The enhancement mechanism of modified basalt fiber on the performance of geopolymer concrete

Incorporation of fibers can significantly enhance the mechanical properties, and crack resistance of geopolymer concrete (GPC). However, the alkaline environment in GPC can adversely affect the performance of fibers. To address this issue, this paper focuses on the surface modification of basalt fibers using a silane coupling agent (SCA) to enhance their compatibility with the geopolymer matrix. Macroscopic tests are conducted to analyze the workability, compressive strength, and flexural strength of geopolymer concrete, as well as the three-dimensional condition of its damaged surface. At the microscopic level, the fiber/matrix interface is investigated using scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) to reveal the enhancement mechanism of the modified basalt fibers (MBF). The experimental results demonstrate that the MBF significantly improves the flexural of GPC and has stronger impact on the degree of flexural deflection of the fracture surface compared to unmodified basalt fibers (BF). Physical aspects of SCA film: increases the roughness of the surface of basalt fiber, improves the mechanical occlusion at the interface between the fiber and the matrix and the transfer of concrete matrix stress. Chemical aspects: reduces the ground polymer matrix -OH ions on the fiber surface erosion, to ensure the stability of the SiO₄ tetrahedral network structure of the basalt fiber surface, increases the fiber and matrix interface at the densification, improves the chemical adhesion. In summary, the MBF effectively enhances the mechanical properties of GPC by optimizing the interfacial bond, enhancing cohesion, and improving the microstructure. These findings provide valuable insights into the potential application of SCA-modified basalt fibers as a promising reinforcement in GPC for sustainable construction and infrastructure projects.