DUST PREVENTION AND' ROAD PRESERVATION". 33 



Section No. 8.- — Refined water-gas tar preparation — Surface treatment. 



During the spring of 1913 the first surface treatment began to 

 lose its efficiency on this section and a number of small, shallow 

 chug holes developed, particularly toward the north end. In order 

 to prevent further deterioration, these were repaired with a light 

 application of heavy refined coal tar and fine gravel. On September 

 12, 1913, the section was given a surface treatment of the same trade 

 product which was originally used, the analysis of which is shown 

 in the following table: 



Table 32.' — Analysis of refined tvater-gas tar 1 used in second surface treatment of sec- 

 tion, No. S. 



Specific gravity 25°/25° C 1. 120 



Viscosity, Engler, 50° C, 50 c.c. specific 12. 8 



Per cent of free carbon 0. 95 



Distillation: By volume. By weight. 



Water ....percent.. 0.2 0.2 



First light oils to 110° C do ... . .2 .2 



Second light oils 110°-170° C do *i.3 1.0 



Heavy oils 170°-270° C do ... . 2 23. 20. 5 



Heavy oils 270°-315° C do ... . 2 17. 8 16. 2 



Pitch residue do 57. 5 61. 8 



Total do.... 100.0 99.9 



The surface was swept and the material was applied by an auto- 

 mobile distributor and was charged at 9 cents per gallon distributed on 

 the cleaned road. The application was immediately covered with 

 clean limestone screenings of a size that would pass a 1-inch screen, 

 and lightly rolled. The, cost data for this treatment are given in 

 Table 34. The section how offers a fairly uniform, attractive surface, 

 well bound and comparatively free from ruts or depressions. 



Section No. 9. — Asphaltic petroleum- — Surface treatment. 



This section, like section No. 8, began to lose the effect of its first 

 treatment in the spring of 1913. The deterioration was most marked 

 on the outer third of the road adjacent to the gutter, where traffic 

 was lightest. This was evidently due to the fact that the surface 

 lacked the ironing action of traffic and, lying somewhat open and 

 porous, was rutted by the combined action of water and detritus 

 which worked over upon it. A number of shallow, worn depressions 

 developed, principally at the south end of the section. These were 

 filled by applying a hot paint coat of the oil asphalt used in section 

 No. 5 and then filling the depression with clean 1-inch limestone 

 screenings. 



On July 30 and 31, immediately after these patches had been made, 

 the entire section was given a surface treatment of the same trade 



i Sticky, fluid. 2 Clear. 



