DUST PREVENTION AND ROAD PRESERVATION, 1916. 
21 
Fairfax County. This road had been reconstructed and surfaced 
with gravel only a few months before the experimental surface treat- 
ment was undertaken. The principal features of the road may be 
described briefly as follows: 
Total width of road 24 feet. 
Total width of gravel surface 16 feet. 
Compacted depth of gravel (2 courses having respective depths of 
3 and 5 inches) 8 inches. 
Crown of road £ inch to 1 foot. 
Maximum grade 5 per cent. 
Drainage conditions Favorable. 
Gravel for use in the original construction was obtained from the 
county pit, located about 500 feet south of station 0+00 at Gum 
Spring, and the Walker pit, located about 100 feet east of station 
92+50. The gravel from the county pit was used from station 
0+00 to station 48+00, while that from the Walker pit was used 
from station 48+00 to the south end of the road. The mechanical 
analysis for the material from each pit is shown in Tables 25 and 26. 
Table 25.— Mechanical analysis of sand-clay gravel from Walker pit, Fairfax County, Va. 
Totals retained. 
Passing— 
Retained on— 
Per cent 
of 
sample. 
Per cent 
of coarse 
aggre- 
gate. 
Per cent 
of fine 
aggre- 
gate. 
Per cent. 
6.5 
15.9 
30.4 
40.6 
45.5 
59.2 
77.2 
85.3 
88.4 
88.9 
89.6 
1-inch screen 
f-inch screen 
£-inch screen 
\ -inch screen 
10-mesh sieve 
20-mesh sieve 
30-mesh sieve 
40-mesh sieve 
50-mesh sieve 
80-mesh sieve 
100-mesh sieve . . 
200-mesh sieve . . 
f-inch screen 
J-inch screen 
£-inch screen 
10-mesh sieve 
20-mesh sieve 
30-mesh sieve 
40-mesh sieve 
50-mesh sieve 
80-mesh sieve 
100-mesh sieve . . 
200-mesh sieve . . 
6.5 
9.4 
14.5 
10.2 
4.9 
13.7 
18.0 
8.1 
3.1 
.5 
.7 
10.4 
21.4 
30.9 
47.7 
£-inch screen 
14.7 
7.0 
30-mesh sieve 
19.7 
25.9 
50-mesh sieve 
11.6 
4.5 
100-mesh sieve 
.7 
1 
14.9 
100.0 
100.0 
100.0 
Table 26. — Mechanical analysis of sand-clay gravel from county pit. 
Totals retained. 
Passing— 
Retained on— 
Per cent 
of 
sample. 
Per cent 
of coarse 
aggre- 
gate. 
Per cent 
of fine 
aggre- 
gate. 
1-inch screen 
Per cent. 
4.8 
15.6 
34.6 
55.9 
69.9 
74.5 
80.3 
86.5 
88.6 
91.1 
92.0 
93.7 
lj-inch screen... 
1-inch screen 
f-inch screen 
Hnch screen 
1-inch screen 
10-mesh sieve 
20-mesh sieve 
30-mesh sieve 
40-mesh sieve 
50-mesh sieve 
80-mesh sieve 
100-mesh sieve . . 
200-mesh sieve . . 
1-inch screen 
f-inch screen 
|-inch screen 
J-inch screen 
10-mesh sieve 
20-mesh sieve 
30-mesh sieve 
40-mesh sieve 
50-mesh sieve 
80-mesh sieve 
100-mesh sieve . . 
200-mesh sieve . . 
4.8 
10.8 
19.0 
21.3 
14.0 
4.6 
5.8 
6.2 
2.1 
2.5 
.9 
1.3 
6.7 
8.6 
19.3 
34.0 
38.1 
f-inch screen 
^-ineh screen 
£-inch screen 
10-mesh sieve 
31.7 
10.4 
13.2 
14.1 
4.8 
5.7 
2.0 
2.9 
15.2 
20-mesh sieve 
30-mesh sieve 
40-mesh sieve 
50-mesh sieve 
80-mesh sieve 
100-mesh sieve 
200-mesh sieve 
100.0 
100.0 
100.0 
