CITY ROADS AND mm PAVEMENTS g^-'/x <#1^: it ;A Book_ Ig'^^ Copyright N" COPVRIGHT DEPOSIT CITY Roads and Pavements SUITED TO CITIES OF MODERATE SIZE Second Edition, Revised and Enlarged, BY William Pierson Judson, M. Am. hoc. Municipal Improvements, M. Am. Soc. C. E., M. Inst. C. E. > ' ' >> ) , > , ' > ) ) J J NEW YORK The Engineering News Publishing Co. 1902. THE LIBRARY OF CONGRESS, Two Copies Received JUL. 26 1902 Copyright entry 01 ASS VtXXa No. COPY 8. Copyright, 1902 by WM. PIERSOX JUDSON. /i :rr^ f c c CHAS. VAN BENTHUYSEN & SONS, PRINTERS. TABLE OF CONTENTS. PREPARATION OF STRP:ETS FOR PAVEMENTS— (Page 7) Reduction of width. Drainage. Subdrainage. Rollers. Roll- ing dirt roads. Wide tires. Pressure of traffic and of struc- tures. ANCIENT PAVEMENTS— (Page 17) Oomparisons. Stone wheel-tracks ; competition with first railway. MODERN PAVEMENTS— (Page 25) Comparative loads. Cost. Pavements for steep grades : asphalt; vitrified brick; creosoted wood block; block stone; broken stone ; bituminous macadam, Crown of pavements : Rosewater formulas of 1898 and 1902. Form of crown: for macadam. Falls of horses on different pavements. Culverts: kinds ; sizes ; costs. Curbs : kinds ; sizes ; costs. Car-track construction. CONCRETE BASE FOR PAVEMENT— (Page 42) Need. Subgrade. Cement : simple outfit for easy tests ; fine- ness ; quickness; soundness; purity ; weight ; results. Manner of use. Aggregates. Sand. Proportions and mixing. Water. Machine-mixing. Spreading and ramming. Monolith. Sur face. Setting. Wetting. Freezing : use of brine; limit of cold Cost, Portland. Natural. Extra work. Table, 36 cities. BLOCK-STONE PAVllM HNTS— (Page 57) Defects. Merits. C'ost. Extent. WOOD PAVEMENTS— (Page 66) Old. Cedar block. Modern. Australian. American • kreo- done-creosote; creo-resinate ; cost. TABLE OF CONTENTS. VITRIFIED BRICK PAVEMENTS— (Page 82) Modes. Extent. Objections. Production. Characteristics. Qualities. Tests. Examination in use. Construction : base ; sand cushion ; joint-fillers ; expansion. On steep grades. Cost. Guarantee. AMERICAN SHEET-ASPHALT, ARTIFICIAL AND NA, TURAL— (Page 103) Comparison. History. Artificial. Natural. Companies. Sources. American artificial : materials and methods ; founda- tion; binder ; wearing surface ; roUing. Steep grades. Crown. Railway tracks. Cost. Guarantee. Causes of failures. Block- asphalt; extent; cost. Comparative preferences, asphalt and brick. BITUMINOUS MACADAM PAVEMENT— (Page 131) Characteristics. Details. Methods Cost. Opinions. BROKEN STONE ROADS— (Page 138) Extent. Rock for roads. Tests of rock. Telford and Mac- adam : relative costs. Binder : mode of use ; (quality ; quan- tity. Maximum grades. Construction. Subgrades of various kinds. Rock : crushing ; screening. Base. Top. Thickness. Crown. Cost. Cautions. Maintenance. Methods of repairs • raveling ; rolling ; ruts ; cleaning ; cost. Re-surfacing : methods ; cost, INDEX— (Page 187) PREFACE TO SECOND EDITION, The local features of the fir.^t edition, havini^ served their purpose, have been omitted, and modifications have been made to show the present applications of general methods, some of which have changed since 1894. The most marked change during the past eight years has been in the increased use of crushed stone for roadways of macadam and of telford construction, on the improved streets of villages and cities. A notable instance is that of the city of Greater New York, which contains outside its parks eight hundred miles of crushed stone roads built since 1894. This general increase has resulted in part from the work begun in 1893 by the State of New Jersey, followed in 1894 by Massachu- setts, in 1895 by Connecticut and in 1S98 by New York. The examples given by the governments of these States in building highways by State aid and outside corporate limits, have led to the building by the municipalities of similar roads within many cities and villages, which have thus wisely profited by the experienced methods of State officials. The results have l)een an increasing extent of the best kinds of roads of broken stone, and a growing knowledge of the methods and machines by which alone can such roads be built and main- tained. These are here described under the heading " Broken Stone Roads," without however differing essentially from the descriptions given in the first edition. The grade of a city street is usually a fixed condition and not a theory, and it is often difficult to decide which is the best pavement for a fixed steep grade in a given climate, or how steep a grade will give good results with a given pavement. Tables of actual instances are given in order that engineers may know where to find condi- PREFACE TO SECOND EDITION. tions similar to their own, and where they may examine certain pavements in actual use. To watch the traffic using a steep paved slope or to examine its condition during a sharp shower or after a heavy rain, will suggest points as to the proper grade and crown which will be worth any amount of theorizing as to maximum grades. The sections entitled respectively " Concrete Base," '^ Block Stone," " Wood," " Vitrified Brick,' " Asphalt," " Bituminous mac- adam '" and " Broken Stone," are made to accord with the latest records of methods and costs, using illustrations and tables for brevity. These records have been obtained from personal practice and investigation and from the publications and discussions of the several Societies of Civil Engineers, from the reports of the officials of States and Cities, and from the columns of Engineering News, The Engineering Record, Municipal Journal and Engineer, The Engineering Magazine and Municipal Engineering, and also directly from many civil engineers in addition to those whose names are mentioned. The uniform courtesy shown by civil engineers, both in the United States and abroad, in cordially meeting inquiries regarding their works, methods and results, and in freely giving all desired information, is a marked and peculiar characteristic of the Profession. These statements of facts and opinions are meant for those who wish to profit by the varied experiences of practical road makers. Wm. p. J. Oswego, New York, May I, 1902. CITY ROADS AND PAVEMENTS SUITED TO CITIES OF MODERATE SIZE. The extent of street-surface in the cities having a population of fifty thousand or less is usually such that only a portion can be paved or improved at any one time, and it is therefore necessary to carefully study the local conditions existing in any given city in order to determine which of the various kinds of pavement are best suited to the existing conditions of slope and of trafific and of treasury, and to the local supplies of proper materials. REDUCTION OF SURFACE TO BE PAVED. In cities which have always had dirt roads, the actual width of roadway is usually much greater than is needed for the traffic, and the subject should first be studied with a view to reducing the area to be paved by widening the bermes and the sidewalks on each side of the street, and thus narrowing the roadway to a width no greater than the traffic demands. Many cities have 42 feet to 45 feet width of dirt roadway on residence streets where 26 feet and 32 feet would be an ample width between the curbs of the same streets CITY ROADS AND PAVEMENTS. when they are paved ; 32 feet is the width most often used. The beauty of the streets will be much improved by such change and by forming on each side of the street a w^ider grassy berme outside of a row of trees, and this change will also give room for wider sidewalks, which in many cases are much needed. These wider bermes can usually be formed from the worn earth and sand which must be scraped from the surface of the existing old roadways before attempting to form new ones. DRAINAGE OF ROADWAY. Having determined the proper widths of roadway of the various streets, their grades should be most closely studied in order to get the best results with the least change of existing grades ; it should be considered that the proposed pavements with their curbs, crossings, manholes and catch-basins will be, or should be, per- manent structures and they should be located carefully. Before paving any street, there should be in place a complete system of sewers and of pipes for water and for gas with service-branches to every lot on both sides of the street, and with manholes to give access to the sewers, and with catch-basins so arranged as to take the storm-waters without blocking the sewers with street-waste and silt, which can readily be prevented from entering the sewers by the use of recent improve- ments in catch-basins. In designing these sewers, and in considering whether existing sewers are sufficient, it must be remembered that the proposed pavements will bring the storm-water into the sewers more quickly and that larger capacity will be needed to carry the in- creased flow. 8 SUB-DRAINS. Careful consideration sliould also be u"i\'en in order to decide whether the local conditions make it best to pro\'ide sub\va)'s for electric wires. The thorough drainage of such streets as ha\e been naturally muddy in spring and in fall, must be provided for before any method of pa\'ing or surfacing is consid- ered. The natural earth is the real roadbed which does the work, and it can only support the pave- ment — of whatsoever kind it may be — by being- kept dry. In most of the cities, a portion of the streets have good grades and will drain naturally if rightly formed ; and it is the streets running at right angles to these which will be most difficult to drain, especially if thev are on a hillside ha^ing springs in the subsoil, which must then have sub-drainage by tile drains before an\' form of surface or of pavement will be of permanent value or effect. There are many such streets on which rain water now stands until it evaporates. On the ordinary street in northern cities, the direct rainfall between fence- lines per mile, is equal to 30,000 tons or 8 million gallons of water every year, and there are mam' streets where this water has been left to evaporate or to soak into the ground. SUB-DRAINS. Any such roadbed, where, from any cause, water naturally stands and forms mud, must be thoroughly sub-drained. To put broken stone, or gravel, or anv valuable material of any kind upon a bed of earth and ashes which rain will conxert to mud, is to throw away both money and material. CITY ROADS AND PAVEMENTS. The sub-drains should consist of Hnes of two inch to four inch porous tile, or four inch to six inch vitri- fied tile laid with open joints ; one line on each side of a level road which receives drainage from both sides, or one line only on a hill-side road, this being put on its up-hill side to intercept ground-water from the higher ground. These tiles should be placed on an accurate grade, a foot or more below the bottom of the gutter, next to the curbs, away from tree-roots and below frost, in order to lead the ground-water to the catch-basins or road-culverts, from which it will run to the sewers or outlets with the surface-water from the pavement. The provision of this sub-drainage should be the first move toward making any permanent roadway on a fiat street. ROLLING THE EARTH ROADBED. For any method of road-making or of paving which may be adopted, a steam roller of about ten to twelve lO ROLI.INCr THK KARTII K( )AI)l',i;i ). tons weight is requisite in order to compact the eartli roadbed so that it will sustain the wheels which will pass over it. As well try to make the bricks of old Egypt without straw as to try to make the roads of to-day without a heavy steam roller. Every fully equipped road-builder has one or more. There are few cities which have not made some effective efforts to have good roads, and those which have done so know from experience that no good results can be expected until the proper tools are used. For any system of pavements or of roads, a steam roller is the thing first needed, and no contractor's bid should be considered unless he agrees to provide and use a steam roller of at least ten tons weight so proportioned as to give not less than 500 pounds pressure per lineal inch of face of the roller-wheels. The undulations and hollows which may be seen in the surface of many existing pavements are the direct results of the lack of a proper roller which would first 1 1 CITY ROADS AND PAVEMENTS. have disclosed the presence of the soft places in the earth roadbed, and then would have packed the grad- ing-material into them, so that the finished pavement would have had a solid and peniianent foundation and a regular surface. GOOD EFFECT OF ROLLER OX DIRT ROADS. Especially valuable would such a roller be for cities ha\dng great extent of dirt roads, which could be fonned by use of the wheeled scraper and then rolled to a smooth, hard surface, furnishing fine roadwavs during the summer months until the fall rains make them muddy. By rolling the roads as thev freeze, towns can make their earth streets smooth for the whole ^\"inter and so that a few inches of snow will give good sleighing. Nearly a mile per day of temporary, summer road- wav can be made at small cost by a scraper, sprinkler, and steam roller working together. The sprinkler should be selected to have six-inch tires with rear axle two inches longer on each end than the front axle ; it should be built without a reach so that it can be turned without digging holes in the roadv\'ay, and should have a sprinkler which is under the perfect control of the driver. The roller should be selected to be of not more than ten or twelve tons actual weight when loaded, so that it can cross ordinaiy bridges safely and can roll streets ^rithout crushing buried pipes. The roller should be tested to see that it can climb ten per cent grades when thev are covered with loose stone, and also that it can hold its steam-pressure during continuous operation, 12 PRKSSIKK OF 'IKAKFK and it should also have a record for durability under rough usage. WIDE TiRKs ON \viii:i:i.s. To supplement the good effect of a roller on the dirt roads, which are now cut by narrow tires, the use of wide tires on heavy wagons should be required. The following is a practicable way of initiating such a rule: Let the Board of Public Works of any city order that no wagon will be employed upon city work unless it has four-inch tires on its wheels, with the front axle eight inches shorter than the rear axle. This will make each wagon equal to two eight-inch rollers. Let the same order be applied to ice- wagons and to public carters, as a condition of issuing a license. A future date could be published at which all heavy wagons doing business in the cit)', including farmers' wagons from the surrounding country, shall have such wheels. This publication will stop the sale of narrow- tired wagons, which will gradually be displaced by those with wide tires, when the roadways of the vicinity as well as of the city itself, will no longer be so deeply cut and furrowed as now by the pressure of traffic. PRESSURE OF TRAFFIC. It is only necessary to consider the great pressure which ordinary traffic will put upon the roadbed in order to realize that no pavement can keep its form and its regular surface unless the earth roadbed, on wliich all the pressure finally comes, has been perfectly compacted before the pavenient is laid over it; for the pavement, of whatex'er material it may be, is merelv a 13 CITV ROADS AND PAVEMENTS. 14 COMPARISON WITH PRESSURE OF STRUCTURES. more or less rigid surface wliicli receives tlie pressure of traflfic and distributes it to tlie supporting eartli. For instance, the ordinary coal wagon, weighing 1,200 pounds, draws two tons of coal and has tires two inches wide. As the wagon stands on the pax'enu'nt, thu bearin«^ surface does not exceed a leuLTlh of one and one-half inches on each wheel; the four wheels thus standing upon a total surface of twcK^e squai-e inches, with a total pressure of 5,200 pounds, or 433 pounds per square inch, and this is applied with a rolling pressure w^hich is most destructive. COMPARISON WITH PRESSURE OF STRUCTURES. The degree of pressure which this puts upon any pavement will be best appreciated bv comparing it with the pressures per square inch upon the clay, sand, or earth underlying the foundations of some well-known great structures. The Cleveland viaduct 14 to 23 lbs. per sq. in. The 1 894 London tower bridge 21 " " The sixteen-story office buildings of Chicago 21 " " The Memphis bridge piers ... 22 " " The Albany capitol 28 " The Brooklyn bridge anchorage 56 " " The earth supporting these structures is, of course, compressed to the greatest degree in its natural forma- tion, but the average pressure of these structures is less than one-sixteenth of the pressure concentrated on an ordinary wagon wheel. 15 CITY ROADS AND PAVEMENTS. Ancient Roman Road, Early Eighteenth Century Road. Late Eighteenth Century Road. Modern Macadam Road. RELATIVE THICKNESS OF ANCIENT AND MODERN ROADS. I6 ANCIENT PAVEMENTS. Paved highways were built by the Romans througli Europe and throughout tlie Empire two thousand to twenty-two hundred years ago, and portions of these pavements still endure. Many of them have been examined to learn whether the details of their con- struction included features which are now worth}' of imitation. It is found that the locations of these roads were usually made in the simplest manner, ignoring natural obstacles and directing the course by straight lines toward prominent landmarks. Upon the lines thus defined, the width of the proposed roadway was then marked by two parallel furrows which were eight feet to twenty feet apart according to the importance of the highway. Between these furrows all unstable materials were excavated, usually to a depth of about three feet, and in this undrained trench the road materials were placed in more or less regular layers. The statitnicn, or base, was formed of one course, or sometimes of two courses, of large flat stones laid in lime mortar, and was usually about fifteen inches thick. Upon this was formed a 9-inch course of small frag- ments of stone which were embedded in sufficient lime- mortar to fill their voids, and which thus bound together the tops of the large stones of the stahcincn : 17 CITY ROADS AND PAVEMENTS. upon this, the nucleus was formed of fragments of gravel, stone, pottery and brick mixed with Hme-mor- tar to form a concrete, which was consoHdated by ram- ming, and was made about six inches thick. Upon this the sum7na crusta (top crust) or pavimeut win (hard surface) was formed of closely-jointed, irregular stones, which formed a mosaic about six inches thick, the top of which was practically on a level with the adjoining natural surface of the ground. In and near the cities \\\^ pavimentiim was formed of larger irregular blocks of basalt, or porphyry or lava, two to two and one-half feet in length and width and twelve inches to fifteen inches in thickness, which were dressed and fitted together with extreme accuracy and were bedded in cement. In a general way there were thus used various ma- terials and varied methods, none of which showed any attempt at drainage of the subgrade, and all of which were wasteful of the materials and labor, which then cost nothing but the lives of captives, who were forced to build these highways for the armies of their conquerors. The results were roads which were remarkable for their strength and durability and for little else. If anyone were so unwise as to attempt to build similar roads now, the cost would be from four to eight times the present cost of our most expensive modern pave- ments which are, in every way, better for modern uses, and upon which the cities of the United States are estimated to have expended half a billion of dollars. STONE WHEEL-TRACKS. This peculiar form of stone pavement has long been in use in the midst of the roughly paved streets of i8 STONK \viii:kl-tracks. many Italian cities and towns, and in sonic of tlic largest Scotch and English cities, which facts probably susr^ested its use on the Albany and Schenectady turn- pike in 1833, \yhen \yheel-tracks, which are still in use, and which are here shown by a photograph taken in 1 90 1, were built on two miles of the worst parts of this main highway to the West, and which Vv'ere later made to coyer the dry and sandy parts of the fourteen miles between the two cities. There are, in 1902, no memories among the oldest residents along the road and no published accounts in local histories, of the origin and details of this interest- ing pavement, and those which are here given were only found by search amidst a mass of old letters and papers which were saved from an abandoned gate- house by Wheeler B. Melius Esq. of the Albany His- torical Society. The turnpike itself was opened to travel in 1805, be- ing made twelve feet wide of gra\'el at a cost of $8,400 per mile. After ten years of attempts to maintain this gravel road under the traffic of many heavy narrow- tired wagons drawn by four or six horses, a "sunken pavement " of cobbles was built on the dry and sandy parts of the road, and broken quarry stone to the depth of twelve inches, was "bedded" on the wet and clayey parts, the edges being "bonded" by lines fifteen to sixteen feet apart, of small boulders twelve inches to twenty-four inches in diameter embedded in the earth along each side. Under date of January 8, 183 1, the President and Directors of the Turnpike Company reported to the Legislature that they had "hitherto been unable to render said road hard and solid and to keep the hard materials (grax'el, broken (|uarrv-stone 19 CITY ROADS AND PAVEMENTS. and cobbles) on the surface of the earth." In April, 1 83 1, strenuous protests were made by the stockholders of this Turnpike Company, Chancellor Kent among others, against the effect of the charter granted in 1826 to the Mohawk and Hudson Railroad Company, on the ground that " Should the Rail Road Company succeed, their operations will necessarily diminish materially the tolls of the Turnpike Company, and thus sap the consideration upon the faith of which the latter have constructed their road." Referring to the application of the Railroad Com- pany for leave to run a side-track into the heart of Albany, Chancellor Kent wrote from New York under date of April 7, 183 1 : "If that would not be an interference with the rights of the Turnpike Company, then nothing would be an interference short of plowing up the Turnpike Road." It was feared that the Railroad might eventually dis- place the stages, the tolls from which formed a large portion of the revenues of the previously-chartered Turnpike Company, then amounting to $5,137 per annum ; one-third of which was paid out to gate- keepers and overseers and the balance was expended in repairs and occasional small dividends: the tolls were levied on a peculiar system by which a four-horse stage paid 43/4 cents to enter upon the road at either end and the same amount to leave it, or 87 cents for each single trip. The steam railroad was, however, built, and was opened to operation on September 12, 183 1, as the first exclusively passenger railroad in the world. The handling of freight by the railroad was not begun till De- 20 STONK WI I KKl. -TRACKS. cember 6, 1832, as detailed in a letter from the manager to the president, when three cords of wood, making two car-loads, were taken to Albany, and were the first freight carried on what is now the New York Central Railroad. In order to compete with the railroad, the Turnpike Company then made many efforts to arrange to build another railroad of their own along the side of the turnpike,* and the failure of these efforts resulted in deciding, in 1832, to lay the "stone rails," of which twenty thousand linear feet were brought from Whalen's limestone quarries at Flint Hill, eight miles up the Mohawk valley from Schenectady, and were laid in 1833 and 1834, and extended later. Sections of this stone wheel-track, in some cases half a mile or more in length, are still in good condition and in daily use, as shown in the photograph made in 1901. The " stone rails " were made four inches thick and were roughly cut eighteen inches to twenty-four inches wide, of any length from two to eight feet, with square ends to be laid close together and with both faces flat to permit of turning over when w^orn. The slabs now show a concave surface worn one to two inches at the center. They were bedded in the gravel and broken stone of the roadway, by two men at the rate of 1 25 feet per day or one and one-half cents per running foot, the cost of the stone delivered ready to lay being thirteen cents per running foot. This made the wheel tracks cost $1,530 per mile while the cobble paving two feet to three feet wide between the tracks and five feet wide on each side of the tracks cost $1,610 per mile: Form- ing the roadbed cost $160 per mile, or a total of $3,300 per mile completed. A few slabs which have Ix'en * Finally accomplished, in 1901-2 by buildintra double track electric road. 21 CITY ROADS AND PAVEMENTS. 5 ft. of large cobble pavement. <^ 6 ft. of trackway. > 18 in. ti)24 in. wide, 4 in lo 5 in. thick. Road from Albany west to Schenectady, X. Y., 1901. Built by Turnpike Company in 1834. 5 in. w iile, 3 in. deep 6 in. thick Road west from Kingston, Ulster Co., X. Y., 1902. Built b}' Turnpike Company in 1S62. STONE WHEEL-TRACKS. 22 STONE WHEKL-TRACKS. broken have from time to time been re})lacecl l3v old blue-stone curbs from Albany. About 1862, a system of similar wheel-track roads was begun in Ulster County, N. Y., when I)a\is Winne built a blue-stone track-way as a toll-road from Kingston eight miles up the Delaware and Ulster Valley to the blue-stone quarries in the Catskill moun- tains. This proved to be so successful that branches, and other roads of the same sort, were soon built and are still in decreasing use. The ease of traction on these smooth slabs led to an increase of the loads drawn upon them, until eight tons has been and is an ordinary load for two horses to bring from the quarries in the hills to the wharves at Kingston and Rondout. Loads of twelve to fourteeii tons drawn by three horses are now of daily occurence, and loads of seventeen tons actual weight have some- times been drawn by four horses : all loads being weighed to determine the tolls. These great loads were formerly carried upon nar- row tires of one and one-half to two inches which speedily cut furrow^s in the hard stones, so that the slabs six to ei^ht inches thick were cut throuHi in three or four years and required renewal. Along the roadsides are now many such slabs cut nearly through and laid aside, w^hile all the slabs which are in use show furrows ranging from one to five inches deep and three to four inches wide. A railroad now parallels and crosses this highway reaching the quarries or passing near them. Wide tires, \vhich are required in the river cities and towns, are used on all w^agons carrying these loads, so that four-inch slabs of blue-stone are now used for renewals 23 CITY ROADS AND PAVEMENTS. of the wheel-tracks and cost ten cents per running foot of slabs twenty-four inches wide. The actual cost of the original wheel-track road built in 1862 was about $3,000 per mile ; the high prices induced by the War increasing the cost fifty per cent over the contract-price made in 1861. 24 MODERN PAVEMENTS. Comparative loads. — In considering the desirability of the different road-surfaces and pavements, it may be noted that a team drawing one ton on a good dirt road can, with the same effort, take two tons over a good macadam surface. Passing from this to a good block- stone pavement, six tons could be drawn as easily, and this load can be increased to eight tons on good wood- block or new vitrified brick, or to ten tons on a bitu- minous macadam or an asphalt pavement. COST OF PAVEMENTS. The following table shows the conditions and costs in 1894 in the 32 cities named, 8 of which had wood- block pavements, 27 of which had sheet-asphalt pave- ments, and all of which had block-stone, six having sandstone, and the rest granite. The conditions and costs in 1901 are shown in detail in the. several chapters. 25 CITY ROADS AND PAVEMENTS. TABLE. Block-Stone. Sheet Wood. CITY AND STATE. Granite. Sandstone . Asphalt. Cedar-block. Cost, Sq. Yard. Cost, Sq. Yard. Miles. Cost, Sq. Yard. Miles. Least Cost. Albany, N. Y $2 90 3 37 1 49 3 90 2 33 $3 12 2 75 3 00 3 30 3 00 3 50 2 90 3 CO 2 54 2 35 3 20 2 55 2 80 2 93 2 75 Allegheny, Pa Atlanta, Ga Boston, Mass 4 II 150 24 Brooklyn, N. Y Buffalo, N. Y $3 25 Chicago, 111 3 00 4 20 3 71 3 40 4 25 2 74 648 $1 10 Cincinnati, Ohi) Columbus, Ohio II 4 Denver, Col Detroit, Mich Kansas City, Kan .... Kansas City, Mo 2 16 26 43 47 63 I 50 I 35 I OS 76 2 90 Milwaukee, Mis 2 Z7 1 b; 2 40 4 75 3 50 2 32 Minneapolis, Minn Nashville, Tenn 2 New Orleans, La 8 52 23 3 65 3 00 2 68 New York, N. Y Omaha, Neb 38 I 52 Oswego, N. Y 2 45 Philadelphia, Pa Pittsburg, Pa 2 41 2 38 2 00 3 25 2 50 3 35 Portland, Me Providence, R. I 265 2 60 Rochester, N. Y J I 90 ^ )3 00 ^ 9 San Francisco, Cal 2 GO 2 05 1 15 3 56 3 20 3 15 2 08 St. Paul, Minn 2 70 2 45 2 50 1 9S>^ 2 25 30 I 10 Syracuse, N. Y Toledo, Ohio 3 00 10 125 Utica, N. Y 2 50 Washington, D. C Wilmington, Del 1 Average of prices $2 90 $2 71 $2 81 • $1 19 PAVEMENTS FOR STEEP GRADES. In selecting a pavement for a given street of which the grade cannot be improved, the choice will often be limited by the fact that the grade is too steep to permit the use of a pavement which might otherwise be preferred. 26 PAVKMKNTS FOR STKKP (;RA1)KS. The most uscfui information on tlic sul^jcct can he obtained from the teamsters and ]u)rsemen of cities in which different pavements on varying grades liave been in use. If it is generally agreed that certain pavements are shunned by teamsters because their horses slip and fall when going down a certain street with a load, it will evidently be unwise to repeat the construction of the same kind of pavement with ec[ual slope in a similar climate. Under the headings of "Asphalt," "Brick," and " Broken Stone," there are given numerous instances of extremely steep grades upon which these pavements are actually built in various cities named. Examina- tions of these may furnish to the observer conclusive reasons for or against copying them, or may suggest changes in detail which w^ould give better results. In examining these steep grades, it should be borne in mind that the selection of a pavement for a given street may have been made directly or indirectly by the prop- erty owners, who have not necessarily chosen the pave- ment best suited to attract traflfic, but w^ho, preferring a quiet street, sometimes select a pavement which trafHc will shun. SJieet Asphalt, — The practical limit of slope for busi- ness streets paved with asphalt is 4 feet per 100 feet, though any slope steeper than 3 feet per 100 feet is not advisable on a main thoroughfare. On residence streets grades as steep as six per cent, are common, and much steeper ones often occur as shown on page 118: The residents accepting th.e incon- venience resulting from a fev\^ da\'S of icy roadway because of the many and great advantages during the rest of the year. 27 CITY ROADS AND PAVEMENTS. On semi-business streets having steep grades, it is a common and good arrangement to lay a sixteen feet asphalt roadway in the center, with an 8-foot strip of block-stones or chamferred bricks, or grooved-joint wood blocks, on each side. In Syracuse, N. Y., on East Genesee street, and on Bellevue avenue, this was done in 1897-8, using Medina sandstone blocks. In some cases where this has been done, the asphalt has been used almost exclusively. Even on flat streets, however, in cold, misty weather, horses slip badly, so that in Washington it is common to remove the shoes from horses in winter because the hoofs slip less. In Brooklyn, on Christmas, i9oi,many delivery-wagon horses were seen with burlaps tied over their hoofs to give foot-hold on the asphalt. There will be parts of two or three days during most winters when this difficulty will occur with both asphalt and brick, both on steep and on level streets unless sand is strewn. Vitrified Brick. — No complaints are made of slip- ping upon grades of five per cent, but these will be more or less slippery as soon as this slope is exceeded, with- out regard to ice. Observations show that horses begin to slip on brick as soon as the grade reaches six per cent, and that for any slope over five per cent it will be advisable to use special brick having a beveled top affording a foot-hold in the joints, which should be filled with asphaltic cement and sharp sand. With this precaution vitrified brick can be used on slopes as steep as are shown on page 98. Creosoted Wood Block, — The same general condi- tions apply to these as to asphalt for the grades less 28 PAVEMENTS FOR STEEP (iRADES. than three per cent, ])rc)\'iclecl sliarp sand is strewn o\'er the surtace when needed, as for asphalt. For grades steeper than three per cent, the special grooved joint here shown in detail is filled with asphaltic cement and coarse sharp sand, and this gives as good a foot-hold as grooved brick. Block Stone. — This may be used in its ordinary form upon slopes less tlian ten per cent, but for this slope and greater, the blocks should have chamfered tops and special joints to give better foothold. The best manner of construction is detailed on page 6i. Broken Stone. — The maximum grade of macadam is fixed rather by the difficulties of maintenance than by conditions which govern the other pavements. Any grade steeper than five per cent offers increased difficulties from the wash of storm-water, although many instances are given on pages 164-166, where these actual steep grades were accepted l^y tlie engi- neers who built these roads as being unavoidable features whicli would ha\e been changed if possil)le. 29 CITY ROADS AND PAVEMENTS. Bititininoiis Macadam. — Aside from the general merits of this new construction described on page 131, bituminous macadam seems specially adapted to meet- ing the difficulties which have heretofore attended or prevented the use of ordinary macadam on steep grades. While it presents the rough surface necessary for a secure foot-hold on steep slopes, it does not give any chance for toe-calks to loosen it or for storm-water to gully it, and these features specially commend it to experienced and critical road-builders like the one quoted on page 13 7. CROWN OF PAVEMENT. The ideal road-surface for a rainless climate would be flat, but the practical road-surface for all weathers must be curved or " crowned," in order to quickly shed water to the gutters. This is the sole reason for giv- ing a " crown," and it is therefore logical to reduce the amount of curvature when the slope of the street gives the needed drainage. To suit the crown to the slope, engineers have made frequent use of the formulae devised in 1898 by Andrew Rosewater, M.Am. Soc. C. E., city engineer of Omaha, Neb., by which the crown is computed for any width and any grade : the amxount of crown decreasing as the slope increases. The 1898 forrauhe are as follows : For Brick, Stone and Wood block := C = }^ {20-f) 1600 ^ For Sheet-asphalt, C = ^ (9-/) C =: crown of pavement in feet, W = distance between curbs in feet, _/= grade of street in feet per 100. 30 CROWN OF PAVEMENT. Standard Crowns i;v For-mii-.k oi" 1S98. For Block- STON E , Brick and Wood-hlock Distance Crown given in hundredths of feet. Curbs Grade of street in feet per hundred. in feet. Level. 1 2 3 4 5 6 7 8 20 25 24 23 21 20 19 18 16 15 25 32 31 29 27 25 24 2 2 21 19 -^ 30 38 36 34 32 30 29 27 25 23 «J 35 44 42 40 38 35 33 31 29 27 C U D ^ 40 50 48 45 43 40 3^ 35 33 30 "«5 45 57 54 51 48 45 43 4"- 37 34 ia 50 63 60 57 54 50 47 44 41 38 00 u; 55 69 66 62 59 55 52 48 45 42 60 75 72 68 64 60 57 53 49 45 r s 65 87 78 74 70 65 61 57 53 49 0-^ 70 S8 84 79 75 70 66 62 57 53 dj 75 94 90 85 80 85 71 66 61 57 IT. 80 100 95 90 85 80 75 70 65 60 For Sheet-Asphali ■ Distance Crown given in hundredths 3f feet. BETWFFV Curbs Grade of street in feet per hundred. in feet. Level. 1 2 3 4 5 20 30 27 23 20 17 13 a; £ tr. 25 38 33 29 25 21 17 -^ 30 45 40 35 30 25 20 ■^ u 35 53 47 41 35 29 23 40 60 54 47 40 34 27 ^ xn 45 68 60 53 45 38 30 ta 50 75 ^7 59 50 42 33 5. J 83 73 64 55 46 37 - > 60 90 80 70 60 50 40 65 98 87 76 65 54 43 ^0 70 105 94 82 70 59 47 (U 75 113 100 88 75 63 50 CO 80 1 20 107 93 80 67 53 31 CITY ROADS AND PAVEMENTS. 1902 /'(^rw?^/^^.— Observations since 1898 have con- vinced Mr. Rosewater that American sheet-asphalt pavements should have the maximum crown practi- cable for traffic, as a means of protection against the standing of water in the small surface depressions. Observation also suggested to him an increase of crown of all pavements on various gradients because, under the 1898 formulae, the pavements on grades varying from three to eight per cent failed to shed water to the gutters quickly enough to prevent freezing in sleety weather, or to avoid its spreading in warm weather. To meet these objectionable conditions, radically different formulae have been devised in 1902 by Mr. Rosewater as substitutes for those of 1898. The \()02 forTHidce are as foiIo7us : For brick, stone-block, wood-block and com-") W (100 — 4^) pressed pAiropean rock-asphalt, - " ) ^°°° For American sheet-asphalt ~) ^ W (100—4 /) }- (composed of sand and asphalt or of compressed . .^q^ natural sand-rock), ---.-' C ^^ crown of pavement in feet, W = distance between curbs in feet, f = grade of street in feet per 100. 32 CROWN OF PAVKMKNT. Standard Crowns by Formll/E of 1902. For Block-stone, Brick and Wood-block Distance Crown given in hundredllis f )f feet. BETWEEN Gurus Grade of street in feet per " lundred. in feet. Level. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 20 33 3^ 31 29 28 27 25 24 ^Z 21 20 19 17 16 15 25 42 40 38 ?>i 35 1>7> 32 30 28 27 25 23 22 20 18 30 SO 48 46 44 42 40 38 36 34 32 30 28 26 24 22 35 'IS 56 54 51 49 47 44 42 40 Zl 35 'i2> 30 28 26 40 67 64 61 59 56 53 51 48 45 43 40 31 35 32 29 45 7S 72 69 66 63 60 57 54 51 48 45 42 39 36 33 50 83 80 n IZ 70 67 63 60 57 53 50 47 43 40 31 55 92 88 84 81 11 IZ 70 66 62 59 55 51 48 44 40 60 100 96 92 88 H 80 76 72 68 64 60 56 52 48 44 65 108 104 100 95 91 87 82 78 74 69 65 61 56 52 48 70 117 112 107 103 98 93 89 84 79 75 70 65 61 56 51 75 121; 120 III 1 10 IDS 100 95 90 85 80 75 70 65 60 55 80 133 128 123 117 112 106 lOI 96 91 85 80 75 69 64 59 For Shket-Asphalt Distance Crown given in hundredths of feet. BETWEEN Curbs Grade of street in feet per hundred. in feet. Level. 1 2 3 4 5 6 7 8 9 10 11 12 20 40 38 31 35 34 32 30 29 27 26 24 22 21 25 SO 48 46 44 42 40 38 36 34 32 30 28 26 30 60 58 55 53 50 48 46 43 4' 38 36 34 31 35 70 67 64 62 59 56 53 50 48 45 42 39 36 40 80 11 74 70 67 64 61 58 54 51 48 45 42 45 90 86 83 79 76 72 68 65 61 58 54 50 47 50 100 96 92 88 84 80 76 72 68 64 60 56 52 55 1 10 106 lOI 97 92 88 84 79 75 70 66 62 57 GO 120 115 1 10 106 lOI 96 91 86 82 11 72 67 62 65 130 125 120 114 109 104 99 94 88 83 78 13 68 70 140 134 129 123 118 112 106 lOI 95 90 1 84 78 13 75 150 144 138 132 126 120 114 I08jI02 96, 90 84 78 80 160 154 147 141 134 128 1 22 115 109 102 96 90 83 ?>?> CITY ROADS AND PAVEMENTS. Under the heading of "Asphalt," pageiiS, and " Brick," page 95, will be found the record of the actual present practice for crown on level grades and 30 feet width in the cities named. Form of Crowjt. — The form of crown should be a parabolic curve nearly flat at the center, for traffic, and sloping more quickly toward the sides, for drainage. When the amount of crown has been computed from a formula or a table, or when an experienced engineer has preferred to determine it arbitrarily, as is very often well done, the form of the curve can be determined thus for any width or crown : divide the space from center to curb into twelve equal parts. Take the center ordinate, or total "crown," as unity; then the successive ordinates, measured up from the base-line, will be: At center, i.oo, .99, .97, .94, •89, .83. -75. -66, .55, .44, .30, 16, .0 at curb. Or stretch a line from curb to curb on level with the center, and measure down the corresponding amount. Thus if the width is 30 feet from curb to curb, and the crown has been determined to be half a foot, the ordi- nates measured down at intervals of i % feet will be in inches and decimals. At the center o inches — 0.06, 0.18,0.36,0.66, 1.02, 1.50, 2.04, 2.70, 3.36, 4.20, 5.04, 6.00 inches at curb. This shows a side-slope of about five per cent on the third next the curb. These fig- ures may be useful in making a template for fixing the curve of a pavement-surface, or for forming the sand-cushion of a brick pavement as described on page 95- For Macadam, it is usual to consider that the con- ditions to be met are reversed, and it being necessary to prevent storm-water from following the road-surface, 34 CITY ROADS AND PAVEMENTS. the " crown " for macadam is increased as the slope increases; one-half inch per foot being usual on level grade, and a maximum of three-quarters inch per foot on steep slopes, increasing to one inch on excessive slopes. This produces in theory a ridge in the center, with a straight slope of 5 ^ inches on each side for a level 22 foot roadway. But in practice, the roller flats the central " ridge " down, and produces a curve which is flat in the center and slopes most at the sides, which is the form desired. FALLS ON DIFFERENT PAVEMENTS. As to the relative liability to accidents from slipping of horses' feet upon different pavements, observations were made for Captain (now General) Francis V. Greene, M. Am. Soc. C. E., during a period of six months on thirty-six various streets in ten different cities, viz.: New York, Philadelphia, Chicago, Boston, St. Louis, New Orleans, Washington, Buffalo, Louisville and Omaha. The result of these observations, and of similar ones made by Col. William Haywood, M. Inst. C. E. in London, by George F. Deacon, M. Inst. C. E. in Liverpool and by French engineers in Paris, were read before the Am. Soc. C. E. on December 16, 1885. Over 800,000 horses and 81,000 miles of travel were observed in the ten cities of the United States, with the result of showing that a horse may travel, for each fall that occurs — 272 miles on wood-block pavement. 413 miles on granite-block pavement. 583 miles on sheet-asphalt pavement. These results in the cities of the United States dif- fer radically from those obtained for Colonel Haywood, 36 CULVKRTS. in London, wIktc it was required that liorses should be sniootli-sliod, instead of liaving tlie sliarp toe-calks which are generally used in the United States, and where European rock-asphalt is used instead of Ti-ini- dad asphalt and sand. The results observed in Lon- don were — 446 miles on wood-block pavement. 132 miles on granite-block pavement. 191 miles on sheet-asphalt pavement. CULVERTS. To carry water beneath a roadway, culverts are variously built of cast-iron pipes, of masonry, of concrete and of double-strength vitrified pipe. The bottom-line of culverts is usually fixed at the bottom-grade of the side-ditches so that the available height is limited, and large waterway is often obtained by using two, and sometimes three, parallel lines of 18, 24 or 30-inch ])ipes. If the ditch drains a hillside having a southern exposure, the midday sun of winter will supply a trickle of water which will freeze at night, and under this con- dition such pipe culverts will soon freeze solid and sometimes burst. For most conditions, box-culverts of rubble masonry or of monolithic concrete with embedded expanded metal in the covers, are much preferable to pipes, being less ready to freeze and less liable to be dama^^ed if frozen. For equal areas of waterway and depending upon the local conditions of stone-sup]:)ly and freight rates, the relative costs will usually be in the order fu'st named above. When the span of a masonry culvert is two feet or more and 6-inch to S-inch cox'er-stones are used, thev 37 CITY ROADS AND PAVEMENTS. should be carried on suitable I-beams placed two feet centers, in order to carry ordinary traffic safely. If there is height enough a rough stone arch may be best and cheapest. CURBS. Curbs should be set or re-set before beginning the pavement of which they are a necessary adjunct. The trench for the curb should first be cut and graded, and sub-drained if needed, and if concrete foundation for the curb is proposed, the curb-stones should be accurately aligned and graded upon fragments of stone, around and over which the concrete is to be formed and tamped : the pavement-base, if any, and the pavement itself being afterward formed against the face of the curbs. Curbs are used of various materials which are some- what as follows for the different sections of the United States; there being noticed a general tendency toward the use of concrete. Kinds.— ¥ or the New England States, granite and also concrete. For New York and the cities along the Hudson and the coast, and for Washington in part, "bluestone" (a tough sandstone) from Ulster county, N. Y., and limestone and also concrete, of which there was built 202 miles in the Borough of Brooklyn during 1900. For central, southern and western New York, and for adjacent Ohio and Pennsylvania, Oxford " blue- stone," from Chenango county, N.Y., and Medina sand- stone, from Orleans county, N. Y., and limestone, and also concrete. For the western and southern cities, granite, and sandstone from Kettle River, Minn., and from Berea, Ohio, and from Colorado, and also concrete, the latter 38 CURBS. being mucli used in Chicago, St. Paul, and Cleveland. Brick curbs are used with brick pavements in Louisiana and Texas, and have been observed in two northern towns in connection with brick gutters for macadam- ized streets. These were special brick, 2^-inch by 4^-inch by 8>^-inch, with one corner rounded, set on end upon concrete with the edge toward the road- way and showing 4>^ inches above the paved gutter: they seemed to be poor substitutes for stone or con- crete, as the material is unsuited for the purpose : this opinion is confirmed by Willis Fletcher Brown, con- sulting engineer of Toledo, Ohio, whose extended experience with brick pavements is well known. Sizes. — The dimensions of stone curbs vary in the cities from sixteen to twenty-four inches for depth, five to six inches for thickness, and three to five feet for length. The top is always beveled to take the slope of the sidewalk to the gutter. Coo c rate A^phQlt pavement with CornbinecJ c<^rt) and guttfei* Concrete curb is usually mioulded in place in uniform lengths, varying from four to ten feet, preferably five feet, with }i inch joints formed by the removal of tem- porary steel templates. It is often made in combination with a 1 2-inch to 15-inch gutter, and it is recent and good practice to add a cast iron or a steel guard-strip or " rub-strip," anchored two inches into the concrete by a 2-inch by ^-inch perforated web, and showing a 39 CITY ROADS AND PAVEMENTS. rounded flat surface of i >^ to 2 inches on the outer top edge, to protect against the impact of wheels. Corners are usually curved on radii varying from four feet to nine feet; the former preferred for streets of moderate traffic. COST. Straight curbs set cost about as follows, with thirty per cent to fifty per cent added for curves: — Granite, 50 cents to 90 cents and in some cases $1.25 per linear foot. Ulster or Oxford bluestone, 40 cents to 80 cents and in some cases ^i.oo per foot. Medina or Berea sandstone 35 cents to 70 cents. Concrete usually costs from 40 cents to 50 cents, with 35 cents added for a combined gutter, though combined curb and gutter have been built for 50 cents. The prices vary widely with the freight-rates and the local conditions. CAR TRACK CONSTRUCTION. When any of these pavements are to be built on a street containing car-tracks, special attention must be given to the reconstruction of the track and to the details of the pavement next to the rails. The pave- ment between the rails, and for two feet on each side of them, should be built by the railroad company under the plan and direction of the city engineer, or this should be done by the city at the expense of the rail- road, as in Rochester, N. Y. The methods there used in 1900 are shown in the picture here given. This construction with heavy rails is necessary to make the track-structure as rigid as possible, and this is so well accomplished in 1901 that sheet-asphalt is 40 CAR TRACK CONSTRUCTION. laid in actual contact with both sides of the rails, upon which exceptionally heavy cars pass without cracking the asphalt. This is seen at the best in Huffalo, N. Y., where the rails are electrically spliced in place, by wielding three-inch by one-inch by fifteen-inch steel plates on both sides of each joint, forming continuous ninety-pound rails for great lengths. Joints are cast with molten iron with similar effect at Chicago, Brook- lyn and Minneapolis, and many other cities where the authorities and the railroads work together to get the best results in their pavements. TRACK AXD PAVEMEXT COXSTRUCTIOX, ROCIIEvSTER, X. Y., t.xx). Medina sandstone block pavement on six-inch natural cement concrete base, and trolley-railway track-construction on concrete foundations. Three-inch porous tile beneath concrete and leading to sewers ; Ties two-feet centers, on concrete five inches thick, with twelve inches of concrete between the ties ; Xine-inch full-grooved steel girder-rails, bonded, resting upon the ties and upon twelve inches of concrete between the ties. 41 CONCRETE BASE FOR PAVEMENT. A concrete base, four to six inches thick, is desirable, whether the wearing-surface is to be of asphalt, or of creosoted wooden blocks, or of vitrified brick, or of stone blocks. The wearing-surface will need repairs and renewals, but a properly-made concrete base will be permanent, and will always increase in strength and solidity. It is specially needed wherever the street is of recently made ground, or where it was formerly swampy or unstable, or where traffic is expected to be heavy, unless an old stone pavement is in place to serve as a substitute. SUBGRADE. Before forming the subgrade to receive the concrete base, all present and prospective sewer, water and gas and subway connections should be made and extended under the curbs, and all old and new trenches should be tested with a ten-ton roller, and depressions should be filled and wetted and tamped until solid. HYDRAULIC CEMENT. The manufacture of American Portland cements has increased from one-third of a million barrels in 1890 to ten million barrels in 1900, and the manufacturers have meantime raised their standards, improved their pro- 42 CEMENT TESTS. ducts and reduced their prices to keep pace with tlie growing demand for the highest grades which were formerly only made abroad. The differences in price between the high-grade reliable cements and the low-grade uncertain ones are comparatively small, and the poor cements will disap- pear from the market when all engineers make tests and are guided by the results. Good natural cements are still much used, as appears from the table at page 56, and they are better than low-grade Portland cements, as w^ell as being cheaper. CEMENT TESTS. The engineer of a small city will seldom have time or outfit for the complete tests now usual on large works, for which there are needed a special man with an expensive equipment installed in a separate room. The following described simple tests can be made by the engineer himself, with an outfit costing not over four dollars and which can be stored in a desk pigeon- hole. The tests thus made will be interesting in them- selves, and will be effective and convincing aids in rejecting most bad cements which may be offered, and will also have the preventive effect of causing manu- facturers to send their lower grades of cement else- where and to send only their best products to the places where such tests are probable: — First. — For fineness. — Sift three to four ounces of cement through a standard test seive of 100 meshes per linear inch. Reject cement of which ten per cent by weight is retained on the seive. This is conserv- ative and the limit may be made smaller, for many Port- land cements are now in the market which will leave 43 CITY ROADS AND PAVEMENTS. less than four per cent. A test by 200-mesh seive with a thirty per cent hmit is desirable but takes time. Second. — For qztickness of setting. — Make a pat of four ounces of neat cement adding one-quarter to one- fifth its weight of water and making a putty-like ball which can be dropped on the table and retain its form without falling to pieces. Press this upon a three bv four inch glass plate leaving it half an inch thick in the center and sloping to thin edges all around. Note time required to take initial set. Reject cement which sets in less than twenty-five minutes. It may take three hours or more, but it will be better for paving if it sets in one hour. The instant of " initial set " is determined by noting when the surface will support a four-ounce weight resting upon the smooth flat end of a one- twelfth inch diameter wire. Third. — For soundness. — Use the pat on glass above described and note when it sets enough more to make it difiicult to indent it with the thumb nail, or when it will support one pound on the smooth flat end of a one- twentv-fourth inch wire, which mav be considered as indicating " a hard set." Then put the pat with its glass plate over boiling water until the steam has heated them, and then immerse and keep them in the boiling water for three hours. Reject Portland cement if the pat shows radiating cracks in the center, or shows blow- holes on the surface, or curls up from the glass or cracks at the thin edges. Good natural cements may fail to en- dure this test (which is a severe one), and it may prop- erly cause the rejection of some Portland cements which would endure it after being " air-slacked " or " seasoned." Fourth. — For purity. — Provide a glass-stoppered bottle of muriatic acid ; two shallow white bowls or two 44 CEMENT TESTS. half-inch by six-incli test-tubes, a glass rod and a })air of rubber gloves. Put in a bowl or a tube as much cement as can betaken on a nickel five-cent piece; moisten it with half a teaspoonful of water; cover witli clear niuriatic acid poured slowly upon the cement while stirring it with the glass rod. Puix Portland cement will effervesce slii>:htlv and will give off some pungent gas and will gradually form a bright yellow jelly without any sediment. Powdered Iiniesto7ie or powdered cement-rock mixed with the pure cement will cause a violent effervescence, the acid boiling and giving off strong fumes until all the carbonate of lime has been consumed when the bright yellow jelly will form. Powdered sand or qnartz or silica mixed with cement will produce no other effect than to remain undissolved as a sediment at the bottom of the yellow jelly. Reject cement which has either of these adulterants. Poz^dered slag mixed with cement unfits it for pave- ment-work. The adulteration is indicated in the dry cement (when coloring matter does not conceal it), by a lilac tint, and it is also indicated on the surface of a test-pat after drying, by brown and green and yellow discolorations. A chemical test will show the presence of slag if made as follows : Provide an ounce of mixture of methylene iodide (C H3 L) and benzine, in which the methylene (the specific gravity of which is 3.'^' being the heaviest organic liquid) is reduced to the specific gravity of 2^^ bv addition of benzine. The methylene is uncommon and costs a dollar an ounce. 45 CITY ROADS AND PAVEMENTS. In a half-inch test-tube put half an inch of the dry suspected cement and pour in a little of the mixture, stirring to a thin grout. Then cork the tube and let it stand. If slag is present, it will remain at top while the cement will settle to the bottom. The separation can- not be seen if coloring matter is present. Coloring matter in any cement will show itself in the acid test by giving a black or gray color to the resultant jelly which would otherwise be yellow. The coloring matter may, or may not, be injurious in itself, but its presence shows that the manufacturer wished to dis- guise the cement, which should be rejected, because there are a plenty of good cements which need no disguise. Weight. — The several kinds of cement differ mate- rially in weight and any cement that varies much from these average weights should be examined specially. The standard barrel contains 3.65 cubic feet and the standard bag is one-fourth of a barrel. The average weight of a cubic foot of packed cement is : Portland, 104 to 114 lbs. ; puzzolan, 90 lbs. ; natural, 75 to 82 lbs. for Eastern and 70 to 72 for Western : The average net weight of each per barrel being 375 lbs., 330 lbs., 300 lbs. and 265 lbs. RESULTS. These tests will be conclusive as far as they go, and will cause the rejection of no good cements. The makers of high-grade cements would not object to these requirements and would not increase the price because of them. 46 AC.C.RKC.ATES. ISK OF CEMENT. The cement in bags or l^arrels slioulcl he deli\'ere(l and stored in a tight shed two feet off the dry ground. Blending. — The cement should never be used di- rectly from any original barrel or bag, because there may be more or less damaged or defective packages, each of which would thus form a bad spot in the work. This chance is wholly avoided by requiring that the contents of five packages shall always be blended dry in the cement-shed before any is sent out for use, and that only this blended product shall be sent out of the shed into the work. This will not add to the cost, but will merely keep the cement-man busier. AGGREGATES. The aggregates may be crushed from the cheapest stone available, though the hardest and toughest is preferable. Special care is necessary to see that the stone, before crushing, is clean and free from mud and clay. Stone unfit for masonry, or for macadam, may serve the purpose when it shall be embedded in the matrix of mortar in the concrete. Crusher-dust as " sand." — The total product of a crusher passing through a 2>^-inch screen will give the best results, provided that the crusher-dust is consid- ered as sand, and that proper allowance is made for its presence after determining its quantity. If the stone before crushing is not entirely clean, the crusher-dust should be excluded by screening. Clean gravel and sand may be used in lieu of stone with the same provision as to the included sand. 47 CITY ROADS AND PAVEMENTS. Where neither stone or gravel is available, as in the middle West, fragments of brick or of furnace-slag are often used as aggregates. In any case, the number of cubic yards of loose ma- terial for the aggregate will be twelve to twenty per cent more than the total cubic yards of concrete ram- med in place. SAND. The sand should be the sharpest and cleanest avail- able, preference being given to pit-sand, of which the grains vary from fine to course. It will be well worth while for the engineer to examine the various sources of supply, and to be as careful in its selection as in the selection of the cement which is to be mixed with it. In a recent case, sand, which seemed fairly good, w^as washed and was then found to make concrete which w^as one-third stronger than when the sand was used in its natural state. Sand containing five per cent of loam or of clay is common and should not be used until washed. Two per cent will retard the set and per- ceptably weaken the mortar. PROPORTIONS AND MIXING. The proportions measured in loose bulk should be one part Portland cement to three parts sand to six parts of the aggregate, or one part natural cement to two parts sand to four parts of the aggregate. (See table at page 56.) When the concrete is made by hand, the blended dry cement, described on page 47, should be mixed on a mortar-bed while dry with the due proportion of dry 48 WATER. sand, until the color is uniform and no streaks of cement can be noticed when the dry mixture is smoothed with the back of a shovel. Water (equal in weight to eleven to twelve and a half per cent of the weight of the sand and cement for Portland cement and fifteen to seven- teen per cent for natural cement) is then added gradu- ally while mixing until plastic mortar is formed. Meantime the rest of the men are measuring, sprink- ling and spreading the aggregate in a four-inch layer upon the platform (for which a sheet of iron ten feet square is the best), and on top of the layer is spread the mortar, when the whole is turned with shovels by four men while two men work between them with specially large hoes. This mixing is continued until every face of every particle and fragment is perfectly coated with the mortar, requiring hard w^ork which must be done rapidly. W\\TER. It is not important whether the mixing- water is pure, but it should not be muddv. The required amount of water should vary, as the aggregates are more or less moist, so as to give a uniform result, for to be either too wet or too dry is a grave defect in concrete. There is the widest difference of opinion among engineers of large experience as to the degree of wet- ness which gives the best results. All are agreed tliat the surplus mortar must be brought to the surface by ramming, after filling all voids. The effectiveness of ramming will vary on different works; the ease with which the mortar is brought to the surface increases with the amount of water, up to the condition where 49 CITY ROADS AND PAVEMENTS. the concrete is so wet that no ramming is needed; which is bad practice, but not uncommon. The best practice is to use the least water with which the available rammers can be made to bring the mortar to the surface. It is futile to try to secure this neces- sary result by the persistent ramming of concrete which has been mixed too dry, and which it were better to remix with more and wetter mortar. There should never be enough water to produce free grout, which can drain away into the subgrade and be lost. MACHINE MIXING. Concrete is made better and more cheaply by any of the various rotary mixers than it can ever be made by hand. It is poor practice to depend upon shovellers to proportion the materials, as is often done with continu- ous and with gravity mixers. The proportions should always be accurately measured. Mechanical mixers, operated by steam power, are best adapted to large con- centrated masses like dams, foundations and bridge- READY TO LOAD. LOADED abutments, but are not w^ell adapted to forming a thin layer spread over a large area, like a pavement-base. This condition is particularly well met by a new device known as a "dromedary mixer," which consists of a two-wheeled cart of which the body is a cylinder, which turns with the wheels as the cart is hauled along. 50 SPREADING AM) RAMMI\(;. The proper amounts of cement, sand, stone and water, are put into tlie cylinder wliich is closed tightlx", and then the cart is hauled to the work where the ])er- fectly mixed concrete is dumped in place and spread. DUMPING The machine is described and highly commended by the city engineer of Baltimore, Charles E. Phelps, in the Municipal Journal and Engineer, of December, 1 90 1. jT^'^. CLOSING SPREADING AND RAMMING. Set eight-inch boards from curb to curb, supported on edge by stakes, and enclosing a space five feet wide, within which spread the concrete in a loose layer about 1% to 7^ inches deep, for a six-inch base, so that a one-yard batch will fill about one-third the width of a thirty-foot pavement. Ram it at once vigorously until all voids are closed, when the surplus mortar will come to the surface and the mass will quake slightly under the rammers. Effective ramming is hard work at which a workman should not be kept for more than an 51 CITY ROADS AND PAVEMENTS. hour, when he should be changed to wheeHng or turning. MonolitJi. — Each day's work must be a monoHth. The spreading and the ramming must be so done that each successive batch shall be rammed before the pre- ceding and the adjoining batches have begun their first set. The stiffness of the concrete after ramming in place must be such that the fresh mass will retain its form and will not crumble when the boards are removed preparatory to filling the adjoining space. Properly managed there will be no lines between the batches, which will all be merged into one mass. Bond. — Each day's work can also readily be bonded with the base previously formed, so that the whole will be a monolith. Form the end of each day's work on a steep two-on-one slope, or with a three-inch step and vertical rises, and have the surfaces of the end show voids between the fragments of embedded stone to afford a good bond. When work begins the next day, prepare a pail of thick grout of clear Portland cement, and brush it freely over and into the voids of the exposed end, just before dumping the fresh concrete against it. The result of omitting these small precautions, and of making a flat slope at the end of each day's concrete- work has been known to show, a year afterwards, in well-defined waves of an inch or more in height, ex- tending from curb to curb of an otherwise perfect asphalt pavement. These waves being resultants of a slight expansion, or "growth," of the concrete which slide upward at all the places, two hundred to three hundred feet apart, where the concrete-work for each day had ended. 52 SETTIXC;. SURFACE. If it is desired to " float " the surface smooth, as is required for pavement-base in Paris, and in Sidne}-, N. S. \\\, and for curbs and gutters and for accurately- cut wood-block pavements in the United States, the surface may be formed of the matrix-mortar without the embedded stone-fragments. It is of the first im- portance that this surface shall be of the same mortar as the matrix of the mass, and be placed at the same time and thoroughly blended with it, and that it shall not be made of a different or better kind or proportion of cement, nor be spread afterwards as a plaster to cover a porous or rough surface. Concrete which is consid- ered to need plastering should rather be taken out and replaced by good work. SETTING. WMien concrete has been rammed in place, it must be kept entirely undisturbed until it sets firmly, which should take from four to seven days ordinarily and longer in cold weather. ^?/. — It is of vital importance that the concrete should be kept wet during all this time, and that it be sprinkled freely at night and morning, and be covered from the sun by sand or canvass which will retain the water. It is a common thing to find experienced foremen who fully believe that concrete should ''dry out," and many pieces of otherwise good concrete have been ren- dered worthless by acting upon this idea which ignores the plain fact that "hydraulic" cement requires water. Traffic of all kinds, both by foot or by vehicles, should be kept from the concrete-base for at least a week if 53 CITY ROADS AND PAVEMENTS. possible, using planks to cover street-crossings where passage-ways must be permitted. FREEZING. Portland. — For any concrete likely to be soon ex- posed to frost, use Portland rather than natural cement, and if possible avoid making concrete at all during cold weather. Avoid very slow-setting cement for such work, and especially avoid using sand or gravel con- taining loam or clay, of which even two per cent will greatly retard the setting of any cement with which it may be mixed. Use a little more cement and a little less water than in warm weather. Make special effort to prevent the concrete from freezing, at least until it takes its first set, and, if possible, for several hours afterwards, and also prevent it from thawing after it has frozen. While mixing, keep a fire burning in the sand pile and another in the stone pile, and heat the mixing- water. Brine. — Use brine by making a barrel of saturated solution of salt, in which keep a layer of free salt show- ing in the bottom ; put one-tenth of the contents of this barrel, dipped from the bottom, into each barrel of fresh water heated for mixing. It is useless to provide easily broken salometers which the foremen will not use, as this simple plan more readily provides a ten- per-cent solution, which will retard freezing and which will not injure Portland cement concrete, and which, in some cases, will even increase its strength. Limit. — Stop work when the cold reaches twelve degrees of frost or 20° Fh. If each and all of these precautions be observed, good results will be obtained, but at greater cost than for work under the normal conditions which are the basis of the following table. 54 COST. COST. The present cost of concrete in cities was compiled in 1 90 1 in an unusually effective way by F. V. E. Bardol, M. Am. Soc. C. E. and chief engineer of department of public works of Buffalo, in the following table which is republished from " Municipal Engineering." These figures and this table do not include the four- inch base for five miles of sheet asphalt pavement built during 1895 to 1899, in the city of Niagara Falls, N. Y., by Walter Jones, city engineer, in proportions of one Portland cement, five sand and ten stone, at a total cost per cubic yard, in 1897, of ^4.00. The items were: i-io cubic yard (or 68^ of a 4-foot barrel) of high grade Port- land cement, at $1.75 per barrel $1 20 5-10 cubic yard of graded pit-sand, fine to coarse, at $1.10 per cubic yard 55 I cubic yard of crushed and dust-screened limestone at $1.25 per cubic yard i 25 Mixing and placing and ramming " dry "-mixed concrete, one cubic yard i 00 Total per cubic yard , $4 00 The results were good. Portland Cement, — Of forty-two cities, one-third use Portland cements in the proportions of one cement, three sand and six to seven stone or gravel, at an average cost, for twelve cities, of $5.30 per cubic yard. Natural Cement. — Two-thirds of these forty-two cities use natural cements in the proportion of one cement, two sand and four to five stone or gravel, at an average cost, for sixteen cities, of $3.85 per cubic yard. 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OJ 0) 3 *^ ja •n t. >TJ u J3 a >> u Oi 0. a >> u 0. •a -^ « so ca 3 «•£ u o . *^ *^ o TJ o 0) n em o 11) a 3 -0 a « a. ^ © ■^ u ao o a Sf i^ E B 3 fo E M o 3 a n J3 rr aa 0) 0) a .x B a. a s a s B 2i -n D 2 "o 3 O □ w fa 3 a a a 1) u O 30 • H o < 56 BLOCK-STONE PAVEMENTS. Block-stone pavements are forms of tlie most ancient pavements, the details of which have been adapted to the conditions of modern city traffic. Examination of the conditions in the great cities which do the best street-work, and which employ the best skill to plan and to execute it, shows that block- stone pavement of all kinds have long been regarded as necessary evils which have only been tolerated because they were improvements on the barbarous cob- ble-stone pavements which formed the first stepping- stones out of the mud, and because better substitutes were lacking. There have been obvious advantages w^hich have off-set the evident disadvantages, thus inducing a more general use of block-stone than is now necessary. Block-stone pavements are now only desirable for steep grades, or for those streets of the largest cities where the heaviest traffic exists. There is no such traffic in any city of moderate size. It has been considered until recent years that blocks of the hardest trap rock, or basalt, or granite were best adapted to endure the class of traffic which required block-stone, and vast sums have been spent in ]:)rcpar- ing and laying blocks of granite from Massachusetts, 57 CITY ROADS AND PAVEMENTS. Clermoxt Avenue, Brooklyn, N. Y. Paved about iSSo. Eighth Avenue, Brooklyn, N. Y. OLD COBBLE-STONE PAVEMENTS. Jan. I, 1901, New York City (^Manhattan) had 227 miles of cobble. Brooklyn had 300 miles of cobble and defective blocks. 58 BLOCK-STONE PAVEMENTS. Maine and Vermont, and of diabase trap rock from tlie Palisades of the Hudson. Pavinof blocks formed of these rocks and laid in the usual manner with sand joints, wear in such a way that their tops become rounded and polished, giving a poor foothold for horses, and forming a surface which collects and retains filth, and causes noise, and is injurious to public health and comfort : the hardest and finest- grained rocks giving the worst results, so that the coarser grades of granite have nearly displaced trap rock for paving blocks. i^"^!±£d dond Cone ret*. Granite povement Broadway, New York, has very heavy traffic and has been repeatedly paved, from Fifty-eighth street to the Battery, five miles, with various forms of granite and of trap blocks ; portions of which have needed relaying after three years' use, and all of which have been dirty and noisy. These conditions are shown to be unnec- essary by the fact that during 1900, this block-stone pavement was re-set and used as the foundation for noiseless sheet-asphalt, which can be kept clean, and which is guaranteed to be in perfect condition during and at the end of ten years. This was done from Fifty-eighth street to Fourteenth street, two and a half miles, (and also on sixty other streets in New York,) during 1900, and has been extended to Canal street, 59 CITY ROADS AND PAVEMENTS. Metn.politan Op^ra H. BROADWAY, NEW YORK, 1900. Looking up from the Casino at Thirty-ninth Street. After paving- with sheet-asphalt, in 1900 : Trinidad Lake wearing-surface ; Bermudez Lake binder-coat. 60 BLOCK-STONE PAVEMENTS. one and one-fourth miles, during 1901, and in 1902 will be continued one and one-fourth miles to the foot of Broadway at the Battery. Many other cities of the ' United States have, during the. past ten years, preferred to use sheet-asphalt or brick rather than granite blocks, I. with the result that the total annual expenditure of the cities of the United States for granite block pavements has decreased one-half since 1890. The ill results obtained from pavements of granite and trap blocks are much less marked when the pave- ments are formed of blocks of Medina, N. Y., sandstone or Kettle River, Minnesota, sandstone. These sand- stones wear flat, do not polish, and approach granite in their resistance to crushing force, as indicated by the followTng statements of average pounds of crushing force endured per square inch : — Maine granite, 15,000 to 22,000 pounds; Quincy granite, 19,500 pounds; average of several of the New England granites, 22,000 pounds; Palisades diabase trap, 19,700 pounds; Medina, N. Y., sandstone, on bed, 1 7,500 pounds ; Berea, Ohio, sandstone, 10,250 pounds ; Oxford, N. Y., blue stone (sandstone), 13,470 pounds; Kettle River, Minnesota, sandstone (after seasoning), on bed, 12,300 pounds. Paving blocks of Medina sandstone are used to the largest extent in the cities of Rochester and Buffalo, N. Y., and Cleveland, Columbus and Toledo, Ohio, and are quarried along both sides of the Erie canal in various places from thirty to fifty miles west of Roch- ester, N. Y. The methods are particularly good in Rochester and in Cleveland, where the best pavements are laid on concrete foundation. At Rochester, the half-inch joints are filled with hot coarse sand and hot 61 CITY ROADS AND PAVEMENTS. Setting Medina sand-stone blocks on six-inch concrete base coveioi wiiii une and one-half inches to two inches of sand-cushion. Filling joints with coarse sand and hot paving cement. BLOCK STONE PAVEMENT, ROCHESTER, N. Y., 1900. 62 B LOC K-STON E 1 ' A \' K M K NTS. pa\ing cement. '1 lie i^axcmcnts arc built b\' Edwin A. Fisher, M. Am. Soc. C. E., as city engineer, and the results are the best of which the material is capable, at a cost, in May 1901 of $2.48 per scjuare }ard com})leted including six-inch foundation of Portland cement con- crete. At Cleveland, Ohio a similar pavement is built with close joints. Paving blocks of Kettle River sandstone are used in in Saint Paul and Minneapolis, Minn., and are quarried at Sandstone, Minn., about one hundred miles north- east of Minneapolis. The method of construction and the results are similar to those at Rochester, N. Y., the joints being half an inch wide and being filled with equal parts of Portland cement and sand. The cost at St. Paul in 1900, including six-inch concrete base, was $2.45 per square yard completed. 63 CITY ROADS AND PAVEMENTS. The following table shows the relative use of several kinds of block-stone pavements in various cities : — Mileage of Block Stone Pavements (on basis of 30 feet width or 17,600 square yards per mile). CITY. Albany Atlanta Boston Buffalo Chicago Cincinnati . . . . Cleveland . . . . Columbus . . . . New York: Brooklyn . . . Bronx Manhattan . Queens . . . . Richmond. . Philadelphia . . Richmond. . . . Rochester . St. Louis St. Paul Toledo Troy Washington . . . state. N. Y. . . Georgia. Mass. . . N. Y. .. Ill Ohio... Ohio... Ohio... N. Y. .. N. Y. . . N. Y. . . N. Y. . . N. Y. .. Pa Va N. Y. .. Mo. ... Minn. . , Ohio... N. Y. . . D. C. .. i Year, j 1902 1902 1902 1899 1890 1902 1900 1900 1902 1902 1902 I901 I9OI 1902 1902 I90I 1902 I90I 1902 1902 1900 Granite. 28 miles 52 miles 114 miles 21 miles 58 miles 2 miles 146 miles 44 miles 192 miles 29 miles y2 mile 340 miles I mile* 70 miles 26 miles 28 miles Diabase Trap. 2 miles I mile 7 miles 87 miles 7 miles y\j- mile 3 miles Sandstone. 108 miles 121 miles 7 miles 31 miles 3 miles 6 miles * Also 31 miles of "granite spalls." 64 WOOD BLOCK PAVEMENTS. 1 i C iJ o r. c "S O o O c < is Pti ',J 65 WOOD PAVEMENTS. Wood-block pavements, as built since 1900, surpass others in freedom from noise, and rank among the best in qualities and in cost. Of the many forms of wood pavements which have been built, only those need be described in detail which are still in actual construction : brief descriptions being given of the cheaper forms, which are only regarded as temporary expedients, and fuller details being shown of those latest and most improved forms of wooden block pavements which are now ranked with the best class of modern work. The corduroy roads of a century ago are now best known in the tales of our grandfathers, although there can yet be found, crossing swamps on the line of the old military road which was built in 1 8 1 2 across the Adirondack wilderness, from the Mohawk valley at Schenectady to Ogdensburg on the St. Lawrence, and to Sackett's Harbor on Lake Ontario, sections of corduroy road, which are still as sound as when laid, having been preserved from decay by the water which has usually covered them, although huge forest trees have meantime grown up in the old and abandoned roadway near at hand. The plank roads of a half century ago are nearly gone, with the toll-gates which were the objects of their beginning and the cause of their ending ; though it is of 66 ROUND CEDAR lU.OCK. curious interest tliat tliere are still, in 1902, two plank roads leading from the westward into the city of Albany, N. Y., having five toll-gates on ten miles of road ; but these relics of old days are of only historic interest, as are the majority of the thirty patented and forgotten forms of wood pavements which had their rise and fall thirty to forty or more years ago, beginning in Boston, Philadelphia and New^ York about 1840 and culminating from i860 to 1870, in the "Nicholson block," of which a description is now useless. ROUND CEDAR BLOCK. The well-known round white-cedar block pavement came into general use in western cities about 1880, in response to an urgent demand for something quick and cheap which would last until the abutting lots could be sold. This pavement w^as built in different ways in the various cities, but it probably has its best form as still built in Chicago in 1900. The prepared subgrade of the street is covered with two inches of sand, in which are embedded, across the street at six feet intervals, one-inch by eight-inch pine boards laid flat, as supports for the ends and centers of two-inch hemlock plank laid lengthwise of the street and close together, forming a regular crowned surface. The cedar blocks are of sound live w^ood, free from bark, not less than four, nor more than eight inches in diameter and six inches long. These blocks, unsea- soned and untreated, are set on end in close contact, and the irregular interstices are rammed full of half-inch to one and one-half inch gravel. The surface is then flooded twice with coal-tar heated to 300° Fh., using two gallons per square yard in all, followed while hot with 67 CITY ROADS AND PAVEMENTS. a three-fourth-inch layer of clean gravel, not exceeding half-inch, which has been screened from that used to fill the spaces. In 1900, this cost about seventy cents per square yard in Chicago, where there was then about 880 miles (on basis of thirty feet width) of streets thus paved. This being probably somewhat more than the total similar mileage in all of the other cities using this form of pavement, the relative amounts being in about the following order: viz., Detroit, Superior, Duluth, Mil- waukee, Minneapolis and Toronto. It usually needs renewal in six years and becomes impassable in nine years, though the results are some- times much better than this. Cypress blocks were similarly used in Omaha, Des Moines and Kansas City, and failed in two to four years. BLOCKS ON SIX-INCH CONCRETE BASE. Hexagonal blocks of mesquite, 5" deep and 4" to 8" diameter have been laid at San Antonia, Texas, at cost of $2.80 per square yard, including the six-inch base. Tamarack-blocks, 3" by 5" by 6" have been laid in Montreal and coated with hot coal-tar and gravel. Redwood blocks, 4" by 6" by 6" seasoned, and boiled in asphalt, have been laid in San Francisco and Oak- land, California. Yellow pine blocks, 4." by 6" by 6" to 10" creosoted with twelve pounds per cubic foot, were laid in Galves- ton, Texas, in 1895-8. Creosoted or " treated " blocks on concrete base are recommended for fifteen miles of streets by the board of local improvement of Chicago during 1902. 68 WOOD BLOCK l'A\ KMEMS. -;i^ty o 0. > < 05 ^ '*" < ^ ■J c ^ 2 "^ -a , *" L ' O > ^■r^ ^ oi HI r" o rn ■j: o W Si Qi o < 0) > ;.; ^ < ''^ n '1^ tii '^ ffi H ^ O Z 69 CITY ROADS AND PAVEMENTS. Washington cedar blocks, sterilized and creosoted with three to four pounds of creosote per cubic foot, were laid on about four miles of Indianapolis streets in 1896, and some are in good condition in 1901. Some of the w^ooden pavements built in Indianapolis about that time have swollen and heaved badly. Oregon red cedar and southern yellow-pine heart- wood blocks, 4" by 4" by 9" creosoted with ten pounds per cubic foot, were laid in 1899 in Indianapolis at a cost of $2.10 to $2.50 per square yard, including base and five years guarantee : the joints being filled with paving cement of nine parts coal-tar to one part asphalt, and the surface being covered with half-inch screenings of crushed granite. This is a much more costly pave- ment than the others which have been described, and is of a high class, as are the later improved kinds described on page 74. In Paris, pine blocks of several forms, creosoted with eight to ten pounds of creosote oil per cubic foot, form the greater part of the ninety miles (thirty feet width) of wood-paved streets. Wood is preferred as being less slippery and less noisy than compressed rock-asphalt, and that it is satisfactory in its other qualities is evi- denced by the fact that the amount of wood pavement in Paris is increased every year. Including the six- inch concrete base in both cases, the cost complete is about the same as for rock-asphalt, viz., $3.10 per square yard. 70 AUSTRALIAN HARD-WOOD PAVEMENTS. These are the most costly of any of the various wooden-block pavements and, therefore, have not been laid to any extent in the cities of the United States. They have, however, been largely used, and wdth good effect, in London, which has wood pavements of many kinds to the extent of about 240 miles, computed on a basis of thirty feet width. The city of Sidney, New South Wales, has many miles of wood-paved streets, upon which Australian hard woods have been used with most remarkable results, which would be incredible if not substantiated by the statemicnts of \\\ A. Smith, M. Inst. C. E., and also by the report of R. \V. Richard, Asso. M. Inst. C. E., the city surveyor of Sidney, and engineer in charge of Sidney pavements. Queen street, which has an estimated daily traffic of 25,000 tons, was thus paved, and the blocks after eight years use, showed a greatest observable wear of one-sixteenth of an inch and were otherwise in almost as good a state in 1893 ^'^ when laid. The original cost was $3.05 per square yard, exclusive of foundations, with an annual cost of two cents per square yard for maintenance and for daily sanding. The details of their construction in Sidney are as follows : 71 CITY ROADS AND PAVEMENTS. The foundation, or base, was a layer of one-to-seven concrete, formed with a floated smooth surface, having a convexity from one in forty to one in eighty, and allowed to set for seven days before use. This concrete base was six inches thick on solid ground and nine inches thick on uncertain ground. The pavement which gave the best result was formed with seasoned heart-wood blocks of tallow- wood, black- butt, and blue gum, red gum, jarrah or karri, each kind being laid separately. Each block was formed by cut- ting a three-inch by nine-inch plank into pieces six inches long, and these blocks were then painted with, or dipped in, hot coal-tar and hot wood-preserving oil, and stacked for four hours before being set in the work. The blocks were set on end with the fibre vertical, forming three-inch rows across the street from curb to curb, each block breaking joints two inches with blocks in the next row. To provide for the expansion of the blocks when wet, expansion-joints were formed along each side of the pavement; these joints being two inches wide between the curb and the gutter-course, and an additional one- inch joint between the gutter-courses, which were formed of blocks set in rows running lengthwise of the street. Curbs, eighteen inches deep, were needed to resist the thrust which moved twelve-inch curbs. Bet- ter results were reached when these expansion joints were filled with mastic than when filled with sand or with clay puddle. These widths of joint were used on pavements sixty-four feet wide and gave good results. The best results were obtained when the blocks were forced close together on grades up to one in twenty and with one-quarter-inch joints on steeper 72 AiMEKlCAN HARD-WOOD PAVKMKNTS. < c £ c -^ C -7 < - O 73 CITY ROADS AND PAVEMENTS. grades up to one in thirteen, or eight per cent. After completing sixty Hneal feet of roadway, the surface of the pavement was swept with hot coal-tar and sprinkled with hot sand, and again swept with hot tar until the spaces were thoroughly flushed with the plastic paste. As to the durability of these hard- wood blocks as compared with cubical blocks of blue-stone, Mr. Richard states that the blue-stone blocks have shown a wear of one inch per year, while the hard-wood blocks, laid as described and subjected to similar traffic, have shown a wear of one-fiftieth {-^\) inch per year. Where the joints have been filled with hydraulic cement, the results were not as satisfactory as where blocks were laid with close joints, but with the con- struction described, these wood-block pavements are free from the various faults of our cedar blocks and are expected to have a minimum life of sixteen years, equal- ing asphalt. In Melbourne, similar pavement is estimated to last fourteen years. Either of these improved methods or the more crude ones generally used in this country are costly. The final expense of our cheap construction being twice as great as for asphalt or for granite blocks, and probably much greater than if white oak or some similar hard wood were used. AMERICAN WOOD PAVEMENTS OF THE LATEST TYPE. The valuable qualities of the highest grade of treated wood-block pavements have been generally recognized especially their freedom from noise; but their extensive use in the cities of the United States has been deferred by distrust based upon former failures and by the excessive cost. The cities seem to have awaited the de- 74 AMERICAN WOOD PAVEMENT. velopment of some process of treatment of native woods which should be less costly than the Australian hard- woods just described, and more satisfactory in various ways than the former well-known American methods. The creosote as ordinarily used is an effective pre- servative in itself, but it tends to form an emulsion with water, and also to ewaporate half to three-fourths on exposure to the sun and the weather. To avoid these defects has been the object of two recent modifications of the treatment : the one called " kreodone-creosote," and the other " creo-resinate." 75 CITY ROADS AND PAVEMENTS. Concrete base Id prugreis, Ten-ton roller. Completod pavement. MERIDIAN STREET, INDIANAPOLIS, 1902. Kreodone-Creosote Wood-block Pavement in progress in March, 1902. 76 KREODONE-CREOSOTE PROCESS. This consists in impregnating the seasoned selected blocks under pressure with ten pounds per cubic foot of an oil derived from creosote oil, possessing the origi- nal preservative properties with a longer endurance, and also having the effect of forming a varnish-like film or coating on the outer surface of the wood, protecting it from the elements. The seasoned blocks are sterilized by subjecting them to dry heat of 240° Fh., for eight hours. The kreodone-oil is then forced into the fibres of the wood, under a pressure of seventy pounds per square inch, maintained for two to three hours, or until twelve pounds have been absorbed by each cubic foot of the wood. In some cases the blocks are laid with the courses running diagonally across the street. The cost in Indianapolis for blocks four inches deep, has been #2.50 to $2.70 per square yard of completed pavement, includ- ing concrete base, and also including nine years' guar- antee and maintenance. The cost of the Chicago pavement on Michigan avenue, in front of the Auditorium hotel, for blocks five inches deep, exclusive of the concrete base, and including surety company guarantee for five years, was $1.90 per square yard. This Chicago pavement and that on North Dela- ware street in Indianapolis, were both laid in 1901, and will furnish conspicuous examples by which may be observed the peculiar qualities of pavements treated with kreodone-oil. 11 CREO-RESINATE PROCESS. A pavement treated by this process has become known during 1900 and 1901 by having been laid on conspicuous streets in Boston, on Tremont street in front of the Parker House and on Harvard Bridge and on Beacon street, and in Springfield, Mass., and in New Rochelle, N. Y., and on Holliday street, Baltimore, Md., where these pavements have been much commended. B. T. Wheeler, superintendent of streets of Boston, states that the creo-resinate pavement seems the most '§t^ H f TREMONT STREET, BOSTON, 1900. Creo-Resinate Wood-blocks, laid in 1900. 78 CREO-RESINATK I'ROCESS. satisfactory piece of wood-paving in Boston, and tliat it is guaranteed to be kept in such condition for ten years. As there used, the pavement is noiseless, is free from dust, is not sHppery when wet, when laid on three per cent grade with the grooved joint shown on page 29, can be taken up and re-laid readily, does not absorb moisture, and promises to be durable, though this can only be assured by the test of time. The special features of the creo-resinate process are the preliminary treatment in dry heat to kill the germs of decay, and the mixing with the creosote of fifty per cent of melted rosin which is forced into the fibres with the creosote, where it solidifies and seals the pores of the wood and prevents the evaporation of the creosote or its displacement by water, w^hich can find no entrance, so that the pavement does not swell and heave when wet. The blocks are of Georgia long-leaf yellow-pine heart-wood 4" by 8" by 4" deep and are treated in an air-tight cylinder by dry heat for five hours, during which time the temperature and pressure are gradu- ally raised to 285° Fh., and to ninety pounds per square inch, when both are gradually lowered and a vacuum is produced, followed by hot creo-resinate mixture, afterwards forced in by hydraulic pressure of 200 pounds per square inch, which is maintained until twenty-one to twenty-two pounds of the mixture has been absorbed by each cubic foot of the wood. This is followed, in another cylinder, by hot milk-of- lime under the same pressure, in order to fix and set the creosote, so that the blocks, when ready for use, present a peculiarly solid appearance. 79 CITY ROADS AND PAVEMENTS. The blocks are then laid, with the grain vertical, upon a one-inch cushion of screened sand, covering a six-inch concrete base; the blocks are driven tightly together at every sixth row and are rolled with a five- ton steam-roller until a firm, uniform and unyielding surface is made, when the whole is covered temporarily with one-quarter inch of clean screened sand. COST. The cost of this pavement, complete, including a surety company ten-year guarantee, for blocks four inches deep on concrete six inches deep, varies with the local conditions from $3.10 to $3.50 per square yard. 80 VITKIFIKI) r.RICK. Main street, Daj-ton Ohio, paved in 1892. Street in St. Louis, paved in 1901. ', I ^>*.^"^..r"*^" '* BRICK PAVEMENTS IN 1901. 81 VITRIFIED BRICK PAVEMENTS. THEIR USE IN THE UNITED STATES. During the past seventeen years there has been a steadily increasing use of vitrified brick for the pave- ments of the streets of cities and towns in the United States, especially of those of moderate size — that is, of 100,000 inhabitants and less: the larger places wel- coming brick as a competitor with sheet asphalt, and as affording another means of escape from the intoler- able noise and dirt resulting from block-stone pave- ments and from the temporary and unsanitary features of cedar blocks, while the smaller western towns, with characteristic enterprise, have built miles of brick pave- ments to displace the natural mud. The total length of brick-paved streets in the United States in February, 1902, is estimated by Wm. S. Crandall, editor of The Municipal Journal, at about 1300 miles. The following table is reprinted from the first edition of " City Roads and Pavements," and shows the modes, costs and results in sixty-five cities in 1894: 82 VITRIFIED BRICK PAVEMENTS. Brick at entrance to Union Station, laid m 1893. (Stone-block pavement in foregrovind ). Alley paved with brick in 1894. BRICK PAVEMENTS, ST. LOUIS, 1901. 8 Summary of Reports of Modes of Construction, Cost and Results of Vitrified Brick Pavements. City and State. Atlanta. Ga Atchison, Kan Alton, 111.. Alleghany, Pa Bellaire, Ohio Binghamton. N. Y. Bloomington, HI. . . Buffalo, N. Y Burlington. la Cedar Rapids. la. . . Charleston, W. Va. Chicago, 111 Cincinnati, Ohio. . . Clinton, la Columbus, Ohio . . . Connellsville. Pa.. . Council Bluffs, la.. Davenport, la Dayton, Ohio Decatur, 111 Detroit. Mich...... Des Moines, la Dubuque, la Dunkirk. N. Y Evansville, Ind Findlay, Ohio Fort Wayne. Ind . . Galesburg, 111 Hannibal^ Mo Hartford, Conn Indianapolis, Ind. . Jacksonville, 111. . . Kansas City, Mo. . . Kenosha, Wis Keokuk, la Lafayette, Ind Lancaster, Pa Lexington, Ky Lincoln, NeV> Lock port, N. Y Louisville, Ky Massillon, Ohio Memphis, Tenn Olean, N. Y Omaha, Neb Ottawa, 111 Peoria, 111 Philadelphia, Pa. . . Providence. R. I. . . Quincy, 111 Rochester, N. Y. . . Rockford, 111 Rock Island, 111.... St. Paul, Minn Scran ton. Pa Springfield, 111 Steubenville, Ohio. Syracuse, N. Y Terre Haute, Ind. . Toledo, Ohio Troy, N. Y Washington, D. C. . Watertown, N. Y. . Wheeling, W. Va.. Wilmington, Del.. . Miles in use June, 181)4. Average of prices. ].l 2.75 1 2 0.25 6 3.33 7.50 2 1 15 10 30 2 5 6 0.4 15 9.6 10 1.5 2.5 4.5 4 2 12 1.5 0.12 8.7 9 10.25 1 1.25 2.50 0.10 6 15 10 10 9 2.25 1.50 10.25 2.25 20 1 6 3.14 1.82 7 0.34 0.10 5.38 10 5 1 16.33 1 0.25 0.12 2 3 Cost per Square Yard of "Best Work'' on the Foundation here indicated. Six inches Concrete. $2.19 1.60 "2!46' '2!75 2.30 2.50 2.00 2.30 2.50 1.70 1.69 2.10 1.70 1.63 4.00 2.35 2.00 1.80 2.25 2.09 1.50 2.65 2.00 1.87 1.75 2.05 3.00 2.30 2.33 2.15 2.50 2.05 2.46 Flat Brick or Gravel. M.75 2.16 2.00 1.60 1.35 1.50 1.60 1.75 1.80 2.05 1.55 1.80 1.75 1.40 1.75 1.62 2.40 Broken Stone or Grave). .19 $1.75 ).6l 1.15 1.45 '2!49' 1.87 'i!75" 1.40 'i!55' 1,40 1.80 1.37 1.33 1.35 1.00 2.25 1.05 1.35 2.15 .52 Filling of Joints. Paving tar. Sand. Sand. Paving tar. Cement grout. Sand. Cement grout. Sand. Sand. Sand. Paving tar. Paving tar. Sand. Paving tar. Sand. Sand. Sand. Cement grout. Sand. Paving tar. Paving tar. Sand. Cement grout. Sand. Paving tar.- Cement grout. Sand. , Sand. Cement grout. Paving tar. Sand. Reported Results. Satisfactory. Excellent. " Fair. Fair. Good. Fair. Gratifying. Fair. Sand. Sand. Sand. Paving tar. Cement grout. Cement grout, Sand. Paving tar. Cement grout. Sand. Sand. Sand. Paving tar. Sand. Paving tar. Sand. Sand. Sand. Cement grout, Sand. Sand. Cement or tar. Cement grout. Sand. Cement grout. Cement grout Sand. Paving tar. Cement grout Satisfactory. Fair. Good. Good. Excellent. Good. Good. Good. Good. Fair. Good. Satisfactory. Good. Satisfactory. Good. Good. Perfly. satisfy. Good. Good. Good. Fair. Good. Good. Good. Good. Good. Good. Excellent. Good. Good. Entirely satis. Good. Moder'telyfair Good. Fair. Good. Good. Good. Good. Satisfactory. Indifferent. Good. Good. Good. Good. Good. Good. Good. Good. Satisfactoiv, 84 RKACTIOX ACrAINST USK OF P>RI(KS. EXTENT OF FFS USK. Two to three hundred such cities and towns, as well as all of the larger cities, especially Philadelphia, have laid more or less vitrified brick pavement, and its use is constantly extending, as is shown by the accompany- ing table on page 130, compiled by Willis Fletcher Brown, city engineer of Toledo, Ohio, showing the miles of streets paved with brick and with sheet asphalt in thirty cities. This table also shows the relative estimation in which brick is held as compared with sheet asphalt in cities where both ha\'e been used for a period long enough for opinion to be formed. REACTION AGAINST USE OF BRICKS. There has undoubtedly been a reaction in the popu- lar desire for brick pavements in some of these cities, where people have learned to know what good pave- ments are and where brick pavement has been brought into close comparison with sheet asphalt, and with the best grades of creosoted wood-block pavements in the western cities, and more recently by comparison with bituminous macadam or bitulithic pavement, in a few of the cities of the east. The excessive and peculiar roaring noise produced by the passage of light wagons over some brick pave- ments is objectionable on residence streets, and on some streets having heavy traffic there have been poor results as to durability. Much discredit has also been thrown upon the use of vitrified brick by the care- less and ill-judged manner in which many manufac- turers have sent out irregularly and imperfectly burned brick. These have been laid by incompetent contrac- 85 CITY ROADS AND PAVEMENTS. tors, under inexperienced city officials, and have thus caused the needless failure of many pavements, thus stopping further extensions and preventing other cities from using brick at all, to the great gain of the sheet- asphalt companies, and with the effect of encouraging the introduction of bituminous macadam, creo-resinate wood blocks and other high-grade pavements which are free from these defects and which have not yet had time to develop other defects which may be peculiar to themselves. REGION OF PRODUCTION. The production of vitrified paving brick in 1894 was in a measure restricted within two regions of Penn- sylvania and Ohio on the southwest and Indiana and Illinois on the west, w^hich produced the special quality of material for forming paving bricks, which differ entirely from ordinary building bricks in both their material and mode of manufacture and in their qualities ; the name being a misleading one, as they are not brick but tile, and are not actually vitrified, but are fused. There are now a number of places outside these limits where paving bricks are produced in large quan- tities, one of the large plants being on the Hudson river at Catskill, from which have been furnished bricks for pavements in 112 cities and towns, nine-tenths of which are in seven of the eastern states, and the rest are in six of the southern states. The material of these bricks is low-grade iron ore, shale and clay, which are ground to a powder and mixed in proper propor- tions and formed into repressed bevelled-edge vitrified paving bricks and blocks, which compare well with others, and w^hich have been used for most of the brick pavement in Albany, N. Y., with good results. 86 CHARACTERISTICS. Other well-known kinds of high-grade paving mate- rials are the Mack bricks and blocks, made at very large works, located at New Cumberland, W. Va., fifty-six miles west of Pittsburg, Pa. These have been used for pavements in loo cities and towns, two-thirds of which are in five of the eastern states, the rest being in three of the middle western states and four of the southern states. The materials are silica, alumina and iron, forming fire-clay, which is ground to powder and mixed with water in proper proportions and moulded into bevelled- edge vitrified paving bricks and blocks. Streets of Philadelphia, equal to over sixty miles length of thirty feet width, have been paved with these blocks, and it is stated by Wm. H. Brooks, chief of bureau of highways of Philadelphia, that some streets thus paved for over ten years have required no repairs and are now in good condition. CHARACTERISTICS. The material for moulding any paving brick must be of a peculiar character which will not melt and flow when exposed to an intense heat for a number of days, but will gradually fuse and form vitreous combinations throughout, while still retaining its form. The resulting brick must be a uniform block of dense texture, in w^iich the original stratification and granulation of the clay has been wholly lost by fusion which has stopped just short of melting the clay and forming glass. The clay while fusing must shrink equally through- out, thus causing the brick to be without any lamina- tions or any exterior vitrified crust difTering from the 87 CITY ROADS AND PAVEMENTS. S8 ABRASION AND IMPACT TKST. interior. Such a brick will be incapable of absorbing any considerable amount of water, and will hence be unaffected by frost, and if formed of the best material properly treated will be tough, to withstand the blows of horses' toe-calks; hard to resist the abrasion of wheels, and strong to carry heavy loads: these being in the order of effectiveness of the destructive forces to be met. There is now little difficulty, with rigid inspection, of getting brick which will uniformly possess these qualities. QUALITIES OF PAVING BRICK. If the brick are uniform in character and are per- fectly formed of proper material which is thoroughly fuzed, they will be harder than glass and nearly as hard as quartz (being 6.5 on Mohs' scale), and will be tough enough to endure traffic. These qualities will be best determined by the followang described test: ABRASION AND IMPACT TEST. The standard test revised and adopted by the Na- tional Brick Manufacturers Association in 1900, pro- vides for the use of a machine having a rattling chamber twenty-eight inches in diameter and twenty inches in length, formed of two steel heads and four- teen steel staves set one-fourth inch apart to allow the escape of the chips and dust. This machine must be set to run uniformly at about thirty revolutions per minute for about sixty minutes, or for 1,800 revolutions by actual count of a cyclometer. Each separate charge of bricks to be tested must consist of bricks of one 89 CITY ROADS AND PAVEMENTS. kind, which must be perfectly clean and dry, and free from moisture : twelve paving bricks or nine paving blocks (so called because larger), are accurately weighed and constitute a charge, together with 300 pounds of cast iron in the form of blocks with rounded edges and corners : one-fourth in weight to be two and one-half inches square on end and four and one-half inches long, and three-fourths to be one and one-half-inch cubes. After 1800 revolutions, made as stated, the loss is determined by again weighing the brick: the limit of loss which is allowed varies in different specifications : the St. Louis specifications reject bricks when the tests show a loss of over thirty per cent of the original weight: Columbus, Ohio, puts the limit at twenty- seven and one-half per cent : many lots of bricks tested will lose less than tw^enty per cent. Such brick must be practically without pores, for a brick which can absorb water equal to more than two per cent of its dry weight, will probably fail to endure the rattler test. The absorption test is, therefore, not a useful one, and may mislead, and may safely be omitted. The tests by abrasion, and for absorption, and for crushing strength, are the most important of the numer- ous tests which are sometimes specified, and of the total value of all the tests, the abrasion test is variously con- sidered as varying from thirty per cent to seventy-five per cent of the whole. EXAMINATION OF BRICKS IN USE. The best and most useful test can, however, be made by visiting places where brick pavements have been in 90 EXAMINATION OF BRICKS IN USE. use for several years, and by examining tlic actual results of traffic upon well-known and standard makes of brick. For instance, Columbus, Ohio, has some eighty miles of brick pavement, varying in age from one to twelve years, in which twenty-six kinds of paving bricks and blocks have been used, with various kinds of fillers in the joints. Dayton, Oliio, has twelve miles of brick pavement, in which fourteen kinds of bricks and blocks have been used. Des Moines, Iowa, and Terre Haute, Indiana, have also large mileage, composed of great varieties of mate- rials, as have also Cleveland and Toledo, Ohio, Louis- ville, Ky., and Detroit, Michigan. A few days spent in such examination of pavements in actual use will make experiments unnecessary, and will enable the engineer wiio is planning new work to avoid poor bricks and to specify those kinds which can be depended upon to give good results. This method of natural selection is gradually forcing the poor grades of brick out of the market. 91 CITY ROADS AND PAVEMENTS. Mixing and placing- concrete base. Placing brick on sand cushion. BRICK PAVEMENT, PROSPECT STREET, CAMBRIDGE, MASS., iS 92 BUILDING BRICK PAVEMB:NT. Rolling' with two and one-half ton roller. Spreading Portland cement grout filler. BRICK PAVEMENT, PROSPECT STREET, CAMBRIDGE, .MASS., li 93 CITY ROADS AND PAVEMENTS. VARIOUS STYLES OF CONSTRUCTION. The table on page 84 is reproduced from the first edition as showing the actual practice in 1894 i^"^ the sixty-two cities there named, of which thirty-four then used one course of brick set on edge on a six-inch concrete base with a sand-cushion of one inch. Vitrified Br.cK- 5ancl ^ Concrete 1- Brictt' pavement The table on page 100 shows a more general use of a concrete base in 1900 and 1901, and this is to be expected as showing a higher standard of work obtained at less cost. Broken stone forms a good base, especi- ally where it is covered with a layer of sand, with a course of second quality of brick, laid flat, as founda- tion for the surface-course of brick set on edge. Two courses of brick on sand have been used for seventeen miles of pavement in Topeka, Kansas, some of which has been in use for twelve years, and all of which is in fine condition in 1902. It is there pre- ferred as being less noisy than when laid upon a con- crete base, and being made from local brick has cost $1.25, or less, per square yard. A concrete base, for which details are given on page 42, is, however, usually well worth the extra cost, and should be used in preference to any cheaper substitute ; especially for a city which has been educated to a cor- rect idea of what constitutes a good pavement. 94 SAND CUSHION. MODE OF CONSTRUCTION. The earth roadbed being sub-drained and rolled hard, as described for other pavements, should be formed with a regular crown of about one one-hundreth the width between curbs: the best amount of crown is an important matter discussed on page 30, and the following table is given to show the practice in 1900 in twenty-seven cities having experience with brick pavements: Actual "Crown" of Brick Pavements as Built in 1900. CITY. State. Inches ]ier 30 ft. width bet. curbs ! CITY. State, Inches per 30 ft. width bet. curbs. CITY. State. Inches ])er 30 ft widtii bet curbs. Albany Atlanta Binghamton. . . Buffalo Columbus Dayton Detroit Elmira Erie N. Y.. Ga N. Y.. N. Y . . Ohio... Ohio... Mich . . N. Y.. Penn . . 5 5 5 5 6 4'f 4-2 6 Fort Wayne. . Grand Rapids Harrisburg. . . Houston Jackson Joliet Mansfield Meridan j Milwaukie . . . Mich .. Mich .. Penn . . Texas.. Mich.. Ill Ohio... Conn . . Wis . . . 4 6 5 6 4 5 6 6 New Orleans Peoria Sandusky Scranton Springfield . . . St. Paul Terre Haute . Toronto Troy La Ill Ohio... Penn . . Mass . . Minn . . Ind.... Ont ... N. Y.. 5 6 6 5 3>^t0 7 6 7 4 BASE FOR BRICK PAVEMENT. This may be formed in either of the several ways mentioned on page 94, but should generally be four or six inches of concrete, as detailed on pages 42 to 56. SAND CUSHION. When ready to set the brick, the sand cushion is formed by spreading screened moist sand over the con- crete or other base: this is spread uniformly to the required depth of one and one-half to two and one-half inches, and smoothed and brought to the proper crown by wooden templates, traveling on wheels or shoes and resting on the top of the curbs on either side. Upon the true surface thus formed upon the sand, the brick are set on edge, the workmen standing only upon the 95 CITY ROADS AND PAVEMENTS. brick already laid, and placing the bricks in front of them in regular lines across the street; the brick in each course breaking joints with those in the next courses. The bricks are then rammed with a seventy- five pound rammer and rolled with a two and one-half- ton or a five-ton steam roller and settled firmly into the sand-bed. If the surface is then sprinkled and examined, soft brick can be detected and picked-out as being those which remain wet after the hard bricks have dried. JOINT FILLERS. No filler has yet been found that is perfect, and there are wide differences of opinion as to the best. Sand filler is cheap and allows the brick to be readily taken up and relaid, but it also allows the edges and corners of the bricks to chip and become rounded, and permits the bricks to settle at soft spots of subgrade. Portland Cement Gront of equal parts by bulk, of loose cement and fine sand, if properly made and applied, is better, and there are patented mixtures which are combinations of iron-slag and cement ground together, and which are equally good or better. Grout is irregular and worthless, unless the sand used is so fine as to remain in suspension, and such sand is not easy to obtain : grout should be poured into place, but is sometimes flushed broadly over the surface and swept into the joints. Grout makes it difficult to take up and relay the brick, but it can, if properly made and applied, perfectly protect their edges and corners and thus pre- serve a smooth surface, which is most desirable. For some reason which is not clear, the pavements with cement grout joints seem to be the most noisy. Paving Cement makes an elastic joint which in some cases is best, although it costs more than grout. The 96 JOINT FILLERS. usual composition consists of lOO })arts l^y wciglit of No. 4 coal-tar, til rcc parts residuum oil and twenty parts refined asphalt, kept and used at a temperature of 300° Fh., meantime carefully avoiding over-heating it. This hot mixture should be poured into the joints from a spout, or it may be poured upon the surface and swept in with steel wire brooms: a thin coating of sand should be at once spread over the pavement, and this will mix with the surplus pitch while still hot so that traffic will soon grind the whole from the surface and leave the bricks clean. Expansion. — The expansion of brick pavements during and after periods of extreme heat has been a frequent source of trouble, and many pavements have been thus heaved and broken ; in some cases by a quiet raising of the brick pavement until the arch thus formed was broken by its own weight or by traffic, as occurred at Niagara Falls in July, 1897, '^^'^^ "^^ Glens Falls in August, 1901: in other cases by sudden ruptures or explosions, as at Kansas City in July, 1901, where this occurred on seven streets and brick w^ere thrown ujd a foot or more. In nearly every case this peculiar result has occurred where the brick have been laid with cement joints, and where the cross-expansion has been pre- vented by rigid curbs ; or at the apex of grades from both ways, or at the top of a steep incline where the resulants of longitudinal expansion have been concen- trated at one place. Expansion-joints of one inch of coal-tar, or mastic, or bitumen or sand have been formed along the curbs on l3oth sides of the street and across the pavements from curb to curb at intervals of fifty feet: one city in centra] New^ York took special precautions of this kind 97 CITY ROADS AND PAVEMENTS. and yet has had more or less trouble every year. Other cities have taken no precautions and have no trouble. It remains to find a preventive. BRICK PAVEMENT FOR STEEP GRADES. Brick pavements are often used successfully on grades which are considered to be too steep for smooth asphalt, which may afford no foothold, or for macadam, which may be gullied by heavy rainfalls. It is often difficult to decide what pavement to use in such cases, and equally difficult to select from the various forms of vitrified bricks and the different ways of laying them, in order to secure the best results on steep slopes. The following table is given of the steepest grades of brick pavements, in actual use in 1900, in the cities named : the fact that such steep grades are in use, may not be taken as a reason for imitation, but may furnish conclusive reasons for avoidance. Maximum Grades of Brick Pavements — 1900. CITY. State. Grade in feet per 100 feet. CITY. state. Grade in feet per 100 feet. Albany Baltimore Columbus Des Moines . . . Erie N.Y... Md ... Ohio .. I owa . . Penn . . Ill Ohio .. Wis . . . 9-3 9 1 1 7 6 8 8 Nashville .... Parkersburg . . Peoria Philadelphia. . St. Joseph. . . . Toledo Troy Wheeling .... Tenn . . W. Va. Ill Penn . . Mo ... Ohio .. N.Y... W. Va. 7 8-4 6 10 Joliet Mansfield Milwaukee .... 5-6 7 8 Cost. — The average cost of construction of brick pavement on concrete complete in 1894, ^^ot including curbing and extras, as shown by the table on page 84, 98 BRICK PAVEMENT FOR STEEP GRADES. was 32.21 per square yard, \arying from $1.56 at Alle- ghany, Pa., to $3.00 at Providence, R. I. In 1900, the cost is materially less, and the j^rices of several are given as a basis, being obtained from tlie "Engineering News" and the "Engineering Record,'' and from direct advices. On April 10, 1900, at Chillicothe, Ohio, offers were made by six bidders for pavement to be formed of either of seven different kinds of first-class paving bricks, using either of four different kinds of filler in the joints and naming a price for each ; six inches of concrete forming the foundation in each case. For the concrete base the prices ranged from twenty-eight to thirty-four cents, with an average of thirty-one cents per square yard. For the bricks laid in place, the prices ranged from seventy-seven to eighty-eight cents with an average of eighty-four cents per square yard. For the fillers, the prices per square yard ranged from an average of nine cents for cement to an average of sixteen cents for " No. 6 filler; " fifteen cents w^as bid and accepted for " Murphy grout,'' a patented mixture of powdered iron-slag and cement, which w^as used. For the complete pavement (not including excava- tion or curbs) the prices ranged from $1.24 to $1.38, with an average of $1.33 per square yard. On May 18, 1900, at Kewanee, Illinois, four bids were made for vitrified brick pavement on six inches of con- crete for w^hich the price for base, pavement and filler complete in place, ranged from $1.42 to $1.47, with an average of $1.45 per square yard. These and other prices are given in the table on page 100, in each case giving not only the minimum price, at which the work was done in each case, but 99 CITY ROADS AND PAVEMENTS. O w I— I Q < w < O ;5 »— ( Q U W > < u C W u Oh o t/l ^/^ ^ CnO O M o 00 00 lO M 00 C^ 00 M rOOO C^ fO c, N ■E/3- O ci M O O ^^ ci O. lo lO ^ M M M CO Cn ^~ fO fO <^ ^ 'd- Tf- LO rt- lO O t^OO C^00 rt ^ ■ji in m ir. ir. ^ s_ ^ t_ »-i >^ >^ >> >s >^ l-O i-O LO l-O l-O ir. j: l-O U-) O K w M ro M M • — C C C C xc^*-' •—' "- "^ -^ '"'^ M VO h-t M M C E c c c c c ^ .S .S .S .S LOO O O CO cc .s .s 00 00 vo o o t .s .s .s .s .s o o o -— --H Q H-l l-H ^ '^: !:C i S^:: .^ 3 =i 3 1^ .'^•z: "z^ TX o < 4-1 . ^ rt rt rt ^ ^ ^ o o o rt rt rt ^ ^ ^ o o o o o v: m ir. x^ ^ 1^ <1-) O U ^ ^ r-| r^ r^ r^ ^^ ^^ '—' o o o ■^ O -^ ^ "^ "^ ri ri -^^ ^ l—l ^ f^ ^~t ^-i I 1 r— I (L) I; u u u u :; ^ ::; ^ tn o a, 0-) u o CO 3 'o :/: m mmOOOCnOOOmmmCnOmOO Cn OOm OOOOOCnOOOOOOC>0000 Cs ooo CNCr\CNC\CNOC CsOnCnCnCnOX CnOCnCn 00 CnCNCn r-O O l-O O r- ^ '-> VO VO O M M CO M M M o looo ) b/D tiD bJD ^ „ _: ^ c^ =5 ^ ^ e^e-^ rt ^ rt ^Sc^;::^oo Rock-asphalt laid in front of City Hall in 1897 and repaired in 1898. Soui^ccs 0/ Supply.— Th^YQ are many sources of sup- ply of different asphalts, each varying from the rest and each requiring its own treatment. Formerly that from Lake Trinidad was assumed to excel all others for forming the American asphalt mixture ; but large de- posits were discovered in 1899 in northern Venezuela in addition to Bermudez Lake in the Department of Sucre, which alone is eight times the size of Lake Trinidad. There is also in Venezuela another newly found deposit of asphalt near the Gulf of Pavia in the Orinoco delta, and another in the state of Jujuy in Argentina. 108 ARTI Fin AL SHEET-ASri I A I .T. The American supplies of Kentucky sand-rock and of California sand-asphalt are very large and are free from international complications. MATERIALS AND METHODS; AMERICAN ARTIFICIAL SIIELT- ASPHALT PAVEMENT. Asphalt. — The full details of the materials and of the methods of construction are omitted here, but those which are given are based upon the practice during 1900 in the city of Washington, where closest atten- tion is given to the subject by the engineer commis- sioner of the District of Columbia, aided by Prof. A. W. Dow, whose expert ability is widely known. Trini- dad and Bermudez asphalts are used with results which appear to be equally good. They are " refined " by simply evaporating the water which occurs with them in their crude state, and which forms about one-third of the Trinidad Lake asphalt. This refined asphalt must be softened to be useful as a paving cement, and for this effect there is used a flux, which is generally a heavy mineral oil or petroleum residuum. Asphalt cement is the result of mixing eighty-one to eighty-seven parts, by weight, of refined asphaltum, with nineteen to thirteen parts of flux. This forms the matrix cf the asphalt pavement, constituting nine and one-half to twelve and eight-tenths per cent, or an average of nine and seven-tenths per cent by weight of the asphalt mixture forming the wearing surface. Asphalt cement of a softer consistency is formed by mixing seventy-two to seventy-eight parts of refined asphaltum with twenty-two to twenty-eight parts of flux. This forms the matrix of the "binder," or about five per cent of its total weight, or about eight per cent of its bulk. 109 CITY ROADS AND PAVEMENTS. Skill and care are required to vary the amount of flux, so as to produce the uniform results necessary for a reliable pavement. Asphalt Mixture. — The "asphalt mixture" above referred to is formed by mixing about nine and seven- tenths parts by weight of asphalt cement with ninety- one and three-tenths parts of hot sand and stone-dust and limestone dust: the asphalt cement varying dur- ing 1900 from a minimum of nine and five-tenths to a maximum of twelve and eight-tenths per cent. This limited amount of asphalt cement is less than the actual voids in the sand, but the " mixture " becomes too plas- tic, and forms waves when rolled, if the attempt is made to use enough asphalt cement to wholly fill the voids which are probably equal to at least five per cent after it is rolled and finished. Saiid. — The careful and exact testing and propor- tioning of the sands and the stone-dust and limestone dust are a special feature of later practice. Formerly it was only required that sand should be clean and free from objectionable matter, but since 1894 it has been recognized that there are many varieties of sand, no two deposits being alike and no deposit being uniform. Samples are now taken constantly and are heated to a proper degree of dryness, and then passed over a series of screens to determine the relative proportions of each size. The composition of each of the various sands which are available being thus learned by tests, two or more kinds are combined in certain proportions, using great care from day to day to obtain a perfectly uniform mix- ture having a minimum of voids. These voids are in turn filled, as nearly as possible, by adding a varying 1 10 MATERIALS AND MHTMODS, KTC. proportion — averaging about one-tenth of the weiglit of the sand — of finely powdered siHcaor fine stone-dust. Limestone dust was formerly used exclusively for this purpose, but during recent years powdered silica or powdered mineral of any kind has been used instead and has been thought to be better in some ways : but the latest evidence in 1900 is said by Prof. A. \\\ Dow, to show that powdered limestone acts differently in some way and that the toughest and best asphalt is produced when, in addition to the stone-dust, powdered limestone is also used. The sand resulting from these admixtures had the following proportions as the average mesh compo- sition of the sands used during 1900. The voids were the least possible and were probably not more than twenty-five per cent nor less than twenty per cent when the sand was shaken and packed as closely as possible. Percentages of the sand retained on sieves as follows: 10 meshes per linear inch none. 20 meshes per hnear inch 6.;^ per cent, 40 meshes per linear inch 30.1 per cent. 60 meshes per linear inch 23.7 per cent. 80 meshes per linear inch 15.6 ])er cent. 100 meshes per linear inch 7.8 per cent, passing 100 meshes per linear inch 16.5 per cent. 1 00.0 ])er cent. This accurate proportioning of the sand and of the stone-dust to fill its voids was found necessary in order to prevent the uncertainties caused by the variation in character of the sand in different localities — it proving cheaper to go to this expense and trouble than to make good the failures which formerly occurred when all care had apparently been used in making and })lacing 1 1 1 CITY ROADS AND PAVEMENTS. the ordinary mixture. This has been done since 1894 by the best equipped companies, who have learned the necessity, and the details, from experience and who are therefore able to guarantee their work in a w^ay which was not formerly possible. Crushed Stone for '* Binder T — Crushed stone to form the " binder " consists of any tough, hard rock and is the total product of the crusher passing through a one and one-quarter inch screen, with some of the dust removed and with the coarse screenings of the sand added. Ninety-five parts of this by weight are mixed while hot with about fiYQ parts of the softer asphalt cement before described. The amount of asphalt cement varies with the char- acter of the stone, the hot asphalt cement being added in the mixer until all faces of each fragment are coated^ but avoiding any excess of asphalt which might tend to fill the voids between the fragments of stone. FORMATION OF THE PAVEMENT. Foundation, — If the street has never been paved, the base of the proposed asphalt pavement is made of hydraulic cement concrete four inches or six inches thick. The usual practice is here shown and in the table on page 56. Con creTfe Asphalt Pavemenr 112 FORMATION OF THE PAVEMENT. Much of the sheet-asphalt laid in the great cities has been put directly upon old pavements of cobbles or of stone blocks, of which the depressions maybe filled with hot crushed stone sprinkled with hot asphaltic cement^ or which may be merely re-set at points of subsidence to restore the regular form, but which are usually re-set at three inches lower grade and with the proper crown in order to make room for the "binder" and the " wearing surface " of asphalt, without having to raise the manholes, car-tracks and curbs. The lower part of Seventh Avenue, New York, was thus treated during 1 90 1. The joints between the stones of the old pave- ment should be three-fourths of an inch wide and should be brushed and cleared for at least an inch in depth to afford a firm hold for the " binder." In some instances, stone blocks for a base have been re-laid flat to give a lower grade, but this is not good practice and has given poor results unless there is a concrete base beneath the old blocks, as was the case in New York on Broadway below Forty-second street to Canal street which was thus treated in 1901. Brick pavements built in 1887 have been used as base for sheet-asphalt for many miles of streets in Columbus, .Ohio. Old macadam roads have often been successfully used as foundation for sheet-asphalt, and this may work well until cuts are made for sewer and water and gas connections when it will be difficult to restore the pavement. Binder. — The mixture of stone and asphalt which has been described at page 112, is brought hot from the mixer and is spread over the clean and dry base, using rakes to give it a regular depth of two inches, 113 CITY ROADS AND PAVEMENTS. where it is at once compressed to one and one-half inches with a steam roller which may be slightly sprayed with water to prevent adhesion. When completed, this "binder" must be firm so that fragments are not displaced by the passage of con- struction teams, but the surface must be open and " honey-combed " so that it may give a good hold for the " wearing surface " which should follow at once if possible and certainly on the same day. All trafhc must be kept off during whole progress of work. If the fragments of binder are not firm, or if its voids are filled by excess of asphalt cement, such portions must be removed and replaced by perfect material. Asphalt work of all kinds should stop during rain^ or snow-fall, or freezing weather. Wearing Surface. — This is formed of the " asphalt mixture" which has been described on page no, and must be brought hot from the mixer and should reach the work with a temperature of about 280° Fh. : the surface of the " binder " should be swept perfectly clean to receive it, and it should be spread with hot rakes to a uniform depth of two and one half inches of the loose material, taking care to loosen that coming from near the bottom of the cart which must be scraped clean after every load. The loose layer is spread two and one half inches deep to form a one and one half inch finished surface, or three and one-third inches to form a two- inch surface, which latter is much the better for heavy traffic. Rolling the Wearing Surface. — The " asphalt mix- ture " is then rolled with a cold 1200-pound hand roller^ the surface of which is constantly wiped with a piece of oily cotton-waste to prevent adhesion. 114 FORMATION OF TIIF I'AVKMFNT. After this rolling which is done quickly, tlie surface of the asphalt is covered with finely ground dry mineral dust (generally using dry liydraullc cement), wliich is swept over the surface to give it tlie soft gray color which is desired and to j^revent the adhesion of the five-ton finishing roller with which the " wearing sur- face " is rolled until compressed to one and one half inches or two inches in thickness and until the surface is perfect. Cities are about equally divided as to which of these thicknesses is used, as indicated in table on page 56. This rolling will usually occupy about one hour on sixty feet length of pavement thirty feet wide. The entire manipulation of the material, and espe- cially its spreading and rolling, require skill and care not only for the general features here described but also for many other important details which are neces- sary to secure good results. TT5 CITY ROADS AND PA.VEMENTS. CARROLL STREET, BROOKLYN, NEW YORK, 1900. Before covering cobble pavement with sheet-asphalt in 1900. 116 SUKKKT-AS I'll ALT rAVKMKNT. CARROLL STREET, BROOKLYN, NEW YORK, 1900. After paving with Trinidad sheet-asphalt in 1900. 117 CITY ROADS AND PAVEMENTS. GRADE AND CROWN. The actual steepest grades existing in various cities are shown in the accompanying table, in order that those having doubts in any extreme case may examine some of these grades and observe the results. Actual Grades of Sheet-Asphalt. CITY. State. Ft. per loo feet. CITY. State. Ft. per loo feet. Buffalo Erie N. Y.... Penn. ... Mich Conn Ohio.... N. Y.... Neb Ill 5-1 5 7 5 5-75 5 8 7-2 Pittsburg Salt Lake City. San Francisco . St. Joseph Scranton Syracuse Toledo Troy Penn . .. Utah.... Cal Mo Penn. .. N. Y. .. Ohio.... N. Y. .. 17 5 i6 8 13 7 5 7-5 Grand Rapids.. Hartford Marion New York Omaha Peoria. The crown used in various cities on level streets is shown in the same way; it being borne in mind that the least crown which will shed water makes the best road for those who use it. See " Crown of Pavement," at page 30. Actual " Crown " of Sheet-Asphalt. CITY. State. Inches ]ier 30 ft width bet curbs CITY. State. Inches per 30 ft. width bet. curbs. CITY. State. Inches per 30ft width bet. curbs. Albany Atlanta Bine;hamton.. . Buffalo Charleston Columbus Dayton Detroit Elmira Erie N. Y.. Ga N. Y.. N. Y . . S. C. . . Ohio... Ohio . . Mich . . N Y.. Penn . . 5 5 5 5 4 6 4^ ->% 4^ 6 Fort Wayne. . Grand Rapids Harrisburg. . . Hartford Houston. Jackson Joliet Mansfield Meridan Milwaukie . . . Mich . . Mich . . Penn . . Conn . . Texas.. Mich . . Ill Ohio... Conn . . Wis . . . 4 6 \)i 6 h4 II Muncie New Orleans Peoria Sandusky .... Scranton Springfield . . . St. Paid Terre Haute . Toronto Troy Ind.... La Ill Ohio . . Penn . . Mass .. Minn . . Ind.... Ont ... N. Y.. 12 5 6 6 5 3>^ 5^ 7 7 5^ 118 RIGID RAIL-BASE. RAITAVAV TRACKS IN ASPHALT-PAVED STREETS. When railway tracks are laid in streets paved with asphalt, there is wide variation in the manner of con- struction next the rails : of fifty-two cities having this condition to meet, all have, until recently, put some other material than asphalt next to the rails : fourteen using granite blocks, six using stone blocks, and four- teen using vitrified brick. The best practice in Buffalo, Rochester, Pittsburg and elsewhere, is to use ninety-pound rails with nine- inch or ten-inch webs welded in continuous lengths, and placed on twelve-inch concrete base to insure rigidity: the asphalt surface being then laid in contact with the rails. See page 40. The practice in Rochester since 1899 and in Pitts- burg in 1 90 1 has been to first place the heavy steel rails accurately on line and grade with temporary supports, and then to form the twelve-inch concrete base beneath the rails ; ramming and tamping the concrete until it rises against the rail-base and gives it a perfect bearing at all points without having to use w^edges. COST OF SIIEET-ASPIIALT. This varies widely with local conditions and with the competition and can best be seen by reference to the tables here and at page 56, showing rates with and without concrete base and curbs. 119 CITY ROADS AND PAVEMENTS. PRICES FOR SHEET-ASPHALT PAVEMENT, NOT INCLUDING BASE OR CURBS OR EXTRA WORK. DATE. Oct. I, 1900. Jan. I, 1901. Sept. 26, 1900. Oct. I, 1900. Sept. > 1900. PLACE. Guar- antee. Albany, N. Y 10 yrs Cedar Rapids, Iowa j Cincinnati, Ohio 5 yrs Owensboro, K y ] San Antonio, Texas j 10 yrs. No. of Bids. Price per Sq. Yd. Max. Aver. Min. 2.17 $1.91 $1.34 2.02 i-«3 1.69 2.31 2.21 1.97 2.09 1-93 1.80 2.00 1.56 1.40 INCLUDING 6 INCHES OF CONCRETE AS BASE. DATE. PLACE. Guar- antee. No. of Bids. 5 2 Price per Sq. Yd. Max. Aver. Min. Aug. 7, 1900. March 3, 1901 . Aug. I, 1900. , 1899. March 4, 1901 . — , 1899. — , 1899. — , 1899. , 1898. — 1899- — , 1899. , 1899. Dec. 31, 1900. Sept. 3, 1900. Aurora, 111 5 yrs. 10 yrs. 10 yrs. 10 yrs. 10 yrs. 5 yrs. 5 yrs. 5 yrs. 5 yrs. 5 yrs. 10 yrs. ^ 5 yrs. ID yrs. 5 yrs. $1.97 2.27 2.35 $1.88 2.34 $r.8i Baltimore, Md 2.17 2.33 1.89 2.00 1.95 2.13 1.95 1.70 1.70 1-53 2.62 Cortland, N. Y... Fort Wayne, Ind Houston, Texas Joliet, 111 3 2.90 2.42 Milwaukie, Wis New Orleans, La Oswego, N. Y 2.23 Peoria, 111 Rochester, N. Y Sandusky, Ohio St. Paul, Minn includ- ing excav. >2.26 2.04 Toledo, Ohio 2.65 2 27 2.10 Note. — Mainly from the columns of the Engineering News and of the Engineering Record. GUARANTEE. It is now usual to require that the price paid for a sheet-asphalt pavement shall include a guarantee that it will be kept in good condition for a term of years and delivered in good condition at the expiration of this time: this term varies as is indicated by the records of forty cities of the United States which had, on Jan- uary ist, 1900, 757 miles of sheet-asphalt pavement: of these, twenty require guarantee for five years and twenty require a guarantee for ten years. Ten of the latter have formerly required five years, but now require 120 GUARANTEE. ten, showing a tcMidency toward a ten year guarantee. Maintenance guarantees for long terms were required for the sheet-asphalt pavements of Fifth avenue and of Broadway, New York. Asphalt was laid in 1S96-7 on Fifth avenue with fifteen years' guarantee at the follow- ing prices per square yard, including new concrete base : from Ninth street to Fifty-ninth street, the cost was ^4.35 : from Fifty-ninth street to Eightieth street, $4.00: from Eightieth street to Ninetieth street, $3.29: these different rates indicating the expected effects of traffic on the cost of maintenance. Asphalt was laid in 1900 on Broadway, with fifteen years' guarantee, from Fifty-eighth street to Fourteenth street, upon new concrete base to Forty-second street and upon the old stone blocks relaid flat upon two inches of sand over the old six-inch to eight-inch con- crete base below Forty-second street. The cost was $5.37 per square yard. Asphalt was extended in 1901 down Broadway to Canal street, and cost $6.31 per square yard. This in- cluded fifty-nine cents for relaying the old blocks fiat upon the old concrete base and also ten years' main- tenance. This should include strewing sharp sand when the pavement is slippery, as on Fifth avenue and on all wood-block and asphalt pavements abroad. The average cost of a guarantee in Buffalo is put by F. V. E. Bardol, M. Am. Soc. C. E. (see page 56), at three cents per square yard for the first five years and fifteen cents for the second five years or eighteen cents for ten years. The probable cost of a guarantee for the third five years would in some cases equal the cost of an entire renewal of the surface. 121 CITY ROADS AND PAVEMENTS. 122 SHEET-ASrUALT PAVEMENT. f^^ ^:/ 123 CITY ROADS AND PAVEMENTS. CAUSES OF FAILURE OF SHEET-ASPHALT. A reasonable amount of traffic tends to prolong the life of a good sheet-asphalt pavement. When a pave- ment beghis to fail, the causes are probably to be found in about the following order: First. — Defective foundation, which has settled and caused the hollows in which pools of water have stood upon the surface of the asphalt until it has become disintegrated. Second. — Wearing surface too soft, or excess of asphalt in binder, or dirt on surface of binder, either of which may allow " wearing surface " to creep under traffic and to form waves or rolls, in which the sheet of asphalt mixture is thickened, alternating with hollows where it has become thin. Third. — Patches where the pavement has been torn up for sewer and water connections and not well restored. Fourth. — Surface cracks, which sometimes appear in cold weather as a result of excessive contraction of the surface, and which sometimes close and re-unite in warm w^eather under the combined effects of warmth and of passing wheels. Fifth. — Excessive traffic which has worn off the sur- face. This is the least common. Sixth. — Lack of traffic, allowing the asphalt to become spongy. The latter cause usually shows its effects at the sides of the roadway next the curbs, where there is least passage of wheels. The process of failure may then be as follows : The material composing the sheet of asphalt expands slightly with the sun's heat, as all other substances do; but unlike most other substances, it does not of itself at once return to its original thickness when the heat 124 CAUSES OF FAILURE OF SIIEET-ASrilAI.T. is lost, because the asplialt becomes rigid as it cools, and unless compressed by force, tends to remain in its expanded form. In the center of the roadway, where most of the wheels pass, the asphalt is at once re-com- pressed, but at the sides this is not done so promptly, with the result that there is a tendency to become somewhat porous or spongy where there is little traffic. When at last the asphalt has thus actually become porous, water can permeate it, and this soakage of water is helped by the fact that the surface-drainage is toward the sides, where the material is most likely to absorb some of it. Having thus absorbed ever so little moisture, of course both heat and frost have increased JEFFERSON AVENUE, HROOKEYN, iqoo. Destriictive effects of gas leaks on sheet-asphalt pavement. CITY ROADS AND PAVEMENTS. effects upon the material, and ultimately it shows signs of disintegration. Seventh. — When a failure of asphalt is so complete as to include several of these features, it will usually be found that the pavement was built by some local paving company, wdthout previous experience, whose bid should not have been considered and whose work and guarantee proved to be equally worthless. EightJi. — Disintegration of surface may also result from defects in the mixture of asphaltum and flux or from the laying of the pavement during freezing weather; disintegration is frequently caused, espe- cially in Brooklyn, New^ York and Kansas City, by the escape of illuminating gas from leaky mains. The hydrocarbons which are now used in these cities to enrich and cheapen illuminating gas, are solvents of asphaltum ; leaks of this destructive and tenuous gas from the underlying main pipes are the direct cause of failures like those shown in the accompanying photo- graph of Jefferson avenue, Brooklyn, taken in 1900. Disintegration of asphalt is also caused by the spill- ing of kerosene by careless vendors, and by the drop- ping of oil from the axle-boxes of street-cars. Bonfires are sometimes built on asphalt pavements with destructive effect, and this was done in one case with a misdirected desire to celebrate the completion of the pavement w^hich it injured. Most of these causes of failure are preventable by proper selection of the builders or by proper care of the finished work. There are many cases — among them Oswego, N. Y., as shown on the frontispiece — where no defects of any kind have appeared during and after five years' use of the pavement. 126 BLOCK ASPHALT PAVEMENT. Asphalt blocks are used in many cities of the United States, there being in 1900 the equivalent of ninety-five miles of pavements, thirty feet wide. During 1900, twenty-one streets, equal in area to three miles, thirty feet wide, were thus paved in the Borough of Manhattan, equaling twenty-five per cent of the sheet asphalt laid in 1900. Washington, in July, 1900, had twenty-two miles of such pavement, as compared with 141 miles of sheet- asphalt. The asphalt blocks laid in 1900 were formed of thirteen per cent asphaltic cement, ten per cent limestone dust and seventy-seven per cent crushed gneiss, and cost $1.77 per square yard laid, not including base. The character of asphalt blocks has been much im- proved during recent years and the proportions are now usually about as above stated, except that crushed diabase trap or basalt is generally used and with better results. The materials are heated to 300° Fh. and are mixed in a rotary mixer until all the faces of every particle of the crushed stone are perfectly coated with the mixture of asphaltic cement and limestone dust. The product is then put in moulds twelve inches long, four inches or five inches wide and three inches or four inches deep and subjected to a pressure of two to two and one-half tons per square inch and then slowly cooled in water. This is done in a factory where the best results may be obtained and the blocks are then shipped to their destination, where they can be laid, like brick, in cold weather, if necessary, by unskilled labor. This last feature constitutes their chief advantage over sheet asphalt. The blocks are laid in close con- 127 CITY ROADS AND PAVEMENTS. tact, sometimes on gravel covered with sand, though a concrete base is best, upon which the blocks are some- times bedded in one inch of Portland cement mortar. Asphalt blocks made as above described, have worn well, but there are few cases where sheet-asphalt is not preferable. The following table shows the prices of recent pavements of this kind : Prices for Block-asphalt Pavement, Four Inches Thick, Including Six Inches of Concrete as Base and Filler in Joints. Date. CITY. State. Guar- antee. No. ot bids. Price per Sq. Yard. Max. Aver. Min. Mar. II, 1 90 1 Mar. 13, 1901 Mar. II, 1901 Sept. 3, 1900 Feb. 18, 1901 Annapolis . Chillicolhe. Pontiac Toledo Toledo Md.. Ohio. Mich. Ohio. Ohio- 5 yi-s. 5 ys. 5 yrs. 5 yrs. 2 ^ On 6 in.| 1 gravel. J 18 3 $2 85 3 25 2 55 $2 80 1 17 2 32 2 45 $2 75 1 07 2 40 1 95 2 25* * (On sand base, seventeen cents less; on stone base, three cents less.) A cheaper modification of block-asphalt, known as the Leuba pavement, has been in successful use in Neuchatel, Switzerland, since 1898, and consists of blocks eight and three-fourth inches long, four and one- half inches wide, and four inches to four and one-half inches thick, but with the lower three-quarters of each block made of hydraulic Portland cement and clean, sharp sand in proportions of about one to four : this concrete base being covered with a w^earing surface one and one-fourth to one and one-half inches thick of compressed natural rock-asphalt: the tw^o materials being joined under heavy pressure, and the blocks being laid with cement joints on a concrete base. 128 BLOCK-ASPHALT PAVEMENT. BLOCK ASPHALT PAVE^IEXT, NINETY-SIXTH ST., NEW YORK, 1900. Looking- west from Third avenue to Park avenue. Paved in 1900. 129 CITY ROADS AND PAVEMENTS. List of Cities Having Both Sheet-Asphalt and Brick Pavements. Miles of each with preference. city. Albany Atlanta Baltimore Binghamton .. Boston Buffalo , Cleveland Columbus Dayton , Detroit , Elmira Erie Fort Wayne .. Grand Rapids Harrisburg . . . Houston Jackson Joliett Mansfield Marion Milwaukee . . . Minneapolis.. New Haven .. New Orleans . Peoria Philadelphia.. Rochester Sandusky .... Scran ton Springfield . .. St. Joseph . .. St. Paul Terra Haute. . Toronto , Toledo Troy Washington .. Total State. N. Y. Ga ... Md .. N. Y. Mass . N. Y. Ohio . Ohio Ohio Mich . N. Y Penn Mich Mich Penn Texas Mich 111.... Ohio.. Ohio.. Wis ... Minn Conn La ... Ill Penn N. Y Ohio Penn Mass Mo .. Minn Ind .. Ont .. Ohio N. Y D. C. Sheet- Asphalt, Jan. 1, 1900. 9 2 7 5 14 217 9 15 17 22 miles miles miles miles miles miles miles miles miles miles 0.8 mile II miles 7 miles 6 miles 3.4 miles 4 miles 0.4 mile 3 miles I mile 1.5 miles ID miles 13 3-5 23 8 235 43 I 12 0-3 9 13 3-5 24 21.6 4 141 miles miles miles miles miles miles mile miles mile miles miles miles miles miles miles miles Brick. Jan. I, 18 16 2 I 2 I 7 66 74 12 24 o. 6 ID 4 o. 7 2. 3 15 6 miles miles mile miles mile miles miles miles miles miles mile miles miles miles mile miles miles miles miles miles 2 miles 5 1-5 59 22 120 7 6.5 2 1-5 7 3 4-5 8 42 8-5 I miles miles miles miles miles miles miles miles miles miles miles miles miles miles miles mile 920 miles 560 miles II Preference. As- phalt. Brick. On over 4 per cent grades. 13 Not stated. 13 (Compiled by Willis Fletcher Brown, consulting engineer of Toledo, Ohio.) 130 BITUMINOUS MACADAM, OR BITULITHIC PAVEMENT. During 1901, a practically new form of pavement with the above name has attracted much attention and has come into use at widely separate places : its favor- able discussion in the Engineering News of January 30, 1902, and in the Engineering Record of the same date, has confirmed many in the opinion that this was a new factor in the solution of the paving problem although the test of time is yet to be applied. The former bituminous or "tar" pavements have usually been formed of sand the fine grains of which have no other stability or structural strength than is derived from the matrix of asphalt or of coal-tar in which they are embedded : or they have consisted of tarred fragments of stone with twenty per cent or more of void spaces, generally placed without systematic heating and mixing. The new pavement is formed of trap rock, or other tough rock, crushed and screened to fragments varying in size from two inches down to the dust, and com- bined in such proportion of sizes that the final spaces between the fragments of rock do not exceed ten per cent. This means that the fragments must be in actual and firm contact with each other and that the addition of ten or twelve per cent, by bulk, of bituminous com- BITULITHIC PAVEMENT. Adams Street, Lowell, Mass. Rolling and coating the base. Temple Street, Cambridge, Mass. Spreading and rolling the wearing surface. BITUMINOUS MACADAM, 1901. 132 DETAILS. pound will fill the remaining voids and make a solid and impervious mass. When this is accomplished, the result must be a pavement which water cannot penetrate and which should support the passage of traffic without abrasion of the fragments upon each other and without the bituminous filler being exposed to action of the weather. It is obvious that the success of the pavement will be dependent upon the care which is used in the selec- tion of the materials and the skill and thoroughness shown in combining and placing them, and that these features are as important as for an asphalt pavement. BASE. The base for the new pavement is prepared as for a macadam road; the earth road-bed being graded, drained, formed and rolled, and then covered with a layer of the best stone available w^hich is crushed and screened to two inches and larger and is rolled with a fifteen ton steam roller into a compact layer four inches thick. This stone base is then sprinkled with a thin hot bituminous mixture and then covered with a coat- ing of thicker hot bituminous mixture which binds the surface of the base and prepares it to receive the next layer w^hich is spread on top of it. TOP. The " wearing surface " is then spread w^iile hot, and is rolled and compressed to a final thickness of two inches: this "wearing surface" is formed of the best available rock, preferably trap rock, which has been crushed and screened to retaii^i all less than two inches : ^33 CITY ROADS AND PAVEMENTS. this is then dried and heated in rotary drums and then screened in rotary screens which separate it into the various sizes from two inches down to dust. These sizes are then proportioned, and some sand added if necessary, in such ratio as shall give a minimum of voids not exceeding ten per cent : this low ratio of voids being only possible by careful study. The heated stone is then run into a mechanical mixer at a temperature not exceeding 300° Fh., together with hot bituminous cement (which may consist of asphalt), in sufficient quantity to fill all voids and to coat all faces of all particles of stone and dust and sand, and also to provide a slight surplus of " filler." When thoroughly mixed by about 1 50 revolutions of the mixer, it is hauled to place on the street and is spread and rolled in the same manner as asphalt, but using a fifteen to twenty-ton steam roller to compress it and to crowd the bitumen into all the voids, forcing out all air-bubbles and making the surface as dense as possible. Upon this surface, filling its irregularities and mak- ing it sticky, there is then poured and rubbed a coating of quick-drying bituminous cement, heated to 250° Fh. and over this is spread about a quarter-inch layer of small stone chips which are rolled and forced into the sticky coating forming a final wearing surface: these chips being larger in proportion as the grade is steeper, so that a good footing is given for horses on steep grades. COST. During 1901 streets have been thus paved by vari- ous city departments, under expert advice and super- 134 OPINIONS. vision, at New Bedford, Holyoke, Cambridge, Lowell and Brockton, Massachusetts, and at Salem, N. J., and Pawtucket, R. I., and Charleston, S. C; and the cost has ranged from $1.25 at Holyoke, Brockton and Lowell to $1.50 per square yard at Salem, or about double the cost of ordinary macadam of the same thickness. The city engineers and oflficials of these cities have spoken so favorably of it that a number of cities are to follow their example during 1902 at varying costs from $1.80 to $2.75 per square yard, which in each case in- cludes guarantee for five years. Among these are Taunton, Mass., Norwich, N. Y., Charleston, S. C, Yonkers, N. Y., and three miles of " State Road " leading south from Cleveland, Ohio, which last is to cost $1.40 per square yard: also, two and one-fourth miles of Seventh Avenue, New York city, from iioth street to 155th street, which, if done, will cost about $2.75 per square yard: the five year guarantee in this case being important, as the trafific is heavy. WIDTH AND GRADE. The pavement usually extends from curb to curb, the widest built being forty feet at Salem, N. J., and the narrowest being sixteen feet proposed near Cleve- land, Ohio. The steepest grades are eight feet to twelve feet per 100 on Harvey street, Pawtucket, R. L, and ten feet to fifteen feet per 100 proposed at Yonkers, N. Y, OPINIONS. This new pavement has been in actual use only since January, 1901, but the opinions expressed by 135 CITY ROADS AND PAVEMENTS. MAPLE STREET, HOLYOKE, MASS.,1901. Before and after paving with Bituminous Macadam. 136 OPINIONS. skilled road-builders, who have examined it critically, are favorable as to its durability and \'alue. In addition to the officials of the various cities named, many city engineers and street superintendents ha\e examined these pavements during and after comple- tion, and intend to build similar ones in their various localities, it being found that the winter and spring of 1902 have left these in good condition. Among these are the president of the Massachusetts highway association, C. A. Brown of Cambridge ; the vice-president of the Massachusetts highway asso- ciation, R. A. Jones, of Waltham ; Prof. A. W. Dow of Washington, D. C, who is quoted by the Municipal Journal as expressing the opinion, based upon what he knew of it, that this pavement exceeded in good quali- ties any other pavement that he had seen laid. Chas. W. Ross of Newton, former State highway commissioner of Massachusetts, commended it to the convention of supervisors of New York State at their annual meeting at Albany on January 28, 1902, saying that its use would prevent the storm-washing of macadam streets on steep grades and would have saved Newton from damages amounting to $20,000 which were caused by a single shower in July, 1901. With such weighty opinions from unbiased experts, it is evident that this pavement is a factor to be con- sidered in future projects for city streets. 137 BROKEN-STONE ROADS. In the recent wide discussion of " Good Roads," mac- adamizing or some more or less similar arrangement of small fragments of broken or crushed stone, is most often spoken of, and the general reader who has given no special attention to the subject further than to read the many articles which appear in papers and maga- zines is most likely to conclude that some such con- struction suits all conditions and localities, though it is really best suited and most used for highways outside of the business parts of cities. Within the past eight years, there has been an in- creased use of broken stone roads for residence-streets of cities, resulting from the examples of good work given by the governments of various states in building high- ways by state aid outside of corporate limits, and thus familiarizing city ofificials with the methods by which the best roads of this kind can be built and maintained. This is especially manifest in the cities of Massa- chusetts, where over 200 miles of macadamized streets have been built since 1894 i^"^ the cities of Brookline, Cambridge, the Newtons, Medford and Springfield, as well as 240 miles in Boston. Also in many cities of New York State, especially in a section of Buffalo, near Delaware Park. The city of Greater New York leads in this as in all things, the five Boroughs having on 138 EXTENT OF BROKEN-STONE ROADS. January ist, 1901, the following stated miles of mac- adam streets and boulevards. Manhattan, eighty-two miles; The Bronx, ninety-one miles; Brooklyn, eighty- two miles; Richmond (Staten Island), 183 miles; Queens (on Long Island), 388 miles ; Central Park, nine and a half miles (all telford, 1869 to 1878); Pros- pect Park, six and a half miles ; Greenwood, twenty miles; or a total of 862 miles of broken-stone roads within the city, practically all but forty- five miles built since 1894. The building of rural roads by state aid was begun in 1893 by the State of New Jersey, which pays one- third of the cost of construction ; followed in 1894 ^Y the State of Massachusetts, which pays three-fourths of the cost, and by Connecticut in 1895, ^vhich pays two- thirds to three-fourths of the cost, and by New York State in 1898, which pays one-half of the cost: the bal- ance in each case being paid by the towns or counties. In Maryland, the state aids the counties by making their surveys and plans and directing the improvements. Under these systems, the roads most considered and most built have been of the two principal types of con- struction known as the macadam and the telford, though many miles of gravel roads have also been built and many miles of highways in each state named have been merely improved by forming and draining the natural materials as found, with the idea that this work may be later continued by putting broken stone upon the road- ways thus begun. ROCK FOR ROADS. Trap. — The three states first named are fortunate ii"! having many formations of good rock for road con- 139 CITY ROADS AND PAVEMENTS. struction, while New York State is mainly limited for the best grade of rock to the diabase-trap or dolorite formation lying on the Hudson River in Rockland county, just north of Nyack and opposite to Sing Sing or Ossining. This lies ten miles north of the limit of the proposed Palisades Reservation, is more accessible by canal boat and by railroad than any part of the Pahsades and con- tains enough material of the best grade to macadamize all the roads in the state. The many quarries of New Jersey and Connecticut are also available for roads in New York as well as in those states. There was also discovered in 1901 a large isolated mass or "plug" of trap rock, near Schuylerville, N. Y., about twenty miles north of Albany, lying close beside the Champlain canal and the railroads. Other similar formations have been found in Clinton county by the State Geologist, Professor F. J. H. Merrill. Trap rock is the best for road construction, in that it has no true cleavage and breaks irregularly with toothed surfaces, and is tough and does not easily grind into dust and mud. Its spe- cific gravity is great, so that its dust does not blow so readily as that of limestone. Porphyry is ranked next, but it is not common and the supply in New York State is limited to Lake Champlain. Quartzite, and siliceous qiiartzite are more common and in some cases make very good road-material. Granite of some varieties is a good road-material, in proportion as it contains a small amount of mica and of quartz, and is not weathered. The same is true of gneiss and of syenite, which are granitic and of which large and accessible formations 140 ROCK FOR ROADS. exist at Little Falls, on both sides of the Mohawk ri\ei\ where there are unlimited quantities, close to the Erie canal and the railroads. Throughout Westchester county, N. Y., there are many and varying ledges of gneiss, some of which are tough and good, but many of them carry an excess of mica and of quartz and of feldspar, and crumble readily, especially when weath- ered, and are unsuited to road-making. Limestone usually binds well and readily and, if unusually hard, makes a good road. Well-known examples of the best limestones, which have been and are much-used for road-making, are the Tompkins' Cove stone and tlie Clinton Point stone, quarried on the Hudson, forty miles and seventy miles from New York, and the Bethlehem stone, near Albany, N. Y., and the Jammerthal flint-limestone, quarried in the suburbs of Buffalo, N. Y. Some of the other limestones, which also bind readily and have been used for roads, contain an excess of lime and crush under heavy trailRc, and form a light and impalpable dust, wdiich is most objectionable to residents as well as to drivers. This dust is only avoided by keeping these roads constantly wet, entail- ing an expense for sprinkling w^hich proves to be more costly than to use a better stone which does not form such dust. Soft limestones form a good low^er course to be cov- ered by a harder wearing-surface or top course. The cementing action, so called, of limestone, is purely mechanical, but it serves to firmly bed the fragments and to prevent them from rubbing and W'Caring against each other. The use ot limestone screenings is dis- cussed at page i6o, under ''Quality of Screenings." 141 CITY ROADS AND PAVEMENTS. <*•, ,««*'^ Mr: . feg: ii^i 1 -i ^ 1 ^pr/,. ^ "^H ^C^Sa ■Sf»^I|^^f'l ' ?^^^^^^H|^H^^^^HH M ^^ptte^ ,xp- "'"''* ^^^n Sandstone or "bluestone" road, built m Ulster county, N. Y., by state engineer E. A. Bond, M. Am. Soc. C. E., in 1900. 142 COBBLE-STONES. Sandstone is only suited for use where better rock cannot be readily obtained, and then only for tlie base course where it should be covered by a wearing sur- face of trap or other tough rock. An exception to this must be made in favor of the ''blue-stones" of Ulster county, and the five adjacent counties of eastern New York, which are true sandstone and are peculiarly tough. The Ulster county stone binds readily with its own screenings, and has been used to form the whole material of good six-inch macadam roads, which stand well under moderate traffic and are here shown. Various Kinds of Rock. — Broken stone roads can be well made with various rocks, requiring varied treatment to suit the conditions. The many rocks and the details for their successful use, can nowhere be better studied than in New York State, which probably contains as great a variety of geologic formations as any other equal area in the world. IMPORTANCE OF UNIFORMITV. In the selection of material to be crushed for road metal, uniformity in character is of the first importance; material which is uniformly of a second grade being preferable to a mixture of better and worse. Such a mixing of fragments of hard and soft rocks results in quickly crushing the softer pieces and then exposing the harder pieces to excessive shocks from passing wheels. COBBLE-STONES. Rounded cobble-stones gathered from tlie fields and lake shores, make a very poor wearing sui"face for a road, whatever their composition. 143 CITY ROADS AND PAVEMENTS. Being worn by action of water or ice into rounded forms, all of the fragments crushed from them have at least one curved or water-worn face. These curved and polished faces prevent the adjacent fragments from coming to a solid bearing in a road. They will always be likely to rock or slide under passing loads, and thus loosen all the fragments which touch them. Further, these rounded cobble-stones which were strewed broadcast over parts of the country during the glacial period, came from the most widely different localities in the northern part of the continent and include all varieties and degrees of hardness. Granite, syenite, quartz, limestone, flint and slate were found to make up one-tenth of a mass of them, of which the remaining nine-tenths were sandstone, of which at least one-half were so disintegrated or weather- worn — so " rotten," as the workmen call them — as to be worthless for any purpose: for road-surface metal they are worse than worthless, as their only effect is to destroy the good material with which they chance to be mixed. Crushed cobble-stones may be selected to form the lower or base course, if nothing better is available, by rejecting all which are inferior and by selecting, to be crushed and screened, only the hardest and best. 144 TESTS OF ROAD MKTAI. 145 TESTS OF ROCK FOR ROAD-MAKING. The various rocks available for road-making are compared as to their relative endurance, by subjecting similar sets of samples of each kind to similar abrasion in machines like that here shown, which was devised by Deval in 1878. Each set of samples consists of eleven pounds, or five kilograms, of roughly cubical selected fragments, none smaller in any way than one and one-quarter inches, nor larger than two and one- half inches. These are cleaned, washed, dried and accurately weighed, and enclosed in one of the cylinders and tightly sealed. Similar sets of samples are put in each cylinder and the whole machine is then slowly revolved at the rate of 2,000 revolutions per hour for five hours, or until a cyclometer registers 10,000 revolutions. The fine dust worn from each set of samples is then saved for cementation tests, and the fragments are washed, dried and again weighed : comparison of the percentage of loss of each set indicates the relative endurance which is also to be seen by examining the fragments of rocks before and after testing. The department of civil engineering of Columbia University has a most complete equipment with which Prof. Wm. H. Burr, M.Am. Soc. C. E. has caused to be made many useful tests of road materials, and Harvard 146 TESTS OP^ ROCK FOR ROAI)-M AKIXG. is similarly equipped : the testing laboratory of the college of civil engineering of Cornell Uni\ersity, directed by Prof. E. A. Fuertes, M. Am. Soc. C. E., is also fully equipped and makes many tests of stone and bricks for pavements, as does the highway division of the Maryland geological survey at Johns Hopkins University, directed by Harry Fielding Reid by whose courtesy the plates of machines and samples are here given. Records of similar tests of various rocks have been made and published by the highway commission of Massachusetts, by the highway division of the geological survey of Maryland, by the U. S. ofKice of road inquiries at Washington, by the State geolo- gist of New York and by the State engineer of New York and these records are useful guides in selecting stone for road-construction. H7 CITY ROADS AND PAVEMENTS. MARBLE. HARD LIMESTONE. DL\BASE TRAP ROCK. ROCK FRAGMENTS BEFORE AND AFTER ABRASION TEST. Two-thirds natural size. HIGHWAY DIVISIOX, MAKYLAND GEOLOGICAL SURVEY. 148 TESTS OF ROCK FOR ROAD-MAKING. The following table shows the results of loo tests of the six kinds of rock most used in Massachusetts and New York: KIND. Diabase trap Limestone . . Granite . . . . Quartzite . . . Gneiss Sandstone . . Per cent OF Loss BY i Number of tests. 1 Max. Min. 35 4.31 1.40 24 6.68 2.33 10 4-30 2.23 7 5-9° 1.97 12 6-57 1-73 12 6.69 1. 71 Mean. 2.28 4.34 3-52 ?>-(^?> 4.01 (The last item includes Medina Sandstone at a. 29 and Ulster " Bluestone " at 3.71.) Several local rocks are sometimes available of which there may have been no tests, but experience will usually enable a selection to be readily made of the one which will give the best results. The rock which will bind the most readily will probably be the least durable, and it may be more economical to make a long haul of a good rock than to use one which is near at hand, but which will soon need renewal. 149 THE MACADAM AND THE TELFORD SYSTEMS. About a century ago Macadam preached and prac- ticed a gospel of good roads for England with an effectiveness which our leagues of to-day can only hope to imitate in the United States. England had long had roads of broken stone, and the use of this material was not peculiar to Macadam's method ; but he was the first to establish rules of con- struction which were generally accepted, and under them were built 25,000 miles of road which formed a network all over England; so that his name has come to be associated with broken stone as a road material, although Telford, who came twenty-five years later, used the same material but in a different manner. In Macadam's talk to committees of Parliament and to his workmen, he always enforced the idea that the whole secret of making a good road was to keep its earth-bed dry ; that the ground was the real road and must bear the weight of the stones, as well as of the traffic, and that the subsoil, however bad, would carry any weight if made dry by drainage and kept dry by an impervious covering. In this requirement Telford and all skillful road makers fully agree. This dry roadbed. Macadam covered with a layer of road metal of a finished thickness of five to ten inches 150 be M C 3 o « •^ ^ 3 « _. *^ 1- - O X J i^HliilHBHHHaBaB^ CITY ROADS AND PAVEMENTS. (varying with the weight of traffic), composed of small angular fragments of the hardest and toughest rock, broken to a uniform size, as nearly as possible to one and one-half inch cubes, or six ounces each in weight. No dimension larger than two inches was allowed, and any piece too large for a workman to put in his mouth was to be broken again. In the matter of Telford's foundation for a broken stone road and Macadam's omission of it, there are wide differences of opinion and of practice: French and English engineers generally omitting the telford foundation and many American engineers seeming to tend toward the same practice, or to limiting the use of telford foundations to those portions of roads where the earth subgrade is not firm. The latter practice is best because where the sub- grade is firm, the telford base serves as an anvil upon which the shocks of traffic break the fragments which form the surface. Where the sub-grade is dry and well drained, the telford base has the effect to more quickly remove the moisture which helps the binder to bed and to hold the surface-fragments. Sprinkling is done in dry weather to supply this moisture and without it the road " ravels." This raveling will occur sooner on a dry section of telford road than on a similar section of a macadam road, but this difference is not so important when the roadway is a city street which is sprinkled and shaded. When the sub-grade tends to being wet, the telford base is desirable as a foundation, and costs, when local stone is at hand, thirty to thirty-five cents per square yard. 152 TELFORD ROADWAYS. COST. As to the relative cost of the two methods, it is usual that telford is somewhat more expensive, but the fol- lowing does not so show. At Somerville, N. J., on October 22d, 1900, proposals were received for two miles of eight-inch macadam and for six miles of ten-inch telford and macadam, each of trap rock, each twelve feet in width, and each including about 2,000 cubic yards of excavation per mile : the prices were in cents per square yard: Average at Max. Min. 14 bids. For eight-inch macadam roadway complete. . 8;^ 50 62 For ten-inch telford roadway complete 8;^ 50 66 For the stone roadways only, not including grading and drainage, for eight roads built in New Jersey, dur- ing 1900, the average costs were: For four six-inch macadam roads, fifty-three cents per square yard ; for four eight-inch telford roads, fifty- one cents per square yard. During 1901, as stated in the report of Henry I. Budd, commissioner, nine eight-inch macadam roads averaged seventy-seven cents per square yard and three eight-inch telford roads averaged sixty-one cents per square yard. TELFORD ROADWAYS. The general requirements for construction of telford roadways are similar in the different states with the exceptions which will be named: the earth roadbed or subgrade, is excavated and carefully rolled and formed as for a macadam road, conforming to the })ro- posed cross-sections and twelve inches below the estab- lished grade of the finished road. 153 CITY ROADS AND PAVEMENTS. On this subgrade are then placed by hand the stones forming the telford foundation, which may vary in size as shown below: each stone must be set vertically upon its broadest edge, lengthwise across the road and forming courses and breaking joints with the next course, so as to form a close and firm pavement. The stones are then bound by inserting and driving stones of proper size and shape to wedge the stones in their proper position. All projecting points are then broken with a sledge or hammer so that no projections shall be within four inches of the finished grade-line. The telford foundation is then rolled with a steam roller of ten or more tons weight, until all stones are firmly bedded and none move under the roller. All depres- sions are then filled with stone chips not larger than two and one-half inches, and the whole left true and even and four inches below the line of finished grade and cross-section. A good workman will average about twenty minutes in setting a square yard of this telford foundation, which may be formed of any kind of quarried rock which is most available : cobble-stones are not suitable. The practice in 1901 in the states named is here shown : Sizes of Stone for Telford Foundation, in Inches. STATE. Depth, as SET ON EDGE. Width, as SET. Length, set across ROAD. Remarks Max. Mm. Max. 4 10 10 1 10 Min. Max. Min. j New Tersev. Mass Conn 8 6 8 8 8 5 8 6 4 6 4 10 15 6 8 6 Alternate end-stones double length. Two inches gravel rolled on sub-grade as base. Macadam covering formed in one layer. Used only on unstable ground as foundation for macadam. New York . . 154 CITV ROADS AM) I'AVIIMKNTS. The re(juir(jincnts for formin^^ the four inches or six iiiclu'S of l)rokcn stone roadway upon this telford foundation are tlie same as for re^^ular macadani. ()f the inilea;_;"e of l)r()ken-slone roads ])uilt ])y State aid (hu"in^ Kjoo, telford foundation was used for one- sixth in New Jersey, one-seventh in Coiuiecticut, one tliii'ty-ei^lith in Massachusetts and none in New York. During- 1901, New Jersey used tlie same ])ro|)ortion as in 1900. NEKI) OF r>INI)i;K Willi UROKKN S'l'ONK. Macadam required that tlie layer of regular frag- ments sliould l)e s]:)read on the earth roadbed, to l^e con- sohdated ])y the wlieels of ]:)assin^ vehicles, without tlie aid of any fine material or of " binder" of any sort. This recjuirement was impracticable and j^robal^ly could not be enforced, and exj:)erience has shown that it is not desirable that it should be enforced. Such fragments, loosely jailed or spread, have about forty-six to forty-ei^ht ])er cent of void sj)aces, and will pack by i-ollin^ to about three-fourths of their thickness when loose. The consohdation of ])erfectly clean, re^^ular, angular fragments of trap rock, free from screening's or binder of any sort, was thoroughly tried by Mr. Grant in Cen- tral park, New York city, in i(S6o. A ])iece of road covered with Macadam's ideal road metal, free from binder, was rolled for several days, until the fragments were worn and rounded, without hrm consolidation being effected, and this experience has been recently repeated elsewhere. Road material which can be ])acked without binder must be of a ])()or (pialit}', which will supply itself ^5(> MODKS Ol' I'SK OK lUNDI.K. with l)iiuk'r 1)\- ruadih' griiuliiig" iiUo dii^t and small j)ic'(X's. 'rc'lford's sNstrin dilkTcd radicalh' in that he first covered the earth roadbed with a i-oiigh pax'ement ol firmly set stones, and that the wearing" la\er of broken fragments xaried in si/e, and that a hinder of fine material was spread over the surface to help in its consolidation. Moi)i:s oi" i;si'; of r,i\i)i:K. This is one of the most important features of mac- adam road construction, and the different modes which produce sucx'cssful results on State roads are therefore gi\'en in detail. /// Jiiigland there are now various methods in use, l)ut as a general thing Macadam's method of using ])erfectly clean fragments of hand-broken rock is not now followed. The commonest ])ractice seems to be to use tw'enty-five ])er cent of binder called "hoggin," consisting of a mixture of loam, coarse sand and small graxel. This "hoggin" being worked into the la\('!- of broken stone by flooding the roadwa)' with water. Jji pyance, where the greatest care is given to road construction and maintenaiKX', twent}'-ri\'e ])er (x-nt ol sand is generall\' used with the broken rock as a binder. This is washed to fill the \'oids between the fragments of rock, with a final addition of ehalky dirt and watei- to fill the voids in the sand. See (piotation on |)age I 69. In llic United States, where little or no stone is now l)roken by hand, ex])erience has satisfied most /Xmeri- ean engineers that the roads wear better and have less dust and fewer loose stones if binder is put upon the '57 CITY ROADS AND PAVEMENTS. consolidated layer of crushed stone to fill the spaces which remain after rolling, and this binder is usually the stone dust and the small fragments from the crusher which pass through the circular holes, half an inch in diameter, of a revolving cylindrical screen. The use of binder is the same whether the construction is tel- ford or macadam. In Nczu Jersey, after the lower course of broken stone has been rolled until compacted, trap rock screen- ings one-half inch to dust, free from loam or clay, are spread over the lower course in a uniform layer and the course is again rolled until the stones cease to sink or creep in front of the roller; water being applied in advance of the roller if required. The same treatment is given to the top course. This is then covered with a mixture in equal parts of three-fourths inch crushed trap and of half inch trap screenings, properly mixed and spread in sufificient thickness to make a smooth and uniform surface which is rolled until hard. Sandy loam is used with good results upon some New Jersey roads. Ill Connecticut^ after each of the two courses has been rolled until solid and iim, dry trap rock screen- ings not larger than one-half inch are scattered over the surface so as to fill all interstices and the roller is then run over the road to shake in the dust. The sprinkler is then used to wash in the screenings and then more screenings are added, rolled dry and then sprinkled, and these processes are repeated for each course until all interstices are completely filled. When the top course has thus been made firm and smooth, it is then covered with one inch of screenings to form a wearing surface. 158 MODES OF USE OF lUNDFR. /;/ Massachusetts, tlic lower course is tliorouglily compacted by rolling, but no screenings or filler are spread or used upon it. After the top course has also been thoroughly compaced by rolling, screenings of the same kind of stone which forms the top course are laid on in just sufficient quantity to cover the stone and are then watered and rolled until the mud flushes to the surface. The screenings are not treated as a part of the wearing surface but are used simply to hold the larger stone in place, using as little as possible. In N'ciu Yoi'k, the screenings used as filler are usu- ally limestone when the road-material is brought from a distance, but are often the product of the local crushed stone when local rock is fit for use ; sometimes local rock and its screenings are used for the lower course only, but when possible they are used for the top also. In some cases when local granitic rocks are used, the screenings for the top course are caused to bind prop- erly by mixing an equal amount of limestone screen- ings with granitic screenings. In other cases good results have been obtained by mixing an equal amount of clean sand with the granitic screenings. Trap and granite and quartzite screenings are limited to a maxi- mum of one-half inch, but those of softer rocks are lim- ited to three-quarter inch. After the first course of broken stone has been rolled until the stones do not creep or weave ahead of the roller, the dry screenings are spread uniformly to a depth of one-half inch and are then rolled dry and are swept with brooms of steel or rattan until the screenings disappear among the stones, when the process is repeated until no more will go in while dry: the surface is then wet with a sprinkler (unless the subgrade is of clay), using water freely until 159 CITY ROADS AND PAVEMENTS. all voids are filled, leaving the surface of the stones free from screenings. See page 175. The top course is then spread and rolled and treated in the same manner in sections of about 300 feet length, water being freely used and the rolling continued until a grout has been formed of the stone-dust and water and until a wave of this grout is pushed before the wheels of the roller. After this effect is produced, screenings are spread and rolled, leaving three-eighths of an inch depth for a wearing surface. After forty- eight hours, or when the surface has dried, the road is again rolled and sprinkled and then opened to traf- fic, being meantime sprinkled daily for thirty days. QUALITY OF SCREENINGS. Trap. — The best "binder" for the top course, all things considered, is probably a mixture of three parts of trap-rock dust and screenings, with two parts of smooth sand not too coarse. In addition to its tough- ness, trap-rock dust has the advantage as compared with limestone dust, of having a greater specific gravity, so that it does not blow readily. If this mixture fails to " bind," or if it " ravels " afterward, a different grade of sand may help it, or a small addition of one-fourth or less of cementitious limestone screenings, like that from Tompkins Cove, will certainly make it bind. Limestone. — Some kinds of limestone screenings make a sticky paste, which is very bad, and it is important to select carefully and to study the effects closely. Cementitious limestone dust and screenings " bind " broken stone better than will any other mate- rial, and many experienced road-makers consider that limestone of some kind is necessary to make a good 160 QUALITY OF SCREENINGS. road; but the facts remain as detailed on pages 157, 158 that vast extents of perfect roads have been built and maintained without it, both in this country and abroad, during years past as well as recently. Granite. — The screenings crushed from granitic rocks and from gneiss have in some cases been successfully used to bind the crushed rock from which they were screened. In other cases, during 1901, perfect results have been obtained from granite screenings which would not " bind " by mixing with them an equal quan- tity of carefully-chosen local sand. Qtcantity of Screeni7igs. — The actual quantity of screenings required to thus bind the crushed stone and to fill the voids, varies somewhat with the character of the rock and with the degree to which it is crushed and ground together by the roller: with trap rock, w^hich is not crushed by rolling, the loose yardage of screenings needed to fill the voids will equal thirty- three per cent of the loose yardage of the crushed rock measured in the bin : with some gneiss, or with soft limestone, or with sandstone, the screenings may not exceed twenty-five per cent of the loose yardage of the crushed stone measured in the bin. A fair average with the various rocks will be thirty per cent, which will be ample if the screenings are not wasted. 161 MAXIMUM GRADES FOR MACADAM ROADS. There is a wide difference between theory and prac- tice in the matter of maximum grades on which broken- stone roads may be built and maintained. Grades of less than five feet per loo feet are not only better for the traveling public, but can also be built and main- tained at less cost, because it is more diflficult to roll macadam on steeper grades, and because the fragments are loosened by horses toe-calks and are washed by rain-fall. In the construction by state aid in the states already named, the roads are necessarily outside of corporate limits and are usually old highways on which the steeper grade can be reduced by cutting the tops of the hills and by filling the valleys, or in extreme cases by changing the line of the road and making a new loca- tion around a hill instead of going over its top. In this way, the maximum grade on state work in Massa- chusetts and in New York is nominally five feet per hundred because this is considered to be the most economical for the convenience of travel and for the cost of maintenance. In both these states, grades as steep as six and one-fourth feet per hundred are found necessary in some cases. 162 ml' ■ .ti-..., > * f/f \ ■VVl .5^ X _, H ^ a; c CITY ROADS AND PAVEMENTS. In New Jersey, among the roads built in 1900 are the following upon which the grades are steep: NAME OF ROAD. Construction. Thickness, inches. Width of macadam, ft. Max. grade, ft. and tenths per 100 ft. East Passaic avenue Budd's Lake road Passaic ave. (E. bank Passaic river) Patterson and Hamburg Turnpike Mendham-Bernardville. . Telford .... Macadam. . . Telford .... Macndam .. Macadam . . 8 6 10 t 16 10 to 16 20 16 12 7-5 7-5 8.86 9 10.75 Upon city streets, however, it is often difficult to make any radical change in the grade, and always im- possible to avoid hills by change of location, so that grades which are steeper than these are sometimes used, and with surprisingly good results. The city of Newton, Massachusetts, comprises fifteen villages in an area of twenty square miles, containing some sixty miles of the finest macadam roads, which are built and maintained in perfect order by commis- sioner Chas. W. Ross, formerly member of the state highway commission. Among these finely kept roads are the following : NAME. Length of steep grade. Grades in Village. Street. feet per loo feet. West Newton .... West Newton .... Newtonville Newtonville Chestnut street Mt. Vernon street . . Highland avenue. . . Otis street 1000 feet J 000 feet 1000 feet 1200 feet 700 feet 600 feet 1500 feet 1000 feet 9 feet 9 feet 10 feet 10 feet West Newton .... West Newton .... Newton Prospect street Putnam street Bellevue avenue. . . . Newtonville avenue. 10 feet 10 feet 9 feet 12 feet Newtonville 164 STEEP CxRADES FOR MACADAM ROADS. All streets having grades steeper than fi\'e feet j^er I GO have paved gutters three feet or more in widtli for which concrete is preferred to cobbles as being more durable, being free from weeds, and giving the best flow. The city of Waltham, Mass., has fine macadam streets with the following described steep grades built since 1895: NAME OF STREET. Length of steep grade. Width of mac- adam in ft. Max. grade, in feet per 100 feet. Main street Newton street I COO feet 500 feet 700 feet 400 feet 400 feet 40 feet 20 feet 20 feet 20 feet 20 feet 7 8 Plympton street Bellevue street 9 12 Plympton street 13 These streets have paved gutters three and one-half feet wide and the cost of their maintenance after the first year is stated by superintendent R. A.Jones to be about one cent per square yard per year. Clinton, Mass., has the following described macadam streets with steep grades, maintained by superintendent Loring B. Walker: NAME OF STREET. Length of steep grade. Width of macadam in feet. Max. grade, in feet per 100 feet. Boylston street Chestnut street 6000 feet 1800 feet 3000 feet 3000 feet 3000 feet 18 feet 14 feet 24 feet 24 feet 24 feet 6 7 8 Sterling street Church street 9 10 Main street These streets have paved gutters four feet wide. Cambridge, Mass., has steep grades on Lancaster street, Humbolt street and Washington avenue, main- •65 CITY ROADS AND PAVEMENTS. tainecl by superintendent R. A. Brown. Medford has a steep grade on High street while there are also steep grades, kept in good condition, in Brookline, Chelsea, Maiden, Winchester, Woburn and Somerville, Mass. On Staten Island, now the Borough of Richmond of the city of New York, there were built from 1895 to 1 90 1, by Henry P. Morrison, M. Am. Soc. C. E., 183 miles of macadam streets, w^hich include some having steep grades which are described as follows : they are now in charge of Louis L. Tribus, M. Am. Soc. C. E. : XAME. T.ength of steep grade. Width of macadam in feet. Max. grade Village. Street. in feet per ICO feet. Garretson's . . Ocean terrace. . . . 800 feet 16 feet 9 Garretson's . . Prospect avenue. . 500 feet 16 feet 10 Stapleton. . . . Orient avenue 100 feet 16 feet 10 Stapleton. . . . Orient avenue. . . . 100 feet 16 feet 16 Garretson's . . Four Corners' road 500 feet 16 feet 1 1 Stapleton. . . . Trossack road .... 730 feet 16 feet 12 Clifton Hillside avenue 1600 feet 16 feet 12 Stapleton. . . . Occident avenue . 100 feet 16 feet II Stapleton. . . . Occident avenue . 100 feet 16 feet 13 Stapleton. . . . Occident avenue . 100 feet 16 feet 14 Stapleton. . . . Occident avenue . 100 feet 16 feet 16 Stapleton. . . . Louis street 300 feet 16 feet II Stapleton .... Louis street 200 feet 16 feet 20 These streets are formed of eight inches of crushed trap (except Trossack avenue which is six inches) all thoroughly rolled with four inches of crown, and all except three have paved gutters. CONSTRUCTION OF A MACADAM ROAD. The earth roadbed must first be drained, and in flat streets where the usual deep side-ditches are impossible, there must be shallow brick paved gutters to take the 166 SUBGRADE. surface water at each side of the street and also porous tile drains, two feet below them, to collect the [ground water and carry it to the sewers. See jxige lo. Curbs will usually be required for a city street. SUBGRADE. The subgrade, must then be cleared of all soft and loose material, preparatory to forming it on the best grades obtainable, with a regular crown or con\'e.\ity of about one-half inch per foot for any grade up to five per cent and for widths up to sixteen feet, and of three-fourths inch per foot for steeper grades. (See page 36.) Old roadbeds usually have more or less hard and firm material beneath the objectionable dust and mud, ar.d this firm substratum should be dis- turbed as little as possible by establishing the grade line high enough to avoid it. A steam roller passing over an earth roadbed will disclose the existence of a surprising number of yield- ing places and soft spots which could never be found in any other way, but which can readily be filled, or excavated and refilled and re-rolled, until the earth is regular and equally hard throughout. Instead of first forming the side-ditches and the crowned subgrade, as is usually done, it is sometimes better practice and easier for the roller to grade the road- bed flat in cross-section and at about two inches below the desired elevation of the center of the crowned sub- grade ; deferring the ditches until the last, unless their excavation is at once necessary to provide grading material or to take storm water. On this flat roadbed, use the roller and adniit trafiic until the whole surface is so hard that the wheels of a 167 CITY ROADS AND PAVEMENTS. loaded wagon leave no ruts. When ready to prepare for spreading stone, stake out the proposed macadam and drive twenty-four inch by one-half inch steel pins fifty feet apart along each edge and stretch a cord at the correct elevation of the proposed surface of the base course : then use square-end shovels and picks to cut down four inches along the cords, sloping the cut to nothing at three feet toward the center for a sixteen feet roadway, or more for a wider one : throw the excavated material into the center to form the crown and roll it till firm, making the center at the right elevation and forming the desired crown to receive the stone. The side ditches can be left to be dug and paved after the completion of the macadam roadway. Several expe- rienced contractors who have doubtfully tried this method, have adopted it as their regular practice. All precautions must be taken to secure the per- manence and solidity and dryness of the subgrade, and it is an economy for the contractor during construction to get it as hard as described because this prevents the loss of costly crushed stone, and it is also an economy in future maintenance by prolonging the life of the roadway. Broken stone roads have been " built " in cities by spreading six inches of good crushed trap upon the mud and dust of a soft subgrade with the result of total failure within two years. Sand Subgrade. — A subgrade of sand which will not consolidate even when wet, may be fixed by cover- ing with three inches of loam, or of shale or gravel, or with a thin layer of broken stone, either of which will probably consolidate under the roller after wetting. Peculiarly loose sand is sometimes found, into which 1 68 SUBGRADE. one's arm can be thrust to the elbow, and this has been bound as above. Tliis difficult condition is also well met in an article entitled " Economic Design of Streets and Pavements," by Halbert Powers Gillette, re-printed from the Engineering News, in the very complete 1901 report of the highway commissioner for New Jersey, Henry I. Budd, as follows: " Sand can be made quite as unyielding as gravel simply by filling the voids with fine dust or pulverized sand. No rolling is necessary. "Water, if supplied in abundance, will puddle sand to which fine dust has been supplied, until the sand becomes hard and unyielding." A telford base may be required as discussed on page 152. A layer, one and one-half inches thick, of three- quarter inch to one inch broken stone, coated with hot bitumen and rolled at once, will serve in an extreme case where simpler ways fail. Clay Subgrade. — Subgrades of slippery clay showing increasing waves when rolled with a twelve ton to fif- teen ton roller, have been consolidated, after subdrain- ing with buried tiles, by covering the clay with a layer of freshly-cut straw and then rolling with a lighter roller, ten tons in weight. This has also been done by covering the clay with a single layer of quarter inch to half inch green brush, rolled into the moist clay and then covered with an inch of sand and again rolled. Small areas or " pockets " of springy wet clay must be removed, or must be drained and then covered with a layer of gravel or coarse sand. Settlhig a Clay Subgrade. — It is sometimes best, and has been done with good results, to rough-grade a clayey subgrade and to let it stand under traffic for some 169 CITY ROADS AND PAVEMENTS. months, or better through a winter, before preparing it to receive the broken stone. Sandy Loam Subgrade. — This is most difficult when the particles are very fine, so that the capillary attrac- tion prevents sub-drains from taking the ground- water; in such case, this part of the road must be watched during the first wet season after completion, and if it shows signs of yielding under traffic, the layer of broken stone must be increased in thickness, as is discussed on page 177, in the quotation from W. E. McClintock, M. Am. Soc. C. E. Various expedients must be tried until one is found, by which the subgrade will remain firm and smooth when the broken stone is spread and rolled upon it, so that the fragments shall not work down into the sub- grade, nor the material of the subgrade w^ork up among the fragments, under the action of the roller. The stone thus saved is worth more than the cost of this special work. Remove Stones. — Stones or rocks lying within half a foot of the top of the subgrade, and which are larger than six inches, should be removed, lest they serve as anvils on which traffic will crush the road-metal. QUALITY OF ROCK TO BE BROKEN. The rock should be hard, tough, durable and uni- form in character, fracturing with a toothed surface and showing a tendency to break into cubes rather than into flakes. This latter pecularity occurs with some rocks which would otherwise be good, and in one case was found to be the direct result of excessive use of dynamite in the quarry. 170 CRUSllINC. The rock should ]ia\'c a compositioii wliicli cements wlieii wet and rolled, and should come clean from the Tailings larger than ^ inrhe to return to cruslirr. Wagon loading c rushed sloiie from Inn. Screens and bins for screenings and three sizes of stones. Cart dumping rork from r|narr>' onto iilallorni over crusher, Crnslier prndncina 135 euliic j(ls. crushed stone per day. CRUSHIXCi AND SCREEXIXG ROCK. quarry to the crusher. A softer rock may be crushed for the base course, and its screenings will usually form a good filler for it. (See page i6i.) CRUSHING. The crusher should be placed where the rock will pass down from the ledge through the crusher and through the bins into the wagons, and then down-hill to the work. The crusher should be set to produce the largest size specified, and the whole j^roduct should then be screened through a series of three revolving 171 CITY ROADS AND PAVEMENTS. screens or cylinders pierced with circular holes, set on a slope so that the material passes slowly as the screens revolve into separate bins for each size. Thin slabs and long pieces and the " tailings," should be re-crushed. Sixty cubic yards of solid rock in the ledge allowing for quarry w^aste will make about loo cubic yards of loose rock which will produce about 125 to 135 cubic yards of the different sizes measured separately. The following results were obtained in crushing hard flinty limestone weighing 168 pounds per solid cubic foot, or 2 1 7 1 pounds per cubic yard of quarry frag- ments of one to two cubic foot each, of which a mass showed fifty-two per cent of voids and 100 cubic yards produced as follows: Size of screened Number of Weight per Per cent of products. cubic var ds. cubic foot. voids. inch to I y2 inch . . 1 ^5 1 96 pounds 43 J^ inch to ^8 inch. . (91.5 pounds 45-5 Y^ inch to Y^g- inch . . 14 92 pounds 45-2 -^-^ inch to dust inch . 19 93 pounds 44.6 One hundred and eighty cubic yards of quarry-rock were crushed in ten hours and the product was screened and put in bins and cars at a total cost for plant, fuel and wages of fourteen cents per cubic yard of product. The usual cost is twenty cents, and with a smaller crusher, thirty cents. The screens should be selected to produce the re- quired sizes, two and one-half inch circular holes giving what are known to dealers as " two inch " stone : one and one-fourth inch holes giving " one inch," used for the binder-coat of asphalt pavement : one inch holes giving " three-fourths inch : " one-half inch holes giving " screenings : " one-fourth inch holes giving " one-eighth inch dust." 172 Preparing subgrade. Finishing' subgrade. .ifHi T Ill^dP?-;-; .^ - ■ ,:rJ^i^l^i^A Snreading and 1 111 lation stone. RIVER-ROAD NEAR BLFlALt), NEW YORK. Surface of two inches of trap rock on base of four inches of limestone. Built by State Engineer E. A. Bond, :\I. Am. Soc. C. E., in 1900. CITY ROADS AND PAVEMENTS. The required sizes vary as indicated in the foHowing table showing the practice during 190 1-2 in the States named : Sizes of Broken Stone and Thickness of Courses, in Inches. Lower Course OF Macadam. Upper Course OF Macadam. Surface. i STATE. Size of Frag- ments. Thick- ness after roll- ing. Size of Frag- ments. Thick- ness after roll- ing. Size of Frag- ments. Thick- ness after roll- ing. Size not used. Min. Max. Min. Max. Min. Max. Kew Jersey Massachusetts. Connecticut . . . New York IK 3 2 3 4 4 4 4 1 1 1 IK 2 2 dust dust dust dtist y^ smooth surface smooth j surface 1 Ktol none. Ktoi none. * * Oiie-lialf inch to one inch spreail on siib^rade as oiie-tliiid of the base course. FORMATION OF LOWER COURSE. The thickness of the layer of loose stone spread for this course should be gauged by five and one-half inch cubes of wood placed upon the subgrade, including a bottom layer not more than one and one-half inches thick of that part of the crusher product not otherwise required. The stone should be uniformly spread to this depth, beginning furthest from the source of supply in order to avoid driving over the loose stone, and using spreader- wagons to uniformly distribute it. If ordinary wagons are used, the stone should be shoveled from the wagons or from the roadside. - If dumped in large piles upon the subgrade of the road, the position of each pile will be made evident after the road is finished. When sev- eral hundred feet of roadway have been covered, the roll- ing should begin along each edge, lapping on to the 174 FORMATION OF TOP COURSE. earth shoulder aixl rollinij^ cacli side several times iiiuil the fragments do not ereep or weave before the roller when they will be compressed to four iiiches. No screenings or water should be put on till after this: the use of dry screenings is described on page 159. When the lower course is properly filled and bound it will be so firm and solid that loaded wagons can pass over it without leaving an)' mark, but the surface of the stone should be free from screenings. FORMATION OF TOP COURSE. The top course, perferably of trap, is then spread in the same manner, using two and three-fourths inch gauge-blocks and rolling the loose stone to two iiiches, and until the fragments do not creep and weave, before spreading the dry screenings as described on page 160. Sometimes it is required that the rolling of the top course shall continue until the material is packed so firmly that an inch cube of trap laid upon the finished surface shall crush under the roller without sinking into the road surface. A properly made macadam pavement resembles a mass of concrete, and in several cases has proved self- supporting when the earth beneath it has been washed out by floods. /D CITY ROADS AND PAVEMENTS. r ■ ( ' .-!^^^^^^|H^^^HHHHi j f^i '^^^^^^^^^^^^^^^^H f ■, ^fe^ ^H^^^^^^^^^^^^^H^^hJ^^^hBI^^^^I , i W'l^^^^^^H^^IHH f . , ' ' ii^^^^KK^^ r \ - 1 1 .jh'uM^^^^^K^M o < g 3 < c^ w > o o I— I e w o I— ( >1 I— I cc O P^ < Q halt, 26, 56 ; block stone, 26 ; cedar block 26 Kansas City, Mo.— asphalt, 26, 126; block stone, 26; brick, 84, 97; cedar blocks, 26 ; cypress blocks. 68 Keokuk, Ia. — brick. 84 Kenosha, Wis. — brick 84 Kewanee, III. — brick 99, 100 Kingston, N. Y. — wheel tracks, stone 22, 23 Lafayette, Ind. — asphalt, 56 ; brick , 84 Lancaster, Pa. — brick 84 Lexington, Ky. — brick , 84 Lincoln, Neb. — brick. 84 Little Falls, N. Y. — jrranite near . . 141 LocKPORT, N. Y. — brick 84 Long Island City, N. Y. — asphalt 123 Los Angeles, Cal — asphalt 56 Louisville, Ky. — brick ... 84, 91 Loads, comparative 25 London — Australian hardwood blocks 71 Macadam 180 Lowell, Mass — bituminous macadam. 132, 135 Macadam pavement— (See Broken Stone Roads, 138) Malden, Mass — macadam 1 65 Mansfield, Ohio.— asphalt, 118, 130; brick 95,98, 130 Marion, Ohio.— asphalt, 118, 130; brick 130 Massillon, Ohio. — brick 84 Melbourne, Australia. — hardwood blocks 74 Medford, Mass — macadam 138, 166 Memphis, Tenn. — brick 84 Meriden, Conn. — asphalt, 118; brick 95 Milw. ukie, Wis.— asphalt, 26, 56, 118, 120, 130 ; block stone, 26 ; brick, 95, 98. 130 ; cedar blocks 26, 68 Minneapolis, Minn.— asphalt, 26, 130 ; block stone, 26 63 ; brick, 130 ; wood block , 26, 68 Montreal, Canada. — asphalt, 56 ; tamarack blocks 68 Mdncie, Ind. — asphalt 118 Nashville, Tenn. — brick 98 Neuchatel, Switzerland — asphalt blocks 128 Newark, N. J. — asphalt. 104 192 INDEX. r.v(;E. New Bedford, Mass — bituminous macadam 135 New Cumberland, W. Va. — brick 87 New Haven, Conn. — asphalt, 130 ; brick 130 New Orleans, La.— asphalt, 2G, HG, 5G, 118, 120, 130 ; block stone, 26, 36 ; brick, 95, 130 ; wood block 36 Newport News, Va. — asphalt 56 New RocHELLE, N. Y. — woodblocks 78 Newton, Mass. — macadam 138, 164 New Yor:-: City, boroughs of Brooklyn — Asphalt 26, 28, 36, 56, 106, 117, 126 Block stone 26, 36, 64 Cobbles . .. 58,116 Curbs 38 Macadam 139 Bronx — Asphalt 107 Macadam . . . , 139 Manhattan — Asphalt 26, 36, 56, 102, 104, 107, 113, 118, 121, 126 Asphalt block 127, 129 Bituminous macadam 135 Block stone 26, 36, 59, 64 Cobbles 58 Curbs 38 Macadam 139 Wood blocks 'M, 67 Queens — Macadam 139 Richmond — Macadam 139, 166 Niagara Falls, N. Y. — asphalt base, 55 ; brick 97 Norwich, N. Y. — bituminous macadam 135 Oakland. Cal. — redwood blocks 68 Olean, N. v.— brick 84 Omaha, Neb.— asphalt, 26, 36, 56, 118 ; block stone, 26, 36 ; brick, 84 ; cypress blocks, 68 ; wood block 36 Oswego, N. Y. — asphalt, frontispiece, 120, 126 ; block stone, 26 ; brick, frontispiece Ottawa, III.— brick 84 Owensboro, Ky\ — asphalt 120 Paris — asphalt, 103; concrete base, 53; macadam, 180, 181, J82; wood blocks 70 Parkersburcj, "W. Ya. — brick 98 Pawtucket, R I. — bituminous macadam 135 Peoria, III —asphalt, 56, 118, 120, 130 ; brick 84, 95, 98 Philadelphia, Pa. — asphalt, 26, 36, 104, 130 ; block stone, 26, 36, 64 ; brick, 84, 87, 98, 130; wood block 36, 67 Pittsburg, Pa. — asphalt, 26, 56, 118, 119 ; block stone 26 Pontiac, Mich — asphalt block 128 Portland, Me. — asphalt, 26 ; block stone 26 Preface , 5 Pressure — of wheels, 13 ; of structures 15 Providence, R. I. — asphalt, 26, 56 ; block stone, 26; brick ,84, 99 QuiNCY, III. — brick - 84 Rails — S])lices of, 41 ; stone 21 Richmond, Va. — block stone 64 Rochester, N. Y.— asphalt, 26, 56, 119, 120, 130; block stone, 26, 61, 62, 64 ; brick, 84, 100, 130 ; car tracks 40, 41 193 INDEX. PAGE. RocKFORD, III. — brick 84 Rock Island, III. — brick 84 ROLLIN G . . „ 10 Dirt roads 12 Roman roads 17 Construction of 18 Cost of , 18 Thickness of 16 RoNDouT, N. v. — wheel tracks, stone 23 St. Joseph. Mo.— asphalt, 118, 130; brick 98, 100, 130 St. Louis, Mo.— block stone, 64 ; brick 81, 83, 90 St. Paul, Minn.— asphalt, 26, 56, 118, 120, 130 ; block stone, 26. 63, 64 ; brick, 84, 95, 100, 130 ; cedar block, 26 ; curbs 39 Salem, N. J. — Bituminous macadam 135 Salt Lake City, Utah — asphalt „ ,, 118 San Ai^tonio, Tex. — asphalt, 56, 120 ; mesquite blocks 68 Sand — Cushion 34, 95 Binder for macadam roads 157, 159, 161 Filler for joints 61, 96 Strewn on pavement 28, 71, 121 For concrete c 48 Washing 48 Sandusky, Ohio— asphalt, 118, 120, 130 ; brick 95, 130 San Francisco, Cal. — asphalt, 56, 106, 118; block stone, 26; redwood blocks 68 ScHEN ectady, N. Y. — wheel tracks, stone 19, 22 ScHU ylerville, N. Y. — trap-rock near 140 ycRANToN, Pa. — asphalt, 56, 118, 130; brick 84, 95, 130 Sewers — increased size 8 Sidney, N. S. W. — concrete base 53 ; Australian hard-wood blocks.... 71 Somerville, N. J. — macadam and teltord streets 153 Somekville, Ma!?s. — macadam streets 165 Splices of rails — electrical, 41 ; cast iron 41 Spokane, Wash. — asphalt 56 Springfield III. — brick .... 84 Springfield, Mass. — asphalt, 118, 130 ; I rick, 95, 130 ; macadam, 138 ; wood blocks , , 78 Sprinkler , 12 Steam railroad, first passenger railroad , 20 Steam roller , 11 Weight 12 Tests 12 Durability ... 13 Steep grades — asphalt, 27, 118 ; bituminous macadam, 30, 135; block stone, 28, 29 ; brick, 28, 98 ; broken stone, 29, 164, 166 ; wood block. 29 Stone rails 21 Stonk wheel-tracks (See Wheel-Tracks) 18 Streets — residence, 7 ; width of 8 Sub-grade — drainage of, 9 ; rolling of, 42 ; test of. 42 Steueenyille, Ohio — brick , 84 Superior, Wis, — cedar blocks 68 Surface — crown of, 30, 95, 118 ; reduction of, 7; ideal, 30; curve ot, 34 Syracuse, N Y, — aspha't, 26, 28, 118 ; block stone, 26 ; brick 84 Taunton, Mass. — bituminous macadam 135 Terre Haute, Ind —asphalt, 118, 130: brick, 84, 91, 95 130 Tests— brick, 88, 89; cement, 43 ; stone 145, 149 Toledo, Ohio— asphalt, 26, 56, 118, 120, 130; asphalt block, 128 ; block stone, 26, 61,64; brick ..-84, 91, 98, 100, 130 194 INDEX. PAGE. Tolls 20, 23, 67 ToPEKA, Kan. — brick , 94 Toronto, Canada — asphalt, 56, 118, 130 ; brick, 95, 130 ; cedar blocks, 68 Traffic, pressure of. 13 Troy, N. Y.— asphalt, 118, 130; block stone, 64; brick 84, 95, 98, 130 Utica, N. Y— asphalt, 26, 56 ; block stone 26 Waltham, Mass. — macadam 165 Washington, D. C— asphalt, 26, 36, 56, 104, 107, 109, 130 ; asphalt l)lock, 127 ; block stone, 26, 36, 64 ; brick, 84, 130 ; curbs, 38 ; wood block . , 36 Watbrtown, N. Y. — brick 84 Wheeling, W. Va.— brick 84, 98 Wheel-Tracks, stone 18 Albany, N, Y 19 Kingston, N. Y 23 Schenectady, N. Y 19 Costof 21, 24 Wide tires 13 Wilmington, Del. — block stone, 26 ; brick 84 Winchester, Mass. — macadam 165 Winnipeg — asphalt 56 Wobdrn, Mass — macadam 165 Wood pavements 66 American, latest types 74 Creo-resinate 78 Cost ; g-uarantee 80 Creosote, quantity of ; details, 79 Localities 78 Pine heartwood ; ros n ; treatment 79 Kreodone-creosote 77 Cost ; creosote, quantity of 77 Details; guarantee; localities 77 Treatment.. — 77 American, older types — Cedar blocks, round 26, 67 Cost ; details ; extent 67, 68 Cedar, Oregon, creosoted — cost 70 Cedar, Washington, creosoted — heaved 70 Corduroy roads ... 66 Cypress blocks 68 Mesquite blocks 68 Pine blocks — various, 70, 79 ; yellow 68, 79 Plank roads. , -. 66 Redwood blocks 68 Tamarack blocks 68 Australian hard woods 71 Concrete base 72 Cost 71 Curbs ; details ; expansion joints 72 Life 74 Sanding 71 Crown 30, 32 Grades 28 Joints, grooved , 29 Noiseless 74-79 YoNKBRS, N. Y. — bituminous macadam , 135 195 ^\}\, 2a JUL 36 1902 ICOPYHEI TO CAT mv. JUL. 28 1902 HiL. 31 1902