Characterisation of temperature-dependent heat conduction in heterogeneous concrete

Considering the heterogeneity, a mesoscopic simulation method was developed to analyse the heat conduction behaviour of heterogeneous concretes. In the numerical homogenisation technique, the concrete was regarded as a heterogeneous material consisting of three components (aggregate, mortar matrix and interfacial transition zones (ITZs)). Both two- and three-dimensional random aggregate structures of concrete were established. The temperature-dependent thermal properties of the mortar and aggregate were obtained based on experimental data from the literature, and those of the ITZ were determined by comparing the simulation results with measured values. The heat conduction equations were solved using the finite-element method: the three components were meshed separately and continuity of the heat fluxes at interfaces was applied. Good agreement was found between the simulation results and available test observations. The simulation results indicate that both the effective thermal conductivity (ETC) and a more accurate temperature field of concrete can be obtained using this mesoscale simulation method considering the temperature dependency of the materials' thermal properties. Aggregate shape was found to have a negligible influence on the ETC of concrete, but the type of aggregate cannot be ignored due to their different thermal conductivities. The ETC of concrete increased with increasing aggregate content and decreased with increasing temperature.