Computational homogenization for thermal conduction in heterogeneous concrete after mechanical stress

Concrete structures are subjected to various loadings during their service life and their internal structures will be changed, resulting variations in mechanical and thermo-physical properties. To investigate the effect of mechanical stress on thermal conduction, a computational homogenization method from a mesoscopic perspective was proposed in the present work. In the simulations, concrete was considered as a three-phase composite material consisting of aggregate, mortar matrix and the interfacial transition zones (ITZs) between them. The mechanical analysis was conducted firstly to study the damage distribution within concrete. The outcomes of mechanical computation were then used as the initial input data in the thermal conduction computation. The equivalent thermal conductivity of damaged element was homogenized by a composite mechanical method based on damage and the initial thermal conductivity of sound material. Accordingly, a meso-scale model in which the mechanical and thermal behavior were one-way coupled was built. The method was calibrated by comparing the numerical results with the available experimentally measured ones. Based on the verified simulation method, effective thermal conductivity (ETC) and temperature field of concrete subjected to different loading levels were calculated. Besides, the effects of loading type (compressive and tensile loadings) on ETC and temperature field of concrete were studied. It is found that ETC of concrete decreases with an increasing loading level. In addition, the effect of tensile loading on thermal behavior depends on whether the direction of thermal conduction is parallel or perpendicular to loadings.