MgCl 2 -mediated crystallization of aragonite whiskers from carbonated calcium silicates

This study examines the effect of MgCl 2 (0–10%) as a crystal modifier on the carbonation behavior of C 3 S and [Formula: see text]-C 2 S, with particular emphasis on aragonite whisker formation. The results show that early-stage carbonation is strongly suppressed by MgCl 2 . This inhibitory effect was observed for both C 3 S and [Formula: see text]-C 2 S, where the carbonation reaction extent was reduced in a dosage-dependent manner. This inhibitory effect, however, diminished after 72 h, with the final DOCs converging to approximately 53–55%. MgCl 2 was found to promote aragonite formation over calcite. SEM analysis revealed the development of high-aspect-ratio aragonite whiskers, which formed interconnected networks at higher MgCl 2 concentrations. The strategy of using MgCl 2 to inhibit calcite nucleation and template aragonite growth paves the way for developing high-performance, carbonated cementitious materials reinforced by in-situ grown aragonite whiskers.