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.

This study presents a multiscale computational model for predicting the mechanical behavior of asphalt mixtures. The model can account for mixture heterogeneities by considering individual mixture constituents through the scale-linking technique: a local scale in a form of the heterogeneous representative volume element and a global scale that has been homogenized from local scale responses. The model is implemented with a finite element formulation, so that geometric complexities, material inelasticity, and the growth of time-dependent damage can be properly handled. Damage is in the form of cracks modeled with nonlinear viscoelastic cohesive zones. The primary purpose of this paper is to present the multiscale modeling framework developed and to evaluate the applicability of the multiscale modeling technique to determine the performance of asphalt mixtures and structures when damaged. This is accomplished by employing only material properties at the constituent level (local scale) as model inputs. The indirect tensile test of fine-aggregate matrix mixture is simulated as an example, and the simulation results are compared with experimental results to evaluate the applicability of the model. Predictive power of the model and the benefits related to the reduction of computational efforts and laboratory tests are further discussed.

The objective of this study is to evaluate the effect of mix gradations associated with the Superpave restricted zone on rutting potential specifically for low traffic volume roadways. Although the elimination of the restricted zone requirement in Superpave mix design is highly recommended, some questions still remain unanswered as the research conclusions supporting the elimination of the restricted zone were largely made for medium to high traffic volume roadways, where aggregates are highly crushed and of good quality. The applicability of such research conclusions based on high traffic volume mixes needs to be verified for low volume mixes because many states in the United States (US) use noncrushed local aggregates for low traffic volume pavements, which might be related with aggregate gradation. This paper summarizes the research findings obtained from a systematic approach consisting of (1) statistical analyses of preexisting data accumulated for quality assurance purposes, (2) experimental investigations based on the statistical analysis results, and (3) in-field investigation of the rutting performance of low traffic volume pavement. The comparison

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.

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