Synthesizing aragonite whisker-rich material through wet carbonation of ternesite-based clinker: Nucleation kinetics, microstructure evolution and reactivity

This study identifies a suitable precursor for preparing aragonite whisker-rich material (AWM) via carbonation. By subjecting ground ternesite-based clinker to an aqueous solution at 80 ℃ with continuous CO 2 injection for 2 h, high-aspect-ratio aragonite whiskers were synthesized, reaching 54.2 wt% in AWM and corresponding to a CO 2 sequestration capacity of 410.54 g/kg. The rapid dissolution kinetics of ternesite accelerated Ca 2 + release, enhancing the driving force for CaCO 3 nucleation and resulting in short rod-shaped aragonite crystals. Comparative carbonation experiments on C 2 S powder in varying sulfate solutions indicated that intrinsic sulfate species within ternesite promote aragonite formation. This is likely attributed to the specific adsorption of released SO 4 2- on CaCO 3 crystal planes, which inhibits calcite growth pathways. Elevated temperatures intensified this effect and extended carbonation allowed for the evolution into high-aspect-ratio structures, facilitating the outward migration of silica gel and enhancing AWM reactivity. Adding 20% AWM to cement significantly improved 28-day flexural and compressive strengths by 27.5% and 22.8%, respectively. A preliminary material-level carbon assessment indicated a potential gross CO 2 reduction of 16.2%. This work demonstrates the high-value utilization of industrial solid wastes and offers new perspectives on developing high-performance cementitious materials via carbonation.