How is the percent of air voids calculated?

• A. From the maximum weight of the specimen
• B. Using the volume of solid materials only
• C. From the ratio of the bulk specific gravity to the maximum theoretical specific gravity, expressed as a percentage of 100
• D. Using the total void volume in relation to the sample size

Answer: (C)

The percent of air voids in an asphalt mixture is calculated using the ratio of the bulk specific gravity to the maximum theoretical specific gravity, expressed as a percentage of 100. This method is effective because it considers both the volume of the solids within the mixture and the total volume of the mixture, allowing for an accurate representation of the air voids present.

The bulk specific gravity reflects the overall density when the solid particles and the air voids are taken into account, while the maximum theoretical specific gravity represents the density of the mixture if it were completely compacted without any air voids. By comparing these two values, you can derive the amount of air voids as a percentage.

This calculation is crucial because air voids influence the durability, stability, and longevity of the pavement. Ensuring the right amount of air voids leads to optimal performance under traffic loads and varying environmental conditions.