DUST PREVENTION AND ROAD PRESERVATION, 1916. 
51 
Experiment No. 4 — Residual asphaltic petroleum, hot application. — 
Although section 4 had been patched heavily for over a year, it was 
decided in the summer to attempt to carry it through one more win- 
ter without general re-treatment. It was somewhat doubtful whether 
this was the best policy, for the section was acting very much as 
section 7 did during its second winter when re-treatment was post- 
poned. There were a great number of breaks, small but prevailing 
generally over most of the section, showing more or less uniform fail- 
ure of the mat. At some points a slight rutting had begun and made 
probable the necessity for very heavy patching and re-treatment 
early in the season. 
Experiment No. 5 — Residual asplialtic petroleum, hot application. — 
The condition of this experiment was comparable with that of expe- 
riment No. 4, although the disintegration did not appear to be quite 
so uniform. Though the surface was wet in all bottoms and poorly 
drained sections, there were larger areas almost intact. On the wet 
sections, the mat showed a tendency to break and form mud and 
considerable patching and it was thought a general re-treatment would 
be necessary the following summer. 
Table 53. — Materials and cost data for surface re-treatment, Rockville Pike, in 1916. 
Item. 
Experi- 
ment No. 1. 
refined coal 
tar (hot). 
Experi- 
ment No. 2 
refined 
water-gas 
tar (cold). 
Experi- 
ment No. 3, 
asplialtic 
petroleum 
(cold). 
Experi- 
ment No. 7, 
asphaltic 
petroleum 
(cold). 
Area treated square yards. 
Quantity of material per square yard: 
Bituminous material gallons . 
Gravel cubic yards. 
Sand do . . . 
Cost per square yard (cents): 
Bituminous material 
Gravel 
Sand 
Cleaning surface 
Hauling materials 
Applying bituminous materials 
Applying sand or gravel 
Supervision 
4,825 
0.83+ 
.011+ 
3.00 
2.93 
.16 
.22 
.22 
Total. 
6.80 
7,475 
0.157 
.012+ 
1.71 
3.27 
.07 
.41 
.29 
.26 
.32 
.33 
12,333 
0.154 
.011 
1.65 
5.95 
11, 148 
0.16 
.01 
2.76 
.05 
.82 
.22 
.30 
.24 
.31 
Table 54. 
-Surface maintenance cost of experiments on Rockville Pike to December 
31, 1916. 
Experiment No. 
Length. 
Area. 
Total cost 
per sq. yd. 
prior to 
Dec. 31, 
1915. 
Surface 
mainte- 
nance 
persq. yd. 
during 1916. 
Total cost 
of surface 
persq. yd. 
to Dec. 31, 
1916. 
Surface 
mainte- 
nance 
per mile for 
year 1916. 
1 
Feet. 
9,060 
4,425 
7,400 
7,100 
6,775 
6,325 
6,689 
8q. yds. 
15,100 
7,375 
12,333 
11,833 
11,292 
10,542 
11. 148 
Cents. 
27.70 
18.89 
20.42 
15.21 
15.32 
27.53 
20.41 
Cents. 
5.26 
6.83 
6.87 
2.41 
2.21 
1.34 
6.87 
Cents. 
32.96 
25.72 
27.29 
17.62 
17.53 
28.87 
27.28 
$462. 88 
2. 
601.04 
3 
604. 56 
4 
211 20 
5 
194 48 
6 
117.92 
7 
604. 56 
