DUST PREVENTION AND ROAD PRESERVATION, 1915. 
17 
215 + 28 to 219 + 00 it was necessary to remove entirely the old mac- 
adam base to correct the profile, and a new base was built of "1J- 
inch" granite spread to a loose depth of 6 inches and rolled with a 
10-ton roller until compacted, without the addition of any binder. 
The surface was exactly similar to that in experiment No. 16, 
except that the stone was granite, with physical properties and 
mechanical analyses as shown in Tables 4 and 6, respectively. The 
mechanical analyses of the chips used are shown in Table No. 7. The 
percentage of the weight of asphalt to the total weight of asphalt and 
stone was 6.73. The mixing was done near station 215 + 00. 
Experiment No. 20. — Bituminous Macadam (Mixing Method). Granite 
with Fluxed Native Asphalt A. 
Location: Station 225+10 to station 235+50. 
Total length: 1,040 feet. 
Total area: 1,866.7 square yards. 
The base of this experiment was an old trap-rock water-bound 
macadam road, which was scarified and reshaped. Considerable 
extra stone ( u lJ-inch" granite) was added from stations 229 + 00 
to 234 + 00 to supplement weak places in the old macadam. 
The surface was laid exactly as in experiment No. 19, except that 
fluxed native asphalt of the analysis shown in Table 8 was used 
instead of oil-asphalt. 
SUMMARY OF COST DATA FOR ENTIRE PROJECT. 
The cost data for the experiments described above are presented in 
the tables which follow, Nos. 13 to 23o 
Table 13. — Cost data for subgrade. 
[Subgrade, stations —(1+61) to 235+50.] 
Items. 
Clearing 
and 
grubbing. 
Excava- 
tion. 
Shaping. 
Scarifying 
and 
reshaping. 
Rolling. 
Subgrade, 
complete. 
Quantity 
Acres. 
5.0000 
Cubic yards. 
28,575 
Square yds. 
45,835 
Square yds. 
11,378 
Square yds. 
57,213 
Square yds. 
i 42,111 
Labor 
$125.57 
$8,237.71 
287.05 
$3,035.83 
$348. 17 
6.80 
$72. 74 
30.55 
$11,820.02 
324.40 
Materials 
Total 
125.57 
8,524.76 
3,035.83 
354.97 
103. 29 
12, 144. 42 
Unit cost 
Acre. 
$25. 114 
.22 
Cubic yard. 
$0.2983 
15.24 
Square yard. 
$0.0662 
5.42 
Square yard. 
$0.0312 
.64 
Square yard. 
$0.0018 
.19 
Square yard. 
$0. 2884 
Per cent of total cost 
21.71 
52086°— Bull. 407- 
1 Does not include shoulders. 
-16 3 
