IS 1206 provides viscosity test methods for bitumen — the primary grading parameter for VG (Viscosity Grade) bitumen per IS 73. Absolute viscosity at 60°C determines the VG grade (VG-10, VG-20, VG-30, VG-40). Kinematic viscosity at 135°C indicates mixing/compaction temperature.
Methods for determining viscosity of bitumen by various methods including capillary, rotational, and orifice viscometers.
Key Values
VG-10 absolute viscosity at 60°C800-1200 Poise
VG-30 absolute viscosity at 60°C2400-3600 Poise
VG-40 absolute viscosity at 60°C3200-4800 Poise
Practical Notes
! Viscosity at 60°C determines the VG grade — this is the most important bitumen quality test for Indian roads.
! Viscosity at 135°C indicates mixing temperature — lower viscosity = easier to mix with aggregates.
! VG-30 is the most commonly used grade for Indian highway construction (plains climate).
! VG-40 is specified for heavy traffic and high-temperature regions.