Durability of carbon/basalt hybrid fiber reinforced polymer bars immersed in alkaline solution

Abstract Using basalt fiber‐reinforced polymer (BFRP) bars to substitute for steel rebar in seawater sea‐sand concrete (SSC) members is one of effective solutions to steel corrosion. However, there is a concern about the durability of BFRP due to the alkaline of SSC. In this study, a layer of carbon fibers coating (volume fraction was set at 10% and 20%) was used to improve the alkaline resistance of BFRP, which named as carbon/basalt fiber‐reinforced polymer (C/BFRP) hybrid bars. The tensile properties, interlaminar shear strength, and water absorption and diffusion behavior of the C/BFRP were examined by laboratory acceleration methods. The immersion solution temperatures were set at room temperature, 40 and 60°C, immersion mediums were tap‐water and two kinds of alkaline solutions (pH = 10 or 13). Carbon fiber coating is beneficial for improving the mechanical properties of the composite. The higher the fiber volume fraction, the better the long‐term resistance of C/BFRP can be found. However, carbon‐basalt fiber interface is still a weak part in the durability of C/BFRP. The higher the volume fraction of the coating carbon fibers, the greater the quasi‐equilibrium water uptake, which can be attributed that the smaller diameter of carbon fibers embedded the voids between basalt fibers. Reducing environment alkalinity is also beneficial for increasing the service life of C/BFRP, and the tensile strength retention increased by 12% when pH decreased from 13 to 10 after 50‐year. Highlights Carbon fiber coating is beneficial for improving the properties of BFRP. Carbon‐basalt fiber interface is a weak part for the durability of C/BFRP. Reducing alkalinity can improve the durability of BFRP.