X .£». ,^- , >. ^ LIBRARY OF CONGRESS. ©i^p Gapijrijfat ^a Shelf ....S.I.. UNITED STATES OF AMERICA. Brick for Street Pavements. AN ACCOUNT OF TESTS MADE OF BRICKS AND PAVING BLOCKS, WITH A BRIEF DISCUSSION OF STREET PAVEMENTS AND THE METHOD OF CON- STRUCTING THEM. BY M. D. BURKE, C.E. CONTENTS. le Samples Submitted for Testing Jiow the Specimens were Prepared 7 Description of Specimens Submitted 9 How the Tests were Made 14 Abrasion and Impact 16, 42 Description of the Tables 27 The Chemistry of Brick Manufacturing 36 Discussion of the Tests 38 The Absorption Tests 40 Transverse Strength 41 Statistics of Traffic and Durability of Pavements 43 The Probable Durability o^a Brick Pavement , . 47 Municipal Methods 48 General Discussion of Pavements 53 What Shall be Specified 61 What Has Been Done 68 The Matrix 76 Where Should Brick be Used for Street Pavements 78 Maintenance What is in a Name S3 Size of Paving Brick 84 Brick for Street Pavements. AN ACCOUNT OF TESTS MADE OF BRICKS AND PAVING BLOCKS, WITH A BRIEF DISCUSSION OF STREET PAVEMENTS AND THE METHOD OF CON- STRUCTING THEM. BY M. D. BURKE, C.E. APR 9 ) . /if^X O"' CINCINNATI : ROBERT CLARKE & CO. 1892. a TE^55" Copyrighted, 1892. By KOBERT CLARKE & CO. 0(o-^^173 PREFA^CE. A large part of the contents of this pamphlet was con- tained in a report made to the village authorities of tests of material to be used in paving streets in Avondale, where the writer was employed as village engineer. The investiga- tion then made was as thorough as the time and means at hand would justify. Inquiries for the results of the work have been so numerous, and requests for the same have been so frequently repeated, that it has been deemed advisable to publish the work in this form. If any information or suggestions herein contained shall aid in the construction of better pavements, or prevent the waste of money upon bad ones, or shall bring people to a consideration of placing municipal improvements under sys- tematic control and direction, or shall cause manufacturers to see that their true interest will best be subserved by plac- ing only good material upon the market, then this little pamphlet will have served a useful purpose. x\I. D. BURKE. Cincinnati, March 16, 1892. BRICK FOR STREET PAVEMENTS, The Samples Submitted for Testing. It having been decided that the Main Avenue pavement should be constructed of some form of clay product, a series of tests of the various materials in market was deemed ad- visable in order to aid in selecting the proper variety, and, if found practicable, fix a standard by which the difiterent va- rieties might be adjudged and accepted or rejected, as their qualities and powers of resistance would determine. Ac- cordingly a circular letter was addressed to manufacturers and dealers, requesting them to ship to my office, at 41 Pike Building, Cincinnati, Ohio, samples consisting of twenty or more of each of the varieties of the bricks or blocks manu- factured or sold by them for street paving purposes, to be tested. In response to the circular letter, samples were kindly furnished by the following parties, and numbered as below : 1. Lithonia Georgia Granite, John Regan, contractor, city. 2. West Virginia Brick Co., Charleston, W. Va., H. C. Bruce, President. 3. The Diamond Brick and Terra Cotta Co., Kansas City, Mo. 4. The Pittsburg Sewer Pipe and Fire Clay Co., ^ew Brighton, Pa. 5. Canton Brick Co. (red granite street pavers). Canton, Ohio. (51 b BRICK FOR STREET PAVEMENTS. 6. The Royal Brick Co. (iron rock pavers), Canton, O. 7. Purington Paving Brick Co., Galesbnrg, 111. 8. The United States Fire Clay Co., :N'ew Lisbon, Ohio ; M. li. Coney, agent. 9. The Middleport Granite Brick Co. (Halhvood Block), Middleport, Ohio. 10. L. B. Townsend & Co. (Townsend Paver), Zanesville, Ohio. 11. The Brazil Paving Block, Brazil, Ind., L. H. xMc- Camnion Bros., agents. 12. The Jones Paving Block, Zanesville, Ohio, L. H. McCammon Bros., agents. 13. The Ohio Paving Co. (Halhvood Block), Columbus, Ohio. 14. The John Porter Co., IsTew Cumberland, W. Ya. 15. The l^ew York Paving Brick Co., Syracuse, K. Y. 16. Hallwood Block Granite Brick, manufactured by Tennessee Paving Brick Co., Bobbins, Tenn. In this report the varieties are represented by the numbers above given, and the separate specimens by letters. Of each variety, except 'Nos. 1 and 16, ten bricks or blocks were used in making the various tests. A number always indicates the same variety, but only when the number and letter are the same, does it mean the same brick. Thus ISTo. 1 always means a granite block, yet IsTo. 1 A and No. 1 E are differ- ent blocks, but both Georgia granite. It was deemed advisable to ascertain, first, the essential chemical ingredients; second, the ratio of absorption ; third, crushing strength; fourth, transverse strength; fifth, the re- sistance to abrasion and impact. The Riehle testing ma- chine of Messrs. Otten & Westenhofl, appearing to be the most readily available, these gentlemen were employed, not only to make the crushing and transverse tests, but also to BRICK FOR STREET PAVEMENTS. < make the chemical analysis and determine the specific grav- ity and ratio of absorption of the cubes which were pre- pared for the crushing test. How THE Specimens were Prepared. The testing of a single specimen of any kind being deemed insufficient, it was determined that three cubes of each variety be prepared for ascertaining the crushing strength. Accordingly three bricks or blocks of each va- riety were taken at random, and sent to the marble works of Joseph Foster & Sons, placed in the mill and sawed in tw^o lengthwise, the cut being made so as to leave one piece about 2J inches in width. This piece was then cut by the saws trans- versely, so as to approximate as nearly as practicable to a 2-inch cube from the interior of the brick. The roughly sawn cubes were then placed upon a rubbing bed and worn down to the required size, with parallel and equal faces. Three such cubes were made of each variety. Of the gran- ite, A and B were made from one block; C from another, dumber 16, the three cubes were made from a single block, as of this number but three blocks were furnished. In making ITo. 15, which is of a very refractory material, the saw was unfortunately deflected in such a manner that •cubes could not be obtained from two of the pieces, B and C, and they were rubbed down to two inches square by IJ inches high. Subsequent developments show that it would have been advisable to have made IJ inch cubes instead of 2 inch. The testing machine used has a capacity of 52,000 pounds. Tt was thought that very few, if any, of the specimens would show an ultimate crushing strength exceeding 13,000 pounds per square inch, but in this we were mistaken. By the same process above described, four " granite 8 BRICK FOR STREET PAVEMENTS. bricks" were manufactured; that is, four pieces of granite 2Jx4x8 inches were made, to be subjected to the same tests- as the bricks, in order to compare the resistance of the chiy products with a standard paving material. Tt will be ob- served that great care was taken in this work m order to preserve the material of each specimen intact and to pre- vent injury to it in any way. No cutting with chisels or spalling was permitted. Each specimen was numbered and lettered and its identity preserved throughout the entire series of tests. The cubes were used for three purposes : First, for obtaining the ratio of absorption ; second, specific gravity, and third, the crushing strength of the material. Another absorption test was made with whole bricks, and in some instances the percentages obtained differed materi- ally. There are two reasons for these differences : A single cube only was used and it was immersed but twelve hours. For some of this material probably this length of time was too short for it to absorb all the water that it would ulti- mately take up, but generally the percentages obtained by immersing the cubes was materially higher than that ob- tained from the whole bricks, which is a result to be ex- pected when it is remembered that the outer portions of the bricks were in several cases salt-glazed and were gener- ally more dense and burned harder than the interior portion from which the cubes were obtained. The specimens sub- jected to crushing were lettered A, B, C, those lettered A being used for the absorption as well as the crushing test. ^o essential preparation of the specimens for the re- maining tests was necessary, They were all kept in a steam- heated room from the time of their arrival until used, which was about one week for the latest arrivals, and about four weeks for the earliest. All would be classed as perfectly dry. All adhering sand or dust was carefully brushed from BRICK FOR STREET PAVEMENTS. 9 tliose tested for absorption or abrasion before weighing them. In selecting those used for ascertaining the transverse strength, perfect specimens, showing no fire cracks or other defects, were taken. In fact the manufacturers or agents had generall}^ done the selecting and packing with such care that no outside defects were visible, except as noted for No. 10. Description of Specimens Submitted. No. 1. Application was made to the Southern Granite Company for specimens of their material, but none was re- ceived, accordingly the samples used were obtained from Mr. John Regan, contractor, who was using Lithonia granite in paving a street, and the cubes and specimen bricks were sawed from the interior of the blocks, rubbed down, with- out the use of hammer or chisel, to the dimensions given as above noted, in the preparation of the specimens. No. 2 is a hard burned brick manufactured from plastic clay and burned in the ordinary clamp kiln. It is about 2J''x3f"x8'', and if closely laid, about sixty-iive of them would pave a square yard. Its record can be traced through the various tests in the following tables by its number. Its history as a street paver is said to be quite satisfactory in some localities, but it should not be used where the traffic is very considerable. No. 3 is manufactured from a shale or plastic clay which readily vitrifies. In size it averages 2J"x3f^^x8'', and about sixty- eight will be required for each square yard of pave- ment. The chemical analysis, as given in table No. 1, does not show that it contains an objectionable amount of lime, but other tests unmistakably manifest its presence in form and quantity to a highly detrimental degree. The brick is very hard and dense, ranking third in specific gravity, but it is rather small and quite brittle, the fracture being con- 10 BRICK FOR STREET PAVEMENTS. choidal, and it will yield to the trituration of animals' shoes rather than the grinding of the wheels of vehicles. I have no knowledge of its record in actual service as a street paver. IN'o. 4 is what is known as a lire-clay brick. In color it is an orange buff. The average size is 2J''x4J''x8J^'. About tifty-nine would lay a square yard of pavement. It absorbs water rather freely, but not to a greater extent than many acceptable building stones, and in all the other tests its stand- ing is good. Nos. 5 and 6 are practically the same brick, manufac- tured from a shale or indurated clay. In color they are a dark red. They average 2J''x4i"x8f'', and about fifty-nine of them will pave a square yard. The samples tested are all burned quite hard, but not in all cases to vitrification ; hence while they show great transverse strength, and resist abra- sion well, they are comparatively low in crushing strength and there is great variation in the percentage of absorption. Their record in actual use is quite satisfactory, but I have no statistics of the severity of the traffic to which they have been subjected. No. 7 is of a dark red color, 2J''x3f"x7}'' in size. About sixty-nine will be required for each square yard of pave- ment. In all the tests this ranks among the best of the red bricks, and its record under moderate traffic is good. An increase in size so as to afford a greater weight of pavement would appear to be prudent if it is to be used under heavy traffic. ^o. 8 is a fire-clay brick of a light buff color, 2^q''k 3||.''x8^V'' ^^ which about fifty-five will pave a square yard. The material of which it is composed has not been very finely ground nor very thoroughly compressed. As a con- sequence it has a low specific gravity, a moderately high rate BRICK FOR STREET PAVEMENTS. 11 of absorption, and is outranked by several other varieties in the other tests, but in the uniform quality of each individual brick as compared w^ith the others of its kind, it stands at the head of the list. ^o. 9. In chemical constituents this coincides more nearly with No. 2 than any of the other samples submitted, yet the treatment of the material has been so different that the results are in no respect similar. It is a glazed Hall- ^vood block, 2^''x3|''x8j'', and about fifty-five of them will lay a square yard of pavement. The glaze is said to be a natural, and not a salt glaze. The corners are rounded to about one-half inch radius, and two J" groves extend length- wise around the block near its middle. The clay has been finely ground and completely vitrified, but inasmuch as it contracts greatly in burning, the blocks are liable to show cracks on the outside or cavities on the inside. When broken the blocks show an even dense texture of a dark brown color, and, were the defect above noted remedied (which it would appear to the writer, could be readily done), they would be greatly improved for street paving purposes. No. 10 had been assorted to some extent when they came into my hands, as more than one-fourth of the bricks had been broken in the box. The average size ^s 2^-^'^x4^'xS^^^^y and fifty-eight of them will lay a square yard of pavement. They are dark brown in color, with corners rounded to -about one-fourth of an inch radius; burned exceedingly hard, although they do not present the melted appearance of most of the vitrified bricks. While this brick has great hardness, with sufficient density for all practical purposes, and even a high degree of tenacity under a steadily applied stress, yet it possesses great brittleness, and when subjected to shocks, shows a tendency to spall badly. Could the qual- ity of toughness be given it without materially diminishing 12 BRICK FOR STREET PAVEMENTS. its liardiiess, no essential of a desirable brick paver w^ould be lacking. Ko. 11 is manufactured from a clay found in the coal measures but not termed a Hre-clay. It is a salt-glazed block 2|"x4''x9J'' in size, and each square yard of pavement will require about forty-eight blocks. The corners are slightly rounded. Little fault can be found w^ith the chem- ical ingredients, although an additional amount of iron would be in better proportion to the quantity of alkalies present. The form and size of block has been well chosen. if such a thickness can be properly burned, but the mechan- ical work of preparing the material and forming the block has been inditferently done and the burning decidedly un- derdone. Xo. 12, is of well chosen dimensions, being 2f''x4J''x9",. and Hfty-one blocks will lay a square yard of pavement. The material of which it is composed is about the same as that of which JSTo. 10 is made, namely, a mixture of shale and clays found in the coal measures. The corners are rounded to about one-fourth of an inch radius. The blocks are re- pressed, with live grooves passing transversely nearly across one side, and eight diagonally nearly across the other. The sand, or possibly the oil, used in repressing, serves to give it a reddish brown color. Giving the block a form such that it should always be placed with the same side up ap- pears to be a relinenient hardly required in practice. The material might have been made into a good paving block, but it was not. The clays were not ground sufhciently fine^ neither was the burning carried to such an extent as to pro- duce a block that would withstand the abrasion of street trafhc. The samples tested were obtained from an agent, and not directly from the manufacturers. No. 18, is salt-glazed, corners rounded to about one-half BRICK FOR STREET PAVEMENTS. 13 inch radius, with two grooves ahout one and one-half inches apart, passing lengthwise around it near the middle. Ahout forty-six blocks will pave one square yard. It shows a higher percentage of iron than any other specimen analyzed, but appears to be mainly composed of a plastic clay, possi- bly indurated, Avhich has been finely ground and skillfully combined. In the process of burning or vitrification, the iron and alkalies have combined so as to render the material practically impervious to moisture, but it has not quite as high a specific gravity nor the strength that should be obtained with this material. Its record in practical use is very good, and under any thing like fair treatment will give satisfactory results. 1^0. 14, is a repressed fire-clay brick, wnth corners rounded to about three-sixteenths of an inch radius. The average size is 2J''x4J''x8J'', and sixty of them will pave a square yard. The material is very similar to ]^o. 4, but the repressing has given it advantages in some particulars. It is of a buff color. It has been used as extensively for street paving as any other variety tested, and under mod- erate trafiic its record has been satisfactory. A result ap- pears to be attainable with this material which is not al- ways secured, but when it is, leaves but slight room for ap- parent improvement in the manufacture of paving blocks. It is obtained by the fusion of the iron with the silica when acted upon by the alkalies or other fluxes, in the pro- cess of burning or vitrification, producing a block, which, when broken, presents a gray metallic or granitic texture, showing no traces of cleavage or granular structure, and perfectly uniform throughout. Of the sample bricks of this variety tested, about seventy-five per cent were completely vitrified as here described, while the others presented a granular appearance, either throughout or in the central por- 14 ' BRICK FOR STREET PAVEMENTS. tion, but they were all very hard burned. The cube used for obtaining specific gravity and percentage of absorption was but partially fused, hence it shows great affinity for moisture. This fusion does not appear to add materially ta .the strength, but it does lessen the amount of absorption without materially increasing the brittleness. -N'o. 15, is drab or brown in color, 2J''x3Yyx7|'' in size, requiring about seventy-five of them to lay a square 3'ard of pavement. The clay from which this brick is made is evidently largely formed from the disintegration of lime- stone rocks. All the samples were thoroughly vitrified, and the product is an exceedingly refractory substance. Could the lime be eliminated from it before burning, the bricks- would be as nearly indestructible as could be desired, but every brick tested manifested the presence of lime in quan- tity sufficient to impair its durability. J^o. 16, is made from a shale or clay found in the coal measures, although not described as a fire clay. But three of these blocks were obtained for making the tests, and each was quite a perfect specimen of its kind. This is a Hallwood block, corresponding in dimensions with E'o. 13^ and if the samples fairly represent the product of the kilns, pavements properly laid with this material will be both dura- ble and satisfactory. How THE Tests Were Made. Absorption. — Of the cubes prepared as before described, the one lettered "A" of each variety was placed in a drying oven and maintained at a temperature of 212° Fahrenheit for twelve hours, in order to drive off any contained mois- ture. Each was then accurately weighed. The figures ob- tained are found in the second column from the left of Table Xo. 2. It was then immersed in water, where it re- BRICK FOR STREET PAVEMENTS. 15 mained for the succeeding twelve hours, when it was taken out, the adhering moisture wiped off, and again weighed, the results being noted in the third column from the left in the same table. At this time it was also weighed in water, these last weights being found in the sixth cohimn of Table No. 2. For a further test of absorption two whole bricks of each variety (except as noted in the table) were selected at ran- dom, lettered G and H respectively, placed on an ordinary counter scale weighing to quarter ounces, the results noted, and are found in the ninth column from the left in table No. 2. They were then placed in water and kept entirely submerged for seventy hours, wdien they were taken out, dried with a towel, again weighed, with results found in the tenth column of the same table. These results are only as accurate as the scales were, but the test can be readily re- peated at any time, and will give a fair practical measure of the absorption to be expected from whole bricks in a sim- ilar length of time. The samples had been kept in a steam- heated room during the preceding ten days, and the dust and sand were carefully brushed from them before the first w^eighing. Cnishing Strength. — For determining the crushing strength tlie cubes were carefully measured, their upper and lower surfaces protected by a thickness of blotting paper, and they were subjected to pressure in a Riehle Testing Ma- chine of 52,000 pounds capacity. The results obtained will be found in table No. 3. No visible effect was produced upon the granite except that " B" was very slightly spalled, as noted. No. 15 " C," which was about one and one-half by two inches, was set on edge after being tried the other way, and a pressure exerted exceeding 17,000 pounds per 16 • BRICK FOR STREET PAVEMENTS. square inch, but it could not be crushed, althougli it spalled at one corner at a little over 7,000 pounds per square inch. Transverse Strength. — The transverse strength was as- certained in the same machine in the following manner : Three bricks of each variety (except as noted) were chosen and lettered D, E and F. The lower knife edges were ad- justed at precisely six inches apart, the upper knife edge being placed centrally between them. Each specimen was carefully measured and its surface protected from direct abrasion at the points of bearing by two or three thick- nesses of blotting-paper, and the weight required to break it carefully noted. These results are found in table Xo. 4. Abrasion and Impact. The method adopted for determining the relative re- sistance to abrasion and impact was that whicli is com- monly known as the rattling test. A cylinder about six feet in leno^th bv twentv-eis^ht inches in diameter, contain- ing pieces of cast iron, varying in weight from one to six or eight pounds, and in the condition in which it is ordina- rily used for cleaning castings, was selected for this purpose. Four bricks of each variety (with the exceptions noted in the table) were selected and lettered G, H, I and J, two of the specimens, G and H, having been soaked for the preceding seventy hours. The specimens were carefully weighed and all placed in the rattler at one time. Billets of wood were put in with them, as is ordinarily done in cleaning cast- ings, to prevent breaking. The cylinder was revolved at a speed of about twenty-four revolutions per minute, and at the end of one thousand revolutions was stopped, the speci- mens taken out, weighed and the loss of each noted. The object of making this :^rst test in this particular manner was to wear away the sharp angles or corners and bring BRICK FOR STREET PAVEMENTS. 17 each piece as nearly as practicable on a level footing with its fellow for that which was to follow. This first test, therefore, was intended more to equalize the several pieces than to measure their actual wear. On the following day the specimens were again placed in the cleaner, omitting the protecting billets of wood. The object now being to observe the survival of the fittest. The cylinder was given three thousand revolutions, occupy- ing something over two hours in time, and although all the pieces were in at the same time, excepting a fragment of J^o. 15 " I," which had broken ofiT in the former test and was in- advertently omitted ; there was ample room for motion and the loss in weight of every piece was a measurable quantity. The individuality of some specimens was lost, as the marks were in some cases almost entirely worn away, but there was no trouble in identifying the varieties ; hence, in tabulating the results of this work the percentage of loss in the sec- ond rattler test is given for each variety. This will be found in detail in table 'No. 5. With the completion of the second rattler test closed the actual work upon the specimens, and the labor of col- lating the information obtained was commenced. Further investigation would appear to be desirable, especially some test that will more nearly resemble the attrition of the shoes of animals in passing over the pavement than do any of the tests that were made. But the information now gained would appear to justify seeking that knowledge by a prac- tical test of the brick in the street pavement itself. 2 18 BRICK FOR STREET PAVEMENTS. TABLE No. 1.— Chemical Analyses. < < c4 s % 1 < < II 2 73.32 14.82 8.34 0.70 0.99 2.26 100.43 3 64.37 19.73 9.07 0.82 2.32 1.89 1.80 100.00 4 67.36 22.05 5.61 0.86 0.36 2.70 1.06 100.00 5 67.65 18.36 8.34 0.80 1.02 2.58 1.25 100.00 6 68.12 18.63 8.53 0.68 0.71 2.58 0.75 100.00 7 68.69 17.95 7.25 0.76 1.47 2.83 1.05 100.00 8 64.08 25.32 5.44 0.30 0.29 0.63 3.94 100.00 9 71.57 17.06 8.34 0.50 0.58 0.56 1.39 100.00 10 61.80 20.76 8.70 1.38 1.09 1.44 4.83 100.00 11 77.67 14.77 3.63 0.38 0.27 2.43 0.85 100.00 12 65.08 22.39 7.97 0.62 0.74 2.33 0.87 100.00 13 66.30 18.62 9.78 0.40 0.84 1.89 2.17 100.00 14 69.02 22.07 4.53 1.70 0.38 1.34 0.96 . 100.00 15 67.67 11.67 6.53 12.74 0.95 0.80 100.36 16 70.57 15.19 7.97 0.78 0.32 1.15 4.02 100.00 Undertermined is water manganese oxide and possibly some titanic acid. OTTEN & WESTENHOFF, Chemists. 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TABLE No. 3.— Crushing Strength. i SIZE IN INC. z5 . per D". 2 A 1 97 1.97 1.94 3 82 29600 7749 35500 9293 Soaked 12 hours. 2 B 1.94 1 94 1.94 3.76 28000 7447 35920 9553 2 C 1.94 1.97 1.94 3 82 Did not spall at 52000 lbs. = per D". 13613 lbs. 3 A 1.97 1.97 1.97 3.88 32290 8322 37720 9722 Soaked 12 hours. 3 B I 94 1 97 1 94 3,82 15200 3979 ■48000 12565 3 C 1 97 1.94 1.94 3.76 18100 4813 32720 8702 4 A 1.97 1.97 1.97 S 88 33110 8533 43120 11113 Soaked 12 hours. 4 B 1,97 1 97 1 97 3,88 36590 9427 Did not crush at 52000 lbs. = perQ". 13402 lbs. 4 c 1.97 1.97 1 97 3,88 Did not spall at 52000 lbs. = per D". 13402 lbs. 5 A 1.94 1.97 1.94 3 82 50000 13089 Soaked 12 hours. Did not 52000 lbs. = 13613 lbs. per Q crush at 5 B 1 97 1.97 1.97 3,88 3S8oO 10013 391.50 10090 5 C 1 97 1.97 1 97 3.88 28000 7216 38850 10(113 6 A 1.94 1 91 1 91 3 6.i 19650 5383 23100 6329 Soaked 12 hours. 6 B 1.94 1 94 1 91 3.70 37220 10059 51500 13919 6 C 1.97 2.00 1.97 3 94 Did not spall at 52000 lbs. = perD". 13198 lbs. 7 A 2.00 1.97 1.97 3.88 25120 6471 51600 13300 Soaked 12 hours. 7 B 1.97 1,97 1.97 3.88 . Did not spall at 52000 lbs. = per D'^ 13402 lb.s. 7 C 1.97 1 97 1 97 3.88 38550 9935 52000 13402 8 A 1 97 1.97 1 94 3.82 34000 8900 46460 12162 Soaked 12 hours. 8 B 1 97 1.97 1.94 3.82 25220 6602 446.50 11688 8 C 1.97 1.97 1.97 3.88 25030 6451 39570 10198 9 A 1.97 1.97 1 94 3 82 24000 6283 39820 10424 Soaked 12 hours. 9 B 1 97 2.12 1.97 4.18 26000 6220 48270 11.548 9 C 2.00 1 97 1.94 3.82 17500 4581 39820 10424 10 A 1.97 1 97 1.97 3.88 50750 13080 Soaked 12 hours. Did not 52000 lbs. = 13402 lbs. per D crush at 10 B 1 97 1.97 1 97 3.88 35500 9149 51460 13263 10 C 1 97 1.97 1.94 3 82 32000 8377 50050 1.3102 11 A 1.97 1,97 197 3.88 27900 7191 50300 12964 Soaked 12 hours. 11 B 1 97 1.97 1.94 3 82 24000 6283 39400 10314 n C 1.97 1.97 1.97 3.88 23880 6155 27250 7023 12 A 1.97 1.94 1.94 3 76 19700 5239 37330 9928 Soaked 12 hours. 12 B 1 97 1.97 1.97 3.88 14240 3670 17620 4541 12 C 2.00 1.97 1 94 3.82 10960 2869 28110 7359 13 A 1.91 1 97 1 97 3 88 28000 7216 48000 12371 Soaked 12 hours. 13 B 1.97 1 97 1 97 3.88 40000 10309 46600 12010 13 C 1 94 1.97 I 91 3.76 1'.I500 5186 3S380 10207 14 A 1 97 1.97 1.97 3.8- 38800 10000 50770 13085 Soaked 12 hours. 14 B 1 97 1.97 1.97 3.88 Did not spall at 52000 lbs. = per D". 13402 lbs. 14 C 1.97 1 97 1 94 3.82 Did not spall at 52000 lbs. = per D"- Soaked 12 hours. Did not 13613 lbs. 15 A 1 97 1 97 1,97 3.8S 27770 7157 crush at 52000 lbs. = 13402 lbs per n " 15 B 1 50 1 97 1,97 3 88 Did not spall at 52000 lbs. = per D". 13402 lbs. 15 C 1.50 2.03 1.94 3 94 Did not spall at 52000 lbs. = 13198 lbs. per D". 15 C 1 94 2 03 1.50 3.04 a5400 11644 Did not crush at 52000 lbs, = ner n". 17105 lbs. 16 A 2. 2. 2. 4 00 51660 12915 Soaked 12 hoiars. Did not crush at 52000 lbs. = 13000 lbs. per D". 16 B 2. 1.97 I 97 3.88 Did not spall at 52000 lbs. = per D". 13402 lbs. 16 C 2. 2. 2. 4 00 Did not spall at 52000 lbs. = per Q". 13000 lbs. BRICK FOR STREET PAVEMENTS. 21 TABLE No. 4. — Transverse Strength. SIZE IN INCHES. " . CO < ?;; H z " s 2 "* " H K S^ O « "^ -E-a «5:z ^2§ ^ W q; M^ O aj R 6590 1501 4580 1222 G500 1801 5050 1310 5G20 1811 7G00 2377 5400 1932 11680 2472 8000 1693 11110 2427 l:«20 3089 lllfiO 2511 15171. 3288 12460 2657 10870 2329 12000 2496 7020 2292 10250 3525 7840 2650 8320 1959 7850 1820 1 8000 1811 8730 2093 7410 1776 4790 1148 9690 236r> 8000 1948 11610 2584 6780 1346 6000 1197 5100 1043 8000 1668 9010 1811 7770 1518 9760 1850 7830 1483 7640 1630 11660 2527 12710 2667 9640 2091 5750 1982 8000 2853 5530 1972 7150 1664 2.25 2.31 2.31 2 31 2 125 2.19 2.125 2.50 2.50 2.50 2 50 2.50 2 44 2.56 2.625 2.625 2 25 2 31 2.25 2 50 2.50 2,56 2 50 2.50 2.50 2 375 2 31 2.375 2.75 2.81 2.75 2.62 2 55 2.55 3 00 3.06 3.00 2.44 2.375 2.375 2.06 2.06 2.06 2.75 4.19 3 82 3.75 3.875 3 625 3.625 3 44 4.125 4 125 4,06 3 94 4,00 4 125 4 06 4.00 4 06 3 50 3,625 3 44 3,94 3 94 3 94 3,875 3.875 3,875 3.94 4.00 4 125 4 25 3 87j 3 94 3 75 4,12j 4,25 4.18 3.56 3 50 3.50 3.75 6.0 6.0 6.0 6.0 6 6,0 6.0 6 6,0 6,0 6 6,0 6.0 6 6 6 6.0 6.0 6 6 6 6.0 6,0 6 6 6,0 6,0 6 6,0 6 6.0 6,0 6 6,0 6 6 6 6,0 6,0 6 6,0 6,0 6 6.0 9 43 8 82 8 66 8 95 7 70 7 94 7,31 10 31 10.31 10 15 9 85 10.00 I 10 06 I 10 39 I 10 50 10 66 7 875 8,37 7.74 9.85 9.85 10. 08 9.69 9. 36 9.24 9.79 11.17 11 . 24 11.00 10,64 10 68 10,83 11.62 12.06 11.25 10.06 10,09 9 93 7.33 7 21 7,21 10 31 R ■ 1444 2040 -2197 2963 -2494 -2822 1863 1672 -2299 1195 ■1666 1688 -2428 -2269 Only one specimen broken. Broke at one of the lower knife edges. Round corners, grooved longitudinally. Round corners. Round corners. Round corners, grooved transversely. Round corners, grooved longitudinally. Round corners. Only one specimen. Round corners, grooved longitudinally. For numbers 9, 10, 11, 12, 13, 14, and 16, the dimensions are those of the estimated equivalent rectangular seetious. 22 BHICK FOH STREET PANEMENT8. O REMARKS. Soaked 70 hours. Soaked 70 hours. Soaked 70 hours. Broke and fragments lost. Soaked 70 hours. Soaked 70 hours. Soaked 70 hours. Soaked 70 hours. Soaked 70 hours. 5.17 26.59 25 37 10 27 11.24 10.89 14.12 17.28 4.70 23 93 24.14 9 42 10.05 9 80 13 ,01 16 31 PER CENT LOST IN ST TEST 000'^-..= '-l'M-Mi-(MOr-iOO^.-IO'--^i-,0^'— Or-lf-— lr-!rtr-lO TOTAL LOSS IN OUNCES. 6 5 25 6 75 30 75 35 50 10 75 14 25 25 10.75 5.50 48 75 15 9.75 10 50 11.25 13 75 12.75 13 11 75 1{ 75 11 50 10.75 12 75 10 50 10.75 13 25 9 25. 17 25 18.0 19 25 16.50 LOSS IN 2d TEST. ;:5o^^l:2l«ggogl2oSS^ooi-:''e^SSS.^'c;5oSoL2ol5oS IC-O O O C5 -O C<1 CC. 05 CO CC CO C3 O O o O H Ood-:t..0^r-irlr-.^0.-IOO^.-^r-l,-IWrH,-lr-0 r.^ V^ ^ ._ ^ ^ „ WEIGHT AT END OF 1st TEST ORIGINAL WEIGHT IN OUNCES. 116,75 115.0 116 94 25 90 87.75 87.75 92 25 91.50 85 80 118 113.75 113 75 112 114 110 114 112.0 109 75 114 112 50 112 25 87 75 88 50 88 25 87 75 103 50 103 25 101 50 102 50 •Haxxai wfr! -M ri CO CO CO CO "* >* ■* TT lO >^ O l-O -O O :» O l^ t- t- r- 00 CO OC OO BRICK FOR STREET PAVEMENTS'. 23 >^ . o 1 s s t. ^ T* SJ a be > 3 r/- 2 o £ a ^ i O 3=0 ■ g oS o ^50 go go g C -5 . o - Si - "^ - ^H t-lnt-i Ql ^ >-? 'O-C'ac^'c «'C .-a.-oflp. <1> - - oCt^^fc-Oo^O^O^ c^^ j M ^P3 ro J^aq (» pq;?; r^ J?; ^ ;^. M ;?; ;» pq O 1 iH ^ — , ^Tf ST-^ o"-^ «-. -rf. t- f-,-- 1^ CiO •^ .-1 ^10 c-i Ol \ %ll 00 c^ CO CO •>\T-i "C; irr TTi 00 £i^ £L"^ (N ^ ^ ^ ^ E-" ',■• 1 ^ti cS'o §^ i'f-^ 2 r^ ^ ■:^ E^ ■M 'M ^0 'O -^ 5C OS --■zt .-iCO 00 .-i |2S l-HrH -Mr-, -M T-( IM I-t ,-( E>=g ^ ,v ,. ^ ^ ,. ^ 1 ^' ^' ^ ^' ^' ^ Sis c~.l-O.COl-l^.O!(< r)< i^r^ 1 9q ^^^■,^_ t-lr-liO I^'Mi-liHCMMCOC0i-li-n-(*Ji-lr-i r-l r-( — , r— , ift; i-O i- .C i^ lO iC "O >C iC i.t 10 lO lO 10 iC iC lO oii^o o i-ir^Ol-C^liO l- .0 0(MOC^l-~uo.Ql-i — -^j-jooomoi^i-^ocbo 5s lO o o lOiC lO lO uo loooo \rt Oi;t 'ftoioiOic>oo"oLOuo _ w oi^^s >o t^l-O I- C-I C^l l-urju-5uOOiCl-Ol^l-l^l-!Nl-iMl-Si-Ol-l- M =^ i-lrHO O OOtH d M r-( OOrHi-lr-lr-IOr-lOOOOOOr-lOCOM'oO ss 0-1 IGHT END OP TEST . O iC o ifto uo 10 OiT. >-r>- .oiooi — . LOOI-I ift C^iCO 1^ t^ COOOiCi^=:i-l-OOir:Ot^C<1.00000 J-ii^l- o oo~. Tt< i;? CO 01 i-ooc'^ T — — ~i rt ri i~ := ■O'MiOiOCO'^r^.-i ooo o 000 CI ^ onMC-1 01 ri Ti :t c- :-: rt ooooi^i--..-:-i-i-(M _ 1 2 aa: o o.c.^ iC >.0! ^ ^ iCO OOO.T iT.COi-.Oi- lOOOiT 1(0 lO m i^ i^ o cj t- I- lO 'C in. >;5 CM I- 1^ .ft t- I- c^ c^j ic lo m lO 1^ 1^ °M°. o S2S 8 ^. 5 {:5?ifl!^S?,?g?2S?^S'a'a8SS S I^?5 1 •tiaxxai ^WHUH ^ ■Z^^ ^ C3 ^ -^'-^OS^^->5S"^^-H^^OK ^ "^ •HaawnK C-. Si -. C-. 000 ^ — ^»- 12 9 1 16 3 7 5-10 & 15 12 9 11 4&6 2 14 13 BRICK FOR STREET PAVEMENTS. 9r. TABLE No. 7~Loss of Brick tn Terms of Granite. Specimen Num- First Rattler Second Rattler Entire Rattler ber, Test. Test. Test. 1 1.0 1.0 1.0 2 8.1 5.0 5.1 3 3.8 5.1 4.9 4 1.9 2.0 2.0 5 3.0 2.1 2.2 6 2.0 2.1 2.1 7 3.0 2.7 2.7 8 2.6 3.4 3.3 9 2.0 3.8 3.7 10 1.7 4.8 4.5 11 2.1 4.6 4.3 12 2.5 5.3 5.0 13 1.4 3.1 2.9 14 1.4 ■ 2.2 2.1 15 20.0 1.4 2.9 16 K4 2.0 2.0 26 BRICK FOR STREET PAVEMENTS.. W < < o O H Qh >0 -X) CO ^ 5< -* rt< Tf V. o O O ^: t^ p^ Tf O lO ^ ^ CO (M r-l ±^ C^ cc o 5^ O-i Eh 13 H << --0 o o c ^ !>. lO -^ < o t^ '■ CO O CO ^ 'a -^ o s o ^ tc " w c (^ CO LO --^1 Ci CC oq CO O OO OO 13 o- OO CO O rt lO O o < c d o-i 1- d ,- o- CM CO' -*' d d- 3 o ! cj CO j5 t- r— 1 -* Oi OO : ^ l^ d d d ^ »o CO [ d d o <5 ^ -t I- C^J ^ cc f- c O O ^ O CO W c -^ -t i*^ GO lC CC Ci tH lO '^l .o J3 d T- 't d r- c ,- GO -* c o d HH ^ ;^* -t ^ Cv t^ cc c- r— 1 o c »o t^ i9 o: a c CC (^ lO c o CO lO c C5 1^ -c CO o J cc l(- X lit o- -,- O- l^ t-- cc IT lO ^ I-- t^ iC :c cc »r: cc !>■ 1^ o kO t^ cc cc X " ! > ~» Cv c -tJ c f^ X :^ 1 2 c . M 1l O c is 1 ^ a ■^ _ " 1 J > ^ 1 PC C c ci 1—1 ■ " s 'bD c 1 ^ i 1 1 C a c a PC £ c .S g 1 (X g -^ 1 a .5: > o ^ ^ ^ b s -r- f5 1 oc 4j 6 1 :3 o i— ( =; K* ^ t— >— ><^ 1— I X t— 1 1— 1 1—1 , > K^i X M 1 brick for street pavements. 27 Description of the Tables. Table IN'o. 1 requires but little description. It shows the essential cliemieal ingredients of the different varieties of bricks tested as obtained from a single analysis of each kind. Generally the sample was taken from the crushed cubes, but where we failed to crush them pieces were taken from other broken specimens, using the common mortar and pestle for pulverizing. Could a larger quantity of each variety have been ground and used in sampling, or a greater number of analyses have been made, a more accurate average determi- nation would have been obtained, but the time and expense required for such work is so great that it was deemed pru- dent to limit our investigation to the single analysis. It is evident that an inquiry into the nature of the material of which the bricks are composed is the proper basis for a study of the whole matter, and should next be followed by a scru- tiny of the methods of combination. These searches should then be followed by tests of the goods produced. Without proper clay no good result can be expected, and with suita- ble materials improperly combined failure is sure to follow. From the first cause I would cite numbers 3 and 15, as not meeting the requirements ; from the second, numbers 2, 11, and 12 are conspicuous examples. Could our analyses have been made from the clays used, we should have been working to better advantage ; but that Avas not practicable for us under the circumstances. In or- der to show that the results obtained are entitled to credence, I have compiled Table N'o. 8 from the sources named in its description, which shows that the work done has been care- fully performed. Table No. 2, is a detailed statement of the results of the investigations to determine ratios of absorption and specific gravities. The method of performing the work has been described. N"umbering the cokimns from left to right, the 28 BRICK FOR STREET PAVEMENTS. first is the specimen number ; the second is the weight in grammes of the cubes lettered "A" after being dried; the third is their weight after soaking twelve hours in water; the fourth is the excess of the third over the second, which is obviously the weight of moisture absorbed ; the fifth is the quotient (multiplied by one hundred) of the fourth di- vided by the second, or the percentage of absorption ; the. sixth is the weight of the cube in water; and the seventh is the specific gravity. This was determined by the formula : W Specific gravity :== \\v ^// In which W equals weight before immerson, W equals weight after immersion, and W equals weight in water. The remainder of the table details similar experiments witb whole bricks, using a less accurate means of determining weights, column eight giving the letters designating the mark- ing of specimens of the several numbers (it will be noted that these bricks appear again in The Rattler Test — Table ^o. 5); column nine giving the weight in ounces before inmiersion ; column ten, the weight after soaking seventy hours in wa- ter ; column eleven is the excess of ten over nine, being the weight of water absorbed ; column twelve is again the per- centage, or the quotient multiplied by one hundred of eleven divided by nine ; and column thirteen is the mean of the two results from specimens of the same number in column twelve. The latter test is not one of great accuracy, and the tabulated results can not show all of the influences which should be taken into consideration. For example, numbers three and fifteen were smooth, clean bricks when put in water, but when they were taken out their surfaces were defaced by numerous indentations caused by the dissolution of the BRICK FOR STREET PAVEMENTS. 29 contained material. This loss lessens the apparent amount of absorption, and unless provision is made for determining it in each case it can not be measured. It, however, re- veals a serious defect, Avhich should not be overlooked. Where nothing of this kind is a[)paront tlie test is a very practical one, and can be repeated at pleasure with the ordi- nary counter-scale and but little trouble. It furnishes a very fair test of the absorbing qualities of the material. Table I^o. 3 sets out in detail the results of the work done to ascertain the crushing strength of the materials tested. The method of preparing the specimens having al- ready been described, it is not considered necessary to set forth in further detail the manner of arrivins^ at the results here tabulated, as that will be evident from a mere inspec- tion of the table. A glance at the results obtained shows us that we are not dealing with the substance ordinarily known as brick. In Table E'o. 4 is given the work done to ascertain the transverse strength of the material. The Riehle testing ma- chine of Messrs. Otten & Westenhoff was used for this purpose. Three whole bricks or blocks, lettered D, E, and F, of each variety were broken, excepting numbers one and sixteen, of which but one each could conveniently be had. The bricks were supported on knife edges six inches apart, and the load w^as applied by another knife edge brought to bear midway between, and parallel to, the other two; each point of bearing being protected from direct abrasion by two or three thicknesses of blotting paper. The modulus of rupture w^as computed by the ordinary formula: 3 w I R-= 3 6 d' in which W represents the breaking w^eight in pounds, h, (/, 30 BRICK FOR STREET PAVEMENTS. and U the breadth, depth, and length, respectively, all in inches, and E, the modulus of rupture in pounds. If the span I be measured in feet, while b and d are measured in inches, the formula becomes K=18 hd' Hence, the modulus of rupture is stated by Prof. Rankine to be " Eighteen times the load required to break a bar of one inch square, separated at two points, one foot apart, and loaded in the middle between the points of support." While this is the ordinary formula used in the text-books, and identical with that adopted by Prof. Baker in his recent publication upon "• The Durability of Brick Pavements," it should not be confounded with that commonly employed for determining the transverse strength of material, which is / W 4tt d In which R represents the coefficient of transverse rupture ; W the breaking weight; a the sectional area; d the depth; I the length, all in inches. Results obtained by the latter formula will be found to be about \ of those derived from the one first stated. In the table, the first column on the left gives the speci- men numbers; the second, the letters by which they were designated; the third column is the breadth or thickness; the fourth, the vertical depth; the fifth, the length between supports, all of these dimensions being in inches. The sixth column is the product of the third by the fourth, being the area in square inches. The seventh is the weight in pounds at which the specimen was broken ; the pressure being ex- erted by the continuous working of the pump without shock BRICK FOR STREET PAVEMENTS. 31 until rupture was produced. The eighth column is the mod- ulus of rupture calculated by the formula first above given. This formula is stated in Professor Baker's pamphlet, page 5, in the following form : 2 h d^ W: 3Z The letters having the same significance as above given, but a moment's inspection shows this expression to be identical with that used in calculating the table. The ninth column shows the averages of the three results given in column eight for specimens of the same kind or number. Table 'No. 5 is a detailed statement of '' The Rattler Test," or the effort to measure the effect of abrasion and im- pact upon the specimens submitted. The method of con- ducting the test has already been briefly outlined. Tabulat- ing the result has been a tedious process, but it has been done with much care, and is believed to clearly show the re- sults obtained in such a manner that the value of the test can be judged from a correct basis. All the weights were carefully repeated, and, if errors have been made in the cal- culations, all the work is given in detail, so that corrections can be made by inquiring minds if incorrect results are found in any of the columns. Counting from the left, the first column gives the speci- men number ; the second, its letter (those marked G- and H having just come from their bath in the absorption test — Table 'No. 2) ; the third, its weight in ounces when placed in the rattler; the fourth, its weight after the first thousand revolutions, or at the end of the first test. There was an in- terval of nearly forty-eight hours between the first and sec- ond rattler tests, and the weighing was repeated before placing the specimens the second time in the cleaner, but the 32 BRICK FOR STREET PAVEMENTS. loss in weight by evaporation from the saturated bricks did not appear to be a measurable quantity by the instrument used, which was a new Fairbank counter scale, weighing to quarter ounces. The fifth column is the excess in the weights given in the third over those in the fourth, or the loss in ounces of each specimen in the first test. The sixth column gives the weight of each specimen at the end of the second or final test. In a few cases, there was uncertainty about the identity of some specimens, as the marks had been so defaced, but in all instances the varieties could readily be distinguished. Where figures are inclosed in parentheses, they include the weights of the pieces Avhich had been broken off and were of sufiicient size to be saved and weighed. The seventh column is the excess of the weights given in the fourth over those in the sixth, being the loss in the second test. The eighth is the sum of the seventh and fifth, or the difference of the third and sixth, being the total loss in both tests. The ninth is the quotient, multiplied by 100, of the fifth divided by the third, or the percentage, to the nearest tenth. The tenth column is the percentage of loss in the second test, and is obtained by dividing one hundred times the sum of the losses for specimens of the same number, taken from column seven, by the sum of the weights of specimens of that number, taken from column four. The eleventh column is calculated in the same manner, using the sum of the weights for each variety or number as given in column eight, and the sum of the weights of the same variety in column three. Table Xo. 6 is compiled from the results set out in the preceding Hve tables; the several numbers being rated with each other in the order in which they have withstood the various tests to which they have been subjected. It shows some rather unexpected results and is worthy of very care- BRICK FOR STREET PAVEMENT:?. 33 fill study. The rank is by averaging all the tests of each kind for each number or variety in each test. Thus, in the absorption tests, those numbers showing a less average per- centage of absorption are ranked higher than those showing a greater percentage. In crushing strength, those showing a higher power of resistance rank above those showing a less endurance. In this test, unfortunately, our machine had not the power to enable us to properly classify the better grades of material tested, but the rank so given is strictly in accordance with the results of the work. It is not thought that Xo. 16 is absolutely a stronger material than granite, but one of the granite cubes was slightly spalled at a lower pressure than was exerted when the Xo. 16 cube was spalled, but none of the cubes of either number were crushed, hence the actual endurance of the material remained undetermined. In transverse strength, the numbers having a greater average modulus of rupture are ranked above those having a less, which correctly classifies the material as to its tenacity under stress as it was applied in making tests, but furnishes but a poor criterion by which to judge of the quality of brittleness under percussion or shocks. Under abrasion and impact, the numbers are ranked according to the percentages of loss in the second rattler test; those suffering a less loss being ranked higher than those suffering a greater one. Table No. 7 is deduced from the percentages given in table No. 5, the loss of the granite being taken as one. The left hand column gives the specimen number; the second column its ratio of loss in the first test; the third column its ratio of loss in the second test, and the fourth column its total ratio of loss in both tests. For purposes of comparison it is recommended that the figures in the third column l)e used. It will be seen that the best bricks under the most 3 o4 BRICK FOR STREET PAVEMENTS. favorable conditions siiifer about doable the loss which the granite does. Table ^o. 8. This table has been compiled for the pur- pose of comparing the work of other investigations with that herein described. The first analysis given is a Stour- bridge iire-clay used exclusively for the manufacture of glass house pots and furnace linings. It is a coal measure clay and probably contained traces of lime and magnesia, but no mention of such ingredients is found in Mr. Wills's analysis. The second analysis by the same chemist is of a clay from a like source, but in this case he has determined the percent- age of lime contained, which is very small indeed. These clays are mined and used because of their heat resisting qualities, and are principally valuable because at white heat they do not readily vitrify, but retain their form and tex- ture. The third analysis is of a i!^ew"castle lire-clay, by Mr. Taylor, the product being less remarkable for resisting heat than wear. It is to be observed that this clay contains in- gredients which at a white heat will unite or vitrify, but would hardly be likely to become fluid or even sulKciently plastic to greatly change in form. It is quite similar to our I^os. 4, 8, and 14, except that it contains much less iron. Tlie fourth analysis, from Percy's Metallurgy, is of the Glasgow iire-clay, adapted to a variety of metallurgical uses, is an average of many determinations in which, unfortunately for our purposes, the percentage of alkalies is not given. With this exception it gives the characteristic ingredients of the coal measure fire-clays. The fifth analysis is of the white clay of the tertiary formation in Dorset, by Professor Way. It is used for the manufacture of fire-brick and could prop- erly be termed a modified fire-clay. The analysis gives the alkalies as '^ alkalies and alkaline earth," and the lime as a sulphate. This clay contracts very greatly in the process of BRICK FOR STREET PAVEMENTS. 6b drying and burning, to counteract whicli tendency it is cus- tomary to incorporate with it tine sand and ground burnt chiy. Kumber six is the Beacon Hill chxy from the Lower Bagshot Beds, which withstands the high temperatures of furnace linings without much tendency toward vitrification, but decrepitates or is worn away by passing currents. The seventh analysis is taken from a recent publication by C. P. Chase, on "Brick Pavements," and gives the composition of the clay used in the manufacture of the Hale paving brick. Mr. Chase gives the moisture at 212 degrees as 2.08, and combined water as 5.16, but does not determine the alkalies present, if any were contained in his sample. If the writer understands what is meant by the Hale paving brick, this should correspond with our 'No. 2, Mr. Chase's analysis hav- ing been made from the clay and ours from the brick, but the resemblance is not very close. The eighth analysis is copied from the same source as the preceding one. The ma- terial in its natural position more nearly resembles a fine- grained sandstone than a bed of fire-clay, but it pulverizes readily on exposure to the atmosphere, and its composition and position have given it its name. From it is manufac- tured the Hay den block, which is, in reality, a tile used for paving streets. No sample of this material was furnished for testing, but it has been used extensively as a paver, and in some localities is deservedly popular. When properly burned and annealed it presents a homogeneous, compact texture, and has great hardness without brittleness. Many persons would say that the material was " perfectly vitrified," but that expression needs specific explanation to be at all in- telligible. The ninth, tenth, and twelfth analyses are copied from the same author, who also gives the specitic gravity, crushing strength, and percentage of absorption of the bricks manufactured from these clays. While he classes them 36 BRICK FOR STREET PAVEMENTS. among " our best paving brick," he giv^es no statistics show- ing their enduring qualities in actual use. They would more nearly coincide with our No. S than any other sample tested^ although they might not resemble it in color. The writer would not regard ISTo. 10 as a very promising composition, but all of these clays can be melted or vitrified very readily so as to present a compact texture that will not absorb moist- ure in any considerable amount. The eleventh analysis is from the same author of a clay used by the American Brick and Tile Company, of Phillipsburg, New Jersey. This com- position is also said to contain sulphur 0.89, and phosphoric acid 0.13. No further information is given regarding the ]>roduct except that the crushing strength averages from V,000 to 7,500 pounds per square inch. The thirteenth and fourteenth analyses Avere made by Otto Wuth, of Pittsburg, the first being of the Porter fire-brick and the second of the ground clay from which such bricks are manufactured. These compositions, it will be noticed, are quite similar, ex- cept that the brick has had the moisture driven ofl:' in burn- ing. They closely resemble our No. 14, except that we find a much higher percentage of the alkalies, and herein lies the marked distinction between the fire-clay brick, w^hich is suitable for furnace lining, and the one adapted to use in iitreet paving. The Chemfstry of Brick Manufacttjring. The alkalies of potash in the clays is a residuum of de- cayed organic matter. It is an active fluxing agent, and in the process of burning, or so-called vitrification, causes an amalgamation of the iron and silica components w^hich imparts a metallic tone or ring to the brick when struck. When aided by finely pulverized lime or magnesia m the presence of a large percentage of iron, a pale double silicate of lime BRICK FOR STREET PAVEMENTS. 37 and iron is formed, imparting a butt' tint to cla^^s that would otherwise burn red. Ln the tire-clays less than half of one per cent of potash or alkali produces no noticeable result, and the product has good heat resisting qualities, but when from one to three per cent of this ingredient is found in the clay and it contains from four to eight per cent of iron, which it generally does, with perceptible quantities of lime and mag- nesia at a high temperature (usuall}^ a white heat), these flux- ing components form vitreous combinations with the silica, producing a brick quite useless for resisting heat, but when the texture is uniform throughout, and it is allowed to cool gradually, without coming in contact with cold air until be- low the temperature ot" boiling water; or, in other words, is properly annealed, you have the so-called vitrified brick, which absorbs about two per cent or less of moisture, and has great strength to resist crushing or abrasion. This product may be used quite fearlessly for street paving. With the plastic clays or shales the melting or vitrifica- tion occurs at a lower temperature, and, owing to the fact that the ingredients are seldom uniformly mingled, there is greater danger of melting the bricks together in the kiln, or of leaving many of them without vitrification. To render them apparentl}' impervious to moisture, many manufactur- ers have adopted the plan of glazing them with salt, which may be beneficial in some respects, but is objectionable in others. These clays usually contract to a greater extent in the process of drying and burning than the fire-clays do, and hence are more liable to be warped from their proper form, or show injurious fire cracks. But no clay can be made into a good street paving brick, unless the process of firing or burning be continuously progressive and compara- tively slow to the maximum temperature, and the cooling down be gradual and continuous. This can not be done in 38 BlUCK FOR STREET PAVEMENTS. the ordinary clamp-kiln. A broken brick showing varieties of texture or color is a certain indication of defective com- bination or burning, and the fault is fully as liable to be in the burning as elsewhere. Uniformity in the product of the kiln is a necessary condition to the successful manufacture of clay of any kind into proper form to be used for street paving; and only with such clays, and such appliances as will enable the manufacturer to attain this result, can he reasonably hope to achieve success. Discussion of the Tests. With the information now before us, what brick shall be selected? If the tests were of uniform value the numbers should range in horizontal lines across Table J^o. 6, the best material at the top and the poorest at the bottom ; but we do not obtain such results. There are other considerations that can not appear in the tables, ^earl}^ 50,000 square yards of surface are to be paved, and the availability must be consid- ered. That which can be promptly furnished in large quantities should be chosen, even though an article may be inanufactui'ed which is better in some respects, but unattain- able without great delay. But people wdiose ojDinions are entitled to great respect will honestly differ as to the relative value of the several tests. For example. Prof. Baker, in his pamphlet on " Brick Pavements," expresses the opinion de- cidedly that, "As a test of the quality of brick or stone, the crushing strength is practically Avorthless." (Baker on Brick Pavements, p. 8.) He demonstrates in a concise manner that the weight on the wheel of a loaded vehicle is not likelj^ to crush a brick, even though it be soft. Yet the jirofession gen- erally have considered, and probably will continue to regard it as essential, that the constructing engineer should be informed as to the crushing strength of the materials which he uses, BRICK FOR STREET PAVEMENTS. 39 and that, in connection with other information, it is an efficient aid in determining the relative value of different building materials. However, it is only one of the elements to be considered. For example, the crushing strength of cast iron, is about twice that of wrought iron, and of steel more than twice that of cast iron, but this does not make cast iron worth twice, nor steel four times as much as Avrought iron for use under compressive stress. In fact, the best practice adopts wrought iron in preference to either of the others for many po- sitions, but a knowledge of the sustaining power of the mate- rial is, and must be, essential to the designer. A study of the preceding tables shows that those specimens having a high crushing strength also rank well in the test for abrasions and impact, and it is reasonable to assume that the power to sustain great weight without crushing would be necessary to the durability of a block placed in a roadway, and subjected to the attrition and grinding due to that position. It is true that many experiments or tests are conducted in such a manner, and the results given so incoherently, that they are of little value, but where the work is carefully done, and the record clearly set out, so that knowledge of the com- parative strength of different substances can be gained from it, information regarding the crushing strength of any pav- ing material to be used in the form of blocks, will be sought and esteemed as of great merit in determining the value of such material. A recent circular from the State of 'New York has been placed in the hands of the writer, in which it is stated over a name preceding the title of civil engineer, that the " average resistance to crushing per square inch is 44,- 000 pounds " for a certain description of brick which had been tested by him. !N'ow, if that civil engineer had informed the public at large by what steps he had arrived at that remarkable conclusion, he w^ould have conferred a benefit upon his fellow 40 BRICK FOR STREET PAVEMENTS. men. The same circular contains further information as fol- lows: " Under an abrasive test equal to a traffic tonnage of 100,000 tons per inch of width, the loss was nine-sixteenths of an incli, or six and one-fourth per cent of the depth ; thus under a daily traffic of 100 tons per foot ol width of street, this brick would have a traffic life of twenty-eight years." That conclusion appears to be quite definite and satisfactory,, but there are ignorant people at large who know neither just what that abrasive test might be, nor by what process of reasoning such a result is reached. Some people might think that a daily traffic of 100 tons per foot of width for a period of twenty-eight years would not be equal to a traffic tonnage of 100,000 tons per inch of width, and thus conclude that, if the first premise is correct, such a pavement would, be good for at least two or three centuries; even upon the assumption that when it was half worn out the abutting owners might want it renewed for a change. The work done at this time for determining crushing strength is very incomplete, owing to the limited capacity of the machine, but it is believed to be accurate as far as it extends, and enables us to properly classify the specimens not having a resisting capacity exceeding 13,000 pounds per square inch. The Absorption Tests. For this class of paving material, a low ratio of absorp- tion is held by many to be a most essential condition, and therefore that this test is of the greatest importance. In our work this theory has not been accepted. Of all the speci- mens tested there is but one (No. 2) which should be rejected because of its excessive absorption alone, were all other characteristics satisfactory. Manufacturers have been told so frequently that a non -absorbent product is a necessary condition for marketable goods, it is so easy for them to- IJKK'K FOR STRP:ET PAVEMENTS. 41 l)riiig the rate down to two or thi-ee per cent, and the te^^t can be so readily made, that hut few street paving bricks are in the market which absorb moisture as freely as any of the stone blocks except granite. It is probably unfortunate that no variety of stone, other than Georgia granite, was included in the tests made, but sufficient experiments have been made with the various building stones to show that when the ]>er- centage of absorption is three or less, and the material is not laminated, they are neither perceptibly softened, nor made susceptible of destruction hy climatic influences. Me- dina sandstone absorbs from two to four per cent of moist- ure. Oolitic limestone absorbs from three to five per cent, yet no one asserts that either of these stones is softened or aftected detrimentally on this account, and the first is a stand- ard paving stone. Again, of the specimens crushed or subjected to abrasion, there is no indication, unless it be Xo. 2, in the Rattler test, that any one was weakened by its pre- vious soaking. Therefore, while it is undoubtedly true that a strictly non-absorbent material is the best, yet, among the paving bricks having percentages of absorption lower than three, while the advantage of an exceedingly low rate should not be ignored, other features may be considered. For in- stance, jN'o. 13 is shown to absorb less moisture than granite, and where it is not to be subjected to an excessive traffic, should on this account be favorably considered, but its en- durance under severe tests appears to be exceeded by some of the other varieties. Transverse Strength. The manner in which the transverse strength of the specimens submitted was determined has been described and tabulated, but in doing the work much information was gained that could not be written out. An unexpected de- 42 BKICK FOR fcTREET PAVEMENTS. ^ree of strength Avas exhibited hy ii niajority of tlie speci- mens. "While tliis test shows tlie tenacity of tlie material under a stress continually increasing- to the point of rupture, it gives but little information about the ability of the same substance to withstand the effect of blows or shocks. The Lehavior of the bricks at the instant of rupture is instruct- ive. Some of those which carried the greatest weights were much shattered. One of the number fives broke into three triangular pieces of nearly equal size. ^N'early every speci- men which exhibited the characteristic vitrified appearance, threw off flint-like s})alls, and presented an irregular fract- ure. Those specimens which in other tests manifested the greatest endurance were usually parted by a clean fracture almost at I'ight angles wnth the brick, directly beneath the central bearing, like the granite; while those having interior defects of any kind would separate at any point between the outer bearings. This test, therefore, is of much value to the experimenter, but the tabulated result is not a sure indica- tion of the value of the material for street paving purposes. Abrasion and Impact. The manner of conducting this work has been so fully •described, and the results set out in such detail in Tables 5 iind 7, that further comment is hardly necessary, yet it is plain that it presents no condition at all similar to that which obtains in actual service. The bricks are loose and battered upon all surfaces, whereas in the pavement they are held firmly in place and subjected to abrasion upon one side only. But in this case they were all subjected to the same treatment, and their losses should give a fair measure of their relative powers of resistance. ** The Rattler Test" has been frequently repeated by various parties, and a prac- tice is coming in vogue of assuming that a half hour or an BRICK FOR STREET PAVEMENTS. 43 hour in the rattler is equivalent to a year's wear in the pave- ment under a given amount of traffic, and from this assump- tion the prohahle life of the hrick in actual use in the street is calculated. By a somewhat similar course of reasoning, although the premises are more fully and fairly detailed, Professor Baker has calculated Table No. 7, given on pages 32 and 33 of his pamphlet on Brick Pavements, in which the life of a pavement made of each of the varieties of brick Avhich he tested, is given in certain streets of ten of the principal cities of this country. The daily traffic tonnage is taken from Captain Greene's statistics, and the results as tabulated are remarkable. His poorest brick would last four years on Broadway, ^N'ew ^ork, and one hundred and sixty- five years on Olive street, St. Louis; while his best brick would last thirty-eight years on Broadway, and fifteen hun- dred and twenty years on Olive street. The writer does not dispute such conclusions, but has no facts from which simi- lar inferences can be drawn. Statistics of Traffic and Durabililty of Pavements. Data regarding the traffic tonnage, and the efi:ect of such wear on street pavements and highways, has not been col- lected and preserved in this country in such form as to be available for ready reference. A few years since, Captain F. V. Greene prepared a paper, "An Account of Some Observa- tions of Street Traffic," which was published in Volume 15 of the transactions of The American Society of Civil Engi- neers. The observations were made by employes of The Barber Asphalt Paving Company, under Captain Greene's directions, during the months of October and November, 1885, in the ten large cities in which that company had offices and works. "The agent in each city was instructed to select the three streets in that city paved with stone, 44 BRICK FOR STREET PAVEMKNTS. asphalt, and wood (if any existed), which, by common re- port, had the heaviest traffic in the class of pavement used on that street. The record was in every case made on six consecutive days (Sundays omitted), at the same place, and it was continuous from 7 a. m. to 7 p. m., except when dark- ness prevented. No addition was made for this omission ; no record was kept during the night, and no addition wa^ made as an estimate of night traffic." '-The traffic is di- vided into three classes, light weight (less than one ton)^ medium weight (between one and three tons), and heavy weight (more than three tons). The Captain says : " I have discarded the weight of the horses altogether, not because they do not constitute a factor in the wear of the pavement, but because they Avere dis- carded in the English reports, and I desired, as far as possi- ble, to make comparisons with them." . . . "To obtain the tonnage, I estimated the light weight vehicles to average one-half ton each (including their loads), the medium weight two tons, and the heavy weight four tons." r l-horse carriages, empty or loaded. Light weight included -{ l-horse wagons, empty or light-loaded. i l-horse carts, empty. {l-horse wagons, heavy-loaded, l-horse carts, loaded. 2-horse wagons, empty or light-loaded. Tj / Wagons or trucks drawn by two or more Heavy weight included... | \^^^^^^ ^^^ ^^^^^^ ^^^^/^ " The average tonnage per vehicle ranges from 0.68 on Fifth avenue (New York) to 2.08 on a portion of Wabash avenue (Chicago). On Fifth avenue, 91 per cent of all the vehicles weigh less than one ton, while on Wabash avenue, only 25 per cent of them have so little weight. The general average for all the cities is as follows: Less than one ton^ 67 per cent ; between one and three tons, 26 per cent ; more- BRICK FOR STREET PAVEMENTS. 45 tlian 'three tons, 7 percent. The average tonnage per foot in each city, so far as here observed, varies from 151 in New ^York to 30 in Buffalo, and the general average is 77. For :all the cities in the table, the average daily tonnage per foot ^of width is 77, and varies from 273 tons on Broadway to 7 "tons on a granite street in St. Louis. The average weight .per veliicle is, for all the cities, 1.15 tons. The average ^width of street between curbs is 44 feet." This is believed to be the first carefully prepared census of travel made public in this country, and it was published by an officer of an asphalt paving company. It is fair to presume that one object in view was to show the durability •of that kind of pavement under heavy traffic. Since its publication, a few annual reports have contained statistics upon the subject, and the investigation has been greatly ex- tended by the diffi^rent asphalt paving companies. Obvi- ously, information of this kind should be officially compiled by municipal officers upon a uniform system throughout the country and its scope materially extended. The effect or wear upon the roadway of an observed traffic tonnage should be given, which has not been done except in a few of the English reports, and there mainly in cost of maintenance or repairs. Reports from Washington have given some data as to the cost of maintenance of certain pavements, and the English reports are usually quite explicit upon this point; but it would greatly benefit all municipal corporations in this country, were each to keep a record of the kind of street im- provements made, their manner and cost of construction; their durability and expense of maintenance, under a traffic, the volume of which could be noted with reasonable accu- racy, at but trifling expense. The omission of the horses from the traffic census is clearly a fault, as we know that they assist largely in wearing the roadway. For example. 4G BRICK FOR STREET PAVEMENTS. between the rails of street car tracks upon lines operated by horses or mules, the wear of the })avenient is due almost ex- clusively to this cause, and it is known to be very great. The tonnage of vehicles, as estimated by Captain Greene, is heavier than many observers would assume it to be, and the percentage to be added for the weight of animals will vary with the nature of the traffic, being greater with the light and less with the heavy traffic. His estimate beins^, that on Fifth avenue, which carries 91 per cent light traffic, the ad- dition should be about 85 per cent for the horses, while on Wabash avenue, w^here but 25 per cent is light traffic, the addition should be only about 40 per cent. The effect of the horse's shoe upon the street surface is modified by the nature of the pavement. Probably sheet asphalt suffers as little from it as any known form of wearing surface, unless the blows fall successively upon the same place and thus effect a displacement of the material. The bowlder is seldom scarred by it, hence the material of the cobble stone pavement is practically indestructible from this cause. Granite blocks are spall ed and rounded until they assume the form of bowl- ders, and, if very hard, become exceedingly slippery and af- ford insecure footing. Brick pavements would be rapidly destroyed were the bricks as widely separated as granite blocks usually are, but being placed in close contact, there is little room for the rounding away of corners. The brick surface is, how^ever, affected as it would be by receiving a like blow from a cutting tool or chisel of similar form. From this cause, will result by far the greater portion of the wear, since the pavement, when unbroken, will be sufficiently smooth to present but slight obstacles to the rolling upon it of the wheels of vehicles, and it will suffer comparatively little from that cause. The blow delivered by the animal's shoe will be greatly increased at high speeds. It would. BRICK FOR STREET PAVEMKNTS. 47 therefore, appear to be proper, that upon avenues carrying suburban travel, a census of traffic should take cognizance of the element of speed. The Probable Durability of a Brick Pavement. This chipping or abrasion of the surface by the shoes of animals traveling upon it will be its severest trial, and since no definite statistics are available by which to compute the traffic tonnage to which it will be subjected, and no test has been made which serves as an actual measure of the wear of a pavement under a given tonnage, the probable durabil- ity of this street can not be stated, but can only be predi- cated upon the endurance of the brick as compared with the granite. Judging this street by others upon which the cen- sus of travel has been taken, it seems fair to assume that the traffic will not greatly exceed 60 tons per foot of width per day, including the weight of horses, which will probably embrace one-half of it. The surface of a granite block pavement, as ordinarily constructed, is about 75 per cent granite, while a brick pavement is about 90 per cent brick. There is, therefore, about 20 per cent more brick than gran- ite to resist wear. The brick surface is comparatively smooth, while the granite is uneven. Wheels will roll smoothly over the brick, while they will jolt over the granite with a continual succession of blow^s. Let it be assumed that the wear due to horses on the brick will be 120 per cent of that due to the same cause on the granite, and the wear due to vehicles on the granite is 200 per cent of that due to the same cause on the brick : it follows that the total ef- fect on the brick is but 80 per cent of that on the granite. ]^ow we find in table 'No. 7 the loss of the brick in our abrasion testtobe 2.2 times that of the granite; a traffic, there- fore, which wears off one inch from the granite pavement 48 BRrCK FOR STREET PAVEMEXTS. will wear one and two-thirds iiiehevS from the brick; or, the time required to wear an iucli from the brick will be about 60 per cent of that required to wear an inch from the granite. Xo record is known to exist showing that amount of wear from a granite block pavement under a similar traffic, but about live times the tonnage has worn some portions of our city pavements to about that depth in four years. The estimated traffic is about 60 percent of that on Fourth street between Walnut and Race streets, exclud- ing street cars, and quite similar in character, taking the en- tire width of pavement (omitting car tracks), and live years' w^ear has been estimated to have reduced the blocks one- fourth of an inch. This would seem to justify the belief that this pavement should be in fair condition after ten years' traffic shall have passed over it. Municipal Methods. A cause for tlie lack of deiinite statistics upon these matters is apparent when inunici[)al methods are considered. American civil engineers have achieved a world-wide repu- tation for the boldness and originality of their designs, the skill exhibited in their execution, and the economy shown in attaining results. Great industrial establishments have been built, lines of transportation, with all the works appertain- ing thereto, have been by them located and constructed, and they are accredited with being well toward the van, and of contributing their full share toward the progress and devel- opment of the country. In all such w^orks facts have been collected and compiled, so that reliable data is available. Manufacturers are willing to guarantee a given mileage for their steel rails or car wheels, or a given strength for their iron and steel, from data made available by engineers, but in municipal matters the conditions or the results are in noway BRIOK Full STRKET PAVEMENTS. 40 similar. The total amount of money annually expended by the municipalities of the country in opening, improving, cleaning, and repairing streets and highways, is an enormous sum, exceeding that applied upon all other public works in an equal length of time. The greater part of this fund is nominally disbursed under tlie supervision of engineers, but the results are not such as to add materially to the renown of the profession, or to supply exact data for their guidance in present or future works of this character. One reason for this appears to be found in the fact that these funds furnish the greatest of the existing causes of activity in local pol- itics. Municipal statesmanship is developed in levying, watching, and disbursing this money. Laws providing for its collection, control, and disbursement have been enacted, termed the municipal code, which is more complex and pe- culiar than any other system known to man. Boards and Bu- reaus, Councils and Commissioners, Supervisors and Direct- ors, Counselors and Barristers, have been created or called to govern the work, guard the public interest, acquire fame, and enjoy the advantages accruing to exalted official position. The pervadingspirit of freedom abroad in the land being averse to the creation of such a class as controls similar matters on the continent of Europe, the rights of the people are sought to be preserved by the checking and balancing of sovereign and independent departments. When new things are to be done, additional statutes are enacted and more boards pro- vided. One authority will make an improvement and an- other will dig it up, while no one will repair it because the courts have not decided the question as to which fund shall be drawn upon for meeting the expense in cases of that na- ture. Volumes of annual reports from the heads of the sov- ereign departments and chiefs of the multitudinous bureaus into which they have been sub-divided, assure a confiding 50 BRICK FOR STREDT PAVEMENTS. public, that, since the advent to power of the present incum- bent, the affairs under his control have been conducted upon strictly business principles, thus enabling him to grant more permits and file a larger number of papers than had ever be- fore been handled by similar ofiicers in a corresponding length of time. When the balance of power between po- litical parties is indefinite, and changes in official stations become so frequent as to make employment uncertain, it is sometimes found expedient to further revise the stat- utes and make non-partisan boards, who then carefully di- vide the appointments and perquisites between contending parties, accurate data for the making of such partitions be- ing always available. The smaller municipal organizations copy the '^ systems" of the larger ones. Under such regulations no very considerable amount of " engineering " is required. A " chief engineer " of suitable political complexion is chosen to sign the necessary papers, to whom matters not well understood by other parties can be referred and reported upon, and who can be blamed when it becomes absolutely necessary to locate responsibility some place, and who is willing to allow officials and other influ- ential parties to appoint his assistants, clerks, rodmen, and superintendents. Men who have acquired skill and experi- ence in the construction of works under different regulations seldom take kindly to this order of things, and the field is left free to such as enjoy the surroundings. Many careful and painstaking men are engaged in city work who would make excellent records were they not handicapped by the regula- tions governing them, and almost the entire number are like the parents of heroes, " poor but respectable." Having little at stake except their integrity, that is manfully cher- ished. Occasionally an erring brother may fall, but he merely drops from the ranks which close in his place. The BRICK FOR STREET PAVEMENTS. 51 ainmunition of the enemy, which is most dangerous, espe- cially to those of limited experience, is flattery. ISTot one person in ten thousand of those having experience upon public works would ever approach an engineer with money or a valuable consideration for corrupt purposes, but if the insidious agent can induce him to believe that his genius is apparent to all, and that the world, especially the official part of it, will soon be shouting his praises, such influences may cause the young man to make himself ridiculous. But there is a great following who have a sufficient knowledge of surveying to enable them to handle field instruments, set out work, and compute quantities, who have but little taste for such study or investigation as is necessary to acquaint them with materials, or render them skillful in designing or constructing engineering works ; and their appears to be a greater demand for these persons on municipal, than upon any other class- of public works. This is probably because they have more leisure for compiling political statistics than others, are less liable to have bothersome opinions about how things should be done, and can more readily discern the grade and character of improvements desired by those in power or opposed by those 7iot in power, which is usually the same thing; it being always understood among municipal statesmen that an election or appointment to office confers upon the recipient of such honor all the necessary knowl- edge and experience required, not only to choose an engineer, but to tell him what to do, and just how to do it. Many re- cruits are obtained from those estimable young men annu- ally graduated from our technical schools and colleges. The learned professors solemnly announce to such of their stu- dents as have pursued certain lines of study, that they are now civil engineers. The young men very properly have great confidence in their teachers, and believe what is told 52 BRICK FOR STREET PAVEMENTS. them to be literally true, but when they go abroad in the world and learn that what the professors really meant was, that they were qiialitied to obtain employment upon public works, where, by continual study and actual practice, they could become engineers; the shock is very great, many never recover, and some are engaged by municipal corporations. Such as do recover are achieving great success in professional work. The number and sovereignty of the departments, the uncertainty of the laws (for no one dare hazard any thing more than an opinion regarding the rule of action prescribed by a statute until the court of last resort has guessed at its meaning), and the strifes of contending factions have pro- duced conditions so different from those which would ap- pear to be proper that heroic measures may be required to effect desirable changes. Unless the people at large can be induced to look upon the matter of municipal government as a grotesque absurdity which is really being enacted at their expense,.as it is, the code will continue to be enlarged and the Boards multiplied. When they induce the law makers to re- peal the thousand and one statutes w^hich now exist, and enact a plain, concise code of rules, and not amend it, which will place the direction of public works under a single de- partment, with uniform regulations in like municipalities throughout the state; placing the designing and manage- ment in the haiids of a corps of engineers who should ac- quire position and promotion by the record of their achieve- ments, and not by reason of race, creed, or previous con- dition of partisan servitude or influence, and who, being un- trammeled as in the world at large, would succeed or fail by merit alone, the principal of natural selection, or the survival of the fittest, would soon place the direction of such works in systematic order under competent control. Then would BRICK FOR STREET PAVEMENTS. 5o streets be built to remain undisturbed, as the bottom layers or drains and pipes would first be put down and carried to property lines, then would the character of the pavement be adapted to the uses to which it would be subjected. Paving companies would construct streets and guarantee them to lemain in proper form and repair until a speciiied tralRc ton- nage should have passed over them. Manufacturers would furnish materials under like conditions. Order and uniform system would exist where chaos now reigns, and legislative interference would cease to trouble executive business. Probably the view is Utopian, and will never be realized until we pace those golden streets, but the patching remedies and special laws continually being enacted forthe betterment of evils known to exist are only adding complications to complex affairs, and it thinking people are induced to direct their attention to a subject of such universal and vital inter- est, and make an effort in unison to better municipal govern- ment as applied to public works it will certainly result in some good. Politicians and bosses will undoubtedly offer great obstacles, but the mere absurdity of present methods will insure a change, and if engineers were accorded similar freedom and control, with such responsibilities and oppor- tunities as are given them upon other works, they would not ignore so inviting a field as that presented by the needed im- provements in these matters. General Discussion of Pavements. The office of a street pavement is to provide a w^earing surface which shall fulfill the following conditions : First. It must present a secure and pleasant footing for animals. Second. It must have sufficient smoothness to render traveling in carriages agreeable, and traction easy and as nearly 54 BRICK FOR STREET PAVEMENTS. noiseless as is practicable, for all descriptions of wheeled ve- hicles (excepting those provided with, flanged wheels). Third. It must be of such form and material that liquids falling upon it will quickly flow from it into proper conduits, and must furnish no permanent lodgment for street filth of any kind. Fourth. It must be capable of sustaining without change of form, any and all loads usually transported on public highways. Fifth. It must be reasonably durable, both as against the attrition of street traffic, and the destroying or dissolving action of the elements. Sixth. It must be economical. That is to say, sufficient comfortable use must be obtained from it to make it worth both the cost of construction and maintenance, Seventh. It must be capable of removal and replace- ment, or repair from failure at reasonable cost, and with materials and appliances within the control of the street re- pairing department. A study of these conditions at once reveals the reason why the ^' paving problem" is of such an intricate nature that it has so long remained unsolved, as well as a cause for so many unhapp}^ failures in its attempted solution. For the first and second conditions, the dirt road in good repair stands without a rival, but it meets no other require- ment, hence its use is i-estricted to race tracks and country roads, which like canals are only navigable when the weather conditions are favorable. For the second, third, and fourth conditions, the asphalt pavement on proper foundation appears to be better fitted than any other that has come into such general use; but many persons say that it does not properly meet the first re- BUICK FOR STREET PAVEMENTS. 55 quiremeiit, criticise it severely as to the fifth and sixth, and aflirni that it utterly fails to meet the seventh. Stone block pavements meet the first requirement, but indifferently; utterly fail in the second and third, when properly constructed; are better adapted to comply with the conditions of the fourth, fifth, and seventh, than almost any other description of city street, but when a high charge for transportation is to be added to the cost of preparing the material, they fail to meet the sixth condition. Wooden block pavements meet the first, second, fourth, and seventh conditions fairly well, when made of suitable materials well combined ; but, as they have been built in this country, have signally failed to meet the third condition, and have fulfilled the fifth and sixth but very indifferently. The bowlder or cobble-stone pavement has been with us so long, and has been treated so badly, that familiarity with it has bred a species of contempt that is hard to overcome. It has become popular to consider it an all around failure, yet it meets the first and seventh conditions fairly well, and so far as the material is concerned, it stands unrivaled in the fifth. In many of our cities where horse cars have been operated for the past twenty or thirty years, and the street railway companies are required to maintain the pavements within their tracks, the bowlder pavements are still retained between the rails, while the residue of the streets have been paved with other materials, because in that position they are said to meet all of the conditions named, excepting possibly the second and third, better than any other substance yet offered for the wearing surface of roadways. This saying, however, does not appear to be any thing more than an expression of opinion, which can not be sustained by any process of rea- soning. The cobble-stone can be given no definite bearing on any foundation ; it can not be held in position by any bond 56 BRICK FOR STREET PAVEMENTS. that can be given it in construction. It does not present a suitable surface for vehicular travel, or that can by any pro- cess be ke[)t free from filth ; yet it does not wear out, is easily restored if loosened from its place, and it does answer very well for street car horses to travel upon. Broken stone or macadam as commonly used, of mingled limestone and shale, meets none of the requirements. If,. however, it is clean refractory material, properly prepared and combined by rolling, it fulfills all the conditions except the third (and even that reasonably well), providing the traffic is moderate, and the repairing is promptly and efficiently done. It may be set down as an established fact, however, that wh'en a macadamized street is dug into for any purpose that it is never properly replaced. No one of these conditions can be entirely ignored, yet it is obvious that no pavement yet devised, fully meets all of them. Could the first be ignored, it would be an easy mat- ter to cover street surfaces with iron or steel plates that would fully meet all the others, but plainly this can not be done. The surroundings of the pavement and the extent and nature of the traffic to which it is to be subjected, must be considered in order to decide which of the conditions shall be allowed to determine its character. The first, that of furnishing a secure and reasonably comfortable footing for animals, can in no case be ignored, and in many instances must control all other considerations. Wherever the pave- ment is to be used as a thoroughfare for vehicular traffic at fair rates of speed, or when time, pleasure driving, or quiet- ness become elements of importance, then the first and sec- ond conditions must be met, and other features may or may not be caused to yield to their requirements. But the pres- ervation of life and health is the essential cause of business BRICK FOR STREET PAVEMENTS. >) ( activity, hence the third condition, that of maintaining cor- rect sanitary conditions, should never be neglected. To those at all familiar with street construction, it is obvious that the wearing surface, or pavement proper, can not, and does not in itself, support the loads brought upon it, hut that it more or less successfully resists the impact and abrasion incident to the traffic, and transmits the weight di- rectly to the bed or foundation upon which this surface ma- terial has been placed. It follows, therefore, that the fourth condition can be met by any description of paving material which has sufficient hardness to retain its form under the pressure of street traffic, by merely placing it on a properly prepared foundation; and further, that unless the pavement shall be placed upon a bed capable of sustaining under all conditions the loads brought upon it, the surface will yield regardless of the material of which it is composed, and that this condition not being complied with, no essential feature of a good street surface will remain. Failure to meet this condition is the error most commonly committed in the build- ing of pavements. In this latitude the winter frosts pene- trate to a depth of from one to three feet, or, when not acted upon by frost, the subsoil drainage is seldom so thoroughly efficient as to prevent the changing of the ground from a firm unyielding soil to one of almost complete saturation, thus materially affecting its sustaining power. It therefore follows that no pavement wh:ch is to be subjected to a heavy traffic at all seasons of the year can be relied upon to retain the form originally given it, unless the foundation or bed upon which it is placed shall either be carried below the ac- tion of the frost, say three feet or more, or be so constructed as to distribute the weights of passing loads over sufficient areas to enable a comparatively weak subsoil to sustain them. The deep foundation is the ancient, and undoubtedly 58 BRICK FOR STREET PAVEiVIENTS. the most durable method, having apparently been the ordi- nary practice with the Romans, but the distributing coating is far more economical, and hence has become the established modern practice. Two methods are in vogue. First, to drain the sub- roadway as efficiently as is practicable, grade it to the proper form, compact its surface by rolling, and cover it with a layer of mingled broken stone and gravel, which is made smooth and firm by flooding and rolling with a steam roller ; the layer of metal being from six to twelve inches in thick- ness, according to the requirements of the locality or the specifications. On this layer or "foundation" is spread the bed of sand, in or upon which the pavement is set. Some- times broken stone alone, and again gravel only, is used for the bottom course. This style of " foundation " is used very extensively for all descriptions of pavements excepting as- phalt. With brick pavements the practice of placing a layer of bricks flatwise on the bed of sand, covering them with a thin coating of sand, and paving on it the wearing surface on edge, is quite common, and produces what is called the "two course" pavement. Still another method consists in covering the layer of sand with tarred boards, upon which the sand cushion and brick on edge are paved herring-bone style, producing the "Hale Pavement." In this, however, the broken stone is generally omitted, the boards being sepa- rated from the subsoil by from four to six inches of sand only. These expedients tend to better the distribution of the weights brought upon the pavement, and have the merit of economy in first cost, but they are obviously inade- -quate except where the subsoil is exceptionally good and the traffic very moderate. The method of combination is quite defective. When gravel is used that is free from loam, it will not compact under the roller, and if it does contain BRICK FOR STREET PAVEMENTS. 59 loam the water which comes from the subsoil, and percolates throii2^h it, is liable to carry the soluble substances with it down the gradients, and leave the pavement unevenly sup- ported. When broken stone and gravel, or broken stone alone, forms the foundation course, it is expected to be por- ous, and act, to some extent, as a subsoil drain. The voids, however, are liable to become the receptacles of the clay from beneath, which is brought uj), or rather the stones brought down, by the pressure upon the pavement, or they will be tilled b}' the sifting down of the bedding course of $;as companies will carve it to erect their lamps. Each will ce- place the disturbed material in his own way, and the street- cleaning department will haul away such as remains lo<)se upon the surface. In the meantime no one looks for, or remedies defects in their incipiency, the street having JMst been paved is supposed to require no attention, and so long as it remains passable without danger to life and limb, is not repaired. If a drain becomes clogged no one knows aMy- thing about it until the owners of the inundated properties file claims for damages, which are promptly referred to the engineer and solicitor. If vehicles are wrecked or animals crippled the claims filed by owners go to the legal depart- ment, and not until the street has been absoluteiy destroyed will it receive any attention from the repairing department. If it should happen to have been constructed under the supervision of officials of an opposite political complexion from those now repairing it, money will be lavished upon it to show how utterly rotten and useless were the works con- 8 82 BRICK FOR STREET PAVEMENTS. structed at enormous expense by the other party. Should it be some of their own work, it will be easy to show that it was honestly constructed, but was ruined by the actions ol* other sovereign and independent departments. Imagine the effect of placing railways under the control of half a dozen independent boards with no executive head, their revenues separated into distinct funds with sovereign boards to disburse them, each caring mainly that its minutes shall record resolutions, ordinances, or references in proper sequence and due form; so ^vorded as to guard the rights and actions of the board as a body, and show that various matters were considered^ and would be acted upon when some other department had done something else. Think of any corporation conducting any business enterprise upon such methods, and cease to wonder why pavements are not kept in repair. During the first years of the life of a pavement it should be carefully watched, and the beginnings of evil to it should bo checked, just as a new line of railway will require a heavier force of section men than one that, having been pi operly maintained, has been longer in use. Expensive re- newals may be needed as portions of the structure become T^orn by use, but care and watchfulness are of greatest use upon new work. And this is just as true of streets as it is of any like constructions. Contracts for street construction frequently contain provisions requiring the constructor to maintain his work for periods of time varying from one to five or more years, but the meaning usually given this clause l)y the contractor is that, at the expiration of the time uamed he shall make such repairs of the portions of his w^ork which have not been dug up in the interval by some other party as may be designated, and received the retained percentage. There is uncertainty about this provision re- maining in force for any considerable length of time. En- BRICK FOK STREET PAVEMENTS. 88 terprising attorneys may argue that assessments should be made for the cost of construction, and that the expense of maintenance should not be assessed, but borne by the corpora- tion, and no one can tell what the court will say until it speaks in deciding the case as then presented. An etHcient force, under experienced, skillful direction, employed in the inspection and maintenance of streets would appear to be an absolute necessity in every municipality. If such an organi- zation exists in any American municipality, it has published no report of its services to date. If existing regulations can not be bettered, then our form of government as applied to municipalities is a failure. What is in a ^^ame. The title hrick^ as applied to clay products used for street paving, would appear to the writer as a misnomer. The name ordinarily conveys to the engineer or builder the idea of a brittle porous substance, so hungry for moisture that it must be saturated before being laid in mortar, solely for the preservation of the mortar, so brittle that unless combined in masses it has little strength, and in no way suited to with- stand the attrition or abrasion of street traffic. When [leo- ple propose to use such a substance for paving streets, the idea is ridiculed, and they must explain that they are not using building brick, but an entirely different substance, manufactured by brick makers, and in explaining the matter use is made of the other unhappy term, " vitrified brick.'' The only clay product suitable for use in paving streets re- sembles a tile in more respects than it does a brick, and had the name tile been chosen in the place of brick a more cor- rect idea would have been conveyed. The first having gone forth, however, it may be expedient to concur in the usual practice, but it will always be necessary to bear in mind that brick as used in street paving is a substance radically differ- ent from brick as used in anv other connection. 84 brick for street pavements. Size of Paving Brick. A glance at the tables giving dimensions of specimens reveals the curious fact that hardly any two manufacturers make bricks of the same size. One of the first steps to be taken by manufacturers should be the adoption of a stand- ard size for street paving bricks. Obviously their preference would be to make blocks of about the same dimensions as building bricks for both uses. When they make paving blocks only, and sell by the square yard, their interest will lie in the direction of increased thickness and diminished width. A large majority of manufacturers supply material for brick masonry as well as for paving, and can assort their output without material loss, thus enabling them to supply better goods for paving when they are required so to do, without suffering the entire loss of the value of such as may be re- jected. This, from the manufacturers' standpoint, is the greatest argument in favor of making the dimensions of paving the same as building brick. The users side of the question should be considered. The width of the brick or block forms the thickness or depth of the pavement. This should not be less than four inches. If made much in excess of that depth its cost will be increased about in the ratio of the increased depth. In- asmuch as four inches will afford ample strength and weight to resist the wear of the traffic to which this descrii)tion of pavement is suited, there appears to be no reason for mate- rially increasing the width beyond that named unless it be to meet exceptional cases. In the future, should it appear that brick are so perfected as to be able to carry the ex- tremely heavy traffic concentrated upon business thorough- fares, where granite block pavements are now thought to be most suitable, a greater width may be found desirable. The length of the brick or block should be about twice its width; BRICK FOR STREET PAVExMENTS. 8.') its thickness should not exceed its width and may be made <3qiial to it, providing such a block can be properly burned. The writer does not say that manufacturers can not properly dry and burn a brick three or four inches in thickness, but he does say that they do not do it. The conditions and the experience all indicate failure when massive pieces of clay are sought to be burned into bricks or blocks suitable for street paving. The nearest approach to success, has been at- tained by making the block hollow on the lower side in or- der to facilitate burning. For the solid block a thickness of two inches, or at most, two and one-half inches, is as great as should be attempted. Even where the clays can be melted or "vitrified" readily, there is great risk incurred in at- tempting to increase the thickness, for such clays usually contract greatly, and the outer surface is almost certain to be fixed or seared by the intense heat before the inner por- tions shall have been so acted upon as to produce the re- quired vitrification. As a consequence they come from the kiln eitlier insufficiently l)urned, checked with " fire cracks," either internal or external ; or, like an ill-shaped casting, so affected by internal strains as to have no certain amount of strength. Better results are, therefore, likely to be secured hy adopting about the building brick dimensions than by at- tempting to manufacture blocks of a larger size. Unfor- tunately those dimensions have never been determined with much accuracy in this country, but they should be, and then let manufacturers vary the dimensions of their molds as the contractility of the clays vary, so that bricks of equal hard- ness shall be of like dimensions. It may be argued that the increased number of joints in a given area, caused b\' the thinner block, constitute an ele- ment of weakness and should, therefore, be avoided. The defect is more imaginary than real, since the proposition can 80 ■ BRICK FOR STREET PAVEMENT.-. not be true if made general. The perfect pavement would become one without joints, which is impracticable unless made of a substance sufficiently yielding or elastic to afford secure footing for animals, which practically makes it a surface of innumerable joints. An advantage claimed for brick pavements is said to be the fact that they can be so closely laid, and the joints so completely tille'd, that, while they furnisli secure footing for animals, they are so smooth as to be quiet, and so impervious as to be cleanly. If this be true, the additional number of joints is not objection- able. They are not an element of weakness, since the load must in any case be carried by the foundation, and the up- per and lower surfaces being equal, the Aveight transmitted by the brick will be as its area. Should the surface of the fouridation be uneven, the smaller block is less liable to be tilted by an unequal pressure than the larger one. AVithin reasonable limits, therefore, the safe course to pursue w^ould undoubtedly lie in the direction of the thinner blocks; or, in other words, to adopt a standard size for paving blocks corresponding with building brick dimensions. a /"'^^ 028 145 881 4