Effects of pH value and temperature in pore solution of carbonated SCM concrete on creep rupture performance of BFRP bars

The mechanical performance of basalt fiber reinforced polymer (BFRP) bars can deteriorate as a result of creep rupture due to sustained loading and alkaline corrosion caused by concrete alkalinity. Unfortunately, the effect of alkaline corrosion on the creep rupture performance of BFRP bars remains unclear. This study aims to investigate the effects of the pH value and temperature of the simulated pore solution of supplementary cementitious material (SCM) seawater sea sand concrete (SWSSC) subject to carbonation, on the creep rupture of BFRP bars. The pH value, chemical composition of pore solution, phase composition and pore structure of SCM concrete subject to natural carbonation have been characterized. The creep rupture performance of BFRP bars in simulated pore solutions have been tested at various pH values (9.0, 11.0 and 13.5) and temperatures (25 °C, 45 °C and 65 °C). A theoretical model for predicting the creep rupture strength of BFRP bars in air, simulated pore solution and real concrete environments has been developed and validated in comparison with experimental data in existing literature. Experimental results suggest that reducing the pH value (down to 10–11) and temperature of the pore solution can significantly improve the creep rupture performance of BFRP bars. The application of limestone calcined clay cement (LC³) concrete and concrete carbonation is promising in mitigating the alkaline corrosion effect on the creep rupture performance of BFRP bars by lowering pH values, as evidenced by the improvements of creep rupture strength at one million hours of OPC concrete, from 24.1 % to 50.3 % and 71.2 %, respectively.