How is the void content in asphalt mixes determined?

Determining the void content in asphalt mixes is crucial for understanding the compaction and performance of the pavement. The correct method involves calculating the difference between the maximum specific gravity and the bulk specific gravity of the asphalt mix.

Maximum specific gravity pertains to the density of the mix when there are no air voids present—this represents the highest possible density. On the other hand, bulk specific gravity accounts for the actual volume of the asphalt, including the air voids. By calculating the difference between these two measurements, you can accurately ascertain the volume of voids within the mix. This information is essential in evaluating the efficiency of the asphalt mix and ensuring that it meets required standards for durability and performance.

Using measurements of aggregate density, visual inspection, or moisture tests does not provide a direct calculation of void content in the same manner or volume accuracy as the difference between maximum and bulk specific gravity does. These methods may inform other aspects of asphalt quality, but they do not specifically quantify the voids in the asphalt mix.