29Si isotopic enrichment was used for acquisition of multiple 29Si magic-angle spinning (MAS) and cross-polarization magic-angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectra, in situ in an NMR probe, from a single sample of hydrating Ca3SiO5 (C3S). Data with excellent signal-to-noise ratios were obtained at 20, 50 and 75 °C, with minimal use of spectrometer time, and without the need for the quenching of multiple samples. Spectral line widths and polymer-chain lengths derived from the spectra had no detectable differences from experiments in which the quenching was carried out with propan-2-ol. Furthermore, the effects of the MAS technique on the hydration reaction appeared to be minimal. At 20 °C, the bulk hydrate initially produced was dimeric; at later stages of the reaction, polymerization occurred. Arrhenius energies of 35 and 100 kJ mol−1, respectively, were calculated for these two reactions. The cross-polarization (CP) spectra acquired throughout the hydration showed that at 20 °C, 2% of the hydrated monomeric Qo(H)species persisted from after the induction period through to the late stages of the hydration reaction; this indicates that this species is unlikely to result from surface hydroxylation of C3S; an upfield shift of this species occurred with increasing hydration, indicating a possible change of environment for the silicate species. The amount of Qo(H)produced was found to increase at higher temperatures. Potential mechanisms for polymerization were assessed and a model in which dimeric-silicate units are linked together by insertion of monomers (dimer → pentamer → octomer) was found to give the best fit to the observed data; these results support a dreierketten model for the structure of the hydrate.
Nuclear Magnetic Resonance Induction Period Surface Hydroxylation Isotopic Enrichment Nuclear Magnetic Resonance Study
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S. A. Rodger, G. W. Groves, N. J. Clayden and C. M. Dobson, J. Amer. Ceram. Soc.71 (1988) 91–96.CrossRefGoogle Scholar
R. Rassem, H. Zanni-Theveneau, C. Vernet, D. Heidemmann, A.-R. Grimmer, P. Barret, A. Nonat, D. Bertrandie, and D. Damidot, Proceedings of the 1st International Workshop on Hydration and Setting, Dijon, France, 3–5 July, 1991.Google Scholar
J. Rocha and J. Klinowski, J. Magn. Reson.90 (1990) 567–568.Google Scholar