DUST PREVENTION AND ROAD PRESERVATION, 1914. 23 



brittle, especially along the sides of the road, although the treatment 

 still remained generally intact. Section No. 2 had developed several 

 holes of considerable area, but otherwise the surface was in excellent 

 condition. Section No. 3 had several small holes, and the surface 

 mat was largely worn off. The surface of section No. 4 was smooth 

 and regular, but the large stones of the macadam were generally 

 showing. The only repair necessary in this section was a water-bound 

 patch approximately 6 square yards in area on the northwest side of 

 the curve leading toward Twelfth Street, where there is practically 

 no traffic. 



In addition to this large patch, others of water-bound macadam 

 were placed in sections 2 and 3. The total area of such patches was 

 about 11 square yards. 



The sections were then swept with hand brooms and given a sur- 

 face treatment of the same type of bituminous material as that 

 originally used, and covered with a fine torpedo sand. Some bitu- 

 minous material had remained from the previous treatment, as fol- 

 lows: 130 gallons of residual petroleum for section No. 3, which was 

 sufficient to treat the entire section, and 50 gallons of water-gas tar 

 preparation, which was used on the south end of section No. 1. 



Application of the bituminous material was accomplished by allow- 

 ing it to run from the bungs of the barrels or drums directly upon the 

 road and distributing it with push brooms. It was covered imme- 

 diately with sand. 



Analyses of additional materials purchased for this work are given 

 in the following tables: 



Table 15. — Mechanical analysis of sand used in surface treatment at Washington, T). C, 



1914. ■ 



Retained on £-inch screen per cent. . 11. 8 



Passing J-inch screen, retained on 10-mesh sieve do 6. 7 



Passing 10-mesh sieve, retained on 20-mesh sieve do 17. 9 



Passing 20-mesh sieve, retained on 30-mesh sieve do 9.3 



Passing 30-mesh sieve, retained on 40-mesh sieve do 12. 3 



Passing 40-mesh sieve, retained on 50-mesh sieve do ] 0. 9 



J';i--ih'_' ".O-iiK-.sh sieve, retained on 80-mesh sieve do 20. 4 



Passing 80-mesh sieve, retained on 100-mesh sieve do 3. 7 



Passing 100-mesh sieve, retained on 200-mesh sieve do 3. 7 



.•/ 200-mesh sieve do 3. 3 



Total do .... 100. 



Table l f ). Analysis of water gas tar preparation used on section No. i. 



Sped fie gra vity 25°/25° ] . 091 



Viscosity, Bngler, 100 c. c at 50° 0., specific 18.4 



Free carbon per cent. . 2. 22 





