Development of highly carbonation-effective calcium silicates (β-C₂S): Phase evolution, microstructure, and carbonation mechanisms

Carbonation of calcium silicate (CS) minerals to produce hardened construction materials has attracted increasing interest, but the efficiency of conventional CS minerals is low. This study prepared a highly reactive β-C₂S derived from a C-S-H precursor through hydrothermal synthesis. The potential CO₂ uptake ability, product compositions, microstructural characteristics, and carbonation mechanisms of the hydrothermal β-C₂S were investigated. The results showed that the hydrothermal β-C₂S achieved 3.7 times higher carbonation efficiency compared to the reference β-C₂S prepared by traditional calcination and reached a carbonation degree of 56.1 % within 10 min. Its high reactivity was attributed to large specific surface area, unique thin lath structure, and fine grain size. The novel type of C-S-H produced, special thin lath structure evolution and sufficient ACC led to an almost complete carbonation degree of hydrothermal β-C₂S. The developed carbonation process could be used to valorize recycled concrete waste which contains a large amount of C-S-H.