AIM
To determine the ductility of distillation residue of cutback
bitumen, blown type bitumen and other bituminous products as
per IS: 1208 - 1978.
PRINCIPLE
The ductility of a bituminous material is measured by the
distance in cm to which it will elongate before breaking when a
standard briquette specimen of the material is pulled apart at a
specified speed and a specified temperature.
APPARATUS
TESTING MACHINE
i) Standard mould
ii) Water bath
iii) Testing machine
iv) Thermometer - Range 0 to 44oC, Graduation 0.2oC
PROCEDURE
i) Completely melt the bituminous material to be tested by
heating it to a temperature of 75 to 100oC above the
approximate softening point until it becomes thoroughly fluid.
Assemble the mould on a brass plate and in order to prevent
the material under test from sticking, thoroughly coat the
surface of the plate and the interior surfaces of the sides of
the mould with a mixture of equal parts of glycerine and
dextrin. While filling, pour the material in a thin stream back
and forth from end to end of the mould until it is more than
level full. Leave it to cool at room temperature for 30 to 40
minutes and then place it in a water bath maintained at the
specified temperature for 30 minutes, after which cut off the
excess bitumen by means of a hot, straight-edged putty
knife or spatula, so that the mould is just level full.
ii) Place the brass plate and mould with briquette specimen in
the water bath and keep it at the specified temperature for
about 85 to 95 minutes. Remove the briquette from the
plate, detach the side pieces and the briquette immediately.
iii) Attach the rings at each end of the two clips to the pins or
hooks in the testing machine and pull the two clips apart
horizontally at a uniform speed, as specified, until the
briquette ruptures. Measure the distance in cm through
which the clips have been pulled to produce rupture. While
the test is being done, make sure that the water in the tank
of the testing machine covers the specimen both above and
below by at least 25mm and the temperature is maintained
continuously within ± 0.5oC of the specified temperature.
REPORTING OF RESULTS
A normal test is one in which the material between the two clips
pulls out to a point or to a thread and rupture occurs where the
cross-sectional area is minimum. Report the average of three
normal tests as the ductility of the sample, provided the three
determinations be within ± 0.5 percent of their mean value.
If the values of the three determinations do not lie within ± 0.5
percent of their mean, but the two higher values are within ± 0.5
percent of their mean, then record the mean of the two higher
values as the test result.