Which properties are typically included in the properties of aggregate?

• A. Particle size, gradation, cleanliness, and toughness.
• B. Color, odor, and gloss.
• C. Thermal conductivity and magnetic properties.
• D. Moisture content and porosity.

Answer: (A)

When evaluating aggregate for asphalt mixtures, the properties typically emphasized are particle size and gradation, cleanliness, and toughness. Particle size and gradation matter because they determine how the aggregate fills space and forms the right amount of voids, which affects mix workability, stability, and how well the asphalt binder can coat and hold the particles together. Cleanliness is crucial because any deleterious material—like clay, shale, or organic matter—can weaken the binder film, reduce strength, and lead to issues such as stripping or premature wear. Toughness describes the aggregate’s ability to resist crushing and fracture under traffic and compaction; a tough aggregate maintains proper interlock and structural integrity over time.

The other options don’t fit because color, odor, and gloss are cosmetic features that don’t influence pavement performance. Thermal conductivity and magnetic properties aren’t relevant to the typical performance criteria for asphalt mixtures. While moisture and porosity can affect some aspects of behavior, they aren’t the primary set of properties used to characterize aggregate quality for standard asphalt applications in the way that size/gradation, cleanliness, and toughness are.