The sub-grade and the pavement foundation shall extend under the rails uninterrupted except by the ties or other structures connected with the railroad track. For a distance of sixteen (16) inches, on each side of the rail, measuring from the center thereof, there shall be spread on the pavement foundation a layer of mortar not less than one and one-half (1½) inches thick, composed of one (1) part of cement and three (3) parts sand, complying with the requirements of Sections 29 and 30. Upon this layer of mortar shall be set, against the rail, and on each side of it, selected paving blocks, securely bedded in the mortar before it shall have begun to set.[[38]] Alternate blocks shall be long and short so as to break joint with the blocks of the adjoining pavement. Selected blocks with well dressed top surfaces shall be used and their tops shall be set as nearly as practicable at the level of the top of the rail, but not so high that the car wheels will ride upon them. In setting the blocks they shall be firmly bedded into the mortar by the use of paving hammers, but they shall not be thereafter rammed. As the blocks are set, any space between the paving blocks and the web of the rail shall be filled with mortar of the quality described above. The placing of these blocks shall not precede by more than ten (10) feet the block laying on the street. Care must be taken not to disturb the bedding of these blocks in the laying of the adjoining pavement, or otherwise. The joints shall be filled with grout as specified in Sect. 75.
The construction along slot-rails shall be the same as described above, except that blocks of special size or shape may be required, as the Engineer may direct.
79. Bridge Stone Crossings.—Where directed by the Engineer, the old bridge stone shall be redressed and relaid, as hereinafter specified for new bridge stone, and shall be moved from the point where taken up to the point where they are to be relaid, by the Contractor at his expense.
New bridge stone shall be of the same quality of granite as the paving blocks and free from imperfections. They shall not be less than three and one-half (3½) nor more than six (6) feet long, eighteen (18) inches wide and of a uniform thickness not less than six (6) nor more than eight (8) inches, but these dimensions may be varied by the Engineer where necessary to fit the stone into special locations.
Their top shall be well dressed to a true plane surface not varying in evenness more than one-quarter (¼) inch. The sides shall be dressed perpendicular to the face so as to joint closely against the paving blocks. The ends shall be cut to lines making an angle of from 60° to 45° with the longitudinal axis of the stones[[39]] and so dressed and to such a bevel that when set in the curved surface of the street, the joint between adjoining stones shall not be wider than three-eighths (⅜) inch from top to bottom.
Bridge stones shall be set in advance of the block laying, over the concrete street foundation, in a bed of sand or gravel in which they shall be firmly bedded. Their upper surface shall conform truly to the pavement datum. They shall be set accurately to the lines given by the Engineer. Where the crosswalk requires more than one width of bridge stone, the courses shall be laid parallel to, and at such distance from each other as the Engineer may direct, and the space between courses shall be filled with paving blocks laid as specified for other parts of the street.
BRICK PAVEMENT[[40]]
80. Sub-grade.—The sub-grade for brick pavement shall be prepared in accordance with Sect. 26, and shall be finished to a surface ... inches below and parallel to the pavement datum.
81. Foundation.—The foundation for brick pavement shall be of hydraulic concrete[[41]] prepared in accordance with Sections 28 to 37 inclusive. Its thickness shall be ... inches and its upper surface shall, when completed, be parallel to and at a depth below the pavement datum equal to the depth of the brick plus one and one-fourth (1¼) inches. The surface of the foundation shall not vary more than one-half (½) inch above or below that depth.
82. Paving Brick.—The linear dimensions of paving brick may vary between the following limits: In length, from eight and one-half (8½) to nine and one-half (9½) inches; in width, from two and one-fourth (2¼) to three and one-half (3½) inches; in depth, from four (4) to four and one-eighth (4⅛) inches; but the length shall not be less than two and one-half (2½) nor more than three and three-fourths (3¾) times the width.[[42]] The corners shall all be rounded off to a radius of not less than one-eighth (⅛) nor more than three-sixteenths (³⁄₁₆) inch. The brick for any one contract shall be all of the same kind and of the same standard size, and the individual bricks shall not vary in length more than three-sixteenths (³⁄₁₆) inch, nor in width more than one-eighth (⅛) inch from the size adopted as standard. Raised lugs or letters are permissible on one side of each brick but must not project more than three-sixteenths (³⁄₁₆) inch from the general surface.[[43]]