DUST PREVENTION AND ROAD PRESERVATIOIST, 1915. 25 



cessful. The condition of the surface of each section at the time of 

 treatment is discussed in detail in connection with each experiment. 

 The cost of this repair work was $70. 



Experiment No. 1 begins at the city hmits of Rockville, and the 

 remainder of the series follow in regular numerical order. The 

 details of the work are subjoined. 



Table 24. — Mechanical analysis of gravel used on Rochville-Potomac Road. 



Per cent. 



Passing |-incli screen, retained on J-inch screen 9.8 



Passing ^-inch screen, retained on |-inch screen 62. 2 



Passing ^-inch screen, retained on|^-inch screen 25. 2 



Passing -^-inch. screen 2. 8 



Total 100.0 



Experiment No. 1. — ^Asphaltic Petroleum, Cold Application, Corresponding 

 TO Experiment No. 3, on Rockvillb Pike. 



Location: Station 0+00 to station 4545+75. 



Length: 4,575 feet. 



Total area: 7,625 square yards. 



Date of application: September 23 and 24. 



Temperature of petroleum: About 90° to 100° F. 



Table 25. — Analysis of asphaltic petroleum used in Experiment No. 1. 



Specific gravity, 25°/25° C 0. 944 



Flash point, ° C 26 



Burning point, ° C 90 



Viscosity, Engler 50 c. c. at 25° C, specific 86. 6 



Loss, 5 hours at 163° C, 20 grams, per cent 26. 54 



Float test on residue at 50° C. (time) 2^ 0^' 



Per cent of total bitumen insoluble in 86° B. naphtha 13. 70 



Fixed carbon, per cent 7. 93 



Soluble in CS2 (total bitumen), per cent 99. 94 



Organic matter insoluble, per cent 06 



Inorganic matter insoluble, per cent .00 



Total 100. 00 



Except for a few short sections, the total length of which did not 

 exceed 300 feet, the stone in the surface of Experiment No. 1 was loose 

 and covered with a layer of dust. The surface was swept lightly to 

 avoid displacing the stone, and masses of undesirable matter were 

 removed with hoes and shovels. In order to facilitate the adhesion of 

 the petroleum to the dusty stones, much hand-brooming was required. 

 The oil was permitted to He for about 2 hours before the gravel was 

 apphed. The oil was shipped in a tank car, which was placed about 

 1 mile from the beginning of the section. 

 52086°— Bull. 407—16 4 



