Viscosity Grade (VG) Table

In the early 1960s, an improved asphalt grading system was introduced, incorporating a scientifically based viscosity test. The test is conducted at two key temperatures: 60 °C ± 0.3 °C, representing the average road surface temperature under sunshine, and 135 °C, reflecting the average temperature of bitumen during asphalt mixing.

In hot climates, bitumen with low penetration and high viscosity (e.g., VG40) is used to prevent deformation under high ambient temperatures. Conversely, in cooler regions, bitumen with high penetration and low viscosity (e.g., VG10) is preferred to minimize cracking under freezing conditions.

Test	VG-10	VG-20	VG-30	VG-40
Dynamic viscosity @60°C (poise)	1000 ± 200	2000 ± 400	3000 ± 600	4000 ± 800
Kinematic Viscosity @135°C (Min, Cst)	250	300	350	400
Penetration, 25°C, 100g 5s, min	80	60	45	35
Flash Point °C	220	220	220	220
Softening Point °C	40	45	47	50
Solubility in Trichloroethylene (min %)	99.0	99.0	99.0	99.0
Test on residue from Thin Film Oven Test	_	_	_	_
Ductility, 25°C, 5cm/min, cm	75	50	40	25
Viscosity Ratio @60°C Max	4.0	4.0	4.0	4.0