408 ROADS AND PAVEMENTS 



cushion coat should be laid directly on the binder course, or on 

 the concrete foundation when no binder course is used, and 

 should be of such depth as to give a thickness of } in. when 

 consolidated by rolling. The materials for the surface coat, 

 which is laid on the cushion coat, should be delivered on the 

 pavement in carts, at a temperature of about 250 F.; when 

 the temperature of the air is below 50, each cart should be 

 equipped with a suitable heating apparatus that will prevent 

 the paving material from cooling below the proper temperature. 



The material of the surface coat should be carefully spread 

 on the cushion coat to such a depth as will give a uniform sur- 

 face and a thickness of 2 in. after being consolidated; hot iron 

 rakes should be used for this purpose. The material should-first 

 be moderately compressed by hand rollers; a small amount of 

 hydraulic cement should then be spread lightly over it, after 

 which it should be thoroughly compacted by continued rolling 

 with a heavy steam roller for not less than 5 hr. for each 1,000 

 sq. yd. of surface. 



One Coat. When the pavement is given only one coat of 

 asphaltic material, it is laid in much the same manner as just 

 described for the surface coat. The material should be delivered 

 in carts, at a temperature not below 250 nor above 310 P.; 

 while in the carts, it should be protected with canvas covers 

 when the temperature of the air is below 50 F. It should be 

 spread on the foundation to such depth, as will give a uniform 

 surface and a thickness of 2} in. after being consolidated. 

 The material should first be moderately compressed by hand 

 'rollers, and a small amount of hydraulic cement should be 

 spread lightly over it, the same as described for the surface 

 coat, after which it should be thoroughly compacted by rolling 

 with a steam roller weighing not less than 5 T., followed by a 

 second roller weighing not less than 10 T.; the rolling should 

 be continued for not less than 10 hr. for each 1,000 sq. yd. of 

 surface. 



Bitulithic Pavements. A bitulithic pavement is composed 

 of broken stone ranging in size from 2 in. to dust, mixed in the 

 necessary proportions to reduce the voids to about 10%, 

 and cemented together by a bituminous cement manufac- 

 tured either from coal tar, from asphalt, or from a combina- 



