What does the term “voids in mineral aggregate” (VMA) refer to in HMA?

The term “voids in mineral aggregate” (VMA) refers specifically to the air spaces between particles in a compacted asphalt mix, represented as a percentage of the total volume. VMA is a critical parameter in determining the properties of hot mix asphalt (HMA), influencing workability, durability, and the overall performance of the pavement.

In essence, VMA indicates how much void space is present in a given amount of aggregate, which is essential for ensuring that there is sufficient asphalt binder to fill these voids for effective adhesion and stability. If the VMA is too low, it may suggest that there is insufficient binder to coat the aggregate particles, which can lead to performance issues such as raveling or stripping.

In contrast, the other options address aspects that are related to, but not directly defining, VMA. The amount of asphalt binder indicates its contribution to the mix but does not specifically refer to voids. Similarly, specific gravity relates to the density of materials, while the total volume of aggregates does not account for the voids present. Thus, the correct association of VMA with the air spaces provides a clearer understanding of its role in HMA.