The effects of basalt fibers and cooling methods on the mechanical properties of concrete after high-temperature exposure

This study aims to evaluate the effects of basalt fibers on the triaxial compressive permeability and shear performance of concrete after exposure to high temperatures under different cooling methods. The triaxial compressive strength, permeability, and shear performance of ordinary concrete (OC) and basalt fiber-reinforced concrete (BFRC) were investigated. The results indicate that the incorporation of basalt fibers significantly improves the density and compressive strength of concrete, with the most pronounced enhancement observed at a 1.0% volume fraction. After high-temperature exposure, the mass loss rates of both OC and BFRC increased with rising temperatures, while the relative dynamic elastic modulus gradually decreased. Performance degradation was more pronounced under water cooling conditions compared to natural cooling conditions. The addition of basalt fibers effectively reduced the mass loss rate and improved the relative dynamic elastic modulus. In triaxial compression tests, natural cooling was more effective than water cooling at maintaining the strength and toughness of concrete. During water cooling, the thermal shock effect resulted in increased internal cracking, thereby significantly increasing the permeability. However, the addition of basalt fibers effectively reduced the porosity of concrete, thus enhancing its impermeability. Furthermore, in variable-angle shear tests, basalt fibers significantly improved the shear performance and toughness of concrete, particularly under water cooling conditions. The findings of this study provide theoretical and practical references for the application of basalt fiber-reinforced concrete in high-temperature environments.