Three-fold benefits of using CO2 to cure seawater sea sand concrete

Excessive CO2 curing of concrete may significantly increase the risk of steel corrosion, which limits the application of this technology in reinforced concrete. Considering the substantial potential advantages of seawater sea sand concrete (SWSSC) structures reinforced by fiber reinforced polymer (FRP) bars in coastal infrastructure, FRP-SWSSC is proposed to capture CO2 by means of carbonation curing in this study. The effects of long-term CO2 curing on the compressive strength, pore structure, interfacial transition zone, CO2 uptake and pH of SWSSC were examined. It is found that CO2 curing can achieve an increase of approximately 25% in both 28d and 56-d compressive strengths of SWSSC. Additionally, the porosity experiences a reduction of approximately 3%. The increased carbonation depth and higher CO2 uptake in CO2-cured SWSSC lead to significantly greater CO2 storage. Even after 28 days of additional water curing, the pH of CO2-cured SWSSC remains below 9, thus preventing any damage caused by the high pH environment to the mechanical properties and microstructure of embedded FRP bars. Therefore, CO2 curing of FRP-SWSSC offers three-fold great benefits: (1) improved SWSSC performance, (2) increased CO2 storage amount, and (3) reduced adverse effects of high alkaline concrete pore solution on embedded FRP bars.