ASPHALT BLOCK PAVEMENT
60. Sub-grade.—The sub-grade for asphalt block pavement shall be prepared as specified in Sect. 26 of these specifications.
61. Foundation.—The foundation for asphalt block pavement shall be hydraulic concrete or broken stone.[[26]]
Concrete foundation shall be constructed in accordance with Sections 28 to 37 inclusive of these specifications and shall have a thickness of ... inches.
Broken stone foundation shall be constructed in accordance with Section 40 of these specifications and shall have a thickness, when completed of ... inches.
62. Asphalt Blocks.—Asphalt blocks shall be not less than ten (10) inches nor more than twelve (12) inches long, not less than four (4) nor more than six (6) inches wide and not less than two (2) inches nor more than four (4) inches thick. Blocks for the same street must be of the same standard size throughout and individual blocks shall not vary in any dimension more than three-sixteenths (³⁄₁₆) inch from the standard size. Blocks that are chipped, cracked or are otherwise defective shall be rejected.
63. Material and Composition.—Asphalt paving blocks shall be composed of crushed trap rock[[27]] or equally hard and durable rock, sand, pulverized stone and asphaltic cement.
The crushed rock shall be of such sizes that all will pass a screen having circular openings one-third (⅓) inch in diameter and that all will fail to pass a number ten (No. 10) sieve. The stone shall be freshly crushed, free from foreign substances and clean and bright.
The sand shall be clean and sharp and of such sizes that all will pass the number ten sieve and not more than five per cent. will pass the number two hundred sieve. The grain-size of the sand shall preferably be such that at least fifty per cent. (50%) of it will pass the number eighty sieve. The screenings from the crushed stone passing the number ten sieve may be used in place of sand, or thoroughly mixed with the sand to produce a mass of the above composition. The pulverized stone shall comply with Section 49 of these specifications. Portland cement shall be used in place of not more than ten per cent. of the whole if directed by the engineer, in which case the Portland cement will be paid for as extra work at the prevailing market price.
The asphaltic cement shall comply with the requirements of Sections 43, 44, 45, 46, 47 and 50 of these specifications.
64. Typical Composition.—A typical composition of the blocks, which must be complied with as nearly as practicable, is as follows; (by weight)
| Bitumen | 7% | |
| Mineral material passing No. | 200 sieve | 13% |
| Mineral material passing No. | 80 sieve | 9% |
| Mineral material passing No. | 40 sieve | 7% |
| Mineral material passing No. | 10 sieve | 28% |
| Mineral material passing No. | 3 sieve | 36% |
| 100% |
65. Manufacture.—The crushed rock, sand and pulverized stone shall be thoroughly mixed together at a temperature not above three hundred and seventy-five degrees Fahrenheit (375° F.) and not below three hundred and twenty-five degrees Fahrenheit (325° F.) and the asphaltic cement, at a like temperature, added and the mixing continued until a perfectly uniform mass is produced, with every fragment of stone completely coated with cement.
The hot mixture will then be compressed in molds under a pressure not less than four thousand (4000) pounds[[28]] per square inch, after which the blocks will be removed from the molds and allowed to cool, either in the air or in water.
The completed blocks after cooling in air shall have a specific gravity of not less than 2.5. They shall not absorb, when immersed in water for twenty-four hours, more than one-half of one per cent. of water. When tested in the standard rattler for testing paving brick the average loss by abrasion shall not exceed twelve per cent. (12%) of their original weight, after 1800 revolutions of the rattler.
66. Laying the Blocks.[[29]]—The foundation shall be first cleaned of dirt, rubbish or loose material.
When the blocks are four (4) inches or less in depth as laid, they shall be set upon a bed of mortar made and applied to the foundation in the following manner:
The mortar shall be composed of Portland cement and sand, in the ratio of one (1) part cement to three (3) parts of sand, thoroughly mixed with sufficient water to make a rather soft mortar. This mortar shall be spread over the foundation, which shall be previously wetted, in a layer approximately one-half (½) inch thick and its top graded by the use of templates to a surface at such depth below, and truly parallel to the pavement datum, that when the blocks are firmly set in it and rammed their tops will be in the true grade and contour of the pavement. The mortar shall be made and spread only as required in the progress of block laying, and any mortar that has begun to set before the blocks are in place and rammed, shall be removed and fresh mortar substituted. The blocks shall be set upon this mortar bed with their longest dimension across the street, in continuous courses which shall be straight and at right angles to the axis of the street. The block layers must stand upon the blocks already laid and not upon the mortar. The blocks and the courses of blocks shall be set as closely together as practicable. Blocks in adjoining courses must break joint not less than four inches. Whole blocks only will be used, except as fillers at the ends of the courses or in fitting the pavement around manholes or other structures, and where thus used the broken ends of the blocks must be dressed to make close joints. Unless otherwise permitted, each course must be laid continuously across the street without interruption in time. As each course is completed the end joints shall be forced close together by the use of wedges, levers or mauls. Upon the completion of every third course, the courses shall be forced together by placing a timber scantling against the face of the last course and striking it with a sledge or maul. When the blocks are thus laid, and before the mortar under them begins to set, they shall be well rammed to a solid bearing in the mortar with a wooden street rammer weighing not less than thirty (30) pounds, a two inch plank ten (10) inches wide and three (3) feet long being interposed between the block and the rammer and moved about so that the whole surface shall be covered and rammed. When the ramming is completed, the top of the blocks must conform so closely to the pavement datum that when a template or straight-edge is placed upon the pavement, its surface shall nowhere depart from the true surface more than three-sixteenths (³⁄₁₆) inch. Blocks, or portions of the pavement found too high or too low, must be taken up and reset in fresh mortar to the true grade. When thus completed to the satisfaction of the Engineer, a layer of one-half (½) inch of fine dry sand shall be placed over the surface and swept about with brooms until all joints are completely filled. The remaining sand shall be removed from the pavement at such time as the Engineer may direct.
When the depth of the blocks exceeds four (4) inches, they may be set upon a cushion course of sand, as prescribed for brick pavement, Section 86, the joints to be filled with sand, as specified above in this Section.
67. Railroad Tracks.—Where railroad tracks exist on the street to be paved, the construction shall be the same as prescribed for granite block pavement, Section 78.
68. The street shall not be opened to travel until the mortar under the blocks shall have become fully set, and in no case under five days after the blocks are laid.