Heat transfer mechanism of EPS concrete with fly ash based on random aggregate model

To investigate the heat transfer mechanism of expanded polystyrene (EPS) concrete, this study was designed to experiment the thermal insulation performance of EPS concrete doped with fly ash. A random aggregate model of EPS concrete was also established to verify the accuracy of the model through experiments. The effects of aggregate volume rate, aggregate shape, aggregate distribution mode, interfacial transition zone and porosity on the thermal insulation performance of concrete were investigated. The heat flow and temperature fields of EPS concrete were analyzed to reveal the heat transfer mechanism of EPS concrete. Finally, a second-order heat transfer calculation model for EPS concrete was developed to predict the effective thermal conductivity. The results show that the thermal conductivity decreases with the increase in volume ratio and porosity of EPS particles, and is 0.24 W/(m·K) at the volume ratio of 40 % and porosity of 13.3 %. The lowest thermal conductivity was found in triangular EPS granular concrete and the highest in pentagonal. The reduction in thermal conductivity was most significant when the rotation angle of elliptical EPS particles ψ a = 0°. As the number of EPS particles and pores increases, the thermal channels narrow, extending the duration of heat flow through the interior of the concrete, which leads to a decrease in thermal conductivity. The established second-order heat transfer model for EPS concrete enables effective prediction of its thermal conductivity. This study integrates experimental, numerical simulation, and theoretical analysis to establish a quantitative relationship between the characteristics of EPS concrete and its thermal performance. The proposed model offers a robust analytical basis for predicting the thermal properties of EPS concrete with fly ash.