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: