32 BULLETIN 257, U. S. DEPARTMENT OP AGRICULTURE. 



At the time of inspection the section generally presented a firm 

 smooth surface. A few small cup-holes had formed where repairs 

 were made before the last surface treatment, and were undoubtedly- 

 due to a poor distribution of oil asphalt in placing the patches. 



Section No. 10 (Residual Petroleum — Surface Treatment). 



The development of irregular humps and ruts upon this section, 

 noted in U. S. Department of Agriculture Bulletin No. 105, con- 

 tinued during the past year, until the surface was in such condition 

 that it was deemed advisable to remove the surface mat as far as 

 possible and re-treat the entire section. Accordingly the surface mat 

 was broken up by means of a 3-ton scarifier, and as much of it re- 

 moved as could be easily separated from the macadam stone. The 

 old surface was then loosened by scarifying and picking, shaped with 

 rakes, and brought to grade by the addition of a thin course of f -inch 

 limestone. After rolling, limestone screenings were scattered over the 

 surface just sufficient in quantity to fill the surface voids. The sur- 

 face was then thoroughly bonded by sprinkling with water and rolling. 



The following table gives the materials and cost data per square 

 yard for the reconstruction of the water-bound macadam surface. 



Table 23. — Materials and cost data for reconstruction of section No. 10, Chevy Chase, Md. 



Materials used per square yard : 



1-J-inch limestone cubic yard . 



f-inch limestone " do. .. 



Limestone screenings do . . . 



Cost per square yard: 



l-|-inch limestone cents. 



f-inch limestone do. . . 



Limestone screenings do 



Sweeping old surface do 



Removing old surface mat do. . . 



Scarifying, and raking scarified surface do . . . 



Spreading stone do... 



Sprinkling ' do. . . 



Rolling do. . . 



0.001 

 .016 

 .007 



.173 

 4.080 

 1.823 



.145 

 2.970 

 2.674 

 1.041 



.764 

 2.979 



Total do 16. 629 



On November 3 and 4, after several days' traffic over the water- 

 bound surface, the section was given a cold surface treatment with 

 an asphaltic petroleum of the analysis given in Table 22. This was 

 covered with washed f-inch gravel. The bituminous material was 

 applied by allowing it to run from the bungs of the barrels directly 

 upon the road, which had previously been swept with hand brooms 

 to remove loose material. The oil was broomed over the surface 

 until no uncoated spots remained, and it was found that considerable 

 brooming was necessary, owing to the fairly large amount of dust 



