Pore structure and thermal conductivity of basalt fiber reinforced foam concrete under freeze-thaw cycles

To study the pore structure and thermal conductivity characteristics of basalt fiber reinforced foam concrete (BFRFC) under freeze-thaw cycles, four BFRFC samples with different fiber contents were selected. X-CT technology and Avizo software were employed for three-dimensional reconstruction to analyze the pore structure and fiber distribution characteristics. Thermodynamic performance tests and COMSOL numerical simulations were conducted to investigate the changes in thermal conductivity of BFRFC under different freeze-thaw cycles. Based on the Bruggeman model for porous media and the parallel and series conduction mechanisms of fibers, a theoretical thermal conductivity model for BFRFC was proposed. The results show that the pore size and shape factor of BFRFC approximately follow a log-normal distribution, with fiber polar and azimuthal angles uniformly distributed in the ranges of 15° to 90° and 0° to 360°, respectively. BFRFC's thermal conductivity ranges from 0.2 to 0.4 W/(m·K), primarily influenced by porosity and freeze-thaw cycles, with fiber content having a smaller impact. By establishing a numerical simulation model of BFRFC and using COMSOL to simulate thermal conductivity, the results were found to be consistent with experimental data. The theoretical thermal conductivity model, based on the Bruggeman model and the parallel-series fiber model, effectively predicts the thermal conductivity of BFRFC under different fiber contents and porosity conditions, providing a theoretical basis for the application of BFRFC in cold region engineering.