By Srinivas Chowdary Sunkara // petrobazaar.com
In India, Bitumen grading is practised on the basis of penetration test, which is conducted at a temperature of 25 degrees C, and 60/70 penetration grade bitumen is widely used. A penetration of 0.6 to 0.7 mm indicates 60/70 penetration grade bitumen. The empirical penetration test was developed over 100 years ago in which a standard penetration needle loaded with 100 grams is allowed to penetrate the bitumen for five seconds. the penetration is measured in mm and it indicates the relative hardness of the bitumen. Higher the penetration, softer is the bitumen. Later on, Viscosity test was implemented in U.S. some 30 years ago. The viscosity of the bitumen is measured in poises at 60 degrees C using a simple Viscometer to ensure the consistency of the paving bitumen at high temperature (such as 60 degrees C) .