New Jersey

Department of Transportation

Standard Specifications

for Road and Bridge Construction

2007

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:
   
   
   

   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

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

   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.