Experimental study on carbonation behavior of seawater sea sand recycled aggregate concrete

The carbonation behavior of seawater sea sand recycled aggregate concrete (SSRAC) was investigated in this study. Considering different added water, fine aggregates, and coarse aggregates, the specimens were divided into 12 groups for the accelerated carbonation test by 7 days, 14 days, and 28 days. Among them, river sand, sea sand, and mixed sand (the proportion of sea sand and shell sand was 4:1) were used as fine aggregates. The results show that the carbonation depths of concretes with different mixtures all increase over time. When the replacement ratio of recycled coarse aggregate (RCA) is not less than 50%, sea sand is the most suitable fine aggregate to acquire best carbonation resistance, while river sand is the worst. On the contrary, when the replacement ratio of RCA is not more than 30%, river sand is the most suitable fine aggregate, while sea sand is the worst. It can also be speculated that the most appropriate replacement ratio of RCA is 50% when sea sand is applied as fine aggregates in SSRAC. At the same time, 30% replacement ratio of RCA is appropriate when mixed sand is applied as fine aggregates in SSRAC.