Properties of Bitumen

Properties of Bitumen

  1. Adhesion: Bitumen has the  ability  to  adhere  to  a  solid  surface  in  a  fluid  state depending on the nature of the surface. The presence of water on the surface will prevent adhesion.
  2. Resistance to Water: Bitumen is water resistant. Under some conditions water may be absorbed by minute quantities of inorganic salts in the bitumen or filler in it.
  3. Hardness: To measure the hardness of bitumen, the penetration test is conducted,which measures the depth of penetration in tenths of mm. of a weighted needle in bitumen after a given time, at a known temperature. Commonly a weight of 100gm is applied for 5 sec at a temperature of 77 °F. The penetration is a measure of hardness. Typical results  are  10  for  hard  coating  asphalt,  15  to  40  for  roofing asphalt and up to 100 or more for water proofing bitumen.
  4. Viscosity and Flow: The viscous or flow properties of bitumen are of importance both at high  temperature  during  processing  and  application  and  at  low temperature to which bitumen is subjected during service.
  5. Ductility: Ductility test is conducted  to  determine  the  amount  of  bitumen  will stretch at temperature below its softening point.
  6. Softening point: The temperature at  which  a  steel  ball  falls  a  known  distance through the bitumen, when the test assembly is heated at known rate.Usually  the  test  consist  of  (3/8)  inches  diameter  steel  ball,  weight  3.5  gram,which  is  allowed  to  sink  through  out  (5/8)  inches  diameter  (1/4)  inch  the  disc  of  the bitumen in a brass ring. When the whole assembly is heated at a rate of  9 F/min.Typical  values  would  be  240F  for  coating  the  grade  asphalts,  140-220F  for roofing asphalts and 115F for bituminous water to fill material.
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