**Scope**. This test method is used to determine the percent of air voids in compacted open-graded HMA specimens.

**Apparatus**. Use the following apparatus:- Apparatus for determining maximum specific gravity according to AASHTO T 209.
- Caliper accurate to 0.001 inch.
- Balance accurate to 0.1 gram and conforming to requirements of AASHTO M 231.

**Procedure**. Perform the following steps:- Weigh specimen in air to the nearest 0.1 gram.
- Measure the height of the specimen at 4 approximately equidistant locations and average. Record the average height to the nearest 0.001 inch.
- Measure the diameter of the specimen at 4 approximately equidistant locations and average. Record the average diameter to the nearest 0.001 inch.
- Determine the maximum specific gravity of the specimen as specified in AASHTO T 209.

**Calculations**. Perform the following calculations:- Calculate the volume of each specimen based on the average height and diameter and convert to cubic centimeters.
- Calculate the bulk specific gravity of the specimens using the formula:
- Determine the maximum specific gravity of the specimen according to AASHTO T 209.
- Calculate the percent of air voids using the formula:

Bulk Specific Gravity = Density g/cm^{3}0.99707 g/cm^{3}Where: Density= Mass divided by volume 0.99707 g/cm ^{3}= density of water at 77 °F

Percent Air Voids = Maximum Specific Gravity - Bulk Specific Gravityx 100 Maximum Specific Gravity

**Report**. Report the percent air voids of each specimen and the average percent air voids of the specimens to the nearest 0.1 percent.

Last Document Correction:

December 14, 2007