42 BULLETIN 407, U. S. DEPARTMENT OF AGRICULTURE. 
with, wood fuel; a concrete mixer equipped with revolving blades 
and operated by a 4-horsepower gasoline motor; dump wagons; a 
6-ton steam tandem roller; 2 hand rollers; corrugated culvert pipe 
for heating sand; hand pouring pots; and hand tools. 
Experiment No. 1. — Limestone, Residual Asphaltic Petroleum, Penetration 
Method. 
Location: Station 201+15 to station 212+92. 
Length: 1,177 feet. 
Area: 1,834 square yards. 
Details. — Upon the rolled subgrade, partly of sand-clay and partly 
of sand, a foundation course of pit-run limestone was spread and 
rolled until firm. The depth of the foundation course was 5 inches, 
loose measurement. Upon this a wearing course, 2 inches thick by 
loose measurement of screened rock was spread and rolled with 
the 6-ton tandem roller sufficiently to smooth and shape the course 
but not to break up the fragments. Upon the wearing course was 
applied approximately 1 gallon per square yard of the residual 
asphaltic petroleum, analysis of which is given in Table 43. The 
petroleum was heated in the large sirup kettle at the roadside 
and was spread by means of hand-pouring pots. In applying the 
hot oil care was taken to coat the rock as uniformly and completely 
as was possible. The oil was immediately covered with sand and the 
surface was then rolled until firm. As the oil was forced upward 
through the sand by rolling, more sand was distributed to absorb it. 
Shoulders, 2 feet wide and 6 inches thick, of pit-run rock or screen- 
ings, were constructed on each side of the 14-foot oil-treated road. 
Materials and cost data for this experiment are given in Table 46. 
Table 43. — Analysis of residual asphaltic petroleum used in experiment No. 1. 
Specific gravity 25°/25° C 0. 985 
Viscosity, Engler, 100° C, 50 cc, specific 15. 6 
Float test at 32° C. (time) V 48" 
Float test at 50° C . (time) (K 40" 
Loss, 163° C, 5 hours, 20 grams, per cent 1. 64 
Float test of residue • at 32° C. (time) 6' 30" 
Float test of residue at 50° C. (time) 1' 30"' 
Per cent of total bitumen insoluble in 86° B. naphtha 17. 98 
Fixed carbon, per cent 10. 04 
Soluble in CS 2 (total bitumen), per cent 99. 93 
Organic matter insoluble, per cent 07 
Inorganic matter insoluble, per cent 00 
Total, per cent 100. 00 
i Very viscous, sticky fluid. 
