On the nature of structural disorder in calcium silicate hydrates with a calcium/silicon ratio similar to tobermorite
- BRGM, 3, Avenue Claude Guillemin, 45060 Orléans Cedex 2 (France)
- CRMD, UMR 6619 – CNRS, 1b rue de la férollerie, 45071 Orléans Cedex 2 (France)
- Laboratory of Environmental Geology, Research Group of Geoenvironmental/Engineering Division of Solid Waste, Resources and Geoenvironmental/Engineering Graduate School of Engineering, Hokkaido University, Kita 13 Nishi 8, Sapporo 060-8628 (Japan)
- Faculty of Integrated Arts and Sciences, The University of Tokushima, 1-1, Minami-Josanjima, Tokushima, 770-8502 (Japan)
- ANDRA, Centre de Meuse/Haute Marne, 55290 Bure (France)
- ISTerre, Grenoble University, CNRS, F-38041 Grenoble (France)
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 °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 ∼ 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 Å. 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.
- OSTI ID:
- 22220811
- Journal Information:
- Cement and Concrete Research, Vol. 52; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0008-8846
- Country of Publication:
- United States
- Language:
- English
Similar Records
Experimental determination of bulk modulus of 14 A tobermorite using high pressure synchrotron X-ray diffraction
Transformation of meta-stable calcium silicate hydrates to tobermorite: reaction kinetics and molecular structure from XRD and NMR spectroscopy