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. nor less 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 designed cross-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.