Review of Aggregate and Asphalt Mixture Specific Gravity Measurements and Their Impacts on Asphalt Mix Design Properties and Mix Acceptance.

摘要

Volumetric properties are currently used for design and acceptance of hot-mix asphalt (HMA) mixtures. Vital to the calculation of mixture volumetric properties is the conversion of mass percentages to volume proportions/percentages using specific gravity measurements of the mixture and the aggregates in the mixture. The accuracy and reliability of the specific gravity measurements are therefore fundamental to the business of building quality asphalt pavements. A task group consisting of the authors under the direction of the Federal Highway Administration (FHWA) Asphalt Mix and Construction Expert Task Group was tasked to conduct a critical review of specific gravity measurement methods. The objectives of this review were to summarize problems and issues with current methods, examine possible improvements and/or alternate methods, and identify areas that need further research and development. This review separately examined three specific gravity determinations, namely, the bulk specific gravity of the aggregates (Gsb), the maximum specific gravity of asphalt mixtures (Gmm), and the bulk specific gravity of compacted specimens (Gmb). The review draws upon information from research studies, state transportation departments, AASHTO and ASTM standards, and the AASHTO Materials Reference Laboratory (AMRL). The view of the task group has been that change(s) to the current specific gravity methods may be motivated by one or more of the following three reasons: 1. The change(s) or new method(s) will provide specific gravity results closer to the truth (i.e., greater accuracy), 2. The change(s) or new method(s) will yield more repeatable results (i.e., better precision), and 3. The change(s) or new method(s) will be faster, easier, and/or less expensive.