Bond behaviors between GFRP bars and CO2-cured seawater sea-sand concrete with sufficient carbonation

Given that seawater sea-sand concrete (SSC) structures reinforced with GFRP bars (GFRP-SSC) have great potential advantages in coastal infrastructure construction and renewal, CO2 curing for GFRP-SSC is proposed in this study. Herein, the CO2 uptake by CO2-cured SSC with sufficient carbonation is examined, as well as the pH levels in SSC. Additionally, in view of the significant role of the bond properties in ensuring their joint work, our primary focus is on evaluating the impact of CO2 curing on the bond behaviors between SSC and GFRP bars. The experimental results indicate that CO2-cured SSC exhibits a significant increase in CO2 storage capacity since it allows sufficient carbonation to occur. The pH in CO2-cured SSC can be reduced to below 9 at the age of 180 days. The average bond stress-slip curves clearly demonstrate that CO2 curing enhances chemical adhesion, mechanical interlocking, and friction at the interface between SSC and GFRP bars. The maximum gain in the interfacial bond strength caused by CO2 curing can exceed 100 %. Additionally, CO2 curing partially mitigates the adverse effects of increased w/b ratio in SSC or larger bar diameters on the bond strength. The simulation results indicate that the mBPE model and the CMR model can effectively describe the average bond stress-slip curves between CO2-cured SSC and GFRP bars.