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

  Bitumen does not suddenly change from solid to liquid state, but as the temperature increase, it gradually becomes soften until it flows readily. The softening point is the temperature at which the substance attains particular degree of softening under specified condition of test. For bitumen it is usually determined by Ring and Ball apparatus. The test is conducted as per IS: 1205.

Aim: To determine the softening point of given paving bitumen as per IS: 1205.

Apparatus: Ring and Ball apparatus, Water bath with stirrer, Thermometer, Glycerin, etc. Steel balls each of 9.5mm and weight of 2.5±0.08gm.

Procedure:

•    Sample material is heated to a temperature between 75° and 100°C above the approximate softening point until it is completely fluid and is poured in heated rings placed on the metal plate.
•  To avoid sticking of the bitumen to metal plate, coating is done to this with a solution of glycerin and dextrin.
•    After cooling the rings in air for 30 minutes, the excess bitumen is trimmed and rings are placed in the support.
•    At this time the temperature of distilled water is kept at 5°C. This temperature IS maintained for 15 minutes after which the balls are placed in position.
•  Then the temperature of water is raised at uniform rate of 5°C per minute with a controlled heating unit, until the bitumen softens and touches the bottom plate by sinking of balls. At least two observations are made. For material whose softening point is above 80°C, glycerin is used for heating medium and the starting temperature is 35°C instead of 5°C.
•  The temperature at the instant when each of the ball and sample touches the bottom plate of support is recorded as softening point value.

Observations: -

 TABLE 4.3: - Observations of Softening Point

Test Property	Trial 1	Trial 2	Trial 3	Mean value
Temperature(0C) at which 1st ball touches the bottom plate	51.20	50.60	50.80	50.87
Temperature (0C) at which 2nd ball touches the bottom plate	50.50	50.80	51.10	50.80
Final Softening Point temperature(0C)	Average Value = 510C

Result: - The Softening Point the given bitumen sample is 51⁰ C. softening point of the bitumen shows the nature of bitumen (Bingham Plastic) at which point it start melting/ softening or at which it attends sufficient degree of softening.