METHODS OF SAMPLING AND TESTING HIGHWAY MATERIALS 77 
the two clips pulled apart at a uniform rate of speed of 5 centimeters per 
minute. 
PROCEDURE 
5. The asphalt cement or bituminous material to be tested shall be completely 
melted at such a temperature that it will be thoroughly fluid — with ordinary 
paving asphalt cement this is about 160° C. (320° F.). It shall then be strained 
through a 50-mesh sieve, and after a thorough stirring, poured into the mold. 
The mold shall be assembled on a brass plate and so as to prevent the material 
under test from sticking, the surface of the plate and the interior surfaces 
of the side pieces a<i' of the mold shall be thoroughly amalgamated. In filling 
the mold care shall be taken not to disarrange the parts and thus distort the 
briquet. In filling, the material shall be poured in a thin stream back and forth 
from end to end of the mold until it is more than level full. It shall be left 
t< cool to room temperature and then placed in water maintained at 25° C. 
(77° F.) for 30 minutes, after which the excess of bitumen shall be cut off by 
means of a hot putty knife or spatula so that the mold shall be just level full. 
6. The brass plate and mold, with briquet, shall then be placed in the water 
bath and kept at a temperature of 25° C. (77° F.) for at least one and one-half 
hours, when the briquet shall be removed from the plate and the side pieces 
detached. 
777 
w 
m 
Fig. 20. — Ductility mold 
7. The rings at each end of the clip shall then be attached to the pins or 
hooks in the ductility machine and the two clips pulled apart at a uniform rate 
of 5 centimeters per minute (±5 per cent) until the briquet ruptures. The 
distance through which the clips have been pulled to produce rupture shall 
then be measured in centimeters. While the test is being made, the water in 
the tank of the ductility machine shall cover the sample by at least 2.5 centi- 
meters and shall be kept continuously at a temperature within 0.5° C. of 25° C. 
(77° F.). 
A normal test is one in which the material between the two clips pulls out 
to a point or thread until rupture occurs at the point where the thread has 
practically no cross-sectional area. The average of three normal tests shall be 
taken and reported as the ductility of the sample. 
If a normal test is not obtainable on three successive tests, the ductility 
should be reported as being unobtainable under the conditions of the test. 
52. METHOD OF TEST FOR DISTILLATION OF TARS AND 
TAR PRODUCTS 
(A. S. T. M. tentative standard method (5), serial designation D 20-27 T) 
APPARATUS 
1. The apparatus consists of ;1 fiask. condenser tube, shield, receivers, and 
thermometers, as specified in sections 2 to 6. 
