Abstract: In order to improve the mechanical properties of the composite materials of concrete with basalt fiber, the ethyl orthosilicate, which was a relatively cost-effective silane coupling agent, was used to modify the surface of basalt fibers. These modified fibers were then introduced into concrete as the reinforcing phase to improve the mechanical performance of the concrete material. The microstructure of both fibers and concrete was studied by scanning electron microscopy. The influence of basalt fibers on the rheological properties of the fresh concrete was studied. The mechanical strength of concrete was assessed by three mechanical strength indicators: compressive strength, splitting tensile strength, and flexural strength. As a result of this, the addition of basalt fibers reduces the variability of the fresh concrete. After modification, the introduction of basalt fibers into the concrete results in a tighter interface boundary adhesion between basalt fibers and concrete. At the optimal addition amount of 4 kg·m^－3, the compressive strength, splitting tensile strength, and flexural strength of concrete composite materials increases by 6.83%, 21.46%, and 12.7%, respectively.

Key words: basalt fiber, concrete, surface modification, mechanical strength