A feasibility study of using low-alkalinity seawater sea sand concrete to improve the long-term bond performance of the BFRP bar in the seawater environment

BFRP bar has been recognized as one of the most promising alternative reinforcements to address the chloride-induced corrosion of steel bar-reinforced concrete structures in the marine environment. However, the high alkalinity of normal concrete is aggressive to BFRP bars, affecting their long-term bond performance. To address this issue, the bond durability performance of BFRP bar-reinforced low-alkalinity seawater sea sand concrete (SWSSC) after aging in seawater was investigated using the central pull-out test. Scanning electron microscopy (SEM) was also used to characterize the microstructure of BFRP bar-SWSSC interfaces. The findings revealed that since the corrosion of BFRP bars in low-alkalinity SWSSC is substantially lower, the bonding durability performance of BFRP bar-reinforced low-alkalinity SWSSC is significantly higher than that of ordinary SWSSC pull-out specimens. After 270 days of accelerated aging in seawater at 55°C, bond strength retention in normal SWSSC specimens reduces to about 73%, whereas that of low-alkalinity SWSSC specimens improves to about 107-110%. The energy consumption and carbon emissions of low-alkalinity SWSSC are less than half of those of normal SWSSC.