73. Setting the Blocks.—The blocks shall be set in this bed of sand perpendicular to the street surface, with their length at right angles to the street, in courses extending entirely across the street, and at right angles to its axis, except at street intersections where the courses shall be arranged as the Engineer may direct.[[34]] Only stones of the same width shall be set in the same course. The stones in each course, and in adjoining courses, shall be set firmly against each other. The blocks shall be set in the sand bed in such a manner that their bottom surface shall rest evenly upon the sand and that their tops shall be even with each other and to such an elevation that after the pavement is rammed, as hereinafter directed, its general surface shall conform closely to the pavement datum. Stones in adjoining courses shall break joint not less than three (3) inches.
74. Ramming.[[35]]—After the blocks are set each individual block shall be thoroughly rammed to give it a firm bearing in the sand and to bring its top to the prescribed pavement datum. The rammers used shall have wooden faces not more than four inches in diameter, and shall weigh not less than thirty (30) pounds. Blocks or sections of blocks whose tops under the ramming remain above or sink below the pavement datum shall be taken up and reset so that after the ramming is completed their tops shall coincide with the pavement datum.
75. Filling the Joints.[[36]]—After the ramming specified in Sect. 74 shall have been completed, the joints between the paving blocks shall be filled in the following manner:
All the joints for a distance of three feet out from the curbstones, and three contiguous joints continuous across the street, with the included end joints, at intervals of about fifty (50) feet in the length of the street, shall be filled with gravel and bituminous paving cement. The gravel used shall be of such size that all will pass through a screen having five-eighths (⅝) inch meshes, and all will be held on a screen having one-fourth (¼) inch meshes. When used, the gravel must be free from refuse and street dirt. The bituminous paving cement shall be composed by weight of straight-run coal-tar pitch of the hardness commonly known as number six, to which has been added and thoroughly mixed, while both are in a melted condition, twenty per cent. (20%) by weight of refined Trinidad asphalt, or other asphalt, equal for the purpose, and twenty per cent. (20%) by weight of Portland cement. These ingredients must be thoroughly mixed, and kept agitated until used.[[37]]
The joints will first be filled with the gravel, which shall be perfectly dry, and heated so that when put in the joints it will be at a temperature of about three hundred (300) degrees F. The paving cement, heated to a temperature of about three hundred (300) degrees F., shall be at once, while the gravel is still hot, poured from a spouted vessel into the joints until the interstices of the gravel are entirely filled to the surface of the pavement, repouring being resorted to to accomplish this result whenever necessary.
All the joints in the pavement other than those named above shall then be completely filled with Portland cement grout, in the following manner:
The grout shall be composed of equal parts by volume of sand (Sect. 30) and Portland cement (Sect. 29), a quick-setting cement being preferred. The sand and cement shall be first thoroughly mixed dry and then enough water added to make a grout of such consistency that it will flow like thick cream, and the mixing continued until a homogeneous mass is produced and until the grout is applied to the pavement. The grout shall be prepared in water-tight boxes of a convenient size. Before applying the grout the pavement shall be thoroughly dampened by sprinkling. The grout shall be removed from the mixing box and spread over the pavement with scoop shovels, in two courses, the first being sufficient to about half fill the joints, and the second, which shall be applied before the first has begun to set, shall be sufficient to entirely fill the remaining space in the joints. As the grout is applied to the pavement it shall be swept about with brooms until it all enters the joints.
76. Order of Work.—The sand bed shall not be put in place more than fifty (50) feet ahead of the block setters. The ramming and filling of the joints shall follow closely the block setting, but no ramming shall be done within less than six (6) feet of the face of the block setting; and the final joint filling shall be kept completed to within twenty-five (25) feet of the ramming; except that all the work rammed during any day shall have the joint filling completed before the cessation of work on that day. The street shall not be opened to travel until the grout has thoroughly set.
77. Fitting Paving Around Other Structures.—The size of blocks and the width of courses shall, as the block laying approaches bridge stones, curbs and other structures, or in making closures with other sections of pavement, be so selected and adjusted that joints not over three-quarters (¾) inch in width shall result, without breaking blocks or splitting courses.
78. Street Railroad Tracks.—Where railroad tracks exist in the street the paving blocks shall be laid against the rail in the following manner: