To Perform Ductility Test on Bitumen
A ductility test is conducted to determine the amount of bitumen that will stretch at a temperature below its softening point. A briquette having a cross-sectional area of 1 in2 is placed in a tester at 77 °F. Ductility values range from 0 to over 150 depending on the type of bitumen.
The ductility test is a common method used to evaluate the flexibility and elongation properties of bitumen. It measures the distance in centimeters to which a standard briquette of bitumen can be stretched before it breaks. The test provides valuable information about the ability of bitumen to withstand deformation under varying temperature conditions, as well as its suitability for different applications such as road construction. By assessing the ductility of bitumen, engineers can make informed decisions regarding the selection and application of this crucial material in civil engineering projects.
APPARATUS:
- Penetration Apparatus
- Needle
- Container
- Water Bath
- Thermometer for Water Bath
- Stop Watch
The procedure of Ductility Test on Bitumen:
Ductility is the property of bitumen that permits it to undergo great deformation or elongation. 
Ductility is defined as the distance in cm, to which a standard sample or briquette of the material will be elongated without breaking. The dimension of the briquette thus formed is exactly 1 cm square. The bitumen sample is heated and poured into the mold assembly and placed on a plate. These samples with molds are cooled in the air and then in a water bath at 27 °C temperature. The excess bitumen is cut and the surface is leveled using a hot knife. Then the mold with the assembly containing the sample is kept in a water bath of the ductility machine for about 90 minutes. The sides of the molds are removed, the clips are hooked on the machine, and the machine is operated. The distance up to the point of breaking of the thread is the ductility value which is reported in cm. The ductility value gets affected by factors such as pouring temperature, test temperature, rate of pulling, etc. A minimum ductility value of 75 cm has been specified by the BIS.
Step by Step Procedure
Sample Preparation:
A briquette of bitumen is prepared by pouring molten bitumen into a mold and allowing it to cool and solidify. The dimensions of the briquette typically conform to standard specifications.
Conditioning:
The prepared briquette is typically conditioned at a specified temperature for a specific duration to ensure consistency in the test conditions. Conditioning may involve heating or cooling the sample to simulate the temperature conditions it will experience in the field.
Mounting the Briquette:
The conditioned briquette is then mounted vertically between two clamps in a ductility testing machine. The lower end of the briquette is usually immersed in a water bath to maintain a constant temperature during the test.
Stretching the Briquette:
The clamps move apart at a specified speed, stretching the briquette until it breaks. The rate of separation is typically standardized to ensure consistency across different tests.
Recording the Ductility Value:
The distance the briquette stretches before breaking is measured and recorded as the ductility value in centimeters. This value represents the ductility or elongation properties of the bitumen sample.
