Meso-Structural Modeling of Asphalt Mixtures Using Computed Tomography and Discrete Element Method with Indirect Tensile Testing

This study develops a meso-structural modeling approach for asphalt mixtures by integrating computed tomography (CT) technology and the discrete element method (DEM), which accounts for the morphological characteristics of aggregates, asphalt mortar, and voids. The indirect tensile (IDT) tests of SMA-13 asphalt mixtures, a commonly used skeleton-type asphalt mixture for the surface course of asphalt pavements, were numerically simulated using CT-DEM. Through a comparative analysis of the load-displacement curve, the peak load, and the displacements corresponding to the maximum loads from the IDT tests, the accuracy of the simulation results was validated against the experimental results. Based on the simulation results of the IDT tests, the internal force transfer paths were obtained through post-processing, and the force chain system was identified. The crack propagation paths and failure mechanisms during the IDT tests were analyzed. The research results indicate that under the external load of the IDT test, there are primary force chains in both vertical and horizontal directions within the specimen. The interaction between these vertically and horizontally oriented force chains governs the fracture progression of the specimen. During IDT testing, the internal forces within the aggregate skeleton consistently exceed those within the mortar, while interfacial forces at aggregate-mortar contacts maintain intermediate values. Both the aggregate's and mortar's internal forces exhibit strong linear correlations with temperature, with the mortar's internal forces showing a stronger linear relationship with external loading compared to those within the aggregate skeleton. The evolution of internal meso-cracks progresses through three distinct phases. The stable meso-crack growth phase initiates at 10% of the peak load, followed by the accelerated meso-crack growth phase commencing at the peak load. The fracture-affected zone during IDT testing extends symmetrically 20 mm laterally from the specimen centerline. Initial meso-cracks predominantly develop along aggregate-mortar interfaces and void boundaries, while subsequent propagation primarily occurs through interfacial zones near the main fracture path. The microcrack initiation threshold demonstrates dependence on the material's strength and deformation capacity. Furthermore, the aggregate-mortar interfacial transition zone is a critical factor dominating crack resistance.