Ductility Test of Bitumen(डामर) (Experimental Procedure, Observations and Result)

     A certain minimum ductility is necessary for a bitumen binder. This is because of the temperature changes in bituminous mixes and the repeated deformations that occur in flexible pavements due to the traffic loads. It is of significant importance that the binders form ductile thin films around the aggregates. The binder material which does not possess sufficient ductility would crack and thus provide previous pavement surface. This is in turn results in damaging effect to the pavement structure. The ductility is expressed as the distance in centimeters to which a standard briquette of bitumen can be stretched before the thread breaks. The test is standardized by the IS: 1208. The test is conducted at 27°±O.5°C and a rate of pull of 50±2.5 mm per minute.

Aim: - To measure the adhesion property of bitumen and its ability to stretch.

Apparatus Required: - Briquette mould, (length – 75mm, distance between clips – 30mm, width at mouth of clips – 20mm, cross section at minimum width – 10mm x 10mm), Ductility machine with water bath and a pulling device at a pre – calibrated  rate, a putty knife, thermometer.

Procedure: -

      

1.   Melt the bituminous test material completely at a temperature of 75⁰ C to 100⁰ C above the approximate softening point until it becomes thoroughly fluid

2.      Strain the fluid through IS Sieve 30.

3.      After stirring the fluid, pour it in the mould assembly and place it on a brass plate

4.      In order to prevent the material under test from sticking, coat the surface of the plate and interior surface of the sides of the mould with mercury or by a mixture of equal parts of glycerin and dextrin

5.      After about 30 – 40 minutes, keep the plate assembly along with the sample in a water bath. Maintain the temperature of the water bath at 27⁰ C for half an hour.

6.      Remove the sample and mould assembly from the water bath and trim the specimen by leveling the surface using a hot knife.

7.      Replace the mould assembly in water bath maintained at 27⁰ C for 80 to 90 minutes

8.      Remove the sides of the moulds

9.      Hook the clips carefully on the machine without causing any initial strain

10.  Adjust the pointer to read zero

11.  Start the machine and pull two clips horizontally at a speed of 50mm per minute

12.  Note the distance at which the bitumen thread of specimen breaks.

13.  Record the observations in the proforma and compute the ductility value report the mean of two observations, rounded to nearest whole number as the “Ductility Value”.

Observations: -

    TABLE 4.2: - Observations of Ductility Value

Test Property	Trial 1	Trial 2	Trial 3	Mean value
Ductility Value	43cm	42cm	40cm	42m

Result: - The Ductility Value of the given sample is 42cm.