From which layer should samples be obtained when sampling haul unit materials?

From which layer should samples be obtained when sampling haul unit materials?

• A. Outer layer of HMA
• B. Inner layer near the aggregate
• C. Surface moisture layer
• D. Random depth throughout the haul

Answer: (A)

Sampling the haul unit material from the outer layer captures the portion of the load that will actually be laid on the road. In transit, hot mix can segregate as it vibrates and settles, so the material at the surface is the most representative of what will be placed and used for quality control. This outer layer reflects the current mix properties—binder content, aggregate gradation, and overall consistency—better than material that has shifted or cooled toward the interior or bottom. So taking a sample from the outer layer gives a test result that more accurately represents the delivered product.

Sampling the haul unit material from the outer layer captures the portion of the load that will actually be laid on the road. In transit, hot mix can segregate as it vibrates and settles, so the material at the surface is the most representative of what will be placed and used for quality control. This outer layer reflects the current mix properties—binder content, aggregate gradation, and overall consistency—better than material that has shifted or cooled toward the interior or bottom. So taking a sample from the outer layer gives a test result that more accurately represents the delivered product.