12 
BULLETIN 407, U. S. DEPARTMENT OF AGRICULTURE. 
Experiment No. 7. — Bituminous Macadam (Mixing Method); Gneiss with 
Oil- Asphalt X. 
Location: Station 58+45 to station 71+78. 
Length: 1,333 feet. 
Total area: 2,369.8 square yards. 
The crushed gneiss used in the bituminous mixture had the phys- 
ical properties shown in Table 4 and of mechanical analysis shown in 
Table 6. The mechanical analysis of the gneiss chips used on this 
experiment is shown in Table 7. The experiment was otherwise 
exactly similar to experiment No. 4. 
Experiment No. 8. — Bituminous Macadam (Mixing Method); Gneiss with 
Fluxed Native Asphalt A. 
Location: Station 71+78 to station 78+65. 
Total length: 587 feet. 
Total area: 1,221.3 square yards. 
This experiment is exactly similar to experiment No. 7, except 
that fluxed native asphalt A, with properties as shown in Table 8, 
was used instead of the oil-asphalt. 
Experiment No. 9. — Bituminous Gravel Concrete, Pit-Run Gravel, with 
Oil-Asphalt Y. 
Location: Station 78+65 to station 89+50. 
Total length: 1,095 feet. 
Total area: 2,152.1 square yards. 
Table 10. — Typical analyses of oil-asphalt gravel mixtures used in experiment No. 9. 
III. 
Bitumen soluble in CS2 
Mechanical analysis of aggregate: 
Passing 1-inch screen, retained on f -inch screen . . 
Passing f-inch screen, retained on J-inch screen . . 
Passing |-inch screen, retained on J -inch screen. . 
Passing J-inch screen, retained on 10-mesh sieve.. 
Passing 10-mesh sieve, retained on 20-mesh sieve . 
Passing 20-mesh sieve, retained on 30-mesh sieve. 
Passing 30-mesh sieve, retained on 40-mesh sieve. 
Passing 40-mesh sieve, retained on 50-mesh sieve. 
Passing 50-mesh sieve, retained on 80-mesh sieve. 
Passing 80-mesh sieve, retained on 100-mesh sieve 
Passing 100-mesh sieve, retained on 200-mesh siev 
Passing 200-mesh sieve 
Total 
Per cent. 
Per cent. 
Per cent. 
6.4 
6.9 
7.5 
5.7 
6.7 
4.4 
16.9 
11.4 
12.8 
17.1 
19.9 
18.6 
12.6 
12.2 
13.9 
8.5 
6.5 
6.5 
10.3 
10.5 
8.6 
11.0 
11.4 
11.1 
6.5 
8.9 
7.2 
6.2 
6.1 
6.4 
0.8 
0.8 
1.0 
2.2 
2.8 
3.4 
2.2 
2.8 
6.1 
100.0 
100.0 I 100.0 
The gravel base for this experiment had been open to travel several 
weeks and was hard and smooth when surfacing commenced. Wher- 
ever smaU depressions or irregularities had developed they were 
corrected by hand picking and the application of new gravel, which 
was thoroughly rolled. 
The gravel used for the aggregate in the bituminous concrete was 
a uniform dense gravel containing much fine material, as shown by 
