Mesoscale Fracture Evolution in Concrete: Insights from GPU-Accelerated 3D Discrete Element Simulations with Realistic Aggregate Morphologies

Deciphering the fracture mechanisms of concrete at the mesoscale is pivotal for predicting the structural integrity of quasi-brittle materials.This study develops a high-fidelity 3D discrete element method (DEM) framework, characterized by real-shaped, crushable aggregates and a sophisticated contact constitutive model designed to address the inherent limitations of traditional DEM, such as insufficient compression-to-tension ratios and the lack of softening effects.Implemented on the opensource platform MUSEN with GPU-accelerated computing, the model enables large-scale simulations of wedge splitting tests (WST) with unprecedented efficiency.Validation against laboratory experiments confirms the model's capability to capture the macroscopic mechanical response and the intricate F-CMOD relationship.Through the evolution of internal principal stress fields, the study clarifies how boundary-induced end effects and mesoscopic heterogeneity govern crack initiation and propagation.Furthermore, a parametric analysis of aggregate and interfacial transition zone (ITZ) strengths reveals a fundamental transition from transgranular to intergranular failure modes.The results quantify the crack-bridging and toughening mechanisms provided by aggregates, providing a robust computational tool for the multiscale design and safety assessment of concrete structures.