What term refers to spaces in the pavement not filled by aggregate or asphalt?

• A. Porosity
• B. Pore spaces
• C. Air voids
• D. Void spaces

Answer: (C)

Air voids refer to the spaces in the compacted asphalt mix that are not filled by aggregate or asphalt binder. These are the air-filled pores left after compaction and are the precise measure engineers use to describe how much empty space remains in the mix. Their level matters for performance: too many air voids mean less binder per volume, making the mix more permeable and prone to oxidation and cracking; too few air voids can cause binder squeeze-out, flushing, and reduced durability. Porosity is a broader term for all void space in a material and isn’t the specific measure used for asphalt mixes, while “pore spaces” or “void spaces” are generic phrases that don’t pinpoint the air-filled pores the specification targets.