Research on the Anisotropy of the Thermal Conductivity of Sandstone Heritage via Digital Rock Physics Under Various Pore Media

The thermal conductivity of sandstone heritage has been emphasized as one of the crucial factors affecting the weathering, in order to further investigate the anisotropy of the thermal conductivity of sandstone at the microscale. In this study, the thermal conductivity of the sandstone samples is measured using the laser flash method. Next, micro-CT images are utilized to reconstruct the digital rock, randomly selected different sizes of REVs (130 × 250 * 250, 100 × 100 * 100, 50 × 50 * 50 voxels) are taken from the reconstructed digital rock. Thermal simulations are then conducted on these REVs in different directions and under steady-state conditions for three pore-filling phases (air, water, and ice). An anisotropic model is introduced to evaluate the thermal conductivity anisotropy of the REVs. Finally, the overall analysis reveals that the pore-filled phase changes from air to water and finally to ice result in an increase of the thermal conductivity of the digital rocks; Additionally, as the thermal conductivity of the filling phase increases, the digital rock progressively transitions towards isotropy. As the porosity of the digital rocks increases, the thermal conductivity decreases and the thermal anisotropy factor diverse further from 1. Changes in REV size has an insignificant effect on the thermal conductivity; however, an increase in the REV size causes the anisotropy factor closer to 1. It is expected the innovative method reported in the present work can provide a feasible and reliable alternative for studying the thermal anisotropy and delaying weathering in stone heritage.