The paper aims to simulate the micromechanical behavior of asphalt mixtures during the compaction process using the Discrete Element Method (DEM). The interactions between the components of a Porous Asphalt (PA) mixture were represented using an Elastic Viscoelastic Contact Model (EVCM), which is a user-defined model implemented in EDEM software, developed based on linear elastic and Burger's viscoelastic constitutive equations. The macroscale parameters of asphalt mortar were characterized using the nonlinear regression analysis of master curves obtained from Dynamic Shear Rheometer (DSR) tests. The verification process of EVCM successfully indicated that the computations trends fall within the range of expected values for the typical asphalt mixture material. Further, a Superpave Gyratory Compaction (SGC) test was carried out and the obtained sample was scanned using X-ray Computed Tomography (X-ray CT) to capture the air void distributions. The DEM was utilized where digital samples were established to simulate the overall process of laboratory and field compaction. The simulation results showed that the model provided a comparable prediction of responses and demonstrated the capability of SGC to fabricate a representative sample. The influence of temperature on the asphalt compaction process was explored and the results implied that temperature decreasing adversely affects the compactability and dramatically increases the demanded compaction efforts which are consistent with the law of viscoelasticity. On the contrary, when the temperature is high, the asphalt binder becomes too fluid and roller loads will simply displace, or “shove” the mat rather than compact it. Tracking the change in the air voids proportion indicates that the motion of aggregates is rather compound. The aggregates flowed vertically downwards in line with the compacting orientation while moved horizontally outwards away from the center. The results demonstrated that the model effectively simulated the compaction process, the developed model, and can be considered as a useful tool. All in all, the findings confirm that the concept is technically practicable, affording the model a tremendous potential to help researchers understand the microstructural phases of asphalt mixture during the compaction.

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The mechanical properties of asphalt mixture are always required for the evaluation of the durability of pavements. In order to obtain these properties without conducting expensive laboratory tests and using calibrated empirical models, research studies have been carried out to develop micromechanics-based models. Continuum-based micromechanical models (CBMM), which are developed based on continuum mechanics, have increasingly been utilized to estimate the mechanical properties of asphalt materials based on the fundamental properties of individual constituents. These analytical models are expected to provide reliable predictions without the need for extensive computational facilities. Although the utilization of CBMM has been presented by several past studies, most of the studies do not provide a concise and critical review of these models. Therefore, in this paper, a complete review of CBMM was presented. Commonly used CBMM were introduced in detail and their advantages and disadvantages were discussed and compared. Comprehensive summaries and critical discussions about their current utilization and limitations for predicting the mechanical properties of asphalt materials were given. Further modifications and new development for addressing the limitations were extensively described and discussed. In the end, research challenges were highlighted and future recommendations from different perspectives were proposed.

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The motivation of this research is to simulate the micromechanical behavior of asphalt mixtures using the Discrete Element Method (DEM). A bonded-contact model, named as EVCM, was developed to describe the micromechanical behavior of asphalt mixture, based on linear elastic and Burger’s viscoelastic constitutive equations. The EVCM is a new user-defined model implemented in the EDEM software. The microscale parameters of asphalt mortar were characterized by fitting the Burger’s model to Dynamic Shear Rheometer (DSR) data. A simple model was developed to evaluate EVCM, and the produced analysis successfully indicated that the trends of computations fall within the range of values expected of typical asphalt mixture materials and the EVCM is sensitive to the loading rate. Further, a Superpave Gyratory Compaction (SGC) test was carried out to compact a porous asphalt mixture and the obtained specimen was scanned using X-ray Computed Tomography (X-ray CT) to capture the air void distributions. The DEM was utilized to simulate the overall process of the SGC laboratory test where a digital specimen was established. The simulation predictions have shown agreement with the lab results and proved the ability of the EVCM to simulate and predict the micromechanical behavior of a PA mixture across a range of temperatures. The model was employed to assess the air voids distribution showing a good agreement at the top, but an opposing trend at the bottom.@en