Prime coat typically is application of low viscosity Bitumen over a granular base, preparing it for laying an asphalt mixture on it. A prime coat performs several important functions.

Coats and bonds loose material particles on the surface of the base.

• Hardens or toughens the surface of the base.
• Waterproofs the surface of the base by plugging capillary or interconnected voids Provides adhesion or bond between the base and the asphalt mixture.
• Bitumen emulsions used for Prime Coat are Cationic Slow Setting Emulsion 1 and Cationic Slow Setting Emulsion 2 as per latest MoRTH specifications.