What is ductility of the bitumen?
The ductility of the bituminous binder is expressed as the distance in centimeters at a standard semi-solid briquette will elongate before breaking. In this article we will discuss full procedure for the Ductility test of bitumen.
Ductile material is one that elongates when in tension. The test is carried out in a standard ductility test apparatus.
Specified conditions for ductility lest
Mould-8 shaped Briquette of standard dimension.
Temperature:- 27 degree Celsius.
Pull rate- 50 mm/minute
Starting minimum width (neck width) 10 mm X 10 mm
Apparatus required for Ductility test of bitumen
- 8- Shaped Briquette mould
- Heating Oven
- Heat measuring thermometer
- Steel Beaker
- Water bath container
- Bitumen Sample testing machine
Size of Briquette mould
Total length of briquette mould is 75 mm ± 0.5 mm
Distance between two clips is 30 mm ± 0.3 mm
Thickness of clip is 10 mm ± 0.1 mm
Width of clip is 20 mm ± 0.2 mm
Procedure for Ductility test of bitumen
To perform the ductility test of bitumen we require three Briquette mold (8-shaped mold) of standers size. (as given above)
After that the sample of bitumen is heated up to 75 to 100 degrees centigrade nearly to the softening point.
An equal part of glycerin and dextrine is mixed in equal part and apply at the external part of the Briquette mold.
This is done to prevent the bitumen to stick with Briquette mold while testing ductility of bitumen.
After that pour the bitumen into all three Briquette mould and let it cool till 30 minutes to 40 minutes.
Now, take this sample along with Briquette mould and put it to water bath maintained at 27 degree Celsius till about half an hour.
Now remove the sample of bitumen and put into ductility testing mahine.
Now note down the initial reading of the machine and switch on the machine with an appropriate pull rate of 50 mm/minute .of separation.
Now, observe the distance of elongation of bitumen at time of breaking of samble.
Note down the value for elongation of sample.
And hence ductility value is calculated with the help of initial and final reading of machine. Like,
Initial reading (a) :- let 0
Final Reading (b) :- let 74.3
Ductility (a-b) :- 74.3
This value is taken for all the sample of bitumen.
Significance of Ductility test of bitumen
The ductility value is the measure of adhesiveness and elasticity bitumen. Its range varying from 5-100 cm.
The most appropriate value is 50 cm.
Ductile bitumen forms a thin ductile film around aggregate does not crack under lower temperature. Brittle between then does not form ductile films does crack under lower adverse temperature.
Bond in brittle bitumen is not completely reversible. Bitumen’s possession of high ductility is also usually highly susceptible t temperate change. While low ones are not.
Ductility requirement for paving Bitumen
|2.||S – 55||75|
|4.||S – 90||75|
Precaution for testing bitumen
- Briquette mould should not be fractured at any side.
- The sample should not be heated too much.
- The temperature of the water bath should not be more than 27 degree Celsius.
- The pull rate of the machine should not be higher than 50 mm/ minute.
- Initial and final reading should be noted carefully.