Earlier, we had discussed the penetration test of bitumen to find out the consistency or hardness, grade the bitumen for the construction work. In this, we are going to test the softening point of bitumen.
The softening point test used to determine the melting point in which the bitumen reaches the viscosity (semi-liquid form).
A laboratory test used to find out the bitumen viscosity (semi-liquid form) at a certain degree of temperature is called a softening point test. It is also named ring & ball test because it is performed using a steel ring and a ball.
The bitumen will not be suitable for road work if it starts to melt at atmospheric climate conditions. So the softening point test is conducted to ensure that the bitumen can withstand the hot weather conditions.
According to the requirement of the usage, the bitumen can be classified and used for pavement construction.
To determine the softening point of the bitumen specimen as per the IS code 1205.
Now the bitumen sample is ready to start the procedure of softening point test.
Take the reading through the thermometer when the steel balls fall on the surface of the bottom plate. The average temperature is the softening point of the bitumen.
Softening Point of Bitumen = Degree Celsius.
The allowable difference between the two readings is 1 °c.
Bitumen/Tar | Ball 1 | Ball 2 |
Temperature @ ball touches the bottom | ||
Average Penetration value |
The recommended softening point bitumen as per IS code 73 have been listed below.
Paving Grades | Softening Point |
VG 10 | 40 |
VG 20 | 45 |
VG 30 | 47 |
VG 40 | 50 |
Video Courtesy – NCTEL
Happy Learning 🙂
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