# NJDOT B-6 – Determining Percent of Air Voids in Open-Graded HMA

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

2. Apparatus. Use the following apparatus:

1. Apparatus for determining maximum specific gravity according to AASHTO T 209.
2. Caliper accurate to 0.001 inch.
3. Balance accurate to 0.1 gram and conforming to requirements of AASHTO M 231.

3. Procedure. Perform the following steps:

1. Weigh specimen in air to the nearest 0.1 gram.
2. Measure the height of the specimen at 4 approximately equidistant locations and average. Record the average height to the nearest 0.001 inch.
3. Measure the diameter of the specimen at 4 approximately equidistant locations and average. Record the average diameter to the nearest 0.001 inch.
4. Determine the maximum specific gravity of the specimen as specified in AASHTO T 209.

4. Calculations. Perform the following calculations:

1. Calculate the volume of each specimen based on the average height and diameter and convert to cubic centimeters.
2. Calculate the bulk specific gravity of the specimens using the formula:

3.  Bulk Specific Gravity = Density g/cm3 0.99707 g/cm3
 Where: Density = Mass divided by volume 0.99707 g/cm3 = density of water at 77 °F

4. Determine the maximum specific gravity of the specimen according to AASHTO T 209.
5. Calculate the percent of air voids using the formula:

6.  Percent Air Voids = Maximum Specific Gravity - Bulk Specific Gravity x 100 Maximum Specific Gravity

5. 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