Geometrical Evaluation and Experimental Verification to Determine Representative Volume Elements of Heterogeneous Asphalt Mixtures

This paper presents an experimental verification of geometrically defined representative volume elements (RVEs) of heterogeneous asphalt concrete mixtures before any significant damage is initiated. A typical dense-graded Superpave mixture (12.5 mm nominal maximum aggregate size) is selected as a representative roadway paving mixture and used in this study to accomplish two parallel approaches: Geometrical analysis of mixture heterogeneity using two-dimensional actual images of asphalt concrete inner structures and experimental evaluation through uniaxial tensile tests of asphalt concrete mixtures incorporated with digital image correlation (DIC) technique. To properly address the significant heterogeneity of asphalt concrete mixtures in defining the RVE, several geometrical factors such as area fraction, gradation, orientation, and the distribution of aggregate particles in asphalt concrete mixtures are considered altogether. For the uniaxial tensile test with the DIC, the mean strains and their standard deviations captured by DIC are analyzed to confirm statistical homogeneity of RVEs evaluated from the geometrical analyses. The two approaches present similar results, indicating that typical dense-graded asphalt mixtures can be characterized for their material properties with an approximate RVE size of 60 mm. Findings from this study further imply that the simple geometrical analysis can be an efficient tool to reasonably determine the RVE of asphalt mixtures and other granular composites where significant heterogeneity is involved