Numerical study on the effect of pore shapes on the thermal behaviors of cellular concrete

This paper proposes a numerical method to study the effect of pore shapes on the effective thermal conductivity (ETC) of cellular concrete by a two-dimensional model. Cellular concrete can be seen as a composite of two phases with pore and cement paste. The model is established by two steps. Firstly, a generation of two-dimensional representative volume element of cellular concrete microstructure is necessary. Secondly, a finite element method is adopted to simulate heat transfer through the pixelated microstructure. Simulations are validated against analytical approximations, as well as experimental data from the literature. The model can also be used to evaluate the pore size distribution and orientation effects that are hard to measure only in laboratory experiments. It is concluded that ETC decreases when triangle pores substitute for circular pores on account that the tortuosity increases continuously. The other shapes of non-circular pores (square, pentagon and hexagon) have negligible effects on ETC. For ellipse cases, ETC decreases with increase in aspect ratio and volume fraction of pore. In the case of aligned pores, the ETC is larger along the principal axis. However, the size distribution of pores seems to have an insignificant influence. The numerical results suggest that the finite element method (FEM) considering quantitative data of thermal transfer behavior of cellular concrete can be obtained by the pore shapes, and it may be of great help to the optimization of materials.