Effects of Water and Alkaline Solution on Durability of Carbon-Glass Hybrid Fiber Reinforced Polymer Bars

The glass fiber reacts with the hydroxyl owing to the concrete pore solution. A thin coat of carbon fiber wraps around the internal GFRP bars to improve the durability of internal GFRP bars in harsh environments. This paper investigates the effect of a thin carbon fiber coat on the durability of the carbon-glass hybrid fiber reinforced polymer bars (HFRP bars) in water, and compares the performance of FRP bars in alkaline solution. To this end, the water absorption behavior, interlaminar shear strength of both the GFRP bars and the HFRP bars was characterized in water and alkaline solution. The results indicate that the diffusivity coefficient of the carbon fiber coat is higher than that of internal GFRP in water. Compared to the GFRP bars in water, the HFRP bars have a higher diffusivity coefficient and saturation water absorption. It caused that the interlaminar shear strength of the HFRP bars aged in water at a temperature of 60 °C for 140 days decreases more markedly than that of the GFRP bars aged under similar conditions. Finally, it was proved that the thin carbon fiber coat does not slow the deterioration of the GFRP bars in water, while the carbon fiber coat significantly improves the retention of the interlaminar shear strength of the HFRP bars in the alkaline solution owing to the prevention of internal glass fiber reactivated by alkali ions.