Note 33 — PART I SPECIFICATIONS FOR STREET ROADWAY PAVEMENTS (continued 2)

The widths of joints here specified as allowable are based upon the assumption that they will be filled with Portland cement grout as specified in Sect. 75. If this grout filling is used narrower joints are not necessary, as the grout has sufficient strength to support the corners of the blocks, and sufficient hardness to resist the wear of travel (largely protected as it is by the blocks themselves) and to cause the blocks to wear down quite evenly.

In many European cities the specifications require much closer joints. The granite there available appears to break out naturally to truer lines and better surfaces than that used in the Eastern states, at least, so that the cost of dressing the blocks abroad is not as great as here.

The City of New York has recently adopted specifications for “Special Improved” Granite Block pavement intended to approximate the Liverpool standard. These require that the blocks shall be not less than 6 nor more than ten inches long, not less than 3½ nor more than 4½ inches wide and five inches in depth. “The blocks are to be rectangular with tops and sides uniform in thickness, to lay closely, and with fair and true surface, free from bunches and so cut or dressed that when laid stone to stone the joints shall not exceed ⅜ of one inch. The head of the block shall be so cut that it shall not have more than one-quarter of an inch depression from a straight-edge laid in any direction across the head and held parallel to the general surface of the block.” The joints are filled with bituminous cement.

The above specification is very difficult to meet from the granite available to New York without excessive and expensive cutting, and examination of the pavements laid under these specifications shows that the joints greatly exceed the width specified.

It is believed that equally good results may be secured by permitting somewhat wider joints filled with grout, and the cost would be materially reduced.