The reinforcement mechanism of surface-modified basalt fibre on the mechanical properties of concrete

Basalt fibre (BF) is frequently used as a reinforcing material in concrete. In this study, to enhance mechanical interlocking at the fibre–matrix interface, BF was surface-modified using the silane coupling agent KH550 to produce modified basalt fibre (MBF). The physico-mechanical properties of concrete reinforced with unmodified basalt fibre (BFRC) and MBF-reinforced concrete (MBFRC) were evaluated. With an increase in the content of MBF, the P-wave velocity and mechanical properties of the MBFRC initially increased and then decreased. The mechanical strength was the highest with 0.05% volume fraction of BF. Compared with BFRC, after 28 days of curing, the uniaxial compressive strength, splitting tensile strength and flexural strength of the MBFRC increased by approximately 7.1%, 4.8% and 14.9%, respectively. Although the single-fibre tensile strength of the MBF was not increased, scanning electron microscopy and atomic force microscopy observations showed that modification with KH550 roughened the surface of the BF. These results suggest that the increased surface area of the MBF may facilitate additional nucleation sites for hydration products, thereby reducing interfacial pore defects and improving load transfer and crack-bridging efficiency. The study provides a new method for the strength improvement of BFRC.