A comprehensive review of calcium metasilicate(CaSiO3) polymorphs as low-carbon cementitious materials for CO2 sequestration

Calcium metasilicate (CaSiO3, CS)-based carbonatable materials present significant advantages, including reduced calcination temperatures, active CO2 sequestration during curing, and accelerated strength development. This comprehensive review systematically examines the structural characteristics of CS polymorphs (beta-CS, alpha-CS, and high-pressure phases), synthesis methodologies encompassing natural wollastonite extraction, solid-state sintering, and hydrothermal-calcination approaches, alongside detailed carbonation mechanisms. Comparative analysis reveals that alpha-CS demonstrates superior carbonation reactivity relative to beta-CS, attributed to its distinctive three-membered silicate ring structure that enhances structural vulnerability and facilitates elevated Ca2+ dissolution rates. The microstructural evolution during carbonation processes and the resulting mechanical properties are comprehensively discussed, elucidating how calcium carbonate precipitation and silica gel formation synergistically contribute to strength development. Applications as both primary cementitious materials and supplementary cementitious materials are critically evaluated. This analysis provides fundamental insights and technical guidance for developing next-generation low-carbon cementitious materials that support sustainable construction practices while contributing to global climate change mitigation strategies.