96 HIGHWAY CONSTRUCTION 



be adequately supported, or the load coming upon it may force it 

 downwards and cause unevenness, a eondition which conduces to the 

 rapid destruction of the pavement. Several forms of foundation have 

 been used such as gravel, plarik, sand, broken stone, and concrete. 

 The last mentioned is doubtless the best. 



Sand Cushion. The sand cushion is a layer of sand placed on 

 top of the concrete to form a bed for the brick. Practice regarding 

 the depth of this layer of sand varies considerably. In some cases it 

 is only half an inch deep, varying from this up to three inches. The 

 sand cushion is very desirable, as it not only forms a perfectly true and 

 even surface upon which to place brick, but also makes the pavement 

 less hard and rigid than would be the case were the brick laid directly 

 on the concrete. 



The sand is spread evenly, sprinkled with water, smoothed, and 

 brought to the proper contour by screeds or wooden templets, properly 

 trussed, mounted on wheels or shoes which bear upon the upper sur- 

 face of the curb. Moving the templet forward levels and forms the 

 sand to a uniform surface and proper shape. 



The sand used for the cushion-coat should be clean and free from 

 loam, moderately coarse, and free from pebbles exceeding one-quarter 

 inch in size. 



Manner of Laying. The bricks should be laid on edge, as closely 

 and compactly as possible, in straight courses across the street, with 

 the length of the bricks at right angles to the axis of the street. Joints 

 should be broken by at least 3 inches. None but whole bricks should 

 be used, except in starting a course or making a closure. To provide 

 for the expansion of the pavement, both longitudinal and transverse 

 expansion-joints are used, the former being made by placing a board 

 templet seven-eighths of an inch thick against the curb and abutting 

 the brick thereto. The transverse joints are formed at intervals 

 varying between 25 and 50 feet, by placing a templet or building-lath 

 three-eighths of an inch thick between two or three rows of brick. 

 After the bricks are rammed and ready for grouting, these templets are 

 removed, and the spaces so left are filled with coal-tar pitch or asphal- 

 tic paving cement. The amount of pitch or cement required will vary 

 between one and one and a-half pounds per square yard of pavement, 

 depending upon the width of the joints. After 25 or 30 feet of the 

 pavement is laid, every part of it should be rammed with a rammer 



