A prime coat is an application of low viscosity binder material to the surface of a granular base, or the mixing of a low viscosity binder material into the upper portion of a granular base in preparation for an initial asphalt layer or a chip seal. Traditionally, the binder has been an asphalt cutback, but asphalt emulsions and non-asphalt emulsions are gaining acceptance.
Inexpensive insurance to reduce risk of base failures
Can reduce fugitive dust and newer materials are more environmentally friendly
Minimal investment to reduce potential weather and traffic damage to the base
It allows long areas to be primed, which subsequently allows long, continuous applications of surface treatment, thus reducing the number of transverse construction joints. This enhances pavement smoothness and ensuing pavement performance. An actual life extension estimate for this benefit is difficult to determine.
Promotes a strong bond between the base and proceeding asphalt layers
Protecting road base during construction from weather and traffic
Adhesion between the base and next pavement layer
Control dust during construction
Promotes adhesion between base and the initial asphalt course
Protects base from weather and traffic during construction
Increases structural integrity of base
Reduces water movement through base and plugs capillary voids