ASTM D6995-21 PDF Download

The ASTM D6995-21 standard aims to provide a rapid field determination of voids in mineral aggregate (VMA) of asphalt mixtures, specifically for quality control (QC) operations at hot mix asphalt (HMA) plants. The standard recognizes that various users require indications of compliance with VMA specifications during production.

Traditionally, determining VMA requires a time-consuming test that involves determining the bulk specific gravity of the aggregate components, which is not suitable for routine QC procedures. In cases where the aggregate source used in the mix has highly variable bulk specific gravity and a reference average bulk specific gravity (Gsb) is used to calculate VMA, incorrect values may occur.

To address these challenges, the standard proposes using the test for maximum specific gravity of the mix (Gmm), which is a routine QC test at HMA plants. The effective specific gravity of the aggregate components (Gse) can be easily calculated from this test. However, Gse does not account for the amount of asphalt absorbed, which is crucial for accurate VMA determination. The ASTM D6995-21 standard provides a procedure to correct Gse using the average absorbed asphalt, allowing for more accurate VMA determination in the field.

It is important to note that the ASTM D6995-21 standard should not be used if the percent water absorption of the total aggregates varies by more than 0.4% in four tests obtained randomly over a 30-day period. The test method also provides equations for calculating VMA based on the asphalt content of the mix and its maximum specific gravity (Gmm). VMA determined using this rapid field method is VMA that has been corrected for aggregate absorption.