DUST PREVENTION AND ROAD PRESERVATION, 1916. 
55 
tion of the surface appeared imminent. It appeared probable that 
reconstruction of the macadam would be necessary. 
Section 4 was re-treated in October, 1916, and at the time of in- 
spection was in almost perfect condition. A few small spots near 
the north end showed excessive wear, but otherwise the surface was 
uniform and intact. The quantities and costs appear in Table 58, 
and the characteristics of the bitumen, which was the same as used 
in original construction, were the same as of that used on section 3. 
Table 58. — Materials and cost data for surface re-treatment, Washington, D. C, in 1916. 
Item. 
Experi- 
ment No. 
1, refined 
water-gas 
tar prepa- 
ration. 
Experi- 
ment No. 
2, asphaltic 
petroleum. 
Experi- 
ment Nos. 
3 and 4, 
asphaltic 
petroleum. 
Area treated sq. yds. 
Quantity of material per square yard: 
Bituminous material galls. 
Sand cu. yds. 
Cost per square yard (cents): 
Bituminous material 
Sand 
Cleaning surface 
Hauling materials 
Applying bituminous materials 
Applying sand 
Supervision 
Total 
1,318 
0.138 
.0064 
1.38 
1.03 
.05 
1.08 
.42 
.41 
.41 
4.78 
1,129 
0.152 
.0053 
70 
2,041 
0.113 
.0046 
1.81 
.73 
.13 
.88 
.56 
.17 
4.64 
CHEVY CHASE, MD., 1912. 
BITUMINOUS CONCRETE, CEMENT CONCRETE, OIL CEMENT CONCRETE, VITRIFIED 
BRICK, BITUMINOUS SURFACE TREATMENTS ON CONCRETE. 
The original reports of these experiments were begun in Circular 
No. 99 of the Office of Public Roads and completed in Bulletin No. 
105, U. S. Department of Agriculture, and supplementary reports 
have been published in Bulletins Nos. 257 and 407, U. S. Department 
of Agriculture. The following report covers the condition of exper- 
iments on February 21, 1917. 
Experiment No. 1 — Bituminous concrete, Topeka specification. — 
This section continued in essentially the same condition as at last 
report. At points 15, 25, and 30 feet from the north end of the lime- 
stone section three cracks appeared, extending about one-half of the 
width of the surface on the gutter side. About 70 feet from the 
north end of the trap section, near the gutter, there were two breaks 
with an area of about 1 square foot each. In one of these the con- 
crete base was exposed. The slight pitting noted in the last report 
had not increased. 
Experiment No. 2 — Bituminous concrete, District of Columbia speci- 
fication. — This surface continued in the same condition as when last 
reported. Two cracks have appeared at 50 and 65 feet, respectively, 
