Abstract: FRP bars are prone to alkali corrosion and performance degradation in high-alkalinity cement concrete. To address this issue, types of low-alkalinity cement(high-belite sulfoaluminate cement and slag sulfoaluminate cement) were proposed for the preparation of low-alkali cement concrete. The pH evolution of the pore solution in low-alkalinity concrete immersed in freshwater and seawater was measured. Experimental studies were conducted to examine the performance changes of FRP bars after immersion in simulated pore solutions, as well as the time-dependent evolution of the bond strength at the FRP bar-low-alkalinity cement concrete interface. The results indicate that the pore solution pH of the two low-alkalinity cement concretes is reduced by 0.7 to 2.0 compared to Portland cement concrete, with seawater exposure contributing to a further decrease in pH. The alkali corrosion rate of FRP bars is significantly lower in low-alkalinity simulated pore solutions. Based on experimental data and the Arrhenius degradation model, the estimated service life of FRP bars in low-alkalinity cement concrete simulated pore solutions increases by 10% to 30% compared to those in Portland cement concrete simulated pore solutions. Additionally, seawater exposure promotes strength development in low-alkalinity cement concrete while lowering the concrete pH. After 180 days of immersion in artificial seawater at 40 ℃, the bond strength at the FRP bar-low-alkalinity cement concrete interface increases by 10% to 30%, whereas that at the FRP bar-Portland cement concrete interface decreases by 10% to 15%. In conclusion, the adoption of novel low-alkalinity cement can significantly enhance the bond strength between FRP bars and concrete while improving the durability of structures in marine environments.

Key words: FRP bar, high-belite sulfoaluminate cement, slag sulfoaluminate cement, bond strength, alkali corrosion