ROADS 165 



In the mixing method, the second crust or layer of stone 

 is mixed or covered with bitumen before spreading. This is 

 also true of the upper layer of sand or chips, which is thor- 

 oughly mixed with bitumen before applying to the surface. 

 It is expected that roads of this type will largely replace the 

 standard or water-bound type. 



Cost of Stone Roads. The cost of stone roads will vary 

 largely with the cost of materials; this in turn being directly 

 dependent upon their availability. The cost in different 

 parts of the United States varies from $1.20 to $1.50 per 

 square yard, and from $4000 to $10,000 per mile. 



Maintenance. Macadam roads must be given constant 

 attention or they will be rapidly destroyed. All ruts should 

 be quickly filled with new material and not be allowed to 

 become larger. After several years of wear, depending 

 upon the durability of the materials used, it will be neces- 

 sary to apply a new layer of materials. This is usually 

 accomplished by loosening or scarifying the surface, leveling 

 or rolling it until thoroughly compact, and then applying new 

 material in a layer two or three inches thick, depending upon 

 the condition of the road. This repair layer is applied in a 

 way similar to the laying of the second course in the original 

 construction. 



Brick Roads. In some localities where stone is very 

 expensive or where good durable brick may be obtained 

 cheaply, brick roads will be found to be the most practical. 

 In the construction of a brick road, the subgrade or foun- 

 dation is carefully prepared by grading and rolling, and the 

 sides of the road are provided with concrete or wooden 

 curbs, to hold the brick in place. On the subgrade a course 

 of stone is laid and thoroughly rolled, or a coarse layer of 

 concrete is spread, usually about 6 inches deep. On this 

 course a layer of sand is spread and smoothed as a cushion 



