How are air voids calculated in asphalt pavement?

The calculation of air voids in asphalt pavement is determined using the formula that accurately reflects the relationship between the maximum theoretical specific gravity (Gmm) and the bulk specific gravity (Gmb) of the asphalt mixture.

In this context, Gmm represents the maximum specific gravity of the asphalt mix, which indicates the highest density the mixture can achieve without any air voids present. Conversely, Gmb is the bulk specific gravity, which accounts for the actual volume of the asphalt mix, including the air voids within it.

The formula for calculating air voids is derived from the difference between these two values, reflecting the proportion of voids in the compacted mixture. Specifically, it takes the difference between Gmm and Gmb, divides that by Gmm, and then multiplies by 100 to express it as a percentage. This way, the formula effectively shows how much of the total volume is composed of air voids, helping assess the quality and performance of the asphalt mix.

The other options do not correctly represent the relationship needed for calculating air voids in asphalt pavements, leading to inaccuracies in the determination of void content. Understanding this correct calculation is crucial for ensuring optimal pavement performance and longevity.