NJDOT B-3 – Selecting Cores for Maximum Specific Gravity Testing
in Air Voids Determination
Scope. This test method is used to randomly select the core samples on which the maximum specific gravity will be determined according to AASHTO T 209 for use in the calculation of air voids for acceptance of a lot, and the procedure to be followed in the event of a possible failing lot.
Determine the bulk specific gravity according to AASHTO T 166 on each core from the lot.
Randomly select 1 core sample from a 5-core sample lot using a computer-generated random number selection program.
Determine the maximum specific gravity of the randomly selected core according to AASHTO T 209. NOTE: For Recore Lots and Statistical Outlier Lots, do not randomly select a core for maximum specific gravity testing. The entire core lot must be tested for maximum specific gravity.
Determine the air void comparison limits based on air void acceptance limits specified for the mix being tested. Add 0.5 percent to the lower acceptance limit for the lower comparison limit and subtract 0.5 percent from the upper acceptance limit for the upper comparison limit.
Calculate the air void content for the randomly selected core using its maximum specific gravity determined in Step 3 and its bulk specific gravity determined in Step 1.
If the percent air voids for the randomly selected core is outside the comparison limits determined in Step 4, perform maximum specific gravity testing on the remaining cores in the lot. Do not perform Steps 7 to 9.
If the air void content for the randomly selected core is within the comparison limits determined in Step 4, use the maximum specific gravity of the randomly selected core and the individual bulk specific gravities to determine the air void content of the remaining cores in the lot.
If the air void content of any 1 of the cores in the lot as calculated in Step 7 falls outside of the comparison limits as determined in Step 4, perform maximum specific gravity testing on the remaining cores in the lot. Use the individual maximum specific gravities and bulk specific gravities to determine the air void content of each core.
If the air void content of all of the cores in the lot as calculated in Step 7 fall inside of the comparison limits as determined in Step 4, use the air void contents for the individual cores as determined in Step 7.
If the lot has an outlier or is a recore lot, the entire lot must be tested for maximum specific gravity. Calculate air voids using each individual core maximum specific and bulk specific gravity.
Calculations. Calculate the air voids for each core as follows:
Air Voids =
A − B
x 100
A
Where:
A
= Maximum Specific Gravity
B
= Bulk Specific Gravity
Report. Report the air void content for each core to the nearest 0.1 percent.