2010 Volume 8 Issue 3 Pages 273-280
The carbonation of γ-Ca2SiO4 (γ-C2S) and mechanism of vaterite formation have been investigated by evaluating the crystal structures of both γ-C2S and vaterite. The samples used were autoclaved calcium silicate hydrate hardening bodies prepared from Ordinary Portland Cement (OPC), γ-C2S and α-quartz and then subjected to accelerated carbonation. The ratio of OPC to γ-C2S was varied. Ca2+ in both γ-C2S and vaterite was found to be coordinated to six O2-. In addition, both γ-C2S and vaterite have similar atomic arrangements of O2- and Ca2+ and Ca-O bond distances. Therefore, it is proposed that vaterite mainly forms from γ-C2S via a topotactic reaction during accelerated carbonation.