What is the purpose of prime coats?

• A. Promote bonding between layers
• B. Improve compaction
• C. Reduce binder viscosity
• D. Prevent slippage, prevent base shifting, protect against weather

Answer: (D)

Prime coats are applied to a prepared base to stabilize the surface and create a bonding-ready interface for the next layer. The main purpose is to prevent slippage and base shifting under traffic and weather, and to protect the base from moisture and weather effects. This keeps the overlay from moving or loosening as conditions fluctuate. While bonding between layers can occur, the essential role of the prime coat is to control movement and moisture defense rather than focusing on compaction or changing binder viscosity.