CO₂ Capture of Concrete Waste Fines Through Wet Carbonation Under Seawater

Abstract

The growing concern over the increase in atmospheric CO₂ concentrations has led to the development of innovative methods for its storage and utilization. One promising approach is to store CO₂ in seawater, which can dissolve and store large amounts of CO₂. Recent technological advances have facilitated the rapid storage of CO₂ in concrete waste through wet carbonation. Therefore, combining these two approaches has been proposed to achieve effective CO₂ storage while also addressing the issue of concrete waste. In this study, we investigate the feasibility of wet carbonation of concrete waste fines under seawater, compared to pure water, for CO₂ capture. The experimental results indicated that seawater eluted a considerable amount of calcium and other elements from concrete waste, which were approximately 2–3 times higher than those in deionized water. However, the concentration of Si dissolved from cement paste carbonated in seawater was found to be lower than that in deionized water. Furthermore, the phase assemblage evolution in cement paste during wet carbonation in seawater exhibits a similar trend to that in deionized water but with a faster rate of hydrated phase decomposition. Wet carbonation of concrete waste in seawater exposure results in the emergence of new phases in concrete, including Friedel's salt and halite. The rapid decomposition during wet carbonation in seawater increases the amorphous phase in cement paste, even though the decomposition of C-S-H is completed. Moreover, wet carbonation in seawater was observed to sequester a larger amount of CO₂ in both the concrete waste and solution compared to deionized water. These findings provide valuable insights into the potential of seawater for carbon capture and utilization and contribute to the development of efficient and effective CO₂ capture technologies.