TRB’s National Cooperative Highway Research Program (NCHRP) Research Results Digest 369: AASHTO T 209: Effect of Agitation Equipment Type on Theoretical Maximum Specific Gravity Values evaluates the effect of using various devices and methods on measured values of theoretical maximum specific gravity (Gmm) used to determine the air void content and the in-place density of hot-mix asphalt (HMA) as described by the American Association of State Highway and Transportation Officials (AASHTO) T 209, Theoretical Maximum Specific Gravity and Density of Bituminous Paving Mixtures.
According to the report, AASHTO T 209 describes a test method for determination of the theoretical maximum specific gravity (Gmm) and density of uncompacted HMA. The Gmm and the density of HMA are fundamental properties whose values are influenced by the composition of the HMA mixtures in terms of types and amounts of aggregates and asphalt materials.
Gmm is used to calculate percent air voids in compacted HMA and to provide target values for the compaction of HMA. Gmm also is essential when calculating the amount of asphalt binder absorbed by the internal porosity of the individual aggregate particles in HMA.