Test procedure for Ductility test of bitumen, blown type bitumen and other bituminous products.
TEST STANDARD: IS 1208:1978, Reaffirmed 2009
Ductility is the ability of a material to undergo a visible enduring deformation through elongation (decreasing of cross section area). Ductility is a physical property of bitumen, associated with the ability to be hammered thin or stretched into wire without breaking.
Brass moulds, Constant temperature water bath capable of maintaining temperature within ±10C of the specified temperature, ductility testing machine, thermometer.
Unless otherwise specified, the test shall be conducted at a temperature of 25.0 ± 0.5°C and at a rate of pull of 50.0 ± 2.5 mm/mm. When a low temperature ductility test is desired, the test shall be made at a temperature of 4.0 ±0.5°C and at a rate of pull of 10.0 ± 0.5 mm/min.
Completely melt the bituminous material to be tested to a temperature of 75 to 100°C above the approximately 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 interior surfaces of the sides of the mould with a mixture of equal parts of glycerine and dextrine. In 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 the room temperature for 30 to 40 min, and then place in a water bath maintained at the specified temperature for 30 min after which cut off the excess bitumen by means of a hot, straight-edged putty knife or spatula so that the mould shall be just level full.
Testing for Ductility of bitumen
Place the brass plate and mould with briquette specimen, in the water bath and keep at the specified temperature for about 85 to 95 minutes. Then remove the briquette from the plate, detach the side pieces, and test the briquette immediately. Attach the rings at each end of the clips to the pins or hooks in the resting machine and pull the two clips apart horizontally at a uniform speed as specified until the briquette ruptures. Measure the distance in centimetres through which the clips have been pulled to produce rupture. While the test is being made, make sure that the water in the tank of the testing machine covers the specimen both above and below it by at least 25 mm and is maintained continuously within ±0.5°C of the specified temperature.
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 a minimum.
Report the average of three normal tests as the ductility of the sample, provided the three determinations be within ± 5 percent of their mean value. If the value of three determinations do not lie within ± 5 percent of their mean but the two higher values are within ± 5 percent of their
mean then record the mean of the two higher values as test result.
If the bituminous material comes in contact with the surface of the water or the bottom of the bath, the test shall not be considered normal. Adjust the specific gravity of the water in the bath by the addition of either methyl alcohol or sodium chloride so that the bituminous material does not either come to the surface of the water, or touch the bottom of the bath at any time during the test. If a normal test is not obtainable on three successive tests, report the ductility as being unobtainable under the conditions of test.
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