Development of Acceptance Criteria of Compacted Hot Mixture Asphalt Bulk Specific Gravity Based on Vacuum Sealed Specimens

A number of test methods are available to measure the bulk specific gravity of compacted hot mix asphalt (HMA). The most commonly used test methods (ASTM D 2726 and AASHTO T 166) were designed for use with specimens that do not contain open or interconnected air voids. With increased traffic loading, coarse and open-graded asphalt mixtures have become more common to improve in-situ performance. These mixtures are known for open or interconnected air voids. The current methods for addressing coarse and open-graded mixtures (ASTM D 1188 and AASHTO T 275) can lead to erroneous bulk specific gravity measurements and can prevent specimens from further testing. Thus a vacuum sealing method (ASTM D 6752) was developed to address asphalt mixtures that contain interconnected or open air voids. In an evaluation of the new method for determining bulk specific gravity it has been found that a criterion test would help to identify when the new test method would be most suitable. The research objective is to define the point at which the vacuum sealing method (ASTM D 6752) more accurately predicts the bulk specific gravity of an HMA as compared to the conventional method (ASTM D 2726 and AASHTO T 166). For this reason permeability was the fundamental property that was investigated. Permeability is a measure of the asphalt mixtures ability to transmit fluid, which in turn represents the mixtures connectivity of void space. A laboratory method for measurement of permeability of hot mix asphalt (ASTM PS 129-01) has been hypothesized as a criterion test for method selection in determining the bulk specific gravity of hot mix asphalt.