softening point test

Softening Point Test of Bitumen


It is a type of test done on an important highway construction material i.e. bitumen. Softening Point test of bitumen is done to determine the consistency of bitumen. This test gives an idea of the temperature at which the bitumen attain certain viscosity.

Softening point is defined as the temperature at which bitumen softens beyond some arbitrary softness i.e. bitumen softens and sags down about 25mm below the weight of steel ball.


Apparatus Required:

 A brass shouldered ring
 A steel ball
 Ball centring guide
 Ring holder
 Brass pouring plate
 Water bath and thermometers



Procedures in Softening Point Test of Bitumen:

1. The sample is first heated with continuous stirring until it becomes sufficiently fluid to pour.

2. A slight excess of the heated sample is poured into two rings that have already been preheated to approximately the pouring temperature.

3. The apparatus is then assembled with the rings, thermometer, ball centring guide, and filled with boiled water up to a depth not less than 102mm and not more than 108mm.

4. The water bath temperature is then maintained at about 15 degree Celsius for about 15 minutes.

5. Then, balls previously adjusted to the temperature are placed on the ball centring guide.

6. The arrangement is heated at the rate of 5 degree Celsius per minute. It must be noted that the rise in temperature is uniform.

7. The maximum permissible variation of any 1mm period after the first 3mm shall be +0.5 degree or -0.5 degree. All the tests in which the rate of rising doesn’t fall within these limits are rejected.

8. For each ring and ball, the thermometer reading is noted at the instant when the specimen surrounding the ball touches the base plate.

softening point test


Observations and Calculations

The temperature when the ball touches the bottom, °C12





The softening point of bitumen/tar =………….. °C



Civil Nepal International Team.

How useful was this post?

Click on a star to rate it!

Average rating 0 / 5. Vote count: 0

No votes so far! Be the first to rate this post.

As you found this post useful...

Share this on social media!

We are sorry that this post was not useful for you!

Let us improve this post!

Tell us how we can improve this post?

Leave a Reply

Your email address will not be published. Required fields are marked *