Xiaohan Zhou, Zirui Li, Xinrong Liu, Yan Wang, Libing Du
The precise calculation of concrete thermal conductivity is of significant engineering value for optimising the thermal performance of buildings. To address this issue, the paper proposes a calculation model for concrete thermal conductivity considering microstructural characteristics. Firstly, unsaturated mortar is simplified as a three-phase material comprising gas-phase pores, liquid-phase pores, and non-porous mortar. The equivalent thermal conductivity of the mortar is calculated using the parallel model. Secondly, the interfacial transition zone (ITZ) is simplified as a three-phase material comprising mortar, gas-phase pores, and liquid-phase pores. The equivalent thermal conductivity of ITZ is calculated using the parallel model. Thirdly, an aggregate-interface composite (AIC) is established, and its equivalent thermal conductivity is calculated using the cubic dispersed phase parallel-series model. Finally, concrete is simplified as a two-phase material comprising AIC and mortar, with its equivalent thermal conductivity calculated using the cubic dispersed phase parallel-series model. Numerical simulation and experimental data validation indicate that the relative error range between the model and numerical simulation is -4.5% to -2.5%, while the relative error range compared to experimental data is -10.4% to 5.6%. Comparison with existing theoretical models reveals that the proposed model exhibits lower MSE, RMSE, and MAPE metrics than other models. This model effectively characterises the nonlinear response relationship between microstructural parameters and concrete thermal conductivity. Based on the model, the study systematically reveals the influence laws and sensitivity of factors such as aggregates, pores, and ITZ on concrete thermal conductivity. The model achieves cross-scale characterisation of concrete thermal performance, providing a reliable computational framework for the optimised design of concrete thermal performance.