Study on quasi-brittle fracture modeling of concrete based on coarse aggregate size and content

To investigate the influence of coarse aggregate size and content on concrete fracture, single-edge notched beam tests were performed on mixtures with three aggregate sizes (5–10 mm, 10–15 mm, 15–20 mm) and four contents (0, 300, 600, 900, 1200 kg/m³). The findings reveal that the crack path deviation increased with larger aggregate size and higher content. The initial fracture toughness, unstable fracture toughness, and fracture energy all increased with both parameters. At the maximum content of 1200 kg/m³, fracture energy increased by 43.4 %, 65.5 %, and 81.7 % for the three sizes, respectively, compared to the aggregate-free mix. A new quasi-brittle fracture model was proposed, which incorporated a maximum virtual particle size ( d v-max ) parameter to synthesize the effects of aggregate size and content. This model provided improved predictions of fracture toughness across the tested mixes, offering a theoretical framework for fracture property evaluation.