2017 Volume 71 Issue 1 Pages 48-55
This study was performed to generate the highly reactive β-C2S by heating the calcium silicate hydrates（C-S-H）with high CaO/SiO2 molar ratio（C/S ratio）at low temperature. Therefore, C-S-H samples were synthesized by double-decomposition method under various conditions. Then, the synthesized C-S-H samples were heated at 600℃, and the heated samples were hydrated. The synthesized C-S-H, the heated samples, and the hydrated samples were analyzed phase composition, chemical composition and BET specific surface area. As a result, the calculated C/S ratio of C-S-H with targeted C/S ratio＝2.0 was about 0.9；however, the C/S ratio of the same C-S-H analyzed by XRF was about 1.2. When this C-S-H was heated at 600℃, wollastonite which has a C/S ratio of 1.0, β-C2S and α-C2S were generated. It may be suspected that the C-S-H with C/S ratio of 1.0 and the C-S-H with C/S ratio of 2.0 were coexisted in the synthesized C-S-H, and these C-S-H phases were changed to wollastonite and C2S respectively. Furthermore, BET specific surface area of the heated C-S-H sample was comparable with the literature value of the highly reactive β-C2S, and the calcium hydroxide was not generated after hydration. Therefore, it was concluded that the C2S generated in this study was likely the highly reactive C2S.
