THE MANUFACTURE OP 
 
 CONCRETE BLOCKS 
 
 AND THEIR USE IN 
 
 Building Construction 
 
The Manufacture of 
 
 CONCRETE BLOCKS 
 
 and their use in 
 
 Building Construction 
 
 By 
 
 H. H. RICE, 
 
 Secty. American Hydraulic Stone Co., Denver, Colo. 
 
 WM. M. TORRANCE, M.W.S.E., 
 Asst. Engineer Hudson Companies, New York 
 
 AND OTHERS. 
 
 New York : 
 
 The Engineering News Publishing Company, 
 1906. 
 
CONTENTS 
 
 Introduction 7 
 
 First Prize Paper, Engineering News Competition, by H. H. Rice. 11 
 
 Second Prize Paper, Engineering News Competition, by Wm. 
 
 M. Torrance 27 
 
 Extracts from other Papers submitted in Engineering News 
 Competition 61 
 
 Appendix I. Rules and Regulations Covering the Manufacture 
 and Use of Hollow Concrete Building Blocks in the City of 
 Philadelphia 108 
 
 Specifications Governing Method of Testing Hollow Block Ill 
 
 Appendix II. List of Manufacturers of Concrete Block Machines, 
 
 Molds and Tools 114 
 
 Index 117 
 
 17792 
 
Plate XIII— THE ROYAL BANK OF CANADA BUILDING, HAVANA, CUBA. 
 Built by Purely & Henderson, of Concrete Blocks Cast in Sand. 
 
 (See p 
 
PREFACE. 
 
 The two most important applications of concrete in building 
 construction at the present day are, first, reinforced concrete, and 
 second, concrete block construction. Concerning the first, a vast 
 amount of literature is available and the engineer desiring in- 
 formation finds technical periodicals and proceedings of engineer- 
 ing societies full of articles on reinforced concrete, while several 
 excellent books are also available. Concerning the second, how- 
 ever, there has been an absolute dearth of literature and at the 
 same time there is a demand for information, which it is the 
 object of the present book to supply. It is made up of a series of 
 articles by different authors, being those submitted in competition 
 for money prizes of $250 and $100 offered jointly by "Engineering 
 News" and "Cement Age," of New York City. The two papers 
 printed in full are those to whose authors the prizes were awarded; 
 the abstracts that follow the second prize paper are those parts of 
 the ten papers not awarded prizes that contained data not in the 
 prize papers or that presented the same information in greater 
 length or with more force. Altogether the papers and abstracts 
 form a practical treatise on the manufacture of concrete blocks 
 and their use in building construction that at present stands alone 
 in the literature relating to cement and concrete. 
 
INTRODUCTION. 
 
 The symposium of expert knowledge and opinion which makes 
 up the body of the present book presents for the first time an ade- 
 quate discussion of the technology of concrete block manufacture. 
 All the details of the industry are reviewed; the choice of locations 
 for concrete block factories, the plant and equipment required, the 
 selection of molding machines and processes, the manufacture, cur- 
 ing, shipping and storing of blocks, and, finally, their use in build- 
 ing construction, are all discussed. In view of all that these writers 
 tell us it can hardly be doubted that the intrinsic merits of hol- 
 low concrete blocks will ultimately give them a prominent place 
 among modern building materials. This assertion is made with a 
 full realization of the limitations of the new material and of the 
 conditions responsible for its present imperfect development. A 
 material that at its best has the value of natural stone in its 
 physical properties, that can be molded to any form to which stone 
 can be cut, and that shape for shape and volume for volume is far 
 less in cost than cut stone has just claim to a place in the work 
 of architects. 
 
 The imperfect development of concrete blocks as a building 
 material is a conceded fact. They are neither so widely used as 
 they might be, nor, where used, do they give the results aesthetically 
 and structurally that they are capable of being made to give. The 
 responsibility for this condition rests partly on the architect who 
 has done little to develop the architectural possibilities of the new 
 material and partly on the block maker who has applied false stand- 
 ards of beauty and utility to his product. 
 
 Concrete block manufacture originated with the idea chiefly in 
 mind of producing an artificial stone capable of competing with 
 brickwork in the construction of building walls. Incidentally, it 
 may be stated that the great bulk of block manufacturers have never 
 gotten away from this original conception. To compete with brick- 
 work the manufacturer was compelled to sacrifice everything to 
 cheapness. There was no possibility of doing anything at the low 
 price set as a goal but produce a concrete block of the plainest 
 and most economical form. The sole aim must be to duplicate a 
 chosen size and shape of block as many times and as frequently 
 as possible. The molding machines put on the market by various 
 inventors were devised with the object chiefly in view of producing 
 a cheap block. Their range of adjustability was limited to the 
 
molding of half-blocks or quarter-blocks and to the production of 
 such face patterns as could be managed by a simple change of 
 face plates. On the other hand every possible mechanical device 
 for increasing the output of blocks was utilized. 
 
 The result of this was that although working with a plastic 
 material capable of almost limitless variations in form and tex- 
 ture the block maker succeeded only in producing one of the most 
 rigidly regular and monotonously uniform building units ever 
 put on the market. It is true that he produced a building material 
 which was cheap, in fact, marvelously cheap, but it was one which 
 he could not get specified by architects for the better class of build- 
 ings. Concrete blocks found use only in the plainest of wall con- 
 struction, and here they struggled with brickwork for a place. In 
 many cases the block makers sacrificed quality as well as flexibility 
 of form and size, and thousands of blocks were made that were so 
 porous, ragged and weak that they were dangerous to use. This 
 still further damned the concrete block in the eyes of the architect. 
 
 We have spoken as if the conditions set forth were a thing of 
 the past. They are this only in case of the better class of block 
 manufacturers. The original idea that the mission of concrete 
 blocks is chiefly to replace brick as a structural material still pre- 
 vails with the majority of block makers and of block machine build- 
 ers. The idea that cheapness is an end in itself is hard to get 
 away from. In visiting recently a number of concrete block build- 
 ings under construction the writer was warned in each case that 
 he would not see concrete block work at its best. Why? Forsooth 
 the architect had refused to adapt his design to the standard blocks 
 produced by the machine in use. He had planned his windows so 
 that odd size blocks had to be made to fit the masonry to the 
 window arrangement; he had demanded blocks shallower or deeper 
 than the standard for certain courses where he thought that appear- 
 ance would be enhanced by the change; he had demanded various 
 face dimensions in order to secure a chosen bond that he considered 
 desirable to the looks of the building; he had done other irregular 
 things too numerous to mention. Wherein was the sin in all this, 
 it may be asked. The blockmaker's answer was that it decreased 
 the output of his machine, it increased the cost of the blocks, it 
 increased the cost of the walls, it made concrete block work far 
 more expensive than brickwork. The sin was that cheapness had 
 been sacrificed. 
 
 In justice to the industry, it should be said that these ideas 
 do not prevail with the most progressive and intelligent block manu- 
 facturers. They stand ready to execute the architect's plans, and 
 they invite work on this basis. Every block manufacturer who de- 
 sires to see his product go into building work of the better class 
 must do the same. This means that his standard of attainment 
 
must be the production of a material that will compete with the 
 best natural stone for most building purposes. There will always 
 remain cellar walls and cow barns to be built, and the single block 
 man will do as well at these as any one, but the block manufacturer 
 who intends to meet the quarryman in the architect's office and on 
 an equal footing must stand ready to duplicate the quarryman's 
 product size for size and shape for shape, and to do it for less money. 
 
 Duplication in the sense that it is urged here , does not mean 
 imitation. Only a few of those who have imbibed the broader 
 doctrine of competition with natural stone have perceived this fact 
 to the fullest degree. Imitation of natural stone has a small place, 
 if any place at all, in the work of the concrete block maker. 
 Honesty is as vital a principle in art as it is in trade. It is not 
 honest to give to concrete a pretense of being what it is not. More- 
 over, concrete does not need the factitious aid of a simulated pitch 
 face dressing in order that it may satisfy the eye in building con- 
 struction. The pride of the worker in the material with which he 
 works should alone prevent him for masking its identity. 
 
 The block maker may ask at this point if he is to abandon color- 
 ing, ornamentation and surface dressing for his product. The 
 answer is, certainly not. Coloring may be used as freely as he 
 chooses so long as it is used with taste, but it should not be used 
 for the purpose of imitating a natural stone. In the same way the 
 block maker may hammer-dress or chisel the face of his concrete, 
 but he should do it not to make it resemble cut stone, but simply 
 for the variation in surface texture in the same material that proper 
 tooling may be made to furnish. In the matter of ornamentation 
 the block maker is at equal liberty, but he had better do as the 
 quarryman does and produce his ornamental work only to the order 
 of the architect. There is far more than this to be said of the possi- 
 bilities of surface finish and ornamentation in concrete work, but 
 here we wish merely to prescribe a single broad precept to be obeyed 
 in their use. Let the block maker shun imitation, and work for 
 appearance always within the limitations of his material. 
 
 Concrete has so many advantages as a building material that 
 it is frequently forgotten that it has its limitations. Concrete is 
 concrete always. A natural stone may be granite or marble or 
 onyx. Concrete has beauty of its own which may be properly en- 
 hanced in a variety of ways, but it has not the peculiar beauty 
 of marble or of granite, and the architect cannot be expected to 
 choose it when he wishes the color and texture effects peculiar to 
 granite or marble. Furthermore, he will not, if he be an artist, 
 choose an imitation. In conversation recently a very prominent 
 architect said: "These block makers come in here and say, 'why 
 don't you use concrete blocks? I can make a block that ten feet away 
 you can't tell from red sandstone or marble or what not.' Now I 
 
don't wish a concrete block that I can't tell from sandstone. I 
 wish a concrete block that won't 'flower.' When I wish sandstone 
 I can get sandstone." The rebuke in these statements is just; the 
 business of the concrete block maker is to make concrete blocks 
 and to make them without defects and not to make imitation sand- 
 stone. 
 
 The discussion so far has borne rather heavily on the short- 
 comings of the block maker, but the architect has been quite as 
 negligent of his obligations if these may be assumed to exist at all 
 in lending his aid in developing the possibilities of new structural 
 materials. In a recent article we find the following statement: 
 "The architect will be ready to use their product (concrete blocks) 
 the moment it conforms to his conception of what constitutes a 
 pleasing as well as a durable building material." Possibly it would 
 not be professional good form, but it occurs to one not an architect 
 that the architect's interest and activity might well go a step 
 further. He might tell the block maker what he would consider 
 to be pleasing, or failing in this he could at least tell him wherein 
 his present product was unpleasing. This would help somewhat 
 toward reaching the lofty plane where their product would conform 
 to the architect's conception of what constitutes a pleasing building 
 material. It would help matters considerably more, however, if the 
 architect would devote a little study to ascertaining if possible how 
 by adopting suitable architectural styles and finishes and forms of 
 blocks, concrete blocks could be made to work out pleasingly to 
 the eye in building construction. There is no insuperable obstacle 
 to doing this; in fact, it has been done for a few special structures. 
 The Royal Bank of Canada building at Havana, Cuba, illustrated 
 in the body of this book, is one of these structures. One can point 
 out others that are fully as enlightening as to the architectural 
 possibilities of concrete blocks. They are equally enlightening to 
 the block maker, for they show him what he must do if he is to 
 claim a place with architects for his production in competition with 
 cut stone. 
 
 Editors, 
 
 ENGINEERING NEWS. 
 
 April, 1906. 
 
The Manufacture of Concrete Blocks and 
 Their Use in Building Construction. 
 
 First Prize Paper in ENGINEERING NEWS Competition. 
 
 H. H. Rice. 
 
 CONCRETE. 
 
 In any discussion of concrete blocks a clear conception of the 
 theory of concrete is essential. We have heard and read a great 
 deal of "artificial stone," and I wish that we might forget the term 
 and banish from our minds the idea it conveys. I would that we 
 might rather embrace the thought of concrete as a union of certain 
 elements scientifically combined to form a material useful in con- 
 struction because of its own distinctive merits, and not because of 
 its resemblance to any other natural or artificial product. I am 
 convinced that the effort toward imitation has caused half of the 
 evils in connection with concrete construction. If we take it for 
 what it is, rather than what it resembles, we shall find qualities, 
 uses and advantages worthy of exhaustive research. Concrete is 
 neither more nor less than a form of masonry readily adaptable 
 to a large variety of uses because of the facility of production in 
 any desired size or form. On account of the large number of aggre- 
 gate members and the diversity in their shape and size, it requires 
 the application of certain scientific methods in relation to the 
 mortar, which are not required in masonry as the latter term is 
 popularly used. The underlying principle of good concrete con- 
 struction is that every particle of sand shall be thoroughly coated 
 with cement, and that every piece of gravel or broken stone shall 
 be thoroughly coated with the mixture of sand and cement. To the 
 observance of this principle we must closely adhere if we would 
 avoid those evils which have often followed the use of defective 
 concrete, and by faithful adherence to this basic rule we shall pro- 
 duce a constructive material possessing such marked distinctive 
 advantages that it easily rests upon its own merits. 
 
 MATERIALS. 
 
 In considering the materials used in the manufacture of con- 
 crete blocks, cement claims our first attention. The use of cement 
 
12 
 
 CONCRETE BLOCKS 
 
 in concrete construction is first actively brought to our notice by 
 the Romans. They discovered that calcined clay finely ground and 
 added to lime produced a substance which would set under water. 
 The volcanic dust found near the village of Pozzuolo afforded an 
 excellent hydraulic base for this lime-mortar, and the cement came 
 to be called Puzzuolani. Modern orthographers have abbreviated 
 this to Puzzolan, and the latter term in modern practice denotes 
 any cement produced by the intimate mixing and grinding to ex- 
 treme fineness, without subsequent calcination, of furnace slag, vol- 
 canic dust or burned clay and powdered bydrates of lime. Puzzolan 
 cement attains great strength and toughness, but never becomes 
 hard like a true Portland cement. It is not adapted for use ex- 
 cept under water or in places where it can be constantly moist, as 
 a dry atmosphere causes oxidation of the sulphides and resultant 
 cracks and disintegration. Puzzolan cement is much lighter in 
 weight than Portland, and is usually of a light lilac color instead 
 of the well-known bluish gray. Freshly made pats of Puzzolan will 
 show stains instead of the even color of Portland. 
 
 The manufacture of cement in England began about the year 
 1791, with Parker's cement, which was produced by calcining at 
 a temperature sufficient to liberate the carbonic acid gas, and subse- 
 quently pulverizing, the argillo-calcareous nodules found in the 
 Isle of Sheppey, containing approximately 70% carbonate of lime, 
 4% oxide of iron, 18% silica and 6%% alumina. Although the first 
 discovery of cement rock in the United States was made 87 years 
 ago, the process of manufacturing natural hydraulic cement is to- 
 day, excepting improvements in kilns and grinding processes, sub- 
 stantially the same as used by Mr. Parker. The relative growth 
 of the natural hydraulic cement industry and of the Portland cement 
 industry is shown by the fact that of the former there were manu- 
 factured in the United States 2,030,000 barrels in 1880 and 4,86fi,331 
 barrels in 1904, as against 82,000 barrels of the latter in 1880 and 
 26,505,881 barrels in 1904, showing for the 24 years last past a 
 gain of less than 140% for the natural hydraulic cement against 
 a gain of 32,224% for the Portland. 
 
 Another cement which deserves passing notice is known as 
 silica cement. It is merely a mixture of equal parts of Portland 
 cement and sand ground to extreme fineness. It produces good re- 
 sults, but is in reality an adulteration, and there is no excuse, at 
 the present low price of cement, for its purchase. It may be de- 
 tected by the sediment in the jelly remaining after pouring a little 
 muriatic acid on a small quantity of cement. 
 
 Portland cement is produced by calcining up to incipient fusion 
 a mixture in definite proportions of argillaceous and calcareous 
 substances, the resulting clinker being ground to extreme fineness. 
 It is a curious fact that this clinker is incapable of hydraulic 
 
MANUFACTURE AND USE 13 
 
 activity before grinding, and that the hydraulicity of cement con- 
 stantly increases with fineness of grinding. The name was first 
 given to this class of cements on account of the resemblance in 
 color to the famous Portland building stone of England. The essen- 
 tial elements are lime, silica and alumina. The industry was devel- 
 oped in Europe earlier than in America, and certain German brands 
 have gained a world-wide reputation, though possessing no points 
 of superiority over the American brands of the present day. 
 
 With the development of the rotary kiln, which was invented 
 in England but perfected in the United States, a great gain was 
 effected by placing the process of burning at all times under the 
 direct control of the operator. Improvements in grinding ma- 
 chinery have similarly increased the efficiency in that department, 
 while the relative proportions of ingredients are now carefully de- 
 termined by constant chemical analysis, so that the product of 
 an American Portland cement plant is of a very definitely known 
 quality. In 1903 there were 78 factories in the United States mak- 
 ing a true Portland cement. It is, therefore, evident that a wide 
 range of choice is offered as to brands, and the concrete block 
 manufacturer will be largely governed by location and freight rates, 
 as the keen competition of recent years has resulted in a product 
 so uniformly excellent that one can scarcely go amiss in buying 
 from one of the larger companies. 
 
 In selecting a brand of known reputation one is able to profit 
 by the exhaustive factory tests, and leave himself free to make 
 his own tests on blocks of the finished concrete. And this is in 
 some respects more satisfactory, for, while cement theoretically con- 
 stitutes the principal element of strength in concrete, it is found 
 in practice that the character of aggregates and the presence of 
 deleterious substances in the sand have a very potent bearing on 
 the ultimate strength. One should as far as possible avoid the 
 use of different brands of cement, as greater uniformity of color 
 is thus obtained. Prices are made on Portland cement by the bar- 
 rel of 380 lbs. net, each barrel being the equivalent of four sacks 
 of one cubic foot each. It may be procured in paper sacks or 
 in cloth, the latter being billed at 10 cents each, and an equal 
 credit allowed for all sacks returned in good condition to the fac- 
 tory. As a considerable saving in cost is made by large purchases, 
 ample storage should be provided for a stock of cement, and precau- 
 tions taken to preclude the possibility of its gathering moisture. 
 
 Sand is the next ingredient to be considered. Local availability 
 and cost must, of course, govern to some extent. The sand should, 
 however, be sharp, siliceous and clean. While some experimental 
 tests have shown no loss of strength by an admixture of a certain 
 percentage of clay, the best practice in building block work de- 
 mands that the sand be free from loam, clay or other foreign 
 
14 
 
 CONCRETE BLOCKS 
 
 substances. If sand cannot be obtained in its natural state with- • 
 out such foreign materials, thorough washing is necessary to pro- 
 duce a reliable block. The general rule is, that the washing should 
 continue until clean water is no longer discolored. The sharper 
 the sand the greater will be the strength of the block. This is not 
 hard to understand when we consider the necessity of the cement 
 adhering to the sand facets, and also that the increase of sharpness 
 produces a better bond among the grains of sand. 
 
 The color of sand is worthy of consideration, as it has more 
 to do with the" color of the block than, most operators realize. Where 
 a facing is used of a texture differing from the body of the block, 
 it is very desirable to have a supply of white sand, similar to 
 that used in the manufacture of glass, by the use of which a 
 most beautiful face is secured without the addition of coloring mat- 
 ter. The quantity of sand should have the most careful consid- 
 eration, as this will determine whether the block will be weak and 
 porous or strong and dense in structure. The greater the propor- 
 tion of sand, the more cement necessary to cause adhesion of the 
 grains, and to fill the voids in the sand, but the amount of sand 
 must not be less than necessary to fill the voids in the gravel or 
 broken stone. It is not supposed that the average block maker 
 will have at hand elaborate apparatus for scientific determination 
 of voids and porosity, and therefore his best method of arriving 
 at the proper proportions of sand to use with a given aggregate 
 is to pour into a vessel filled with gravel or stone a measured quan- 
 tity of water. The volume of water received will closely approxi- 
 mate the requisite amount of sand. This is very important on 
 account of the variation in aggregates, and it is impossible with- 
 out some test of this kind to say that a given mixture will result 
 in a dense block unless the proposed mixture be so largely sand that 
 an abnormal amount of cement is used or the grains are not thor- 
 oughly coated. 
 
 The gravel used in concrete block manufacture should contain 
 a fair percentage of as large sizes as can be advantageously em- 
 ployed in the particular style of machine in use. It is better to 
 have the gravel run from fine to coarse as the smaller sizes will 
 tend to fill the spaces intervening between the large sizes, thus 
 reducing the amount of sand necessary to fill voids. For this reason 
 bank gravel is preferable, as it will often show such a gradation 
 of sizes as to require little admixture of sand, but like sand it 
 must be free from foreign materials. It is always advantageous 
 to use as great a percentage of large sizes as possible without 
 creation of voids as by this course greater strength is obtained 
 from a given percentage of cement. 
 
 Where gravel is not available, crushed stone is used. In such 
 cases care must be exercised to obtain stone which will be as strong 
 
MANUFACTURE AND USE 
 
 15 
 
 as the mortar, otherwise the concrete will be weakened by lack 
 of strength in the aggregates. Exhaustive experiments on the 
 relative strength of stone and gravel concrete show that at an 
 early age the stone concrete is stronger but the gravel concrete 
 makes a greater percentage of gain in strength with age. 
 
 Cinder concrete should not be used for walls intended to carry 
 weight or to be subjected to lateral stress. Brickbats and similar 
 materials are not permissible as aggregates in any class of concrete 
 block construction. 
 
 The water used both in mixing and in curing should be clean 
 and as free as possible from injurious minerals or vegetable mat- 
 ter. The amount of water will vary under different systems of 
 manufacture, but under all it is an item of the greatest importance, 
 without which chemical reaction is impossible. 
 
 MIXING. 
 
 In the matter of mixing, the first question which presents itself 
 is what proportions shall be used. While the character of local 
 materials makes it impossible to lay down any exact rule, some 
 general observations may be helpful. The voids in sand, gravel or 
 broken stone will show a variation ranging from 33% to 50%. 
 Assuming that we have to deal with the larger percentage, a mix 
 of 1-2-4 should be used, which is classified as the lowest grade of 
 fat mixture. With certain character of aggregates, however, a lean 
 mixture, as 1-3-5, may be advantageously employed. On the other 
 hand, where gravel or broken stone is not used, the proportion 
 should be 1 to 4 of cement and sand. A fat mixture possesses 
 greater tensile strength than a lean, but compressive strength de- 
 pends upon the thorough filling of voids. Ultimate success with 
 any mixture can only be attained by the entire coating of every 
 grain of sand with cement and every piece of stone or gravel 
 with the sand-cement mortar. Hence it is evident that a lean mix- 
 ture may with thorough and intelligent mixing prove more satis- 
 factory than a fat mixture with hasty and indifferent mixing. 
 
 Where necessity compels mixing by hand; a platform or cement 
 floor should be provided and the sand spread thereon, the cement 
 then spread on the sand and turned twice before wetting. The 
 water should then be applied by spray from a hose nozzle while 
 the mixture is being turned, and when the mass is sufficiently moist- 
 ened and the water evenly incorporated the gravel or stone (pre- 
 viously wet to avoid absorption) should be spread on this mortar 
 and the whole turned at least twice. It is a good rule to continue 
 the mixing until an even color is obtained. 
 
 Wherever possible, however, a power mixer should be installed 
 as the initial cost is a matter of small consideration in view of 
 the subsequent saving of labor and the greater uniformity obtained 
 
16 CONCRETE BLOCKS 
 
 in the mix. The most exhaustive comparative tests of hand and 
 machine mixing of which record has been made were in connec- 
 tion with the construction of a pier in Duluth Harbor about five 
 years ago. At seven days the hand-mixed concrete showed 53% of 
 the strength of machine mixed; at 28 days 77%; at six months 84%, 
 and at one year 87%. 
 
 There are a great many mixers on the market and it is neces- 
 sary to exercise some judgment in selecting one which will thor- 
 oughly mix the ingredients and do it quickly and cheaply. The 
 usual type of continuous mixer is not so well adapted to concrete 
 block manufacture as are the batch mixers. It is very important, 
 either in hand or machine mixing, to regulate the size of batches 
 mixed so that no concrete shall be used which has been wet over 
 half an hour, as cements usually take their initial set within 30 
 or 40 minutes after the addition of water, and if incorporated into 
 blocks thereafter a certain portion of strength is lost. 
 
 The amount of water used in mixing is subject to the greatest 
 variation, depending upon the style of machine used. A dry mix- 
 ture is one in which just enough water is used to hold the cement 
 and sand together. When compressed in the hand it will retain 
 its shape, but will show no water and will not discolor the hand, 
 in a more or less fluid condition. It will be seen that machines 
 have been designed for using these different mixtures and the 
 manufacturers of these various machines adhere with great ten- 
 acity to the particular degree of moisture required to obtain the 
 best results under their respective methods of manufacture. Tests 
 show, in a general way, that a dry mix has its greatest relative 
 strength on short time tests while the use of a greater percentage 
 of water increases the relative increase in strength with age. In 
 the process of concrete block making a certain amount of water 
 is absolutely essential to secure proper crystallization of the sili- 
 cates and if it is not used in the mixture it must be supplied 
 subsequently. Whatever method be used it is essential that the 
 proportion of water be uniform, as the making of one batch wet 
 and another dry will produce an unsightly variation in the color 
 of the blocks. 
 
 Before leaving the subject of mixing, I wish to more fully im- 
 press upon the reader the importance of the most thorough manipu- 
 lation of the mass. We have already seen that it is only by this 
 method that voids can be eliminated and the greatest strength 
 obtained. There are, however, other advantages resulting from an 
 absence of porosity. The permeability of a concrete block is greatly 
 reduced by added density and with sufficient attention to this matter 
 the question of waterproofing is, at least in a measure, solved. 
 Efflorescence is also practically overcome by making really dense 
 and reasonably impervious blocks. 
 
MANUFACTURE AND USE 17 
 MANUFACTURE. 
 
 Our materials having been selected, our proportions having 
 been determined, our mixture having been made, we are now ready 
 for the actual manufacturing of concrete blocks. The processes 
 which are offered for our consideration are three in number: Tamp- 
 ing, pressing and pouring. 
 
 The first is the method generally used in connection with the 
 dry mixture, the material being shoveled into molds and gradually 
 rammed to place as the mold is filling. To secure good results it 
 is necessary that the tamping be thoroughly done, which involves 
 a considerable amount of labor. Of late several automatic tampers 
 have been placed on the market, calculated to lighten the labor, 
 secure greater rapidity in manufacture and insure a more uniform' 
 A medium mixture is one in which water enough is used to flush 
 to the surface when slightly tamped or compressed. A wet mix- 
 ture is one in which an excess of water is used, the concrete being 
 product. Tamping is better adapted to a dry mixture, as it will 
 pack under the blows of the tamper and will not become displaced 
 by lateral pressure as is the case if a medium or wet mixture be 
 used under a tamper. This method is also more satisfactory with 
 a cement and sand mixture than with coarser aggregates, as gravel 
 or broken stone, unless comparatively small in size, does not readily 
 yield the best results either in a dry mixture or under tamping. 
 It may, therefore, be set down as a general rule that under tamped 
 processes a dry mixture and aggregates of small size should be 
 employed. 
 
 Under the systems using compression the advantage is claimed 
 that a more uniform density is secured by the simultaneous appli- 
 cation of pressure to all parts of the block. As the mold is entirely 
 filled before the application of this pressure, the necessity for a 
 dry mixture and fine aggregates is overcome, and a medium mix- 
 ture is ordinarily employed containing aggregates of a size as large 
 as can be conveniently accommodated in the particular mold in use. 
 
 The plan of operation under the poured processes is radically 
 different from either of the others, as neither tamping or pres- 
 sure is relied upon to compact the mass and bring the aggregates 
 so close together as to secure necessary adhesion. Reliance is 
 rather had upon the reduction of the cement to a fluid state, it 
 being contended that by this method the aggregates are more thor- 
 oughly coated and perfect crystallization assured. An honest objec- 
 tion to this process appears to lie in the fact that the greater specific 
 gravity of the cement is liable to cause it to settle to the bottom 
 of the mold, and a practical difficulty is the large number of molds 
 necessary on account of the length of time required for such a 
 block to attain sufficient rigidity to be removed from the mold. 
 
18 
 
 CONCRETE BLOCKS 
 
 It is to be presumed that any one about to engage in the manu- 
 facture of concrete building blocks will provide himself with some 
 one of the large number of machines now offered to the public, 
 which are roughly divisible into five classes: 
 
 1. Upright machines for making hollow blocks. 
 
 2. Machines for making hollow blocks on the side. 
 
 3. Machines for making staggered blocks. 
 
 4. Machines operated by the wet process. 
 
 5. Machines making blocks for two-piece walls. 
 
 The first class of machine is, I take it, well known to most 
 readers. The machines consist of removable hinged sides and up- 
 right interior cores. The blocks are made by tamping under the 
 dry process and are, in the earlier designs of machines, removed 
 on iron pallets, while some of the later machines avoid this expense 
 by turning the mold over and releasing the block on wood or in 
 some cases by making the block on a wooden board and lifting 
 the mold bodily away from the block. The cores are in many ma- 
 chines mechanically raised and lowered, but in others the cores 
 remain stationary while the bottom and sides are adjustable by 
 various mechanical devices. It is evident that these variations have 
 little influence on the manufactured block, and are merely labor- 
 saving contrivances. The principle involved in the manufacture 
 is in every case the same. 
 
 The second class is only different from the first in so far as 
 the mold is turned on its side in order to facilitate facing. The 
 face matter is first deposited and tamped, after which the cores 
 slide into the mold laterally and the filling and tamping proceeds. 
 The only thing gained over the first class is the opportunity to 
 use a face mixture of different composition from the body of the 
 block. 
 
 The third class eliminates the straight cross-partitions of the 
 first and second classes and so disposes the cores that a staggered 
 effect is produced. The object is to prevent the passage of moisture 
 through the wall. This class of blocks have not been long on the 
 market but seem to be meeting with considerable success, and are 
 apparently an improvement as to the purpose they aim to accom- 
 plish. 
 
 The fourth class is totally different from others in process. 
 They use a large number of light iron molds, having interior cores, 
 and usually constructed to admit a circulation of air in the walls 
 by making the body of the block of a less height and length than 
 the faces. Into these molds the wet mixture previously described 
 is poured and allowed to stand for several hours. The principal 
 contentions of manufacturers of these molds are that the blocks 
 are waterproof; that they are actual stone, and that they are cheaply 
 made. 
 
MANUFACTURE AND USE 
 
 19 
 
 Class five is a radical departure from the others. Two-piece 
 walls were brought out about three years ago and have distinctive 
 features worthy of consideration. They are manufactured by pres- 
 sure of a medium mixture, usually containing a considerable por- 
 tion of large aggregates. This mixture is shoveled into the mold, 
 pressed almost instantaneously, and forthwith released from the 
 mold. "Where it is desired to use a face mixture of color or tex- 
 ture other than the concrete forming the body of the block, a 
 gage is used to rake out a quarter or three-eighths of an inch of 
 the coarse concrete before it is pressed, and the face matter is 
 applied on this loose mass and all pressed at one time. This bonds 
 the face and body of the block very firmly together and as the 
 pressure is applied directly to the face of the block a beautiful 
 face of great hardness and density is obtained. This method of 
 manufacture is made possible by the shape of the block, which con- 
 sists of a face section with a long right-angle arm extending in- 
 wardly from the middle and a shorter arm extending from each 
 end. In laying the blocks in a wall no portion of a block extends 
 through the wall and, indeed, by leaving the interior vertical joints 
 open to afford a free circulation of air no portion of a block on 
 one side of the wall comes in contact with any block from the 
 opposite side, thus precluding the passage of moisture and pro- 
 ducing in effect two walls, tied by the overlapping of arms or webs 
 in alternate courses, and affording a great resistance to lateral 
 stress by the employment of the principle of bonding known as 
 the header and stretcher bond of brick work or the three-quarter 
 stone of ordinary masonry, while in thin partition walls the bond- 
 ing is by the system of through-stones. 
 
 CURING. 
 
 While the importance of curing leads us to consider it under 
 a separate heading, it is well to understand distinctly that curing 
 is a most important part of the manufacturing process. It is in 
 the adaptability for effective and thorough curing that block con- 
 struction differs essentially from all other systems of concrete 
 construction, and therein does it possess a distinct advantage. It 
 is, however, necessary that the importance of curing be firmly im- 
 pressed upon the block maker and every effort made to secure 
 the best results. I believe that to a failure to appreciate the ad- 
 vantages of scientific curing is due, more than to any other cause, 
 the difficulties encountered by many manufacturers. To secure 
 strength and durability in concrete blocks it is necessary that the 
 cement shall have a certain amount of water to produce the chem- 
 ical reactions resulting in crystallization of the silicates of lime 
 and aluminum. If the requisite amount of water be not used in 
 the initial mixing it is evident that it must be subsequently sup- 
 
20 CONCRETE BLOCKS 
 
 plied. However, this application of moisture is often made in a 
 manner so irregular and haphazard that the cement is allowed 
 to take its final set under the most unfavorable conditions and as 
 a consequence a great portion of its strength is lost. 
 
 The great point to be remembered is that uniform conditions 
 must be maintained. If a block be wet in the morning, dry at 
 noon and wet again at night it is not hard to see why it will 
 lack strength when tested. Again, it is essential that every part 
 of the block shall have the same treatment. Varying degrees of 
 moisture or exposure to the sun will cause variation in contraction 
 and result in cracks and liability to subsequent disintegration, as 
 well as variation in color. It is, therefore, essential that the blocks 
 be sprinkled at regular intervals, and so frequently that there is 
 no drying. The blocks should not, during curing, be allowed to 
 become dry enough to begin to turn white. The sprinkling should 
 be thorough, evenly reaching every part of the block and should 
 be accomplished by use of a gentle spray which will not deface 
 the freshly made blocks. Moreover, the blocks must be protected 
 from the sun to secure necessary uniformity of conditions. A free 
 circulation of air among the blocks is desirable, and it is bad 
 practice to allow blocks to rest in contact with one another in 
 the curing shed. Most manufacturers are anxious to make a record 
 as to speed and cost, and rush blocks into a wall while too green. 
 The result is that the exposed side of the wall dries more rapidly 
 than the interior and the part which should possess the greater 
 strength becomes the weaker and may disintegrate in a few years. 
 
 Blocks made by the dry process should have the most careful 
 curing for at least twenty days after coming from the molds, while 
 from a week to ten days of similar treatment will suffice for blocks 
 made from a medium mixture. Blocks made by the wet process con- 
 tain an excess of water which is subsequently taken up by the 
 cement so that they will require little water in curing except on 
 exposed surfaces, but the maintenance of uniform conditions and 
 shelter from the sun is quite as important as under either of the 
 other processes. 
 
 The curing of blocks in winter has been successfully conducted 
 by protection from freezing for the first few days. As soon as the 
 block acquires sufficient rigidity to protect itself from the danger 
 of expansion cracks, freezing merely suspends the setting but does 
 not prevent its resumption upon a rise in temperature. However, 
 curing under these conditions requires more time and a constant 
 exercise of the greatest caution. 
 
 In view of the fact that crystallization is quickened by a rise 
 in temperature experiments have been made on curing blocks in 
 a Mve steam room. The results have been very satisfactory as 
 to time, making it possible to lay blocks in the wall within 48 hours 
 
MANUFACTURE AND USE 
 
 21 
 
 after molding. It is still an unsettled question, however, as to 
 how great an extent this artificial acceleration of the chemical reac- 
 tion secures the full strength of the cement. 
 
 FACING. 
 
 Authorities differ as to the advisability of applying a thin facing 
 of different composition from the material composing the body of 
 the block. As the manufacture of concrete blocks sprang from mono- 
 lithic construction, it is believed that the opposition to facing orig- 
 inated from the bad results obtained by efforts made to face that 
 class of work. The cause of those ill effects is, however, not dif- 
 ficult to determine when one considers that in such construction 
 the coarse concrete is deposited in forms and allowed to set for 
 some time before the removal of those forms, and that the face 
 matter is afterward applied and the surface troweled. This pro- 
 cess is wrong for two reasons: First, the backing having already 
 taken its set does not, even though thoroughly wet, allow ready 
 adhesion of the facing which is, therefore, liable to separation and 
 cracking. Second, the troweling draws the neat cement to the 
 surface and results in hair cracks owing to the variation in con- 
 traction. The fact that very many of the machines now on the 
 market advertise facility of facing as a strong point in favor of 
 their process indicates that facing is growing in favor, and it is 
 certain that the efforts made by the various manufacturers to satis- 
 factorily solve this problem have resulted in greater success than 
 was generally anticipated. It will, therefore, be well to consider 
 some points in connection with methods calculated to secure the 
 greatest efficiency in this line. 
 
 The objects of facing are three: 
 
 1. Saving in cost of material. 
 
 2. Securing a beautiful surface. 
 
 3. Making the surface more dense and impervious. 
 
 The saving in material is effected by using a coarse lean mix- 
 ture for the body of the block and applying a face of fine fat mix- 
 ture varying from a quarter to a half inch in thickness. The beauty 
 of surface results from the opportunity afforded of using expensive 
 selected material for this thin face which would make the cost pro- 
 hibitive if used throughout the entire block. The use of the fat 
 mixture with the fine aggregate makes it possible to produce a 
 face which is practically impermeable and possesses much greater 
 density than the mixture ordinarily employed for the body of the 
 block. 
 
 The selection of sand for the face mixture is worthy of most 
 careful consideration, and here we are not dependent upon local 
 availability as the small quantity required warrant shipping from 
 a considerable distance to ensure the desired result. As mentioned 
 
22 CONCRETE BLOCKS 
 
 in a previous section, a fine white sand of such sharpness as used 
 in glass factories is suitable, and sharp screenings from crushed 
 granite also afford an excellent material. 
 
 The face mixture may be made in proportions varying from 1-1 
 to 1-3 and requires greater care in mixing than concrete, as there 
 is a tendency to roll up and become lumpy, which may be over- 
 come by screening the wet mixture immediately before use. The 
 best results are obtained by using a little more water than usual 
 in the body of the block and applying the face matter in about 
 the consistency of an ordinary dry mix; the face will then, by 
 capillary attraction, draw moisture from the body of the block. It 
 will be noted that the process is, in this respect, directly opposite 
 to the method ordinarily used in sidewalk construction. 
 
 Whether the block be made by tamping or pressure, it should 
 be so arranged that direct compression of the face is obtained and 
 there must be no interval of time between the manufacture of the 
 face and body of the block, but both must be made at one simul-. 
 taneous operation, so that the face matter may be thoroughly im- 
 bedded into the loose coarse concrete and become an integral part 
 of the block with no distinct line of cleavage between the two. 
 It is only thus that separation and cracks may be avoided and a 
 product of great durability assured. 
 
 Many block makers produce desired colors by mixing dry colors 
 with the face matter. Only mineral colors should be used, free 
 from deleterious chemicals, acids or greases. As several manufac- 
 turers are now offering a variety of colors especially prepared with 
 a view to obviate the loss of strength frequently resulting from an 
 admixture of coloring matter, and as these specially prepared colors 
 have given general satisfaction it is well to procure them and avoid 
 the expense and annoyance incident to experimentation along orig- 
 inal lines of coloring. These colors are thoroughly mixed with the 
 dry facing sand before the cement is added, and used in such pro- 
 portions that a freshly made block will be two shades darker than 
 required when cured. 
 
 The form of face is a matter which is given much attention 
 by the manufacturers of concrete block machines. Those in most 
 common use are smooth face, bevel edge, corrugated or ribbed, pitch 
 or rock face, and special designs of ornamental faces. In the use 
 of various designs of these face plates it is desirable, at all times, 
 to bear clearly in mind the fact that concrete blocks have a place 
 of their own in building construction, that they are capable of such 
 artistic finish that they may rest upon the merit of their own beauty, 
 and that they are not dependent for their popularity upon imita- 
 tion of any other material commonly used in the construction of 
 buildings. It is to this idea of imitation which has been so preva- 
 lent in the earlier stages of the development of this industry, and 
 
MANUFACTURE AND USE 23 
 
 to the consequent failure to appreciate the artistic possibilities of 
 concrete block construction, that much that is monotonous, much 
 that is artificial, much that is unpleasing and abhorrent in concrete 
 block architecture is chargeable. 
 
 TESTING. 
 
 It is very desirable that tests of tensile and compressive strength 
 be made from time to time. While the customary method of testing 
 cement briquettes is useful, it gives us no information concerning 
 the strength-giving properties of the other materials used, and it 
 was found in a series of tests recently conducted at the University 
 of Michigan that the character of sand, gravel or broken stone, 
 the presence of earthy matter, the use of an excessive amount of 
 sand, the size of aggregates and the thoroughness of mixing, all 
 have an important bearing upon the strength of the finished block. 
 A block for testing should be not less than 28 days old, and to 
 ascertain the relative tensile strength should be supported by knife 
 edges upon the platen of the testing press with the load resting upon 
 the center of the block. Compression tests may afterward be made 
 upon fragments of the same block. 
 
 COST. 
 
 Too much has been written about the low cost of concrete blocks. 
 While they may be placed in the wall at a lower cost than any nat- 
 ural material of equal quality, yet the distinctive points of excel- 
 lence peculiar to concrete block construction are of far greater mo- 
 ment than the saving in cost. Many block makers have considered 
 low cost the chief end to be attained and have sacrificed quality 
 to its attainment, while the highest success can only be secured by 
 those who make uniformly superior blocks and keep the cost down 
 by intelligent management and judicious systematization of the work 
 of manufacturing. The literature of every manufacturer of concrete 
 block machines contains statements of cost, and these figures may 
 be considered as truthfully compiled from the results of work in- 
 telligently conducted under favorable conditions. A paper read at 
 a recent meting of the Iowa Cement Users contains a rather full 
 report as to cost, being compiled from reports obtained from a 
 large number of block makers. The results were computed to ascer- 
 tain the average cost per square foot of 10-in. wall, and were as 
 follows: 
 
 Sand 2.0 cts. 
 
 Cement 4.5 " 
 
 Labor (manufacture and curing) 3.8 " 
 
 Total 10.3 cts. 
 
 For 8-in. walls, 1 ct. less. 
 For 12-in. walls, 1% cts. more. 
 
 The cost of labor and mortar for laying averaged five cents per 
 
24 CONCRETE BLOCKS 
 
 foot. The above figures do not take into consideration the cost of 
 administration or incidentals. 
 
 CONSTRUCTION. 
 
 In laying blocks in a wall it is necessary that they be first thor- 
 oughly moistened to prevent absorption of water from the mortar 
 and consequent insufficiency of adhesion. The best mortar for laying 
 concrete blocks is composed of one part cement, three sand and one 
 slaked lime. The admixture of this proportion of lime increases 
 the adhesiveness and gives to the mortar a body which makes it 
 trowel with greater facility. To produce satisfactory results it is 
 necessary that joints be uniform. Usually a quarter inch joint will 
 produce the best effect. 
 
 The size of blocks varies greatly with the different machines 
 and processes and it would seem, as suggested at the June meeting 
 of the Concrete Block Machine Manufacturers' Association, that the 
 public good might be greatly subserved by the exercise of a spirit 
 of co-operation looking toward the adoption of more universal stand- 
 ards of sizes. There is no apparent reason why the size of concrete 
 blocks should not be as standard as the size of brick. What this 
 size should be is not material so long as symmetrical proportions 
 are maintained between the width and length by observing the rule 
 of multiples. Whatever size may ultimately be adopted should have 
 allowance made for width of mortar joints so that the block when 
 laid in the wall will, with its mortar joint, be of the determined 
 dimensions. 
 
 Until such action shall be taken it is impracticable to prepare 
 any extensive sets of plans for the construction of concrete build- 
 ings. The only important respect in which such plans would dif- 
 fer from those for buildings of other materials would be in the 
 adaptation of dimensions to the size of the blocks and the placing 
 of openings in conformity thereto, but with the present diversity 
 of sizes a series of plans adapted to the product of one machine 
 would be no better suited to the product of another than would 
 the plan of an ordinary brick house. 
 
 A few manufacturers provide machines for making sills and 
 lintels of four and five feet lengths, but it is not practicable to 
 construct machines along present lines for the larger sizes so often 
 required, and it may be fairly said that in general the block maker 
 is thrown upon his own resources for the construction of these parts 
 of a building. Some simple reinforcement may be used and these 
 parts easily and quickly constructed in wooden molds made in any 
 block factory. The customary method of troweling the surface has 
 been the cause of most of the trouble in making sills and lintels. 
 As previously mentioned this troweling causes checks and hair 
 cracks, rendering the work unsightly and liable to weather badly. 
 
MANUFACTURE AND USE 25 
 
 This trouble is eliminated by constructing a knock-down mold 
 (clamped at the ends) of the best straight-grained surfaced lumber, 
 putting in the face matter first and backing with coarse concrete, 
 the latter as wet as practicable. Of course it has often been ob- 
 served that faced work constructed in lumber forms shows the 
 grain of the wood. To obviate this the interior surfaces of the 
 mold and bottom board should be carefully sandpapered and shel- 
 laced. 
 
 Of the various methods used by different systems for supporting 
 floor joists the use of steel joist hangers is undoubtedly superior. 
 It not only permits of the unbroken construction of the wall but 
 also possesses a distinct advantage inasmuch as the floors are en- 
 tirely free from the walls, so that the burning of the former will 
 not cause the latter to fall. 
 
 As it is impossible to drive nails into concrete, it becomes neces- 
 sary to provide some means for fastening door and window trim, 
 base boards, picture molding, etc. This is best accomplished by 
 the use of a very excellent metal wall plug now on the market 
 which is laid in the mortar joints as the wall is building. 
 
 There is no reason in the nature of things why plastering 
 should not be applied directly to the interior of a wall built of 
 concrete blocks. Indeed, if the wall be regularly laid and the inte- 
 rior unfaced the surface is such that the priming coats may be 
 omitted and a coat of hard plaster applied directly to the blocks. 
 One must, however, be sure either that the blocks are waterproof 
 or that the construction of the wall is such as to prevent the pass- 
 age of moisture. Without the presence of one or the other of these 
 safeguards, furring and lath are as necessary as with ordinary solid 
 brick walls. 
 
 Not only may the superstructure be of concrete blocks, but the 
 foundation as well; the latter should be of a little heavier wall 
 and should rest upon concrete footing the depth of which must 
 be determined by the character of the soil and the width by the 
 load which the ground will sustain without deflection. It is very 
 important that these matters be definitely ascertained and a con- 
 siderable factor of safety allowed inasmuch as any settlement will 
 result in cracked walls. 
 
 The widths of walls considered necessary for ordinary build- 
 ings by the best authorities on concrete block construction are 
 approximately as follows: 
 
 For one-story buildings 8-in. walls. 
 
 For two-story buildings 10-in. " 
 
 For three-story buildings 12-in. and 10-in. " 
 
 For four-story buildings 15, 12 and 10-in. 
 
 In some cities the Department for Inspection of Buildings have 
 granted permits without question for constructing walls of the 
 
26 CONCRETE BLOCKS 
 
 widths mentioned. In other places rival interests have caused to 
 be passed ordinances prejudicial to the concrete block industry. Such 
 opposition is necessarily short-lived providing block makers use dili- 
 gence in universally maintaining that high standard of excellence 
 of which the industry is easily capable. 
 
 The matter of fireproofing of buildings is probably now receiv- 
 ing greater attention than at any previous time in the world's his- 
 tory. The attention of architects and insurance experts was ac- 
 tively drawn to concrete construction by the great fire-resisting quali- 
 ties manifested in the Baltimore conflagration and in numerous 
 fires of more recent date, and the interest thus aroused has led 
 to a number of experimental fires the results of which prove be- 
 yond a doubt that well-made concrete is not merely non-inflam- 
 mable but that it withstands the conflagration test far better than 
 any other building material in use at the present day. It is gener- 
 ally considered that concrete will disintegrate under the same ex- 
 tremes of temperature, or the same alternate subjection to fire and 
 water, that would cause decomposition in the stone composing the 
 aggregate. This view is erroneous inasmuch as the aggregates in 
 properly made concrete are protected by the surrounding matrix, 
 and the latter resists fire far better than any stone, granite not 
 excepted. Here, then, we see the prime importance of obeying the 
 law mentioned in the first section of this paper: Let every grain 
 of sand be thoroughly coated with cement, and let every piece of 
 gravel or stone be thoroughly coated with the sand-cement mortar. 
 
MANUFACTURE AND USE 
 
 27 
 
 The Manufacture of Concrete Blocks and 
 Their Use in Building Construction 
 
 Second Prize Paper in ENGINEERING NEWS Competition. 
 
 Wm. M. Torrance, M.W.S.E. 
 
 Anyone who contemplates the manufacture of concrete building 
 blocks, or construction by their use, should study the following 
 questions carefully: 
 
 1. Proper ingredients entering into concrete for successful 
 work. 
 
 2. Forms of blocks. Patent rights and their value. 
 
 3. Cost (1) Establishing an industry. 
 
 (2) Cost of product. 
 
 (3) Comparative cost of building of concrete blocks 
 
 and other materials. 
 
 4. Associated industries. 
 
 5. Engineering and Architectural considerations. 
 
 6. Success so far achieved in the industry. 
 
 7. Advantages possessed by an Engineer or Architect over 
 others in handling a successful business. 
 
 1. PROPER INGREDIENTS. 
 
 Concrete is generally defined as an aggregate of cement with 
 sand and gravel, or with sand and crushed rock, or simply with 
 crushed stone and the crusher dust and screenings from same, mixed 
 with the proper proportion of water to make a material which 
 can be molded into any desired shape while in a fluid, plastic, or 
 semi-plastic state, or only sufficiently damp to pack solid when 
 tamped; and which will "set" in this molded shape without defor- 
 mation, making an artificial stone. 
 
 Contractors and others have often used too little cement, or 
 cement of poor quality, in railroad work or other structures, and 
 the resulting failures and poor appearance have tended to dis- 
 credit concrete as a building material. In establishing a concrete 
 block business, therefore, no attempt should be made to use any 
 but the best of materials, including the water used, put together 
 in a correct manner and in proper proportions. None but the best 
 
28 CONCRETE BLOCKS 
 
 quality of Portland cement should be used by a concrete block 
 manufacturer if he wishes to have permanent success. 
 
 It is the best practice (in fact, the only correct practice) that 
 concrete should contain somewhat more than enough material of 
 each size of grain to fill the voids in the material of the next 
 larger grain. Thus there should be no less cement than will find 
 the voids in the sand, and no less sand than will fill the voids in 
 the gravel or crushed rock. In many of the so-called "concrete" 
 blocks on the market, only sand and cement can be used, which 
 do not make a "concrete" block in the ordinary use of the term 
 "concrete," but rather a "mortar" block; and this is not so strong 
 or so durable a stone as one to which body has been given by 
 addition of crushed rock or gravel. For any kind of good results 
 with such "sand and cement" blocks, however, more than enough 
 cement must be used to fill the voids of the sand, or the result will 
 be a porous product that will not withstand the elements, as a 
 porous product is bound to result, whatever the method used in 
 making the aggregate; and if too small a proportion of cement is 
 used, actual disintegration is bound to take place within a few 
 years or months. Of course, if the outer exposed face is composed 
 of a mixture which is made in the correct proportions, it would 
 tend to protect a cheaper mixture behind; but large railroad com- 
 panies and others who have used concrete extensively during a long 
 term of years are practically unanimous in making the whole body 
 of a concrete structure, however thick, of concrete in correct pro- 
 portions to fill the voids, and it is certain that the best work in 
 concrete must always be so done. If a richer facing mortar is 
 applied, or if the front portion of the block is made richer than 
 the remainder, great care is necessary to see that there is left no 
 plane or joint of cleavage. 
 
 Large users of concrete are very strict in their specifications, 
 requiring rigid inspection and tests. The N. Y. C. & H. R. R. R. Co., 
 tests, for instance, are so rigid, that of all the various brands of 
 cement on the market, their inspection bureau now only accepts 
 seven, which are the only ones used in the very extensive concrete 
 work being done by that company. Other large users are fully 
 as exacting. The result is that most of the inferior cement sold 
 is sold to the smaller consumer. He pays on the average a price 
 for cement as high or higher than the large consumer pays, as 
 he takes it in so much smaller lots; and what he gets is very apt 
 to be cement that would not pass rigid tests or fill proper specifica- 
 tions. 
 
 Not only the cement but also the other ingredients of the con- 
 crete should pass good specifications and tests. Every manufacturer 
 of concrete blocks should be sure that the ingredients are of the 
 
MANUFACTURE AND USE 
 
 29 
 
 best by making proper tests, and, no matter what the provoca- 
 tion, he should never "rob the job" by diminishing the cement 
 below the correct proportion, or by using a poor quality of water, 
 cement, sand, gravel, or crushed rock (the reader is referred to 
 the standard specifications of the U. S. Government, or those of 
 any large railroad company for specifications for good concrete in- 
 gredients). This is imperative if the prejudice against concrete 
 blocks is to be overcome. A large proportion of such "concrete" 
 block construction as is now going on in small places throughout 
 the country would, in large cities, be prohibited by the rules of 
 the building departments because of the defective material used, 
 or because the method of mixing is not satisfactory. 
 
 Concrete is mixed either "dry," "medium" or "wet." "Dry" con- 
 crete is made by use of only so much mixing water as will make 
 it of the consistency of molding sand when being worked. This is 
 then compacted by tamping, as molding sand is tamped. 
 
 "Medium" concrete is made by use of enough mixing water so 
 that water will flush to the surface by tamping or pressure. 
 
 "Wet" concrete is made by the use of enough mixing water so 
 that the concrete when mixed will pour, or into which, when first 
 deposited, men will sink at least to their ankles. 
 
 There have always been strong advocates of all of these pro- 
 cesses, but the tendency has been for large users of concrete to 
 change from the "dry" to the "medium," or to the "wet." This 
 change has been caused by results of many comparative experiments 
 and tests. 
 
 Specifications of many companies require "wet" concrete now, 
 where the same companies formerly specified "medium," and it 
 would now be hard to find standard specifications which required 
 a "dry" concrete. Certainly the "wet" and "medium" grades are 
 less porous than the "dry." "Dry" concrete, as made into blocks 
 by many companies, also suffers from lack of gravel or crushed 
 rock, which cannot be used in the process. 
 
 The catalogue of one of the larger manufacturers of concrete 
 block machines recommends the following proportions for the mix- 
 ture of cement and sand to be used in the blocks: 
 
 For foundation walls: 1 part cement, 3 parts sand. 
 
 For first floor walls: 1 part cement, 4 parts sand. 
 
 For second floor walls: 1 part cement, 5 parts sand. 
 
 For third floor walls: 1 part cement, 6 parts sand. 
 
 It is difficult to reconcile this sort of a recommendation to any 
 sort of reason. The voids in an average sand are not less than 
 about 30%. Therefore, in the 1:3 mixture, the voids will prob- 
 ably be well filled, and a compact, waterproof (or practically water- 
 proof) concrete might result with proper workmanship, but with 
 
30 CONCRETE BLOCKS 
 
 the 1:6 mixture, probably only a little over 50% of the voids are 
 filled. Blocks so made will be sure to absorb and hold a great deal 
 of moisture, and buildings made of them will be damp. Such blocks 
 will also disintegrate easily through the action of frost. 
 
 Although concrete made of ingredients aggregated in the cor- 
 rect proportion may be nearly waterproof, no concrete as ordinarily 
 made will be entirely so. On this account, there are in use many 
 materials or devices for making concrete impervious to moisture. 
 One firm handles a sort of jelly which is used in proportion of 
 one part of jelly to five parts of the cement used. This is mixed 
 in with the other ingredients of the concrete or in the facing 
 mortar. Another firm handles a "waterproof compound" which it 
 "puts up in paper sacks of 40 pounds each, and which is to be used 
 with from fifty to one hundred times its weight of cement." This 
 firm advertises that "cement with one per cent, of the waterproof 
 compound, with five parts sand gives a more impervious mortar 
 than ordinary untreated cement with two parts sand." Another 
 firm, of international reputation, advertises the use of a "stone 
 liquid" for coating brick work, stone masonry work, or concrete. 
 This is applied as a paint, the surface absorbing the liquid, which 
 becomes an insoluble compound, filling the pores in the facing of 
 the wall. 
 
 Another waterproofing device for concrete is to use 1% by weight 
 of alum with the sand and cement and 1% of soft soap with the 
 mixing water. The chemical action set up makes an insoluble com- 
 pound which practically fills all pores, making an impervious con- 
 crete. 
 
 The above are only a few of many processes employed. The 
 reader is referred to the advertising pages of engineering or scien- 
 tific journals for names of dealers in waterproofing materials, with 
 suggestions that literature from those firms be obtained and care- 
 fully studied. 
 
 No waterproofing scheme, however, will strengthen the con- 
 crete, and many methods for waterproofing damage the cement, and 
 this makes the concrete less durable. Certainly, a 1:5 concrete, 
 waterproofed, is not so good and durable as the 1:2 concrete, which 
 it is said to equal in moisture resisting quality. 
 
 It is probable, however, that waterproofing may often be wisely 
 done on the face of concrete, or incorporated in the whole body 
 of concrete (or at least in the facing mortar of same), whether 
 made in correct proportions or not. It can also be used wisely 
 in the cement mortar that is used in laying up concrete blocks. In 
 hollow concrete walls made by blocks of two-piece system this can 
 be made to prevent water or frost working through, even though 
 the blocks should be made of a porous mixture. 
 
MANUFACTURE AND USE 
 
 31 
 
 Blocks may be colored very economically without any harm 
 by means of iron or other pigments which are put up by various 
 manufacturers (Ricketson Mortar Color Co., of Milwaukee, Wis., 
 for instance) in a great variety of shades. It can be economized 
 by using it only in the facing of the blocks, if the method of manu- 
 facture permits a facing of different mixture thoroughly united to 
 the rest of the block. Concrete may also be colored at the same 
 time it is waterproofed by some processes, the stone liquid or water- 
 proofing jelly, for instance, being colored. 
 
 2. FORMS OF BLOCKS. PATENT RIGHTS AND THEIR VALUE. 
 
 When concrete first came into general use, it was probably 
 used mostly in making large blocks, at convenient places, to be 
 used, after becoming thoroughly set, in building large sea walls 
 and other heavy masonry structures. The idea of molding a mono- 
 lithic wall was a later development. The idea of making a wall 
 hollow for the sake of economy, or for prevention of moisture 
 or frost working through was a still later development. At the 
 present time, practically all concrete block manufacture is designed 
 for making a wall with hollow blocks, with continuous air chambers 
 in the fall, or by making blocks which, though perhaps not them- 
 selves hollow, will lay up into a hollow wall. 
 
 The steps leading up to the present state of the industry were 
 all patented by their inventors, and the man who desires to go 
 into a concrete building block business will do well to look thor- 
 oughly into the patent rights question. Many of these patents bear 
 recent dates, and their holders sell local county or city rights — 
 transferring such rights for so much money — and guaranteeing the 
 exclusive right to manufacture such a block or such a wall in the 
 territory in question. It is certain that many such patent rights 
 are good merely for the machine employed to make the block, and 
 are not broad enough to cover the block of the form made by the 
 machine, or the wall made of the blocks. Anyone purchasing patent 
 rights should bear in mind that patents are not always upheld by 
 law courts; therefore, he should use ordinary business caution to 
 see that the selling company's guarantee is good. 
 
 On November 17, 1850, Joseph Gibbs was granted Patent No. 
 13,071 by the British Government on several improvements in the 
 manufacture of cement and concrete. His patent included the 
 method, now so common, of building solid concrete walls by means 
 of timber forms or lattices on either side. The specification con- 
 tinues: 
 
 When it is thought advisable to dispense with the lattices and to make 
 the wall without any part of it being composed of wood, then in such cases, 
 blocks of the size of the stone of which the wall would be composed under or- 
 dinary circumstances are to be cast, only these blocks are to be hollow, having 
 only sides and ends, the sides and ends being made about two inches thick. 
 
32 
 
 CONCRETE BLOCKS 
 
 No. 80,358. 
 
 PATENTED JULI 28, 1868. 
 
 T. J. LOWRY. 
 MOLD FOR BUILDING BLOCKS. 
 
 0' 
 
 Plate I. — Lowry's Patent Mold for Building Blocks, 1850. 
 
MANUFACTURE AND USB 
 
 After every course of these b.'ocks have been built, the hollows must be filled 
 with concrete like that before described. The blocks being made to break 
 joints with each other, and being filled with cementitious matter, the wall 
 will become one mass of solid artificial stone, so there will be no necessity to 
 put mortar between the blocks to bed them. Instead of the blocks being cast 
 in the shape of hollow parallelograms they may have merely a back and face, 
 such back and face being held together by only as much cement or other ma- 
 terial as will keep such back and face in parallelism with each other during 
 the time they are setting (after which the filling must be the same as before). 
 It will be well to wet the blocks before concreting cement is put in, so that 
 they may all unite to form a solid mass of artificial stone. 
 
 Having described the second part of my invention, I declare that what 1 
 claim in respect thereof is as follows : 
 
 First — 
 Second — 
 
 Third — I claim the process of molding artificial stone by putting plastic 
 materials between lattices or other convenient forms, and also the method of 
 casting hollow parallelograms in cement to be afterwards filled up with con- 
 crete for artificial stone. 
 
 It is evident from this description that the inventor did not 
 intend to use his invention for hollow walls, but it is certain that 
 many walls were built in England and Scotland by both the sys- 
 tems above described in which the builders did not complete the 
 process, but left the wall hollow; and it seems possible that the 
 granting of this patent (which long ago expired) may be construed 
 as invalidating many more recent patents on hollow blocks and 
 hollow walls. 
 
 On July 28, 1868,* Thos. J. Lowry was granted U. S. Patent 
 No. 80,358 on a hollow block and wall, the block being almost the 
 exact shape of those made by use of many of the hollow block 
 machines or processes now in use. Plate I. of this paper shows the 
 drawing which accompanied the patent. This patent, of course, long 
 ago expired. 
 
 On April 14, 1874, T. B. Rhodes was granted U. S. Patent No. 
 149,678 on a great variety of forms of hollow building blocks and 
 hollow shingles, of "concrete or other material, which in its plastic 
 condition may be molded into the required form." Plate II. is 
 one of the three sheets of drawings which accompanied the patent. 
 In this patent, no method of molding the blocks is shown or called 
 for, or even suggested, so that a broad interpretation of the patent 
 would be that it granted Mr. Rhodes the exclusive right to make 
 blocks of these forms by any method of molding then known. It 
 may be noted from the date of this patent that it long ago expired. 
 
 The H. S. Palmer Co., of Washington, D. C, appear to claim 
 in their literature the right to control by virtue of their patents 
 the basic principle of hollow concrete building block machines with 
 
 •Since this article was submitted in this competition the writer has dis- 
 covered a still earlier patent ; viz., No. 53,004, granted March 6, 1866, to 
 C. S. Hutchinson on a hollow building block and wall making continuous ver- 
 tical air spaces. This block is remarkably similar in many respects to many 
 of the hollow building blocks on the market to-day. 
 
34 
 
 CONCRETE BLOCKS 
 
 T. B. RHODES. 
 Building-Blocks. 
 
 No. 149.678. Patented April 14, 1874 
 
 1M.ATE II. Rhodes' Building Block Patent, 1874. 
 
MANUFACTURE AND USB 
 
 35 
 
 removable cores and adjustable sides. Their patents also cover cer- 
 tain forms of block. Plate III. (A and B) shows the drawings accom- 
 panying Patent No. 674,874. This patent, and others controlled by the 
 same company, if rightfully granted, are evidently being infringed 
 on by the makers and users of a great many other machines. The 
 makers of these other machines and devices are practically unani- 
 mous in their claims that the Palmer patents, as far as the block 
 or wall is concerned, are void, and act up to this belief. Considera- 
 tion of the patent 80,358* to Mr. T. J. Lowry, of the patent No. 
 149,678 to T. B. Rhodes, and of the patent granted by the British 
 
 H. S. PALMER 
 No. 674,874 Concrete Wall for Building 
 
 (No Model.) (Application, filed Mar. 21, 1900.) 
 
 Plate III-A. 
 
 Government to Joseph Gibbs in 1850, naturally lead one to ques- 
 tion which is right, and all parties interested should insist on a 
 speedy determination of the matter. 
 
 To illustrate the trouble that is occurring, and may continually 
 occur, attention is called to the Hayden Block Machine. This 
 machine and whole outfit is sold by its manufacturersf to anyone, 
 
 ♦Also patent No. 53,004 to C. S. Hutchinson. 
 
 tHayden Automatic Block Machine Co., Columbus, O., and 26 Cortlandt 
 St., New York City. 
 
3G 
 
 CONCRETE BLOCKS 
 
 Fifr. 9 
 
 Witnesses : Inventor : 
 
 W. C. Coilies Harmon S. Palmer 
 
 Wm. Geiger 
 
 Plate III-B. Palmer Patent of 1000. 
 
 anywhere, for a definite sum, enough to net a fair machine shop 
 profit. They are willing to give with this outfit a bond for several 
 thousand dollars if desired guaranteeing the purchaser against 
 any patent troubles. The makers of the Hayden Block Machine em- 
 phatically deny that the manufacture of the blocks made on their 
 machine infringes any patent in force. Their machine, however,, 
 makes blocks almost precisely of the pattern of the Palmer block, 
 though in its construction it is almost entirely dissimilar to the 
 Palmer machine. 
 
MANUFACTURE AND USE 37 
 
 This question is a more serious one, on second thought, from 
 the fact that, if the patent holding company should take the ques- 
 tion to the court or' last resort, and procure a favorable verdict, 
 royalty could be collected from the contractor, or from the owner by 
 the patent holding company. 
 
 There are at least two types of block made of width equal to 
 tbe whole thickness of the wall in which there are no webs that 
 
 Plate IV. -Purdy & Henderson's Plan for Making Waterproof Blocks. 
 
 pass directly through the wall; viz., the "Miracle" and the "Blakes- 
 lee," both of which are patented. Plates No. VI. and No. VII. show 
 the drawings which accompanied the patents on these forms. These 
 two types, though accomplishing the same purpose, are different 
 in form. One makes a wall with vertical, the other with hori- 
 zontal air passages. Both of the companies holding these patents 
 have exclusive territorial rights to sell. (Miracle Pressed Stone 
 Co., Minneapolis, Minn., and Blakeslee Concrete Block Machine Co., 
 Columbus, Ohio.) 
 
 The first claim in the Blakeslee patent is "A building block 
 wherein there are no continuously solid portions from front to 
 rear." This patent was filed Dec. 19, 1903, and bears the date 
 May 24, 1904, the patent being No. 760,774. The third claim of 
 
38 
 
 CONCRETE BLOCKS 
 
 the "Miracle" patent covers ''A building wall consisting of concrete 
 blocks having two rows of air cavities, the cavities of the one row 
 being opposite and being larger than the intervals or necks be- 
 tween the consecutive cavities of the other row," etc. This is patent 
 No. 730,780, filed Dec. 1, 1902, and issued June 9, 1903. 
 
 Plate V. Comparative Test of Blocks to Show Relative Porosity. 
 
 The patent records show that application for a U. S. patent 
 on a multiple air space wall was filed Dec. 4, 1903, by Peter Dier- 
 lamm, of Stratford, Canada. This patent, No. 774,835, was granted 
 In November, 1904. The drawing accompanying this patent (Plate 
 VIII.) shows that this patented block is almost exactly the same 
 form as the Miracle block. Application for this patent was filed 
 prior to the application for the Blakeslee patent No. 760,774. 
 
 Plate VI., Fig. 3, shows a horizontal section of a portion of 
 a "Miracle" wall. Plate VII., Fig. 10, shows a vertical section of 
 a portion of a "Blakeslee" wall. The writer has added to Fig. 3, 
 Plate VI., three lines marked AA, BB, CC. These lines show how 
 four "Blakeslee" blocks would make one block similar in form to 
 a "Miracle" block turned on end. Practically the same thing would 
 be true of a block of the form patented by Peter Dierlamm. 
 
 The "Blakeslee," "Dierlamm," and "Miracle" blocks are improve- 
 ments on blocks of the "Palmer" type designed to prevent moisture 
 from passing through a wall by doing away with webs passing 
 direct from front to rear. Both the Blakeslee and the Miracle pro- 
 cesses use "dry" concrete, the machines being somewhat similar 
 to those used in the Palmer process, which also uses "dry" con- 
 crete. Nearly all the competitors of the Palmer Company which 
 makes blocks of forms like or similar to the Palmer blocks also 
 use "dry" concrete. The object gained by using "dry" concrete is 
 rapidity of manufacture, as a block may be removed from the 
 
MANUFACTURE AND USE 
 
 3& 
 
 machine as soon as it is tamped and the next block may be started 
 at once, which could not be done by use of "medium" or "wet" 
 concrete. 
 
 No. 730,780. PATENTED JUNE 9, 1903. 
 
 0. V. MIRACLE & W. L. DOW. 
 BUILDING WALL AND CONCRETE BLOCK FOR SAME. 
 
 APPL10ATI0S FILED DEO. 1, 1902. 
 
 ^1 °QI vol 
 
 \4 I * * 
 
 THE 
 
 
 
 
 ,,;,!! lil l 
 
 : 
 
 4\i 
 
 
 Or t/r f/e CZcs0Zizwc?e. 
 
 Plate VT. Miracle and Dow Patent of 1903. 
 
 Purdy & Henderson, of New York City and Havana, Cuba, have 
 recently invented a process which will allow the use of "dry" con- 
 crete in blocks made on a machine of the Palmer type, and yet 
 make blocks that will not allow the passage of water or frost from 
 front to rear. Plate IV. shows this improvement, which is described 
 as follows: 
 
 Pig. 1 on the accompanying drawing shows the block with the improve- 
 ment AAAA. It shows the position of the improvement in the webs of a 
 hollow block. If the block were solid the improvement AAAA would be con- 
 tinuous, running longitudinally through the entire block, and if it is desired 
 it is to be used continuously in the solid walls of the hollow concrete build 
 
40 CONCRETE BLOCKS 
 
 ing block. The partition or stratum represented by AAAA, in Fig. 1, which 
 is impermeable, may be made of a mixture of cement, fine sand, or pulverized 
 stone, or both, and hydrated lime, or other waterproof composition, such as 
 asphalt. 
 
 Fig. 2 shows the wedge-shape core B which is placed in the openings In 
 the block machine or mold in which the block is to be made. The block is 
 tamped or poured with the wedge-shaped cores in place. When the block Is 
 finished on top, the wedge-shape cores are drawn out and the waterproof 
 mixture, of which the stratum is formed, is poured into the opening, and it 
 becomes homogeneous with the balance of the concrete at once, and the block 
 may be removed as ordinarily and the waterproof stratum or partition will 
 remain in place. 
 
 What we claim as new, and what we wish to secure by letters patent is : 
 First, The wedge-shape core used in making the opening in the webs or 
 
 walls of the hollow concrete blocks or of a solid block for the partition or 
 
 stratum of waterproof mixture. 
 
 Second, The partition or stratum of waterporof material in the webs or 
 
 walls of the block as shown in the drawings. 
 
 (Signed) Purdy & Henderson, Inc., Inventors. 
 
 The inventors are using this process largely in Cuba at the 
 present time and, patent being applied for, have no competition 
 
 No. 760,774. PATENTED MAT 24, 1904. 
 
 F. W. BLAKESLEE. 
 BUILDING BLOCK. 
 
 4PPLI04TIOB TILED DEO. 19. 1903. 
 
 Platk VII. Blakeslee Patent of t904. 
 
MANUFACTURE AND USE 
 
 41 
 
 there. Patent rights on same will no doubt be for sale locally in 
 this country soon. 
 
 Plate V. shows a comparative test of two blocks of the Palmer 
 type. One is entirely of "dry," hand-tamped concrete; the other 
 is of the same material with the insertion by the method described 
 above of a wet mixture of broken stone concrete, no other water- 
 proofing being used. Note that moss is growing freely on the upper 
 surface of the unimproved block, while the improved block al- 
 lowed no moisture to pass up through to the top. At the time 
 this picture was taken both blocks had been resting in the water 
 side by side for eight months. 
 
 This test seems to the writer to be as good a proof as one could 
 wish of the much greater value of a "wet" mixture composed of 
 broken stone, sand, and cement, over a "dry" mixture composed of 
 only sand and cement. 
 
 There are on the market at present at least three processes 
 of hollow wall construction which do not use the "dry" concrete; 
 viz., by casting "wet" concrete in metal molds; by mixing "medium" 
 concrete and molding same under pressure by machinery; and by 
 casting "wet" concrete in sand. In all these processes gravel or 
 broken stone may be freely used. 
 
 The process of casting "wet" concrete in metal molds is com- 
 paratively cheap, one of the chief items of expense being the great 
 number of metal molds required. These are made with collapsible 
 core pieces and of hinged joints, so that, after setting, the block 
 may be removed. 
 
 Plate IX. shows the drawing which accompanied the original 
 patent No. 704,606, now owned by the American Hydraulic Stone 
 Co., of Denver, Colorado, on its "two-piece" system of hollow wall 
 construction. This company uses in its machinery "medium" con- 
 crete compacted by great pressure in the machine. There are nu- 
 merous advantages to this system over many others now in use, a 
 few of which are here given. 
 
 1. The chance to make the wall, and the individual webs of 
 the wall, any thickness desired, by simple adjustments of machinery. 
 
 2. The chance to use %-in. or 1-in. gravel or broken stone in 
 the aggregate, thus making a true concrete. 
 
 3. The patent rights held by this company are very broad, and, 
 if they will hold, they cover almost any conceivable arrangement 
 of blocks of concrete or other material in which the faces are of 
 separate pieces bonded together in the middle of the wall by T. L. 
 or channel projections extending into the middle of the wall. 
 
 4. The method of manufacture adopted by the use of the pat- 
 ented machinery of this company allows the use of sufficient water 
 
CONCRETE BLOCKS 
 
 No. 774.835. 
 
 PATENTED NOV. 15, 1904. 
 
 P. DIERLAMM. 
 BUILDING BLOCK. 
 
 APPLIOATIOH PILED DEO. 4, 1903. 
 
 ay 
 
 Plate VIII. Dierlamm Patent of 1904. 
 
MANUFACTURE AND USB 
 
 43 
 
 to make a "medium" mixture of concrete. The following claims 
 deserve consideration: 
 
 *It is indeed strange, after exhaustive tests on general concrete work have 
 so thoroughly demonstrated the ineffectiveness of a "dry" mixture, that so 
 manv should undertake to manufacture concrete blocks without sufficient 
 water to excite such hydraulicity as will secure that thorough crystallization 
 of the silicates of lime and alumina, without which the bonding of the aggre- 
 gates is imperfect and the concrete easily crumbled. Indeed, it would seem 
 that, eliminating the question of chemical activity, the mere physical problem 
 of combining materials to form the agglomerate should convince the practical 
 man that a "dry" mixture is not feasible, because if the cement be not re- 
 duced to a solution it can neither fill the voids nor afford necessary cohesive- 
 ness by thoroughly coating the sand and aggregate. 
 
 In considering the methods of manufacture, we notice that the system or 
 applying a heavy uniform, and almost instantaneous pressure is radically dii- 
 ferent from the customary method of tamping "dry" concrete. It is here that 
 the concrete block manufacturer has a decided advantage over monolithic con- 
 struction, as the application of a pressure at once adequate and uniform 
 eliminates squashing and sub-pressure, and secures a density and freedom 
 from norositv which a "dry" mixture cannot produce ; moreover, the applica- 
 tiXof such pressure on the face of the block, where the greatest density is 
 required, secures a face practically impervious to moisture and free from the 
 accumulation of soot and dust which has so often rendered cement houses un- 
 sightly. 
 
 The speed of operation under this system is merely limited by the time 
 taken to fi 1 the molds. As the mold runs into and out of the press on an 
 hon track and the pressure is made by one downward motion of the levers, 
 the PoDeratlor ^ requires less than four seconds exclusive of filling the mold 
 TTnde? ord narv conditions, it has been found that four men operating the 
 m^\na molL me mlxivive being supplied to them) will turn out enough 
 w L f n m«t7i nnn snuare feet of wall in ten hours; this rate can be ma- 
 ? SVV™ aVdX X ,C .S£m»t of elevated . bin., overhead mlxera, 
 
 mnin block it becomes a part of the blocK itseii. 
 
 main diock + nf wnlla the we ll-known prinpicle of the header 
 
 In the construction t of walls the weu * o F nsur i n g a resistance to 
 /%^ P «teial stie^s which cannot be expected in construction where 
 
 oS^ie'mere'V laid end To end without transverse bond. 
 
 5 The continuity of both horizontal and vertical air spaces. 
 One of the most ingenious devices of this system of laying walls 
 is the continuous horizontal air space which extends throughout 
 the wall making in effect two walls tied by the overlapping of webs 
 in alternate courses; thus a very thorough insulation is secured, 
 making a concrete wall construction impenetrable by moisture. 
 
 6 The securing of a very large percentage of air space. By 
 the use of pressure as above outlined, combined with the use of 
 true concrete and adequate moisture, this company has been able 
 to increase the air space in a wall from an average of 30% under 
 the one-piece systems to an average of 55% without any sacrifice 
 of strength. Thus a great saving is made in the amount and cost 
 of material and a corresponding decrease in the weight of walls, 
 while the increased air space saves 25% of heating bills, renders 
 a building cooler in the summer and affords walls practically dead 
 as to sound. 
 
 ~^o7e7from dictation by H. H. Rice, Secy, of American Hydraulic Stone 
 Co., Denver, Colo. 
 
44 
 
 CONCRETE BLOCKS 
 
 7. The ability, on account of the through bond, to construct 
 a wall of any length without providing expansion joints. Long 
 walls of "one-piece" blocks have given trouble where such joints 
 were not provided. 
 
 No. 704,606. 
 
 Patented July 15, 1902. 
 
 C. F. WHITTLESEY. 
 BUILDING BLOCK AND WALL. 
 
 (Application tiled Feb. S4. 1902.) 
 
 c 
 
 -B 
 
 c 
 
 
 JO 
 
 
 
 -3 
 
 c 
 
 
 
 
 Tlate IX. Whittlesey Patent of 1902. Owned by American Hydraulic Stone 
 
 Company. 
 
 8. The greater ability to use the inside surface of an outside 
 wall built by this process for a surface on which to plaster with- 
 out furring and lathing. Those blocks to be used for inside face 
 
MANUFACTURE AND USE 45 
 
 of the wall are left rough, without the application of a smooth 
 finish, so that an excellent bond with the plaster is assured, and 
 the wall being in two pieces can be kept in alignment very easily 
 so as to insure a uniform thickness of plastering. Plate X. shows 
 how continuous horizontal and vertical spaces throughout the wall 
 are obtained. 
 
 The process of casting wet concrete in sand is very adaptable 
 in buildings where the architecture requires arch stones, plain or 
 fluted columns, ornamental caps and sills to windows or doors, orna- 
 mental water tables and cornices, etc. 
 
 Patents Nos. 583,515, 699,587, 699,588, and 624,563, granted to 
 C. W. Stevens, are held by the Stevens Cast Stone Co., of Chicago, 
 on this process. This company, in applying for a patent in Germany, 
 was told that it was not believed possible to successfully cast con- 
 crete in sand, so men were sent to Germany to demonstrate the 
 process. The patent was granted. 
 
 These patents cover broadly the process of casting any shape, 
 more particularly hollow shapes, of concrete in sand molds or molds 
 partly of sand and partly of other materials. These molds are, in 
 many cases, substantially the same as for casting molten metal, and 
 the same quality of molding sand is used. It is questioned by many 
 whether these patents will hold, and there has been much concrete 
 block work done by this method where patent rights from the 
 Stevens Cast Stone Co. were not secured. It is certain that the 
 process of casting any molten metal in sand molds would not be, 
 at this late date, a patentable process. The Aberthaw Construc- 
 tion Co., of Boston, Massachusetts, cast all of the concrete steps 
 for the Harvard Stadium in sand molds, by use of patent rights 
 granted by J. C. McClennahan (Patent No. 711,436). This process, 
 in practice, is substantially the same as that employed by the Stevens 
 Cast Stone Co., the McClennahan patent using in the sand or other 
 mold a "hardening chemical solution." In practice, the writer has 
 been informed, a small proportion of sulphuric acid is added to the 
 water used in compacting the sand molds. 
 
 In Cuba this process seems to be open to competition to any 
 one who desires to use it, without regard to patents.* To the 
 writer's mind, a local manufacturer should use some process that 
 will accomplish the results of "casting in sand" to some extent 
 (however he establishes his right to do so) in order to be able to 
 take any work open to brick, stone or concrete. A man could, for 
 instance, acquire the local county or city rights for the American 
 Hydraulic Stone Co.'s process, which he could use for all the main 
 body walls, etc., and then could use "cast in sand" concrete for his 
 
 *The writer has since been informed that Purdy & Henderson control the 
 Stevens patents for Cuba, and regard other manufacturers as infringers. 
 
46 CONCRETE BLOCKS 
 
 lintels, sills, water tables, cornices, columns, arches, or any curved 
 bow windows required, using reinforcement of steel rods or wire 
 
 Plate X. Illustrating Continuous Horizontal Air Space in Wall Built on 
 American Hydraulic Stone Oo.'s System. 
 
 cloth, if desired, and be much better able to compete with stone or 
 brick work. 
 
 The literature of the Mandt Cement Block Co., Stoughton, Wis., 
 illustrates a novel multiple air space wall. This is a two-piece 
 wall, as may be seen by the illustration, Plate XI. This is de- 
 scribed quite thoroughly in "Municipal Engineering," July, 1905. 
 
 Plate XI. Multiple Air Space 'fl'all of the Mandt Cement Block Co. 
 
MANUFACTURE AND USE 
 
 47 
 
 Application for patent on this block and wall was filed May 10, 
 1905, and has not yet been granted. The bond is the same as 
 that of the American Hydraulic Stone Co.'s two-piece system. 
 (See Plate X.) 
 
 Ho. 776,409. PATENTED NOV. 29, 1904. 
 
 so model A. C. MATHER & M. F. BO WEN. 
 
 BUILDING BLOCK. 
 
 APPLICATION FILED JUNE 23, 1803. 
 
 Plate XII. Mather and Bowen Patent. (Owned by American Hydraulic 
 
 Stone Co.) 
 
 Attention is called to Patent No. 776,409 to A. C. Mather and 
 M. F. Bowen. Plate XII. shows the plan of this block, which when 
 laid up becomes a well-bonded wall with a hollow back, to the chanr 
 nel projections, on each block of which wire lath is attached for 
 
4S 
 
 CONCRETE BLOCKS 
 
 plastering. This form of block is one of the forms used by the 
 American Hydraulic Stone Co. in its patented "two-piece" wall, and 
 could easily be made of impervious broken stone concrete on the 
 machines of that company. The writer has seen no advertisements 
 of any company using this block, but it should become a much-used 
 form of wall. 
 
 The literature of the Queen City Brick Machine Co., Traverse 
 City, Michigan, illustrates a process of making ordinary sized bricks 
 of concrete composed of sand and cement, by pressure, by use of 
 their patented machinery (Patent 761,886). These bricks are all 
 of the same size and may be made with ornamental faces, etc. Such 
 concrete bricks should find a ready market, if the claims of the 
 machine manufacturing company are not exaggerated. 
 
 In closing the patent rights question, the writer would refer to 
 the list of patent numbers, etc., below, and would suggest that the 
 prospective manufacturer of concrete blocks should read copies of 
 these patents. These may be purchased from the U. S. Patent 
 Office for five cents per copy. 
 
 The reader could examine the "Official Gazette of the United 
 States Patent Office" for this purpose. This publication is issued 
 weekly ($5 per year), and gives a resume of all patents as issued. 
 A complete index is issued annually. Every volume of this publi- 
 cation is on the shelves of the Astor Library, New York City, or 
 in any large public library. This library also has on its shelves 
 bound volumes of the complete drawings and specifications of all 
 patents issued. 
 
 In 1904 alone about sixty patents bearing on the subject of 
 "building blocks" were granted. Even a casual observer can see 
 that many patents conflict. 
 
 Below is a list giving some of the more important patents: 
 
 IMPORTANT PATENTS BEARING ON THE SUBJECT OP CONCRETE 
 
 BLOCKS. 
 
 , Patent No. — ^ 
 
 Joseph Gibbs 13,071 (British Govmt.) 
 
 T. J. Lowry 80,358 
 
 Theodore Hyatt 142,475 
 
 T. B. Rhodes 149,678 
 
 375,377 
 
 H. S. Palmer Co., Washington, D. C. . 
 
 Miracle Prsd. Stone Co., Minneapolis, Minn 
 Blakeslee Concrete Block Machine Co., Co- 
 lumbus, Ohio 
 
 Peter Dierlamm 
 
 A. C. Mather and M. P. Bowen 
 
 J. C. McClennahan 
 
 674,874 
 727,428 
 730,780 
 
 623,686 
 727,427 
 759,010 
 
 Stevens Cast Stone Co., Chicago. Ill j 699,587 
 
 704,606 
 742,096 
 749,796 
 767,413 
 
 Am. Hydraulic Stone Co., Denver, Colo. . . { 769,601 
 
 769,656 
 771,816 
 773,630 
 I 775,347 
 
 760,774 
 744,835 
 776,409 
 j 698,727 ( 
 (. 711,436 j 
 624,563 
 699,588 
 733,928 
 743,391 
 767,398 
 767,414 
 769,655 
 769,816 
 772,032 
 773,647 
 
 Year. 
 1850 
 1868 
 1873 
 1874 
 [ 1887 
 
 tl904 
 1903 
 
 1904 
 1904 
 1904 
 
 1902 
 
 1897 
 1902 
 
 f 1902 
 1 1905 
 
MANUFACTURE AND USE 
 
 49 
 
 In purchasing patent rights one should, of course, be able to 
 trace the right to deal in them from the selling company back 
 to the patentee. The laws and court decisions relative to the com- 
 mon use of a patent by the employers of the man who developed 
 the patent, and by the inventor himself, should also be considered, 
 as he might purchase exclusive local rights of the one parly only 
 to encounter competition from the other. 
 
 3. COST. 
 (1) Establishing an Industry. 
 
 The amount of capital necessary to purchase a machine or out- 
 fit sufficient to make the equivalent of from 5,000 to 20,000 brick per 
 day is in no case more than from $200 to $600. To this must 
 be added credit or capital sufficient to obtain supplies, rent of land, 
 use of teams, etc., to suit local conditions. 
 
 If the form of block, or the whole process, is patented, an 
 additional sum must be paid for patent rights for the local use of 
 the process. The companies holding these rights are all ready 
 to sell exclusive local rights at rates ranging from $5 to $50 per 
 thousand population. Sometimes a part of this payment may be 
 made as a royalty on wall as made until whole contract amount 
 is paid. 
 
 It is usually best to establish the industry near the source of 
 supply of broken stone or sand, or near railroad yard or wharf 
 where such material may be unloaded. Inasmuch as any consider- 
 able business will require an extensive plant of tram cars and 
 sprinkler system to care for the blocks, etc., after being made, it 
 will usually be best to make the blocks at a central yard and 
 transport by team to the building site after they are cured and 
 ready for the wall. The machinery is usually so light and portable, 
 however, that for a large building it often pays to set it up at 
 the site, and if this is done, the blocks may be put into the wall 
 sooner after manufacture than would be the case if necessary 
 to team them. 
 
 The advertising pages of "Engineering News," "The Cement 
 Age," "Cement and Engineering News," "Municipal Engineering," 
 and many other scientific journals contain advertisements of those 
 firms which have been mentioned, as well as of many others. 
 "Municipal Engineering" (No. 1 Broadway, New York), July, 1905 
 ($0.25 per copy), contains advertisements of 58 companies in the 
 United States which make machinery or molds for the manu- 
 facture cf concrete building blocks, or associated products. All 
 of these companies have literature concerning their processes for 
 distribution, and the writer would suggest that much of this liter- 
 ature deserves perusal, and the advertisements themselves are well 
 worth reading. In corresponding with any of these firms, he 
 
50 
 
 CONCRETE BLOCKS 
 
 would suggest also that special emphasis be laid on inquiries con- 
 cerning patent rights, and concerning the ingredients which it is 
 possible to use in the concrete, including the proportion of water, 
 in order to determine probability of patent infringement legal trou- 
 bles, and probable quality of product to be obtained by the process. 
 
 (2) Cost of Product. 
 
 The cost of any concrete building block depends on two things: 
 The cost of the labor to mix the ingredients and that required to 
 put the mixture through the machine or process. Ordinary broken 
 stone concrete, mixed in proper proportions, in large masses, costs 
 in place from $4 to $8 per cu. yd., depending on local cost of in- 
 gredients, and on the shape and size of the masses put together. 
 
 To put such concrete through the American Hydraulic Stone 
 Company's machinery costs little more than the ordinary process 
 of putting it into wooden forms, with the cost of form work in- 
 cluded in the latter. Thus, in a wall made by this process with 
 50 per cent, hollow space, the actual cost to the manufacturer for 
 the blocks is just about 50 per cent, of what the cost would be to 
 build a solid concrete wall of the same outside dimensions, of 
 same grade of concrete. The cost of labor of laying up the wall 
 with these blocks is small, and so the total cost of the hollow wall 
 is not much more than half of the cost of the solid wall. The or- 
 dinary manufacturer of these blocks makes a handsome profit on 
 them at $0.15 or $0.18 per sq. ft. of wall, as the total cost may be 
 as low as 6 cts. or 8 cts. for correctly made concrete. The actual 
 cost of a 13-in. wall has been in some cases as low as 10 cts. or 11 
 cts. per sq. ft. 
 
 The cost of casting concrete blocks in sand is much greater, as 
 the labor item is so much larger, the molds being set up anew for 
 each casting, and labor of molding being comparatively high-priced. 
 In Havana, Cuba, Purdy & Henderson, and J. B. Clow & Son have 
 built a great deal of "cast in sand" hollow concrete block wall at 
 from $5 to $6.50 per square meter ($0.46 to $0.60 per sq. ft.) 
 
 The process of casting the blocks by pouring wet concrete in 
 metal molds is cheaper than by cas.ing in sand. The Stevens Cast 
 Stone Co., of Chicago, use this method for the straightaway work 
 on many of their buildings, using the "cast in sand" method for 
 only the ornamental or peculiar shaped blocKs required by the 
 architecture, but using the same "wet" mixture of broken stone 
 concrete througnout. This process is also used by the K. Dykema 
 Co., Battle Creek, Mich.; The Electrical Concrete Post & Stone Co., 
 Lake City, la., and several other companies. For the same grade of 
 concrete this process makes more expensive walls than the "me- 
 dium" concrete process of the American Hydraulic Stone Co., on ac- 
 count of the greater amount of outfit necessary. 
 
MANUFACTURE AND USE 
 
 51 
 
 Any concrete block machines on the market which use the 
 "dry" tamped process make blocks at prices which vary greatly 
 according to the grade of the mixture employed ($0.15 to $0.50 per 
 sq. ft. of wall). The tendency of this process is to use too little 
 cement in order to keep the cost down, as it is possible to use only 
 sand with the cement. Blocks made in correct proportions by 
 this process would cost nearly as much as, or more than, concrete 
 blocks of broken stone, sand and cement, made by the "cast in 
 sand" process. 
 
 (3) COMPARATIVE COST OF BUILDINGS OF CONCRETE AND 
 OTHER MATERIALS. 
 
 The literature of nearly all of the manufacturers of concrete 
 block machinery contains statements of comparative cost of walls 
 made of their product, and of ordinary brick, stone and wood. A 
 careful perusal of this literature, or an investigation of workman- 
 ship, would show that many of these comparisons are overdrawn, 
 or that, in order to make so cheap a wall as described, a poor mix- 
 ture of concrete was used, and that the labor employed was not of 
 the highest class. 
 
 In our large cities, labor unions control the building trades, 
 but, as far as is known to the writer, neither union masons nor 
 union bricklayers have as yet refused to lay a wall of concrete 
 blocks, though these blocks were made by non-union labor. Trou- 
 ble on this score is probably in store, however, if it ever assumes 
 large proportions. The above mentioned unions have close working 
 agreements with the stone cutters' union, the hod-carriers' union, 
 etc. Unions of concrete workers demanding standard wages of the 
 hod-carriers' union have already been formed, and if these unions 
 become powerful, -the item of labor will be increased, as the union 
 bricklayers and masons who lay the wall will undoubtedly insist 
 on having the concrete blocks made by union laborers. At the pres- 
 ent time brick and stone masonry walls are built entirely by union 
 labor from the brickyard and the quarry to the finished wall, and 
 ultimately brick, stone and concrete work will all be on the same 
 status in this respect, which is not the case at present. 
 
 It is certain, however, that concrete blocks are cheaper than cut 
 stone, of the same durability, and much more adaptable, and for a 
 hollow wall, concrete blocks cannot be successfully competed with 
 by brick or stone. It is customary for concrete block machinery 
 companies to compare the cost of the hollow wall of their product 
 with a solid brick wall of same dimensions. It should also be re- 
 membered that the hollow concrete wall — if built by any moisture- 
 proof process — does not need to have furring strips fastened to 
 the inside for lathing and plastering. On a brick wall this furring 
 anu lathing are necessary, and so the comparison is still more in 
 
*>2 CONCRETE BLOCKS 
 
 favor of the hollow concrete block wall. Moreover, the hollow 
 concrete wall, of same size and strength as the solid brick wall, 
 weighs only 50 per cent, to 75 per cent, as much as the latter, so 
 money may be saved on the foundation, if on yielding soil. 
 
 In general, at the prevailing price of materials, building walls 
 may be built of correctly made concrete blocks for from 40 per cent, 
 to 75 per cent, of the cost of brick walls, or from 25 per cent, to 50 
 per cent, of the cost of cut stone or fancy brick. In fact, by some 
 processes a house may be constructed of this material for the cost of 
 a good frame house, and the owner has the advantage of a non- 
 burnable construction as well as of a much warmer building. 
 
 It should be noted, however, that the process, comparatively new 
 in this country of making sand-lime brick may be destined to reduce 
 the cost of brick walls to about 60 per cent, of their present cost. 
 This process has been in use in Germany for many years. The ease 
 with which bricks of a perfectly uniform size are turned out at a 
 cost to the manufacturer of from $3 to $5 per M. renders them formid- 
 able competitors with any other building material. The reader is 
 referred to "American Sand-Lime Brick Co.," 1307 Great Northern 
 Building, Chicago, 111., for data relative to this process. The Para- 
 gon Plaster Co., of Syracuse, N. Y., are successful . manufacturers 
 of these bricx, as well as of the American Hydraulic Stone Com- 
 pany's "two piece" system of concrete blocks. 
 
 The process of "casting in sand" will successfully compete with 
 cut stone or terra cotta for ornamental cornices, columns, balus- 
 trades, etc., for all places except perhaps points very near to the 
 quarries or terra cotta works. For the same, or equally good ap- 
 pearance, and the same durability, the "cast in sand" process should 
 not cost more than 60 per cent, of the others, while from the stand- 
 point of fire-resisting qualities, there is no comparison, as the 
 concrete would pass without damage a fire test under which cut 
 stone or terra cotta would crumble. 
 
 A further comparison might be made by considering hollow 
 walls built up of two separate walls of brick bonded together by 
 metal strips, but to make a good and permanent wall by this 
 method requires a very good metal. Galvanized iron, or copper 
 strips should be used, and even these will sometimes rust through, 
 so that the life of such a wall is not to be considered as great as one 
 entirely of concrete materials. 
 
 Brick walls are often built in this manner, sometimes using an 
 occasional "header" brick for the bond instead of metal strips. 
 The cost of a hollow concrete wall will usually not be much less 
 than a brick wall of same outside dimensions, built in this manner, 
 but it will be stronger on account of the more thorough bond. 
 
 Under present conditions, it is certain that hollow concrete 
 
MANUFACTURE AND USE 53 
 
 wall construction is cheaper than an equally good wall of other 
 materials. This because of the cheapness of crushed rock and 
 sand, in nearly every locality, and the abundance of good cement 
 mills all over the country. For brickwork, stone or terra cotta, 
 proximity to the brickyard quarries plays such an important part, 
 rendering the cost of construction at any considerable distance from 
 these places very great on account of freight charges. 
 
 4. ASSOCIATED INDUSTRIES. 
 
 Fence posts, telegraph poles, flag stones, roofing slabs, sewer 
 pipes, piles, solid concrete brick of ordinary brick size, etc., are 
 made successfully of concrete. In any locality there is also a great 
 deal of concrete work in cement sidewalks, concrete floors, con- 
 crete roofing and basement paving, concrete steps, etc., that is con- 
 stantly open to contractors. 
 
 A concrete block manufacturer could, in almost any locality, 
 carry on some, or all, of these other lines of work to good advan- 
 tage. He would also find in many places a good chance to engage 
 in a mercantile business in cement, sand, crushed rock, etc. Such 
 a business might enable him to purchase his own supplies in larger 
 quantities, and hence on better terms. 
 
 5. ENGINEERING AND ARCHITECTURAL CONSIDERATIONS. 
 
 The concrete block business is not growing as it should. This 
 is largely due to the objections raised by civil engineers and archi- 
 tects. The civil engineer argues that the ingredients in the con- 
 crete are not the proper ones, that too little water is used in mixing 
 to make the block a success, and that the wall as built needs to 
 be provided with expansion joints in spite of the bonding. The 
 architect argues that, in spite of the claims to the contrary, the 
 walls will be wet, and moisture will work through and spoil the 
 decorations inside where plastering is done directly on the block; 
 that the wall as made looks too artificial; that, if made of "rock 
 faced" blocks, the patterns adopted are too much alike, and there 
 are no sharp corners as in cut stone; that this makes the wall look 
 as though it were faced with galvanized iron, stamped to imitate 
 rock faced blocks, and then painted with a sand paint or cement 
 grout; that in any case a concrete wall cannot be made to look like 
 cut stone work; that the concrete presents such a poor appearance 
 when wet, etc. 
 
 It is possible, however, to make concrete block buildings not 
 subject to these objections. Purdy & Henderson, of Cuba, and the 
 Stevens Cast Stone Co., in the United States, have erected build- 
 ings by the "cast in sand" process that do look like cut stone. The 
 same is true of other processes. The poor appearance of wet con- 
 crete may be entirely obviated by choosing the sand and broken 
 
54 CONCRETE BLOCKS 
 
 stone carefully. Clear white sand and crushed rock, with no iron 
 or other coloring matter contained, are procurable, and if used give 
 good results. 
 
 The reason for the necessity of providing expansion joints in a 
 long wall of concrete blocks is that the wall is not bonded thor- 
 oughly enough. This defect is obviated in the best concrete block 
 work. 
 
 Plate XIV. Miramar Hotel, Havana, Cuba. Built by Concrete Blocks by Purdy & Henderson! 
 
 The engineering and architectural authorities will be con- 
 vinced by good result?, and good results may be obtained. These 
 professions are conservative. Therefore, great care and good work- 
 manship must be used by the manufacturers of machinery, and 
 ol the blocks, to get their unqualified indorsement, without which it 
 will never become an important industry. 
 
MANUFACTURE AND USE 55 
 6. SUCCESS SO FAR ACHIEVED IN THE INDUSTRY. 
 From an artistic standpoint, the best success in the industry 
 has so far been achieved by means of the process of "casting in 
 sand." In Havana, Cuba, this process has been extensively used. 
 Plates XIII. and XIV. are photographs of "The Royal Bank of 
 Canada" building, and the "Miramar" hotel building, both built by 
 Purdy & Henderson, of sand-molded blocks, except the flat portions 
 
 Plate XV. Concrete Blocks Cast in Sand at Havana. 
 
 of the wall near the second story windows in the Miramar, which 
 are "dry" tamped blocks of the "Palmer" type. For reasons noted 
 above, these buildings were quite expensive. Plate XV. shows a 
 group of "cast in sand" blocks from Havana, and Plate XVI. shows 
 a residence under construction. 
 
 In Cuba the ordinary "dry" hand-tamped block construction of 
 the "Palmer" type has been largely discarded after having a good 
 trial, as the slanting rain of the rainy season put moisture through 
 walls built of such blocks in a few hours, and the firms now put- 
 
Plate XVII. New Armory Building, Ames, Iowa. Built of Miracle Concrete Blocks. 
 
Plate XVIII. Hotel Angelus, El Paso, Texas. 
 Built of American Hydraulic Stone. Co.'s Concrete Blocks. 
 
 ting up buildings of concrete blocks use either "cast in sand" 
 blocks or "dry" tamped blocks made impervious by the new in- 
 vention of Purdy & Henderson described and illustrated above. 
 
 Plate XVII. shows the new armory building at Ames, Iowa, 
 
 Plate XIX. Office Building of National Electric Co., Milwaukee, Wis. 
 Built of American Hydraulic Stone Co.'s Concrete Blocks. 
 
 built of "Miracle" blocks. This is a very handsome building and 
 a credit to the Miracle Pressed Stone Company, Minneapolis, Minne- 
 sota, whose product makes a wall practically free (as a whole) 
 
58 
 
 CONCRETE BLOCKS 
 
 Plate XX. Portion of Wall of Residence Built of "Normandin" Blocks. 
 
 from moisture on account of the "double air space" obtained in the 
 wall. The Miracle Pressed Stone Company have granted their 
 local patent rights to a great number of block manufacturing 
 plants in the United States and Canada, and their testimonials from 
 users from all latitudes show good protection from moisture, frost 
 or temperature changes. 
 
 Plate XVIII. shows the Hotel Angelus, El Paso, Texas, and 
 Plate XIX. shows the office building of the National Electric Com- 
 pany at Milwaukee, Wisconsin, built of the blocks of the American 
 Hydraulic Stone Company. In this building these blocks have also 
 been used for inside work. 
 
 The Naugatuck Chemical Company, 25 Broad Street, New York 
 City, have recently erected a large building at Naugatuck, Conn., 
 of these American Hydraulic Stone Company blocks, of which they 
 are justly proud. Tnis building is said to have cost 25 per cent, 
 less than a common brick building would have cost, and a much 
 better, and better looking building is the result. 
 
 Plate XX. is a photograph of a portion of a residence of Nor- 
 mandin -blocks- (dement Machinery Company, Jackson, Michigan), 
 showing a good imitation of cut stone. 
 
MANUFACTURE AND USE 59 
 
 There has been much very unsatisfactory work in concrete 
 building blocks. Most of this is traceable to the greed of the build- 
 ing block maker who, in order to reduce the cost and increase his 
 profits has used poor concrete. The writer is well acquainted with 
 a building built of "dry" tamped hollow blocks of the "Palmer" or 
 "Normandin" type in which plastering on the inside of the walls 
 was done directly on the blocks. The maker of the blocks stated 
 that the hollow spaces insured dryness. The building is a very 
 damp one on account of the porous nature of the concrete, both on 
 account of being made a "dry" mixture, and on account of a too 
 small proportion of cement in the concrete. Such a failure has 
 given the concrete block business a set-back in that locality in the 
 very beginning. 
 
 It must be remembered that there can be as much difference 
 in imperviousness between a concrete block wall made of true 
 broken stone concrete in "medium" or "wet" mixture, and a wall 
 made of "dry" hand-tamped standard cement blocks, as there is 
 between a vitrified paving brick and a common soft brick. 
 
 7. ADVANTAGES POSSESSED BY AN ENGINEER OR ARCHI- 
 TECT OVER OTHERS IN HANDLING A SUCCESSFUL 
 BUSINESS. 
 
 In first-class cut stone or terra cotta work, such block is made 
 to size and shape from the plans made by the engineer or architect. 
 In successful concrete block manufacture, each block must also be 
 to size and shape from the plans, otherwise the resulting wall will 
 not present the best appearance. The writer has seen concrete 
 block walls in which joints in the successive courses of the wall 
 were not broken, also walls in which the blocks have been cut by 
 stone-cutters' tools after manufacture, simply because of lack of 
 plans and proper supervision for the laborers employed in making 
 the blocks. The reader is referred to an article in "Municipal En- 
 gineering," May, 1904, which illustrates this point. 
 
 An engineer or architect who, by education and training, is 
 perfectly capable of making plans and laying out, or directing the 
 laying out, of such work, and who is capable also of directing a 
 business will have great advantage over a man who has no such 
 training, and who therefore tries to do without such ability, or is 
 forced to hire it. The partnership of a hard-headed business man 
 and an engineer or architect would have its advantages. An engi- 
 neer will usually have an advantage also in being better qualified 
 to make or supervise tests of materials, etc. 
 
 The writer has had occasion above to refer to the work of Purdy 
 & Henderson in Cuba. The success of this firm in concrete build- 
 ing block construction has undoubtedly been largely due to the en- 
 gineering and architectural ability at its disposal. 
 
60 CONCRETE BLOCKS 
 
 The engineer and the architect are much more familiar with 
 matter pertaining to the strength of materials, and are much more 
 apt to insist on good and thorough workmanship in their work than 
 competitors without their training. 
 
 CONCLUSION. 
 
 It has been said that this is the "Age of Concrete." Cement 
 manufacturers no sooner get their mills built than they are working 
 overtime to fill orders. The growth of the cement industry is enor- 
 mous, and shows no signs of ceasing. The demand for concrete in- 
 stead of heavy masonry for bridge work; for reinforced concrete in- 
 stead of structural steel and brick walls for sky-scrapers, or indus- 
 trial establishments; instead of brick or hollow tile and structural 
 steel beams for floors; instead of brick or stone for dams, sewers, 
 aqueducts, etc., is a steadily growing one. Now comes the demand 
 for concrete block walls for buildings instead of brick, stone or 
 timber. 
 
 A concrete block business if founded on correct business prin- 
 ciples as outlined in this article is almost sure to succeed. It is 
 already an assured success in many places. 
 
 A business of erecting buildings of concrete building blocks 
 with reinforced concrete floors and roofs is sure to be a popular one 
 before very long. Many such buildings are now in use. 
 
 Not the least important consideration in concrete work is its 
 great safety in case of fire. It has been shown that concrete is one 
 of the very best materials of construction to resist fire. In the 
 great Baltimore fire the buildings not destroyed were nearly all 
 of concrete. 
 
 In this connection it is well to divide concrete into classes. 
 Concrete walls made by any process giving a porous wall which 
 will absorb moisture, will not withstand fire as well as concrete 
 so compact that no moisture can be contained. In the one case the 
 wall as a whole, on account of air space, double air space, intro- 
 duction of water-proofing strata, etc., might be slow to allow moist- 
 ure to pass entirely through the wall, but in case of fire, the con- 
 fined moisture, previously absorbed, may become steam and crumble 
 the wall. The writer would refer, in this connection, to an article 
 by Noyes F. Palmer, in Engineering News, July 13, 1905. 
 
 In general, however, the concrete building will prosper largely 
 on account of the growing demand by owners of buildings that they 
 shall have safety from fire to themselves, their families, or their 
 business, and that they shall have lower rates of insurance or be 
 able to do without insurance. 
 
MANUFACTURE AND USE 
 
 61 
 
 The Manufacture of Concrete Blocks and 
 Their Use in Building Construction. 
 
 Extracts from Papers Submitted in ENGINEERING 
 NEWS Competition. 
 
 Besides the two papers given, which were awarded prizes in The 
 Engineering News competition, there were received several others, 
 nearly all of which contained contributions of value to the knowledge 
 of the subject of concrete block manufacture and use. From these 
 papers selections have been made and arranged under descriptive 
 headings. 
 
 The names of the writers from whose papers extracts have been 
 taken are as follows 
 
 Joseph Babiczky, Kansas City, Mo. 
 George H. Crafts, Atlanta, Ga. 
 H. H. Frantz, Des Moines, la. 
 U. G. Hayne, Fort Stevens, Ore. 
 Noyes F. Palmer, Brooklyn. 
 H. H. Rice, Denver, Colo. 
 H. G. Richey, Evanston, Wyo. 
 G. W. Robertson, Marion, O. 
 G. W. Stevens, Boston, Mass. 
 
 LOCATION OF PLANT. 
 U. G. Hayne. — The points to be considered in establishing a con- 
 crete block plant, or factory, are many and various, every locality 
 presenting different difficulties and problems to be settled. The one 
 vital question to be thoroughly looked into and decided before in- 
 stalling a plant in a locality, is: "Will it pay?" In connection 
 with this query must be considered the climatic conditions, and 
 the kind, price and quality of the building materials provided at 
 hand by nature. The facility and cheapness with which good mate- 
 rials can be obtained for making blocks in the locality under con- 
 sideration should also be closely investigated. It may be that the 
 custom of using a certain building material in a community is so 
 set that in order to get a trade established it will cost considerable 
 
62 CONCRETE BLOCKS 
 
 in advertising, rustling and time before good results can be obtained. 
 With enough capital this question is easily settled, but it may mean 
 failure to a man of small means before he can get returns. 
 
 In years past some one may have so handled concrete work in 
 a locality that a prejudice exists against its use; he having used 
 a poor quality of sand, gravel, or possibly cement; though an even 
 chance poor workmanship. It little matters what the error has 
 been; results will be slower and more expensive until this senti- 
 ment is overcome. Therefore the place not so hampered, for the 
 man of small capital, is the best; though a hustler with good goods 
 to make good with, can win out in any community. 
 
 A locality that has supported a brick-yard of any size should 
 be able to furnish work for a block plant, though there are many 
 such places where the cost of transporting the sand, gravel and 
 cement will practically prohibit manufacturing blocks at a profit. 
 While, on the other hand, all the materials for block-making may 
 be close at hand, and cheap, in a locality that has no materials for 
 brick-making. 
 
 Stone in some places may be cheap enough to materially in- 
 terfere with the use of concrete blocks on account of cost. I think 
 that such cases are rare. No doubt but that brick cuts a more im- 
 portant figure, though I know of instances where the price of brick, 
 a few years ago, could not be touched with concrete for foundations 
 even, including basement walls; where now more than half the work 
 is concrete, and growing in favor. Timber in some localities has to 
 an extent kept out concrete, and will for some years to come; but 
 owing to a material advance in the price of lumber, conditions are 
 changing. 
 
 Having decided on the community or town in which to locate, 
 the next item to be considered is the location of the plant. This 
 should be as nearly as possible so situated that the cost of trans- 
 portation will be reduced to a minimum. The cartage on the fin- 
 ished block will be, in most instances, more for the same distances 
 than that of the raw materials. So a location central for the finished 
 product should be looked for, at the same time keeping in mind 
 that, if possible, a location near a railroad siding will be very con- 
 venient. On account of receiving cement, and, in many instances, 
 sand and gravel, by rail, the expense account can be kept down, as 
 well as being in a position to make shipments of the finished prod- 
 uct, with all cartage cut out. Where water transportation is pos- 
 sible, it should be considered in this connection. 
 
 The plant should be located where water under pressure can 
 be cheaply obtained, either from the city mains or a system con- 
 structed for the purpose, as water under pressure must be had for 
 sprinkling the blocks and the various uses of the factory. 
 
MANUFACTURE AND USE G3 
 
 In many instances an old mill building or warehouse with suf- 
 ficient ground adjoining for a yard can be utilized much cheaper 
 than constructing a building. 
 
 H. G. Richey. — As the location of the plant will be one of the 
 first considerations in starting a concrete block business, the points 
 to be given the most attention are, the market for the finished 
 product and the proximity of the raw materials; and then after 
 the plant is in operation to turn out a finished product equal or a 
 little better than any other like material on the market. Rather 
 make a high-priced good block than a low-priced poor one; for no 
 person will wish to buy a poor block at any price, but generally 
 people will pay a good price if they know they are getting a good 
 block and their money's worth. 
 
 A concrete block plant should be so located that the bulk of 
 the materials to be used can be obtained with the least expense 
 possible. As the broken stone or gravel forms the larger quantity 
 of material to be used, the plant should be, if possible, located 
 adjacent to this supply; if this point is on a railroad, it will also 
 save the expense of hauling the cement from the car to the plant. 
 Another advantage of being located on a railroad is, that the fin- 
 ished blocks can then be shipped by rail to other points, and there 
 will be no expense of hauling from the plant to the car. 
 
 DESIGN AND ARRANGEMENT OF PLANT. 
 
 U. G. Hayne. — In parts of the country where the winters are 
 cold, a basement, in which to work the men making blocks for the 
 spring trade and to keep the crew together, would be a good in- 
 vestment. Should the location selected have a plot of ground that 
 can be secured and converted into a factory, such as will answer 
 the purpose of the block manufacturer, he can use his best judgment 
 in arranging it to suit his requirements. 
 
 In case he has to build and his capital is limited, a cheap wood 
 building large enough to hold about four days' work, with a floor 
 of fine sand, and windows so placed as to give a good light about 
 the part of the building where the making of the blocks is done, 
 will be sufficient in size to start with. 
 
 As the blocks must be kept from the sun and wind as mush 
 as possib.e for about ten days, the yard can be so arranged as to 
 keep off the wind by fencing, and on sunny days canvas can be 
 spread over the blocks in the yard which have not been stacked 
 out over six days, or, in other words, over those blocks that are 
 being kept wet. For an output of about 1,000 blocks per week a 
 room will be required approximately 30 ft. wide by about 80 ft. 
 long for the machine, mixing-platform, and room for curing the 
 blocks. By stacking and re-handling the blocks once, this room is 
 large enough to double the capacity. 
 
64 CONCRETE BLOCKS 
 
 A close-built mixing platform about 12 ft. x 14 ft. should be 
 placed alongside the block machine, which must be in such a posi- 
 tion as to make it handy to the materials, preferably close to one 
 side of the building. The sand or gravel can then be shoveled di- 
 rectly onto the platform from the outside. Where a mixer is to be 
 used, the plant can be so' arranged that the materials may be placed 
 in the mixer by machinery, or by gravity, thus doing away with 
 practically all shoveling. 
 
 When it comes to a factory the size of which it will pay to 
 so arrange that all mixing, tamping, etc., is done by machinery, 
 the party interested in installing it should take sufficient time and 
 money to investigate the subject thoroughly, and know just what 
 he is doing. My object in this article is to give any information 
 I can that may be of use to the man who has to start in a small 
 way at making blocks or not be able to start at all. 
 
 In large plants an arrangement of tracks and cars will be 
 very necessary in handling the blocks about the building and yard. 
 Most machine companies have cars and tracks for handling and 
 curing the blocks, and can give the best arrangement of them for 
 handling the output of their respective machines. 
 
 The factory should be so piped that the new-made blocks can 
 be easily and cheaply wet down with a spray of water from one 
 or more sprinklers. 
 
 The arrangement of the yard, to facilitate the loading of the 
 finished work, for transportation to the place where they are to be 
 used, with roads through it at convenient intervals for driving 
 trucks, should not be forgotten. 
 
 In most cases it will be best to make the blocks at the factory, 
 and haul them to the place where they are to be used in the build- 
 ing. Yet where a large number are under consideration, at 
 a distance from the factory, it may be profitable to make them on 
 the site of the building to be constructed. A contract or two of this 
 kind would save enough to purchase a tent of sufficient size for the 
 purpose that could be used to good advantage on similar work. 
 
 Included in the plant are the shovels, hoes, etc., for mixing; the 
 hose and piping for wetting down the blocks, etc. 
 
 Some of the various companies selling machines make a metal 
 bottom board or pallet for making and curing the block on, and 
 which has the advantage of not being liable to check or crack 
 the stone as a wood pallet is apt to do, on account of the wood 
 swelling by absorbing the moisture from the block. Should the 
 wood pallet be kept wet and watched on account of the shrinkage 
 from drying out, they are all right, and much cheaper. 
 
 A factory such as spoken of, with the building only high enough 
 
MANUFACTURE AND USE 65 
 
 to work in, and ready for the machine should cost from two hundred 
 to five hundred dollars. 
 
 G. W. Robertson. — One wishing to engage in the making of 
 blocks, etc., should first select a suitable location after having ascer- 
 tained probable cost of cement, sand, crushed stone, etc., and finding 
 out probable price he can get for blocks. A location should be 
 selected as handy as possible for the handling of material of all 
 kinds, also for shipment of product, and not too cramped for 
 storage room, as in the handling, re-handling, piling, etc., money 
 is either made or lost. In this business, as in any other, it is 
 the seconds that count. Therefore, it stands you in hand to have 
 everything convenient. The shed or shop for making block, mixing 
 concrete, etc., can be light and airy, while the part of shed where 
 blocks are placed after making should be rather dark, or at least 
 protected from sun and wind till they are fit to move into the 
 yard, this in spite of the claim made by some that blocks can be 
 made either out in the sun, or any old place that may be handy, 
 and given no protection. In arranging the shed or shop, care should 
 be given to have the place for cement as dry as possible. 
 
 Joseph Babiczky. — In a large city where a well-organized con- 
 crete block company is working successfully, it is perhaps advisable 
 to build a regular factory equipped with the most perfect machinery 
 for turning out high-class and speedy work. Start in always, how- 
 ever, with a tent plant, and when you see that you are successful 
 in the business, consider a permanent plant. In the following table 
 I give the price and size of tents for various daily outputs of con- 
 crete blocks: 
 
 Dimensions, Daily capacity, 
 
 ft. Area. No. blocks. Cost of tent. 
 
 40X61 2,076 sq.ft. 300 $150 
 
 44X65 2,444 " 400 175 
 
 44X72 2,752 " 500 190 
 
 48X76 3,152 " 700 215 
 
 52y 2 X80y 2 3,633 " 950 350 
 
 After it is seen that it is absolutely necessary to put up a 
 permanent factory, equipped with power mixer, power presses and 
 molds of various sizes and kinds, the tent outfit, with the hand 
 machines, can be used as a "flying factory,'" which can be packed 
 up in a few hours and shipped to any place outside the city where- 
 work may be contracted for. I think that the shipping of concrete 
 blocks is very seldom profitable, on account of high transportation 
 rates, cost of handling and packing, and loss from breakage. 
 
 Geo. H. Crafts. — In order to make blocks in the cheapest way, 
 judgment should be used as to the proper location of the plant for 
 business, and the location and design of the buildings and placing 
 of the machinery therein so as to bring the operating expenses 
 down to a minimum. If possible, it is best to locate the plant near 
 a good sand bed, as sand is one of the principal materials used. 
 
66 
 
 CONCRETE BLOCKS 
 
 Then the buildings should be located so that the sand can be gotten 
 into the bins with the least expense, and the bins should be of 
 ample capacity to keep a surplus of dry sand on hand at all times. 
 The boiler and engine, pump, press and mixer, should be so placed 
 that the material can be put through the different processes of 
 proportioning, mixing, pressing and curing with as little handling 
 as possible, and so that the processes can be carried on continuously 
 and with as little interference of one operation with another 
 as is possible. The mixer should be placed so that the 
 materials can be measured and charged into it from the 
 sand bins, and discharged from it in close proximity to the 
 loading platform. The platform should be in line with the press, 
 and the transporting apparatus such that the material can be put 
 through the press and be deposited in the curing shed in the safest 
 and quickest manner. An overhead traveler costs little more than 
 ground tracks, and leaves more ground room for the placing of 
 the blocks. The curing shed should be large enough to hold a 
 week's product of blocks, and should have a sprinkling apparatus 
 throughout the length and breadth of it, so that all the blocks can 
 be kept wet at all times. It is advisable to have the sides of the 
 building closed in so as to keep the sun from shining on the blocks 
 and the wind from blowing the spray about too promiscuously. 
 
 In order to conduct a plant successfully, it should be fitted up 
 to make not only building blocks, but also window and door sills 
 and lintels, caps and copings, columns, balusters, rails, posts, and all 
 other building forms; also walk tiles and street curbing, etc. All 
 three of the processes of putting into mold can be economically 
 used; the pouring for complicated patterns, as capitals, columns, 
 balusters, etc.; the tamping process for all blocks where only a few 
 in number of a size are required, and the pressure system for the 
 majority of the work where a number of blocks of the same size 
 and pattern are needed. 
 
 The accompanying photographs (Figs. 1 to 6 incl.) are of a large 
 and successful Artificial Stone Plant. This is located near a thriv- 
 ing city at the junction of two railroads and on a navigable stream. 
 There is an inexhaustible bed of the finest building sand on the 
 property, and immediately adjacent to the buildings. The buildings 
 consist of a two-story frame building, about 20 ft. by 30 ft., with 
 pattern shop above and mixing and pressing room below; connected 
 to this building is a one-story building containing boiler, engine 
 and pump. Adjoining the press room is the curing shed, which is 
 an enclosed frame building, 150 ft. long by 45 ft. wide. The ma- 
 chinery consists of a 15-HP. boiler, 12-HP. engine, Fisher hydraulic 
 press, cubical mixer, Hexagon tile smoother and ventilating fans. 
 There are two lines of overhead tracks in the curing shed, and 
 
MANUFACTURE AND USB 67 
 
 ground tracks from the mixer through press and to the switch 
 tracks through the yard. There is an artesian well flowing at least 
 150 gals, per minute within 100 ft. of the curing shed, and pipes 
 
 Eno.News, 
 
 Fig. 1. General View of Concrete Block Plant. 
 
 throughout the building with sprinkling devices. This plant is 
 equipped for manufacturing in the most approved manner anything 
 that can be made out of concrete, with or without reinforcement, 
 and it is managed by men with a thorough knowledge of concrete 
 
 Fig. 2. Interior View of Press and Mixer Room. 
 
Fig. 6. Interior View of Curing Shed, Showing Overhead Trolley Tracks 
 
 and Molds. 
 
70 CONCRETE BLOCKS 
 
 and its uses, and who keep abreast with the advance knowledge on 
 the subject. 
 
 FORMS OP BLOCKS. 
 H. H. Rice. — To one contemplating the manufacture of concrete 
 blocks as a business there is nothing more important than an ex- 
 haustive consideration and investigation of the various shapes, sizes 
 and designs in which blocks have been constructed. Such investi- 
 gations should not stop with the forms now in actual use, but 
 should extend to all possible forms and their combination in finished 
 buildings. Let us begin with the crudest idea in block construc- 
 tion — a solid concrete block. We note that it has all the advan- 
 tages of natural stone, that it may be molded in any size or form 
 desired, that it is ready for its place in the wall without chisel 
 or hammer, and hence all expense of cutting and dressing is elimi- 
 nated, that each block fits in its intended place with a consequent 
 saving in time and annoyance in laying, that the blocks are made 
 on the ground where needed, thus making an enormous saving in 
 cost of transportation, that the walls tend to grow in strength for 
 many years while stone tends toward disintegration from the day 
 it is exposed to atmospheric influence, and, lastly, that it sustains 
 an enormous crushing strain. 
 
 The next step in block construction is taken in fulfillment of 
 a desire for a hollow wall, and is exemplified in the use of slabs 
 tied by metal strips and leaving an intervening air space, the effect 
 produced being equivalent to two walls with air space between. 
 Though crude in a way, it is scarcely necessary to elaborate on 
 the advantages of such construction. The building is warmer in 
 winter and the saving in consumption of fuel is estimated at 25%. 
 It is more comfortable in summer. It is sanitary and free from 
 vermin. While moisture may penetrate the outer shell, it cannot 
 pass the air space, and hence the interior is dry in all weather and 
 in all climes. Thus furring and lathing are unnecessary, and plaster 
 or other decoration is applied directly to the interior walls. The 
 patent disadvantages of such construction rest in the metal ties, 
 which are subject, on account of moisture penetrating the outer 
 shell, to rust and corrosion, and experience indicates that they 
 readily attract lightning. However, such a house may be seen in 
 the State of Kansas, now well preserved, though built over twenty 
 years ago by its present occupant; the Fine Arts Building of the 
 Lewis and Clark Exposition is of this style of construction. 
 
 To provide a wall having the advantages of the air space with- 
 out the disadvantages mentioned as appertaining to the metal ties, 
 and to secure throughout the wall a uniform, durable and fireproof 
 material, the hollow block was brought forth. Some 17 years has 
 this block now been in use in America, and it may be described 
 
MANUFACTURE AND USE 71 
 
 as having an outer and an inner face united by transverse sections 
 or webs, and containing intervening air spaces. When laid in the 
 wall these blocks break joints between alternate courses. The hol- 
 low spaces form continuous perpendicular flues. By far the greater 
 number of concrete block buildings in the United States are of this 
 type, and it is not difficult to find factories in operation under 
 some one of the many systems producing this style of block. But 
 man is ever alert for improvement, and experience showed a defect 
 in this construction in that moisture would follow the transverse 
 sections or webs through the wall, causing dampness on the interior 
 and necessitating furring and lathing. 
 
 With the view of obviating this fault blocks were devised in 
 which no transverse section passed directly from the outer face to 
 the inner one, and while retaining the external form of the blocks 
 alst mentioned the interior construction is such that the cross webs 
 are broken by perpendicular or longitudinal sections, the webs in 
 this type of block assuming a staggered, zigzag or S shape. This 
 considerably impedes the passage of moisture and makes it possible 
 to preserve a dry wall to a much greater degree than in the form 
 of block last described. 
 
 In the evolution of concrete block construction there next fol- 
 lows the development of various forms of angle blocks, being modi- 
 fications of the "T," "U," "E" or "L" shape, which will, by reason of - 
 certain characteristics common to all, be considered in this discussion 
 of structural form as a common type. Of these characteristics we 
 may especially note: (1) That no single block or portion thereof 
 extends through the wall; (2) that no single block possesses both 
 an outer and an inner face; (3) that the blocks in laying a single 
 course overlap breaking joints laterally so that in any given course 
 no joint passes through the wall, while the alternate courses break 
 joints perpendicularly, as in types already considered; (4) that 
 the arms or webs of alternate courses overlap from side to side 
 in such a manner as to form an alternating cross bond extending 
 from the inside of the outer face section to the outside of the 
 inner face section; that is to say, the bond extends almost through 
 the wall; (5) each block is held in place by eight other blocks to 
 each of which it is joined by cement mortar; (6) by leaving the 
 interior joints open a quarter of an inch a continuous horizontal 
 air space exists throughout the wall, and we have in effect two walls 
 tied by the overlapping of arms or webs in alternate courses; (7) 
 by a clever interlocking bond a wall may be produced of any desired 
 width, containing not one, but three, five, seven or more air spaces. 
 
 As the development of this type is comparatively new, a brief 
 discussion of these seven points may be profitable. The first pre- 
 cludes the passage of moisture by capillary attraction. The second 
 
72 
 
 CONCRETE BLOCKS 
 
 affords greater facility in facing. The third makes a frost-proof 
 wall. The fourth affords the greatest lateral strength of any known 
 masonry construction. The fifth makes a wall almost monolithic. 
 The sixth gives an insulated wall practically fireproof, a non-con- 
 ductor of heat, a wall dead as to sound and impervious to moisture. 
 The seventh affords a desirable wall for ice houses, refrigerating 
 plants and packing houses, as well as for bridge abutments, piers 
 and retaining walls. 
 
 Thus far we have discussed the various forms of blocks for 
 ordinary or main wall construction, but these alone would not build 
 a house. We must have numerous special blocks. As all systems 
 break joints perpendicularly, half blocks must be used in alter- 
 nate courses to finish at the end of a wall. Corner blocks must be 
 produced with a return of such length as will conform to the general 
 plan and preserve the bond in the wall. Openings for windows 
 and doors must be provided with jamb blocks of different designs 
 according to the character of casings to be used. The above indi- 
 cate only a few of the absolutely essential forms of blocks which 
 every system must provide before it can make any reasonable claim 
 to patronage. In addition I may mention lintels, sills, caps, coping, 
 belt courses, arch blocks, keystones as essential architectural mem- 
 bers fairly coming under our title. 
 
 Joseph Babiczky. — The size of blocks is limited by their weight. 
 A block weighing more than 100 lbs. cannot be handled with ease 
 and speed by one man; it is better not to exceed 75 or 80 lbs. 
 
 Geo. H. Crafts. — The one-piece block is simpler to lay in the 
 wall and has been the block principally used up to within the last 
 year or so. The two-piece is a lighter block to handle to make the 
 same size face stone, can be made of mere compact material and 
 gives a stronger bond in the wall. 
 
 SELECTION OF MATERIALS. 
 The standard ingredients for concrete blocks are Portland ce- 
 ment, natural sand and crushed stone or gravel. Hints on the 
 selection of these materials are found in the following quotations: 
 
 CEMENT. 
 
 H. H. Robertson. — Manufacturers should make some simple test 
 to determine what brands of cement give the best results as to 
 color when combined with the sand and aggregate it is expected to 
 use. Prefer cement to be shipped in paper bags, as no care has 
 to be expended in preserving bag, there is less loss by cement sift- 
 ing out, and paper is less easily penetrated by moisture than cloth. 
 
 H. H. Rice. — Having selected a certain brand of cement, stick 
 to it; different brands differ in color; furthermore, there is a dif- 
 ference in the way cement works; one's mixture may be ideal with 
 a certain brand, and give much trouble with another brand. 
 
MANUFACTURE AND USB 73 
 
 H. G. Richey. — Puzzulan cement should never be used for mak- 
 ing concrete blocks, as such blocks fail from cracking and shrink- 
 ing (at the surface only) in dry air; in damp places this cement 
 is equal to and in some cases better than the best Portland cement. 
 Color is one of the points to be considered in selecting a cement 
 for making concrete blocks, as the various brands dry out in different 
 colors, some being dark and some light in shade. It would be well 
 to keep samples of blocks made from the different cements to show 
 customers the various shades to be obtained. 
 
 Geo. H. Crafts. — Various substances having claims to strengthen 
 or accelerate the action of Portland cement are on the market, but 
 they should be used with great caution, as even if they do appear 
 to strengthen the material when first made they may have a deterior- 
 ating action. 
 
 SAND. 
 
 Since nearly all the writers specify clean and sharp sand, this 
 quality will be understood in the following quotations unless excep- 
 tion is recorded. 
 
 U. G. Hayne. — Test sand as to fire-resisting quality, when blocks 
 are liable to be subjected to fire. 
 
 Geo. H. Crafts. — A small proportion of clay makes blocks of a 
 damp mixture stand up better when made, and does not appear 
 to decrease their strength; but too much clay is undoubtedly in- 
 jurious. 
 
 Noyes F. Palmer. — Sand that will not absorb water should be 
 avoided. We had a ton of special sand sent to us; it was the kind 
 used in the manufacture of glass, and sold at $10 per ton. We had 
 difficulty in handling green product made with it, and when the 
 product was cured it looked like "shad roe" when examined with 
 a magnifying glass; the sand grains were all piled on top of each 
 other with voids between. To the naked eye the face looked white 
 and smooth, but the tenacity of the face was lacking. 
 
 G. W. Stevens. — Divide sand and gravel into two classes each, 
 viz., fine and coarse. Sand that will go through a sieve having 24 
 meshes to the inch, call fine sand; of the remainder that portion 
 which will pass a sieve of six meshes to the inch, call coarse sand; 
 of the remainder, that portion which passes a sieve having two 
 meshes to the inch, call fine gravel, and of the remainder, that 
 passing a 1-in. mesh sieve, call coarse gravel. This classification 
 is followed in the proportioning of the mixture. Both sand and 
 gravel should be entirely free from soft stone, or any other material 
 that will absorb water, because such particles when near the surface 
 are liable to freeze and burst out. 
 
 H. H. Rice. — Rolling sand between the fingers is an excellent 
 method of determining what is a proper material. In this manner 
 
74 CONCRETE BLOCKS 
 
 one can determine the relative strength of sand particles, detect the 
 presence or absence of clay, loam or other foreign substance, and 
 observe the presence of "grit." A gritty sand is essential, but loam 
 or clay in any considerable quantity becomes fatal, and necessitates 
 washing. Test the sand not only dry, but ascertain also what ef- 
 fect water will have on it. If wetting causes it to loose somewhat 
 of its "grit" and sharpness, and it shows a tendency to dissolve, or 
 reminds you of the action of sugar, discard it. 
 
 H. G. Richey. — Sand for the face should be fine, and that for 
 the body of the block should be coarse, or, better, should range from 
 fine to coarse. The sand for the face, if not perfectly clean, should 
 be washed; that for the body may contain about 5% of clay without 
 detriment to the strength of the block. There must be no clay in 
 the sand used for the face or exposed part of the block. 
 
 Joseph Babiczky. — Experiments show that sand containing up 
 to 10% of finely distributed loam makes just as strong and durable 
 concrete as does clean sand. It is to be noted that the loam must 
 be uniformly distributed, and not be in lumps; furthermore, sand 
 containing more than 2% of loam, even finely distributed, must 
 not be used in winter work as freezing destroys the cohesion. Sand 
 must be free from any kind of organic substance such as roots, 
 leaves and straw. 
 
 SUBSTITUTES FOR SAND. 
 
 Joseph Babiczky.— The following materials can be used in 
 place of sand in making concrete blocks: (1) Fine crushed stone, 
 which can be obtained at no extra expense if the rock is crushed to 
 maximum ^-in. size, when so much dust will result that the voids 
 in the clean crushed stone are completely filled. This is an ideal 
 material for concrete. (2) In the Southern states, where no sand 
 is obtainable, crushed oyster shells furnish a very good, clean and 
 sharp material, whose only objection is that blocks made from it do 
 not resist fire very well. 
 
 GRAVEL AND CRUSHED STONE. 
 
 H. G. Richey. — The aggregate may be either broken stone or 
 gravel, whichever is the more convenient and the cheaper; it should 
 be of a size to pass a 1-in. mesh sieve. Some manufacturers of con- 
 crete blocks are using sand and gravel combined, as it comes from 
 the pit or river bed; this is poor pplicy, for the sand and gravel 
 are not uniformly mixed nor in correct proportions; some blocks will 
 have too much sand, and some not enough. When the sand and 
 gravel are found together, they should be first separated by screen- 
 ing, and re-mixed in correct proportions; in this way only can a 
 uniform mixture be obtained. 
 
 Joseph Babiczky. — Crushed stone should consist of particles 
 varying in size from pieces passing a %-in. ring to fine dust. Lime- 
 stone in no form is permissible, because when the block is heated the 
 
MANUFACTURE AND USE 
 
 75 
 
 limestone is calcined to quicklime, and the blocks collapse, par- 
 ticularly if water is thrown on them. 
 
 H. H. Rice. — The choice as between gravel and broken stone 
 must often depend upon the local availability of the two; where 
 both are obtainable with equal facility there is some difference of 
 opinion as to which is preferable. Personally, I favor gravel, as 
 ordinarily possessing greater strength and firmness, although nu- 
 merous operators are using stone with marked success. Both mate- 
 rials should range in size from "pea" up to as large as can be 
 accommodated in the particular style of mold or machine in use. 
 Remember always that the object is to manufacture stone, and the 
 more of the large sizes contained in the aggregate the more do you 
 take advantage of the help which nature offers in the stone already 
 produced, and the more easy has your art become. Remember again, 
 that you can only make real stone by coating every particle of the 
 aggregate with cement; the smaller the particles of the aggregate 
 the greater is their resulting number, and the greater the amount 
 of cement required to secure the requisite crushing or tensile 
 strength. Hence with a given proportion of cement, the strength 
 is increased by increased size of the aggregate members. This 
 theory has been well substantiated by exhaustive laboratory tests 
 and by practical experience in general concrete work. 
 
 Noyes F. Palmer. — It is generally accepted that trap or granite 
 broken into pieces not larger than hen's eggs make the strongest 
 block; that the more stone dust used the fewer voids; that broken 
 stone that averages the size of chestnuts, with fine stone dust in- 
 cluded, is easy to handle and manipulate in block manufacture, and 
 makes a neat finish, while too large stone aggregates necessitate 
 slower work. 
 
 U. G. Hayne. — For block work no gravel that will not pass a 
 1%-in. screen, placed at an angle of about 30° with the horizon, 
 should be used. Great care should be taken to have the gravel 
 clean; even though it is worn quite smooth it is all right providing 
 it has the necessary tensile strength and toughness. Broken stone 
 of good texture that will break cubical in form, with the crusher 
 dust left in, will make good blocks. 
 
 SUBSTITUTES FOR GRAVEL AND STONE. 
 
 Several writers mention the possible substitution of crushed 
 slag, crushed brick, crushed tile and cinders for the usual gravel 
 or broken stone aggregate, but only one gives specific information. 
 
 Joseph Babiczky. — Old bricks of hard quality furnish a cheap 
 aggregate for concrete blocks when crushed. Cinders offer many 
 advantages as an aggregate for concrete, but must be used cautiously 
 as they often contain dangerous impurities and particles of un- 
 burned coal. They must be carefully washed, screened of ashes, 
 
7 b 
 
 CONCRETE BLOCKS 
 
 and the coarse particles crushed. Cinder concrete blocks must al- 
 ways have a sand mortar facing about L / 2 in. thick. It should be 
 noted also that cinder aggregate gives a block weighing about 40% 
 less than blocks of the usual cement, sand, stone mixture. 
 
 MIXING WATEE. 
 
 Few of the papers make any statement as to the quality of the 
 mixing water to be used in making concrete blocks. 
 
 H. H. Rice. — Use clean water. Don't spoil your blocks with 
 dirty, impure, muddy water. After performing the physical opera- 
 tion of block-making we feel that we have made stone, while we 
 haven't done anything of the sort; the chemical action of the water 
 upon the cement, causing crystallization of the silicates, is the real 
 process of stone-making. We want the most perfect chemical action 
 obtainable; therefore, use the best water obtainable. 
 
 PROPORTIONING OP MIXTURE. 
 The proper proportioning of the various ingredients is a ques- 
 tion upon which the several writers exhibit great divergence of 
 opinion. 
 
 Joseph Babiczky. — My experience is that 1 part cement and 5 
 parts sand properly mixed, tamped, handled and cured gives blocks 
 as good as any common building stone. If suitable crushed stone 
 can be obtained, a combination of 1 part cement, §y 2 parts sand 
 and 6 parts stone makes a good mixture supposing that the sand 
 is not too coarse and the stone varies in size from y 2 in. to dust. 
 
 G. W. Stevens. — For the wet process the following proportions 
 can be used: 1 part cement, 1 part fine sand, 2 parts coarse sand, 
 2 parts fine gravel and 2 parts coarse gravel. For the dry process 
 the following mixtures are suitable: (1) For facing, 1 part fine 
 sand, 1 part coarse sand and 1 part cement; for backing, 1 part 
 fine sand, 2 parts coarse sand, 3 parts fine gravel and 1 part cement. 
 (2) For one mixture throughout, y 2 part fine sand, 3y 2 parts coarse 
 sand and 1 part cement. (3) Same face mixture as above; for 
 backing, y 2 part fine sand, iy 2 parts coarse sand, 2 parts fine gravel 
 and 1 part cement. (4) 1 part fine sand, 2 parts coarse sand, 3 
 parts coarse gravel and 1 part cement. 
 
 Noyes F. Palmer. — In regard to cement and its aggregates, it 
 matters not if it be a mortar block of 1 cement and 4 sand, or a 
 concrete block of 1-2-4 or 1-3-5 composition. The practical thing is 
 to find out how to fill the voids in all cases so as to get the greatest 
 strength in the cured block. 
 
 U. G. Hayne. — In most cases a mixture of 1 part cement to 4 
 parts sand should be used for blocks. This proportion can be used 
 where blocks are to be put to the severest test as to fire, compression, 
 tension, etc. I would recommend a facing of about % in. in thick- 
 ness of 1 part cement and 2 parts sand mixed a trifle drier than 
 
MANUFACTURE AND USE 77 
 
 the body of the block. This will permit the face mold to part freely 
 from the mortar leaving a clean cut face. 
 
 H. H. Frantz. — Use mixture of 1 cement, 2 x /o sand and 3^ 
 broken stone proportioned by measure. 
 
 G. W. Robertson. — To determine practically the amount of ce- 
 ment needed for making a good block have found a simple and satis- 
 factory way to be to get two graduates such as druggists or pho- 
 tographers use, one of say 24 oz. and the other of 8 oz.; fill the 
 larger with the coarse aggregate and then from the smaller pour in 
 water until it stands on top of the material; note amount of water 
 used; empty large graduate and fill with same material, to which 
 add the amount of fine material (sand or stone dust) indicated by 
 the amount of water noted; mix the fine and coarse material thor- 
 oughly, then add water from smaller graduate as before; the amount 
 of water used will give amount of cement needed to make good 
 blocks. 
 
 CONSISTENCY OF MIXTURE. 
 In respect to consistency, practice classifies concrete mixtures 
 for block manufacture into wet mixtures and dry mixtures. Con- 
 crete block machines are designed specifically to use one or the 
 other of these mixtures. 
 
 H. G. Richey. — It is the opinion of the writer that the use of 
 such a number of molds as will permit the mixture to be left in 
 the mold about 12 hours will result in the production of the bet- 
 ter blocks. The concrete can then be mixed with enough water 
 to permit solid tamping and to provide for the proper crystalliza- 
 tion of the cement; this will make a much harder and more dense 
 block than many of the dry mixtures now in use. In making a 
 block where the mold has to be removed immediately the con- 
 crete must be dry enough to stand up when the mold is taken 
 away, and the block must stand from 6 to 8 hours before it is 
 safe to wet or sprinkle it without fear of destroying the face or 
 arrises. Concrete made as dry as this and then exposed to the air 
 while the setting of the cement is taking place has not sufficient 
 water to cause complete and correct crystallization. The writer does 
 not advocate a mixture so wet that it can be poured into the molds, 
 but the mortar portion of the concrete should be of about the same 
 consistency as mortar used for laying brick or stone. 
 
 Geo. H. Crafts. — About 10% by weight of water is the proper 
 proportion to use for the mortar for tamping and pressure processes, 
 but about double this amount is necessary for the pouring process. 
 
 U. G. Hayne. — While the reason in favor of employing the make 
 of machine that uses wet flowing concrete and permits it to set in 
 the mold is a good one, it is more than balanced by the large num- 
 ber of molds required for work. Where reinforcing prevents thor- 
 
78 CONCRETE BLOCKS 
 
 ough tamping, or where the surplus water can be quickly drawn off, 
 are the only cases in which I would sanction an excess of water 
 in this class of construction. When well tamped in the mold there 
 should be just enough water in the concrete to show on the iron 
 tamper. 
 
 H. H. Frantz. — The mixture must be made sufficiently liquid 
 that the mere shaking of the mold will settle the mass; a stone thus 
 made will be found far better and much more impervious to water 
 than one made by the dry process. 
 
 Joseph Babiczky. — For tamping and pressing the materials must 
 be mixed with only so much water that the mixture is of the con- 
 sistency of damp garden earth. For the pouring process the mix- 
 ture must be so wet that it runs easily out of the buckets. 
 
 G. W. Stevens. — I am in favor of wet concrete. The concrete 
 should be made wet enough to flow freely under the cores and into 
 the corners. 
 
 Noyes F. Palmer. — The less water used in the process of mold- 
 ing mortar or cement blocks the less voids and a resultant greater 
 strength. 
 
 METHODS OF MIXING. 
 Two methods of mixing the ingredients, first machine mixing 
 and second hand mixing, are available in concrete block manufacture 
 as in general concrete work. 
 
 G. W. Stevens. — A wooden floor should not be used; a cement 
 or earth floor with a coating of fine sand spread over it is a desirable 
 one. In summer, especially, have the mixing floor so that the sun 
 does not shine on it, and where there is no draft of air. 
 
 Joseph Babiczky. — The ingredients must first be thoroughly 
 mixed dry and then wet; if mechanical mixing is employed the 
 mixer should provide for separate dry and wet mixing; it should 
 also provide for the addition of the water in a fine spray. 
 
 H. H. Frantz. — Provide yourself with a mixing box on wheels; 
 box should be say 6 ins. deep, 5 ft. wide and 5 ft. long. Place in the 
 box 2y 2 parts by measure of sand well scattered, spread over this 
 1 part of cement and mix thoroughly with hoe, shovel or rake. 
 Next add clean water and beat up to consistency of soft mushy 
 mortar. Finally add Sy 2 parts of gravel and mix and "beat to a 
 soft mixture. 
 
 H. G. Richey. — When the plant is large enough to justify the 
 expense a power mixer will be the most economical as well as the 
 most convenient. For a block plant a batch mirror will prove the 
 best, for by it the concrete can be mixed as thoroughly as desired. 
 In any machine mixing the cement, sand and aggregate should first 
 be mixed thoroughly while dry, then the water should be added 
 in just sufficient quantity to make a soft plastic mixture, which 
 
MANUFACTURE AND USE 
 
 75 
 
 will tamp readily in the molds, and after being tamped lightly will 
 quiver at each stroke of the tamper. When the mixing is done 
 by hand with shovels or hoes, the cement and sand should be mixed 
 dry, then with water to make a mortar of the consistency described. 
 Finally the aggregate previously wetted should be added and thor- 
 oughly and evenly incorporated with the mortar. 
 
 Geo. H. Crafts. — Undoubtedly machine mixing is much better 
 than mixing by hand as it is much more thorough. A batch mixer 
 mixes thoroughly all the ingredients of a batch, and can be kept 
 running continuously if the material is not wanted just at the time 
 it was mixed, whereas a continuous mixer has to be stopped, since 
 it will not continue to mix the same material. It is better to mix 
 the materials in a dry state at first and then gradually add the 
 water in a spray and continue the mixing. The longer the mixing 
 is kept up the better, as experiments show that the strength of 
 concrete is increased by mixing even up to two hours after being 
 wetted. 
 
 U. G. Hayne. — Hand mixed concrete should be mixed on a tight 
 platform, or in a large mortar box, with square, pointed shovels or 
 mortar hoes. Measure and spread the sand evenly over one side 
 of the platform, or in one end of the mortar box, care being taken to 
 have it spread evenly and 8 ins. to 1 ft. in thickness. On top of 
 this spread the required quantity of cement, taking care to, have the 
 cement well distributed on the edges of the layer of sand. On each 
 side of the platform place a man with a square pointed shovel pre- 
 pared to shovel the concrete to the vacant side of the platform. 
 The shovel should be run along the edge of the pile, filling from 
 what rolls down and when full should be turned to a separate pile 
 with a spreading motion, care being taken to have all the pile thor- 
 oughly turned as there is a tendency to first to slight the portion 
 where the two shovels meet. The object of the shovelers should 
 be to have gravity aid in the mixing as much as possible by handling 
 the concrete so that it rolls down on the pile, being shoveled from as 
 well as cn the one shoveled to. 
 
 Two or three good turnings should give the concrete an even 
 color, if not, it should be turned until it is of one. Then the con- 
 crete should be evenly spread out and the water added, preferably 
 with a sprinkler, though I have seen no evil effects from taking 
 the quantity of water required and gently pouring it on top of the 
 pile, and after letting it stand for two or three minutes mixing 
 in the same manner with the shovels as before, adding the water. 
 The turning should be continued until the water is thoroughly in- 
 corporated in the concrete, and, when finished ready for the molds, 
 a quantity of the concrete tightly squeezed in the palm of the hand 
 and the hand opened palm up, should remain like a ball on the hand. 
 
80 CONCRETE BLOCKS 
 
 Using the mortar box and the hoes, the sand and cement should 
 be spread in one end of the box evenly, the same as described for 
 the platform. The man mixing then stations himself at the oppo- 
 site end, and hoes the concrete toward him with a quick downward 
 stroke, pulling quickly toward him at the same time the stroke ends, 
 and taking a cut of about an inch into the concrete each time. This 
 quickly and thoroughly mixes the concrete. Turn the whole quan- 
 tity back the same way to the end it was first in, or two turnings, 
 add the water and turn until the mixture is all of the same wetness. 
 
 There is no question but that machine mixed concrete, where 
 the machine is correctly used, is better and more thoroughly and 
 cheaply mixed, than by hand, and as soon as the business will 
 justify it one should be used. Would not attempt to use a hand- 
 power mixer but a gravity or power one. The danger to be avoided 
 above all, though is to not mix too much concrete at once, as the 
 temptation is too great to use it, if mixed, even though the initial 
 set has begun. With some cements, concrete used within l 1 /^ hours 
 is all right, but with most 20 to 30 minutes is about the limit. 
 
 BLOCK MACHINES AND MOLDING. 
 
 Concrete block machines are designed to use either a wet, a 
 machine or a dry mixture, and the construction of the machine and 
 the process of molding vary for each mixture. 
 
 H. H. Rice. — The most simple form of mold ever devised for 
 making a hollow concrete block consists of two side boards with 
 cleats to engage end boards, clamps to keep the sides in position, 
 two or three pieces of stove pipe to form the hollow spaces, with 
 a piece of 2 x 4-in. timber for a tamper, the latter shaved at one 
 end to fit the hand. If you have some knowledge of cement and 
 a little mechanical skill, it is possible for you to make very good 
 blocks with this outfit. If you do not understand the action of 
 cement, and have no mechanical skill, it is possible for you to make 
 very poor blocks with the latest improved appliances. And I may 
 here say that the genius of the inventor and the mechanic is ex- 
 emplified in varying degrees from the mold I have described to the 
 most modern machinery in block manufacture, while the energy, 
 perseverance and ability of the operator are displayed in varying 
 degrees from blocks whose quality has irreparably injured the stand- 
 ing and reputation of artificial stone to beautiful, lasting and sym- 
 metrical edifices, which are things of beauty and a joy forever. 
 Don't forget that the best machine requires mechanical commonsense 
 to obtain the best results. 
 
 I have said that all processes are roughly classified as tamped, 
 poured or pressed, and again, in the same order, as dry, wet or 
 medium. I shall first consider the machines for making blocks by 
 the comparatively dry hand tamped process. These machines con- 
 
MANUFACTURE AND USB 81 
 
 sist, in general, of a stand to bring the bed to convenient working 
 height surmounted by a mold containing interior cores. The mold 
 is filled with a moist mixture of sand and cement, tamped well as 
 the mold is filling and slightly heaped up at the last to permit 
 leveling off with a straight edge. Now there are very many differ- 
 ent machines of this type in market to-day, and their chief differ- 
 ences may be summarized as follows: Some drop the interior cores 
 mechanically from the block, then unclamp and drop the sides, 
 thus leaving the block free on the bottom plate ready to be car- 
 ried to the curing yard. In others, the cores and the frame sur- 
 rounding the mold are stationary while the bed moves upward to 
 release the block and the same upward motion disengages the sides 
 from the surrounding frame, allowing them to fall away from the 
 block; when the bed is lowered the cores come into proper position 
 and the outer frame engages the hinged sides and ends so that one 
 downward motion throws the entire mold into position for re- 
 filling. In others the sides are hinged on a corner, the bed station- 
 ary and the cores movable, so that in releasing one side and one 
 end are laterally withdrawn from the block and the cores dropped 
 out of the block, as in the kind first described. Still others have 
 longitudinal cores which are withdrawn by hand. Certain of these 
 machines have a device for throwing the mold at 45° angle to per- 
 mit of applying face matter as already mentioned. Another type 
 of machine, though following the same general lines of construc- 
 tion, has the mold turned on the side to more easily face the blocks, 
 and the latter type withdraws the interior cores laterally. The 
 above fairly covers that general type of machines in which blocks 
 with interior cores are manufactured by tamping. You will note 
 that but slight structural differences obtain, the diversity being more 
 in the line of labor-saving devices. All contemplate the use of hand 
 or automatic tampers, and hence neither wet nor medium mixture 
 may be used. If this is attempted, the mass will squash under the 
 blows of the tamper, while if comparatively dry it will pack to an 
 extent sufficient to enable the block retain its shape while being 
 carried (on the bottom plate) to the curing yard. Subsequent sprink- 
 ling is relied upon to secure additional cyrstallization. The best 
 practice does not admit of placing such blocks in the wall under 
 twenty days. While some manufacturers claim that coarse mate- 
 rial, either gravel or broken stone, may be advantageously used 
 under this process it has never been my good fortune to see this 
 practice followed in commercial manufacture, and I believe sand 
 and cement to be best adapted for use in the machines already 
 mentioned. 
 
 Next in order we have the wet or poured process, which is 
 characterized by sheet iron molds in which a fluid mixture is poured. 
 
82 CONCRETE BLOCKS 
 
 Either fine or coarse aggregates may be used with equal facility. 
 The paramount ideas of this process are that a copious admixture 
 of water causes the cement in fluid state to thoroughly permeate the 
 aggregate and completely coat every particle thereof, and that such 
 immediate and plentiful application of water secures a thorough 
 crystallization in the initial set. There can be no question about 
 a block so produced being both strong and durable, though there 
 is some doubt as to the uniformity of that strength on account 
 of the gravitation of heavier particles to the bottom of the mold. 
 By the use of porous molds one manufacturer aims to avoid the 
 porosity in the block due to an excessive amount of water creating 
 voids by subsequent evaporation. The chief objection, however, to 
 this process appears to lie in the fact that the block must remain 
 several hours in the mold before attaining sufficient firmness to 
 retain its form. Hence, an unreasonably large number of molds is 
 required to produce a reasonably large output. 
 
 We have yet to consider the medium or pressed process, in 
 which from seven to eight per cent, of water is used, and a con- 
 siderable proportion of gravel or broken stone. As this process is 
 comparatively new the systems based on its principles are less 
 numerous than those under the processes previously considered, but 
 I have found a considerable number of factories turning out a 
 satisfactory product. As the pressure is simultaneously applied to 
 every portion of the block, the difficulty mentioned in using a wet 
 or medium mixture under tamping is obviated. On the one hand, 
 this process eliminates the time consumed in tamping under the 
 dry process; on the other hand, it eliminates the time consumed 
 in setting in the molds under the poured process. It may fairly 
 be said to partake of the nature of both, inasmuch as the amount 
 of water in the mixture is sufficient to flush to the surface under 
 pressure, and the blocks are afterward kept thoroughly saturated 
 with water for a week before going into the wall — thus securing 
 both the initial set and subsequent crystallization. The application 
 of pressure necessarily eliminates the use of interior cores, and 
 hence blocks are made in the "T," "E," "U," or "L" shapes mentioned 
 in a previous paragraph, the molds providing for adjustment to all 
 widths of wall by shortening or lengthening the arms of the blocks. 
 The best results under this process appear to be obtained by press- 
 ing the block with the face up, for two reasons: First, the pres- 
 sure applied in this way insures a hard, dense and comparatively 
 impervious face; second, it affords an opportunity to first shovel 
 the coarse concrete into the mold, and lastly (before pressure) to 
 apply the rich face matter, which, under a heavy pressure, becomes 
 well bonded with the body of the block. 
 
 Geo. H. Crafts. — There are three general systems of filling and 
 
MANUFACTURE AND USE 83 
 
 compacting the mixture into the forms desired; the pouring, tamp- 
 ing and pressure systems. In the pouring system, the concrete 
 material in a wet condition is poured into the box or mold, great 
 care being taken that the mold is completely filled in all parts, and 
 particularly in the angles and corners, and that no air holes are in 
 the material. The one-piece block is the block generally used in 
 the pouring system of work. In the tamping system, which is the 
 one most in use at the present time, the material in a damp con- 
 dition is thoroughly tamped by hand tampers as it is put into the 
 box, and especial care has to be taken that the edges and the cor- 
 ners are thoroughly rammed. The one piece block in multitudinous 
 forms is the one generally used in this system. In the pressure 
 system the material, which is in a damp condition, is pressed by 
 hydraulic pressure, or pressure secured by toggle joints or other 
 mechanism, into the box. Hydraulic pressure gives the heaviest or 
 most exact pressure as the amount of pressure is shown exactly 
 by a gage attached to the machine, and is the same regardless of 
 the amount of material in the box. With the toggle joint machines, 
 the pressure is more or less indeterminate, depending on the amount 
 of material put into the box. The two-piece block is the one gen- 
 erally used in the pressure system, although the one-piece block can 
 be made. 
 
 G. W. Robertson. — Too much care can hardly be given to the 
 selection of a block machine, as upon the machine largely depends 
 failure or success in block making. Aside from the fact that a 
 majority of those engaging in the manufacture of blocks do not 
 have the necessary capital to purchase and outfit a plant with hy- 
 draulic machinery, I do not believe the results obtained from the 
 use of such an outfit justify the outlay either as to amount or 
 quality of blocks made. Taking into consideration the fact that 
 the pressure applied is for but a fraction of a minute, and that to 
 a material in what might be called practically an air tight box 
 or mold, and I believe the result will be found to be a block with 
 two surfaces more or less compact, while the main body of the 
 block is filled with air channels, where the air has been suddenly 
 expelled or compressed, giving a block that will readily absorb 
 moisture. Select a machine that will give varieties of the most 
 salable size blocks. Get a machine with as few cogs, gears, springs 
 and levers as possible, for you will find all such not only limit the 
 life of the machine, but are liable at any time to get out of order 
 from clogging with concrete. Do not get a machine standing too 
 high, as then you will either have to build a platform for work- 
 men to stand on or they will be working at a most decided disad- 
 vantage. Prefer also a machine using removable cores, as not only 
 are they less liable to catch or stick when coarse material is used 
 
84 
 
 CONCRETE BLOCKS 
 
 for backing, but are also more quickly handled than machines with 
 fixed cores. Prefer again a machine in which blocks are made face 
 down and after being made are revolved, say, one-fourth to rest 
 on pallet when machine is opened. Face, side and end plates should 
 be accurately machined so they may fit properly, and not used just 
 as they come from the mold, else you will always have trouble in 
 getting your plates to fit, and also in having your blocks correct 
 in size and shape. As to pallets for use with machines prefer 
 wooden to iron, because of lower first cost and cost of mainte- 
 nance. With common care wooden pallets will last nearly as long 
 as iron, and their first cost should not be over one-sixth that of 
 iron pullets. 
 
 Noyes F. Palmer. — Concrete blocks cannot be too good, and 
 hence the heavier the machine and the more automatic its action 
 and positive its movement, the cheaper the product. A machine 
 must have adjustability to permit the manufacture of varied shapes. 
 It must be the most favorable in functions to permit open top tamp- 
 ing and, like the flask and drag in the foundry, easily got at and 
 handily manipulated. 
 
 G. W. Stevens. — A good way to judge a block machine is to 
 find out how long it takes to set up and take apart the machine 
 in actual work. Some of the points to be considered are these: 
 Is it complicated and likely to get out of repair quickly? Are the 
 castings light and easily broken? In the wet process the concrete 
 should be wet enough to flow freely under the core and into the 
 corners. By raising the end of the mold and letting it drop sud- 
 denly the concrete will be sufficiently settled. In the dry process 
 fill in 2 or 3 ins. of concrete, give the first blows to the corners 
 and the edges, and, finally, tamp the body. As soon as hard stop 
 tamping. If tamped too much the layer will be smooth and be 
 liable to cause a seam; the surface should be left a little rough 
 so that the next filling will adhere to it. The last filling should 
 bring the material above the mold so that it can be tamped solid 
 and struck off with a straight edge. 
 
 H. H. Frantz. — The first things needful are "molds" or "forms," 
 of which hundreds of patented articles are now on the market, but 
 fortunately these need not be expensive, nor patented, nor is ma- 
 chinery at all necessary or essential; what is needed is a simple 
 steel mold or form. This will consist of only four pieces of steel 
 plate, say %-in. thick, two sides and two ends, with the edges stiff- 
 ened by riveting thereto steel angles, and arranging the angle joints 
 so that these can easily be connected, and disconnected and firmly 
 clamped; the inner surface should be perfectly smoothed. The size 
 will of course depend on the size of block that may be desired; a 
 block 10 ins. thick x 10 ins. high x 27 ins. long would be fair. Of 
 
MANUFACTURE AND USE 85 
 these molds a number must be provided, and with each there must 
 be a smooth wood bed plate, say 12 x 30 ins. long, having a true 
 smooth surface. The next requisite is a "core" (that is, a form of 
 wood or metal) to be laid inside the mold, to form the hollow 
 space in the block. It may be of any desired form. The block 
 may have one or more hollows, extending through the block, from 
 side to side, but their size should be such as will leave the walls 
 or shell of the finished block of sufficient strength, from iy 2 ins. 
 to 2% ins. thick, and their shape must be such that, after the 
 cement block has been formed, it can easily be withdrawn, with- 
 out disturbing the material of the block, usually in two parts, half 
 to draw out from either side. 
 
 U. G. Hayne. — I can see no special object in making a concrete 
 brick the same size as an ordinary clay building brick, except that 
 of force of habit. I will not, therefore, consider that form of block 
 more than to say that it can be made and laid the same as ordi- 
 nary brick, but there is no saving in cost of laying in the wall 
 over that of laying brick, which is quite an item in using con- 
 crete blocks. It may be that in some localities the call for blocks 
 the size of brick will be such that a machine for making them will 
 be a valuable addition to the plant. Then there is the choice be- 
 tween the machine in which the concrete is permitted to set in the 
 mold, having the concrete wet enongh to pour, and the one that uses 
 the concrete of such wetness that the molds can be stripped from 
 the block immediately, and the process of filling repeated. 
 
 While the point in favor of employing the make of machine 
 that uses wet flowing concrete and permits it to set in the mold 
 is a good one, it is more than balanced by being compelled to have 
 so many molds to do the work with. Just as good results can be 
 obtained with the machine using material of such wetness that it 
 will stand to have the molds removed immediately. 
 
 Where reinforcing prevents the use of good tamping, or where 
 the surplus water can be quickly drawn off, are the only cases in 
 which I would sanction an excess of water in this class of con- 
 struction. The simplest made machine with the least gearing and 
 parts to get out of order will give the best satisfaction. On account 
 of the danger of jarring the block, while handling it, after taking 
 it from the machine to the place where it is to be cured, I would 
 favor the machine that is taken from the block, after the block is 
 in place for curing. The strength of the concrete can be much 
 weakened and the block still hold its form, or the stone may be 
 checked and the harm not noticed at any time, and thus result in 
 making a poor block. 
 
 Machine or power tamping in a large plant should be all right, 
 though, as I understand the situation, the power tamping machines 
 
86 CONCRETE BLOCKS 
 
 are not all the success that they should be. A pneumatic tamper 
 handled by hand in a similar manner as the pneumatic riveter is 
 said to be giving good satisfaction. On account of the expansive 
 quality of air, the pressure made block is somewhat weakened by 
 the expansion of the air in the stone when the mold is taken from 
 it. I know of no machine of the pressure type that is a good block 
 maker and believe this to be the reason. 
 
 This brings the question of the machine down to the one that 
 can be easily carried, and to hand, or pneumatic, tamping. Add to 
 this the ones that the makers are willing to furnish a copy of any 
 patents they may have, and the makers' ability to prove that they 
 will protect the purchaser in his rights, and the machine deal is 
 ready to close. A machine with a patent on it is not of as much 
 consequence as the features of the block and air spaces that are 
 patented. In a wet country the double, staggered air spaces are 
 more apt to make a warm, dry wall. 
 
 As to the speed of operation of a machine, there are few if 
 any machines but that will make as many blocks as material can 
 be tamped into them and taken out. Expressed in other words: 
 they are limited only by the skill, dexterity and handiness of the 
 crew handling them, and a gang of three men should be able to 
 make from one hundred and twenty-five to one hundred and fifty 
 blocks, of an average size of 8 ins. high by 9 ins. wide, by 2 ft. 
 long, in a day of ten hours. 
 
 A machine guaranteed by a good, reliable company should be 
 considered above one not so warranted, other things being equal. 
 Though the cost of compelling the making good of the guarantee 
 makes it of uncertain value. The only feature of exclusive rights 
 that has any real merit is the one where the patent applies to 
 some good feature of the structure of the block and not to the ma- 
 chine. There are so many machines of practically the same price 
 and capacity that the exclusive right to use a certain machine with- 
 out a block patent would be of little if any value. 
 
 H. G. Richey. — After deciding on the location of the plant, then 
 will come the selection of machines or molds. This is a matter that 
 must be left to the party who is to operate the plant; for different 
 people prefer different machines or molds. He should visit the dif- 
 ferent plants in operation and see the various machines at work, 
 and then after making all the inquiry he can about them select the 
 one that most favorably impresses him. 
 
 There are quite a number of machines on the market at the 
 present time, and all are turning out about the same quality of block. 
 So far as quality is concerned, it is not so much the machine or 
 molds as the materials used, the proportions in which they are 
 mixed, and the manner of using them, that determines the quality 
 
MANUFACTURE AND USE 87 
 
 of the block. A person in selecting a machine should select one 
 which is not too complicated, and which is as simple as possible 
 in its operation. 
 
 Some manufacturers of machines, in addition to selling their 
 machine or molds, are selling exclusive territory for the use of the 
 machine. The writer considers money paid for the right to use 
 any particular machine in a certain territory is money thrown 
 away, for there are so many different makes of machines on the 
 market that the buying territory for the use of any particular ma- 
 chine will not give the purchaser the exclusive right to manufacture 
 concrete building blocks in that territory. Some other party with 
 a different make of machine will step in, and turn blocks equal to 
 the ones made by the person who paid his money for exclusive 
 territory. Thus the writer would be adverse to paying money for 
 territory, but would take the money thus saved and purchase addi- 
 tional molds for making a larger variety of blocks. 
 
 The location and amount of business contemplated will also 
 have to be considered when purchasing a machine. If it is not ex- 
 pected to do a large business a set of ordinary molds may be suf- 
 ficient, but in another locality where there will be a large demand 
 for the blocks a larger number of molds or machines will be required. 
 
 CURING MOLDED BLOCKS. 
 
 Geo. H. Crafts. — After molding the next process in the proper 
 making of blocks is the curing. This process is one of the most 
 important in the manufacture of first-class blocks, although, as a 
 usual thing, no attention at all is paid to it. Most block makers 
 consider that the block is made as soon as it comes out of the 
 mold, and they put it out in the sun or in any old place where it 
 is handiest and pay no attention whatever to the curing of it. 
 Any concrete material to attain its greatest strength and have the 
 best appearance must be properly used, and this curing consists 
 in keeping the material in the shade and in a wet condition for 
 a number of days after it is made. If concrete dries out imme- 
 diately after making, the action of the cement is deadened and 
 the concrete is crumbly and weaker than if kept wet until the 
 cement has had full time to harden. All good authorities recog- 
 nize this fact and proper means for the curing of all blocks should 
 be a part of every building block plant. The blocks should be kept 
 in the shade and thoroughly wetted for a week or ten days in order 
 to receive the proper curing. 
 
 U. G. Hayne. — After the block is safely set it should be gently 
 sprayed with water, care being taken not to have the spray of 
 such force as to disintegrate the face of the block or mar the cor- 
 ners. After ten or twelve hours there is little danger of the block 
 receiving too much water. The intelligent care used in curing 
 
88 CONCRETE BLOCKS 
 
 molded concrete work has almost as much to do with attaining 
 its ultimate strength as the quantity of cement used. The early 
 drying of the block will have a tendency to dry out the corners 
 before the initial set is fully completed, leaving them with little 
 strength and likely to crumble at a touch. Plenty of water for 
 about ten days is what the work needs after the first sprinkling 
 is given. 
 
 Joseph Babiczky. — Curing of the blocks is one of the most im- 
 portant processes of their manufacture, and must be watched very 
 carefully. In summer the heat and in winter the frost is very in- 
 jurious. In summer after the blocks have set so far that sprink- 
 ling does not hurt them they must be sprinkled over and over again. 
 A boy with a watering pot which is equipped with a rose spray 
 and which sprays the water in a uniform stream is one of the 
 best devices for small and medium size plants. If there is city 
 water under pressure it serves well, but I would suggest in the 
 first 48 hours the exclusive use of the watering pot, as the pressure 
 of the city water can easily injure blocks in the early stages of 
 hardening. Apply water in abundance. 
 
 H. G. Richey. — Concrete blocks should always be cured by wet- 
 ting or sprinkling them with water. Blocks which have sharp cor- 
 ners or arrises or any sharp projections should be given special 
 care to keep these projections moist and prevent their drying too 
 rapidly. A number of block manufacturers have failed to produce 
 ornamental blocks with sharp and distinct lines, the principal 
 reasons being that the mixture used was so poor and the projec- 
 tions or ornamentations of the blocks were allowed to dry too rap- 
 idly. Blocks as soon as taken from the molds should be placed 
 in the curing room or shed, which should be built so as to exclude 
 all sunshinne or draughts of air. As soon as hard enough, which 
 will be in about ten hours, the blocks should be sprinkled lightly 
 with water and covered with a wet cloth or burlap; they should 
 then be wet four times daily for about seven days, and should not 
 be removed for use until they have attained an age of about 15 days. 
 
 FACING AND COLORING. 
 H. H. Rice. — I now challenge your attention to that much 
 mooted question of body and facing, as well as various forms of 
 face and colored blocks. Eliminating face matter from your pro- 
 cess of manufacture, you are compelled to make your entire block 
 of such material as will produce the face you desire. That is to 
 say, if you wish a rich face your entire block must be unnecessarily 
 rich in cement. If you wish a fine face your entire aggregate must 
 be of fine sand, and result either in a loss of strength or in the use 
 of an inordinate proportion of cement. A standard argument 
 against facing is that it does not increase strength; certainly not. 
 
MANUFACTURE AND USE 
 
 89 
 
 Though face matter contains a much greater percentage of cement 
 than does the body of the block, yet the aggregate of the face is 
 very fine sand and hence possesses no greater strength than that 
 obtaining in the body of the block through the use of a smaller 
 percentage of cement with coarser material in the aggregate. Now, 
 do you wish to use a similar composition throughout the block, 
 with consequent loss of strength unless the amount of cement be 
 abnormally increased? Certainly not. What then? Do you de- 
 sire the face of your block to be of coarse material? Certainly 
 not in a quality of blocks to compete with pressed brick and cut 
 stone. The opposition to facing has largely arisen from the old 
 style of mold in which faces are formed by the upright sides, and 
 in which there is no device for facing otherwise than by the use 
 of a partition. A popular demand always brings forth some remedy 
 for any existing evil, and this fault is now overcome in various 
 ways in various machines. Some now make the face on the bottom 
 of the mold, some tilt the mold at an angle in order to put in 
 the face matter first, some make the two-piece blocks with face up, 
 putting the face matter in last and then applying pressure from the 
 top. Of these various machines more in their order, but the fact 
 I wish here to establish is that the various devices now in use 
 for facing prove beyond a doubt that what the people want, and 
 what they will have, is a strong and durable concrete block with 
 a beautiful face. And here I would also firmly impress this truth, 
 that the face and the body of the block must be made at one simul- 
 taneous operation and the face matter must be so imbedded into 
 the coarse concrete that it becomes an integral part of the block, 
 and there must be no distinct line of cleavage between the face 
 and the body. I wish you would memorize that; it is perhaps the 
 most important sentence in this paper, and the number is legion 
 who have dearly paid to learn this truth. 
 
 Now, as to various forms of face, the smooth even face is always 
 elegant, but if without contrasting ornamentation it becomes mon- 
 otonous. The pitch face, commonly called "rock face" by all block 
 makers, is to-day the most popular design, principally from force 
 of habit. I cannot believe that it will ultimately endure, as it nearly 
 always appears to be what it is — an imitation. When the manu- 
 facture of concrete blocks was in its infancy, a man whose name 
 is known to very many readers of this article as an eminent author- 
 ity on cement matters, remarked to me, "What you want is a 
 face that will survive, and that face will be chiseled, or ribbed 
 with a bevel edge, because it has a genuine look." He was right. 
 That is the face that is daily growing in favor. The popular de- 
 mand of the day is for genuineness. That is destined to be the 
 face of the future. That is the face which will get business, which 
 
90 
 
 CONCRETE BLOCKS 
 
 will keep business, and which will increase business. Then there 
 are various ornamental faces; nearly every plate manufacturer pro- 
 duces a greater or less variety. Into the merits of these I shall not 
 go. Prepare yourself with a reasonable variety, in order to meet 
 the demand, but don't get into the "gingerbread" habit — it lacks 
 elegance. And don't, without advising to the contrary, allow a cus- 
 tomer to select a design of which he will tire in a month. 
 
 Now, as to colored facing, it is simple. Almost any color may 
 be produced by mixing dry mineral coloring matter with the face 
 matter. Vegetable colors should never be mixed with cement. 
 Reputable manufacturers now produce colors from iron pigments, 
 especially adapted for this purpose, furnish them at reasonable prices, 
 and supply complete instruction as to mixture and methods. A 
 quarter or three-eighths inch face properly colored and properly 
 applied will produce a beautiful stone practically unchangeable and 
 everlasting. 
 
 G. W. Stevens. — In making colored blocks the following colors 
 may be used: The proportions given should vary according to cir- 
 cumstances, different materials giving different colors. There is one 
 coloring matter that is a benefit — that is lampblack; all other colors 
 are more liable to be an injury than a benefit. In mixing it is best 
 to mix your coloring with the sand. The barrel to be used for meas- 
 uring should be the size of a cement barrel. To obtain blue, use 3^ 
 lbs. of ultramine blue to one barrel of sand; dark blue, 1 lb. of Ger- 
 mantown lampblack. For red use 10 lbs. violet oxide to one barrel 
 of sand; if a small amount of lampblack is used the color will hold 
 better but will be changed. For buff, use 5 to 7 lbs. of yellow ocher 
 per barrel of sand, and for brown use 6 lbs. of brown ocher to a 
 barrel of sand. 
 
 By using the coloring judiciously the blocks will be made so 
 that no two stones will be alike. The way to do this is to mix and 
 wet two different kinds of facing; they can be both colored or one 
 can be without coloring. Spread out one mixture an inch or two 
 thick, then put the other on top of it, give the two a light turning 
 and use as facing. Another way is to put a little of one mixture and 
 then a little of the other into the mold. 
 
 H. H. Frantz. — The coloring of concrete blocks can, as a rule, 
 be accomplished only at the expense of loss of strength, with the pos- 
 sible exception of red, which may be secured by the addition of finely 
 ground oxide of iron mixed with the facing cement. 
 
 H. G. Richey. — In making concrete blocks the manufacturer 
 should be able to imitate or match any of the various natural stones; 
 this can be done by using the proper coloring materials. All coloring 
 materials should be the best to be obtained, and should be used care- 
 fully, just enough being used to give the desired shade. The coloring 
 
MANUFACTURE AND USE 91 
 
 material should be measured very carefully so as to get every batch 
 of mortar or concrete of the same shade. The following is a list of 
 the most common coloring materials used and the amount to be used 
 with a barrel of cement. Of course, these quantities will vary accord- 
 ing to the color of the cement used and the color of the block 
 desired. Usually coloring materials will lessen the strength of the 
 mortar or concrete, so no more than necessary should be used; this 
 is especially so of the ochers. To color black use 45 lbs. of man- 
 ganese dioxide to a barrel of cement; brown, 25 lbs. of best roasted 
 iron oxide, or 15 or 20 lbs. of brown ocher per barrel of cement; blue, 
 use 19 lbs. of ultramarine to a barrel of cement; buff, use 15 lbs. 
 of ocher to a barrel of cement, but this will greatly reduce the 
 strength of the block; green, use 23 lbs. of greenish blue ultramine 
 to a barrel of cement; gray, use 2 lbs. of Germantown lampblack 
 (bone black) to a barrel of cement; red, use 22 lbs. of raw iron 
 oxide to a barrel of cement; bright red, use 22 lbs. of Pompeiian or 
 English red to a barrel of cement; purple, use 20 lbs. of Princess 
 metallic to a barrel of cement; violet, use 22 lbs. of violet oxide of 
 iron to a barrel of cement; yellow, use 22 lbs. of ocher to a barrel 
 of cement. Ultramarine is one of the best coloring materials, as it 
 does not affect the strength of the cement. Germantown lampblack 
 is also good on account of the small quantity necessary to give a 
 good color. Do not use common lampblack or Venetian red, as they 
 are liable to run and fade. In coloring blocks the wet mixture should 
 be colored several shades darker than that desired in the finished 
 block, as the wet mortar looks darker to the eye (owing to the gloss 
 of the water) than it really is. Concrete blocks should not be too 
 dark as this is contrary to nature; all natural stones are of a light 
 color or shade, thus in making a concrete block it should be given 
 tone rather than color. The sand used for the colored mortar should 
 be perfectly dry, and the cement, sand and coloring matter mixed 
 thoroughly before being wet. Various shades and colors can be 
 obtained by the use of different cements; for instance, a blue cement 
 used in connection with light colored sand will produce a light blue 
 block. Experiments should be made with the various sands and 
 cement to be obtained so as to know what colors of stone can be pro- 
 duced without the addition of coloring matter. 
 
 Joseph Babiczky.— Facing and coloring for cement blocks have 
 been much discussed. I can see no reason why rock face has been 
 used so much. Concrete blocks are too fine grained and too uniform 
 in color to have such a face applied to them. Smooth or flat tooled 
 faces are more suitable to the material. Facing blocks with an extra 
 rich mixture to make them waterproof results in too smooth a sur- 
 face; if any facing is used it should be made with crushed granite 
 or marble. This gives a fine effect and does not cost much more than 
 
92 CONCRETE BLOCKS 
 
 colored faces, which can be obtained by adding different mineral 
 colors to the concrete. 
 
 U. G. Hayne. — In using coloring matter, mineral colors are the 
 safest. Take the proportion of the coloring decked upon and mix 
 it and the cement thoroughly, then add the necessary sand and mix 
 all together until of a uniform color, then add water and mix until of 
 a uniform color and of the wetness desired. For a black stone, take 
 1 cu. ft. of cement and 2 cu. ft. of sand, to this add 3 lbs. of excelsior 
 carbon black; for a gray stone add 1 lb. of excelsior black to tn*> 
 above quantity of sand and stone. Using the same quantities of 
 cement and sand add for the following colors: Dark blue, 4 lbs. 
 ultramarine blue; brown, 4 lbs. brown ochre; bright red, 7 lbs. 
 English red; red, 5 lbs. violet oxide of iron (raw). Coloring matter 
 should be used sparingly, as much of it is detrimental to the setting 
 of the cement. 
 
 Fig. 7. Stamped Metal Forms for Pitch-Faced Wall Blocks. 
 
 ORNAMENTAL WORK. 
 
 H. H. Rice.— Of ornamental work I would say, leave it to a 
 specialist. It is possible to produce most beautiful figures in cement 
 work by simple processes, but poor ornamentation is an abomination, 
 and a high degree of skill is required to obtain effects really artistic. 
 In every manufacturing center you will find factories exclusively 
 devoted to this branch of the cement industry. If you value your 
 peace of mind or care for your profits you will, until you have 
 acquired skill through long experience, give to such a factory the con- 
 tract for that part of your work. 
 
 H. G. Richey.— For making special molds for rock face work 
 sheets of stamped metal in imitation of rock face can be procured 
 at little cost, as shown by Fig. 7, and this can be cut and shaped to 
 make any size block desired. This metal can be procured in blocks 
 of various sizes and also in lengths of 5 ft. and from 6 to 12 ins. 
 in width. These stamped shapes can also be procured for making 
 
MANUFACTURE AND USE 93 
 
 piers, porch columns, etc. Fig. 8 shows stamped metal suitable for 
 this work. 
 
 Molds for the nosing and molding of steps can also be made in 
 sheet metal, and a step of this kind will look much better than a 
 plain one. For making molds for cornices, moldings, etc., stamped 
 and bent sheet metal can be used as shown by Fig. 9. 
 
 Fig. 8. Form for Pitch- 
 
 Faced Column Blocks. 
 
 These members can be got in any size and shape desired and 
 up to 8 ft. in length. Circle molds as shown by Figs. 10 and 11 are 
 also made in stamped or spun metal, and make excellent molds for 
 bases and caps of columns. 
 
 Spun ballusters in sheet metal can be cut apart and used for 
 
94 
 
 CONCRETE BLOCKS 
 
 molds for casting cement ballusters. In cutting the molds for circle 
 work they should be cut in three pieces so as to be more easily re- 
 moved from the cast stone. 
 
 Special molds for ornamental work of all kinds can be made 
 from stamped metal. The metal when stamped in one piece can be 
 used direct as a mold for ornamental work, or if the design is made 
 up of several pieces of metal soldered together a mold can be made 
 by taking an impression direct from the face of the metal ornament 
 with a glue composition. In this way a mold can be made to dupli- 
 cate any ornament desired. This glue mixture for making molds for 
 plaster or cement ornaments is made as follows: 
 
 Take the very best glue to be obtained, place it in cold water at 
 night, the next morning take it out; when it will be found to be 
 swollen. The water it has absorbed during the night is sufficient to 
 melt it by heat; then mix as much glycerine with it as you had glue 
 and keep the vessel containing them in a steam or hot water bath 
 till the water is about evaporated, and till there is left as much in 
 weight as the weight of the dry glue and glycerine taken together 
 amounted to. This will make a compound of glue and glycerine 
 which will never dry, and a mold of it can be remelted and used 
 over and over again. 
 
 The most intricate design can be made in these molds, and with 
 a little practice the mechanic will be able to turn out ornaments and 
 work to conform to or duplicate any architectural design and add a 
 great percentage to the appearance of any building he may erect or 
 furnish the blocks for. 
 
 Molds can be made in cement for plainer ornaments or moldings; 
 the cement can be poured on the original and when hard can be re- 
 moved, and this reverse impression of the ornament or molding can 
 
 Stamped Metal Circle Moldings for Column Cap and Base Blocks. 
 
 be used as a mold in which to cast the ornament. Before pouring on 
 the cement the original ornament should be given a coat of linseed 
 oil to prevent the cement from sticking. 
 
 After the cement mold is hard it should be given a coat of paint 
 made by dissolving asphalt with turpentine or benzine. This will 
 give the mold a smooth surface, which, if coated with a soap solution, 
 will not stick to the cast. 
 
 Fig. 10. 
 
 Pig. 11. 
 
MANUFACTURE AND USE 
 
 95 
 
 In making molds or ornamental blocks several can be made along 
 with the ordinary day's work, and in this way will not require a 
 large number of molds for each design. 
 
 Figs. 12 and 13 are specimens of stamped metal suitable for orna- 
 
 Fig. 12. Stamped Metal Form Suitable for Ornamental Block. 
 
 mental molds; and Figs. 14 and 15 show a pilaster capital and a 
 panel made of cement cast in glue molds as described. 
 
 Fig. 13. Metal Form for Ornamental Block. 
 
 Cement moldings can also be run in long lengths with a mold 
 similar to that used in running stucco or plaster cornices; then the 
 molding can be cut into the desired lengths. 
 
 To make a success of the concrete block business the proprietor 
 must have mechanics who will be able to make any special mold 
 desired to reproduce the designs and ideas of the architect. 
 
 ■ 
 
 mn 
 
96 
 
 CONCRETE BLOCKS 
 
 The past use of concrete blocks has shown and" developed very 
 little along this line, nearly all of the work done in the past 
 has been confined to the product of machines and to an imitation 
 of rock face work, and this is an imitation of the cheapest and most 
 common class of stone work. 
 
 Fig. 14. Concrete Panel Cast in Glue Mold. 
 
 The reason of this has been that the majority of the molds fur- 
 nished with the various machines have been for this kind of work 
 only. 
 
 The successful block manufacturer must break away from this 
 sameness of production and produce blocks in imitation of the better 
 class of stone work. It costs no more to make blocks of this kind 
 than those imitating the most common work except the cost of the 
 
 Fig. 13. Concrete Column Capital Cast in Glue Mold. 
 
 molds and perhaps a little extra work, but. this will pay in the end. 
 
 Take blocks made in an ordinary box moid, with the face troweled 
 smooth as for sidewalks, and you have a good imitation of rubbed 
 stone and also a waterproof block; water does not go through a 
 sidewalk simply because the face or top is troweled smooth and is 
 made of a strong mixture of cement. To float the block off with a 
 
MANUFACTURE AND USB 
 
 97 
 
 cork or wooden float and leave it a rough sand finish gives a very 
 desirable effect. 
 
 A tool can be made of corrugated metal or of cast iron in the 
 form of a trowel, which can be used on the face of the block and 
 which will give a correct imitation of droved work on cut stone. 
 
 Blocks finished in this way are very pleasing to the eye, as the 
 small corrugations (about ^-in. apart) take away the gloss or smooth 
 surface from the stone. 
 
 In the operation of a concrete block plant there will continually 
 develop new ideas for making of molds and of ornamental blocks, 
 and the man who is always on the alert to adopt new ideas which 
 will assist him in turning out varied designs of blocks will be the 
 one to succeed in the business. 
 
 The cement or concrete block houses of the past have not been 
 designed by architects, but as a rule have been merely four walls 
 built up and a roof put on them; but the concrete block house of 
 the future will be designed by architects. Architects have been slow 
 to take up concrete block construction for this reason, they have not 
 been able to get their designs and ideas reproduced in the concrete 
 blocks. It will thus be seen that the man who equips his plant in 
 such a manner so as to be able to turn out blocks according to, and 
 which will conform to the architects' sizes and drawings, will be the 
 man to make a success of the concrete block business. 
 
 H. H. Frantz. — Ornamental faces may be had at but little addi- 
 tional expense by procuring stamped patterns of thick oiled card- 
 board, such as are employed by wall decorators in all cities. By 
 placing one of these patterns in the bottom of the mold and filling 
 the concrete on top if it, its duplicate will be obtained on the block 
 face after washing the cardboard off with hot water. Another very 
 pretty effect can be easily produced by the employment of an ordi- 
 nary sheet of paper and a stencil. Lay the stencil on the paper and 
 apply a brush coat of glue, the pattern of the stencil will be produced 
 in glue on the paper. On the wet glue sprinkle granite or marble 
 chips or crushed glass of bright color and after the glue has become 
 dry shake off all loose particles. Lay the paper face up in the molds 
 and fill above with concrete. When the block has hardened and the 
 paper has been washed off, the pattern will appear in marble chips 
 or what not. 
 
 SPECIAL BLOCKS. 
 H. H. Rice. — I shall now consider the manufacture of a class of 
 specialties which will greatly embarrass the operator if he be not 
 prepared to meet the issue. I refer to such portions of a building as 
 may fairly be grouped as sills, lintels, caps, coping, belt courses, 
 arches and key stones. No machine of which I have knowledge, 
 which may be truly characterized as a concrete block machine, is 
 
98 CONCRETE BLOCKS 
 
 capable of satisfactorily producing these parts except in most limited 
 sizes and designs. It is true some have attachments and others have 
 cumbrous and unwieldy auxiliary machines of limited adjustability. 
 In my opinion these attachments and auxiliary machines are made 
 solely to sell, and do not embody the fundamental idea of mutual 
 benefit as between manufacturer and operator. I have had a laborer, 
 unskilled in carpentry beyond the use of saw and hammer, prepare 
 from S-l-S boards molds for these things with most excellent results. 
 They may be adjustable, too. The principle of their making is ex- 
 plained in the mold first described in the preceding section. If orna- 
 mentation is desired it is easily secured. If a molded belt course is 
 needed, put a piece of stock molding in the bottom. If the demand 
 be for arch blocks or keystones, ascertain the radius and cut the 
 boards at the required angle. Put your face matter in first and back 
 with concrete as wet as can be tamped. If sills or lintels are over 
 4-ft. in length, reinforce with an angle iron embedded in the concrete. 
 
 H. H. Frantz. — The production of special blocks is simply a 
 matter of pattern making. Sills, caps, keys stones and all the orna- 
 mentation of an architect's design can be readily executed in wooden 
 molds. 
 
 WATERPROOFING. 
 U. G. Hayne. — There are localities where waterproof walls 
 are very essential, while other places where the rainfall is very 
 small have very little need of such a wall. Where one is required, 
 good results can be obtained from a waterproofing mixture of alum, 
 lye and cement, to be used as a wash, and made of the following pro- 
 portions: 
 
 Dissolve 1 lb. of concentrated lye and 5 lbs. of alum in two 
 gallons of water, care being taken to have every particle dissolved. 
 Heating to near the boiling point will quickly insure this without 
 injury to the mixture. This constitutes the "stock" and may be 
 mixed in any quantity. To one pint of the stock add 10 lbs. of 
 cement, thinning out with water until the mixture spreads easily 
 and well on the blocks or walls with a calsomine or whitewash 
 brush, filling all the pores in the face of the block. This is satis- 
 factorily done when it lathers freely under the brush. Usually one 
 pint of the stock put into a 12-qt. pail and 10 lbs. of cement stirred 
 in, with enough water added to well fill the bucket, makes the wash 
 about right. 
 
 Much depends, however, upon the condition of the surfaces to 
 be coated, as to how dry they are. If too dry, wet them down with 
 a spray or a brush ahead of the waterproofing, the object being 
 to apply the wash as thin as practicable without running, rubbing 
 the wash well into the block with the brush. The wash should 
 be applied to the face of the block that is to be exposed in about 
 
MANUFACTURE AND USE 99 
 
 three or four days after it has been made, and while the block is 
 being kept wet in curing, as a few hours are sufficient for the wash 
 to harden enough to stand a spray. The wash is not satisfactory 
 on old work, and should be applied while the block is under cover 
 from the sun and where it is moist. Otherwise too rapid evapora- 
 tion of the water in the wash will leave the cement without the 
 necessary moisture to set it and leaving it so it can be brushed off. 
 The wash should never be applied too thick or it will be liable to 
 scale off similar to paint that is applied too thick. 
 
 One part "stock" and about thirty parts water can be used for 
 wetting the one part cement to two parts sand mixture that the 
 blocks are faced with, instead of using water, with good results. 
 This will leave the face of the block as it comes from the mold 
 without the mark of a brush on it. 
 
 I have seen this wash used for over twelve years, and in no 
 instance, where it has been applied correctly, has it failed to make 
 the surface waterproof. In fortification work I have seen sand fills 
 sluiced over the top of concrete surfaces under which were rooms 
 and passages, and the water stood for weeks above them without 
 a sign of any of it coming through. Have used it on cable tanks 
 with complete success. Two tanks constructed seven years ago, and 
 made to hold 6 ft. of water, have been in use continually since that 
 time and lose no water except by evaporation. In this case two 
 coats of the wash was applied to the inside and bottom of the 
 tanks, and also to the outside walls. The concrete was first 
 plastered with a coat of one part cement to two parts of sand 
 mortar. 
 
 A large store house constructed eight years ago, with solid 
 walls 1 ft. thick, in a climate where the annual rainfall is about 
 80 ins., was given two coats of the wash under the same condition 
 as the cable tanks, and it has been dry at all seasons since, with no 
 sign of moisture on the walls. In addition to its waterproofing 
 properties this wash tends to prevent fungus growth on, or dis- 
 coloration of surfaces coated with it. It thoroughly closes the 
 pores of the plaster and insures dry walls. 
 
 A block faced with a mixture of one part Portland cement to 
 two parts clean sand, well tamped, is nearly waterproof, and if 
 correctly cured will answer in many localities without waterproof- 
 ing. The facing on a correctly made block is in no danger of 
 peeling off. 
 
 The Sylvester process leaves the surface of the concrete look- 
 ing practically the same as when taken from the molds, and in 
 some instances this is much to be desired. The method of mixing 
 and using which is as follows: Dissolve iy 2 ' lbs. of castile soap 
 in 1 gal. of water; also dissolve iy 2 ' lbs. powdered alum in 4 gals. 
 
100 CONCRETE BLOCKS 
 
 of water, when the surface is dry apply the soap wash at boiling 
 heat with a brush, but do not froth the soap. After the soap 
 wash is thoroughly dry apply the alum wash the same way at a 
 temperature of 70° F. The applications should be made twice to 
 secure perfect impenetrability to water. 
 
 The alum and lye wash sprinkled, immediately after applying, 
 with granite dust, or, in fact, with any very fine sand or stone 
 dust, will make the block look very much like natural stone, though 
 I do not see any very good reason why concrete should not be 
 able to pass on its own good looks if dressed up as it should and 
 can be. 
 
 A wall can be painted with an ordinary linseed oil paint and 
 made waterproof for a time the same as a brick wall is sometimes 
 painted, only the paint should not be applied for at least six months 
 after wall is made, as the paint will not stick sooner. Would not 
 make a custom of painting block walls. 
 
 COST. 
 
 U. G. Hayne. — As the cost of the materials varies with each 
 locality, it will be necessary to assume prices at which materials 
 and labor can be purchased, and which can be easily adjusted to 
 suit the location. The prices here given are all higher than in 
 most parts of the country, but prevail in this vicinity. Cement, 
 $2.50 per barrel of about 3.4 cu. ft., or 4 cu. ft. measured loose; 
 sand, $1 per cu. yd.; labor, $2.00 per day of nine hours That in- 
 cidental expenses will amount to about 4% of the total cost of the 
 blocks, which is about right for a small plant, but a little high for 
 a large one. 
 
 The cost of the blocks that will lay the same amount of wall 
 as 1,000 ordinary sized building brick is about $7. This is calcu- 
 lated with a one part cement to four parts sand mixture, and 
 figuring out 25% for the holow spaces. Any other mixture can be 
 figured out with this as a base. For laying blocks of about one 
 to two cubic feet volume, it takes about one-fourth the mortar and 
 about one-third the labor that it takes to lay the same space with 
 brick. The cost of special blocks, to comply with the requirements 
 of the plans will vary according to the difficulty of making them, 
 or from two to four times as much as for ordinary blocks. 
 
 I understand that in some cities the building ordinances permit 
 a hollow block wall to be somewhat narrower than a brick wall 
 would be required for the same space. When in considering the 
 cost of a block, it must be remembered that there is practically 
 no difference in the cost of a plain, panel or rock faced block, and 
 that there is considerable difference in the cost of brick, pressed 
 brick and stone. 
 
MANUFACTURE AND USE 
 
 101 
 
 At the figures given above, a 12 in. wide, by 24 ins. long, by 
 8 in. high, block will cost 19 cts. 
 
 Joseph Babiczky.— The cost of manufacturing blocks varies 
 very much in different localities, but can be calculated near enough 
 before anybody goes into the business of manufacturing blocks. 
 My experience is that one part cement and five parts sand properly 
 mixed, tamped, handled and cured gives as good blocks as any 
 common building stone. Or if suitable crushed stone can be 
 obtained, then 1 part cement, 3% parts sand and 6 parts stone is 
 also a good mixture, supposing that the sand is not too coarse and 
 the crushed stone has a maximum size of % in. down to dust. 
 I will give examples of how to calculate the cost of manufacturing. 
 Suppose a small plant started with four hand machines. 
 
 With four machines 400 blocks can be handled daily. The 
 blocks are supposed to have the following dimensions: 24 x 8 x 8 
 ins., and contains, after deducting the hollow spaces, y 2 ' cu. ft. of 
 concrete. 
 
 Mixture: 1 part cement and 5 parts sand; necessary for 1 
 cu. yd. of concrete, supposing that a barrel of cement — 3.5 cu. ft. 
 
 Cement 27/3 :3.5 = 1.54 bb i s . 
 
 Sand 1 cu. yd. 
 
 Total expenses for 400 blocks daily capacity by using 400 x 0.5 
 = 200 cu. ft. = 7.4 cu. yds. concrete are: 
 Materials : 
 
 Cement 27/5 : 3.5 = 1.54 bbls. 
 
 Sand 7.4 cu. yds. at 60 cts. = 4.44 
 
 Labor : 
 
 4 moulders at $2.00 = 8.00 
 
 2 mixers at 1.50 = 3.00 
 
 1 water boy at 1.00 = 1.00 
 
 Total $36.94 
 
 36.94 
 
 or = $0,925 per block. 
 
 400 
 
 To this must be added the interest of the capital invested, 
 maintenance of the machinery, tools, etc., office expenses, etc. This 
 will make the average price about 10% per block. 
 
 BUILDING CONSTRUCTION. 
 
 N. F. Palmer. — The laying of concrete blocks is the duty of a 
 stone mason, and calls for the same mortars and methods as with 
 a stone or marble building, except that in the stone or marble struc- 
 ture the cutter and trimmer under the scaffold does the preparatory 
 work, from measurements from the wall, while the concrete blocks 
 come to the scaffold the exact size. A concrete block cannot be cut 
 and fitted to the wall — at least, not on the outside — without break- 
 ing the skin or outside set without opening the entire inside of 
 the block to moisture and dampness — the enemy of all stone build- 
 ings. Therefore, the problem for the mason is to lay concrete 
 blocks so that the outside can be pointed up tight and true. 
 
102 CONCRETE BLOCKS 
 
 Foundations should not be made with either mortar blocks nor 
 with brick. Brick foundations, unless treated on the outside, will 
 always create dampness which will permeate the entire superstruc- 
 ture, whether of wood, stone, mortar block or iron. Concrete blocks 
 can be used as foundations, but should be treated on the outside to 
 prevent dampness, and the hollow spaces ventilated. Regular con- 
 crete of 1-3-5 in the usual forms are cheaper than molded blocks 
 of any material for foundations. We have seen foundations holding 
 up four-story brick buildings, made 1-3-5, and the 5 was gravel, not 
 a broken stone in it. We should have preferred broken stone to 
 round gravel. The best Portland cement should always be used 
 in foundation work, no matter if of stone, brick or concrete in any 
 form, but never use hollow mortar blocks in foundations. 
 
 Preparatory to the mason's work it is presumed that the archi- 
 tect's details have called for such units in the wall; and fractions 
 co fit all corners, openings and stretchers as will fit the plan. Cor- 
 ner blocks are laid first, and from the center both ways the marks 
 are made on the foundation by the use of a gauge showing the unit, 
 its half, three-quarter and one-eighth size, etc. No blocks are to 
 be laid on a course until this marking agrees with the plan. Mor- 
 tar should never be spread within one inch of the outside of a 
 finished wall, or in the center line of the block lengthwise of the 
 wall. The outside one inch for pointing up, the center line to 
 permit of longitudinal circulation of air to allow circulation of damp 
 air from the damp side of a building around to the drier side. In 
 pointing up the best Portland cement putty with stone dust, and a 
 small percentage of hydrated lime should be used. In our ex- 
 perience we have seen several concrete block buildings faced with 
 La Farge cement that had the dry appearance on all sides of the 
 structure, because of this method of mason work. In that case, of 
 course, the blocks were faced in the manufacture of the block, and 
 were pointed up after completion. It is well known that La Farge 
 cement is for inside fine finish, and the use of it on the outside of 
 a building was an innovation. To our mind the skill of the mason 
 builder and of the architect on this concrete block building is mani- 
 fest. On the contrary, we have seen buildings erected under charge 
 of this same architect and mason builder who failed to build a satis- 
 factory structure in this same neighborhood with blocks that were 
 not faced, that were cut to fit the wall, where double the number 
 of blocks were made and half the blocks condemned as unfit, mis- 
 takes of the block machine man and lack of knowledge how to plan 
 and how to build. The fact that the same architect and mason 
 builder tried again with a different machine and erected an $8,000 
 Queen Anne building and sold it as soon as completed, is proof 
 that the industry only lacks skill of architect and builder. 
 
MANUFACTURE AND USE 103 
 
 Now, what can be done to a completed building made with 
 mortar or concrete blocks to improve its appearance, or to remedy 
 defects of face mix? Nothing can be done in such building to 
 correct the unequal mortar joints caused by improper size blocks. 
 The joints may be repointed, and the face may be recoated, which 
 will improve the structure. And the manner of doing this can also 
 be followed where the material was first-class as well as the mason's 
 work, by a wash coat of Portland cement and hydrated lime. We 
 have tried this, as well as a wash coat of alum water followed with 
 soap water. The latter method can be done, and then a wash coat 
 of Portland cement and hydrated lime. We have tried this on 
 blocks we know were poorly made; merely to show operation of 
 our machine, and we are satisfied that any concrete block building 
 can be treated and made more impervious and of uniform exterior 
 by a wash coat of 1 Portland cement, % of hydrated lime used as 
 a whitewash. In fact, we have treated chimneys exposed to great 
 changes in temperature, and, in fact, leaky tin roofs, in same man- 
 ner, and are surprised at the result. We give these experiments as 
 the result of practical experience, and in block construction it is 
 well to bring some of these practical experiments to bear in this 
 new industry. 
 
 Geo. H. Crafts. — It is a great mistake for a building block 
 manufacturer to try to compete with common clay, brick or wood 
 construction in price, as to do it he has to make an inferior article 
 which will eventually injure him and the business. Good blocks 
 cannot be made as cheap as common bricks in most localities, and 
 there is no use in competing in price with them. Concrete building 
 blocks do not compete with common bricks, but with natural stones 
 and pressed bricks, and where these materials are cheaper than 
 good building blocks there is no need of a building block plant 
 and it cannot be made a success. This will happen in very few, 
 if any, localities, however, as the cost of quarrying and cutting 
 and laying of natural stones is much more than the cost of making 
 and laying building blocks. The qualities of good concrete blocks 
 will often give it the preference over pressed brick or terra cotta 
 at about the same prices. 
 
 Joseph Babiczky. — Most walls are constructed not only for 
 direct vertical loads, but also to resist the lateral forces which act, 
 if walls are high in comparison with their width. The ideal wall 
 is the monolith concrete wall, and the weakest in construction are 
 the walls built out of brick, as the many horizontal and vertical 
 joints of a brick wall are the weak points in every respect, no 
 matter how carefully built and bonded. The hollow concrete block 
 wall has the advantages of both, without having their disadvan- 
 tages a-s it is almost a monolith as usually laid in first-class cement 
 
104 CONCRETE BLOCKS 
 
 mortar. The face is uniform, can be made in any color or finish 
 and also with architectural design. Offers can be made for build- 
 ing a house per square foot, but before starting the manufacturing 
 of the blocks extra drawings must be prepared showing every block 
 in the building. Then an index must be made, which shows the 
 different sizes and the number of blocks. 
 
 The first thing is to prepare such plans. The architect (if any 
 is engaged) lays out the plans for brick or frame building and his 
 plans must be worked over for cement blocks. It is very simple 
 work, notwithstanding it must be done very carefully. Every 
 phase of manufacturing and also using of cement blocks must be 
 taken into consideration in making advantageous and acceptable 
 plans for this purpose. If possible, whole, three-quarter and one- 
 half blocks must be used, and the use of different sized blocks 
 makes the manufacturing of the concrete blocks complicated, and 
 also building walls out of them, causing extra expenses. Corners, 
 pilasters, etc., must be shown not only in view, but also in plan. 
 The working drawings for the masons must be made clear and easy 
 to read, as otherwise misunderstandings and delay in the work may 
 easily result. 
 
 It happened in my practice that everything was in first-class 
 shape, but I could not get any masons who could lay concrete 
 blocks easily and with a fair amount of speed. I was obliged to 
 watch them and not only see that the blocks were laid after the 
 working drawings but that the wall went up straight, joints pointed 
 up before the cement mortar hardened. Brick masons are not 
 suitable for cement block setting, and they are too high priced, too 
 speedy, and are not accustomed to lifting heavy weights and to do 
 exact work. First-class stone masons are required, but they must 
 also be very closely watched. 
 
 My opinion is that every block manufacturing plant must have 
 not only the special workmen for the manufacturing of concrete 
 blocks, but also those who build them in the wall. The organiza- 
 tion of the concrete block manufacturers or the entire business 
 world which is especially connected with using of cement for the 
 different purposes, must take place without any delay. This is 
 such an important branch now, and it develops with such im- 
 mense rapidity, that an immediate organization of the partakers 
 is indispensable. To protect trade, labor, and to guard the reputa- 
 tion of such an important business branch by a well-organized body, 
 is absolutely necessary. 
 
 Now, often different unions make trouble. The brick masons 
 are of the opinion that the wall out of concrete blocks can only be 
 built by them, the stone masons are of the same opinion, and I 
 think neither of these unions have the right to "butt in," and the 
 
MANUFACTURE AND USE 105 
 
 reason why they do is that they do not have to confront a strongly 
 organized cement-working union. 
 
 Concrete blocks must be laid in good Portland cement mortar, 
 1 part cement and % slacked lime, and 3% parts sand. First, 
 cement and sand must be mixed dry thoroughly, then slacked lime 
 added. 
 
 My experience has been that in summer often cement mortar 
 is half set when the last third part of the batch is used up. The 
 mortar mixers must be instructed and also watched very carefully, 
 as they are mostly accustomed to lime-mortar, which can be used 
 even after days have elapsed without any disadvantage. Let them 
 make small batches and mix thoroughly dry, and after that wet 
 same. 
 
 If late in autumn or early in spring, walls must be built out 
 of concrete blocks; it is better to leave slacked lime out entirely, 
 and use one part cement and three parts sand, as the night frost 
 may destroy the cohesion of the cement mortar if it is not yet set. 
 In hot summer days the blocks must be sprinkled over before set 
 in the wall and the mortar made good and slushy, as otherwise the 
 cement mortar will dry out before it hardens. 
 
 Avoid, if possible, any kind of work with cement in winter 
 time. If unavoidable, be very careful. Never do any work under 
 25° above zero. Under 40° above zero the manufacturing plant 
 must be heated. Be careful and do not use an open coke stove 
 when you are working in a tent, as the gases which develop destroy 
 the top of your tent in a short time. If the temperature is less 
 than 32° above zero, the sand and the water must be heated for 
 the block and also for the mortar. The frost alone does not injure 
 even fresh cement concrete very much, but the alternating of frost 
 and thawing loosen the cohesion and lessens the strength consider- 
 ably. 
 
 I made an interesting experiment on this point last winter, 
 when I was obliged to complete a very important structure as soon 
 as possible. It happened that at noon the thermometer showed 40° 
 above zero, and the next morning 10° below. My blocks, notwith- 
 standing I had a big stove fired night and day, on the north side 
 were frozen bone «hard, and they were covered by hoar frost. I 
 broke off about one-fourth of a block and wrapped it in a paper 
 and placed it in the drawer in my room. I thought that one frost, 
 no matter how strong it was, could not destroy the hardening capac- 
 ity, but only stop the process, as the frozen water is a solid sub- 
 stance by which the hardening process is only stopped. Thus my 
 opinion was proved after three or four days, as the soft and brittle 
 piece of the concrete block thawed out and the hardening process 
 completed satisfactorily; but the wrapping paper was thoroughly 
 
106 CONCRETE BLOCKS 
 
 soaked with water. I remarked before that the blocks on the north 
 side of the tent were covered with hoar frost. This happened be- 
 cause the blocks are better conductors of heat than the air, and so 
 the moisture of the air precipitated on the blocks, forming, after 
 the temperature went under the freezing point, hoar frost on them. 
 After thawed out this precipitated moisture furnished extra moisture 
 for the blocks, which helped the cement to perfect crystalization, 
 but, indeed, in my case, wet also the wrapping, which was a sign 
 that water was present in abundance. 
 
 These blocks were made out of a dry mixture which is abso- 
 lutely necessary in winter time. As when the water passes over a 
 certain percentage, even so by the first freezing the cohesion will 
 be entirely destroyed, which I observed in different cases when soft 
 concrete was poured in forms building up walls. So far as the 
 frost penetrated the concrete became entirely loose, and could be 
 brushed off with even a soft brush. 
 
 Cost of the Complete Wall. 
 The costs of the complete wall are composed : 
 
 (1) Concrete blocks on the ground. 
 
 (2) Cost of materials for mortar. 
 
 (3) Labor. 
 
 (4) Staging. 
 
 I will show in the following a general example how to calculate 
 the costs of the concrete wall: 
 
 (1) Concrete block, 24 x 8 x 8 ins. in the factory.. 10 cents. 
 Handling and hauling to the place where the 
 
 building has to be erected, average 2 " 
 
 Total costs = 12 cents. 
 
 (2) Mortar: 1 cement and 3 sand. 
 
 For 100 blocks are necessary about 9 cu. ft. mortar. 
 9 
 
 Cement : 3.6 = 0.834 bbl. at $1.80 = $1.50 
 
 9 
 
 Sand = 0.333 at GO cents = .20 
 
 27 
 
 Total $1.70 
 
 also, per block 1.7. 
 
 A mason can lay on an average of 10 blocks in one hour, including point- 
 ing, so 40 cents, divided by 10 == 4 cents per block. 
 
 Now suppose a gang of 5 masons working on the place 8 hours each = 40- 
 hours, making 10 blocks an hour = 400 blocks. These 400 blocks having the 
 dimensions of 24 x 8 x 8 ins., will cover 530 sq. ft. The total cost of the 
 
 530 sq. ft. wall will be : 
 
 400 concrete blocks at 12 cents = $48.00 
 
 Mortar 400 x 1.7 cents = 6.80 
 
 Masons 400 blocks at 4 cents — 16.00 
 
 Helpers : 1 mortar mixer. 
 
 1 mortar carrier. 
 
 3 block carriers. * 
 
 2 pulling up mortar and blocks. 
 
 Total 7 helpers at 8 hrs. = 56 hrs. at 18 cents = 10.08 
 
 1 foreman 4.0O 
 
 Staging made out, barrel or horses, material and handling 2.00 
 
 Total $86.92 
 
 8692c. 
 
 — = 16.4 per sq. ft. 
 
 530 sq. ft. 
 Profit, 25%. . . 4.1c. 
 
 Total 20.5c. per sq. ft. complete wall, made 
 
 out of complete blocks. 
 
MANUFACTURE AND USE 107 
 
 Concrete wall of 8 in. is at least as good as brick wall 13 in., 
 as the blocks are at least as strong as any brick of middle quality, 
 and, laid in cement mortar, concrete blocks make almost a mono- 
 lithic wall. 
 
 By comparing a concrete block wall with a wall made out of 
 
 bricks, it must be supposed that pressed face-bricks were applied, 
 
 7 pieces to the square foot, and backed with common red brick. 
 
 The 13-in. wall contains per sq. ft. 21 bricks. The cost of the ready 
 
 brick wall is composed as follows: 
 
 7 pressed face bricks, at $30.00 per 1,000, ready in wall =21 cents. 
 
 14 common red brick at $10.00 per 1,000, ready in wall. =14 " 
 
 Total 35 cents. 
 
APPENDIX I. 
 
 RULES AND REGULATIONS COVERING THE MANUFACTURE 
 AND USE OF HOLLOW CONCRETE BUILDING BLOCKS IN 
 THE CITY OF PHILADELPHIA. 
 
 1. Hollow concrete building blocks may be used for building 
 six stories or less in heigbt, where said use is approved by the 
 Bureau of Building Inspection, provided, however, that such blocks 
 shall be composed of at least one (1) part of standard Portland 
 cement, and not to exceed five (5) parts of clean, coarse, sharp sand 
 or gravel, or a mixture of at least one part of Portland cement to 
 five (5) parts of crushed rock or other suitable aggregate. Provided 
 further, that this section shall not permit the use of hollow blocks 
 in party walls; said party walls must be built solid. 
 
 2. All material to be of such fineness as to pass a ^in. ring 
 and be free from dirt or foreign matter. The material composing 
 such blocks shall be properly mixed and manipulated, and the hollow 
 space in said blocks snail not exceed the percentage given in the 
 following table for different height walls, and in no case shall the 
 walls or webs of the block be less in thickness than one-fourth of 
 the height. The figures given in the table represent the percentage 
 of such hollow space for different height walls. 
 
 Stories. 
 
 1st. 
 
 2d. 
 
 3d. 
 
 4th 
 
 1 and 2 
 
 33 
 
 33 
 
 
 
 3 and 4 
 
 25 
 
 33 
 
 33 
 
 33 
 
 5 and 6 
 
 20 
 
 25 
 
 25 
 
 33 
 
 3. The thickness for walls for any building where hollow con- 
 crete blocks are used shall not be less than is required by law for 
 brick walls. 
 
 4. Where the face only is of hollow concrete building block and 
 the backing is of brick, the facing of hollow concrete blocks must 
 be strongly bonded to the brick either with headers projecting 4 ins. 
 into the brick work, every fourth course being a heading course, 
 or with approved ties, no brick backing to be less than 8 ins. Where 
 the walls are made entirely of hollow concrete blocks, but where 
 said blocks have not the same width as the wall, every fifth course 
 shall extend through the wall, forming a secure bond. All nails 
 where blocks are used shall be laid up in Portland cement mortar. 
 
 5. All hollow concrete building blocks before being used in the 
 construction of any buildings in the City of Philadelphia shall have 
 attained the age of at least three (3) weeks. 
 
MANUFACTURE AND USB 109 
 
 6. Wherever girders or joists rest upon walls so that there is 
 a concentrated load on the block of over two (2) tons, the blocks 
 supporting the girder or joists must be made solid. Where such 
 concentrated load shall exceed five (5) tons, the blocks for two (2) 
 courses below, and for a distance extending at least 18 ins. each 
 side of said girder shall be made solid. Where the load on the wall 
 from the girder exceeds five (5) tons, the blocks for three (3) 
 courses underneath it shall be made solid with similar material 
 as in the blocks. Wherever walls are decreased in thickness the 
 top course of the thicker wall to be made solid. 
 
 7. Provided always that no wall or any part thereof composed 
 of hollow concrete blocks shall be loaded to an excess of eight (8) 
 tons per superficial foot of the area of such blocks, including the 
 weight of the wall, and no blocks shall be used that have an average 
 crushing at less than 1,000 lbs. per sq. in. of area at the age of 
 28 days, no deduction to be made in figuring the area for the hol- 
 low spaces. 
 
 8. All piers and buttresses that support loads in excess of 
 five (5) tons shall be built of solid concrete blocks for such dis- 
 tance below as may be required by the Bureau of Building Inspec- 
 tion. Concrete lintels and sills shall be reinforced by iron or steel 
 rods in a manner satisfactory to the Bureau of Building Inspection, 
 and any lintels spanning over 4 ft. 6 ins. in the clear shall rest on 
 solid concrete blocks. 
 
 9. Provided, that no hollow concrete building blocks shall be 
 used in the construction of any building in the City of Philadelphia, 
 unless the maker of said blocks has submitted his product to the 
 full test required by the Bureau of Building Inspection, and placed 
 on file with said Bureau of Building Inspection, a certificate from 
 a reliable testing laboratory showing that samples from the lot of 
 blocks to be used have successfully passed the requirements of the 
 Bureau of Building Inspection, and filing a full copy of the test 
 with the Bureau. 
 
 10. A brand or mark of identification must be impressed in 
 or otherwise permanently attached to each block for purpose of 
 identification. 
 
 11. No certificate of approval shall be considered in force 
 for more than four months unless there be filed with the Bureau 
 of Building Inspection of the City of Philadelphia, said samples to 
 every four months following, a certificate from some reliable physi- 
 cal testing laboratory showing that the average of three (3) speci- 
 mens tested for compression, and three (3) specimens tested for 
 transverse strength comply with the requirements of the Bureau 
 of Building Inspection of the City of Philadelphia, samples said to 
 be selected either by a building inspector or by the laboratory, from 
 
HO CONCRETE BLOCKS 
 
 blocks actually going into construction work, samples must not be 
 furnished by the contractors or builders. 
 
 12. The manufacturer and user of any such hollow concrete 
 blocks as are mentioned in this regulation, or either of them, shall 
 at any and all times have made such tests of the cements used in 
 making such blocks or such further tests of the completed blocks, 
 or of each of these, at their own expense, and under the supervision 
 of the Bureau of Building Inspection, as the Chief of said Bureau 
 shall require. 
 
 13. The cement used in making said blocks shall be Portland 
 cement, and must be capable of passing the minimum requirements 
 as set forth in the "Standard Specifications for Cement" by the 
 American Society for Testing Materials. 
 
 14. Any and all blocks, samples of which on being tested under 
 the direction of the Bureau of Building Inspection, fail to stand 
 at 28 days the tests required by this regulation, shall be marked 
 condemned by the manufacturer or user and shall be destroyed. 
 
 15. No concrete blocks shall be used in the construction of 
 any building within the City of Philadelphia until they shall have 
 been inspected, and average samples of the lot tested, approved and 
 accepted by the Chief of the Bureau of Building Inspection. 
 
SPECIFICATIONS GOVERNING METHOD OF TESTING HOL- 
 LOW BLOCK. 
 
 1. These regulations shall apply to all new materials such as 
 •are used in building construction, in the same manner and for the 
 same purposes, as stones, brick, concrete, are now authorized by the 
 building laws, when said new material to be substituted departs 
 from the general shape and dimensions of ordinary building brick 
 and more particularly to that form of building material known 
 as hollow concrete block manufactured from cement and a certain 
 addition of sand, crushed stone or similar material. 
 
 2. Before any such material is used in buildings, an applica- 
 tion for its use and for a test of the same must be filed with the 
 ■Chief of the Bureau of Building Inspection. A description of the 
 material and a brief outline of its manufacture and proportions 
 of the material used must be embodied in the application. 
 
 3. The material must be subjected to the following tests: 
 Transverse, compression, absorption, freezing and fire. Additional 
 tests may be called for when, in the judgment of the Chief of the 
 Bureau of Building Inspection, the same may be necessary- All 
 such tests must be made in some laboratory of recognized standing, 
 under the supervision of the engineer of the Bureau of Building 
 Inspection. The tests will be made at the expense of the applicant. 
 
 4. The results of the tests, whether satisfactory or not, must 
 be placed on file in the Bureau of Building Inspection. They shall 
 be open to inspection upon application to the Chief of the Bureau, 
 but need not necessarily be published. 
 
 5. For the purposes of the tests, at least twenty (20) samples 
 •or test pieces must be provided. Such samples must represent the 
 ordinary commercial product. They may be selected from stock by 
 the Chief of the Bureau of Building Inspection, or his representa- 
 tive, or may be made in his presence, at his discretion. The sam- 
 ples must be of the regular size and shape used in construction. 
 In cases where the material is made and used in special shapes 
 :and forms too large for testing in the ordinary machines, smaller 
 sized specimens shall be used as may be directed by the Chief of 
 Bureau of Building Inspection, to determine the physical charac- 
 teristic specified in Section 3. 
 
 6. The samples may be tested as soon as desired by the ap- 
 plicant, but in no case later than 60 days after manufacture. 
 
 7. The weight per cubic foot of the material must be deter- 
 mined. 
 
112 CONCRETE BLOCKS 
 
 8. Tests shall be made in series of at least five, except that 
 in the fire tests a series of two (four samples) are sufficient. Trans- 
 verse tests shall be made on full-sized samples. Half samples may 
 be used for the crushing, freezing and fire tests. The remaining 
 samples are kept in reserve, in case unusual flaws, or exceptional 
 or abnormal conditions, make it necessary to discard certain of the 
 tests. All samples must be marked for identification and com- 
 parison. 
 
 9. The transverse tests shall be made as follows: The samples 
 shall be placed flatwise on two rounded knife edge bearings set 
 parallel, 7 ins. apart. A load is then applied on top, midway be- 
 tween the supports, and transmitted through a similar rounded 
 knife edge, until the sample is ruptured. The modulus of rupture 
 shall then be determined by multiplying the total breaking load in 
 pounds by 21 (three times the distance between supports in inches) 
 and then dividing the result thus obtained by twice the product of. 
 
 the width in inches by the square of the depth in inches. R — 3 W *2 
 
 2bd 
 
 No allowance should be made in figuring the modulus of rupture 
 for the hollow spaces. 
 
 10. The compression test shall be made as follows: Samples 
 must be cut from blocks so as to contain a full web section; samples 
 must be carefully measured, then bedded flatwise in plaster of paris 
 to secure a uniform bearing in the testing machine and crushed. 
 The total breaking load is then divided by the area in compression 
 in square inches. No deduction to be made for hollow spaces; the 
 area will be considered as the product of the width by the length. 
 
 11. The absorption tests must be made as follows: The sample 
 is first thoroughly dried to a constant weight. The weight must be 
 carefully recorded. It is then placed in a pan or a tray of water, 
 face downward, immersing it to a depth of not more than in. It 
 is again carefully weighed at the following periods: 30 minutes, 
 four hours, and 48 hours, respectively, from the time of immersion, 
 being replaced in the water in each case as soon as the weight is 
 taken. Its compressive strength, while still wet, is then determined 
 at the end of the 48-hour period in the manner specified in Section 10. 
 
 12. The freezing tests are made as follows: The sample is 
 immersed, as described in Section 11, for at least four hours and 
 then weighed. It is then placed in a freezing mixture or a refrig- 
 erator, or otherwise subjected to a temperature of less than 15° F. 
 for at least 12 hours. It is then removed and placed in water, where 
 it must remain for at least one hour, the temperature of which is 
 at least 150° F. This operation is repeated ten times, after which 
 the sample is again weighed while still wet from the last thawing. 
 
MANUFACTURE AND USE 113 
 
 Its crushing strength should then be determined as called for in 
 Section 10. 
 
 13. The fire test must be made as follows: Two samples are 
 placed in a cold furnace in which the temperature is gradually raised 
 to 1,700° F.; the test piece must be subjected to this temperature 
 for at least 30 minutes. One of the samples is then plunged in cold 
 water (about 50° F. to 60° F.) and the results noted. The second 
 sample is permitted to cool gradually in air, and the results noted. 
 
 14. The following requirements must be met to secure an ac- 
 ceptance of the materials: The modulus of rupture for concrete 
 blocks at 28 days old must average 150 and must not fall below 100 
 in any case. The ultimate compressive strength at 28 days must 
 average 1,000 lbs. per sq. in., and must not fall below 700 lbs. in 
 any case. The percentage of absorption (being the weight of water 
 absorbed divided by the weight of the dry sample) must not average 
 higher than 15% and must not exceed 20% in any case. The reduc- 
 tion of compressive strength must not be more than 33%%, except 
 that when the lower figure is still above 1,000 lbs. per sq. in. the loss 
 in strength may be neglected. The freezing and thawing process 
 must not cause a loss in weight greater than 10% nor a loss in 
 strength of more than 33%%, except that when the lower figure is 
 still above 1,000 lbs. per sq. in. the loss in strength may be neglected. 
 The fire test must not cause the material to disintegrate. 
 
 15. The approval of any material is given only under the fol- 
 lowing conditions: 
 
 (a) A brand mark for identification must be impressed on or 
 otherwise attached to the material. 
 
 (b) A plant for the production of the material must be in full 
 operation when the official tests are made. 
 
 (c) The name of the firm or corporation and the responsible 
 officers must be placed on file with the Chief of the Bureau of Build- 
 ing Inspection, and changes in the same promptly reported. 
 
 (d) The Chief of the Bureau of Building Inspection may 
 require full tests to be repeated on samples selected from the open 
 market, when, in his opinion, there is any doubt as to whether the 
 product is up to the standard of these regulations and the manu- 
 facturer must submit to the Bureau of Building Inspection once 
 in at least every four months a certificate of tests showing that 
 the average resistance of three specimens to cross breaking and 
 crushing are not below the requirements of these regulations. Such 
 tests must be made by some laboratory of recognized standing on 
 samples selected by a building inspector or the laboratory from 
 material actually going into construction, and not on ones furnished 
 by the manufacturer. 
 
 WC rjT'v .1 ...I :i * I 
 
114 CONCRETE BLOCKS 
 
 (e) In case the results of tests made under these conditions 
 should show that the standard of these regulations is not main- 
 tained, the approval of this bureau to the manufacturer of said 
 blocks will at once be suspended or revoked. 
 
 Tests made under the specifications of the City of Philadelphia 
 on concrete blocks in the market here have developed about the 
 following results: Modulus of rupture, 150 to 175 lbs.; compressive 
 strength, 1,200 to 1,600 lbs. per sq. in.; absorption, 5%. 
 
 The compressive strength is reduced little, if any, by the water 
 absorbed. Freezing tests show little loss. The average compressive 
 strength after freezing is in the vicinity of 1,000 lbs. per sq. in. 
 The blocks passed the fire tests well. 
 
 APPENDIX II. 
 
 To aid those readers who desire to avail themselves of the 
 descriptive pamphlets and similar trade literature issued by the 
 various concerns making concrete block machines, molds and tools 
 the following list of manufacturers has been compiled: 
 
 American Hydraulic Stone Co., Denver, Colo. 
 
 Automatic Building Block Machine Co., Jackson, Mich. 
 
 Blakeslee Concrete Block Machine Co., Columbus, O. 
 
 Brady Cement Stone Machine Co., Jackson, Mich. 
 
 Cement-Normandin Machinery Co., Jackson, Mich. 
 
 Cement Machinery & Mfg. Co., Burlington, la. 
 
 Cement Working Mach'y Co., 193 Lafayette Ave., Detroit, Mich. 
 
 Century Cement Machine Co., 181 Main St., W. Rochester, N. Y. 
 
 Coltrin Mfg. Co., Jackson, Mich. 
 
 Concrete Construction Co., 3 Broad St., New York City. 
 (Machines for Export.) 
 
 Cottom Artificial Stone & Mfg. Co., Dayton, O. 
 
 Drake Standard Machine Co., 300 Jackson Boulevard, Chicago. 
 
 K. Dykema & Son, Grand Rapids, Mich. 
 
 Z. Fielder & Son, 1017 Broadway, Hannibal, Mo. 
 
 H. E. Goodwin, 208 Blake St., Indianapolis, Ind. 
 
 Hayden Automatic Block Machine Co., Columbus, O. 
 
 Ideal Concrete Machinery Co., South Bend, Ind. 
 
 International Concrete Block Machine Co., Minneapolis, Minn. 
 
 Iowa Building Block Machine Co., Waterloo, la. 
 
 L. D. Libby, 238 Second Ave., South Minneapolis. 
 
 Michigan Cement Block Machinery Co., Union City, Mich. 
 
 Miles (P. B.) Mfg. Co., Jackson, Mich. 
 
 Miracle Pressed Stone Co., Minneapolis, Minn. 
 
 National Hollow Concrete Machine Co., Washington, D. C. 
 
 Nolan & Layman, 2801 18th Ave., South Minneapolis, Minn. 
 
MANUFACTURE AND USE 115 
 Harmon S. Palmer Co., 1450 Binney St., Washington, D. C. 
 Noyes F. Palmer Mfg. Co., 150 Snediker Ave., Brooklyn, N. Y. 
 Pettyjohn Bros., Terre Haute, Ind. 
 
 Scott Mfg. Co., Commonwealth Trust Building, St. Louis, Mo. 
 W. J. Scoutt, 60 West Washington St., Chicago, 111. 
 E. W. Seamans, Grand Rapids, Mich. 
 Simplex Mfg. Co., Jackson, Mich. 
 
 Standard Stone Co. of America, 140 Nassau St., New York City. 
 
 Standard Sand & Machine Co., Cleveland, O. (1509 St. Clair St.). 
 
 Stevens Cast Stone Co., 608 Chamber of Commerce, Chicago, 111. 
 
 Stewart Cement Block Machine Co., Waterloo, la. 
 
 Stringer Machine Co., Jackson, Mich. 
 
 Underwood Building Block Machine Co., Columbus, O. 
 
 U. S. Cement Shingle Machinery Co., Saginaw, Mich. 
 
 Universal Concrete Machine Co., Norfolk, Va. 
 
 Variety Machine Mfg. Co., 116 First Ave. N., Minneapolis, Minn. 
 
 Waterloo Automatic Stone Machine Co., Waterloo, la. 
 
 Winget Concrete Machine Co., Columbus, O. 
 
 Winner Concrete Block Machine Co., Minneapolis, Minn. 
 Concrete Construction Co., Steubenville, O., 
 (Manufacturers of Molds for Ornamental Construction). 
 
 A. H. Kennedy, Rockport, Ind. 
 (Template Puller for Concrete Blocks). 
 
 Collapsible Centering Construction Co., Detroit, Mich. 
 (Collapsible Centers for Concrete Conduits or Arches). 
 
 L. A. Pratt, Bay City, Mich. 
 (Galvanized Iron Flasks for Concrete Fence Posts). 
 
 J. A. Mitchell, Goshen, Ind., Concrete Fence Posts. 
 
 J. H. Emery, West Bay City, Mich., Cement Brick Machine. 
 
 Keystone Hollow Cement Block Machine Co., Phoenixville, Pa. 
 
 Hartwick Concrete Block Machine Co., Jackson, Mich. 
 
 Frost Concrete Stone Co., Waterloo, la. 
 
 Perfection Block Machine Co., Sioux Falls, S. D. 
 
 Bright & Co., No. High St., Columbus, O. 
 
 Auburn Concrete Machinery Works, Auburn, Ind. 
 
 Fishers Hydraulic Stone System, Memphis, Tenn. 
 
 Concrete Hollow Wall Constr. Co., 1520 Ashland Bk., Chicago. 
 
 Walton Granolithic Stone Machine Co., Kansas City, Mo. 
 
 W. P. Bryson, 939 N. Y. Life Building, Kansas City, Mo. 
 
 Diamond Cement Block Co., Rock Rapids, la. 
 
 Underwood Building Block Machine Co., Fostoria, O. 
 
 J. A. Noble, Fostoria, O. 
 
INDEX 
 
 Air Spaces in Walls 40 70 8 g 
 
 Alum Water Wash 103 
 
 American Hydraulic Stone Co. (Whittlesey) Patent 41 
 
 Architects' Designs and Specifications 97, 102 
 
 Architectural Considerations 53 
 
 Associated Industries 50 
 
 Blakeslee Patent 37 
 
 Block Machines, Selection of 83 
 
 Buildings of Concrete Blocks 55 101 
 
 Cardboard Faces, Use of 97 
 
 CASTING IN SAND 41, 45, 50 
 
 Competition with Other Processes 52, 55 
 
 CEMENT— 
 
 Gibb's Patent Specifications ' 31 
 
 Proportions in Mixture 76 
 
 Selection of Quality 13 79 
 
 Varieties 12 
 
 CONCRETE r n 
 
 Cinder 15 
 
 Composition 27 
 
 Fire Resisting Quality of 2(5 
 
 Gibb's Patent 31 
 
 How Mixed 29 
 
 Ingredients 27 
 
 Inspection and Tests 28 
 
 Porosity 29 
 
 Use in Various Processes 38, 53 
 
 Varieties 29 
 
 Waterproofing 30 
 
 CONCRETE BLOCK MANUFACTURE— 
 
 Amer. Hydraulic Stone Co.'s Process 41 
 
 Cardboard Mold 97 
 
 Casting in Sand 45 
 
 Coloring 31 ( 90 
 
 Cost of Manufacture 23, 50, 100, 101 
 
 Cuban Methods 45 
 
 Curing 1 9> 87 
 
 Design and Arrangement of Plant G3 
 
 Dierlamm Patent 38 
 
 "Exclusive Rights" { 87 
 
MANUFACTURE AND USE 117 
 
 Facing 21 > 44 > 88 
 
 Forms 70 > 85 
 
 Labor Organizations IO 3 
 
 Limitations of Use 9 
 
 List of Concerns Making Machines, etc 114 
 
 Literature on Processes 49 
 
 Location of Plant G1 
 
 Lowry Patent *3 
 
 Machines 18 > 8(1 
 
 Materials I 2 
 
 Cost of 1°° 
 
 Crushed Stone W 
 
 Gravel 14 
 
 Sand 13 
 
 Volcanic Dust 1" 
 
 Water lf> 
 
 Mather & Bowen Patent 4 7 
 
 Origin and Development 7 
 
 Ornamental Work 92 
 
 Palmer Patents 33 
 
 Patent Rights and Limitations 31 
 
 Points of Consideration 27 
 
 Processes 1? 
 
 Proportions of Mix 29 
 
 Purdy and Henderson Patent Claims 39 
 
 Queen City Brick Machine Co.'s Type 48 
 
 Regulations in Philadelphia 108 
 
 Rhode's Patent 33 
 
 Sizes 24 
 
 Specifications 110 
 
 Special Shapes and Uses 97 
 
 Stamped Metal Molds 94 
 
 Stevens' Patents 45 
 
 Strength 88 
 
 Tamping 17 
 
 Technical Qualifications of Makers 59 
 
 Testing 23, 41 
 
 Types * 3 7 
 
 Use of Stencil 97 
 
 Weights • • • • 72 
 
 "Wet" Process 41 
 
 CONCRETE BLOCK CONSTRUCTION— 
 
 Architects' Designs 97 
 
 Artistic Results , 55 
 
 Causes of Unsatisfactory Work 59 
 
H-8 CONCRETE BLOCKS 
 
 Comparative Costs 51 iq3 
 
 Continuity of Walls 44 
 
 Cost Data 106 
 
 Examples 55 
 
 Fire Resistance 60 
 
 Laying of Blocks 101 
 
 Methods and Details 24 
 
 Objections to 53 
 
 Points of Consideration 27 
 
 Principles of H 
 
 Regulations in Philadelphia 108 
 
 Waterproofing Walls 98 
 
 In Winter 105 
 
 COLORING 31> 88 
 
 Materials Used 90 
 
 Consistency of Mixture 77 
 
 Construction Work 24 
 
 Continuous Mixers 16 
 
 Cores 84 
 
 COST of Manufacture 23, 50 
 
 As Factor in Location 65 
 
 Of Materials 100 
 
 Of Mechanical Outfit for Plant 49 
 
 Crushed Stone 74 
 
 ^UBA — Use of Different Processes 45 
 
 Uses of Concrete Blocks 55 
 
 Curing Process 19 37 
 
 Dierlamm (Peter) Patent 3§ 
 
 Disintegration of Blocks 30 
 
 Drying of Blocks, Effect of 88 
 
 "Dry" Concrete, Advantages of Use 29, 3S 
 
 Dry Process Machine 80 
 
 Duluth Harbor, Construction of Pier 16 
 
 Efflorescence 16 
 
 Engineering Considerations 53 
 
 Establishing a Factory 49 
 
 "Exclusive Rights" SG, 87 
 
 Expansion Joints 54 
 
 FACING 21, 88 
 
 Defects and Remedies 103 
 
 FACTORY Arrangement 6G 
 
 Class of Output 6G 
 
 Desi sn 63 
 
 Equipment 64 
 
 Establishment of 49 
 
 Location 61 
 
MANUFACTURE AND USE 119 
 
 Failure of Concrete Block Construction 59 
 
 Filling Forms 83 
 
 Fireproofing of Buildings 26 
 
 Fire Resisting Quality of Concrete 2G 
 
 "Flying Factory" 65 
 
 Floor Joists, Support of 25 
 
 Forms, Examples of 92 
 
 Foundations, Construction of 102 
 
 Foundation Walls, Composition of Blocks for 29 
 
 Gibb's Patent on Concrete Walls • 31 
 
 Glue Mixture for Making Molds . 94 
 
 GRAVEL 73 
 
 Proportions in Mixture 15. 76 
 
 Substitutes for 75 
 
 Hand Mixing 15. 79 
 
 Hayden Block Machine, and Patent Claims 35 
 
 Hutchinson (C. S.) Patent 33 
 
 Hydraulic Pressure 83 
 
 Labor, Cost of 50 
 
 Labor Unions 51 
 
 La Farge Cement 102 
 
 Laying Blocks 105 
 
 Loam in Sand 74 
 
 Location of Plant 49, 62 
 
 Lowry (Thos. J.) Patent 33 
 
 MACHINES, Guarantee 86 
 
 Payment for Use 87 
 
 Speed of Operation 86 
 
 "Wet" Process 18 
 
 Mixing 15> 78 
 
 Varieties 18 
 
 List of Makers 114 
 
 Mandt Cement Block Co.'s Process 46 
 
 Masonry Work 102, 104 
 
 Materials 72 
 
 Mather & Bowen Patent 47 
 
 "MEDIUM" CONCRETE 29 
 
 Claims of 43 
 
 Machines 82 
 
 Miracle Patent 38 
 
 MIXERS, Selection of 16 
 
 Arrangement of Platform 64 
 
 MIXING, Concrete I 6 
 
 Methods 78 
 
120 CONCRETE BLOCKS 
 
 Process 15 
 
 Tests : 79 
 
 Time Required 80 
 
 Water 16 
 
 MIXTURE, Blocks for Walls 29 
 
 Consistency 77 
 
 Dry 16 
 
 Proportioning 70 
 
 Molding 80 
 
 MOLDS y 84 
 
 Examples 92 
 
 Monolith Wall, Advantages of 103 
 
 Mortar , 105 
 
 Nails, How Used in Concrete 25 
 
 Objections to Concrete Block Construction 53 
 
 Organization of Concrete Block Manufacturers 103 
 
 Ornamental Work 92 
 
 Use of Stencils 97 
 
 Paint for Waterproofing 100 
 
 Painting Cement Molds 94 
 
 Palmer (H. S.) Patent Claims 33 
 
 Parker's Cement 12 
 
 PATENTS on Concrete and Cement (Gibb's).., 31 
 
 On Hollow Concrete Blocks — 
 
 Blakeslee 37 
 
 Claims and Infringements 35 
 
 Peter Dierlamm 38 
 
 C. S. Hutchinson 33 
 
 List of Important Patents 48 
 
 Thos. J. Lowry 33 
 
 Mather & Bowen 47 
 
 Miracle 38 
 
 H. S. Palmer 33 
 
 Purdy & Henderson Claims 39 
 
 T. B. Rhodes 33 
 
 C. W. Stevens 45 
 
 Whittlesey 41 
 
 Machines, Value of Rights 86 
 
 Rights — Territorial Sale 49 
 
 Permeability 16 
 
 Piping of Factory 64 
 
 Plaster 25 
 
 PORTLAND CEMENT 12 
 
 Price of 13 
 
 Pouring Process 17, 83 
 
MANUFACTURE AND USE 121 
 
 Pressing Process 17, 82, 83 
 
 Price of Construction 103 
 
 Proportioning of Mixture 76 
 
 Puzzuolani Cement 12, 73 
 
 Purdy & Henderson Patent Claim 39 
 
 Purchase of Patents Rights 49 
 
 Rhodes (L. B.) Patent 33 
 
 Rotary Kilns 13 
 
 Royalties 49 
 
 SAND, Proportioning 15, 76 
 
 Selection of 73 
 
 Substitutes 74 
 
 Voids , 29 
 
 Sand-Lime Brick 52 
 
 Shipping of Concrete Blocks 65 
 
 Silica- Cement 12 
 
 Sills, Lintels, Keystones, etc 24, 97 
 
 Special Blocks 97 
 
 SPECIFICATIONS for Manufacture and Construction 108 
 
 for Test of Concrete Blocks 110 
 
 Stamped Metal Molds 94 
 
 Stencil Work on Blocks 97 
 
 Stevens Patents 45 
 
 STRENGTH, Effect of Coloring 90 
 
 Effect of Facing 88 
 
 Stone, Broken 75 
 
 Substitutes for Materials 74 
 
 Sylvester Process of Waterproofing 99 
 
 Tamping Process 17, 77, 83 
 
 Temperature 105 
 
 Tents for Factory Plant 65 
 
 TESTING — Concrete Blocks 23 
 
 Mixture 79 
 
 Time for Setting of Mixture 77 
 
 Tracks and Cars, Arrangement 64 
 
 "Two-Piece" System 41, 46 
 
 Types of Blocks 70 
 
 Unionism in Construction Work 104 
 
 Upright-machine 18 
 
 Walls and Partitions 24 
 
 WATER, Proportion in Mixture 76 
 
 Use in Curing Process 87 
 
 WATERPROOFING, Concrete Blocks 40, 98 
 
 Comparative Tests 41 
 
 Concrete 30 
 
122 CONCRETE BLOCKS 
 
 Weight of Blocks 72 
 
 "Wet" Concrete 29, 53 
 
 "WET" PROCESS, Adaptability 45 
 
 Proportions of Mixture , 76 
 
 Machine 81 
 
 Whittlesey Patent 44 
 
 Winter, Cement Work in 105 
 
 Wire Lath 47 
 
 Workman, Class Required for Work 104 
 
 Yard Arrangement for Factory 64