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On the nature of structural disorder in calcium silicate hydrates with a calcium/silicon ratio similar to tobermorite

Abstract : Four calcium silicate hydrates (C-S-H) with structural calcium/silicon (Ca/Si) ratios ranging from 0.82 +/- 0.02 to 0.87 +/- 0.02 were synthesized at room temperature, 50, 80, and 110 degrees C. Their structure was elucidated by collating information from electron probe micro-analysis, transmission electron microscopy, extended X-ray absorption fine structure spectroscopy, and powder X-ray diffraction (XRD). A modeling approach specific to defective minerals was used because sample turbostratism prevented analysis using usual XRD refinement techniques (e.g. Rietveld analysis). It is shown that C-S-H with Ca/Si ratio of similar to 0.8 are structurally similar to nano-crystalline turbostratic tobermorite, a naturally occurring mineral. Their structure thus consists of sheets of calcium atoms in 7-fold coordination, covered by ribbons of silicon tetrahedra with a dreierketten (wollastonite-like) organization. In these silicate ribbons, 0.42 Si per bridging tetrahedron are missing. Random stacking faults occur systematically between successive layers (turbostratic stacking). Layer-to-layer distance is equal to 11.34 angstrom. Crystallites have a mean size of 10 nm in the a-b plane, and a mean number of 2.6-2.9 layers stacked coherently along the c* axis. (C) 2013 Elsevier Ltd. All rights reserved.
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Contributeur : Anne-Marie Pouget <>
Soumis le : mercredi 16 juillet 2014 - 12:07:30
Dernière modification le : vendredi 17 juillet 2020 - 17:09:03

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Sylvain Grangeon, Francis Claret, Catherine Lerouge, Fabienne Warmont, Tsutomo Sato, et al.. On the nature of structural disorder in calcium silicate hydrates with a calcium/silicon ratio similar to tobermorite. Cement and Concrete Research, Elsevier, 2013, 52, pp.31-37. ⟨10.1016/j.cemconres.2013.05.007⟩. ⟨hal-01024533⟩

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