Which statement correctly identifies a property of aggregate?

• A. Color of the aggregate is a primary property.
• B. The aggregate's viscosity is the primary property.
• C. Particle size, gradation, cleanliness, and toughness are typical properties.
• D. Thermal conductivity is a primary specification.

Answer: (C)

In asphalt paving, how aggregate performs depends on how the particles are sized, how clean they are, and how tough they are. Particle size and gradation control how the aggregate packs together, influence the amount of binder required, and affect the stability and durability of the mix. Cleanliness matters because fines or clay can weaken the bond between aggregate and binder and increase moisture susceptibility, leading to durability issues. Toughness reflects the aggregate’s resistance to crushing and wearing under traffic, which is crucial for long-term performance and skid resistance.

Color isn’t used as a performance indicator for aggregate, and viscosity is a property of the asphalt binder, not the aggregate. Thermal conductivity isn’t a primary specification for standard asphalt mixtures. So the statement that lists particle size, gradation, cleanliness, and toughness as typical aggregate properties best reflects what engineers actually evaluate to ensure a good, durable asphalt pavement.