at intervals of 13 ft. 8 in., and measure 12 in. by 9 in. by 12 ft. io in. over all. These piers are rebated to receive the concrete blocks, and are set 2 ft. 6 in. in the ground on a bed of concrete i ft. 9 in. square by i ft. thick. In the. sides of the rebates of the posts is embedded steel wire mesh so as to fit into the bed joints of the blocks, which are also reinforced with steel wire netting. The wall is self-supporting be- tween piers, and does not require a continuous foundation. The blocks are 285 in. long, 9 in. wide, and 43 in. thick, with recessed end joints. Each block has two cavities, and they were made two at a time in the moulding machine. Six men made and stacked 400 of these blocks per working day of 10 hours, and one bricklayer and two labourers erected in each day 16 ft. by 8 ft. of wall, i pier, and 2 ft. of founda- tion blocks. The proportions used for these blocks were 4 parts clean -in. gravel to i of Portland Cement. PIERS AND POSTS. Piers and posts in reinforced concrete can be conveniently built as follows : An excavation should be carried below the frost level, say 2 ft. sq., and filled in with concrete to within 6 in. of the surface of the ground. A form should be built such as that shown in Fig. 125, say 12 in. sq. Four steel bars 5 in. diameter should be placed vertically in this form, but 2 in. away from the corners, and bound round at intervals of a foot with loops of wire ^ in. in diameter, Fig. 125. It'orm for post. 168 FLOORS, INTERIOR PAVING & ROOFS. these loops being tied to the steel rods with fine wire. Every 2 ft. a short piece of | in. or \ in. wire may be tied to the vertical rods as shown at " A " in Fig-. 125, so as to project against the form and hold the steel in place. Concrete, which should be of medium consistency, not very dry nor yet wet, should now be poured into the form and well rammed therein. A long paddle made like an oar should be worked against the sides of the form to drive out bubbles of air and give the outside o.f the post a good appearance. FLOORS, INTERIOR PAVING AND ROOFS. A basement floor resting upon the earth may be laid without foundations, except in places where there is a danger of frost getting into the ground below the floor. In such cases a dry stone foundation is desirable, as advised for external garden paths or walls. A base of concrete, proportioned i : 2i| : 5, should be first spread over the under-surface, which must be made fairly level, to a depth of 3 or 4 in. This should then be graded with a straight-edge resting on battens placed about 12 in. apart. As soon as this is done the battens are withdrawn and the holes they leave filled up with concrete. No finishing coat is needed unless the floor is to have excessive wear. The surface, however, must be trowelled over as described for paving. If a hard-wearing surface is required, this may be given by a finishing coat similar to that described for external paths. Joints should be made about every 12 ft., and if the surface is more than 50 ft. long, or is subject to extreme temperatures, a sectional area of steel equal to .005 of the sectional area of concrete, in the form of meshwork, is introduced to take up the stresses caused by expansion and contraction. For the surface of such floors, or for concrete paving laid in situ, it is well to use a Portland Cement which sets in three to five hours. For the best work the surface coat should be made of fine sharp coarse material and Portland Cement proportioned 2 to i, and laid i in. to 2 in. thickness. The best wearing surface for pavements is made of 3 parts clean granite chippings, capable of passing through a f-in. mesh sieve, mixed with i part of Portland Cement. Slag chippings are sometimes used instead of granite, but as they may contain sulphur the latter are distinctly preferable. The floors of barns and stables are laid in the same manner as paths, the thickness of the porous foundation being 6 in. to 12 in., the base 3 in. to 5 in., and the surface coat i in. to i\ in. thick. The surface should be roughened and grooved in blocks about 6 in. sq. to prevent the animals slipping, and sufficient slope should be given to the floor to remove liquids to drains placed at convenient intervals, these drains consisting either of gutters or pipes laid in the floor, and leading to a manure pit. If pipes are used they should be bedded in the concrete, the joints put together with Portland Cement mortar, and care should be taken to give them sufficient slope to flush properly. The tops are covered with perforated lids and it is preferable also to form sump-pits below the concrete so as to prevent any manure, straw, etc., INTERIOR STEPS & STAIRS. 169 from choking the drains ; the lids should be about | in. below the level of the floor. Carriage ways, stable yards, and coach-house floors, when made of concrete, should be divided into 6-in. squares to give a foothold. The design and construction of reinforced concrete floors above ground has been dealt with in earlier sections of this book. A concrete roof requires some form of reinforcement, and metal meshwork is very suitable for the purpose. If the ceiling is to be level the roof may be calculated as a flat floor slab ; if curved, it will be desirable to call in an architect or engineer. INTERIOR STEPS 3 AND STAIRS. Concrete can be advantageously used in the construction of steps, particularly in damp places such as cellars, areas, etc. Fig. 126 shows a flight of concrete stairs and Fig. 127"* shows the construction. The stringers are cast in situ in forms, being designed as inclined beams. There is a lip or projection at_ the bottom to support the steps. The reinforce- ment should consist in Fig. 126. Flight of internal stairs. the ordinary way of JTEPW/WAf Fig. 127. Construction of internal stairs 170 INTERIOR STEPS & STAIRS. two f-in. bars about i| in. from the underside, and one bar of similar size at the top, these being connected to- gether by 5-in. wires wound diagonally over these bars as shown in Fig. 1-27. The amount of reinforcing, however, should really depend upon the depth and pitch of the stairs and the weight they have to carry. The steps are cast in moulds as shown in Fig-. I2 - ; an( i arc lodged in the stringers as shown. These steps have a small notch in the lower edge so as to rest against the upper corner of the stair below, and they arc reinforced with three rods as shown. \Yhen the steps have been put in place the whole is chipped over with a small pickaxe, and a finishing coat, proportioned i part Portland Cement to i part sand or granite chippings, is put over the whole flight of steps so as to bond the whole together. Stairs, however, may be con- structed monolithic on a properly built-up form, the stringers being rein- forced as inclined beams, and the treads being reinforced across and longitudinally as shown in Fig. 129. The size of the reinforcement is usually about -5n. rods in the corners of each step threaded with |-in. rods bent to the shape of the steps, spaced about 2 ft. apart; the risers arc moulded between two vertical forms, one above and the other below. The treads do not need an upper form as they are horizontal ; the thick- ness of such steps should be about 3 in- Fig. 130 shows a flight of con- crete stairs, built by ordinary estate workmen, and Fig. 131 refers to a larger example of a winding staircase of reinforced concrete. Spiral staircases are also often constructed of reinforced concrete. An external one built in Holland is illustrated in Fig. 128. Fig. 128. External staircase. INTERIOR STEPS & STAIRS. 171 Fig. 131. Staircase, Mclntyre Building, Salt Lake City. 172 PATHS & PAVEMENTS. In surfacing steps and landings, if the sand is not absolutely clean and the con- crete is mixed rather wet, the clay or loam will come to the surface and injure the same so that it wears off easily and leaves an uneven tread. For improving the surface of such floors, landings, and steps, sili- cate of soda is often applied by means of a brush to the surface of the concrete when clean. Fig. 129. Reinforced concrete stairs. PATHS AND PAVEMENTS. In forming concrete paths and pavements as much care should be taken with the foundations as with the path or paving itself. The foundations should be about 4 in. to 6 in. deep. Where there is a porous soil and a. rainy climate the foundations should be deeper, at least 2 in. or 3 in. more. If the soil is clay, blind drains, coarse gravel or pipes should be laid at the bottom of the excavation to carry off any water that may accumulate. Concrete paths are often ruined by water freezing in the foundation and ex- panding and forcing up the top layer. A shallow trench should be excavated to the re- quired depth, about 3 in. wider on each side than the proposed path. This should then be fi 1 1 e d in with broken stone, gravel, or cinders, to a height 4 in. short of the finished surface, and well wetted and tamped in layers, so that when complete it is even and Fig. 130. Concrete stairs in laundry at Great firrrt Kllf -,,- Confield (with wooden treads). hrm > but P orous - PATHS & PAVEMENTS. 173 Battens measuring about 2 in. by 4 in., preferably dressed on the inside edge and quite straight, are now laid on top of this foundation, the correct distance apart, so as to form the inner and outer edges of the path. For wide paths, the space between the battens should be divided into equal sections not larger than 6 ft. square, putting 2 in. by 4 in. battens crosswise and in the centre as shown in Fig. 132. This ivill make every alternate space the size desired. These alternate spaces are filled to a depth of 3 in. or 4 in. with concrete proportioned i part Portland Cement, 2 parts clean coarse sand, and 4 parts broken stone or shingle. It should be tamped in position, and as soon as the concrete has set the crossways and centre scantlings may be removed, a piece of tarred paper or thin strips of lath being placed between, and the other squares filled with concrete as before. The surface should have a slight inclination of about in. slope each way from the centre to every foot of width of the path to allow the water to run off on either side. A finishing coat of about i in. thick, composed of i part Portland Cement to 2 parts of clean sand or evenly crushed shingle, granite or stone should now be spread all over the concrete before it has become thoroughly set, and the surface rendered smooth by a screed or straight- edge run over the battens, and finally by a wooden float, and a groove NOTE. fO#W PLACfD fVf! SLCKXS a? oss SECTION L -* --^-L,..-. J PIA/V : < -> X ~ ;V'-' \" V -\ : GUf*PB\"\ Fig. 132. Constructing wide concrete Fig. 133. Constructing narrow footpath. concrete footpath. 174 PATHS & PAVEMENTS. Fig. 134. Footpath, South Bethlehem. made with one of the tools referred to on page 101 exactly over the joints between the concrete layer below, so as to bevel the edges of all blocks. The finishing coat should not be trowelled too much nor until it has begun to set, otherwise the Portland Cement will be brought to the surface. To give a glassy finish, men often keep working the surface with their trowels over and over again for some time, sprinkling it with water as well. This should not be done, as it breaks up the initial set of the cement, and renders the surface friable and unable to resist wear. A single trowelling must suffice, even if the appearance is not so good as that given by repeated trowelling. Neat Portland Cement should not be " dusted " over the top surface while being trowelled, as is done by some workmen, as it will only cause crazing. It is important that the foundation should be quite green i.e., that the work should be done on the same day that the finishing coat is applied otherwise there is a danger of this not thoroughly bonding with it. Care should be taken in laying the finishing coat that no sand or dirt be allowed to come upon the lower coat, otherwise a proper union will not be obtained. No section should be left partially completed to be finished with the next batch on the same or the following day. The finished path should be carefully protected from dust, dirt, currents of air, and the sun, as well as from all traffic of men or animals, during the process of setting and hardening. For this purpose it should be covered as soon as set with sand, straw, sawdust, or other similar materials, and 'kept thoroughly wet. In breweries, laundries, stables, dairies, urinals, sewers, etc., no liquid but water touch the moist concrete till it is thoroughly matured. All CONCRETE FOR ROADS. 175 concrete paving" should receive a wetting about once a week for three months at least, and preferably longer. Where paths are made of a narrower width than that illustrated, the path may be formed of a single slab in width, and in this case every alternate section should first be concreted and the section between them filled in afterwards. Fig. 133 shows such a single-slab path. The edges of the paths are rounded with the tools shown in I'ig"- 53 on P a " e 101. ^ an y indentations are required in the path to give a foothold, this may be done with a roller as shown in Fig. 61 on page 102. CONCRETE FOR ROADS. Kerbs may also be formed in concrete, with a foundation ot broken stone, gravel or cinders without the admixture of any cement, or of concrete as shown in Fig. 135. The manner of executing these kerbs follows very much on the lines of the method adopted for paving, and Figs. 135 and 136 clearly show the kerbs and the form for same. The kerbs may be 4 in. to 7 in. wide at the top, and 5 in. to 18 in. at the bottom, with a face 6 in. to 7 in. above the gutter. The concrete base or foundation should be 5 in. to 8 in. thick ; the broken stone foundation should be 12 in. thick. The concrete kerbing, like the paving, should be built in sec- tions 6 ft. to 8 ft. long, separated each from the other and from the path by tar paper, laths or a cut joint, in the same way as the walk is divided into blocks, so as to avoid trouble from expansion and contraction. Fig. 136 shows how stakes are driven and boards inserted to form the under layer of concrete, the f-in. board being removed as soon as the kerb has sufficiently set to stand its own weight without bulging, and the finishing coat filled in the space and over the top of the kerb. The concrete foundation may be proportioned i Portland Cement to I'PUNK Fig. 135. Concrete kerb. Fig. 136. .Form /or concrete fcer'b, 176 CONCRETE FOR ROADS. 3 of sand and 6 larger aggregate. The kerb itself should be propor- tioned i Portland Cement, 23 sand and 5 coarse material, while the finishing coat is composed the same as for paths. Where kerbs have to sustain heavy traffic the edges should be fitted with angle steel corners to take the abrasion of wheels. By such means granite kerbs can be dispensed with. In all cases the edge of the kerb should be bevelled or rounded to prevent chipping. Gutters may be formed in conjunction with the kerbs 16 in. to 20 in. wide, and 6 in. to 9 in. thick. They are also formed with i : 25 : 5 concrete and a finishing coat of fin-a material, as for kerbs and paths. Fig". 137 shows a form of concrete kerb and channel block for roads. This design obtains a result which could only be done in stone at an entirely prohibitive cost. It will be noted that the kerb has a projec- tion upon the outer face upon which the channel block, which is also formed with a projection, rests ; this support and the joggle joints keep the blocks in position and preserve a rigid length for either paved streets or macadam roads. The cross section of the blocks, it will be noticed, also has the sides battered or sloped. This gives a wider bed upon which the blocks rest, and also they leave the mould easier when made in this way. The channel has a dishing | in. deep at the centre on the upper surface. Concrete for the construction of roads to serve as a wearing surface as well as a foundation has been used in rather a tentative way. In towns, nowadays, a great deal of the traffic is by automobiles for which nothing can be better than a concrete road. The motor- racing' track at Brooklands is laid with concrete. For the reason that the work has not been properly constructed it does not appear to be favoured in Great Britain by borough surveyors except for forming the foundations of roads for a wearing surface of wood blocks. In the United States of America, however, a great many roads with concrete wearing surfaces have been constructed, and have given satisfaction. At Richmond, Ind., some of the earliest concrete roads were constructed, the first being in 1896, which is now nearly 15 years old, and it has been in continual service for the whole of that period without having cost one farthing for repairs. Extreme care was taken in the construction of this road even in all the seemingly minor details, the proverb which appears to have governed its builders being that " perfection seems to be made up of trifles, but perfection is no trifle." The natural subsoil being gravel, there was no founda- tion of rammed hard core as usually provided. The concrete was proportioned i part cement, 2 parts sand, and 5 parts coarse material, and was laid 5 in. thick after rolling, with a top surface i in. thick, proportioned i part cement to 2 parts sand. The wearing surface was cut into blocks about 5 ft. square, and the surface indented with a roller such as shown in Fig. 61. In subsequent work the roadways have been cut into blocks 8 to 10 ft. square, and in some cases 30 to 40 ft. square. The joints between the blocks, both transverse and longi- tudinal, were i in. wide and filled with paving pitch. Experience has shown that this is not an advantage because the edges of the joints get CONCRETE FOR ROADS. 177 Concrete feerb ond channel. ft ins block. Channel "block. Fig. 137. 178 CONCRETE FOR ROADS. I chipped in wearing, and so the blocks are made as large as possible in order to reduce the number of joints, and the joints are as thin as can be made. Experience has shown that blocks 10 to 15 ft. square are about as large as can be employed without developing temperature cracks, 1 but as has been referred to elsewhere, by the provision of reinforcements these temperature cracks can be prevented. Grooves or projections on -the surface are objectionable for the same reason as too many joints. They result in the concrete becoming chipped by the hoofs of horses. Moreover, they catch and collect the dirt, so interfering with the work of cleaning the pavements. Sufficient foothold can be given by the indentation of the surface, and it is also contended that sufficient foothold is given by merely bringing the concrete to a face with a cork or wood float which renders it rough and gritty. A surface coating of i part of cement to 2 parts of coarse- grained sand is best. For roads the concrete should be mixed wet and well rammed in place ; the joints are cut through the concrete and merely filled with sand, and before the concrete is finally set a top surface coating is applied, the joints therein being directly over those made in the concrete below ; these joints, however, should be made with a fine jointing tool such as illustrated in Fig. 52, so as to leave as thin a joint as possible. For very heavy traffic, 6 in. of concrete with a 2 in. top surface might be advisable. Concrete roads have also been made without a top surface of finer material ; in this case, however, the concrete should be made with small stones and somewhat richer in cement, say, 1:2:4, with |-in. aggregate. If there is a large stone on the surface there is a tendency for one edge to wear loose, so providing sufficient leverage to tear the remainder of the stone from the concrete. Macadam, the great engineer road builder, after whom were named macadamised roads, used to state that if one could get stones broken into cubes of uniform size of about i in. square, and once could get them laid, one would secure the ideal road. It is difficult to main-tain a road composed of irregularly shaped fragments of irregu- lar size where there is rapidly moving traffic. Bearing this in mind a rather novel form of road has been recently constructed in America. Irregularly shaped stones that are objectionable for macadam roads are taken and squared as it were by the use of Portland Cement. 2 in. cubes of concrete, with these stones as the coarse material, were made by a machine similar to those used for moulding bricks, a number of cubes being cast all at one operation. The cubes were laid evenly on an ordi- nary foundation of stone or gravel, as would be employed for the founda- tion of a macadam road. After the foundation was made firm by the use of a steam roller, gravel was distributed over it and rolled into place to give proper curvature to the road and provide a smooth bed on which the cubes were then laid, and a small amount of somewhat fine somewhat loamy gravel spread and worked in with a broom. A heavy steam roller (10 to iz tons) was then passed over the whole of the surface forcing the cubes to take a proper bearing on the supporting gravel base. The surface was then watered and more fine loamy gravel spread over JOINTS IN DRAINS. 179 the top and brushed in, and again thoroughly rolled. This type of road should be extremely serviceable. In grouting granite setts laid as usual on a concrete bed, slow- setting Portland Cement should be used mixed i part to i part of sand, and fine sand brushed in on top in the usual manner. An experiment was made by running a steam trolley with a 2-ton load, over portions of granite setts grouted with mortar made of quick, medium, and slow setting cements respectively. The initial set of the quick cement was 3 minutes, the medium 20 minutes, and the slow 2 hours ; the final set of the quick was 30 minutes, the medium 2 hours, and the slow 6 hours. The trolley had a total of 6 tons on its four wheels, i.e., 13 tons on each, and it was run over some pieces of wood 3 in. diameter to create a bumping action. The joints of the quick-setting cement were broken wherever the wheels went, this cement having evidently been killed ; the portion done with the medium-setting cement showed a crack or two, while the slow-setting stood well. The time that elapsed from the time of gauging to the time of test was 100 hours. JOINTS IN DRAINS. The customary method of jointing stoneware and. cement drain pipes is to use cement, but mistakes are often made in this work. It should be remembered that neat cement should not be used, but a mixture of i part of cement to i part of sand. The best plan is to fill the whole of the space in the joint with cement mortar without putting in any gaskin or other material, though one often finds it required that the socket should be practically filled with gaskin. The inside of the socket, and the exterior of the spigot should not be glazed, and care should be paid to this point ; if the glaze has run over the surface to which the cement has to stick, then this surface should be chipped. The gaskin is particularly objectionable, for, firstly it allows some amount of play in the pipes, which allows them to sag, and thus breaks the seal between the pipe and the joints; secondly, because it allows of inferior workmen making the joints ; and, thirdly, because the joints will not stand any pressure if subjected to vibration. The most important point at which the joint should be perfect is between the end of the spigot and the bottom of the socket which cannot be obtained if gaskin is used. Cement mortar joints should be absolutely rigid, and drains should be laid on a foun- dation in which there is no possibility of yielding or uneven settlement. Sometimes failures result from various other causes. Another cause may be the uneven expansion of the concrete bed, especially if made of cement with free lime in it, or ground or lias lime, and if it is not of equal thickness, as, for instance, when deep holes are filled up in the bottom of a trench ; such expansion lifts the pipes off their bed. This can be overcome by seeing that the foundation is of even thickness, and that the concrete is made with good Portland Cement. The pipes are generally encased in concrete for their protection- against the material filled into the trench, and as an additional safe- 180 MANHOLES & CESSPOOLS. guard against internal pressure. Often a pipe line is damaged by uneven or careless filling of the trench, or by workmen knocking the pipes, or by debris falling into the excavation ; this in great part can be overcome by encasing the drain carefully in cement concrete. Often failure occurs by testing, or filling in the trench before, the cement is thoroughly hard ; the remedy for this is to use a quick-setting cement, and if the cement manufacturers are informed of the purpose for which the cement is required, there will be no difficulty in having a special quality supplied suitable for jointing drain pipes, by the use of which the pipes may be quickly tested after the joints have been made and the trench also quickly filled in. The failure of joints in a test may, of course, result either from an improper form of joint, or from the insufficient adhesion of the cement mortar to the pipe by reason of the surface being glazed as before mentioned. MANHOLES AND CESSPOOLS. Fig. 138 shows a reinforced concrete manhole used in drains for the main line of the Midland and Great Northern Joint Railway. The manhole is moulded, and merely set in position in the ground. Fig. 138. Manhole, Midland and Great Northern Joint Railway. MANHOLES & CESSPOOLS. 181 fRSHA/R Wi E T. 3' ' '" ' BZHCH/HG T^^" ^X^^. .^ I " \/^"' rosfwn '-x&;s^ Tra*vere Section. Sectional Plan. Fig. 189. A concrete manhole. iE Section. Fig. 140. ^ concrete manhole cover. 182 PIPES, MAINS, CONDUITS & SEWERS. ] - -. JB '^ ^^^^^^^ ^ A s ' 1 v f-vjf, v.M . . '". > D D D D D -Vy '.*"""' D D Q Q D D li'.r: :t* ; . sf?. -? * D a a a a Q H Q p B Qn n n n ?.*> o'^ 4. >> s:V, rfV Q a a Q a Q * ' ;-<:>-' B O D D .\\; :LV~- a a Q B Q a ,^0 * 't^.^ i f'. : :^'. : . v V? ":*:''"- :.">.'Xv V.* Section. Fig. 141. Plan. A concrete cesspool. Fig. 139 gives details of the construction of an ordinary manhole in concrete. Fig. 140 shows a concrete manhole cover. Such covers are now obtainable in stock sizes. The cover drops into a splayed rebate which is quite tight. Fig. 141 shows the construction of a cesspool for use where there are no public sewers. PIPES, MAINS, CONDUITS AND SEWERS. Reinforced concrete has been used extensively for the construction of aqueducts, pipe lines and sewers. A considerable pressure of water ran be resisted by reinforced concrete mains, and their lasting quality is shown by ever twenty years' service. Fig. 142 shows a reinforced concrete water main. These pipes ha v e a sheet of steel or iron in the centre with bars wrapped spirally round outside, and similar bars of smaller size placed inside, the whole being concreted inside and out. The sheet of steel or iron serves to make such pipes watertight under a great bursting pressure. The rods wrapped round, however, give the real strength to the construction, and the concrete protects the steel thoroughly against corrosion. 1,200 yards of such water mains have been laid in Swansea, and Fig. 142 illustrates the preparation of the reinforcement before concreting. Concrete electric conduits for carrying mains and wires are now extensively adopted, either being formed in situ or moulded in sections and laid like iron or earthenware conduits. Concrete sewer pipes up to 2 ft. 6 in. internal diameter and even larger are now manufactured by a number of firms, and can be obtained as regular articles of commerce. They have lapping joints PIPES, MAINS, CONDUITS & SEWERS. 183 Fig. 142. Reinforcement for water main. or are put together with a capping ring consisting of a short length of pipe of larger diameter, the joint being made with Portland Cement mortar or Portland Cement grout. Plain and reinforced concrete tubes are now extensively used for sewers in substitution for brick, glazed earthenware and iron. The con- crete resists the action of acids, and is very durable in running water. The cost is usually less than for brick or vitrified pipes, and though the latter, perhaps, are cheaper up to 18 inches diameter, the extra cost fig. 143. Reinforced concrete sewer at Acton, London, 184 PIPES, MAINS, CONDUITS & SEWERS. Fig. 144. Circular tubes. Fig- 145. Sewer pipe at St. Anne's-on-Sea. PIPES, MAINS, CONDUITS & SEWERS. 185 of concrete pipes is warranted. The pipes are egg-shaped or circular in section as shown in Figs. 144 and 145, the former giving a faster flow with a reduced quantity of sewage. Though a glazed surface gives a greater velocity of flow than concrete, yet the imperfect joints in a glazed pipe compare unfavourably with those of a concrete pipe, which are quite close and offer no resistance to the flow. Such pipes can be easily reinforced so as to be of any desired strength to resist any ordinary pressure. Reinforced concrete pipes with a steel skeleton protected with about a 3 inch of concrete have been in use for the Paris sewers for 17 years now without repairs being necessary, and, when portions have been removed to make junctions, have been found to have suffered no deterioration from such service, being as good as when first put in. Fig. 143 shows a reinforced sewer in course of construction at Acton, London, W. Fig. 146 shows the construction of a reinforced concrete sewer for the Urban District Council of Great Crosby. Owing to the unstable and water-logged condition of the subsoil it was necessary to exercise the very greatest care in the con- struction of this sewer ; and it is stated the ground could scarcely be worse, being composed largely of sand and peat, water-logged at a depth of 2 feet to 3 feet be- low the surface. The dia- gram shows how the diffi- culties were overcome. First of all, a layer of concrete was put in the trenches be- tween the waitings which were left in position, and in this concrete were embedded ordinary jubilee track rails combined with steel sleepers for reinforcement, these not being required for further service. Upon this bed of concrete was placed a spe- cially-moulded concrete block, upon which was laid a rein- forced concrete pipe, and the trench then filled in with concrete. This was the method adopted on the fore- ghore for a length of 120 f|$ Fi O- 14 - , T . . . , \ f f Section through CWGT.< yards. It is joined at another (I .. Great Croby. 186 PIPES, MAINS, CONDUITS & SEWERS. point by a sewer con- structed in a similar manner as regards the lower portion of ron- crete and the moulded blocks, but the top part of the sewer is constructed egg-shap.xl of bricks starting off the splays of the moulded concrete blocks. The total length of the sewer is over two miles, somewhat to these con- invert blocks been m a n u- n stone- Blocks similar crete have factured ware, but these in reinforced concrete were eminently satis- factory as a substitute. Fig. 147. Conduit at Kinlochleven. Fig. 147 illustrates a reinforced concrete conduit that has been built at Kinlochleven, Argyllshire. This conduit was for the purpose of taking away from the site of a large factory and village water which came down the mountain side as rivulets. The unreliable nature of the ground, which was composed partly of large boulders and partly soft earth, necessitated careful consideration in the prepara- tion of the design, but the conduit illustrated would be equally appro- priate in many circumstances. Fig. 148 shows an interesting storm- water sewer in course of construction, in which expanded metal sheets are embedded to give the necessary resistance to either external or internal pressure. The manner in which the work has been built, together with the centering, is clearly shown in the view. The leakage of water into tunnels, sewers, etc., if coming through in isolated spots, can be remedied by cutting a small tapered hole from the inside of the tunnel or sewer, enlarging somewhat as the depth of the hole increases, sp that when filled with cemenf in th,e PIPES, MAINS, CONDUITS & SEWERS. 187 Fig. 148. Storm water sewer at Sal'burn-'by-the-Sea. Fig. 149. Culvert to farm road. 188 PIPES, MAINS, CONDUITS & SEWERS. PIPES, MAINS, CONDUITS & SEWERS. 169 190 CULVERTS. form of a wedge the pressure of the water from the outside will help to bind up rather than loosen the cement plug. Having cut the hole, tallowed waste forced into the back will hold the water for a sufficient time to allow of the hole being filled with stiffly-gauged quick-setting cement. When the cement is set the pressure of the water canno't force the cement plug out of the hole by reason of its larger diameter at the end nearest the water. Figs. 150 and 151 show (i) the rein- forcement, and (2) complete section of the main delivery pipe recently built for the Mexico City Waterworks. Fig. 152. Arch culvert. CULVERTS. In connection with rural roads and estate work concrete culverts have come into general favour. They should be built during the dry season, if possible, or the water may be diverted during their construc- tion by building a dam above the culvert and conveying the water away from the work by means of a wooden trough or pipes. Typical culverts are shown in Figs. 149 and 152. Trenches for the foundations are excavated below the frost line, say about 3 ft. wide. Tfie foundations are usually constructed by the side of the stream, the floor, formed upon the bed of the stream, resting on these foundations. HOUSES. 191 the side walls are built up and a cover placed thereon, the concreting being done upon a centering, very much the same as the circular form illustrated on page 68. For culverts of more than 10 ft. diameter it is advisable to use reinforcement, which may consist of a meshwork or a lattice of steel rods. HOUSES. A further purpose to which concrete is specially applicable is the erection of cottages for agricultural labourers, tenant farmers, estate agents, and the like. The concrete blocks, of which cottages are chiefly built, can be made by ordinary labourers and estate workmen without the help of skilled artizans, and in many cases cartage, except that of the cement, is saved, all other materials for the concrete being found upon the site. For house foundations trenches 18 in. wide and 6 in. deep require to be filled with concrete to the cellar level. If there be no cellar, the foundations should be carried below the frost line. The concrete should be composed of i part Portland Cement, T.\ parts sand, and 5 parts broken stone or shingle well rammed in place, and the whole of the site should be covered with a 4-in. layer of it as before described on page 168. Partition walls may be built 4 in. or 6 in. in thickness of solid concrete, placed between f^irms as before described, and on a proper foundation. If walls are built below ground, as for instance in cellars, they should be of solid concrete, and care should be taken that the forms Fig. 153. Concrete villas at Paisley. 192 HOUSES. Fig. 154. Concrete Manor House at Port Chester, New York. HOUSES. 193 Fig. 155. Bungalow, Carnegie, Pa. Fig. 156. Bungalow at Carnegie, Pa. 194 HOUSES. Fig. 157. Bungalow at Bilton, Harrogate. remain in position for three or four weeks if earth be filled in against the back of the wall. Fig". 153 is a photograph of two semi-detached villas at Paisley, the walls of which are built of hollow concrete blocks. The balls on the pillars and the coping were all made in special moulds by the aid of the machine for making the blocks. The average cost of the blocks was stated to be ^d. each, and they measured 6 in. long, 8 in. high, and 10 in. thick. The body of each block was made of 4 parts gravel and sand to i of cement, while the face of the block was made of crushed granite and cement in the proportion of 2 to i. Figs. 1 155 to 157 show some picturesque types of bungalows con- structed 'of concrete built in situ. Fig. 161 shows a house that has been built of concrete blocks, while Fig. 1^4 on page 192 shows a large mansion entirely constructed of monolithic concrete. Figs. '5^ ar >d 159 show some interesting examples of concrete slab houses, built about 1878, at Croydon. Fig. 158 shows a block of cottages, and Fig. 159 a house in Friends Road, Croydon. The walls of these cottages, both inside and out, were constructed of concrete slabs about i in. thick screwed to timber framework, and in some of the larger houses the floors were of concrete slabs placed upon massive oak beams which give a pleasant old-world effect to the rooms, and at the same time provide a substantial fire-resisting floor. The floors were built with a double thickness of concrete. These s'abs, of course, resist the weather, are equable in temperature, and HOUSES. 195 cheap. The slabs were moulded in the form shown in Fig. 160, the surfaces being marked out to imitate ornamental vertical tiling, and were coloured red in imitation of tiles by lust putting a slip or slurry of cement and red oxide of iron into the moulds before the backing material was applied. Cm \jdon. 158. Concrete slab cottages at Croydon. They were tried for roofing, but found to be rather too heavy for economy and convenience. Fig-, i 6 o shows the arrangement of reinforce- ment provided, the rods being placed across the slabs to enable them to be taken out of the moulds sooner than could otherwise have been done without breaking by their own weight. These cottages were put up by the late Mr. W. H. "Lascelles, an early pioneer in the use of concrete for many purposes, especially Fig. 160. Arrangement of Reinforcement. Details of concrete slab, showing reinforcement. 196 VARIOUS BUILDINGS. domestic uses. In a house which he built for himself at Croydon he had a large conservatory in which there were elaborate concrete shelving and rockeries. Caps to chimneys can be cast in concrete, which generally protects the chimney better than bricks. A bottomless box should be made the size of the required cap, and one or more small bottomless boxes, to correspond with the flues of the chimney and | in. higher than the large box, should be placed within. The concrete may be filled in and sloped off on the top so as to allow the water to run off ; its thickness is usually about 4 in. A reinforcement may, with advantage, be used, and should consist of metal meshwork or of j-in. rods placed lattice-wise. The cap may, if desired, be built in place. In that case the form should be placed in position on the chimney, reinforcement put therein and the concrete filled in in the ordinary way. Chimney caps should be bedded in Portland Cement. VARIOUS BUILDINGS. Fig. 163 illustrates a pleasing architectural treatment of a village hall in the village of St. Petroc Minor, Cornwall. The hall measures 50 ft. long, 24 ft. wide, with a wing attached constructed as a care- Fig. 161. Cottage, Walkergate, Newcastle-on-Tyne. VARIOUS BUILDINGS. 197 taker's house, the plan being L-shaped. The walls are of con- crete blocks cast en the site, each block measuring 32 in. long, 9 in. high, and 10 in. thick, with a cavity in the centre to render the wall damp-proof and more equable in temperature. T h e blocks were composed of i part cement, 4 parts river gravel, znd i part river sand. Another interesting feature of the work is that it was designed and constructed under the supervision of amateurs. The donor, Mr. Athelstan Riley, officiated as architect, while the local churchwarden superintended the construction as clerk of works. There is some fine oak panelling in rhe hall together with a concrete chimney piece shown in Fig. 162. The building cost under /^oo. or about 6{d. per cube foot, which is extremely low considering the ornamental character of the work and the expensive interior fitments. Fig. 162. Concrete chimney piece in Village Hall. -- BM4 Villa?? Ilall, St. Petroc Minor, Cornwall. 198 VARIOUS BUILDINGS. VARIOUS BUILDINGS. 199 200 VARIOUS BUILDINGS. VARIOUS BUILDINGS. 201 Figs. 164 to 1 66 show applications of concrete building blocks to the con- struction of buildings of some importance. Fig. 164 is a view of the Queen's Skating Rink at West H a r t 1 e- pool. Fig. 165 shows the Presbytery at Stock- ton-on-Tees, and Fig. 1 66 a school-house in the same town. The school is 85 ft. long by 62 ft. wide, and 32 ft. in height. It has two storeys. The floors are of reinforced concrete, the staircases are likewise in concrete, and the corridors are laid in red and black concrete tiles. A novel feature of the building is the playground on the roof. It was erected with 9 in. concrete facing Fiflr. 167. Manila Cathedral. Fig. 168. St. Aloysius Church, Glasgow. 202 VARIOUS BUILDINGS, VARIOUS BUILDINGS. 203 Fig. 170. Church at Sundcrland. 204 VARIOUS BUILDINGS. Fig 171 Motor garage at Cheney, U.S.A. blocks and a line of glazed brickwork. The skating rink is 270 ft. long by 106 ft. wide. The hollow concrete; blocks arc rock-fac'":d outside and sparrow-pecked inside. Fig. 107 illustrates the Cathedral of St. Mary and St. John at Manila, in the Phillipine Islands, which is constructed of reinforced concrete, and is a picturesque and suggestive architectural treatment of the material. In tropical countries, of course, the destructive pro- perties of white ants and dry rot have to be reckoned with, and further- more, buildings are required to resist earthquake shocks, so that reinforced concrete is the best material to use. The walls, towers, and parts of the building were of reinforced concrete. The style of the building generally is Spanish Renaissance, and it has a seating capacity of over 1,000 persons. The dimensions of the nave and chancel are, width 60 ft., length 180 ft., the small transepts being 22 ft. long by 18 ft. wide. The two towers flanking the main entrance are 18 ft. square by 57 ft. high. The vertical walls are double or hollow. Fig'. 168 illustrates another church of reinforced concrete having a vau'ted and domed roof in concrete, reinforced with sheets of expanded steel. Fig. 169 shows the interior of a church in Gothic style con- structed of some 300 tons of Christie artificial stone, i.e., Portland Cement concrete. Fig. 170, views arc shown of a church erected at Sundcrland in concrete blocks. VARIOUS BUILDINGS. 205 Fig. 171 shows a motor-house constructed of concrete blocks, measuring 12 ft. by 20 ft. by 9 ft. 4 in. The floor is also of concrete 5 in. thick, as well as the roof, the latter being reinforced. Motor pits are very necessary for the proper overhauling of the interior of cars, and Fig. 172 gives details of the construction of a pit in concrete. Satisfactory dimensions have been found to be the following: 6 ft. by 3 ft. by 4 ft. 6 in. ; but these can, of course, be varied according to circumstances. Iron and similar materials liable to cause sparks from nails in boots should be avoided, so that the steps should be wrapped with cloth. A shelf or recess on either side of the pit is an advantage, enabling the person in the pit to keep the tools, etc., handy. A suitable cover can be made of 2-in. boards to each of which a sunk lifter should be provided. Fig. 173 shows a fire station in Sedgwick, Alberta, Canada, built of hollow concrete blocks. Fig. 174 illustrates the Ferry Tower at San Francisco, which was constructed after the earthquake that occurred there in ion- It is - fs 5CCTION A-D SECTION C-D PLAN POBTION Or TOP Fig. 172. Motor pit. 206 VARIOUS BUILDINGS. particularly interesting because there was some sort of rivalry between steel-frame construction and reinforced concrete construction, as to which was the best as regards general economy and resistance to earthquake shock. The steel-frame advocates who erected this tower with a skeleton framework of steel were, however, averse to employing brick walls because the earthquake had shown that these were shaken off the steel framework, so the walls of this tower are of reinforced concrete, though the frame is of steel. It shows the elaborate archi- tectural treatment that mav be given to the concrete. Most of the other Fig. 173. Fire Station at Sedgewick, Alberta. VARIOUS BUILDINGS. 207 Fig. 174. The Ferry Tower, San Francisco. 208 VARIOUS BUILDINGS. buildings in San Francisco even if of steel-frame construction have reinforced concrete walls now, but a great many of the buildings have been reconstructed in reinforced concrete throughout. Fig- 175 shows a building erected to replace the Royal Mail Steam Packet Company's offices at Kingston, Jamaica, which were destroyed by the earthquake there some time ago. Reinforced ' con- crete is being extensively used in the rebuilding of Kingston because of its proved resistance to earthquake shock. A number of theatres have been constructed in reinforced concrete. Fig. 176 is an example. At one time it was customary to construct stands for spectators of timber, and much timber work is still done in this way, but the cost of heavy timbering Fig. 175. Royal Mail Steam Packet Co.'s New Offices, Kingston, Jamaica. is very great even if the structure is only temporary, for after the timber is removed there is much waste on it and it is considerably damaged, and large timbers are not at all cheap to buy. Reinforced concrete has therefore come into use for such purposes, and a number of large stands have been erected at various football grounds and race courses. Fig. 177 shows such a stand at the Warwickshire Race Course, and Fig. 178 shows a large stand erected at the Bradford Football Ground. Fig. 179 shows the plan of the roof, together with details of the reinforced concrete construction of some underground lavatories erected at Bridlington for the Town Council. It will be noted that some of the walls are reinforced concrete while others are of brick ; the reason for this was that the latter part of the lavatories was built about 15 years previously, and they were enlarged and a new roof substituted VARIOUS BUILDINGS. 209 210 VARIOUS BUILDINGS. VARIOUS BUILDINGS. 211 1 212 VARIOUS BUILDINGS. for the old. The new walls had to retain the earth so they wen? constructed with counterforts as shown in the section. The roof was covered with asphalt on top of the concrete. The retaining wall is 5 in. thick, and the size of the roof beams and the thickness of the flat roof is marked on the plan. Several underground lavatories have been built for the same corporation, and the Borough Engineer esti- mates that quite 30 per cent, of the cost is saved by adopting rein- forced concrete, because instead of heavy retaining walls being re- quired, such a light wall as shown in this case can be substituted, while there is no necessity for putting on a massive concrete roof sustained in the old-fashioned way upon steel joists spaced about 3 ft. apart. Urinal stalls of concrete have been used extensively for a number of years. The concrete is moulded with a rich mixture so as to give a very impervious glassy surface, and the detailing of the structure can be similar to that used for any form of glaze-ware or brick / / NJ COUNTERFORT WITH SECTION AN I* IS ' PLAN or .TOON DAT ION 7' COON -re* TOR Plan of roof. Fig. 179. Underground lavatories. Bridlington. VARIOUS BUILDINGS. 213 ' 1*' ll 1 1 5 **' i 1 S ' i Ut L '^VQ A ,C^ Q i ! \ 5< 1 -. ,) = \ I ^ ,' .' $ , i - $// ./--} J 1 214 VARIOUS BUILDINGS. construction. In many cases the cement rendering on a brick wall will serve the purpose, and in that case a richly-proportioned plastering about i part of cement to 2 of sand is put on the wall in the manner described on page 84. The crazing or cracking of glass, opalite, porcelain tiles and other facings fixed upon a cement backing (much used in underground conveniences) which sometimes occurs, is often due to the fact that the materials have been embedded on neat cement mortar. A mixture recommended for such work is equal parts of cement and sand. For temporary urinals where a water supply is not provided, preparations are sold for coating the concrete in the form of a paste so as to serve as a disinfectant, the properties of which last for some considerable time. Cement is a much more economical material for the foregoing than sheet lead which one often sees used. A cement and sand surface to a timber building can be easily plastered on sheets of metal or even wooden lathing. Allied to the subject of walls and pavements is the construction of fives and racquet courts. Both these require high walls and a paved floor, the chief difference being that in the former game the ball is struck with the hand, whereas in the latter it is struck with a racquet, but it has to bounce against the wall and floor, both of which should present hard, impervious, unbroken surfaces. Reinforced concrete is particularly appropriate for such construction. The walls can be built thin, panelled at the back, i.e., stiffened by ribs, braces and buttresses. The reinforcement need only serve to resist stresses, and the effect of temperature changes which would be inclined to crack plain concrete. The surface finish ot the walls should be trowelled cement and sand, the work being done the same as is described for plastering on page 84. The floor is brought to a level surface the same as described for pavement construction on page 168. The wall requires to have a line clearly marked upon it above which the ball must be struck, and this wall can be made a prominent feature by special white cement or by forming' it with a finish made with a white material such as is described on page 112, or if preferred the line can be put in with a mixture coloured black. In the game of fives each public school has its own variant, the Eton game being the most complex. Fig. 180 shows a fives court on the Eton model. Tho omission of the " pepper-box " and of the various splays and offset- makes the court practically like a small racquet court, which is the more usual form for private houses and schools. The foregoing remarks about unbroken surfaces apply also to the construction of tennis courts. If the courts are covered the construction of the building will be similar to that of other structures referred to in these pages. They may be of plain concrete, moulded in situ, or of reinforced concrete or of concrete blocks. The floor of the court itself should be reinforced to prevent temperature cracks, and the marking of the court can be made prominent by inserting a strip of coloured cernen.t and sand finish, the court itself being VARIOUS BUILDINGS. 215 216 CONCRETE ON THE FARM. finished as described for pavement construction. The amount of steel re- quired for temperature re- inforcement is dealt with on page 52. Reinforced concrete has been used for the building of strong rooms, as it has been proved that it provides a protection against burglary superior to steel alone ; the walls are impenetrable to ordi- nary tools and explosives have little or no effect, whereas a hole can be fairly easily made in sheet steel by their aid. The steel reinforce- ments, which are consider- able in number in such work, offer a decided resistance to burglars, for although a large hole in a wall may be made by means of explosives, yet the steel rods hold the concrete in place and remain in posi- tion even after the concrete is removed. An oxyacetylene blowpipe has little effect upon concrete, and to cut a hole through a reinforced concrete wall, and to saw or fuse through the reinforcement, would take a good deal of time, and the barrier offered lo burglars is almost insurmountable. Of course, in such strong-rooms the reinforcing- bars should be about i in. diameter if valuables are to be stored, but for ordinary purposes, where the strong-room is for guarding- documents against fire, only small bars are necessary. Fig. 181 shows a burglar and fire-resisting strong-room in which the reinforcement consists of indented steel bars. A more novel application still is the construction of a reinforced concrete safe. Fig- 182 shows a safe of this tvpe. This safe measures 2 ft. 4 in. by 2 ft. 4 in. by 3 ft. high. The walls and door are 4 in. thick, reinforced with | in. twisted steel, the lock and hinges being cast in the centre of the wall and door, and, to maintain the uniformity, the handle is of twisted steel, the safe being home-made in every particular. CONCRETE ON THE FARM. Some interesting examples of the employment of concrete on the farm are illustrated in the accompanying photographs. Figs. 183 to Fig. 182. A reinforced concrete safe. CONCRETE ON THE FARM. 217 Fig. 183. Cottage and barn of concrete "blocks and monolithic concrete at Great Canfield. 187 relate to work done on the farm of Mr. Charles Wall, J.P., at fjrcat Canfield, near Dunmow, nineteen years ago. The most in- teresting- point about this work is that much of it was done with the coarse material lying to hand, viz., excavated clay, burnt to ballast. Tn some cases, however, Mr. Wall used cinders and grit, which had to be brought to the site. Mr. Wall's idea was that concrete would be more economical than bricks, and that the making of the blocks would provide work for his men in the winter. These were made on his barn floor. Even the rusticated quoins shown in the cottage photograph (Fig. 183) Fig. 184. Moat walls of concrete at Great 218 CONCRETE ON THE FARM. were made by a farm labourer at 145. a week. Mr. Wall believes that ballast is as good as any coarse material if bvirnt well. Should the burning be accidentally unequal, the monolithic work can be so covered with rough- cast as effectually to keep out the weather. Nowadays machines are to be had for turning out blocks more quickly than by hand, but Mr. OPt Jljjl Wall thinks a landowner or his clerk of the works could improvise one out of a hay binder. Mr. Wall's experi- ence makes him an advo- cate of concrete cottages i n suitable districts and where they can be built in rows. He has used the material not only in blocks, but also monolithically for walls round his moat (Fig. 184), for a barn (Fig. 183), a stable (Fig. 185), a laundry, a piggery (Fig. 186), and glass-house walls, and for a I Fig. 185. Stable of concrete blocks at Great ('anfield, with cinder as the coarse material. Fig- 186. Concrete piggery at Great Canfield. CONCRETE ON THE FARM. 219 Fig. 187. Water tower at Great Canfield of rough cast reinforced monolithic concrete. Well head also of concrete. water tower (Fig. 187). The weight of water in this tower and of the floors of the two rooms used as stores, must be con- siderable. Neverthe- less, the walls are but 6 in. thick. They are only reinforced laterally with three- inch angle iron bolted together. One of the floors of the tower is used as an apple store, from which the concrete walls are found to keep out the frost. Ventilation is o'btained by making the permanent sashes open from inside at the top, so that straw may be thrust into the opening. This has answered admirably, the apples having been kept good till May. Mention should be made of a simple filter tank for water provided alongside the moat. The wail of the meat is 6 in. thick, and being- made of burnt clay ballast only is permeable. The tank is placed alongside the moat with its floor at the same level as the bottom of the moat. Its wall is of rough concrete 6 in. thick and is at a distance of 6 in. from the moat wall. The intervening 6 in. is filled with clean sand, which is renewed from time to time. The water goes through the moat wall into the sand and out of it through the tank wall into the tank. The ballast for the moat walls was obtained from the clay excavated from the moat. The work at Borris, Co. Carlow, Ireland, here illustrated, was done on the large estate of Mr. W. McM. Kavanagh, J.P., D.L., at various periods during the last few years. The large cattle shed illus- trated in Fig. 188, constructed in 1902, so satisfied the owners as to the advantages of concrete for farm work that a large amount of concrete work has since been done continuously on the estate. This cattle shed is 100 ft. long by 50 ft. wide. It was originally a dung pit having a wall round three sides of it, and during the winter months was nothing less than a swamp, in which cattle invariably sank up to the body. It was decided to cover over the pit and convert it into a cattle shed. Concrete pillars, 18 in. square and 12 ft. apart, were built on the existing stone wall, as shown in the photograph. In the top of each pillar an iron plate with two large projecting bolts was embedded. The bolt-ends were connected to the steel roof trusses. Down the centre of the shed and along the fourth side steel stanchions are used, embedded 5 ft. deep in the boggy ground in pillars of concrete. The floor is concreted to a depth 220 CONCRETE ON THE FARM. of i ft., and has a gradual fall to a large concrete tank 12 ft. square and 8 ft. deep. The valuable liquid from this tank is pumped out and used in the gardens and on the farm. The building has turned out a very valuable investment. The manure (amounting to about 400 loads per annum) is now worth is. per load more than it used to be. In summer the shed serves as a fine shelter for the cattle, with room for 40 beasts. In rainy weather the men are put in to turn the manure, and the shed is also used for shearing sheep, for lambing- ewes and for young lambs in the early spring. The cost of construction was about ^"250, and has proved a 10 per cent, investment. Fig. 1X9 illustrates a concrete passage, 100 ft. long and about 20 ft. wide, in front of the large cattle shed, which was formerly paved with stones that hurt the cattle's feet and were difficult to keep clean, besides which seeds from the hay or straw dropped between the stones and produced a full crop of weeds. Instead of these stones being picked up, a layer of rough concrete was simply spread over them to a thickness of 2g in., and finished off with in. smooth surface com- posed of 4 parts sand to i of Portland Cement. This surface was grooved in squares by pressing a frame therein, as shown. The paving has proved its value by saving labour, by its tidier appearance and by protecting the feet of cattle. 188. (a & b). Cattle shed at Borris. CONCRETE ON THE FARM 221 1 222 CONCRETE ON THE FARM. Fig. 190 Interior of cart shed at Borris. Next the cattle shed on the opposite side to this passage is a row byre, the floor of which is similarly paved, and the favourable result of concrete paving is as evident in this shed as in the other. A stone-paved floor in a boiler and mixing house on the farm was also relaid in concrete. It used always to be foul owing to frag- ments of roots, etc., becoming fixed between the stones and there decaying. Cattle food left on this floor for even a short while became tainted and was injurious to the health of the animals. It was also a difficult matter to shovel up the food into the feeding baskets and buckets. The cost of concreting this floor has been amply repaid by savings as well as by the cleanliness of the place and the wholesome- ness of the food. Fig. 190 illustrates the interior of a long cart shed. The portion shown is used as a rearing shed for prize fowls. It is necessary to have the ground quite dry for these birds, and the shed was chosen for this reason. The floor is of concrete 35 in. thick, and with smooth impervious surface, so that it may be washed without fear of its retaining any of the moisture afterwards. The strength of the work is shown by the fact that the portion of the shed shown has been used for several years during the summer to store a large steam thresher weighing five tons. Down the centre is a division in the concrete to allow a frame to fit in and divide the shed into sections. Fig. 191 illustrates a sheep dipping trough and pens, the whole formed of concrete with a timber fence. The view shows the protective door over the top of the trough to prevent animals drinking the poisonous fluid. The trough is about 8 ft. long, 4 ft. wide, and 5 ft. deep. The floors of the pens are of concrete. The sheep are driven into the pens in the foreground ; a man catches them in turn and hands them into the bath, in which each is held for one minute. A long sloping stairway, with cement grips for the animals' feet, leads therefrom, up which the sheep walk into the draining pen seen in the background. The concrete floor in this pen slopes towards the trough, so that as the sheep shake the fluid out of their fleece it finds its way back into the tank, and little is lost. This could not be done with a brick or flagstone floor. Fig. 221 illustrates a line of garden frames 60 ft. long by 6 ft. wide, with concrete walls. The woodwork of the frames was sent to the gardens ready made, and ordinary handy men mixed the concrete, arranged the forms, and fitted the frames finally. The saving in cost on materials alone effected by adopting this construction, instead of CONCRETE ON THE FARM. 223 ft ordinary brickwork, was ;io on this small job. Fig. 219 shows a large greenhouse So ft. long by 20 ft. wide. The front wall is 4 ft. b in. and the back wail 8 ft. above ground, the latter dividing the house from the stoke- hole and potting shed. T h i s greenhouse i s practically all of con- crete, glass, and wood i.e., the water tank, the paths, and the large forcing pit inside, as well as the walls, are of concrete. The outside wall is rough cast, so that creeping plants may get a good grip on the surface. When climbing plants are required to grow on the concrete it is well to leave the surface rougher than ordinarily so as to afford a good hold without the likelihood of their being torn off by a high wind. Fig. 192 illustrates some cement stucco work that has been done on the end of an old building attached to the mansion at Borris. The wall, built of rough random rubble with granite stones, began to fall away in front, rendering it necessary to take some means to preserve it. Consequently it was rendered with a mixture of i cement to 4 of sand, finished with a second richer coat proportioned i cement to 2 of sand, marked out in imitation of stone blocks. Much similar work has been done to the mansion, a part of which is 200 years old. There would be but a very small portion of the older rubble walls remaining if they had not been fortified by Portland Cement stucco. The Portland Cement and sand rendering has been done a portion at a time, and as new work would look staring in its whiteness against the old unless some precaution were taken, the following expedient that may be found useful in repairing stucco work was adopted : The Portland Cement rendering at Borris was made several shades darker than the adjoining work by the addition of soot or fine coal ashes. A few hot days' sun soon turns the new work to the desired colour. Concrete was first used on the Borris House Estate about 30 years ago, for large foundation blocks under two large turbines used for pumping and sawing and turning timber. These blocks may be seen to-day in Fig. 192. Cement stuccoed gable at Borris. 224 FEEDING FLOORS AND the bed of the stream as firm as solid rock. The use of concvele was discontinued until the turbine foundation blocks had been given a fair test. Gradually other work was carried out in the material, tut until 1902, when the large shed above referred to was constructed, larger works were always executed in stone or brickwork. Nearly all the estate work is now carried out in concrete, although stone, bricks and lime are in abundant supply upon the property, while there is plenty of timber and well-equipped saw mills. Even the rubbish heap is turned to good account, as coal ashes, slag, etc., all come in useful in the making of concrete, which has been employed in ways too numerous to mention, ranging from a pig trough to a cow-house. The sewerage scheme has recently been extended, all the drains teing laid on a concrete foundation 4 in. thick. For the design and superin- tendence of these interesting examples of concrete work the estate steward, Mr. F. R. Browne, is responsible. FEEDING FLOORS AND FARMYARD PAVEMENTS. It is far better to place the fodder on feeding floors formed of concrete than on the ground, according to the old method. To supply animals with food on a feeding floor is generally recog- nised as economical for the food, but there is another aspect, too, which is not so well recognised ; viz., that if the food is put on to a feeding floor the sole purpose is not to prevent the waste caused by it getting trampled into the earth, but also to prevent contamination or decav, and the dissemination of disease. \Yooden feeding floors, of course, keep the food out of the mud and dust, until they become worn. Bui they only temporarily maintain the health of the animals, as in a short while they become infected with disease germs. On big farms it has often been found necessary to burn the wooden floors to stamp out hog cholera. If a feeding floor is made of cobble stones, or of fine dressed small stones, there are a number of crevices between the stun; s in which the food lodges so that the animals do not remove it, and the food there lies to decay. Moisture also remains in such cavities, and food thrown on such a feeding floor, through contamination wilh ih<> food already remaining in the crevices, quickly goes bad. Such a floor is neither economical nor healthy. Concrete provides the ideal feeding floor ; such floors not onlv effect a saving in food, a shortening in the time of fattening, and a decrease in labour, but they also afford perfect protection to the health of the animals. Concrete floors constructed with a proper fall so as to drain away any liquids falling on them, cannot become rcallv infected with germs, their surfaces can be easily kept clean, and thoroughly disinfected with oils and dips. Vermin cannot find a refuge in them as in the case of timber feeding floors. Not only do rats eat a good deal of the food, but it is now recognised that they are very active agents in the spreading of disease. Tests have often been conducted to show the economy of concrete floors in the saving of grain and manure alone, and the results have FARMYARD PAVEMENTS. 225 proved, quite apart from the improved health of the stock, that they often pay for themselves in but the short period of one year. Of course, on a feeding floor a good deal of manure is deposited, and it can be arranged so that the liquid drains to a sump, and used for watering the kitchen or flower gardens that are usually found near a farmyard ; the manure, too, is improved in quality as we have shown on page 220. Concrete feeding floors are constructed practically in the same manner as any other concrete floor on the ground or concrete pave- ments, the manner of constructing which is described in foregoing pages. It should be noted, however, that round the outside edges of the feeding floor, it is well to dig a trench about 18 in. deep by 12 in. wide, and to fill this with concrete, to prevent hogs undermining Hie floor, and also to prevent rats nesting in it. Over the ordinary part of the site, between the trenches, a foundation of stones, rock, gravel or broken brick, or other hard material has to be filled, but the trench should be kept open for the concrete which alone is filled within it. The lay-out of the gutters can be arranged in any convenient manner. Either one or more manure pits can be provided for the liquid manure ; these manure pits require covers. The sumps for manure can be made in concrete, but they will have to be carefully done so as to give a watertight finish ; this, however, is described in c'etail in the informa- tion upon waterproofing elsewhere in this volume. The manure pit will require a special cover to allow the liquid to drain into it, but to keep out any other material. This is easily done by means of a Fig. 193. Concrete feeding HOOT. 226 STABLES, COW-HOUSES, grating with a basket contrivance which can be lifted out to remove any straw or any other solid substance, similar to the ordinary gullies for stables. Light floors can be made 4 in. thick in concrete with the foundation extra below ; for heavy loads, 6 in. of concrete should be provided. It is well for these 4 in. and 6 in. floors to stand above the level, the foundation being well rammed up to the ordinary ground level so that the concrete that is laid thereon will stand proud ; the edges of the concrete may be kept true by the use of 13 in. or 2 in. planks. STABLES, COW-HOUSES, PIGGERIES, AND CHICKEN- HOUSES. Fig. 195 shows the adaptability of concrete for the construction of byres for the housing of cattle. The floors of such a building can be economically constructed of concrete, which can be made to give a foothold and to continue clean, sanitary and hygienic, by tne adoption of the expedients referred to in our description of internal paving. The walls, the stalls (see Fig. 197), and the roofs of such buildings can also be economically constructed of concrete. In byres and stables concrete feeding floors and gutters and feeding troughs are used. The concrete should be of good quality so as to prevent any dampness being conveyed up from the ground, and this will add to the comfort of the animals. Fig. 199 shows some reinforced concrete dairy cow stalls erected at a model farm at Winnings Colwall, Malvern. The mangers and floor are also of reinforced concrete. Figs. 196 and 200 show a piggery of an up-to-date character, built entirely of concrete, the roof being in concrete reinforced with steel rods. Fig. 201 shows some reinforced concrete stalls in stables erected in Whitecross Street in the City of London. The manner of constructing these stall divisions is clearly illustrated in Fig. 202. The cast iron posts were placed on a base inserted in the floor, and filled in with concrete, the slabs being moulded and inserted in these posts. The base had a rod passing up into the post and the concrete when filled in bound the whole together. The tops of the posts had a finial which 5. 8 *- - 3 o- -^ 194 Feeding trough and floor in cow-hoyse. PIGGERIES & CHICKEN-HOUSES. 227 228 STABLES, COW-HOUSES, Fig. 197. Concrete stall divisions in cow-house. was screwed on to the rod which went into the base. The concrete was proportioned, 3 parts of crushed shingle, 2 of Thames sand, and i of Portland Cement. The floors were treated with a finish of concrete made with granite chippings and were marked out in squares. The stables have now been in existence some years and have given every satisfaction ; their first cost was about half that of ordinary stall divisions in iron and timber combined. Fig. 198. Interior of cow-house. PIGGERIES & CHICKEN-HOUSES. 229 Fig. 199. Cow stalls, mangers, etc., Winnings Farm, Malvern. Fig. 200. Interior of concrete piggery. 230 STABLES, COW-HOUSES, tfig. 201. Stores and stables, Whitccross Street, London. (View of stalls.) T"n SECTION AMD PLAM OF FOOTSTEP- tig. 2t/2. Details of reinforced concrete stalls. PIGGERIES & CHICKEN-HOUSES. 231 232 STABLES, COW-HOUSES, Figs. 203, 204 and 253 show some examples of reinforced concrete at the Union Stock Yards of Chicago, where the material is being used in substitution for the old-style timber work. Fig. 253 shows the type of fence which has been adopted for general use throughout the yards. The posts are distinct from the rails, being moulded separately and assembled afterwards. Fig. 203 shows some of the cattle pens which are of monolithic construction, the panels in the fence being 23 in. thick. Fig. 204 shows a number of troughs used in the pens for watering stock ; these troughs are 16 ft. long, 73 in. deep, and 3! in. average thickness. Concrete is extensively used for the construction of drinking places and water troughs. Fig. 205 shows a drinking place built by Mr. Fred. Ballard, on Winning's Model Dairy Farm, at Colwall, Malvcrn. It was formed by dishing down the ground to the level of an agricultural drain that taps a small spring, and covering the surface with concrete. Fig. 204. Watering troughs, Chicago Union Stock Yards. It cost less than 205. Water troughs may be built without reinforce- ment, but they then require to be thicker than if they tre reinforced with a small proportion of steel. Troughs may be built upon a solid foundation or set upon corner piers or blocks. A common size is about 8 ft. long, 2 ft. wide at the top, and i ft. deep inside dimensions. Figs. 204, 206 to 209 show two varieties of water troughs. As a general direction for building such troughs, we would advise the selection of a level piece of ground. A bottomless box is formed out of 2 in. boards, the inside measurements being 8 ft. by 2 ft. 8 in. wide and 2 ft. i in. deep. The ground should be rammed hard inside the form and a layer of concrete, 23 in. deep, proportioned i Portland Cement, 2 sand and 4 coarse material, tamped well on the bottom. A sheet of metal meshwork should now be placed on this layer of concrete turned up to within i in. of the top of the forms at the sides and ends. 'Another 2$ in. of concrete should now be placed on the meshwork and rammed lightly so as to bring water to the PIGGERIES & CHICKEN-HOUSES. 233 Fig. 205. Concrete drinking place for cattle at Colwall, Malvern. surface. This should be smoothed over carefully with a trowel, and the inner form, slightly greased, should now be put in place, care being taken to keep it at an equal distance from the sides and ends. This form should be made of 2-5n. boards and be slightly wedge-shaped, Fiy r>C Cvncret: watering trough. 234 STABLES, COW-HOUSES, Fig. 207. Rectangular cattle trough. PIGGERIES & CHICKEN-HOUSES. 235 Fig. 2uy. Concrete watering trough. the outside dimensions being about 8 ft. long, i ft. 6 in. deep, and 2 ft. wide at the top and i ft. 9 in. wide at the bottom. The space between the two forms should now be filled with concrete, tamping lightly. The mcshwork in the sides of the tank should be kept in the centre between the forms. As soon as the forms are removed, any irregularities in the surface should be smoothed off and, as soon as it is hard enough not to crumble, be painted with a pure Portland Cement wash or grout of about the consistency of cream. If an inlet and outlet are required these may be made by putting pieces of pipe in place before filling in the concrete, or greased tapering wooden plugs may be used that can be withdrawn when the concrete has set. Even though the base of a watering trough is not reinforced, it is advisable at least to reinforce the sides. Figs. 207 and 208 are troughs which we exhibited at the Royal Fig. 210. Forms for hog troughs. 236 STABLES, COW-HOUSES, Agricultural Show, at Norwich, in 1911. The rectangular cattle trough of no gallons capacity was reinforced with steel rods and wire netting, quite unbreakable, and cost only us. ad., while the circular tank or trough to hold 120 gallons, similarly reinforced, cost 95. Feeding troughs may be constructed in the same manner as watering troughs. The following, however, is a method for making a hog trough. A bottomless box, 6 ft. long, 12 in. deep by 12 in. wide is made from 2-in. boards, and two triangles out of 2-in. plank having a base of 12 in. and height of 8 in. are placed 5 ft. 6 in. apart and a i -in. plank nailed on each side of the triangles. This inverted V-shaped trough is placed inside the bottomless box, and the triangular fillets placed round the edges to make a square edge. The space left is filled with concrete composed of i part Portland Cement to 3 of sand or fine shingle. After a week the outer forms should be removed and the outside and inside painted with Portland Cement grout. If a round- PIGGERIES & CHICKEN-HOUSES. 237 Fig. 212. Concrete chicken-house. bottomed trough is required an inner form can be made from a log sawn in halves, as shown in Fig. 210. A hog pen may be constructed by excavating a trench of the size and shape desired i ft. wide, to below the frost line, filling this with broken stone and on top of this foundation building walls 4 in. thick and 4 ft. high of 1:3:6 concrete. A space for a gate should be left and the trough constructed for the hogs as described. Fig. 211 shows the construction of a boiler for heating food for pigs or cattle. Figs. 194 and 198 show a feeding trough in a cow house, the con- struction of which is obvious, and from what has been said of the construction of other forms, the forms for this can easily be made without the help of further exact description. Fig. 212 shows a chicKen-nouse. Concrete is particularly advan- tageous for such a purpose, as it resists the incursions of rats, weasels, and other vermin, and can easily be kept clean. Such a chicken-house may be built with solid concrete walls 5 in. thick. If the house is not more than 8 ft. wide, the roof, sloping one way only, might be made of a 4-in. concrete slab with reinforcement of steel rods or heavy meshwork of the size suggested in the table on page 148. The slope should be i in. in every foot, and the surface should be well trowelled to make it waterproof. If the roof is more than 8 ft. span, concrete beams or rafters should be adopted, with a top slab ; or a pitched roof may be used either of concrete or other materials. Concrete shelves and water basins may also be adopted in such a model chicken-house. The use of coke-breeze or clinker is advised for the coarse material in constructing such a building, as it gives sufficient porosity to the con- crete to prevent moisture condensing on the inside of the walls in cold weather. The walls should be coated with a Portland Cement wash 238 DOG KENNELS. Fig. 213. Born at Shipshewcma. as soon as the forms are removed. The Portland Cement wash need not necessarily be always a grey Portland Cement colour ; it may be coloured as desired in the way referred to in the directions for colouring concrete on page 112. DOG KENNELS. Dog kennels are also constructed of concrete, plain or reinforced. Concrete is an excellent material for this purpose owing to the ease with which it can be kept dry and clean, and it is decidedly more healthy than boarding. The entire surface should be quite smooth, and all angles rounded. SHEDS AND BARNS. The foregoing directions for the construction in concrete plain and reinforced of various sorts of buildings apply equally to sheds of all forms, ice-houses, and barn supports. Fig. 213 shows a reinforced concrete barn. It is a twelve-sided building, 60 ft. in diameter, each side being 16 ft. long. The walls are 30 ft. high above the ground floor, and are reinforced with rods of heavy wire fencing put in the middle of the wall. The sides of doors and windows and above them are further reinforced with old iron. SHEDS AND BARNS. 239 Fig. 214. Barn, with raised concrete floor. The walls are 12 in. thick one-third of the way up, the middle third 10 in., and the top third 8 in. thick. The ground floor of the building is of concrete, and has a drive-way through the centre with a row of stalls and mangers on each side. Fig. 214 shows an application of concrete in the construction of a timber barn, namely, the building of the raised concrete floor upon which the barn itself is constructed. It is very necessary in destroying the rat to remove its nesting place, which is usually in the floors, and, 1 Ftp. 215. Rick stand. 240 DAIRIES & LAUNDRIES. Fig. 216. Concrete bottle-washing trough for dairy. furthermore, corn does not go mouldy on a concrete floor, provided there be good ventilation, and the roof be tight. Such concrete floors should be built early in the season so that they may be thoroughly dried out before grain is stored thereon. One of the simplest ways of attaching the studding to the concrete floor is to embed i-inch bolts 8 to 10 in. long, head down in the concrete, projecting 2$ in. above the surface, and build thereon a 2 in. by 6 in. nailing-sill or plate to the floor. The bolts should be spaced not more than 3 ft. apart. The nailing-sill should not be counter-sunk in the floor so that its top lies flush with the surface, as in such a position it is liable to rust. Shelving can generally be constructed of concrete. It is then impervious to liquids, not subject to decay, clean and sanitary, and fire-resisting. For library and record offices, safe vaults, barracks, asylums, etc., concrete shelving is largely employed. Another application of concrete to agricultural work is for rick stands, and one is shown in Fig. 215. The pillars of this stand are formed of concrete, being 4 ft. high, i8 in. square at the base and 8 in. at the top. The pillars shown were made exceptionally long as the district in which the rick was situated was subject to floods. DAIRIES AND LAUNDRIES. Numerous dairies have been constructed in concrete, for not only is a concrete building cool in summer and warm in winter, but this material is easily kept clean, and is therefore sanitary. This considera- tion applies also to laundries, whether in town or country. Fig. 216 shows a large concrete washing trough for a dairy. DAIRIES & LAUNDRIES. 241 Fig. 218. Laundry at Belfast, built of concrete blocks. Fig. 218 shows an addition to the establishment of the Monarch Laundry Co., Ltd., in Belfast, constructed in reinforced concrete and concrete blocks. Its' dwarfed appearance is due to the fact that it is proposed to raise the building eventually another storey. The walls are of rock-faced hollow concrete blocks, and the roof and its sup- porting concrete columns are reinforced. The method of applying the combination of the two materials has been found particularly advantageous. Sanitation on farms and in industrial establishments of all sorts is receiving increased attention, and concrete construction is likely to be a factor in the provision of proper conveniences at a moderate cost. Fig. 217 shows concrete shower-baths and lockers erected on a farm, where they are much appreciated. Fig. 217. Concrete shower-baths and lockers. 242 FRUIT-HOUSES, GREENHOUSES Fig. 219. Concrete greenhouee. FRUIT-HOUSES, GREENHOUSES AND ROOT CELLARS. Concrete is an ideal material for the construction of fruit-houses, greenhouses, root and mushroom cellars. For fruit-houses, the walls, floors and roofs, and the internal fittings in the way of shelves can be conveniently built with concrete. For greenhouses, concrete is superior to wood, for it does not require constant repair, and saves fuel, as it retains heat and keeps out cold air. Greenhouses (Figs. 219 and 220) should have a founda- tion 10 in. wide and 16 in. deep, or below frost level, formed of concrete . 220. Greenhouse of reinforced concrete AND ROOT CELLARS. Fig. 222. Concrete garden frames. proportioned i part Portland Cement, 3 parts sand, and 6 parts broken stone or shingle. On this the walls should be erected about 6 in. or 7 in. thick, composed of i part Portland Cement, 2\ parts sand, and 5 parts clinker or coke-breeze, to the height required. The ridge should be 6 in. wide by 8 in. deep and made of concrete composed of i part Portland Cement, 2 parts sand, and 5 parts broken stone or shingle f-in. size, reinforced with two steel rods, say i in. diameter. If the width of the greenhouse is not over i6ft., beams 2^ in. by 5 in. extending from the ridge t,o side walls, each reinforced with one -in. bar, will be strong enough to support the sashes. The ridge should be supported every 10 ft. by 12 in. sq. reinforced concrete posts. The tables and shelves may be made of concrete 25 in. thick, proportioned i part Portland Cement, 2\ parts sand, and 5 parts clinker, reinforced with a metal meshwork. Hotbed frames can also be built with 3-in. concrete walls propor- tioned i part Portland Cement, 3 parts sand, and 6 parts broken ttone or shingle, resting on a 4-in. foundation (Figs. 221 and 222). The shelves and benching in greenhouses and conservatories should be of concrete also. The construction and moulds for same are shown in Fig. 223. pi g . 2 21. Concrete garden frames at Borria. 244 PRUJT-HOUSES, GREENHOUSES -SLAB //V /2" ' JfCTlOM Zb THICK, ACH R/M- FORCED MTTt TWO <" JfACfD 7"JWT. ND OF FOX M RMOI/D /'60AKDS 'x /%"- Fig. 223. Benching for conservatory or greenhouse. The excavation for root cellars, which are built half above and half below ground level, should be carried about 16 in. below the desired level of the floor; and round the sides a foundation of concrete propor- tioned i part Portland Cement, 3 parts sand, and 6 parts broken stone or shingle, should be formed 12 in. deep. Between and slightly above these foundations 12 in. of porous material should be rammed over the whole area, exclusive of foundations. On the foundations a wall 18 in. thick, composed of i part Portland Cement, 25 parts sand, and 5 parts clinkers, broken stone, or shingle, should now be built, and a floor laid over the whole of the interior composed of similar concrete, 4 in. thick, as described on p. 168. The roof may be as shown in Figs. 224 and 225, and formed of concrete as already indicated. Near, the top at each end window openings should be left in which a sash should be fitted after the concrete has set and the forms have been removed. Mushroom cellars should be two-thirds below the level of the ground to obtain the best results ; otherwise their construction is similar to that of root cellars. AND ROOT CELLARS 245 Hoot cellar witit, pitched roof Fig- 225. Root cellar with curved roof. SILOS. Fig. 226 A concrete tilo. wards wetted and covered with about 8 in. for the foundations and the bottom of the Cement, 2$ parts sand, and 5 parts broken stone or shingle. Upon this foundation the double walls may be built each 3 in. thick, with a hol- low space between of about 9 in. The forms should be about 4 ft. high and should be raised gradually as the work goes up. The concrete should be composed of 1 part Portland Cement, 2 parts sand, and 4 parts broken stone or shingle. The reinforce- ment should be \ in. diameter steel bars, placed vertically about every 3 ft. and hooped SILOS. Concrete is largely employed for the con- struction of air-tight silos. It is fire and ver- min proof and does not decay like timber, and provided the walls be re- inforced and not un- necessarily thick, the cost is small. Fig. 226 shows a large silo. Hollow walls are often found to be of advantage in cold cli- mates, as the air spaces between the walls pre- vent freezing. The foundations should be constructed below the frost level, say 16 in. wide and the excava- tion inside the walls should be filled with dry materials after- concrete, composed, both silo, of i part Portland Fig. 227. Silo at Rugby. fig. 228. Grain silos at Silvertown (end view), 248 SILOS. round with in. diameter steel rods about every 6 in,, well overlapped and wound round with thin wire at the overlapping, The inside of the walls will require plastering, while the outside may be left rough cast or washed over with Portland Cement grout. The roof may be either of concrete or of timber. Every silo requires a ventilator at the top and an entrance for a man which can be easily reached by means of a ladder, as shown in Fig. 226. Openings for doors should be left about every 3 ft. on one side of the silo for convenience in handling the materials to be stored. A shoot running the whole height of the building should be erected simultaneously with the walls. The walls of the shoot may be 4 in. thick reinforced with iron bars running vertically and others running horizontally, as for the walls. The size of the shoot is generally about 2^ ft. wide and 4 ft. on the face, and its walls may be of single thickness. Fig. 228 shows a large grain silo. Fig. 227 shows a small silo for containing materials, the bins Fig. 229. Coal bunker at Du/ermlti. WATER TANKS & RESERVOIRS. 249 measuring 12 ft. 6 in. by n ft. 6 in. inside, having a carrying capacity of 60 tons. Coal bins or bunkers are of smaller construction. A . typical example is shown in Fig. 229. WATER TANKS, WELLS AND RESERVOIRS. Underground cisterns can, with advantage, be made in concrete, and may be round or square, as shown in Fig. 230 or Fig. 231. To make a round cistern a hole should be excavated 16 in. wider than the desired diameter, or a wall two-thirds of the thickness of a brick wall, which could be used for the same purpose, allowed for. The hole should be 14 ft. to 16 ft. deep. A cylindrical inner form should now be made, the outside diameter of which is the inside diameter of the cistern. The form should be about 9 ft. long for a 14 ft. hole, and n ft. long for a 16 ft. hole. It should be sawn lengthwise in equal parts for convenience in handling, and the sections lowered into the hole and there united to form a circle, and allowed to rest on blocks about 6 in. above the bottom of the excavation. These blocks must be withdrawn when the spaces between have been filled in with concrete. The concrete is well tamped qn the bottom and in the sides. It is advisable to puddle the concrete against the form to prevent the formation of pockets or crevices. To form the dome, a wooden floor may be built across the top of the form with a hole in the centre about 2 ft. sq., bracing the floor well with wooden posts resting on the bottom of the cistern. Round the edges of the hole, resting on the wooden floor described, a vertical form is raised, and round it a cone-shaped mould of very fine wet sand is raised from the outer edge of the flooring to the top of the form ; this may be smoothed with a wooden float. A layer of concrete 4 in. thick is now put over the sand so that the edge rests on the side wall. After the concrete has been allowed to harden for a week, one of the floor boards may be removed so as to allow the sand to fall to the bottom of the cistern. When all the boards and forms have been removed they can be easily passed through the 2 ft. sq. aperture, and the sand taken out by means of a pail lowered on a rope. A square cistern is easier to build than a round one. The walls may be 8 in. thick, as advised for the circular tank, and all four walls should be built simultaneously. If the dimensions are more than 8 ft. sq. the walls of a cistern should be reinforced with a metal meshwork. Tanks for storing water are also constructed in concrete. They are easy to keep clean, they do not rust or decay, and thus possess many advantages over other forms of tanks. Tanks may be either square or round, and the sides should be tapered slightly inside as advised for water troughs. The general description for forming troughs applies to the formation of tanks. Reinforcement should always be used, and the concrete should be dense and impervious, made of i par(: best Portland Cement, 2 parts sand, and 4 parts broken shingle 250 'WATER TANKS & RESERVOIRS. Fig- 230. Square concrete cittern. Ft'0. 231. Circulor concrete cittern. WATER TANKS & RESERVOIRS. 25\ or stone not more than i in. diameter in size. It is most convenient to use meshwork for small tanks and steel rods for large tanks. The following table gives the approximate sizes of steel reinforcements for tanks of various dimensions : . "3 .2 S g . cJ. o5 ^ ti ti 2 *c a S* 'c'O si Depth of T Feet. III 2 ^ i t fr % :/ 1 gl la" Mil S| b Spacing Circuinfere Rods at hot Inches 11 * ^^ Diameter Vertical R Indies Spacing Vertical R Feet. 5X5 4 i 6 9 I l'i 5 X 10 4 A 6 9 i 2 2 10 X 10 8 t 6 12 f 2 2 10 X 15 8 6 12 ^ 3 15 X 10 12 ^ 6 15 5 &i 15 x 15 12 t 6 15 1 3 NOTE. Circumferential Rods should be bent in rings, placed in the centre of the wall and the ends lapped 2 ft., and 2 in. or so at the ends bent at right angles. The spacing of the circumferential rods should be gradually in- creased from the bottom 9Hi to the top. The interior pres- sure of the water is assumed to be taken by the steel ; the concrete is therefore only re- quired to be thick enough to embed the steel and make the tank watertight, and should vary with the height of the tank, but not neces- sarily with the diameter. A minimum thickness of 4 in. for a 5 ft. tank, running up to 15 in. for a tank 15 ft. deep is sug- gested. For a very large tank the thickness of the concrete and the amount of steel reinforcement required should be care- fully calculated by a competent engineer. For tank work great care should be taken fi to have the densest Reinforced concrete reservoir at Scafeti, Italy. 252 WATER TANKS & RESERVOIRS. Fig. 233. Reinforced concrete water tower at Champagne- sur-Seine, France. Fig. 234. Water tank. possible proportions of sand and coarse material with more than enough cement added to fill all the voids. The concrete should be made very wet and the whole tank should be made with as few joints as possible. When a joint must be made the surface of the old work should be chipped all over the rougher the better and all loose particles carefully removed. The surface should then be well wetted and a 5 in. layer of cement and sand mortar proportioned i -.2 applied, the new concrete being well rammed against it. When the concrete is new it is somewhat porous, and a method of stopping the pores is to use a wash of neat Portland Cement, This will effectively prevent the water getting WATER TANKS & RESERVOIRS. 253 through until the con- crete has had time to mature. Some large elevated tanks or water towers abroad and in this country have been con- structed in reinforced concrete, of which Figs. 232 to 236 show exam- ples. The tank at Bournemouth is of con- siderable capacity, and the total height is 45 ft. The reservoir is sup- ported on six square re- inforced pillars 35 ft. high and 18 in. square, and finished with arches to receive the tank. The water tower at Champagne - sur - Seine, in France, holds 22,200 gallons. The height is 1 08 ft. above the ground (Fig. 233). The water tower at Newton - le - Willows has a capacity of 300,000 gallons. The tank is 80 ft. above the ground. The tank proper is 5 in. thick at the bottom, the sides at the base being 6 in., reduced at the top to 5 in. thick. Figure 232 shows a water reservoir at Scafeti, Salerno, in Italy, which feeds an equipment in a mill for a sprinkler installation. In case of fire these sprinklers open automatically and the water from this tank gives adequate pressure and supply to extinguish, in its incipient stages, any fire that may occur. Fig. 234 shows an elevated water tank of reinforced concrete suit- able for supplying an estate or village. This particular example is in Holland. Fig. 237 shows a water barrel built throughout by an amateur. The walls are ig inches thick, the reinforcement consisting of 5 ordinary boy's hoops, 3 ft. in diameter, and galvanised wire netting doubled. The capacity of the barrel is about 200 gallons, and its total cost was 275., including the wooden stand at the bottom. Tanks for the storage of mineral oil in grocers' and other shops, factories, etc., can be constructed of concrete so long as they are made watertight and kept filled with water .for a month after comple- Fig. 235. Reinforced concrete water tower at Newton-le-Willowi, Lmnct. 254 WATER TANKS & RESERVOIRS. tion before being used for oil. The oil will not then damage the concrete. Tanks of a large size for storing paraffin or crude mineral oils can also be built of reinforced concrete, if treated in this manner, without fear of deterioration of the cement from contact with the oil. Fig. 238 shows some small acid tanks made of reinforced concrete. Many acids, however, are harmful and some destructive to Portland Cement concrete, and the effect of an acid should be ascertained before the tank is built. Concrete is attacked by many dilute acids quickly or slowly, according to the strength and character of the acid. In the case of acids which form soluble salts in combination with the lime of (he cement e.g., acetic, hydrochloric, nitric, etc., acids the action will be more rapid than in those cases (sulphuric acid, for instance) where the salt formed is wholly or partially insoluble ; the reason being ihat in the latter case the insoluble salt is deposited within the pores of the concrete and gradually closes up the surface, thereby preventing con- tact between the acid con- tents and the parts of the structure not yet affected. Tanning solutions are largely organic in character and often con- tain certain organic acids. Upon green con- crete the action of such liquids would probably be marked, but upon indurated concrete, espe- cially if of a dense and impervious charac- ter, the action would probably be only slight. Mineral and lubricating oils and petrol have no deleterious effect upon indurated concrete, but may reduce the strength of green concrete con- siderably. Unless the tank walls are made of dense, rich concrete, the loss of oil by percolation becomes serious, espe- cially with light oils like Water tower of reinforced concrete , . .. at Bournemouth. P etro1 or gasoline. Fig. 236. WATER TANKS & RESERVOIRS. 255 With all Storage tanks for liquids the importance of dense, closely compacted and properly graded concrete can- not be too greatly insisted Upon, Fig- 239 shows a num- ber of reinforced concrete vats on a Californian wine farm. These measure 4^ ft. high, 19 ft. in circumference at the top, and 13 ft. at the bottom. They are used in the manufacture of cream of tartar. On this same farm reinforced concrete has been used extensively for other works, namely, for the boiling rooms and the cel- lars, the sheds in the distil- lery, and the wine cisterns and fermenting tanks, and the liquids do not dele- teriously affect the concrete. Although sugar and sugar juices have a very in- jurious action if mixed with cement or concrete, they will not affect concrete which is thoroughly set and hardened. Fig. 237. Reinforced concrete cistern. Fig. 238. Acid tanks made with cement plaster and expanded steel. 256 GASHOLDERS. Fig. 240. Gasholder tank, Leigh-on-Sea. In works for the manufacture of tiles, arks are often provided to store a mixture of clay and water, known technically as " slip." These arks are usually built of octagonal form, 9 ft. by 9 ft. by 7 ft. deep. They can, however, be built more economically in reinforced concrete, the walls and bottom being about 8 in. thick, the concrete being made of i part Portland Cement, 2 parts sand, and 4 parts broken stone or shingle. If the walls are reinforced with metal meshwork they can be reduced to 6 in. A number of gasholder tanks and gasholder walls and supports have now been built in reinforced concrete. Three examples are illustrated in Figs. 240 to n 242. The construction of the tank is similar to that for water tanks. The walls and supports are like those of other structures. Fig. 242 shows a large gas holder that has been erected for the MunicipaJ Gas Works, Reick, Dresden, h which has a capacity of : v?l l 10,000 cubic metres -WMl Bfehi 3,300,000 cubic feet. The structure consists of three parts, i.e., a ring-shaped con- tainer and an enclosing wall, both of reinforced concrete, and a steel-frame domed roof and lantern. The ring- shaped container is con- structed for a depth of water of 10 metres (32 ft. 10 in.), Fig. 241. Gasholder at Dresden. and also serves as the VATS. 257 258 GASHOLDERS & RESERVOIRS. foundation of the enclosing wall. Well-kerbs are also constructed nowadays of con- crete ; they are 'the best, as they keep out the surface w a.t e r and are easily kept clean. After digging the well the desired depth and bracing the sides in short sections so that the earth cannot fall in, a circular form 8 in. smaller than the diameter of the well and 4 ft. long should be made and lowered to the bottom in sections and adjusted so that the concrete can be placed between the form and the side of the hole. This concrete should- be proportioned i part Portland Cement, 2\ parts sand, and 5 parts broken stone or shingle. To allow water to get into the well, loose broken stones should be placed in pockets every few feet until the water level is reached. After filling the concrete to the top of the form and allowing it to set over night, or until the concrete will bear the pressure of the thumb, it is raised 3 ft., again braced securely and the operation repeated until the ground level is reached. A slab of Fig. 242. Gasholder near Dresden. Fig. 243. Reinforced concrete reservoir at Downside Abbey. RESERVOIRS. 259 260 SWIMMING BATHS. b i.v;; J /;. N < f\i < ^ < & ,_ \ ';/ < ) v> H 1-J 1! 1 ^ z inTf- 1 ! i - ' j ^'^T" *>J a. '&z%i&3 J.7 51 * I Sj SWIMMING BATHS. 261 rough concrete about 4 in. thick and 8 ft. to 12 ft. in diameter should be placed round the top of the well on a foundation of rough broken stone, well rammed, about 12 in. thick, as described for paving. This prevents the surface water draining into the well. In sinking a well, a drum curb of moulded pipes of plain concrete or reinforced concrete (the latter being generally preferred) may be used instead of wood, this being formed with a sharp edge at the bottom, weighted in the same way as a wooden drum curb, the sinking being done by removing the earth from under it. As the drum curb gradually sinks lengths of similar concrete tubing are placed on the top and sunk with it, or the well may be gradually decreased in diameter beyond a certain point. Large reservoirs are also constructed in reinforced concrete, on the general principles explained for the construction of tanks, water troughs and cisterns. Reservoirs are often covered, and the cover has to be designed as a floor to sustain a certain load. The cover is, as a rule, supported on posts such as are used for supporting floors in buildings. Fig. 243 shows a covered, reinforced concrete reservoir in course of construction at Downside Abbey. Concrete has been extensively used in the construction of the reser- voir at Island Barn, East Molesey, Surrey, for the Metropolitan Water Board, which has an area of 120 acres and contains about 1,000 million gallons of water. The earthwork at the outer side of the embankment is at a slope of z\ to i. On the inner side the lower part has a batter of 4 to i and the upper 3 to i, the latter, to prevent damage from wash by the water, being paved with concrete blocks, set in ballast, with a wall faced with 'similar blocks at the top, com- pleted by a concrete coping moulded in situ. Fig. 244 shows this work in course of construction. Open-air swimming baths also belong to the same class of work. If the reservoir or swimming bath is above the ground it is supported by buttresses, but if below ground the earth supports the side walls. Public swimming baths are generally built of reinforced concrete, as it is found that by such construction considerable economies iust be used. For strengthening the concrete it has sometimes been pro- posed to use wood, either on the surface or embedded in the posts, but this is inadvisable, for if the wood is placed on the surface it will decay, and if it be embedded in the post it will swell by the absorption of water and crack the post. There is no necessity to use galvanised wire for reinforcing con- crete fence-posts, for the concrete itself protects steel perfectly against rust. If plain smooth iron rods are used they should be bent over at the ends to prevent their slipping in the concrete. A fence-post is called upon to resist lateral pressure or bending as a cantilever ; therefore the steel should be placed as near the outside as possible (only about f in. protection is needed), and all sides of the post must be reinforced, as there is no telling from which direction the pressure may come. The most usual system of reinforcing, and, theoretically, the best, is to place a reinforcing rod or wire at each corner of the post. The coarse material should be broken to 5 in. size, and the propor- tions usually adopted are about 1:2:4. The mixture should be of medium wetness. Fig. 246 shows a mould for forming fence-posts, which should taper for the sake of economy ; this is easily arranged. The mould here shown is for making four posts at once, but larger ones could be used on the same principle if desired. The mould consists of two end pieces " A " carrying lugs " B " between which are inserted strips " C." The various parts are held together by hooks and eyes, or sometimes by a form of brace with wedges. The sides are prevented from bulging by a centre brace as shown. The boards used should be i in., or preferably i in. thick. In Fig. 247 the post shown measures 6 in. square at the botton, tapering to 6 in. by 3 in. at the top and is 7 ft. in height ; two of the sides are parallel, the taper not being given to all four sides, it being more convenient to mould them with two sides parallel as shown. Fig. 248 shows posts tapered on all sides for economy of material, and Fig. 249 shows a wooden mould for making high posts that taper on all four sides. These posts are usually square at the top and square at the bottom. A variety with chamfered sides is shown in Fig. 248. Care is required in tamping the concrete into the moulds to ensure the corners being well filled. Without this precaution the metal might become exposed, and eventually rust. A simple permanent fastener for attaching fence wires to the posts is a long staple or bent wire well embedded in the concrete, and bent or twisted at the end to prevent extraction. Galvanised metal should be used for fasteners as they are not protected by the concrete. A piece FENCES & POSTS. 265 of small flexible wire, about 2 in. in length, threading the staple and twisted several times with a pair of pliers, holds the wire in position, as shown in Fig. 250, and is easily renewed when necessary. Othor methods of attaching the wires are illustrated in Fig. 252. Instead of fixing the staples permanently into the posts, a % in. diameter steel bar may be inserted, well greased, through holes bored in the sides of the form the proper distance apart for stringing wires when the concrete has finally set. After about four hours these bars can be pulled out, leaving a hole through which the fence wire can be strung, or a short piece of wire can be run through and the ends twisted round the running fence wire, or wooden or lead plugs may be inserted in the concrete and the wire fastened to them with staples. For the moulding of these posts our general instructions as to concrete moulding may be referred to. The moulds require to be coated with soft soap, oil, or grease, to prevent adherence to the con- crete. About 1 5 in. of concrete should be spread evenly over the bottom and carefully tamped so as to produce a thickness of about ij in. A piecs of board, cut as shown in Fig. 246, will be found useful for levelling the concrete to the desired thickness before tamping. On top of this layer two reinforcing rods are placed about i in. from the Fig. 252. Method of attaching fence wire to concrete posts. 266 FENCES & POSTS. sides of the mould, and pressed in until within about 5 in. of its face. The moulds are then filled and tamped in thin layers to the level of the other two reinforcements, the fasteners for the fence-wires being inserted during the operation. These reinforcements having been de- posited, the remaining \ in. of concrete is tamped and levelled off. To avoid sharp edges, which are easily chipped, triangular strips may be placed in the bottom of the moulds along the sides ; the top edges may be bevelled with a trowel, or by running an edging tool having a triangular edge on its bottom. Such a tool is shown in Fig. 251, and can be easily made of wood or metal. After one operation of moulding the mould should be cleaned with a wire brush before using again, and again coated with soft soap, oil, or grease. The ends and sides of the moulds may be removed after 24 hours, but the posts should not be handled for at least a week, during which time they should be kept well wetted and protected from sun and wind. The intermediate strips should be left in place until the posts are moved. In removing posts great care should be taken, as they do not become thoroughly hardened for some weeks. They should be allowed to harden for about eight weeks before being used, and during this time they should be placed upon a smooth bed of moist sand and protected from the sun, or they may be immersed in a water-tank during the period. If the former method be adopted they should be thoroughly wetted with water at least once a day. Fig. 253. Fence, Chicago Union Stock Yards. FENCES & POSTS. 267 Fig. 254. Fence with rails, Swanscombe. The cost varies, but approximately works out at is. 6d. per post under favourable conditions. In fence-posts 6 in. by 6 in. and 5 ft. 6 in. to 7 ft. long the amount of reinforcement required is about .06 sq. in. for one upon which there is not much strain, and about 0.2 sq. in. for the strongest that are likely to be required. There is no advan- tage in using pipes in- stead of rods for the rein- forcement of such posts. Corner posts may be made by enlarging the forms so that the inside measurements are 10 in. by 10 in. at the bottom and 6 in. by 6 in. at the top. For reinforcing these in. rods may be used instead of No. 6 wire, as used for the ordinary posts. A coat of Portland Cement wash is usually applied to the posts after they are removed from the moulds, this being well worked in with a brush. Boundary stones may be conveniently and econ- omically constructed of concrete. Fig. 255 illustrates an end post or post with struts for tightening the wires, the inclined prop resisting the pull. Figs. 254 to 257 show some fence posts erected at Swanscombe, near Gravesend, on an estate owned by the As- sociated Portland Cement Manufacturers (1900), Ltd. The ordinary posts are 6 ft. long, square sectioned with corners chamfered. The straining posts are 7 ft. long which are embedded in the soil F i g . 255. Fence straining post, Swanscom'be. 268 FENCES & POSTS. K* o > -*- - FENCES & POSTS. 269 t fl II L i ; fc "i ' H ; i H-.b - t ii ? a i i V +- i ' .9-.I = O O j I * X - t 1 - -H > ' 2 o i 5 t h O B< pa ^ i~ a u T"" ' X eClNFOBCED WITH -4- A DIA/^/- 3TCCL EOCO CCNTCES 5"3i* I i IA/^ SfCCJ- u *- u 8 " o_J VJ fc, _l Fence posts at Swanscombe II L -i 't j_ ,H S u u u ! ; a S ( * :j LI ? * 2 Zl 1 El* <- a. s i 9 1 H \ r d g 1 "ST I-' J*< 1 U_J Q. f H H H - ... * . i ' . i fi K^ | iij c S fe ! 1 ^^ 1 I- ^ 4 I 270 HITCHING POSTS & POLES. about 3 ft. in soft ground, and 2 ft. in harder strata. The struts may be 3 in. by 2 in. or 3 in. by 3 in., and the plates about 2 in. thick reinforced with expanded metal or a mesh work of rods on the under side. Similar posts without struts can be used for the ordinary part of the fence if desired instead of the plain ones ; the extra cost, however, is about 33 per cent. The following table gives the market price for good oak posts and the prime cost, including loading, of reinforced concrete posts as ascertained at Swanscombe, together with particulars of other types of concrete posts : Oak. Concrete. s. d. s. d. Line post A, 6 ft. long, 4! in. sq. at bottom, 2| in. sq. at top ...21 17 Line posts B, 7 ft. long, 6 in. sq. at bottom, 4 in. sq. at top ... 4 4 21 Straining posts C, 6 ft. long, with i plate and i strut 47 Straining posts C, 6 ft. long, with 2 plates and 2 struts for corner Posts _ 70 Rail posts D, 7 ft. long, complete with 3 rails and 3 wedges ... 7 10 Figs. 254 and 257 show another type of con- crete fence provided with rails. To enable a broken rail to be cheaply replaced the holes in the posts are made large enough to allow one rail to slide over another. When erected the top of the hole is filled with a concrete wedge, which may be set with cement mortar. The construction of these various posts is illus- trated in detail in Figs. 256 and 257. In the line posts, type A and B, it might be desirable for very rough use to make the four reinforcing rods inch diameter instead of f inch. As regards gate posts, type "D" is serviceable; they can be made for from 35. to 45. each, according to circumstances, without strut. The ordinary mixture for these fence-posts is 4 parts of good clean ballast put through a % inch sieve to i of Portland Cement. HITCHING POSTS AND POLES. Fig. 258. Concrete has also been adopted for making Concrete clothes clothes posts (Fig. 258). The process is much the post. same as fence-posts, just described, except that the posts should be 9 ft. long and should have an iron staple \ in. diameter embedded in the top, or a hole made near the top through which to run the clothes line. For reinforcing such posts, f-in. rods may be used. If the base of the post is well embedded GARDEN STEPS & TERRACES. 271 Fig. 259. Concrete horse-block and hitching post. in concrete then about 2 ft. will be utilised in the ground, but an alternative method of securing the post against the pull of the rope would be to either cast a base in situ or mould it with provision for inserting the post in a socket, much in the same way as is done with timber clothes posts and wooden base boxes. This has the further advantage of enabling the post to be removed when not required for use. Hitching posts should be made, in a similar manner, 6 ft. long and have an iron ring in the top. A horse-block and hitching post is shown in Fig. 259. The former can be made by turning a box, 24 in. long by 10 in. wide and 8 in. deep, bottom upwards on the floor, and building round it a box or form 36 in. long, 18 in. wide, and 12 in. deep, inside dimensions. This form should now be filled round with concrete, proportioned i : z\ : 5, and the top should be smoothed off with a straight-edge and floated. It should be allowed to stand for about 48 hours before the outside forms are removed, and be kept damp for three weeks, remaining in situ for that period. If a finer finish be desired, a coating | in. thick, composed of i part Portland Cement and i part sand, may be plastered over the block after picking it with a small axe and wetting it thoroughly. GARDEN STEPS AND TERRACES. Steps and terraces in gardens may be either monolithic formed in situ or cast separately in moulds and afterwards put in place. The following table shows the proper proportions for risers and treads : Width of Tread. Nosing to Nosing. 8 in 8 9 Rise. Tread to Tread. ... 8 in. - 7* ... 7 Width of Tread. Rise. Nosing to Nosing. Tread to Tread. 11 in. ... ... 6 in. 12 54 . '3 5 Generally, twice the rise and once the tread should equal 2 ft., or tread and rise equal 18 in. 272 GARDEN STEPS & TERRACES. Fig. 260. Flight of external concrete steps. It is not usual to make the risers less than 6 in. nor more than 8 in. If more than one step is to be taken on any tread the minimum width should be 30 in., but it is far better to raise the steps in short flights with wider land- ings between than to adopt high, wide steps. The foundations for all external steps should extend well below the frost line and should be formed of porous material, as described for paths, with drains situated at the lowest point to allow the water to run off. The steps should be wider than the paths or paving from which they lead so as to avoid the appearance of being cramped. It will improve the appearance to add a low parapet or edging, such as is shown in Fig. 260. Each step should be constructed with a slight slope to allow the water to run off. All steps that are moulded separately should be reinforced by iron rods, placed about i in. from the bottom of the step. Having excavated the slope to the required depth and put in the porous foundation in the same manner as described for paths, a plank should be placed on either side of the proposed step or steps and firmly supported. A layer of about i in. of concrete, proportioned 1:2:6, should now be laid on the foundation, and the reinforcement, in the shape of rods, or preferably metal mesh-work, placed thereon. The concrete is now filled in to the thickness of about another 2 in. Fig. 261. Separately moulded concrete steps. GARDEN STEPS & TERRACES. 273 After this has set for about 24 hours, boards should be placed between the side planks, starting at the top, so as to form the riser of each step. These boards should each have a groove or chamfer at the top to form the projection or moulding at the front top edge of each step. After the concrete base has been wetted the top form is filled with one part Portland Cement to two parts clean sand, smoothed with a wooden float, or, if a saving of material is required, the mixture may consist of one part Portland Cement, two parts sand, and four parts broken stone to within about 5 in. of the top, and a finishing coat of one part Portland Cement to two parts sand is then floated as recorded for paths. External steps that have to be supported upon walls for ascending to a porch or a similar raised platform may be constructed by raising two walls in concrete, the upper surface inclined at the desired pitch of the steps, but the top being 3 in. below the point where the inner edge of the tread meets the riser. Between these walls an inclined platform is now made of 2-in. by 4~in. boards well braced. On them, and over the top edge of the walls, a 3-in. layer of concrete is laid, reinforced at intervals of a foot by |-in. iron or steel rods, running from top to bottom. On this the steps may be formed in the manner described for the flight of steps on a slope. Should the steps be more than 6 ft. wide a wall similar to the two side walls should be built in the centre. The forms under the steps should not be removed for four weeks. If the height to which these stairs are required to extend is more than three or four steps, the reinforcement will need to be larger and placed closer together. To determine the dia- meter and spacing of the rods, reference should be made to the table on page 148, under " light floor loading," and the diameter and spacing of the rods selected should accord with the greatest length of the stairs calculated as a 3-in. floor-slab. If separately cast steps are required, these may be formed as in Fig. 261. A form is made, as shown, 14 in. by 17 in. inside measurement, with i in. for projection. This is nearly filled with concrete composed ^ip. 262. Garden roller. 274 FANCY PARK WORK, ROCKERIES of i part Portland Cement, 3 parts sand, and b parts coarse material, well tamped. The front board is now removed and the space at front and top filled with a finishing coat of i part Portland Cement to 2 parts sand. A reinforcement consisting of g-in. diameter rods should be placed at the bottom of such steps, and in fixing them in position they should be placed upon S-in. side walls constructed ,as before suggested on foundations 12 in. wide and carried down below the frost line. The steps should overlap each other 2 in. and the joints be made with Portland Cement mortar. -Fig. 262 illustrates another application of con- crete in the building of a roller. Such rollers are mow to be purchased at less cost than iron rollers. FANCY PARK WORK, ROCKERIES & LAND- SCAPE GARDENING. Concrete may be used with very good results for ornamental and fancy park work, especially for rockeries. Fig. 265 also shows a treatment in a conserva- tory. Fig. 266 shows the inside of an aquarium constructed in reinforced concrete, in imitation of a rock-cave. Some typical concrete garden ornaments are found in Figs. 263, 273 to 279. There are many good reasons for using concrete in gardens in preference to marble or stone. In the first place, it has the lasting quali- ties of flint, in fact it grows harder year by year. Then, too, it needs no protection against the severest wea- ther, freezing and thawing having no effect on its Fig. 263. Sundial. rigidity. The colour of this AND LANDSCAPE GARDENING. 275 Concrete pergolas. 276 FANCY PARK WORK, ROCKERIES Fig. 265. Interior of conservatory in concrete. Fig. 266. Interior concrete rockery in a reinforced concrete aquarium. AND LANDSCAPE GARDENING. 277 278 FANCY PARK WORK, ROCKERIES Fig. 268. Garden AND LANDSCAPE GARDENING. 279 Fig. 269 Balustrade and vases. Fig. 270. Garden entrance. 280 FANCY PARK WORK, ROCKERIES AND LANDSCAPE GARDENING. 281 282 FANCY PARK WORK, ROCKERIES AND LANDSCAPE GARDENING. 283 Fig. 274. Garden vases. 284 FANCY PARK WORK, ROCKERIES Fig. 275. Garden vase. Fig. 276. Ornamental table. AND LANDSCAPE GARDENING. 285 material in its natural grey cement shade is most pleasing, and blends with out- of-door surroundings in a way which marble or newly cut stone does not. It takes on rapidly the soft neutral colour of the common field stone, and, when made into some accessory of pleasing design, never looks out of place, as is often the case with marbles. Again, the cost of the material is rea- sonable. Concrete can be fashioned readily into any form, just as plas- ter and bronze take on the form of the mould into which they are run. Fig. 278, Flower tax. Fig. 264 shows pergolas constructed of concrete. Fig. 271 shows a concrete fountain at Caergwrle Spa, North Wales. The fountain is about 15 ft. in diameter, the walls and bed being made in situ of reinforced concrete. The central pillar supports a concrete basin which supports a brass fountain. The base, capping, and Fig. 277. Garden vase. 286 CEMENT & TREE DENTISTRY. F*^l pilasters were made ift _.ji&^^b It Liverpool and carted to the site. Fig. 272 shows an interesting garden treatment by the Chris- tie Patent Stone Co., -of Hull and Manchester. Fig. 267 shows a good treatment for a concrete garden bench. This particular example is 12 ft. by 5 ft. wide, and the concrete has a rough surface except on the seat where the face is smooth. The proportions employed for the concrete were, i part cement, 2\ parts sharp sand containing some gravel, and 5 parts clinker. The floor- ing is made of tiles, and tiles are also carried in a band along the back of the seat. The tiles are of red and blue- green colour, and look well embedded in the concrete. Other benches are illustrated in Fig. 268. Fig. 263 shows an effective concrete sundial, the sundial proper being in brass. Figs. 273 to 275 and 277 and 279 show some concrete flower vases. These are often reinforced with a network of wire ; while Fig. 276 shows an ornamental table made of concrete for garden use. Concrete flower boxes of the form shown in Fig. 274 look well. toig. 279. Pedestal vase. CEMENT AND TREE DENTISTRY. The uses to which concrete is put are really strange, one of the most remarkable being its employment in forestry. Tree surgery is what might be called the practical application ^of dentistry to trees. Both fruit and shade trees are valued now as never before, and by skilful methods the tree surgeon can give a new lease of life to trees which had otherwise practically reached their limit of existence. When trees develop decay there is no reason why they should be felled unless it is quite impossible to remedy them, but in the majority of cases by CEMENT & TREE DENTISTRY. 287 the application of cement or concrete, they can be preserved. To fill up the cavities in the tree with cement has been practised for a number of years now, but not always with success because a mis- take has been made in leaving the decay in place. The cement was simply filled in the cavity without any re- gard to draining or the subsequent healing of the wound. As the cement did not stick to the wood and the sway- ing of the tree by the wind often enlarged the crack between the wood and the filling, water penetrated behind the cement and decay went on even more rapidly than before. The tree grows in girth by the deposit of a .thin layer of new wood between the wood and the bark. There are three layers in this coat the middle one being composed of thin forming tissues known as the "cambium." The inner side of this layer forms new wood, the outer new bark. It is this new layer and the layers of the four or five previous years which are known as the sapwood, and form the active section of the trunk and branches. The cells of these inner rings are gradually covered by the yearly deposit of new growth, and from living sapwood become heartwood, which is dead, and serves merely as a strong framework for the living parts of the tree and as storehouses for excess material. This is the reason why hollow trees may often be found in a flourishing condition when the heartwood may have entirely disappeared. However, a landscape tree in this condition, deprived of the shelter of its fellows, is in grave danger, for a high wind or a heavy snow- fall may find it an easy victim. In repairing such decayed trees, after the mass of the decay has been removed from the interior of the rotting trunk there remains a shell of living sapwood and bark. Into this cavity a steel brace is Fig. 280. A cavity filled with cement. 288 CEMENT & TREE DENTISTRY. inserted and bolted in place. This gives to the tree a stability which by the decay of the supporting heartwood it had lost. Now comes an impor- tant operation, the cutting of the watersheds, which prevent the entrance of moisture. The watersheds (see Fig. 280) consist of a deep groove cut about an inch inside the edge and opening out to the ground below. The cement, being packed tightly into these grooves, forms a channel down which the water flows, to be led out at the base. The cavity is then wired throughout, the wire being stretched from nails driven into the wood, and acting as reinforcing for the cement. This work having been completed, the cement is made as moist as possible, and then built out into the original outline of the tree. The bark which has been cut back for an inch or so in order to prevent bruising while the work is in progress will eventually cover the filled-in wound, the tree thus regaining its normal appearance. In the case of exceptionally large cavities the opening is covered by large strips of zinc. The cement is then forced down into every crevice and allowed to set, after which the zinc is removed and a coat of fine finishing cement put on and painted the colour of the bark. By this method the tree sur- geon is enabled lo build out trees where fully half the wood may have been destroyed by lightning or from some other cause. The treat- ment serves as a fine example of the healing powers of nature, for it is remarkable how quickly these wounds will heal when pro- tected from moisture and further decay by the cement filling inside by the watersheds. The correction of the forked or defective crotch (Fig. 281) which are found to a great ex- tent in soft maples and elms, and to a less de- gree in almost all cur landscape trees, forms a large part of the Fig. 281. Packing a cracked crotch. tree surgeon's CEMENT & TREE DENTISTRY. 289 work. This form of crotch usually has its origin in the destruction of the original head or leader. In a case of this kind a double head is formed by the forcing out of two lateral buds. As Ihese shoot up, forming the new top, the old stump at their base grad- ually decays, allow- Tp|fV ' , Ify ing water to pene- iJ \v,' *>lffiH trate into the crotch. Nature tries desperately to heal this wound, but the imperfect joint is constantly forced open by the wind and prevented from uniting by the old stump, until finally, weakened by de- cay, the tree splits. Many of the finest trees are ruined every year by the splitting of these defective crotches. These cases are often exceed- ingly difficult to treat. The decayed matter must first be removed with great care and thoroughness in fact, the dentist is not more conscien- tious in removing decay from a tooth than is the tree sur- geon in cleaning out these cavities. The opening is then packed tightly with cement. Cutting watersheds in these crotches often takes all the work- in a n ' s ingenuity and patience, Fig. 282. A 290 CHIMNEY SHAFTS & CONDENSERS. for, working in the narrow limits of the fork, as he is compelled to do, it is exceedingly difficult to use his tools. But here most of all a perfect watershed is required, as the water running down the limbs and trunk would otherwise find lodgment behind the filling. In case of a large tree the additional precaution is taken of putting a bolt directly through the crotch, while a chain is placed some twelve or fifteen feet up. CHIMNEY SHAFTS AND CONDENSERS Reinforced concrete has been used now for some years for the construction of tall chimney shafts. The application of high tempera- tures has little or no effect below 900 Fahr., it being a fortunate coincidence that concrete and steel have practically the same coefficient of expansion, namely, for concrete .000006 and for steel .0000065 P er degree Fahrenheit. This means that the concrete and steel will expand and contract together without parting company, thus neither losing adhesion nor causing internal stresses. For this reason reinforced con- crete is frequently used for ovens, melting house floors, etc., and the property of equal expansion and contraction means also that reinforced concrete floors, beams and columns are not seriously damaged by fires in buildings, which latter may be put in service again with a minimu.n of reparation. Fig. 283 shows typical factory chimneys at North fleet, Kent, at the works of the Associated Portland Cement Manufacturers (1900), Limited. The reinforcement consists of T section steel bars running vertically up the chimney hooped round every few feet with round rods. A chimney at Briton Ferry is 150 ft. high. It has an inner shaft 6 ft. diameter and an outer shaft 13 ft. diameter. A chimney at Belfast is 200 ft. high by 8 ft. 6 in. diameter. Fig. 314 shows an interesting application of reinforced concrete to a somewhat novel use, namely, the construction of a cooling tower, the framework of which is of reinforced concrete. Such a structure does not, of course, suffer decay like steel or woodwork. Fig. 282 is an interesting application of chimney construction in reinforced concrete that excites remark. This chimney, in the form of a tree trunk, is built at Malmaison in France, on the estate of Mr. Edwards Drake. The owner was reluctant to spoil his timber by the erection of an ordinary chimney, so devised this concrete tree in order that the harmony of the scene might not be disturbed. Concrete has been supplanting wood for a number of years, but this is probably the first instance where timber has been reproduced in this original form. BRIDGES AND PIERS. The numerous applications of concrete, plain and reinforced, in the construction of bridges and piers do not call for any lengthy notice here. The advantages of this form of construction are everywhere becoming more and more appreciated. Figs. 284 to 286 show several small bridges which illustrate the kind of work erected by private owners or rural authorities, often seen in the country. The design of even a small bridge requires some expert knowledge, and should be made by an engineer. CHIMNEY SHAFTS & CONDENSERS. 29! r mam > - - Fig. 283. View of two reinforced concrete chimneys at the Northfleet Works of the Associated Portland Cement Manufacturers (1900), Ltd, ( x indicates the chimneys,) 292 BRIDGES & PIERS. 1 fig. 286. Reinforced concrete bridge at Li'Zburn, Northumberland. Fig. 284 shows a light reinforced concrete foot-bridge providing access to Cloghari Island at Mizen Head. It has a span of 172 ft., and a height of 150 ft. above the sea. Fig. 285 shows a reinforced concrete bridge at Colne, Lanes. The span is 45 ft. 6 in., the thickness being 10 in. at the crown and 14 in. at the haunches. Fig. 286 shows a road bridge at Lilburn, in Northum- berland, the span of which is 40 ft. Small bridges or culverts are often required 5 ft. to 7 ft. wide, and, say about 5 ft. high. These can easily be built in plain concrete in arched form, making the thickness at the centre about 12 in. For large bridges, however, plain or reinforced concrete may be employed, and in any case, an expert should be consulted as to their design. i| !i I i i Fig. 287. Brooklands Motor Track Bridge. BRIDGES & PIERS. 293 Fig. 284. Footbridge at Mizen Head, Ireland. Fig. 285. Reinforced concrete bridge at Colne, Lanes. 294 BRIDGES & PIERS. One of the largest plain concrete bridges that have been constructed is that at Walnut Lane, Philadelphia, which has a centre span of 232 ft. in the clear. Fig. 289 shows another of the large plain concrete bridges in America, namely, the Connecticut Avenue Bridge at Washington. It consists of 5 arches, each of 150 ft. span, supported by 2O-ft. piers, and at each end of the series of arches is an 82-ft. arch, separated from the others by an abutment 37 ft. in width. At the ends BRIDGES & PIERS. 295 296 BRIDGES & PIERS. Fig. 290. Reinforced concrete jetty at Dagenham. of the bridge proper are two abutments about 136 ft. in length. The total cost of the bridge, exclusive of land, was ;: 70,000. Its width is 52 ft., and the height of the floor above the ground 130 feet. Fig. 287 shows a portion of the motor racing track at Brook- lands, near Weybridge. At this point it was necessary to carry the track across the River Wey, so this peculiar form of bridge was arrived at. The racing track has a uniform width of 100 ft., so that this is the width of the bridge. It is also about 200 ft. long. The foundations of the bridge are sustained by reinforced concrete piles, as the soil at this point was unstable. Fig. 288 illustrates an artistic reinforced concrete bridge at Innsbruck in Austria. Fig. 291. Pier at WedcllsJiorg, Denmark. BRiDCES & PIERS. 297 Fig. 29! shows a small reinforced concrete pier, constructed at \Ycdellsborg, in Denmark, to serve as a landing stage, supported on reinforced concrete piles. A number of such piers have been built in connection with harbours, bathing places, and the like. Fig. 290 shows a coaling jetty on the river Thames. 298 DAMS, DOCKS, HARBOURS & CANALS. Fig. 293. Lifeboat slipway at Ackergill. DAMS, DOCKS, HARBOURS AND CANALS. Concrete has been largely employed for heavy work in connection with rivers and the sea. Harbours and docks are built with huge monoliths or caissons and solid blocks of concrete. Noteworthy examples are the Admiralty harbours of Dover, Gibraltar and Rosyth, and the commercial harbours of Dover, Southampton and Liverpool. Fig. 292 shows one of the arms of Dover Harbour, constructed of huge concrete blocks. In the foreground stacks of reinforced concrete piles are to be seen. These piles were driven to serve as the foundation for new station buildings for the South Eastern and Chatham Railway. The piles -were .reinforced with helicallv wound steel rods supplemented by longitudinal steel bars on the Considere System. Fig. 293, a slipway, is a typical application to smaller works in this connection. For constructing huge dams concrete is also employed, as for example the Nile Dam. By reinforcing the concrete with steel great economies are effected in such constructions. In canals, too, concrete is largely employed, as for instance the Manchester Ship Canal and the new Panama Canal. Fig. 294 shows an example of its use for constructing a draw-in basin on a small canal at Bradford. Fig. 295 shows one of the dams in connection with i huge water- DAMS, DOCKS, HARBOURS & CANALS. 299 Fig. 294. Canal basin, Bradford. Fig. 295. Dam and hydro-electric power plant, Necaxa, 3/tirfco. 300 DAMS, DOCKS, HARBOURS & CANALS. Fig. 296. Caisson torpedo station. power scheme, which furnishes 50,000,000 horse-power to Mexico and El Oro. The dam, when completed, will have a height of 194 ft. Part of the hydraulic mains conveying water to the turbines for generating electric power are to be seen in the left hand bottom corner of the illustration. Figs. 296 and 297 illustrate a rather remarkable example of the pecu- liar structures which may be built of reinforced concrete. This is a caisson which was floated out as a pontoon or floating dock and sunk in the sea to serve as a torpedo station. Messrs. Schneider and Co., of Creusot, H.I87 Fig. 297. Diagrammatic section of torpedo station. DAMS, DOCKS, HARBOURS & CANALS. 301 desired to establish a station with a suitable area of water of fairly uniform depth for the purpose of torpedo trials. As a suitable site could not be found on the coast it was resolved to construct the station in the sea at some distance from land, and a position \vas found in the roads of Hyeres in the Mediterranean. The first proposal was to construct a large coffer-dam, but the difficulties were so great that as an alternative method, this large structure was built on shore in reinforced concrete and floated to its position. It measures 77 ft. 3 in. hy 55 ft. 2 in. and is 51 ft. high. On the top of the caisson was creeled a t vv o - fl o o r structure another 19 ft. 8 in. high with an overhanging portion. A room for experiments with tor- pedoes discharged under water is in the caisson itself, while the super- structure is used for test- ing torpedoes discharged above the water line. The structure, after hav- ing been towed to the Toulon roads by two tugs, was anchored to a buoy, and the internal concrete work consisting of the partitions then completed. Sufficient, concrete was then filled into the compartments to ensure stability during the operation of towing out to sea. Two tugs then towed it to its des- tination 25 miles away, in rough weather. A rock platform had been prepared and levelled for its reception by divers at a depth of 39 ft. 5 in., and when the caisson was placed into position above, water was pumped into the inner compart- ments until it sank and rested securely on its bed. The outer com- Fig. 298. The La Ccwlire Lighthouse, 302 LIGHTHOUSES. partments were then filled with concrete, and the middle ones with sand, this arrangement permitting of its removal at any future time by taking out the loose ballast from the central compartments. LIGHTHOUSES. Fig. 298 shows a reinforced concrete lighthouse erected upon the Point de la Coubre, on the north side of the mouth of the river Gironde. The height of the fecal plane is 192 ft. above sand level, or 203 ft. 6 in. above the foundations. The ground is about 18 ft. above high water. The internal diameter of the shaft is about n ft. 6 in. The thickness of the walls \aries from 5 ft. 10 in. at the base to 2 ft. 3^ in. at the top. The floors inside the light- house are formed of reinforced c .ncrete. Fig. 2;;o shows another lighthouse which wa> con- structed in reinforced concrete in the Straits of Malacca. The focal plane in this case is 02 ft. 6 in. above high water level . ; the lighthouse is ex- posed to the full severity of the monsoons, and the work of construction was arduous because of rough weather. As is shown, the base of the structure consists of rein- forced concrete piles 17 in number. The piles entered a depth of 26 ft. 8.] in. into the sand when a hard bottom was reached and were sunk by means of a water jet. SHORE PROTECTION V GROYNES. For protecting our shores against the erosion of the sea, groynes and the embanking of the shore have been executed for many years past of concrete. It is recognised as the best material for a permanent protection. The des- tructive force of the sea is. however, at times so great that unless the work consists of great monoliths it is not strong enough: We have often heard of concrete sea walls and groynes being washed away in severe storms. Reinforced concrete appears to offer a solution of the difficulty. Fig 300 illustrates part of the work of widening the promenade between the South Shore and the North Pier, Blackpool, including the Fig. 299. One-Fathom Bank Lighthouse, Straits of Malacca. SHORE PROTECTION & GROYNES. 303 Fig. 300. Sea icaJJ and promenade, Blackpool. provision of esplanades and a substantial sea wall for a length of about three miles. The sea wall varies in height between 26 ft. and 37 ft. and is n ft. thick at the base. At the toe of the apron, which has a slope of i to i, ring piles are driven 12 ft. apart, to which the permanent walling and sheeting piles arc secured. The apron is formed of consolidated sand, covered with a layer of concrete 2 ft. 6 in. thick, and faced with basalt grouted and bedded in cement mortar. On part of the front tiers of concrete seats have been built. Fig. 301 shows a sea wall at West Hartlepool reinforced with sheets of expanded metal, strengthened at points with concrete but- tresses, which are also reinforced with expanded metal. Fig. 302 shows the work in course of construction with sheets of expanded metal in position and the men at work surfacing the concrete. The sea walls act as retaining walls ; the slope, however, is merely the coating for the shore, which is sloped to the natural surface that is capable of being stable. This would not be so, however, if the sea could wash against it and erode the surface, in which case the concrete is reinforced with sheets of expanded steel. Fig. 303 shows some other sea defence works, at Teignmouth, in which the erosive action of the sea is prevented by a toe to the wall, and it should be noted that if the filling material underneath the work or lower esplanade should sink by the filtration of water under it and the construction of the sand, the esplanade would not fall because it is reinforced like a floor, to stand firm on its supports of mass concrete. The view shows a section through the slipway, down which boats can be run into the water. This slipway would serve for the lifeboat, and is an alternate method to that shown in Fig. 293. Fig. 306 shows a dyke and shore protection in Holland, consisting 304 SHORE PROTECTION & GROYNES. CROSS SECTION SEATON END OF WALL. ~^'1 -/ -V :'".';''' '* V ' ." ', *.;'.' ' " r '" : - -'''^ 9-0" > L.{ PLAN. SECTION AT AB fig. 301. 6't'l di fence wottft Ictiveen Scqton Curew and West Hartlepool. SHORE PROTECTION & GROYNES. 303 Fig. 302. Slope protection at West Hartlrpool. 306 SHORE PROTECTION & GROYNES. /6'Concrete / NtO Expanded S\eel Filling SECTION THROUGH TERRACE. WlOExpanded Steel SECTION THROUGH APRON PIECE. 13' 6"- WIOExpanded Steel-. F i I I i n g- SECTION THROUGH SLIPWAY. Fig. 303. Sea dejence works, Teignmouth. (Promenade, slipway and apron.) SHORE PROTECTION & GROYNES. 30? of a slab with ribs or beams to hold it down, also reinforced with expanded metal. Fig. 305 shows a reinforced topping to a dyke wall in Holland. The wall was built in pieces with heavy buttresses at the intervals. The independent nature of the work thus assured is an advantage. I''v 34 shows a novel application of reinforced concrete to the H D A- Fig. 304. Foreshore protection, Tilbury. 308 SHORE PROTECTION & GROYNES. Fig. 305. Topping to a dyke. protection of sea shores consisting of facing with concrete slabs with flanges which are held down by other concrete slabs in which are placed concrete keys somewhat like a nail. In employing this protection, the foreshore or bank is graded to an even slope with a maximum inclination of about 30 degs. If necessary a clay face is formed on this, or in particularly unstable material the bank is faced with straw or other facine work. The slabs with the flanges are then laid, and are about 2\ in. thick and 8 in. square ; the alternate slabs are without fig 306. Dyke and shore protection in Holland. flanges, but have a corresponding rebate, and are the same thickness ; they have a taper hole in the centre through which a long reinforced concrete key is driven holding it firmly to the face of the bank. Should any slight settlement in the bank occur the facing accommodates itself to the new contours. The example of work shown is on the foreshore of Tilbury. CONCRETE ON THE RAILWAY. Concrete is now employed very extensively upon railway works, and among other applications may be mentioned the construction of station platforms, treatment in this way being shown in Fig. 308. The platform can be built of mass concrete of weak proportions, such as I part Portland Cement, 3 parts sand, and 6 parts broken stone or shingle. Train sheds are often built of reinforced concrete consisting of low arched short span, longitudinal roofs, just high enough to clear the largest locomotive in use on the line, with smoke ducts of reinforced CONCRETE ON THE RAILWAY. 309 concrete through which the locomotive gases are discharged into the open air ; these smoke ducts being built high enough to prevent driving rain or snow from reaching tha platforms. Fig- 37 shows a combination coaling and sand station. The elevated coal bunker has a capacity of 260 tons of coal, and on the ground is a wet-sand store-house, and up above an elevated dry-sand bin. The coal is brought on a side track and elevated by a bucket conveyor into the bunker ; it is fed to the engine tenders through hinged gates and shoots. The wet sand is dried and elevated in the same way into the bin, and is fed to the engines through spouts. Engine sheds or round houses are now commonly constructed of reinforced concrete which is durable and fire-resisting, and Fig. 309 shows a reinforced concrete signal box. Terminal buffers are also constructed of reinforced concrete, and this material is specially applicable to the construction of large buildings such as power stations, fitting shops, warehouses, grain elevators, storage reservoirs and tunnels. Railway sleepers and telegraph poles are, of course, other applications in connection with railways, and are dealt with below. The round house shown in Fig. 310 is situated on the Santc Fe Fig. 307. Cool and sand station, N. and W. Railway. 310 CONCRETE ON THE RAILWAY. fig. 308. Cohoes station and platform. Fig- 309. Signal bo*. CONCRETE ON THE RAILWAY. 3! r 312 CONCRETE ON THE RAILWAY. Detail of Plugs. Fig. 311. Italian railway sleeper. CONCRETE ON THE RAILWAY. 313 -WTO *- ~ c 1 c to e> i . 1 T- 1 I 1 s L L r \ \ i P i r I Detail of Plug. Fig. 312. Italian railway flccper. 314 CONCRETE IN MINES. Railway, United States. It is supposed to be one of the largest struc- tures of the kind in America. It measures 850 ft. by 94 ft., and has 35 stalls, each stall being 92 feet long, divided into two sections so as to give an inner and outer circle. The exterior, walls are 7 in. thick, and the beams and roofs are of reinforced concrete, as also the footings, columns, walls, of ring pits, engine pits, and drop wheel pits. RAILWAY SLEEPERS. Figs. 311 and 312 show examples of railway sleepers, which are now being made in reinforced concrete. Concrete railway sleepers have been tried for a number of years by a few people and found to be thoroughly satisfactory, and at the present time a great many experiments are being made by railway companies. Every vear the scarcity of timber suitable for the purpose is getting greater ; its cost is a large item and its life is short. There is little doubt that before many years have passed we shall see all railway sleepers of reinforced concrete. The sleepers illustrated are being used extensively on (he Southern Italian railways, no less than 100,000 of the type illustrated being ordered by the Italian Government in one year. The reinforcement consists of round iron rods arranged longi- tudinally in two layers, bound together by iron wire ; pieces of iron gauze are inserted in the middle of the ties and under the chairs ; vertical rods are also placed underneath the chairs. CONCRETE IN MINES. Reinforced concrete has, for reasons similar to those given above, been adopted in mines for the lining of shafts, bearers for rails and for strutting and pit props. Fig- 3 T 3 shows some of the applications of reinforced concrete in mines in substitution for timber construction. This is the plan adopted in some mines in America. The revetments in these mine galleries were executed in sections about 5 metres long by the aid of timber moulds. The reinforcements consisted of ordinary steel rods placed horizontally and vertically. The walls were first concreted between centering, and the concrete for the roof packed in gradually as the centering was brought along. Some- times, where it was desired to secure very careful packing of the roof, cement grout was forced through tubes embedded in the arched rein- forced concrete roof, formed as before, so as to fill any fissures or spaces existing between the outer face of the concrete and the earth. Fig. 315 shows a gantry for the conveyance of coal from the pit head to the screening house and from thence to the railway siding. The coal is raised in trucks which travel on rails in the runways by gravity for a distance of 80 ft. Fig. 316 is another interesting application of concrete to mines, being a bird's-eye view of the various gantries, bunkers, and pithead structures at a colliery 'in the Pas-de-Calais district. The high building on the right hand of the view contains the various bunkers. Fig. 317 shows a series of reinforced concrete shelves z>nd switch-board for thp distribution of the electric current a{ this same mine, CONCRETE IN MINES. 315 -SECTION OF CONCRETE SHAFT LINING AT BRIDGEPORT ' COLLIERIES. PENNSYLVANIA. -SECTI IN ROADWAYS. -SECTION OF CONCRETE STRINGER AT AHMEEK MINE . MOHAWK. MICHIGAN. 1 c c a $ ^ f$& IV n H.I 6? ..PLAN SHOWING CONCRETE USCD IN PLACE OF TIMBER < IN ROADWAYS. fe Seo/e. 8 Feet to 1 Inch. SECTION OF CONCRETE STRINQE. MICHIGAN. : 1 Foot to 7 IncH. j^ , fl( j Fig. 313. Concrete in 316 CONCRETE IN MINES, CONCRETE IN MINES. 317 316 CONCRETE IN MINES. CONCRETE IN MINES. 319 Fig. 317. Shelves and FwUrhlionrdf. Cm-.-.-prtgnie dcs Mines dc Hovilie dc Marias. -PILLAR OF CONCRETE AT INTERSECTION OF THREE ROADWAYS. 'j,^-;:^-^.,;.:^^ 318. Concrete in minea. 320 SOME UNCOMMON USES OF CONCRETE. TELEGRAPH POSTS, RAILWAY AND ELECTRIC LIGHT STAN- DARDS, SIGNAL POSTS AND NAME AND NOTICE BOARDS. Fia. 319. Reinforced concrete telegraph pole. FOR all these purposes concrete is now- adays being used. Fig. 319 shows a tall telegraph pole, Fig. 320 an electric light standard, and Fig. 321 a mast in which reinforced concrete is found to be very economical. To obtain timber suitable for such purposes is somewhat difficult. Further, timber is liable to decay. The cost of concrete is very little more, and it is practically everlasting. Attempts have been made for many years to increase the life of wooden poles and posts by the adoption cf various expedients, and though they have been successful in extending the life to about 16 years, that is far too short to be at all convenient, and in many tropical countries timber cannot be used owing to its being eaten by ants or damaged by animals. The iron post has therefore been found econo- mical, atid in many cases the only thing possible of adoption. It, how- ever, required constant attention and repainting. Numerous suggestions have been put forward from time to time for using concrete for the construc- tion of posts, and some work has been done with solid reinforced concrete poles, but their great weight was a disadvan- ELECTRIC LIGHT STANDARDS. 321 tage. Attempts to make a hollow concrete pole were unsuccessful until the last few years, but -it is now possible to obtain them of great length and strength and at a very great economy compared even to iron. Electric light standards in concrete compete not only with timber but with iron. They are economical in first cost and do not require painting, while their appearance is certainly superior. Hollow concrete masts for carrying electric wires are now made in London. These are reinforced with longitudinal wires and binding wires and the concrete is wrapped upon them by a special machine of a very ingenious character. They are of great strength. The machine while wrapping the concrete applies a spiral binding of wire at the same lime round the steel collapsible mould upon which are strapped the longi- tudinal reinforcing bars. The concrete is compressed on the mould, and is kept in place temporarily by a wrapping of webbing or cloth that is fed on with the Fig. 319 illus- pole made by this Fig. 320. Reinforced concrete electric light standard. concrete, trates a method. Fig. 322 shows some different types of reinforced concrete telegraph poles that have been erected in Den- mark. In connection with poles or posts for supporting tele- graph or other wires, we may note that reinforced concrete posts and supports have been employed to sus- tain the wires of rope con- veyors carrying sand or other materials. Fig. 323 shows the starting station with the bucket hanging on the wires, and a view of the support for the wires midway between the starting and receiving stations. Fia. 321. Reinforced concrete mast. 322 AERIAL TRANSPORTERS. RIFLE RANGES. 323 324 SHIPBUILDING & PORTLAND CEMENT. Reinforced concrete has been applied to the construction of large ele- vated advertisement boards. They can -be moulded on the ground and hoisted into posi- tion, or constructed in situ. Fig. 324 shows a large reinforced concrete rifle range at Ostend. The height of the targets is 41 ft., and they are 7 in. thick. The supports of the targets are of rein- forced concrete, as are also the targets them- selves. The other uses of concrete suggested by the heading to this section require no explanation. SHIPBUILDING AND PORTLAND CEMENT. Portland Cement is largely used for lining JF.,322. Telegraph and electric poles. ships R . g inadvisab to allow water, however small in quantity, to lie in the bottoms or iron or steel ships, or to permit crevices to remain that can get filled with refuse or dirt which may absorb moisture, for then destruction in time by corrosion can only result. Certain cargoes, too, have an injurious effect on iron or steel by chemical action. The insides of steel ships are therefore, nowadays, lined with Portland Cement. The plating and rivet heads, as well as the frame flanges are practically buried under a layer of Portland Cement, and the floors and keelsons are well covered with cement wash. Even with the double-bottomed vessels it is recognised that water would drain itself through and cause damage, so that Portland Cement is used for treating the bottom plating, rivet heads, floors, angles, intercostals, etc. Next in importance to the bottom in a double- bottomed ship are the bilge and water courses, for which cement is largely used ; the shell, tankside angles and bracket angles are also well covered, the cement making it possible for the water to run freely through the drain holes in the bracket plate. In cases where wells SHIPBUILDING & PORTLAND CEMENT. 325 are used to drain off the bilge water these are thoroughly treated with cement. The bottom plating, lower parts of floors, frames and other portions in ballast tanks, and bilges, and wells are also treated with cement, and often, instead of using paint for the internal parts of fresh water tanks, a good cement coating is used. Wherever it is possible for moisture to accumulate, such as in the double-bottom floors under the boilers, engines, hold tanks, and tunnels, a cement covering is employed. Cement is used for gutter waterways, and between the shell^ and stringer angle bars between decks, and where frames are run up through the decks the spaces are filled in with it. As we have pointed out elsewhere in this volume, from the point of view of hygiene, there is advantage in using cement where cattle are to be accommodated ; it is therefore not surprising to find it exten- sively used in steamers engaged in the transport of cattle, for covering the decks, etc. Cement is also applied to the bosses of propellers when loose blades are used, the nuts, and the propeller or tail shaft nut being covered. Generally neat cement is not applied, but cement mortar made of a mixture of equal parts of cement and sand or of i of sand to 2 of cement, or of i of cement to 2 of sand, according to the purpose for which it is required or the experience of the user. Neat cement is sometimes placed on the bottom of oil tanks in oil tank steamers after they have been tested, and is usually applied about i in. thick. Portland Cement though employed in the above mentioned con- struction of ships, is also largely used for ship repairs. It is found to be very useful in the temporary but effectual stopping of leaks ; there are numerous cases of damaged vessels being brought home safely by the use of Portland Cement, and two instances will suffice. One occurred a few years .ago on the Hooghly river in India ; a sailing vessel went aground and damaged her bottom rather extensively, the plating being corrugated almost right fore and aft, with a resufi that she was found to be leaking badly. To stop this and to enable the vessel to be brought home for repairs a covering of Portland Cement was laid completely over the bottom of the ship on the inside, the thickness graduating from 12 in. at the middle to about 4 in. at the sides. A cargo was then put aboard, and when the vessel arrived in this country she was docked and repaired. Very bad weather was experienced on the passage home, yet in spite of this the cement had kept the cargo entirely free from water, and when the cement came to be removed to enable the work of repairing the bottom to be pro- ceeded with, it was found not to be an easy matter. The second instance was in the case of the " Wingfield " when she collided with the " Mexican," the former being engaged in transporting Yeomanry to the Cape during the late war in South Africa. The " Wingfield " was so badly damaged that the fore end was completely stove in. Temporary repairs by filling in the forepeak solid with Portland Cement were effected at the Cape, to enable her to come to this country for permanent repair, and the passage was safely carried out. It has been found in many cases very difficult to repair vessels which have sustained underwater damage when alongside a wharf, 326 BOATS, BARGES & PONTOONS. particularly when they have been partially loaded, but in such instances Portland Cement has been found a most satisfactory remedy. A square has been formed round the damaged portion the depth of the spar ceiling and cement run in. A somewhat novel application of concrete, but only typical of ^he many similar uses to which the material can be advantageously put, is shown in Figs. 325 and 326. The former illustration refers to the old type of anchor which fishermen used to use off the coast of Denmark for keeping in position the nets, particularly those for catching eels. It will be seen that the anchor takes the form of a heavy stone held between branches of willow. The new type of anchor, however, was an arrangement devised some time ago by one of the fishermen on the coast of Zeeland, and consists of a block of concrete with projected angle irons as shown in Fig. 326, the cost of which worked out to about is. These anchors are cast by he fisher- men themselves. BOATS, BARGES AND PONTOONS. One of the most novel and striking applications of reinforced con- crete is found in its use for boats, barges and pontoons. Figs. 328 and 329 show such examples on the River Tiber at Rome. BRANCHED Or WILLOW HEAVY 5TDME EYE BOLT BLOCKoF-CONCREJE .EMENTAND5ANDJ Fig. "6-25. AN6LE IRON OR 1$ 1 IRON ABOUT M" y Fig. 326. . 325 and 326. Anchors used by fishermen off Denmark. BOATS, BARGES & PONTOONS. 32? Barges and pontoons built in reinforced concrete are advantageous inasmuch as they are quickly and easily constructed at small cost in comparison with ordinary methods. Such vessels are subject to rough usage, but their monolithic construction gives a high power of resist- ance. They also have the advantage of being fire-resisting. Their smooth surface offers but slight resistance to water, and weeds cannot easily adhere to it. The usual scraping and any repairs are executed without much difficulty or expense. The cost of construction as com- pared with steel barges or pontoons is estimated at about one-half, and the cost of maintenance at about one-fourth or one-third. In many places in the country such pontoons might be used for ferries, while house-boats of reinforced concrete should be found highly advantageous. Fig. 328 shows a concrete barge constructed in Italy ; it was built for towing purposes. The details of the construction are shown in the diagram. The concrete used was composed of 3 parts |-inch coarse material, i parts sand, and i^ parts Portland Cement. This barge was built in 1906, since when it has been in constant use for coal traffic. It has a carrying capacity of 150 tons, and is still giving satisfaction. Figs. 327, 330 to 333 require no descriptions further than those under the illustrations. CONCRETE FURNITURE. 1'ig- 334 illustrates a moist closet made of " waste-cement " left from a testing all brands mixed and several samples of natural sand from the same source. The mortar was mixed i to 2 and wet enough to be readily filled and tamped in a f in. space. The walls are ij in. thick, except the centre panels of the doors, which are only ^ in. thick. Fig. 327. Floating dock at Qwensboro. 326 BOATS, BARGES & PONTOONS. Fio. 328. A reinforced concrete barge. Fig. 329. A reinforced concrete pontoon. BOATS, BARGES & PONTOONS. 329 330 BOATS, BARGES & PONTOONS. BOATS, BARGES & PONTOONS. 331 332 BOATS, BARGES & PONTOONS. CONCRETE FURNITURE. 333 The walls are reinforced with in. mesh galvanised wire netting. The hinges were specially designed to be embedded in the walls and doors. The forms consisted of an outer box without top or bottom and two inside forms or cores, or boxes with tops and no bottoms. The space between the outer and inner forms was 13 in. The doors were cast first by filling in a frame of the proper dimensions, laid on a pane of glass, and oiled to form a flat surface. The hinges were placed rightly by the help of marks on the frame and secured to it by small brads before the mortar was filled in. The same form answered for the two doors by simply reversing the position of the hinges. When hard enough to withstand handling, the two doors were placed in their proper relation face down on a flat surface and the outer box form placed around them. The edges of the doors were covered with several thicknesses of oiled paper and the Portland Cement mortar was filled in around them level with the doors, making the layer of mortar just 15 in. thick. The inside forms were immediately placed in position, open end down, and supported by the doors, which were sufficiently hard. They reached to within ij in. of the top of the outer form, and there was an open space of 15 in. around each core. The mortar was then filled in and around these cores and smoothed off even with the top edge of the outer form, this top layer forming the back of the closet. The reinforcement, of course, had to be placed in position before filling in, the wire being kept in position in the middle by strips of 5 in. board, which were moved along or taken out as the mortar was filled in. Cleats for the shelves were allowed for by providing longitudinal strips on the sides of the core boxes, in widths equal to the distance desired for the cleats. Extensive improvements have been effected at Aberdeen Harbour, including the erection of about a mile of walls. In connection with the engineer's department, there is a very complete laboratory for testing cement, and Figs. 336 and 335 show some re- inforced concrete furni- ture therein. The first example is a table for office use, and the other a moist cabinet for the storage of cement bri- quettes before testing them to ascertain their tensile strength. Inside the cabinet are rein- forced concrete trays containing the briquettes immersed in water. The cabinet is composed of Portland Cement, granite and sand, and Fig. 334. A reinforced concrete moi$t closet. 334 CONCRETE FURNITURE. MISCELLANEOUS. 335 I'ig. 336. 'I'abie in laboratory, tony inverts' Department, Aberdeen Harbour. reinforced with ex- panded metal, the walls being i in. thick, and the bottom i| in. thick; the doors are i in. thick with panels | in. thick, and the trays are in. thick. The table is reinforced with 5 in. steel rods and expanded metal fastened together with wires. MISCELLANEOUS. Concrete black- boards are now being put into many schools. They are a consider- able improvement ever other materials, even slate. The blackboards are formed either upon the ordinary brick or concrete wall or upon a metal lath on battens. While the undercoat is still green, the surface finish is trowelled on with neat cement paste mixed with very finely divided carbon black pigment. A smooth surface is thus obtained which consumes little chalk and to a great extent eliminates chalk dust. An important feature is that it presents an absolutely dead finish without reflection, making it possible to see whatever is on the board from any angle of the room. Tombstones and burial vaults are now frequently constructed in concrete. It is sometimes stated that Portland Cement mortar used for jointing stains marble tombstones. This may be due to some chemical action which frees the iron in the cement, and in course of time the iron ixide so released is precipitated on the marble. For such purposes a cement with little if any iron in it should be used, and such cement can be obtained. Fig. 337 illustrates a monumental statue at Espaly, near the town of Puy, France, built at the summit of a basaltic rock. The pedestal and figure are hollow, the former containing galleries and staircases. The statue is 48 ft. 6 in. high from the platform to top of head, making the total height of the monument 72 ft. 9 in. The statue was cast in pieces and joined together in situ and sustained by a reinforced concrete framework. The joints are not noticeable and the statue looks as though it were one huge block of stone. 336 MISCELLANEOUS. Fig. 337. Statue at Espaly. 33? MEMORANDA FOR CONCRETE USERS. SOME GENERAL NOTES. i ton of Portland Cement = 10 sacks of 2 cwts. (224 Ibs. nett) each; or n sacks of 204 Ibs. nett each; or 12 sacks of 187 Ibs. nett each. i c. ft. of Portland Cement weighs from 75 to 85 Ibs. When loosely filled in without any shaking, and about no Ibs. when tightly packed. The Royal Institute of British Architects advises the adoption of 90 Ibs. as the basis of comparison in converting from cubic feet to Ibs. for propor- tioning concrete. This has also been adopted as the standard by the London County Council in their regulations for reinforced concrete construction in London. i c. ft. = .037 c. yds. = 1,728 c. in. i c. yd. = 27 c. ft. = 46,656 c. in. = i load, i ton = 20 cwts. = 2,240 Ibs. = 35,840 ozs. i gallon of water = 10 Ibs. = .16 c. ft. = 277.46 c. in. Minimum specific gravity of Portland Cement required by British Standard Specification is 3.15 at works and 3.10 4 weeks after gauging ; in determining proportions of concrete we have assumed the average specific gravity to be 3.12. i c. ft. of fresh water weighs 62.4 Ibs. = 6.23 gallons .037 c. yds. i c. ft. of salt water weighs 64 Ibs. = 6.23 gallons. Average weight of i 12:4 concrete : coke-breeze as coarse material 100 Ibs. per c. ft.; clinker no Ibs. per c. ft.; brick 125 Ibs. per c. ft.; limestone 135 Ibs. per c. ft.; shingle as coarse material 145 Ibs. per c. ft. Average weight of 1:2:4 reinforced concrete 150 Ibs. per c. ft. i ton = 21 c. ft. river sand = 22 c. ft. pit sand = 22 c. ft. ballast = 23 c. ft. coarse gravel = 24 c. ft. clean shingle. z 338 MEMORANDA. An average wood wheel-barrow is made to contain -L c. yd. of heaped wetted material. Average load of broken stone or ballast for wood wheel- barrow = 2.4 c. ft. Average load of sand for wood wheel-barrow = 2.5 c. ft.' Large load of broken stone or ballast for average iron wheel-barrow = 3.0 c. ft. Large load of sand for iron wheel-barrow = 3.5 c. ft. Average load of ordinary concrete (rammed) for iron wheel- barrow = 1.9 c. ft. Large load of concrete for iron wheel-barrow = 2.2 c. ft. Average net time of one man filling wheel-barrow with concrete = ij min. Average quantity of concrete mixed, wheeled 50 ft., and rammed, per man per day of 8 hours = 1.76.0. yds. Approximate percentage of strength of concrete at different ages in comparison with the strength at i year : 28 days old, 60 per cent. 2 months ,, 75 ,, 3 85 4 9 j> 6 95 >> i year ,, 100 ,, CRUSHING. The resistance of concrete to crushing varies with the grading of the materials (i.e., the percentage of voids), with the character and size of the coarse material and sand, the amount of ramming to which the concrete is subjected, the quantity of cement, the amount of water used in mixing, the curing, and the age. With so many factors involved it will be seen that it must be difficult to obtain anything like uniform results in actual practice, and to reach the highest stresses it is necessary to have the right material properly graded and tested under laboratory conditions. The requirements of the London County Council and the specification drawn up by the Joint Committee on Reinforced Concrete (which was comprised of representatives of the following bodies, viz., Royal Institute of British Architects, District Surveyors' Association, Institute of Builders, MEMORANDA, 339 Institute of Municipal and County Engineers, War Office, Admiralty, London County Council, Concrete Institute) call for a crushing resistance of 1:2:4 concrete to be i, 800 Ibs. at 28 days and 2,400 Ibs. at 90 days. The following figures give the results of a series of tests made by Mr. William G. Kirkcaldy on a mixture of identical materials under the various conditions described : - Proportions : 4 c. ft. Thames shingle (passing f in. mesh and retained on J in. mesh), 2 c. ft. sand (25 per cent, passing J in. and retained on J in. mesh, 75 per cent, passing J in. mesh), i loose c. ft. " Ferrocrete " cement = 76.2 Ibs. Percentage of voids in shingle, 41.3; coarse sand, 40.5 ; fine sand, 29.1. Age Age 28 days. 90 days. Ibs per Ibs. per Mixed fairly wet (as in practice), water added 53-75 Ibs. Mixed fairly dry (not rammed), water added 45 Ibs. Mixed fairly dry (rammed), water added 40 Ibs. Mixed very dry (rammed), water added 35 Ibs. sq. in. Not sprinkled 1026 Sprinkled with water every other day for first three weeks ... 1118 Not sprinkled 1718 Sprinkled ... 1668 sq. in. 1787 1789 2440 Not sprinkled Sprinkled ... Not sprinkled Sprinkled ... 2018 2032 2225 2078 2914 3159 33U 3554 These variations are not in any way exceptional, but are borne out by our observations on tests carried on from time to time in our own laboratories. For 1:2:4 concrete it would appear, therefore, tha* as mixed on the job it should not be expected to reach such a high resistance as 1,800 Ibs. in 7 days and 2,400 Ibs. in 90 days, although such tests may be obtained with hard, well-graded coarse material tested under laboratory conditions. The character of the coarse material used must always be taken into consideration, but the figures of 1,400 Ibs. at 28 days and 2,000 Ibs. at 90 days 340 MEMORANDA. nearly represent the results obtained under normal working conditions with material such as Thames ballast. It should be borne in mind that at 90 days concrete does not by any means reach its full strength, but that there is .a steady increase of strength over a long period. Safe compressive strength of 1:2:4 concrete = 600 Ibs. per sq. in. Tensile strength of good 1:2:4 concrete about 150 Ibs. per sq. in. at 28 days. Safe adhesion strength of concrete to steel = 100 Ibs. per sq. in. of area of metal. Ultimate strength of mild steel in tension = 60,000 Ibs. per sq. in. vSafe strength of mild steel in tension = 16,000 Ibs. per sq. in. .78 c. ft. of stiff cement paste will result from mixing .35 c. ft. of water with i c. ft. of loose cement. i c. ft. of loose Portland Cement will make about : 4.1 c. ft. of concrete mixed 1:2 : 4 5 I 2 2 ' 5 5-8 >> I : 3 : 6 7-5 >> >> 1:4:8 i c. ft. of loose Portland Cement neat as cement paste will cover about 9.5 sq. ft. i in. thick. i c. ft. of loose Portland Cement to i Sand will cover about : 14.7 sq. ft. i in. thick. i c. ft. of loose Portland Cement to 2 Sand will cover about : 23.2 sq. ft. i in. thick. i c. ft. of loose Portland Cement to 3 Sand will cover about : 32 sq. ft. i in. thick. i c. ft. of loose Portland Cement to 2 Sand will lay about : 146 bricks with f in. joint, and 247 bricks with J in. joint. * c. ft. of loose Portland Cement to 3 Sand will lay about : 212 bricks with f in. joint, and 317 bricks with J in, joint. 11.5 c. ft. of rubble stone work. MEMORANDA. 341 i yd. super, of pointing brick work in neat cement requires about 8 Ibs. of cement. 100 Ibs. of Portland Cement and i c. ft. of sand will plaster : 2j sq. yds. i in. thick. 7 $ O 4 >J 4i > 2 100 Ibs. of Portland Cement and 2 c. ft. of sand will plaster : 3 sq. yds. i in. thick. 2 PROPORTION OF SOLIDS AND VOIDS IN VARIOUS COARSE MATERIALS. Aggregates. Solids Voids Sand, moist, fine, passing i8-mesh sieve '57 '43 (i.e. 324 meshes to the sq. inch) ,, ,, coarse, not passing i8-mesh sieve ... 65 35 ,, ,, coarse and fine mixed, ordinary 62 38 ,, dry, ,, ,, ,, ,, 70 30 Stone screenings and stone dust 58 42 Ballast, | in. and under, 6 per cent, coarse sand 6 7 '33 Broken stone, i in. and under '54 46 ,, 2\ in. ,, ,, dust only screened out '59 '4 1 ,, ,, 2, in. ,, ,, most small stones screened out '55 '45 342 MEMORANDA. ii oo co K o Tfob ^J~ vo coo si CO CO K o Tf co K CO Tf VO M pN ON Tf CO K Tf QZ if CO co coo do coo ""?" O f^i^O oo >o CN CO t-x O COO 00 COO < 3 CO N vo CO O COO OO COO CO CN Tf gCOO W a sl r/-\ _j _4 0000 00 00 t^ co CN io O O\ VO O to || OO o M CN Tf JJ COO 00 O CO Knio CO K O o .s3 CO t-i CS 00 COO O CO yo co t> io CJ Tf oo CO M (S o yo o cs h 10 h K *1 CJ VO ON | S * ON ON ON H .Tf rf coo Tf COO O b ii ONMCO CO vo CO O O co r< Tf vo vo (S M p CS CS Tf Q 11 00 CS CO yooq o M M CO 00 n ^ K. r-i CO 10 W j| O vo M O CO ON 00 M O CO OO ONOO oo t^ yo vo K CO | t-xOO ON \O ^" CS vo O VO M CO vo ON CS CO O O 5oo 172 257 i? 056 2-4 42 4,667 131 197 18 048 1-8 32 6,222 97 145 J 9 040 1*2 21 9.333 67 100 20 036 I 18 11,200 55 82 347 GLOSSARY. A;ration Aggregate ... Air slaking ... Baffle plate ... Battens Caisson Carbonic anhydride Centering Chamfer c. c. ... c. ft.... Forms Green Grout Hydraulic lime in situ ..see page n. ..see page 14. ..exposure of cement or lime so that it is able to absorb moisture from the air to enable the free lime to slake. ..a division that shoots off material until it strikes another surface, thus tending to churn the material. ..timbers of small width. ..a watertight compartment. ..carbon dioxide or carbonic acid gas, a compound of oxygen and carbon exhaled by animals and produced by combustion of coal and wood. ..horizontal forms, see " forms." ..to grind or cut off to a sloping edge. ..cubic centimetres. ..cubic feet. ..timber or metal work intended to serve as moulds or supports in or upon which concrete may be applied. These forms are usually removed when the concrete has hardened. ..the condition when concrete has not become thoroughly hardened and dried out, though it has taken its first set. ..see page 92. ..lime which has the property of setting though wet, i.e., without requiring to dry out or have access to air to harden it. ..constructed completely and directly in the final position, like a concrete wall built in between boards instead of being built of blocks ; or a pavement formed by laying the concrete on the ground, instead of putting down separately moulded paving slabs. Work moulded on the site is not necessarily in situ. 348 GLOSSARY. Initial setting Paddle Plumb Plums Puddle Ramming ... Random rubble Riser R.SJ.'s Scantlings Scr ceding Seconds or thirds Short Shuttering ... Slake Silo Soffit Stringer Stucco Sump Tamping Tread ..see page u. ..a "piece of wood shaped like the blade of an oar. ..exactly vertical, or perpendicular. ,.see page 39. ..to stir material which is in a slushy condition so as to work it into place, and to increase its solidity. ,.the operation of pounding concrete with a large rammer, to increase its solidity. ..a kind of masonry made of irregularly shaped pieces of stone roughly put together. ,.the vertical part of a step. ..rolled steel joists, .narrow pieces of timber. ,.see page 86. .qualities of any article inferior to the first. ..without tenacity, i.e., brittle, or easily pulverised. ..vertical forms, see " forms." .to change quicklime into an hydrated condition by the addition of water, .a bin to hold materials ; a term usually applied to bins for grain, .the under side of a beam, floor, or arch. ..the side beam-like support of a stair- case which carries the ends of the steps. .the fine finish of external plastering. ,.a sunken pit or receptacle to collect liquids, .the operation of poking concrete with a small rammer, rod, or other small tool. ,the horizontal part of a step. Some Notes concerning the Associated Portland Cement Manufacturers ( 1 900) Limited PROPRIETORS OF THE LEADING BRANDS OF ENG- LISH PORTLAND CEMENT 350 Portland House, Lloyds Avenue, London, E.C> Offices of The Associated Portland Cement Manufacturers (1900), Limited (The columns, beams, floors, roof, and stairs of this building are in reinforced concrete). 351 SOME NOTES CONCERNING THE ASSOCIATED PORTLAND CEMENT MANUFACTURERS (1 900) LTD., PRO- PRIETORS of the LEADING BRANDS OF ENGLISH PORTLAND CEMENT. IN the year 1900 the Associated Portland Cement Manufacturers (1900), Limited, was formed, consisting of the following twenty-four firms or Companies engaged in the manufacture of Portland Cement, amongst which were included the oldest established and best known in the world : JOHN BAZLEY WHITE & BROTHERS, LTD. HILTON, ANDERSON, BROOKS & CO., LTD. KNIGHT, BEVAN & STURGE. FRANCIS & CO., LTD. ARLESEY LIME AND PORTLAND CEMENT CO., LTD. BURHAM BRICK, LIME AND CEMENT CO., LTD. LONDON PORTLAND CEMENT CO., LTD. GIBBS & CO., LTD. ROBINS & CO., LTD. W. TINGEY & SON. LAURENCE & WIMBLE. BOOTH & CO., LTD. WOULDHAM (MEDWAY) CEMENT WORKS CO. CHARLES FRANCIS, SON & CO., LTD. NEW RAINHAM PORTLAND CEMENT CO., LTD. IMPERIAL PORTLAND CEMENT CO., LTD. BORSTAL MANOR CEMENT CO., LTD. TOWER PORTLAND CEMENT CO., LTD. HOLLICK & CO., LTD. PHCENIX PORTLAND. CEMENT CO., LTD. WESTON & CO. McLEAN, LEVETT & CO., LTD. MACEVOY & HOLT. WILDERS & GARY. 352 The history of many of the afore-mentioned businesses is full of interest to those concerned in the Portland Cement industry. The firm of John Bazley White & Bros, was originally founded in 1805, a full century ago, and after the invention of Portland Cement in 1824 by Joseph Aspdin they took up the manufacture from the very outset at Swanscombe. it is there that the " J. B. White & Bros." brand is still produced, and these works have now become the largest and most important for this manufacture in Europe. In close proximity are the works at Northfleet at which the younger Aspdin began to manufacture the article. They were owned for many years by Messrs. Robins & Co., Limited, and passed into the hands of the Associated Port- land Cement Manufacturers (1900), Limited, in the year 1900. Almost adjoining, also at Northfleet, is the large manufactory established in the year 1853 by Messrs. Knight, Bevan & Sturge, whose " Pyramid " brand is known all over the world, and that of the London Portland Cement Co., the manufacturers of the " Lighthouse " Brand. On the Essex side of the river are the works of Messrs. Brooks, Shoobridge & Co., and Messrs. Gibbs & Co., both cf which were founded more than thirty years ago, and whose pro- ducts meet with great favour in numerous markets both at home and abroad. The works formerly owned by Messrs. Francis & Co., at Cliffe, are amongst the very oldest in the trade. On the Medway the most notable works are those which originally belonged respectively to : Messrs. Hilton, Anderson & Co., the Burham Brick, Lime and Cement Co., Limited, the Gillingham Co., Messrs. W. Tingey & Son, the Phoenix Portland Cement Co., etc. Of these firms the first began their operations at Faversham as manufacturers of Roman Cement in the year 1816, and subsequently em- barked upon the manufacture of Portland Cement at Upnor in 1849, and at Hailing in 1878. In the immediate neigh- bourhood of the properties above referred to lie most of the Associated Company's remaining works, with the excep- tion of the manufactories at Arlesey in Bedfordshire (" Eddystone " brand) and the Vectis works in the Isle of Wight, formerly owned by Messrs. Charles Francis, Son 353 a 11 AA 354 & Co., from both of which a large and increasing trade is done in the Midlands and in the South of England. At its Thames and Medway works the Company pos- sesses the finest raw materials in the world, in quantities sufficient to last for many generations to come. The prac- tically unvarying composition of these materials accounts largely for the reputation which all these brands, now controlled by the Associated Company, have achieved in the home, the colonial, and the foreign markets of the world. It is true that of late years the production of Portland Cement has attained large dimensions in some countries outside the United Kingdom, but none of these possess natural advantages equal to those of the Thames and Med- way district, which alike by seniority and suitability has been rightly described as the cradle of the industry. The Associated Company's properties in the valleys of the Thames and Medway alone cover approximately 4,000 acres. Its river frontages are more than nine miles in length, and a fleet of over 200 vessels, consisting of steam tugs, lighters and barges, owned by the Company, is daily plying to and from its numerous docks and wharves for the transport of materials and manufactured products. Several of the works have equally good facilities for delivering by rail and by water. Central foundries and engineering shops have been erected at Northfleet for the Thames, and at Frindsbury, near Rochester, for the Medway districts. There it is that repairs to machinery and additions to plant which cannot conveniently be carried out at the numerous local workshops are promptly executed. The cask-making machinery at the Company's Cooperages is capable of turn- ing out, chiefly for export, upwards of three and a half mil- lion barrels a year. The greater part of the Portland Cement for the home trade is supplied in sacks. At the numerous factories every approved method of mixing the raw materials, and of burning and grinding the Portland Cement, may be seen in operation, and any new process likely to lead to improvement in quality or to economy of production, receives the most careful examination of the Company's experts. As an instance of this may be cited the radical change in the mode of burning Portland Cement clinker by means of rotary kilns, which was introduced a 355 few years ago and is rapidly superseding older methods. This new process has been adopted by the Company at the cost of a very large sum of money, and is in urc for the production of nearly 900,000 tons of Portland Cement annually at the works formerly owned by Messrs. John Bazley White & Brothers, at Swanscombc, Messrs. Knight, Bevan & Sturgc, at Northfleet, the Arlescy Lime and Port- land Cement Company, Limited, at Arlese>, the Burham Brick, Lime and Cement Company, at Aylesford, and Charles Francis, Son & Co., at the Isle of Wight. At Gravesend the central offices and laboratory are in telephonic communication with each of the works, and their respective laboratories and testing rooms, whence daily reports of chemical and other tests are received and regis- tered. There is constant communication between every department and the London offices, at Portland House, Lloyds Avenue, E.G., where the whole of the sales, finance, and general organisation arc controlled. The ability of the Company to undertake contracts of every degree of importance is unquestioned, and has been proved on many occasions in the past ; for instance, by the satisfactory way in which they carried out contracts en- trusted to them by the respective contractors for the Admiralty Docks at Gibraltar, the new waterworks for the Birmingham Corporation, the Royal Edward Dock at Avon- mouth, and the Barrage and Dam Works on the Nile, Docks at Rosyth, Southampton and Swansea, in connection with which important contracts the company supplied approximately 700,000 tons of Portland Cement to the satisfaction of all concerned. Large stocks of matured Portland Cement are stored at various points and prompt delivery can always be belied upon. The development of reinforced concrete as a construc- tional material is naturally being watched with the greatest interest by the Company, and in order to provide a specially finely ground Portland Cement which shall give the best results for this purpose, new grinding plant has been in- stalled in its leading works. Furthermore, a superfine Portland Cement is being produced under the name of *' Ferrocrete " for the use of concrete specialists. It is being extensively employed by the leading Concrete con- 356 tractors in the United Kingdom, particularly for reinforced concrete work. The Company is itself in many instances adopting reinforced concrete at its works and depots, and for a variety of purposes. The large loading pier at the Swanscombe works of J. B. White & Bros., for instance, is entirely built of this material, and many other cases may be mentioned, such as the large new warehouse at the Lon- don depot, Grosvenor Road, Pimlico ; chimneys at the Northfleet Works ; clinker and coal-hoppers at other works ; and it was employed on a considerable scale in the erection of the new oflices at Lloyds Avenue, Fenchurch Street, London, E.G. The Company employs fully 6,000 people, and the annual capacity of its works is approximately ONE AND A HALF MILLION TONS or over TEN MILLION BARRELS per annum. THE EVERYDAY USES OF PORTLAND CEMENT (THIRD EDITION/ Mr. lessrs (Name] ...(Occupation) (Address) a herewith request the Associated Portland Cement Manu- S faclurers (1900), Limited, to forward when issued (free) a o 3 copy of any Supplement published in connection with the above booklet. To the Secretary, The Associated Portland Cement Manufacturers (1900), Limited, Portland House, Lloyds Avenue, London, E.G. Date.. Fictitious Portland Cement. A pamphlet which all users of Portland Cement should read. It deals with the peculiarities of " natural " cement i.e., fictitious Portland Cement and with the methods of those interested in pushing its sale. * Concrete & Reinforced Concrete in Mines. * The Uses of Portland Cement in Shipbuilding. Copies of the above pamphlets can be obtained free on application to THE ASSOCIATED PORTLAND CEMENT MANUFACTURERS (1900), LIMITED PORTLAND HOUSE LLOYDS AVENUE, E.G. THE LEADING BRANDS OF BRITISH PORTLAND CEMENT. Proprietors and Sole Manufacturers : The Associated Portland Cement Manufacturers (1900), Limited, Portland House, Lloyds Aveave, Fenchurch Street, London, E.G. THE LEWES PRESS, LTD., HIGH STREET, LEWES. THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL. BE ASSESSED FOR FAILURE TO RETURN RETURN CIRCULATION DEPARTMENT TO i^ 202 Main Library 642-3403 LOAN PERIOD 1 2 3 4 5 6 LIBRARY USE This book is due before closing time on the last date stamped below DUE AS STAMPED BELOW LIBRARY USF n^T 21 Q7O "WcilWcr tip* Is /o f " . T; IbT .,' LOAI i DEC 1 1 FORM NO. DD 6A 12m 6'76 UNIVERSITY OF CALIFORNIA, BERKELEY BERKELEY, CA 94720 I UNIVERSITY OF CALIFORNIA LIBRARY