Multiscale characterization and modeling of aggregate contact effects on asphalt concrete's tension–compression asymmetry

Asphalt concrete (AC) exhibits significant tension–compression (TC) asymmetry and aggregate contacts can be one of the critical contributors to this behavior. Nevertheless, the underlying mechanisms are still unclear, and there has been no study to quantify this behavior. To fill the research gap, multiscale characterization and modeling on AC were performed in this study. At the microscale level, nanoindentation tests were conducted to characterize the aggregate contact characteristics in the contact region (CR). The CR was found to have a sandwich-like structure consisting of two interfacial layers, large filler particles, and asphalt mastic. Accordingly, micromechanical models of CR were developed to predict its mechanical behavior in tension and compresison (T&C). The modeling results showed that aggregate contacts significantly increase the compressive modulus, leading to the substantial TC asymmetry of CR. The predicted viscoelastic properties of CR were further applied to the developed mesostructural model of AC. The predicted master curves in T&C showed significant asymmetry and quantitatively agreed with the experimental ones, demonstrating the effectiveness of the adopted modeling approaches. This study is the first study to quantify the asymmetric performance of AC. The outcomes can be applied to evaluate AC's TC asymmetry effects on pavement performance.