GRANITE BLOCK PAVEMENT
69.Granite block pavement shall be laid upon a foundation of hydraulic cement concrete.[30]
70. Sub-grade and Foundation.—The sub-grade shall be prepared as specified in Section 26. The foundation shall be constructed in accordance with the requirements of Sections 28 to 38 inclusive.
71. Granite Blocks.—The blocks shall be made from sound, durable granite, of uniform texture, composition and hardness throughout. No outcrop, deteriorated, soft, brittle, or seamy stone shall be used. If the blocks are obtained from different quarries, or from different parts of the same quarry where the quality or appearance of the rock differs, the product of each must be kept separate and laid together on the street.[31]
The blocks shall be not less than eight (8) nor more than twelve (12) inches long, not less than three and one-half (3½) nor more than four and one-half (4½) inches wide, and not less than four and three-quarters (4¾) nor more than five and one-quarter (5¼) inches deep.[32]They shall be well-shaped, rectangular, with full edges and corners. Their tops shall not depart more than one-fourth (¼) inch from a true plane, and their sides shall be dressed so that joints between the courses will nowhere exceed three-fourths (¾) inch wide, and their ends so that end joints shall not exceedone-half (½) inch wide.[33]The size of the blocks may be varied where necessary to fit the pavement against or around bridge stones or other street structures.
72. Sand Cushion.—The foundation shall be cleaned of all dirt and rubbish. There shall then be spread evenly over it a layer of clean, coarse sand to a uniform depth of one and one-half (1½) inches.
73. Setting the Blocks.—The blocks shall be set in this bed of sand perpendicular to the street surface, with their length at right angles to the street, in courses extending entirely across the street, and at right angles to its axis, except at street intersections where the courses shall be arranged as the Engineer may direct.[34]Only stones of the same width shall be set in the same course. The stones in each course, and in adjoining courses, shall be set firmly against each other. The blocks shall be set in the sand bed in such a mannerthat their bottom surface shall rest evenly upon the sand and that their tops shall be even with each other and to such an elevation that after the pavement is rammed, as hereinafter directed, its general surface shall conform closely to the pavement datum. Stones in adjoining courses shall break joint not less than three (3) inches.
74. Ramming.[35]—After the blocks are set each individual block shall be thoroughly rammed to give it a firm bearing in the sand and to bring its top to the prescribed pavement datum. The rammers used shall have wooden faces not more than four inches in diameter, and shall weigh not less than thirty (30) pounds. Blocks or sections of blocks whose tops under the ramming remain above or sink below the pavement datum shall be taken up and reset so that after the ramming is completed their tops shall coincide with the pavement datum.
75. Filling the Joints.[36]—After the ramming specified in Sect. 74 shall have been completed, the joints between the paving blocks shall be filled in the following manner:
All the joints for a distance of three feet out from the curbstones, and three contiguous joints continuous across the street, with the included end joints, at intervals of about fifty (50) feet in the length of the street, shall be filled with gravel and bituminous paving cement. The gravel used shall be of such size that all will pass through a screen having five-eighths (⅝) inch meshes, and all will be held on a screen having one-fourth (¼) inch meshes. When used, the gravel must be free from refuse and street dirt.The bituminous paving cement shall be composed by weight of straight-run coal-tar pitch of the hardness commonly known as number six, to which has been added and thoroughly mixed, while both are in a melted condition, twenty per cent. (20%) by weight of refined Trinidad asphalt, or other asphalt, equal for the purpose, and twenty per cent. (20%) by weight of Portland cement. These ingredients must be thoroughly mixed, and kept agitated until used.[37]
The joints will first be filled with the gravel, which shall be perfectly dry, and heated so that when put in the joints it will be at a temperature of about three hundred (300) degrees F. The paving cement, heated to a temperature of about three hundred (300) degrees F., shall be at once, while the gravel is still hot, poured from a spouted vessel into the joints until the interstices of the gravel are entirely filled to the surface of the pavement, repouring being resorted to to accomplish this result whenever necessary.
All the joints in the pavement other than those named above shall then be completely filled with Portland cement grout, in the following manner:
The grout shall be composed of equal parts by volume of sand (Sect. 30) and Portland cement (Sect. 29), a quick-setting cement being preferred. The sand and cement shall be first thoroughly mixed dry and then enough water added to make a grout of such consistency that it will flow like thick cream, and the mixing continued until a homogeneous mass is produced and until the grout is applied to the pavement. The grout shall be prepared in water-tight boxes of a convenient size. Before applying the grout the pavement shall be thoroughly dampened by sprinkling. The grout shall be removed from the mixing box and spread over the pavement with scoop shovels, in two courses, the first being sufficient to about half fill the joints, and the second, which shall be applied before the first has begun to set, shall be sufficient to entirely fill the remaining space in the joints. As the grout is applied to the pavement it shall be swept about with brooms until it all enters the joints.
76. Order of Work.—The sand bed shall not be put in place more than fifty (50) feet ahead of the block setters. The ramming and filling of the joints shall follow closely the block setting, but no ramming shall be done within less than six (6) feet of the face of the block setting; and the final joint filling shall be kept completed to within twenty-five (25) feet of the ramming; except that all the work rammed during any day shall have the joint filling completed before the cessation of work on that day. The street shall not be opened to travel until the grout has thoroughly set.
77. Fitting Paving Around Other Structures.—The size of blocks and the width of courses shall, as the block laying approaches bridge stones, curbs and other structures, or in making closures with other sections of pavement, be so selected and adjusted that joints not over three-quarters (¾) inch in width shall result, without breaking blocks or splitting courses.
78. Street Railroad Tracks.—Where railroad tracks exist in the street the paving blocks shall be laid against the rail in the following manner:
The sub-grade and the pavement foundation shall extend under the rails uninterrupted except by the ties or other structures connected with the railroad track. For a distance of sixteen (16) inches, on each side of the rail, measuring from the center thereof, there shall be spread on the pavement foundation a layer of mortar not less than one and one-half (1½) inches thick, composed of one (1) part of cement and three (3) parts sand, complying with the requirements of Sections 29 and 30. Upon this layer of mortar shall be set, against the rail, and on each side of it, selected paving blocks, securely bedded in the mortar before it shall have begun to set.[38]Alternate blocks shall be long and short so as to break joint with the blocks of the adjoining pavement. Selected blocks with well dressed top surfaces shall be used and their tops shall be set as nearly as practicable at the level of the top of the rail, but not so high that the car wheels will ride upon them. In setting the blocks they shall be firmly bedded into the mortar by the use of paving hammers, but they shall not be thereafter rammed. As the blocks are set, any space between the paving blocks and the web of the rail shall be filled with mortar of the quality described above. Theplacing of these blocks shall not precede by more than ten (10) feet the block laying on the street. Care must be taken not to disturb the bedding of these blocks in the laying of the adjoining pavement, or otherwise. The joints shall be filled with grout as specified in Sect. 75.
The construction along slot-rails shall be the same as described above, except that blocks of special size or shape may be required, as the Engineer may direct.
79. Bridge Stone Crossings.—Where directed by the Engineer, the old bridge stone shall be redressed and relaid, as hereinafter specified for new bridge stone, and shall be moved from the point where taken up to the point where they are to be relaid, by the Contractor at his expense.
New bridge stone shall be of the same quality of granite as the paving blocks and free from imperfections. They shall not be less than three and one-half (3½) nor more than six (6) feet long, eighteen (18) inches wide and of a uniform thickness not less than six (6) nor more than eight (8) inches, but these dimensions may be varied by the Engineer where necessary to fit the stone into special locations.
Their top shall be well dressed to a true plane surface not varying in evenness more than one-quarter (¼) inch. The sides shall be dressed perpendicular to the face so as to joint closely against the paving blocks. The ends shall be cut to lines making an angle of from 60° to 45° with the longitudinal axis of the stones[39]and so dressed and to such a bevel that when set in the curved surface of the street, the joint between adjoining stones shall not be wider than three-eighths (⅜) inch from top to bottom.
Bridge stones shall be set in advance of the block laying, over the concrete street foundation, in a bed of sand or gravel in which they shall be firmly bedded. Their upper surface shall conform truly to the pavement datum. They shall be set accurately to the lines given by the Engineer. Where the crosswalk requires more than one width of bridge stone, the courses shall be laid parallel to, and at such distance from each other as the Engineer may direct, and the space between courses shall be filled with paving blocks laid as specified for other parts of the street.
BRICK PAVEMENT[40]
80. Sub-grade.—The sub-grade for brick pavement shall be prepared in accordance with Sect. 26, and shall be finished to a surface ... inches below and parallel to the pavement datum.
81. Foundation.—The foundation for brick pavement shall be of hydraulic concrete[41]prepared in accordance with Sections 28 to 37 inclusive. Its thickness shall be ... inches and its upper surface shall, when completed, be parallel to and at a depth below the pavement datum equal to the depth of the brick plus one and one-fourth (1¼) inches. The surface of the foundation shall not vary more than one-half (½) inch above or below that depth.
82. Paving Brick.—The linear dimensions of paving brick may vary between the following limits: In length, from eight and one-half (8½) to nine and one-half (9½) inches; in width, from two and one-fourth (2¼) to three and one-half (3½) inches; in depth, from four (4) to four and one-eighth (4⅛) inches; but the length shall not be less than two and one-half (2½) nor more than three and three-fourths (3¾) times the width.[42]The corners shall all be rounded off to a radius of not less than one-eighth (⅛) nor more than three-sixteenths (³⁄₁₆) inch. The brick for any one contract shall be all of the same kind and of the same standard size, and the individual bricks shall not vary in length more than three-sixteenths (³⁄₁₆) inch, nor in width more than one-eighth (⅛) inch from the size adopted as standard. Raised lugs or letters are permissible on one side of each brick but must not project more than three-sixteenths (³⁄₁₆) inch from the general surface.[43]
The brick must be specially manufactured for paving purposes. They may be made from shale or from suitable clay. In either case the material must be thoroughly pulverized, mixed and tempered, and must be free from lime nodules or other substances that may disintegrate the brick when immersed in water. The brick shall be molded in efficient brick machines to a truly rectangular form, free from cracks, flaws and injurious laminations. After being dried the brick shall be properly and uniformly burned in down-draft kilns. Shale brick shall be burned to the point of incipient fusion or vitrification. After the burning is completed, the brick shall be allowed to cool with sufficient slowness to insure thorough annealing.
The completed brick shall be free from flaws, cracks, ragged corners, and from such distortion or warping as will interfere with their utility or good appearance in the pavement. Paving brick shall not be salt-glazed.
83.The brick shall be subjected to the following tests to determine their quality:
When broken by the blows of a hammer the brick shall be strong and tough. The broken surface shall show a homogeneous composition throughout the broken section, free from flaws, injurious laminations, nodules and voids, and shall appear to be uniformly burned from surface to center.
When subjected to the standard “Rattler” test, in accordance with the rules adopted by the National Paving Brick Manufacturers’ Association, the average loss in weight shall not exceed eighteen (18) per cent.[44]and the loss in weight of any individual brick in the test shall not be more than twenty-five (25) per cent. greater than the average loss of the whole charge.
When subjected to the absorption test, in accordance with the rules adopted by the National Paving Brick Manufacturers’ Association, shale bricks shall not absorb more than two (2) per cent. norless than one-half (½) of one per cent. of their weight of water,[45]and clay bricks shall not absorb more than six (6) per cent. of their weight of water; the absorption of any individual brick shall not be more than fifty (50) per cent. greater than the mean absorption of the whole lot tested.[46]Brick that do not successfully pass all these tests will not be accepted.
84. Samples.—Where samples of paving brick have been required and submitted by successful bidders, and tested as described above, it will be assumed that these samples fairly represent the quality of the brick to be subsequently supplied for the work, and brick that do not come up to the standard thus established will not be accepted.
85. Delivering Brick on Street.—Unless the sidewalks are too narrow to permit of it, the brick shall all be delivered upon the street before the foundation is constructed, and neatly piled upon the outer edge of the sidewalks; occasional openings being left in the piles for the accommodation of foot passengers. One-half the brick required shall be thus delivered and piled upon each sidewalk. In delivering the bricks from these piles to the bricklayers, they must be carried on pallets, or other suitable devices must be used to prevent mutilation by rough handling; they must not be dumped from wheelbarrows upon freshly-laid brick pavement.
If for any reason the bricks are not delivered before the foundation is laid, or if the sidewalks are too narrow to permit of the brick being stored upon them, they may be delivered over the foundation, but not until the concrete has set so hard that it will not be injured by transportation over it.
86. Sand Cushion.—Directly before the brick are laid into the pavement there shall be spread over the foundation a layer of sand one and one-half (1½) inches in depth. The sand shall be free from vegetable or other refuse matter, and shall not contain more than five (5) per cent. of clay and loam. Pebbles and fragments of stone exceeding one-fourth inch in diameter must be screened out. When spread on the street the sand shall be sufficiently dry to permit of proper gaging by templates, as hereinafter described. The sand shall be spread and correctly gaged to the proper thickness and surface by the use of templates formed to the true designedcross-sectional contour of the pavement. If the width of the street between curbs does not exceed twenty-five (25) feet, the template shall be made in one length sufficient to cover the full width of the street, and its ends shall be so constructed and fitted with iron rollers, that it will rest upon and roll along the top of the curb at each end; if the width of the street between curbs be not more than fifty (50) feet, the template shall be of sufficient length to reach from the curb to the middle of the street, and constructed to move on rollers on top of the curb at one end and upon a plank six (6) inches wide and one and one-half (1½) inches thick laid upon the foundation along the center line of the pavement. The template shall be worked forward and backward along the line of the street until the surface of the sand conforms exactly to the designed contour of the pavement, at a depth below the pavement datum equal to the depth of the paving brick minus one-fourth (¼) inch. The whole surface shall then be rolled with a garden roller not less than thirty-six inches long and not less than thirty inches in diameter, weighing not less than three hundred pounds. When completed the surface of the sand cushion shall be smooth and unbroken, and care must be taken not to disturb it before the bricks are set upon it.
87. Setting the Brick.—Several courses of brick, aggregating a strip having a width of not less than twelve (12) inches nor more than fifteen (15) inches on each side of the street, beginning against the curb, shall be first laid; the brick being set with their long dimension parallel to the curb.[47]The pavement intervening between these gutter courses will then be set in courses at right angles to the axis of the street, except in street intersections, where the courses shall make an angle of forty-five (45) degrees with the axis of the street. The brick shall be set upon edge on the sand cushion with their top faces parallel to the pavement datum, in straight courses, continuous across the street, the long dimension of the brick being parallel to the courses; they shall be set as closely together as possible, so that the joints both between the courses and between individual bricks shall not exceed one-eighth (⅛) inch, where the bricks are without lugs, and not more than one-fourth inch where the brick have lugs. Broken bricks and bats shall not be used except as closers at the ends of the course and in fitting the pavement around manholes, etc., and nothing smaller than half-bricks shall be used in either case, and the broken ends must be shaped to make reasonablyclose joints. Filling up with bats must follow the brick-laying closely. Brick with lugs shall be laid with the lugs all in one direction.
88. Inspection.—After the bricks are laid the pavement will be inspected by the Engineer, or his agent. He may require that the surface shall be previously wetted by sprinklers, or by a sprinkling nozzle, in order to detect soft or porous bricks.[48]Defective bricks indicated by him shall be removed and replaced by acceptable brick.
89. Rolling and Ramming.—The surface of the pavement shall then be rolled and rammed in the following manner:
The roller used shall be of the asphalt roller style, driven by steam and weighing not less than three and one-half (3½) nor more than five (5) tons. The rolling shall begin as near the curb as practicable, the roller being operated slowly, parallel to the axis of the street, and working outwardly until the center of the street is reached, when the roller will proceed to the opposite side of the street and the operation proceed as before. After this longitudinal rolling is completed the pavement will be continuously rolled a second time, the roller operating back and forth at an angle of forty-five degrees to the axis of the street, and a third time, the roller operating at right angles to the course of the second rolling. After the rolling is thus completed the brick in the gutters not reached by the roller shall be rammed with a street rammer weighing not less than thirty (30) pounds, a plank not less than four (4) feet long, ten (10) to twelve (12) inches wide and two (2) inches thick being interposed between the pavement and the rammer and moved about so that the whole surface of the gutter shall be thoroughly and equally rammed and its surface brought to an even junction with the rolled portion of the work.
When the rolling and ramming is thus completed the surface of the pavement shall conform so truly to the designed pavement datum that it will nowhere depart more than three-sixteenths (³⁄₁₆) inch from properly formed templates and straight-edges applied to its surface.
90. Filling the Joints.[49]—Directly after the completion of the rollingand ramming, the joints between the bricks shall be filled as follows:
The joints in the longitudinal gutter courses, and the joints between six contiguous courses running across the street, from gutter to gutter, in each length of fifty (50) feet of the pavement, shall be filled with bituminous cement composed of coal-tar pitch, commercially known as Number Four, to which has been added twenty (20) per cent. of refined Trinidad asphalt and twenty (20) per cent. of hydraulic cement, all by weight. In preparing this bituminous cement, the pitch shall first be melted and the asphalt, also melted, added and thoroughly incorporated by agitation. The hydraulic cement shall then be added and the whole agitated until a complete and uniform mixture results. The bituminous cement thus prepared shall while sufficiently hot and liquid to flow freely, be poured from a spouted vessel into the joints until they appear to be nearly or quite full. After allowing time for the filling to subside, the joints will be gone over a second time and completely filled.
All the remaining joints in the pavement shall be filled with Portland cement grout, as follows:
The grout will be composed of equal parts by volume of sand (Sect. 30) and Portland cement (Sect. 29), a quick-setting cement being preferred. The sand and cement shall be first thoroughly mixed dry and then enough water added to make a grout of such consistency that it will flow like thick cream, and the mixing continued until a homogeneous mass is produced and until the groutis applied to the pavement. The grout shall be prepared in water-tight boxes of a convenient size. Before applying the grout the pavement shall be thoroughly dampened by sprinkling. The grout shall be spread over the pavement with scoop shovels, in two courses, the first being sufficient to nearly fill the joints, and the second, which shall be applied before the first has begun to set, shall be sufficient to entirely fill the remaining space in the joints. As rapidly as the grout is applied it shall be swept with brooms until it all enters the joints.[50]
91.Travel must be excluded from the pavement until the grout has set firmly; in no case less than five days, and the grout must be kept moist during this period.
92. Sub-grade.—The sub-grade for wood-block pavement shall be prepared as specified in Section 26, and shall be finished to a surface ... inches below the pavement datum.
93. Foundation.—The foundation for wood-block pavement shall be Portland cement concrete ... inches thick, prepared as specified in Sections 28, 29, 30, 31, 32, 33, 34, 35, 36 and 37. The upper surface of the concrete foundation, when completed, shall be at a distance below the pavement datum equal to the depth of the blocks to be laid, plus one-half (½) inch, and must not vary more than one-fourth (¼) inch above or below that depth.
MATERIALS
94. Wood-blocks.—The wood-blocks may be made of Long-leaved yellow pine (Pinus palustrus), Lob-lolly pine (Pinus tæda), Short-leaved pine (Pinus echinata), Cuba pine (Pinus heterophylla), Black gum (Nyssa sylvatica), Red gum (Liquidambar styraciflua), Norway pine (Pinus resinosa), or Tamarack (Larix laricina), or of other species of wood of equal strength and toughness and of a texture permitting as satisfactory preservative treatment as those herein named. But, as far as practicable, only one species of wood shall be used on any one contract.[51]
Only wood from live, sound trees shall be used. The lumber from which the blocks are cut shall be properly manufactured, free from bark, and with full square corners. It shall be free from decay, dottiness, brashness, shakes, large season cracks, loose or unsound knots over three-fourths (¾) inch in diameter, and all other imperfections which may, in the opinion of the Engineer, be detrimental. “Fat” pine containing so much resin that it will not take up the specified quantity of creosote oil in treatment may be rejected. Second-growth timber, and Southern pine showing, outside of a radius of three (3) inches from the heart, nine (9) or less annual growth rings to the inch, will not be accepted.
The paving blocks made from the lumber hereinbefore specified shall be well manufactured and truly rectangular and square edged. Their depth (parallel to the fiber) shall be ... inches,[52]their length shall not be less than six inches nor more than three times their depth, and their width shall be from two and one-half (2½) to three and one-half (3½) inches, but at least one-fourth inch less than their depth.
All the blocks for any one contract shall be of the same standard depth and width, and the individual blocks shall not vary more than one-eighth inch from the designated depth and width.
95. Creosote Oil.[53]—The oil used for the preservative treatment of the paving blocks shall be coal-tar creosote oil, commonly known as dead oil of coal-tar, without admixture or adulteration with other oils or tars. Oils produced or resulting from the distillation of water-gas tar, blast-furnace tar, producer-tar, lignite-tar, petroleum-oil tar, or wood-tar, or, containing an admixture of any of these will not be accepted. The creosote oil shall not contain more than five per cent. (5%) of tarry matter nor more than two per cent. (2%) of water. Its specific gravity at a temperature of 100° F. shall be not below 1.03 nor above 1.08. Not less than ninety-nine per cent. (99%) shall be soluble in hot benzol. It shall not contain more than eight per cent. (8%) of tar acids. When two hundred (200) grams are subjected to distillation at gradually increasing temperatures, not more than five per cent. (5%) of distillate shall distil over up to a temperature of four hundred degrees F. (400° F.), nor more than thirty-five per cent. (35%) shall distil over up to a temperature of four hundred and fifty-five degrees F. (455° F.), and not more than eighty per cent. (80%) shall distil over up to a temperature of six hundred degrees F. (600° F.). After complete distillation there shall not remain more than two per cent. of coke. The residue remaining, upon sulphonating a portion of the total distillate, shall not exceed one per cent. (1%). The above tests shall be made in accordance with the methods prescribed in the “Report of the Committee on Preservative Treatment of Poles and Cross-arms” of the National Electric Light Association, 1911.
96. Preservative Treatment.—The paving blocks shall, afterthey are cut to the proper dimensions, be subjected to preservative treatment with the creosote oil specified in Section 95.
The contractor may employ any of the standard methods in common use for impregnating the blocks, provided that uniform results are attained, complying with the following requirements:
The wood shall not be heated during any part of the process to a temperature exceeding two hundred and sixty degrees Fahrenheit (260° F.).
All parts of every block shall be reached and penetrated by the oil. The quantity of oil found in the blocks after treatment shall average not less than ... pounds per cubic foot of wood.
The oil in the treating tanks during the process of impregnation shall not become diluted with water to the extent of more than five per cent. (5%) and if the percentage of water in the oil during the process of treatment shall exceed two per cent. (2%) the quantity of the oil to be injected in the wood as stipulated hereinbefore shall be increased in a like ratio; for example, if the oil in the treating tanks shall be found to contain four per cent. (4%) of water the quantity required to be found in the blocks after treatment shall be four per cent. (4%) greater than herein specified.
The quantity of oil injected shall be determined primarily by tank measurements, but shall be verified by actual determination of the quantity of oil in the treated blocks by the following method: representative treated sample blocks shall be selected and an auger hole one inch in diameter bored entirely through the block parallel to the fiber, the borings all collected, thoroughly mixed, and the quantity and ratio of oil to wood in the borings determined by extracting the oil completely with carbon di-sulphide. The center of the auger hole shall be located midway between the sides of the block and at a distance from the end of the block equal to one-third (⅓) of the length of the block. At the time of treatment the blocks shall not be green or saturated with water, but they shall, preferably, not be thoroughly seasoned. After treatment, and until used, the blocks shall, during dry weather, be frequently well drenched with water to prevent excessive drying out and cracking.
97. Laying the Wood-Blocks.—The concrete foundation shall be cleaned and swept to remove all dirt and débris and shall be thoroughly dampened immediately in advance of the setting of the blocks. Upon the concrete foundation shall be spread a layer of mortar about one-half inch thick, made of one part Portland cement and two parts sand with sufficient water to make a moderately stiffpaste.[54]The mortar shall be thoroughly mixed and shall be spread in place over the concrete foundation immediately in advance of setting the blocks to such a thickness that when the blocks are set and properly tamped their tops shall conform accurately to the pavement datum.
Upon this mortar bed the blocks shall be set with their fiber vertical, in straight, parallel courses at right angles to the axis of the street, except at street intersections where they shall be set at an angle of forty-five degrees with the axis of the street. The blocks shall be set as close together as practicable. Blocks in adjoining courses shall break joint at least three inches. Blocks of such lengths shall be selected as to make as little splitting as practicable in filling out ends of courses. Where splitting is necessary, no fractional block shall be used whose length is not at least equal to its width.
After the blocks are thus set the whole surface of the pavement shall be rammed with a rammer weighing not less than twenty pounds, a plank ten (10) inches wide, two (2) inches thick and four feet long being interposed between the rammer and the pavement and moved about as the ramming progresses until the blocks are forced into a firm seat in the mortar bed and their tops brought accurately to the pavement datum. The ramming shall be completed before the mortar under them has begun to set, but no ramming shall be done, during the progress of the work, nearer than three feet to the edge of the block setting, except where the block setting may be suspended, as at the end of the day’s work, when all the blocks then set shall be rammed.
The top surface of the pavement when completed shall conform so truly to the pavement datum that correctly formed templates twelve (12) feet long applied to the surface shall show at no place a departure of more than three-sixteenths (³⁄₁₆) inch therefrom.
98. Filling the Joints.—After the block setting is completed, perfectly dry, fine sand shall be spread over the pavement surface and swept about until every joint into which the sand will penetrate shall be completely filled. The remaining sand shall be left upon the pavement for such time as the Engineer may direct, when it shall be removed by the Contractor.[55]
99. Inspection.—The lumber for paving blocks will be inspected before it is cut into blocks. The blocks will also be inspected upon delivery to the street and as they are laid. Blocks that have, in treatment or subsequent handling, developed open season cracks or wind shakes or other imperfections that may prevent their durability or usefulness in the pavement shall be rejected and removed from the street.
100. Chamfered Blocks.—Where wood-block pavement is laid on streets or parts of streets having a gradient of more than 3%, the blocks shall not be less than four (4) inches long, and the upper side-corners of the blocks shall be chamfered to a depth of three-eighths (⅜) inch, the chamfered surface to make an angle of 40 degrees with the vertical sides of the blocks; or such other construction shall be used as will, in the opinion of the Engineer, provide an equally good foot-hold for horses.
101. Expansion Joints.—Before the blocks are set there shall be placed along and against each curb a board of trapezoidal section having a width one inch greater than the depth of the blocks, the upper edge of which shall have a thickness of three-eighths (⅜) inch for each ten feet or fraction thereof of the width of the street between curbs, and a bottom width one-fourth (¼) inch less than the top. The paving blocks at the beginning and end of each course shall be set against this board. After the ramming of the blocks has been completed, these boards shall be carefullywithdrawn and the space between the curbs and the paving blocks shall be completely filled with the bituminous paving cement described in Section 90.
102.The street shall not be opened to travel until such time as the mortar under the blocks shall have become well set, nor until the Engineer shall so direct.
Note.—The phrase, Bituminous Concrete Pavement, has been applied to a large variety of roadway surfaces differing materially from each other in composition, construction and utility. Some of these are covered by United States patents, the scope and limitations of which are not yet fully determined or understood. The necessity of avoiding infringement of these patents has to be kept in mind in framing specifications for public use, and this consideration does not permit the presentation here of specifications which, in the opinion of the author, would secure an ideal pavement of this general character.
Bituminous concrete pavements constructed in substantial conformity with these specifications have been laid on a number of city and town streets and country roads and have proved satisfactory and fairly durable in use. It is believed that they do not infringe any existing patents.
Our rather limited experience with pavements of this character seems to indicate that if good materials are used and the work properly done, they are suitable for use on city streets of light travel, and on suburban streets and country roads carrying an amount of travel considered heavy for these classes of roadways. Where the results have been unsatisfactory, the cause can generally be traced to unsuitable materials or unskillful construction, the result of ignorance or carelessness on the one hand, or of the attempt to reduce first cost below normal figures on the other. Many people are searching for a pavement or roadway that will have all the good qualities of the standard pavements but can be built about as cheaply as a common macadam road. It is possible that something of the kind may be discovered; but in the present state of the art it is chimerical. High quality and low first cost do not go together in street paving. The question to be considered is, rather, how can we invest a dollar in street or road building so that it will, in the long run, yield the best return upon the investment. The pavement provided for in these specifications is not a cheap pavement, but where it is suitable for the conditions to be met, it will be well worth its cost.
SPECIFICATIONS
103. Sub-grade.—The sub-grade except where old pavement is utilized for foundation shall be prepared in accordance with Section 26 of these general specifications.
104. Foundation.[56]—The foundation for bituminous concrete pavement shall be a properly prepared old pavement, or hydraulic concrete, or compressed broken stone, as determined by the engineer.
105.Old macadam pavement or road to be utilized for foundation, shall be prepared in the following manner:
All high places or humps shall be dressed down to a plane two (2) inches below the pavement datum, the work being done with care so as to disturb as little as possible the macadam that is to remain. Depressions in the old macadam shall be carefully cleaned out so as to remove all earth and other débris and loose material, and filled with hydraulic concrete. Newly dug or filled trenches and holes extending through the macadam shall be excavated and cleaned out so as to admit the use of at least four (4) inches of hydraulic concrete. The hydraulic concrete for thus leveling up the roadway shall be composed of one (1) part of approved Portland cement, four (4) parts of clean sand and nine (9) parts of sound, hard crushed stone, well mixed into a wet concrete. After placing, the concrete shall be well tamped so as to form a compact body, conforming to a plane two (2) inches below the pavement datum. The concrete shall be protected from travel and allowed to become well set before the surface of bituminous concrete is applied.
106.Old stone block or brick pavement may be utilized for foundation, provided that the blocks or bricks do not require tobe taken up and reset, or, if so taken up and reset, that the joints shall be completely filled with grout composed of one (1) part Portland cement and two (2) parts of good sand. Depressions, trenches and holes shall be treated as specified in Section 105.
107.Hydraulic concrete foundation shall be constructed in compliance with the requirements of Sections 28, 29, 30, 31, 32, 33, 34, 35, 36 and 37 of these specifications. Its depth or thickness shall be ... inches.
108.Broken stone foundation shall be ... inches in thickness after completion. It shall be constructed in accordance with Section 40 of these specifications.[57]
109.When completed the upper surface of the foundation shall nowhere be more than two and one-half (2½) inches nor less than one and three-fourths (1¾) inches below the pavement datum. No travel shall be permitted upon the foundation until the bituminous concrete shall have been laid.
110. Bituminous Concrete.—The bituminous concrete shall be composed of crushed stone, sand, pulverized stone, and asphaltic cement.
A typical composition for the bituminous concrete, to be as closely approximated as practicable, is as follows, the percentages being by weight:
The crushed stone shall be trap rock, granite, or hard, sound, durable limestone. It shall be crushed to such sizes that all will pass through a screen with two meshes to the linear inch and shall be of such assorted sizes of fragments as will, when incorporated with the sand, pulverized stone, and bitumen, produce a mixture substantially conforming to the percentages of each named in the preceding paragraph.
The stone shall be freshly crushed, clean and free from clay, loam, organic matter and refuse of every kind.
The sand shall be silicious, and free from clay, loam and refuse of all kinds. The grains shall be of such sizes that approximately twenty-five per cent. (25%) of the whole will pass the number eighty (80) sieve, fifty-eight per cent. (58%) shall pass the No. 40 sieve and not more than seventeen per cent. (17%) will pass the number 10 sieve, when used in the order named. The pulverized stone shall conform to the requirements of Sect. 49. Portland Cement may be substituted for not more than twenty per cent. (20%) of the pulverized stone if the Engineer so directs, in which case the Portland Cement actually so used shall be paid for extra at the prevailing market price, to be agreed upon in advance. The asphaltic cement shall comply with the requirements of Sects. 43, 44, 45, 46, 47, and 50, except that it may have a somewhat higher penetration, as may be determined by the Engineer.[58]
111. Mixing.—The materials composing the concrete shall all (except the pulverized stone and Portland cement) be uniformly heated to a temperature not exceeding three hundred and fifty degrees Fahrenheit (350° F.) and not below three hundred degrees Fahrenheit (300° F.), and while at such temperature shall be incorporated and mixed in a mechanical mixer. The stone, sand, and pulverized stone shall be placed in the mixer in the order named and well mixed together, after which the asphaltic cement shall be added and the mixing continued until each fragment is thoroughly coated with cement.
112. Laying on the Street.—The mixed concrete shall be taken to the street as soon as practicable after leaving the mixer. It shall be unloaded on the street, properly spread and truly graded with asphalt rakes to such a depth that after compression by rolling it will have a thickness of not less than two inches. The concrete when unloaded on the street shall be at a temperature not below two hundred and eighty degrees Fahrenheit (280° F.). In spreading and grading, all material must be moved from the pile into which it was unloaded. As soon as practicable after the concrete shall be graded, the surface shall be thoroughly rolled with a ten-ton asphalt roller and the rolling continued until the roller makes no further impression on the concrete surface. When completed the surface must conform closely to the pavement datum so that there will be no depressions or elevations exceeding one-fourth inch above or below the pavement datum.
113.The sub-foundation for hydraulic concrete pavement shall be prepared as specified in Section 26.
114.The pavement shall be constructed in two courses called the bottom course and the top course, as hereinafter specified.[60]
115. Bottom Course.—The bottom course shall be four (4) inches in thickness[61]and shall be composed of the materials specified in Sects. 29, 30, and 31. The concrete shall be composed of one part Portland cement, three parts sand and six parts of broken stone, and shall be mixed and placed as specified in Sects. 35 and 36, but its top surface when properly compacted shall be parallel to and not less than two (2) nor more than two and one-half (2½) inches below the pavement datum.
116. Top or Surface Course.—The top course shall be composed of the Portland cement specified in Sect. 29, the sand specified in Sect. 30 except that it shall be especially clean, and the grains shall be of such size that at least seventy-five per cent. (75%) of the mass will fail to pass a screen having thirty (30) meshes to thelinear inch, and shall be of superior quality for making concrete; and of crushed Trap Rock,[62]or of stone equally hard, strong and durable.
The trap rock shall be crushed to such sizes that all will pass through a screen having meshes one and one-fourth (1¼) inch square and that none will pass through a screen having meshes one-half (½) inch square,[63]and it shall be free from clay, refuse or other foreign substances.
117.The surface-course concrete shall be composed of one part Portland cement complying with Sect. 29, one and three-quarters (1¾) parts of sand, and, generally, three and one-half (3½) parts of crushed stone, but the ratio of crushed stone shall be such that in the completed concrete the volume of mortar in the compressed mass shall exceed by about fifteen per cent. (15%) the voids in the stone.[64]The cement and sand shall be thoroughly mixed together dry, enough clean water then added to make a rather wet mortar and the mixing continued until the materials are thoroughly incorporated into a homogeneous mass. The crushed stone shall then be added, and the mixing continued until every fragment of stone is completely covered with mortar. Sufficient water shall be added during the mixing, if necessary, to make a “wet” concrete, but not so wet that free water will flow from the mixed mass. In handling and adding the stone to the mortar care must be taken to prevent the stone segregating into masses of different sizes. The concrete for the top course shall be madewith special care and thorough work, the intention being to secure a superior quality of concrete.[65]
118.The concrete thus prepared shall be placed upon the bottom course before the latter has begun to set[66]and carefully graded so that when properly compacted its top surface will coincide with the pavement datum. The concrete will then be well rammed by rammers having a face of 6 by 6 inches and weighing not less than twenty (20) pounds after which the surface will be completed by rolling with a power roller of the asphalt type weighing not less than five (5) tons.[67]All these operations must be completed before any of the concrete in either course shall have begun to set. The surface shall not be plastered with neat mortar nor shall it be trowelled.
119.The completed surface must coincide with the pavement datum to the extent that a properly formed template when applied to the surface shall show no departure from the pavement datum exceeding three-sixteenths (³⁄₁₆) inch.
120.After the laying of the pavement has been completed it shall be allowed to stand until the concrete of both courses shall be fully set, which period shall be not less than ten (10) days, or longer, if conditions make a longer time necessary, as the engineer may direct, of which he shall be the sole judge. During this period the concrete shall be kept in a moist condition throughout, by sprinkling with hose or otherwise. No travel shall be allowed upon the street until the engineer shall open it for public use. The concrete shall not be laid during rain storms or when the thermometer is below forty-five (45) degrees F., and in case there may be danger from frost the whole surface of the concrete shall be covered by straw or hay. Manure must not be used for this purpose.
121. Expansion Joints.[68]—An expansion joint along the curbing on each side of the street shall be provided in accordance with Sect. 101.Expansion joints shall also be provided and constructed as follows: Wherever the width of the pavement exceeds twenty (20) feet between curbs there shall be a expansion joint along the longitudinal center of the street; expansion joints shall also be made, at right angles to the street and extending continuously from curb to curb, at distances apart not exceeding twenty (20) feet. These expansion joints in the body of the pavement shall be made by cutting entirely through both courses of concrete along a straight line, using a special straight-edged cutter not more than three-sixteenths (³⁄₁₆) inch thick, when the concrete is laid in hot weather and not more than three-eighths (⅜) inch thick if the concrete is laid when the thermometer is below sixty (60) degrees F. The cutting of the expansion joints shall be carefully and skillfully done, and after each joint is cut a special T-shaped smoother, the stem of which is one inch deep and of the same thickness as the cutter shall be worked back and forth in the joint until the edge of the concrete adjoining the joint shall be well and smoothly compacted. The smoother shall be so formed as to round off the corners of the concrete to a circular form having a radius of one-fourth (¼) inch. All these operations shall be completed before the concrete has begun to set. After the concrete has set and before the street is opened to travel all expansion joints shall be poured full of bituminous cement, as specified in Section 90.[69]
122. Bituminous Coating.[70]—After the concrete shall have become fully set as determined by the engineer and before the street isopened to travel the whole surface of the pavement shall be covered by a finishing coat of bituminous road oil as hereinafter specified.
The road oil shall be prepared from native asphalt or from a crude oil having an asphaltic base. Not less than 95 per cent. of the oil shall be soluble in cold carbon di-sulphide, and it shall contain not less than thirty (30) per cent. of solid asphalt, nor more than ten per cent. of fixed carbon. It shall be of such consistency as to flow freely at a temperature of seventy-five degrees (75°) F. The oil shall not be applied except when the road surface is perfectly dry and when the temperature of the air is not below 60° F.
The oil shall be evenly distributed over the whole surface of the street at the rate of one-half (½) gallon of oil per square yard of surface, and well worked over the surface with squeegees or other suitable devices.
Not less than twenty-four hours after the application of the oil the surface of the pavement shall be evenly covered to a depth of one-fourth inch with clean, dry stone screenings or coarse sand, after which the street may be opened to travel.
123.Contractors or promoters submitting proposals for the construction of new, experimental, or special street pavements, the merits of which have not been established by experience in the city of ..., must submit with their proposal a full and complete set of specifications for the construction of the pavement. If contract shall be awarded under said proposal, said specifications will be made a part of the contract entered into. The Engineer will enforce compliance with these specifications, as the construction work proceeds, without assuming or incurring any responsibility for the character, quality, serviceability or durability of the resulting pavement. But the Contractor shall be subject to and shall comply with the requirements and stipulations of Sects. 1 to 25, inclusive, of these specifications.
124. Special Guaranty.[72]—Inasmuch as the pavement to be constructedunder the special specifications submitted by the Contractor is more or less of an experimental character, having not been heretofore used in the city of ... to an extent sufficient to establish its value, the Contractor shall be held wholly responsible for the utility, serviceability and durability of the pavement so constructed; and he shall enter into a guaranty to the effect as follows:
That the pavement will fulfill all the usual and legitimate requirements of a satisfactory roadway pavement upon the street upon which it is to be laid.
That the pavement will successfully serve and endure the travel to which the street may be subjected for a period of ... years next following the date of the certificate of its completion and acceptance, and shall be in good condition at the end of that period, ordinary and reasonable wear and tear, and accidental or other injuries not due to defects in the pavement itself, excepted.
That the Contractor will, at his own cost, keep the said pavement in satisfactory repair during said period of ... years, and will leave it in a condition of satisfactory repair at the end of that period.
That the Engineer, or his successor or successors in office, shall be the sole and final judge as to whether the conditions of this guaranty shall be, or shall have been complied with.
That in case the pavement shall not, in the judgment of the Engineer, fulfill the terms and conditions of this guaranty at any time during said period of ... years, or upon its expiration; or in case the Contractor shall fail to make all or any of the repairs that may in the judgment of the Engineer be or become necessary during said period of ... years, within a reasonable period to be determined by the Engineer, but not to be less than twenty (20) days after notice to make such repairs has been given him by the Engineer, he (the Engineer) may proceed to make or to have made such repairs, or to repave the street, in any manner that he may deem necessary or advisable, and to charge the cost of such repairs or repavement to the Contractor, provided, that the sum or sums so charged against the Contractor shall not, in the aggregate, be more than the amount paid to the Contractor for the construction of the pavement.
125. Bond.—The Contractor shall give bond with sureties satisfactory to the Engineer in a sum not less than the estimated cost of the pavement at the contract prices, the term of the bond to extendover the entire period of ... years, for which the pavement is guaranteed.
126.During the said period of ... years the Contractor shall, upon being notified by the Engineer so to do, make any repairs to the pavement that may become necessary by reason of cutting into it for the purpose of constructing or repairing pipes, conduits or other underground structures, or street railroad tracks, or by reason of accidental or unusual causes, or of any causes other than those due, in the opinion of the Engineer, to the failure of the pavement to meet and fulfill the terms of the guaranty stipulated in Section 124. And for making such repairs the Contractor shall be paid the price of ... per square yard for the repairs actually so made. Repairs so made shall be subject to the terms of the guaranty, stipulated in Section 124, until the expiration of the said term of ... years after the date of the original certificate of completion and acceptance. In case the Contractor shall neglect or fail to make such repairs within a period of twenty (20) days after he shall have received notice to do so, the Engineer may proceed to make or to have made such repairs, and he shall charge to and collect from the Contractor the cost of the repairs so made.
127.Hydraulic concrete combined curb and gutter shall be constructed in accordance with general plan No. ... attached to and made a part of these specifications, but the rise from the gutter to the top of the curb may be varied so as to facilitate drainage.[74]
128. Excavation.—All excavation required for the curb and gutter shall be completed and trimmed to the proper lines as shown by the drawing. The drainage trench under the curb and gutter shown on the drawing shall have the top width and general form shown in the drawing but its depth may be varied to secure proper drainage, as the engineer may direct, provided that its depth below the base of the concrete shall not be less than nine inches nor more than two feet.
129. Broken Stone Drainage.[75]—After the excavation shall have been completed the trench shall be filled up to the level of the base of the concrete with sound, durable broken stone, or coarse gravel, from which the small fragments shall have been removed by screening over a wire screen having openings not less than one inch square. The stone or gravel shall be thoroughly tamped in the trench in layers not more than six (6) inches thick by the use of rammers weighing not less than thirty (30) pounds and having a face area not exceeding thirty-six (36) square inches, and its completed top surface shall conform truly to the designed base of the concrete. These drains shall be connected at suitable intervals with sewers, drains or other outlets to keep them free from standing water. The trench filling shall be completed at least twenty-five feet in advance of placing the forms for the concrete.
130. Concrete.[76]—The concrete shall be made of one (1) partPortland cement, one and three-fourths (1¾) parts of sand and three (3) parts of crushed stone or clean gravel. The Portland cement shall comply in all respects with the requirements of Section 29 of these specifications.
The sand shall be clean, sharp silicious sand made up of grains of such size that not more than fifteen per cent. (15%) will pass a number thirty (30) sieve. It shall not contain more than five per cent. (5%) of clay or loam nor more than two per cent. (2%) of organic matter or other refuse. The stone shall be sound, hard, durable, and freshly broken, free from clay, loam, organic matter, or other impurities. Trap rock or granite will be preferred, but limestone, if hard and sound, may be used with the approval of the engineer. Only those fragments of the crushed stone that pass a screen with openings three-fourths inch square and those that are held on a screen with openings one-fourth inch square shall be used in the concrete.
131. Mixing and Placing Concrete.—The concrete shall be mixed in accordance with Section 35 of these specifications. Very thorough mixing will be required.
The mixed concrete shall be handled so as to prevent as far as practicable any separation or segregation of the stone and mortar. When in place it shall be compacted by tamping and where placed against forms, forking or other effective means must be used to bring mortar to the surface and to secure complete contact between mortar and forms, so as to leave a solid, homogeneous and unbroken surface when the forms are removed. Where the concrete may not be laid against forms, all exposed surfaces must be troweled to a true surface conforming accurately to the lines shown by the plans, templates and straight-edges being used where necessary.
132. Weather.—Concrete in combined curb and gutter shall not be laid in freezing weather nor shall frozen materials be used in the work. Completed work must be securely protected from frost for at least seven days after it is laid. Any concrete curb and gutter that may become frozen within that period shall be wholly removed and replaced with new work.
133. Expansion Joints.—The combined curb and gutter shall be divided into blocks or panels not more than twelve feet long, by clear, open expansion joints perpendicular to the face of the curb,extending entirely and continuously through the whole mass of the concrete. These expansion joints shall be three-eighths inches wide and may be formed either by cutting through the completed curb and gutter with a suitable tool, or by the use of iron forms or partitions, but in either case the corners at the ends of the blocks must be made solid and dense and troweled with a suitable tool.
134. Circular Corners.—At the intersections of streets, circular corners, having a radius equal, generally, to one-fifth of the width of the roadway of the narrower street, shall be constructed of the same dimensions and quality as on the body of the street, and the curb and gutter will be extended along the line of the cross street back to the front lot-lines. Properly curved circular curb and gutter shall also be constructed at all angles exceeding five degrees in the line of the curbing.
135. Corner Protection.—Galvanized steel corner protectors or nose-pieces shall be used to protect the upper and outer corner of the curb at all circular corners and angles in the street. This steel protection may be of any pattern or section procurable in the market and approved by the engineer. It shall be firmly anchored and secured into the concrete.
136. Finishing.—After the forms have been removed and before the concrete has set up too hard to be affected by the brush, the face and top of the curb shall be lightly scrubbed by a suitable wire brush so as to completely remove any glazed surface and to produce a surface of uniform texture and appearance. Dry cement or neat cement mortar shall not be used for dressing up exposed surfaces.[77]
137. Forms.—The forms used may be of dressed lumber or of metal as the contractor may prefer. But they shall have sufficient strength and rigidity to hold the concrete firmly in place, and to preserve the correct dimensions, alignment and levels of the curb and gutter.
138. Protection.—The completed curb and gutter shall be protected from fracture, deformation or spalling until the concrete has fully set. The concrete must be kept moist for at least five daysafter it has been laid. Any part of the curb and gutter that shall have become injured before it is accepted or the street is opened for travel shall be taken up and replaced by the contractor.
139. Payment.—Concrete combined curb and gutter will be paid for by the linear foot in place, the measurement to be made along the upper and outer corner of the curb. The price per linear foot named in the contract will cover all the excavation or grading required and all the materials and labor, including all necessary forms, for constructing the curb and gutter complete. But the crushed stone used for drainage will be paid for by the cubic yard measured in place, and steel corner protection will be paid for by the linear foot in place, at the prices named in the contract.