Journal
CEMENT AND CONCRETE RESEARCH
Volume 42, Issue 11, Pages 1534-1548Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.cemconres.2012.07.005
Keywords
Calcium-silicate-hydrate (C-S-H); X-ray diffraction; Crystal size; Crystal structure
Funding
- King Abdullah University of Science and Technology (KAUST) [KUS-l1-004021]
- U.S. DOE, Argonne National Laboratory [DE-AC02-06CH11357]
- Division Of Earth Sciences
- Directorate For Geosciences [836402] Funding Source: National Science Foundation
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Low-Q region Rietveld analyses were performed on C-S-H synchrotron XRD patterns, using the software MAUD. Two different crystal structures of tobermorite 11 angstrom were used as a starting model: monoclinic ordered Merlino tobermorite, and orthorhombic disordered Hamid tobermorite. Structural modifications were required to adapt the structures to the chemical composition and the different interlayer spacing of the C-S-H samples. Refinement of atomic positions was done by using special constraints called fragments that maintain interatomic distances and orientations within atomic polyhedra. Anisotropic crystallite size refinement showed that C-S-H has a nanoctystalline disordered structure with a preferred direction of elongation of the nanocrystallites in the plane of the Ca interlayer. The quality of the fit showed that the monoclinic structure gives a more adequate representation of C-S-H, whereas the disordered orthorhombic structure can be considered a more realistic model if the lack of long-range order of the silica chain along the c-direction is assumed. (C) 2012 Elsevier Ltd. All rights reserved.
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