56 
BULLETIN 586, U. S. DEPARTMENT OF AGRICULTURE. 
from the north end on the track side and extend about two-thirds 
across the width of the surface. Slight pitting, due to the disinte- 
gration of exposed rock particles, was still noticeable, but there was 
no increase over that reported last year. The repairs made at the 
expansion joint, described in the last report, appear to have been 
adequate, as no further trouble has been experienced at this point. 
Experiment No. 3 — Cement concrete and oil cement concrete; sur- 
faces treated with bituminous materials. — During the autumn the 
entire surface of experiment No. 3 received a carpet treatment with 
torpedo sand as a top-dressing. Sections A, B, G, and H were treated 
with a water-gas tar preparation, and sections C, D, E, and F with 
a residual asphaltic petroleum. Sections I and J received a carpet 
coat in two applications of one-half gallon of cold asphaltic petroleum. 
The first application was top-dressed with torpedo sand and allowed 
to stand 48 hours, after which the second application was made and 
additional top dressing applied. The material and cost data for 
these treatments are given in Table 59. 
Table 59. — Materials and cost data for surface retreatment in 1916, Experiment No. 3. 
Item. 
Sections C, 
D,E,and F, 
residual 
asphaltic 
petroleum. 
Sections A. 
B,G,and H, 
water-gas 
tar prepa- 
ration. 
Sections 
I and J, 
asphaltic 
petroleum. 
Area treated 
Quantity of material per square yard: 
Bituminous material 
Sand 
sq. yds.. 
galls.. 
cu. yds.. 
1,725 
0.275 
.0078 
1,840 
0.306 
.0084 
667 
0.499 
.0149 
Cost per square yard (cents): 
3.00 
1.64 
.30 
.89 
.27 
.23 
4.14 
1.77 
.12 
.87 
.25 
.66 
5.94 
Sand , 
3.18 
- 
.44 
.85 
.44 
.80 
Total 
6.33 
7.81 
11.65 
Sections A and B: These sections were in almost perfect condi- 
tion except for a distance of about 30 feet at the south end, which 
was treated in cold weather. Over this portion of the experiment 
there were quite a number of small scars, where the treatment had 
been removed by traffic. 
Sections 0, B, E, and F: This mat was noticeably heavier than 
that resulting from the application of water-gas tar and had a dis- 
tinctly leathery texture. About 10 feet south of the E.post there was 
one small break, the only one on the section. Slight calk marks were 
visible and quite generally distributed, and there appeared to be a 
tendency to push, but the wavy condition was barely noticeable. 
Sections G and H: These sections showed no breaks, and the sur- 
face was smooth, but the wear near the center had exposed the 
concrete in a number of places. 
