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Transportation Engineering Lab Experiments

Softening Point Test of Bituminous Material Experiment


To determine the softening point of the given bitumen sample.

IS Standards used:IS 1203 - 1978

Need and scope:The Softening Point of bitumen or tar is the temperature at which the substance attains particular degree of softening. As per IS: 334-2002, it is the temperature in°C at which a standard ball passes through a sample of bitumen in a mould and falls through a height of 2.5 cm, when heated under water or glycerine at specified conditions of test. The binder should have sufficient fluidity before its applications in road uses. The determination of softening point helps to know the temperature up to which a bituminous binder should be heated for various road use applications. Softening point is determined by ring and ball apparatus.

Apparatus Required:

  1. Ring & Ball apparatus
  2. Water bath
  3. Stirrer
  4. Thermometer
  5. Beaker
  6. Heating device etc.

Experimental procedure:

  1. Preparation of test sample: Heat the material to a temperature between 75-100°C above its softening point; stir until it is completely fluid and free from air bubbles and water. If necessary, filter it through IS sieve 30. Place the rings on a metal plate which has been coated with a mixture of equal parts of glycerine and dextrin. After cooling for 30 minutes in air, level the material in the ring by removing the excess material with a warmed, sharp knife.
  2. Assemble the apparatus with the rings, thermometer and ball guides in position.
  3. Fill the bath with distilled water to a height of 50mm above the upper surface of the rings. The starting temperature should be 5 °C.
  4. Apply heat to the bath and stir the liquid so that the temperature rises at a uniform rate of 5 +/- 0.5 °C per minute.
  5. As the temperature increases the bituminous material softens and the balls sink through the rings carrying a portion of the material with it.
  6. Note the temperature when any of the steel balls with bituminous coating touches the bottom plate.

Observations and Calculation:

Bitumen Sample Identification of Sample (Grade of bitumen) Ball 1 Temperature (0C) Ball 2 Temperature (0C) Average Temperature (0C)

The Softening Point Temperatures of the given samples of Bitumen are: -

(a) Sample A =

(b) Sample B =

General remarks:

Viva Questions:

  1. What is the importance of determination of softening point in road construction operations?
  2. What are the criteria of selection of medium used for heating the specimen?
  3. What are the factors, which may affect the ring and ball test results?
  4. What will happen to softening point if: a. Aluminium balls are used in place of steel balls b. The distance between the rings and the bottom plate is increased?