Efficient numerical model for effective thermal conductivity of concrete with aggregates of different morphologies and imperfect interfaces

Abstract

The existing numerical model for predicting the effective coefficient of thermal conductivity (CTC) of concrete usually ignores its mesostructure such as the three dimensional (3D) irregular aggregate morphology, imperfect interface, phase in voids, and spatial distribution of aggregates. Meanwhile, most numerical models adopt the uniform temperature gradient in the homogenisation process, resulting in the larger model size required for convergence and lower post-processing efficiency. An algorithm to generate concrete with aggregates of different morphologies and imperfect interfaces was proposed. Subsequently, a simple method of imposing the periodic boundary conditions and an efficient post-processing method were proposed, thereby reducing the time consumption in the numerical homogenisation substantially. In addition, based on the mesomechanical analytical model, DIGIMAT, and experimental data, the rationality of the proposed method and established models was validated, and the effect of the 3D mesostructure of concrete on its effective CTC was analysed. Results show that the concrete exhibits imperfect interfaces in its service life, especially in the dried working condition. The concrete gradation, phase in voids, and aggregate orientation have different degrees of influence on the effective CTC of concrete, and the effect of aggregate morphology can be ignored.