Mesostructure and thermal conductivity attenuation properties for basalt fiber reinforced Foam binder under freeze-thaw degradation conditions

Abstract

Foam binder (FB), as a lightweight cementitious material with favorable thermal insulation properties, is regarded as having promising applications in building and road engineering. While the incorporation of Basalt Fibers (BF) can markedly enhance its mechanical performance, their impact on thermal behavior under Freeze–Thaw Degradation (FTD) remains insufficiently understood. To investigate this, five types of FB with fiber volume fractions of 0 %, 0.15 %, 0.30 %, and 0.45 % were subjected to 0, 40, and 80 freeze–thaw cycles. The internal pore structures under FTD were reconstructed using X-ray computed tomography (X-CT). Based on the reconstructed models, thermal conduction simulations were performed using COMSOL. A predictive model for thermal conductivity degradation under FTD was then developed by integrating effective medium theory with the parallel–series composite model. The results indicate that the addition of BFs effectively reduces the porosity of FB, with reductions ranging from 1 % to 3 % at a fiber volume fraction of 0.45 %. Furthermore, the presence of BFs significantly mitigates the rate of thermal conductivity degradation during freeze–thaw cycling. Simulation results reveal that heat conduction predominantly occurs through the cement matrix, while BFs lower the overall thermal conductivity by modifying the heat flow path. The proposed predictive model, which incorporates fiber content, density, porosity, and freeze–thaw cycle number, demonstrates good agreement with experimental data, with a prediction error of less than 10 %. This model offers theoretical support for understanding the evolution of thermal properties in basalt fiber–reinforced foamed binder (BFRFB) under FTD.