60 



BULLETIN 407^ U. S. DEPARTMENT OF AGKIOULTUBE. 



MAINTENANCE DURING 1915. 



Repairs on these experiments, together with the total cost of each 

 experiment to December 31, 1915, are shown in Table 60. 



Table 60. — Surface maintenance costs of 1912 experiments at Chevy Chase, Md., to 



December 31, 1915. 





Date 

 com- 

 pleted. 



Area. 



Maintenance cost of experi- 

 ment. 



Total cost per square yard 

 (cents.) 



Experiment No. 



Total for 

 projects 

 to Dec. 

 31, 1914. 



1915 



Total. 



Construe- Mainte- 

 tion. nance. 



! 



Total. 



1 



1912 

 ...do 



Sq. yds. 

 1,498 

 1,400 

 2,837 



3,019 

 3,013 

 2,055 





83.25 

 3.55 

 2.54 



18.35 



20.66 



.41 



S3. 25 i 1 Sfi- 62 



0.22 

 .55 

 .13 



.68 

 .75 

 .08 



186. 84 



2 



S4.ll 

 1.03 



2.15 

 2.07 

 1.36 



7.66 

 3.57 



20.50 

 22.73 



1.77 



195. 65 

 1 142. 12 



1 151. 21 



1 143. 13 



258. 21 



196. 20 



3 



4 



Spring, 



1913 

 ...do 



142.25 

 151. 89 



5 



...do 



143.88 



6 



...do 



258.29 









1 Weighted average price for different aggregates. 



SUPPLEMENTARY REPORT OF EXPERIMENTS AT CHEVY CHASE, MD., 



1911. 



BITUMINOUS CONSTRUCTION AND SURFACE TREATMENT. 



The original reports of these experiments are given in Circulars 

 Nos. 98 and 99, Office of Public Roads, and supplementary reports 

 appear in U. S. Department of Agriculture Bulletin No. 105, and 

 again in Department Bulletin No. 257. The following report is 

 based upon an inspection made February 28, 1916. 



Section No. 1. — Refined Coal Tar, Penetration Method. 



At the time of the inspection this experiment presented a surface 

 almost intact, except at the narrowest part on the curve, where traffic 

 is much concentrated. Here the mat is wearing off in sections. The 

 experiment is becoming somewhat rough along the gutter on the west 

 side, due probably to failure of the foundation. A similar condition 

 is noticeable in many of the sections of this project. 



Section No. 2. — Refined Coal Tar, Modified Gladwell Method. 



The condition of this section continues about the same as when 

 last inspected, except for a slightly increased roughness along the 

 gutter edge. 



Section No. 3. — Fluxed Native Asphalt, Penetration Method. 



Wear on this section continues along the line indicated last year. 

 Those areas which were without mat at the time of the last inspection 

 are quite generally marked with small pits which are adjacent to large 

 particles of exposed aggregate. 



