DUST PREVENTION AND ROAD PRESERVATION, 1915. 7 
The guard rail was built of red-cedar posts with two rails of yellow 
pine. The posts, which had been dipped in asphaltic material, were 
set 4 feet in the ground and sawed off 3 feet 3 inches above the sur- 
face. The 2-inch by 6-inch rails were given two coats of white lead 
and oil. The guard rail is set in each instance 3 feet outside the 
edge of the surfaced road. 
Materials. — The materials used in all surface experiments were 
tested in the laboratories of the office and the results are given in 
Tables 4 to 9, inclusive. 
Table 4. — Physical properties of stone used in surface construction. 
Test. 
Sandstone. 
Gneiss. 
Trap. 
2.50 
2.80 
3.00 
156 
175 
187 
.132 
.28 
.43 
4.8 
3.0 
2.6 
8.3 
13.2 
15.5 
15.5 
18.8 
18.3 
5 
5 
13 
Granite. 
Specific gravity 
Weight per cubic foot pounds 
Water absorbed per cubic foot pounds 
Per cent of wear 
French coefficient of wear 
Hardness 
Toughness 
2.70 
168 
.328 
3.0 
13.3 
18.7 
9 
Table 5. — Mechanical analyses of stone used in the bituminous-macadam by the penetration 
methods. 
Sandstone. 
Gneiss. 
Trap. 
Granite. 
12.0 
55.1 
22.3 
10.6 
9.3 
59.9 
22.0 
7.0 
1.7 
25.1 
47.2 
17.5 
9.6 
.5 
.1 
19.8 
Passing 2-inch, retained on 1^-inch screen 
57.7 
16.7 
5.8 
100.0 
99.9 
109.0 
100.0 
Table 6. — Mechanical analyses of stone and gravel used in the bituminous macadam by 
the mixing method, and the bituminous-concrete. 
Sandstone. 
Gneiss. 
Trap. 
Granite. 
Gravel. 
Passing 2-inch, retained on 1^-inch screen 
Passing l§-inch, retained on lj-mch screen 
Passing l^-inch, retained on 1-inch screen 
Passing 1-inch, retained on f-inch screen 
Passing f-inch, retained on J-inch screen 
Passing 1-inch, retained on J-inch screen 
Passing J-inch screen 
Passing 10-mesh, retained on 20-mesh screen . . . 
Passing 20-mesh, retained on 30-mesh screen . . . 
Passing 30-mesh, retained on 40-mesh screen . . . 
Passing 40-mesh, retained on 50-mesh screen . . . 
Passing 50-mesh, retained on 80-mesh screen . . . 
Passing 80-mesh, retained on 100-mesh screen . . 
Passing 100-mesh, retained on 200-mesh screen . 
Passing 200-mesh screen 
Per cent. 
6.4 
12.1 
38.0 
29.5 
13.2 
.6 
.2 
Per cent. 
Per cent. 
22.4 
6.9 
35.4 
32.8 
24.0 
29.5 
15.0 
25.3 
3.2 
5.1 
.4 
Per cent. 
1.8 
24.4 
44.5 
13.5 
8.3 
6.3 
1.2 
100.0 
100.0 
Per cent. 
100.0 
100.0 
1.3 
8.9 
11.3 
17.2 
U3.3 
4.8 
5.8 
8.3 
7.3 
5.4 
0.5 
2.8 
13.1 
100.0 
Retained on 10- mesh screen. 
