SPECIFICATIONS FOR PAVING, ETC. • The following specifications regarding brick street paving represent the standard practice adopted by the Board of Local Improvements of the City of Chicago, Illinois: Cement. In making the concrete, Portland cement shall pass same specifications as for cement used in curb and gutter work.
Sand. The sand used in making the concrete shall be clean, dry, free from dust, loam, and dirt, of sizes ranging froin 1/, inch down to the finest, and in such proportion that the voids as determined by saturation shall not exceed 33 per cent of the entire volume; and it shall weigh not less than 100 pounds per cubic foot. No wind-drifted sand shall be used.
The sand when delivered on the street shall be deposited on flooring, and kept clean until used.
Crushed Stone. The crushed stone used in making the concrete shall be of the best quality of limestone, clean, free from dirt, broken so as to measure not more than 2 inches, and not km than 1 inch, in any dimension.
The stone when delivered on the street shall be deposited on flooring, and kept clean until used.
Mixing and Laying of Concrete. The concrete shall be mixed on movable, tight, iron platforms of such size as shall accommodate the manipulations hereinafter specified.
The cement, sand, and stone shall be mixed in the following proportions: One (1) part of cement, three (3) parts of sand, and seven (7) parts of crushed stone. The sand and cement shall be thoroughly mixed, dry, to which sufficient water shall be added, and then made into a stiff mortar. The crushed stone shall then be immediately incorporated in the mortar, and the mass thoroughly mixed, adding water from time to time as the mixing progresses, until each particle of stone is covered with mortar.
The concrete shall be removed from the platform with shovels, and deposited in a layer on the roadway in such quantities that after being rammed in place it shall be of the required thickness; and the upper surface shall be true and smooth, and - inches below and parallel with the top of the finished pavement.
During the progress of the work, the subgrade must be kept moist.
The concrete shall be sprinkled so as to prevent checking in hot weather, and shall be protected from injury at all times; and shall lie at least seven days before being covered with the wearing surface, or a longer time if deemed necessary.
Sand Cushion. Upon the concrete foundation, shall be spread a layer of sand in such quantity as to insure, when compacted, a uniform thickness of 1 inch.
In surfacing said layer of sand, the Contractor or contractors shall use such guides and templets as the Engineer may direct.
Wearing Surface. Upon the layer of sand as above specified, shall be placed the brick, of such quality and in such manner as hereinafter specified.
Quality of Bricks. The brick to be used shall he of the best quality of vitrified paving brick. Salt-glazed bricks will not be received.
The dimensions of the brick used shall be the same throughout the entire work in any particular case,. and shall be not less than 8 inches in length, 4 inches in depth, and inches in thickness, with rounded edges to a radius of of an inch.
Said brick shall be of a kind known as vitrified paving brick, and shall be repressed to the extent that the maximum amount of material is forced into them. They shall be free from lime and other impurities; shall be as nearly uniform in every respect as possible; shall be burned so as to secure the maximum hardness, so annealed as to reach the ultimate degree of toughness, and thoroughly vitrified so as to make a homogeneous mass.
The bricks shall be free from all laminations caused by the process of manufacture, and free from fire-cracks or cheeks of more than superficial character or extent.
Any firm, person, or corporation bidding for the work to be done, shall furnish specimen brick, which shall be submitted to a waterabsorption test ; and if such brick show a water absorption exceeding 3 per cent of their weight when dry, the bid of the person, firm, or corporation so famishing the same shall be rejected. Such water-absorption test shall be made by the Board of Local Improvements of the City of Chicago, in the following manner, to wit: Not less than 3 bricks shall be broken across, thoroughly dried, and then immersed in water for 72 hours. The absorption shall then be determined by the difference between the weight dry and the weight at the expiration of said 72 hours.