Influence of surface carbonation on the electrochemical chloride extraction of recycled aggregate concrete and sensitivity analysis

At present, applying ECE technology to existing concrete structures to enhance durability and service life is feasible. However, the combined effects of chloride salts and carbonation in marine environments introduce complex influence mechanisms on concrete structures treated with ECE, especially for reinforced concrete projects incorporating RCA. This paper studies the effect of different factors on the ECE of carbonated RAC. The effects include RCA quality and replacement rate, FA admixture, electrochemical parameters, etc. The results indicate that optimal dechlorination efficiency is observed at FA content of 10 %. Overall, increased replacement of RCA improves the dechlorination efficiency with a 26.19 % increase recorded at 100 % replacement ratio compared to NAC. After carbonation, the decomposition of hydration products such as C-S-H reduced the mechanical properties of concrete, but the extended carbonation duration enhanced the ECE effectiveness. With the extension of carbonation time to 28d, the dechlorination efficiency increases by 14.27 %. Longer times and higher energizing currents can enhance for ECE. Dechlorination efficiency of carbonated RAC increased by 42.8 % after 28d of chloride extraction, compared to 7d.Sensitivity analysis highlighted that the electrochemical parameters had the most significant effect on ECE effectiveness. The sensitivity of current density to dechlorination efficiency and the sensitivity of chloride extraction time to the [Cl⁻]/[OH⁻] are 0.241 and 5.418, respectively. This will contribute to improving the durability of RAC structures in marine environments and advancing low-carbon engineering.