Which range correctly represents the prime coat application rate for HMA?

• A. 0.05 to 0.15 gal/SY.
• B. 0.5 to 1.5 gal/SY.
• C. 0.01 to 0.03 gal/SY.
• D. 1.0 to 2.0 gal/SY.

Answer: (A)

The prime coat should be a light, uniform film that wets and seals the base to improve adhesion for the subsequent asphalt layer. A rate of 0.05 to 0.15 gal per square yard provides enough coverage to wet the surface and help bind the HMA to the base without creating ponding or oversaturation. If you apply more (such as 0.5 to 1.5 gal/SY or 1.0 to 2.0), the base can become oversaturated, leading to drainage, tracking, or wasted material. If you apply less (0.01 to 0.03), the surface won’t wet adequately, which can compromise bonding and prevent proper asphalt adhesion. So, the 0.05 to 0.15 gal/SY range is the balanced choice for a prime coat on HMA projects.