DUST PREVENTION AND ROAD PRESERVATION, 1915. 55 
SUPPLEMENTARY REPORT OF EXPERIMENTS AT WASHINGTON, B. C, 
1912. 
TAR PREPARATION AND OILS, SURFACE TREATMENT. 
The original report of these experiments was published in Circular 
No. 99 of the Office of Public Koads, and inspection reports have 
appeared in United States Department of Agriculture Bulletins Nos. 
105 and 257. The following report describes the condition of the 
pavement before re- treatment, the extent of the repairs during 1915, 
and the condition of the experiments when inspected on February 
25, 1916. 
Section No. 1. — Refined Water-Gas Tar Preparation. 
Section 1 appeared intact and required neither repairs nor re- 
treatment during the summer of 1915. 
Section 2 raveled locally in some spots to a depth of 2 inches or 
more. Most of these failures were along the wheel tracks. Only one 
was at the edge, and this failure was probably due in some measure 
to defective drainage. The mat was worn unevenly, and over con- 
siderable areas was entirely gone. The entire section was repaired 
with penetration patches, in which an oil asphalt and limestone were 
used, top-dressed with trap chips. 
The cost of patching was : 
Labor .. $9.50 
Materials 8.10 
Total ....- 17. 60=$0.0155 per square yard. 
The section was then re-treated with the same materials originally 
used. An analysis of the asphaltic petroleum is given in Table 57. 
Section No. 3. — Residual Petroleum. 
Section 3 had been persistently muddy during the last winter and 
spring. The oily mud had been forced aside from the prevailing 
wheel tracks, so that many bare places and depressions existed, and 
one long rut about 1 J inches deep and 8 to 10 inches wide had devel- 
oped along the north edge for some 75 or 80 feet at the west end. 
Table No. 56. — Cost of preliminary repairs per square yard. 
Section. 
Labor. 
Materials. 
Total. 
1 
2... = 
3 
$0.0084 
.0109 
$0.0071 < 
.0073 
, $0.0155 
.0182 
4 
