Effect of carbonation curing on the microstructural evolution and mechanical properties of seawater-mixed calcium sulfoaluminate cements

The present study investigated phase evolution and mechanical properties of seawater-mixed calcium sulfoaluminate (CSA) cements with varying m -values from 0 to 2.0 under normal and carbonation curing at 10 % CO 2 concentration for 28 d. For normal-cured samples with m -values of 0 and 0.5, favorable formation of Kuzel's salt resulted in 160 % and 124 % higher chloride binding capacity, respectively, than that of sample with m -value of 2.0; however, the compressive strength of sample with lowest m-value was 67 % of that of sample with highest m -value, along with increased total shrinkage. Carbonation curing caused decomposition of AFm phases, leading to loss of chloride binding capacity across all samples, though minor physical binding was observed in samples with low m -values. Additionally, total shrinkage of carbonation-cured samples was mitigated up to 14 d, but carbonation-induced shrinkage eventually prevailed, resulting in increased total shrinkage and surface cracking in all samples, with severity depending on m -value. • Lower m -values in normal-cured samples enhanced chemical chloride binding by promoting the formation of Kuzel's salt. • Carbonation curing compromised chloride binding capacity by decomposing AFm phases. • Increasing m -value under normal curing simultaneously reduced total shrinkage and enhanced compressive strength. • Carbonation curing alleviated total shrinkage of samples up to 14 d of curing. • In carbonation-cured samples, a higher m -value induced severe surface cracking, impairing strength development.