Prime Coat

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For Pavement Condition

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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.  

  1. Inexpensive insurance to reduce risk of base failures
  2. Can reduce fugitive dust and newer materials are more environmentally friendly
  3. Minimal investment to reduce potential weather and traffic damage to the base
  4. 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.
  5. Promotes a strong bond between the base and proceeding asphalt layers

Issues Addressed

  • 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
  • Reduces dust during construction process
  • Reduce the drying rate of compacted base

Common Combinations

  • Prime Coat + HMA on high volume roads
  • Prime Coat + chip seal for low volume roads