Study on durability of transverse shear properties for novel carbon/glass hybrid fiber-reinforced polymer bars in simulated concrete environments

Durability on the transverse shear properties of hybrid fiber-reinforced polymer (HFRP) bar may control the cross-sectional load-bearing capacity and failure mode of the HFRP bar reinforced concrete members due to its strength degradation with time. Herein, the degradation of novel carbon/glass (C/G)-HFRP bars were accelerated in simulated concrete environments at 60 degrees C to investigate the effects of fiber volume fraction and distribution pattern, matrix resin volume fraction, exposure environment, and period on their transverse shear properties. The results displayed that the transverse shear strength of the samples reduced by 15%, 20%, and 8% after exposure to the simulated ordinary concrete, seawater sea-sand concrete environments, and tap water for 6 months, respectively. The inward diffusion of water molecules and free hydroxyl ions caused the hydrolysis of matrix resin, etching of glass fiber and debonding of fiber/matrix interface, which were the incentives of the degradation of C/G-HFRP bars. The increase of matrix resin volume fraction and the application of a waterproof coating were recommended to alleviate the degradation of fibrous composites in concrete environments. Finally, two prediction models were proposed to determine the transverse shear strength of HFRP bar before and after exposure to different harsh environments, respectively. The comparisons indicated that the predicted values were coincided with the experimental results.