The Penetration is the consistency of a bituminous material expressed as the distance in tenths of a millimetre that a standard needle vertically penetrates a sample of the material under known conditions of loading, time, and temperature.
The penetration is measured with a penetrometer by means of which a standard needle is applied to the sample under specific conditions.
The penetration test is used as a measure of consistency. Higher values of penetration indicate softer consistency. The value of penetration obtained is also used to classify the bitume in a range of penetration grade.