[43]. The specifications of the Association for Standardizing Paving Specifications require that all paving brick shall have lugs on one side, and allow a projection of ¼ inch from the face of the brick. The object is to provide a wider joint between the bricks in order to facilitate the filling of the joints. The author does not believe these lugs necessary, nor that brick without lugs, but otherwise acceptable, should be excluded. It is certain that many of the best brick pavements ever constructed have been built of bricks without lugs. If lugs are required they should preferably not project more than one-eighth inch. The same reasons that make narrow joints desirable in other block pavements apply equally to brick pavements.
[44]. The A. S. P. S. Specifications permit a loss of 22% with the block size, but do not name a permissible loss for “brick” size.
[45]. Absorption of less than one-half of one per cent., usually indicates that a shale brick has been over-burned, resulting in increased brittleness.
[46]. The absorption test is falling into disfavor, particularly with the manufacturers. The author believes that it possesses a distinct value and should be retained.
[47]. The object of this is to make a gutter offering less obstruction to the flow of water.
[48]. This is the simplest and most effective way to detect soft and underburned brick.
[49]. If the joints are to be filled with bituminous cement, substitute for sections 90 and 91 the following:
Directly after the completion of the rolling and ramming, all the joints in the brick pavement and between it and the curbing, manholes or other structures, shall be filled with a bituminous cement in the following manner:
The bituminous cement shall be composed, by weight, of one hundred (100) parts of straight-run coal-tar pitch commercially known as number four and twenty (20) parts of refined Trinidad asphalt melted and thoroughly mixed together at a temperature of about 350° F., to which shall be added twenty (20) parts of dry Portland cement, which shall be thoroughly incorporated with the hot bitumen until a homogeneous mass is produced, and kept agitated so as to prevent settlement or separation until the cement is used. If another asphalt is used instead of Trinidad the quantity added to the pitch must be sufficient so that the cement will not flow at a temperature lower than one hundred and twenty-five degrees Fahrenheit (125° F.). This cement while at a temperature of about 325 degrees F. shall then be poured from a spouted vessel into all joints and vacancies in the pavement until they are completely filled, repouring being resorted to if necessary to accomplish the complete filling of the joints. After the joints are thus filled a layer of sand one-half inch thick will be spread over the whole surface of the pavement and allowed to remain until the engineer shall direct its removal.
[50]. The bituminous-cement joints are principally for the purpose of providing for the expansion of the pavement in very hot weather.