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.
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 exceed one-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.