α-C2SH can be synthesized by hydrothermal treatment lime and silicic acid for 2 h at 200 °C. When heated to 390-490 °C, α-C2SH dissociates through a two-step process to form an intermediate phase plus some γ-C2S. This appears to be a new dicalcium silicate different from known dicalcium silicates - α, α′L, α′H, β, and γ phase - and is stable until around 900 °C. At 920-960 °C, all the phases are transformed to the α′L phase. The intermediate phase has high crystallinity and is stable at room temperature. 29Si MAS NMR measurements indicate the possibility that it contains both protonated and unprotonated monosilicate anions. The intermediate phase that has passed through the α′ phase at higher temperature yields β-C2S on cooling. The intermediate phase is highly active, and completed its hydration in 1 day (w/s = 1.0, 25 °C). Among the crystalline calcium silicate hydrates with Ca/Si = 2.0, it is hillebrandite that yields β-C2S at the lowest temperature.
|Number of pages||6|
|Journal||Journal of the American Ceramic Society|
|Publication status||Published - 1993 Jul|
ASJC Scopus subject areas
- Ceramics and Composites