Penetration Grades

The penetration test measures the hardness or softness of bitumen by determining how far a standard loaded needle penetrates the bitumen sample in five seconds at a controlled temperature of 25 °C. Bitumen with higher viscosity resists penetration, resulting in a lower penetration value, while softer bitumen allows deeper needle penetration, producing a higher value.

For example, if the needle penetrates 6 to 7 mm in five seconds, the bitumen is classified as 60/70.

Penetration values are used to classify bitumen according to the climatic conditions where it will be applied. Asphalt binders with high penetration numbers (soft) are suitable for cold climates (e.g., 85/100), whereas binders with low penetration numbers (hard) are preferred for warm climates (e.g., 40/50). Although the penetration depth provides only an approximate indication, it is empirically correlated with asphalt binder performance in the field.

Test	Method	30-40	40-50	60-70	85-100	100-120	200-300
Specific gravity @25/25°C	ASTM D70	1.01-1.06	1.01-1.06	1.01-1.06	1.01-1.05	1.01-1.04	0.99-1.04
Penetration, 25°C, 100g 5s, min	ASTM D5	30-40	40-50	60-70	85-100	100-120	200-300
Softening Point °C	ASTM D-36	55-63	52-60	49-56	45-52	42-49	32 min
Ductility, 25°C, 5cm/min, cm	ASTM D-113	100 min	100 min	100 min	100 min	100 min	100 min
Flash Point °C	ASTM D-92	250 min	250 min	250 min	230 min	250 min	177 min
Solubility in Trichloroethylene (min %)	ASTM D-2042	99.5 min	99.5 min	99.5 min	99.5 min	99.5 min	99.0 min
Spot Test	A.A.S.H.T.T102	Negative	Negative	Negative	Negative	Negative	Negative
Drop in Penetration after Heating %	ASTM D5 & D6	20 max	20 max	20 max	20 max	20 max	37 min
Loss on Heating (%wt)	ASTM D6	0.2 max	0.2 max	0.2 max	0.5 max	0.2 max	1 max