IS 217 provides the specifications for cutback bitumen, which is bitumen whose viscosity is temporarily reduced by the addition of volatile solvents for application at lower temperatures. The standard outlines the physical and chemical requirements for Rapid Curing (RC), Medium Curing (MC), and Slow Curing (SC) grades commonly historically used for prime coats, tack coats, and surface dressing.
Specifies requirements for different grades of cutback bitumen used primarily for prime coats, tack coats, and surface dressing in road construction.
Quick Reference Values
Kinematic Viscosity Test Temperature60°C
Standard Viscosity Grades70, 250, 800, 3000 cSt
Maximum Water Content0.2 percent by mass
Penetration Test Temperature for Residue25°C
Practical Notes
The use of cutback bitumen is largely discouraged and being phased out globally in favor of bitumen emulsions (IS 8887) due to environmental concerns, high VOC emissions, and health hazards.
Cutback bitumens pose a severe fire hazard. Engineers must strictly verify the flash point and ensure heating is done well below this limit.
The curing rate depends on the type of solvent used: naphtha/gasoline for RC, kerosene for MC, and heavy oils for SC.