29Si NMR spectroscopy of silicate anions in hydrothermally formed C-S-H

Yoshihiko Okada, Hideki Ishida, Takeshi Mitsuda

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Abstract

Hydrothermal treatment of lime-silica mixtures under saturated steam pressures below 200 °C usually gives C-S-H as an initial product, which reacts further to give crystalline calcium silicate hydrates. In this paper, C-S-H was hydrothermally prepared using CaO and silicic acid at Ca/Si ratios of 0.3 to 2.0 and 120° to 180 °C for 2 h. The C-S-H was examined mainly using 29Si NMR by the magic angle spinning gate proton decoupling and cross polarization magic angle spinning methods. XRD for all of the C-S-H showed bands at 0.304, 0.280, 0.183, and 0.166 nm. NMR results showed that all of the C-S-H contained single chains of silicate union, which became progressively longer as the Ca/Si ratio decreased, i.e., as the system became richer in silica. This was independent of the preparation temperature. The 0.8 ratio preparations at 180 °C contained small amounts of double-chain structure of 1.1-nm tobermorite. The reaction processing in the lime-silicic acid mixtures is also discussed.

Original languageEnglish
Pages (from-to)765-768
Number of pages4
JournalJournal of the American Ceramic Society
Volume77
Issue number3
Publication statusPublished - 1994 Mar

ASJC Scopus subject areas

  • Ceramics and Composites

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