Thursday, October 24, 2013

Rings and Balls Apparatus (Softening point test of Bitumen)

Softening point of Bitumen: It is the minimum temperature at which bitumen get soft.
It is important to find the softening point of Bitumen because bitumen can be easily applied on the road surface when it is soft and we have to use the fuel and fire to soften the available bitumen. Softening point tells us about the amount of fuel/energy that will be needed to soft it before applying on the road surface. Softening point of bitumen must not be below the average day temperature and it should also not be very much higher, because that will require much energy and fuel to soft it before applying on the road.
  • Aim: To find out the softening point of the given bitumen sample.
  • Apparatus: 
  1. Rings and Balls Apparatus
  2. Heating arrangement
  3. Thermometer.

Rings and Balls Apparatus
Ring and Balls apparatus contain metallic rings and steel balls and a base metallic plate, encased inside a jar. This whole arrangement is immersed in the water inside the jar, so as to gradually and uniformly raise the temperature by heating with the help of the heating arrangement.

  • Theory: Theory of this test is that as the temperature rises, bitumen starts to soft, and attains certain fluidity sufficient enough for this to be applied on the road surface. The temperature plays an important role in the hardness or the softness of the bitumen so we have to find out the minimum temperature at which bitumen attains sufficient fluidity.

  • Procedure: 
  1. Fill the top surface of the metallic rings with the given bitumen, forming a sheet like surface.
  2.  At lower temperature surface of the bitumen will be hard enough to support the steel balls on the top surface, so put the steel balls on it just above the rings. 
  3. When the whole arrangement immersed in the water is heated at the specified standard rate, the bitumen will start to soft and the steel balls under their own weight, will start to sink on the bitumen surface. 
  4. Steel balls will sink in a way that they will drag the bitumen along with them in the downward direction, bitumen still supporting them but elongating at the same time. 
  5. At certain rise of temperature, steel balls will touch the surface of the base plates below and that temperature is noted.  Thermometer must be put in through the slot initially to take the readings.

Result: The reading on the thermometer gives the softening point of the bitumen.

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