Abstract: With the advantages of lightweight, corrosion resistance, remarkable strengthening effect, FRP grids have good application prospects in the field of civil engineering. However, the manufacturing technology of traditional hand lay-up affects the quality of the products and the stability of their performance and limits their applications in engineering. The technology of Vacuum Assisted Resin Infusion (VARI) was employed and developed to manufacture the FRP grids in this paper, and two types of FRP grids made of basalt fiber and carbon fiber were manufactured. The corresponding three kinds of tensile specimens cut from the FRP grids were tested. The experimental results indicate that the elastic modulus of FRP grids is stable, whereas the ultimate strength and ultimate strain show large deviation. With the increasing of the fibers of FRP grids, the failure probability due to defects of fibers increases, and the available strength and strain ability decrease, and the elastic modulus is not significantly varied. The different FRP grids reinforced with various types of fibers exhibit different mechanical properties. Basalt fiber reinforced plastic grids have lower ultimate strength and elastic modulus than carbon fiber reinforced plastic grids, but the former has larger ultimate strain than the latter. The effectiveness of underwater concrete columns strengthened with FRP grids was validated, and the strengthened columns have a significant increase in load carrying and deformation ability.

Key words: fiber, FRP, grids, tensile performance, strengthening