Mesoscopic Analysis of the Temperature-dependent Thermal Conduction Behavior Within Concrete

Considering the heterogeneity of concrete and temperature-dependency of materials, both 2D and 3D random aggregate structures of concrete were established to analyze the heat conduction behavior of heterogeneous concretes. In the numerical homogenization technique, concrete was regarded as a heterogeneous material consisting of three components, i.e., aggregate, mortar matrix and the interfacial transition zones (ITZs). The temperature-dependent thermal properties of mortar and aggregate were obtained based on the experimental data from the available literatures and those of the ITZ were determined by comparing the simulation results with measured values. The heat conduction equations were solved by using finite-element method. Good agreement between the present simulation results and available test observations illustrates the accuracy and reasonability of the developed approach. The simulation results indicate that not only the effective thermal conductivity (ETC) but also a more accurate temperature field of concrete can be obtained by the meso-scale simulation method considering temperature-dependency of materials' thermal properties. Aggregate shape has a negligible influence on the ETC of concrete while the effect of aggregate type cannot be ignored due to their different thermal conductivities. The ETC of concrete increases with increasing aggregate content while decreases when the temperature increases.