Mesoscopic Fracture Modeling of Lightweight Aggregate Concrete Under Compression

This study investigates the damage and fracture evolution mechanisms of lightweight aggregate concrete (LWAC) through mesoscale simulation. A hybrid method based on Voronoi diagrams and the Random Walk Algorithm (RWA) was employed to construct aggregate morphology and ideal gradation models, enabling the modeling of mesostructures with high aggregate content (25–35%). The finite element method was utilized to simulate the crack propagation and damage process of LWAC under uniaxial compression. The study revealed key regulatory factors: (1) Aggregate content significantly influences mechanical responses; compressive strength and elastic modulus exhibit an inverse relationship with increasing content, with 30% serving as a critical threshold. When content increases to 35%, the strength of LWA-600 drops sharply by 16.8%, and the stress–strain curve exhibits a sudden decline, reflecting the synergistic expansion of aggregate damage and cracks. (2) Enhanced aggregate strength (e.g., LWA-900) increases the elastic modulus of LWAC, making its mechanical behavior more akin to that of pure mortar matrix. (3) Mortar strength plays a decisive role; high-strength mortar significantly improves the compressive performance of LWAC, while low-strength mortar, due to reduced strength disparity with aggregates, induces plastic damage characteristics. Numerical simulation results align closely with experimental observations, validating the model’s effectiveness and providing a theoretical basis for multiscale mechanical regulation and engineering optimization design of LWAC.