Abstract: The aim of this research is to explore the mechanical properties and failure law of lightweight aggregate concrete. Lightweight aggregate concrete is regarded as a two-phase heterogeneous composite composed of spherical lightweight aggregate particles and mortar matrix. A three-dimensional random aggregate model is established using mesoscopic numerical simulation method to simulate the uniaxial compressive failure process of lightweight aggregate concrete. The influences of constraint effect of loading end face on crack propagation and material's mechanical properties are studied and analyzed. Results demonstrate that 1) compared with ordinary concrete, lightweight aggregate concrete sees the first crack at lightweight aggregate during compression failure, and the crack extends directly through the lightweight aggregate; 2) specimens with unrestrained loaded end face finally witness axial splitting failure, and those with restrained loaded end face undergo inverted cone failure; 3) compared with the constrained specimens, the unconstrained specimens see reductions of compressive strength and peak strain by 29.6% and 45.5%, respectively. The proposed model and simulation results provide an effective supplement to the shortcomings of traditional macro-level tests.

Key words: lightweight aggregate concrete, meso-scale simulation, random aggregate model, compression failure, end surface effect, failure mode