Mesoscale model for mechanical property evolution of low-carbon concrete incorporating structural enhancement and interfacial weakening effects induced by waste rock

Low-carbon concrete (LCC) utilizes solid waste materials such as waste rock, recycled concrete aggregate, and fly ash to replace natural aggregates and cement, offering benefits in reducing environmental damage and carbon emissions in building engineering. Due to the use of various solid waste materials in the preparation of LCC, extensive trial production is necessary to determine the optimal mix proportions. To accurately calculate the evolution of LCC mechanical properties with varying mix proportions, we propose a mesoscale model based on the discrete element method, considering coarse aggregates and interfacial transition zones (ITZ). The proposed model generates ITZ through differential attractive forces between mortar and waste rock particles, capable of reflecting variations in aggregate content, particle size gradation, aggregate morphology, and cementation degree of ITZ. The laboratory and numerical tests were performed to validate the accuracy of the proposed model in characterizing the mechanical property evolution of LCC. Results indicate that the mesoscale model successfully predicts the evolution patterns of LCC’s elastic modulus and uniaxial compressive strength under varying cementation degrees of ITZ. Numerical test results clarified the range of fluctuations in LCC’s mechanical properties influenced by ITZ, and laboratory test results consistently fell within this range. Simulations further revealed that increased waste rock content elevates the number of unclosed contacts in LCC numerical specimens by 67% to 90%, consequently increasing the proportion of tensile microcracks during compressive failure of LCC. The proposed mesoscale model was applied to evaluate the cementation degree of ITZ in actual LCC specimens, and the results were consistent with practical observations. • A mesoscale model for mechanical property of low-carbon concrete is established. • The weakening effect of waste rock on LCC depends on ITZ cementation degree. • Unclosed contacts within ITZ shift the LCC failure mode toward tensile failure. • The mesoscale model can evaluate the degree of ITZ cementation in actual LCC.