Types and grades of bitumen used in road surfacing

Bitumen is graded based on its physical properties like viscosity and penetration depth to ensure its suitability for different climatic conditions and traffic loads. The main types used in road surfacing are:

1. Viscosity Graded Bitumen (Paving Grade): This is the most widely used type in modern road construction, graded based on its viscosity (resistance to flow) at 60°C. The common grades are:
   • VG-10: Has the lowest viscosity. Used in very cold climates for spraying applications and surface dressing.
   • VG-20: Used for paving in cold climates and high-altitude regions.
   • VG-30: The most common grade, used for standard paving applications under normal traffic and temperature conditions. It's a reliable choice for most highway construction in India.
   • VG-40: Has higher viscosity. Used in areas with high traffic loads and elevated temperatures, such as intersections and toll plazas, to resist rutting.
2. Polymer Modified Bitumen (PMB): This is bitumen whose properties have been enhanced by adding polymers like SBS (Styrene-Butadiene-Styrene). PMB offers superior performance against rutting, cracking, and water damage, making it ideal for highways with very heavy traffic.
3. Bitumen Emulsion: This is a mix of fine bitumen droplets suspended in water with an emulsifying agent. It's an eco-friendly, cold-application binder used for tack coats, surface dressing, and patching work.
4. Cutback Bitumen: This is bitumen with its viscosity reduced by adding a petroleum solvent like kerosene.