DUST PREVENTION AND ROAD PRESERVATION, 1915. 63 
Section No. 8. — Refined Water-Gas Tar Preparation, Surface Treatment. 
This section presents a very un-uniform appearance over most of 
the area. The aggregate now shows and the surface is ready for a 
seal coat. This treatment was postponed during the past season 
only at the expense of considerable repair. In a few places there is 
a heavy mat that appears to have been pushed up by traffic, but 
elsewhere the mat is generally worn off. 
Section No. 9. — Asphaltic Petroleum, Surface Treatment. 
During the past season, sections 9 and 10 were re- treated uniformly. 
At the time of inspection they much resembled each other, but 9 is 
in better general condition. There are only three or four breaks 
through the mat and, though wavy and uneven, the surface is nearly 
intact. The marked difference between the east and west halves 
of the section is not nearly so great as in No. 10. Table 63 gives an 
analysis of the bituminous material used, and the cost of this re-treat- 
ment is given in Table 64. 
Table 63. — Analysis of asphaltic petroleum used on sections 9 and 10. 
Specific gravity, 25°/25° C 0. 963 
Flashpoint, °C 31 
Burning point, °C 84 
Viscosity at 25° C, 50 c.c, Engler specific 128. 4 
Loss, 5 hours, at 163° C. , 20 grams, per cent 23. 14 
Float test on residue, 32° C. (time) 2' 37" 
Float test on residue, 50° C. (time) V 4" 
Percentage of total bitumen insoluble in 86° B. naphtha 5. 96 
Fixed carbon, per cent 4. 62 
Soluble in CS 2 (total bitumen), per cent 99. 94 
Organic matter insoluble in CS 2 , per cent 0. 04 
Inorganic matter insoluble in CS 2 , per cent 0. 02 
Total 100. 00 
Section No. 10. — Residual Petroleum, Surface Treatment. 
This experiment continues to be the most troublesome section of 
the entire project. Reference to previous reports will disclose that 
it has had repeated attention, being once scarified and rebuilt and 
once re-treated. In the spring of 1915, after having been very 
muddy during the preceding winter, it had an irregular wavy mat 
and there were numerous spots where the aggregate was exposed. 
It rapidly disintegrated at these points and considerable repair work 
became necessary. Finally, on August 16 to 18, 1915, a second 
re-treatment, using asphaltic petroleum, was given. This re-treat- 
ment was extended over experiment No. 9 and its details are given 
in the description of that section. At the time of inspection the 
west half of the section against the track was in fair condition, but 
