Bitumen Supply

Bitumen is a thermoplastic substance with temperature-dependent stiffness. The temperature-vs-stiffness relationship of bitumen is affected by the crude oil source and refining procedure. 

The Bureau of Indian Standards (BIS) originally developed paving grade bitumen specifications (IS: 73-1950) in 1950 and categorized it based on penetration. The specs were updated in 1962 and 1992. In July 2006, BIS changed IS-73-1992 criteria based on viscosity (Viscosity at 60°C) to improve bitumen quality. These specs specify four grades: VG-10, VG-20, VG-30, and VG-40. Specific gravity, water content, ductility, loss on heating, and Fraass breaking point were eliminated from IS:73-1992 requirements since they have no relationship with the product's quality or performance. 

The higher the grade of viscosity (degree of fluidity), the stiffer the Bitumen. The tests are carried out at 60°C and 135°C, which reflect the temperature of the road surface during summer (hot climate, similar to northern regions of India) and the temperature of the mixing fluid, respectively. The penetration at 25°C (year average pavement temperature) is likewise maintained.  As per Indian standards, bitumen is graded by IS 73:2013. Below table indicates the criteria: