Determining representative volume elements of asphalt concrete mixtures without damage

This study presents a simple method to define the representative volume elements (RVEs) of asphalt concrete mixtures without damage. Three currently used asphalt concrete mixtures (two dense-graded Superpave® mixtures with different nominal maximum aggregate sizes of 9.5 and 12.5 mm and one stone matrix asphalt mixture with a nominal maximum aggregate size of 19.0 mm) were selected and evaluated. To address the significant heterogeneity of asphalt concrete mixtures properly in defining RVEs, several geometrical factors, such as area fraction, gradation, orientation, and the distribution of aggregate particles in asphalt concrete mixtures, were all considered together by using two-dimensional images of actual asphalt concrete inner structures produced by digital-image processing. Geometrically defined RVEs were then supported by finite element simulations to check whether effective nondamage material properties obtained from the RVEs, such as the linear viscoelastic dynamic modulus, were representative of the corresponding bulk asphalt concrete mixture. Analysis results indicated that typical dense-graded Superpave asphalt concrete mixtures can be characterized by their effective non-damage properties with an approximate RVE size of 50 mm. However, the properties of stone matrix asphalt mixtures, which contain larger aggregates, should be measured on a larger scale for improved accuracy. Findings from this study were generally consistent with results of other studies performed on the basis of extensive laboratory tests, which implies that the simple geometrical-numerical method here can be a potentially efficient approach to define the RVEs of asphalt mixtures with much less time and effort.