Investigation into the long-term alkali resistance of basalt fibers

To more accurately simulate the alkaline environment of basalt fiber in cement-based materials, this study innovatively employs the benchmark cement supernatant as the alkaline solution for the long-term corrosion testing of basalt fiber (BF). Additionally, through mechanical performance testing of mortar containing basalt fiber at different ages, the study reveals the corrosion behavior of basalt fiber in an alkaline environment. The results indicate that basalt fiber undergoes corrosion in the benchmark cement supernatant, where the OH- ions in the solution react with SiO2 in the basalt fibers, thereby disrupting the silicate framework of the fibers and causing pitting corrosion on the fiber surface. The black and white binarization analysis of the SEM images of BF7 after 360d erosion revealed that the corrosion pits covered 31.50 % of the fiber surface area, indicating severe corrosion. Furthermore, the study on the long-term mechanical properties of basalt fiber mortar demonstrated an initial increase in performance, followed by a gradual decline as the curing age progressed. Notably, after 360d of curing, the flexural strength of basalt fiber mortar was lower than that at 30d. For instance, the 360d flexural strength of BF10.1 and BF7-0.1 decreased by 18.85 % and 14.54 %, respectively, compared to 30d. This decline is primarily attributed to the corrosion of basalt fibers in alkaline environments, leading to a decrease in their mechanical properties. Therefore, it is essential to enhance the alkali resistance of basalt fibers when used in cement-based materials.