Structural characterization of C-S-H and C-A-S-H samples-Part II: Local environment investigated by spectroscopic analyses
- Clermont-Universite, Ecole Nationale Superieure de Chimie de Clermont-Ferrand, LMI, BP 10448, F-63000 Clermont-Ferrand (France)
- Commissariat a l'Energie Atomique, DEN, Marcoule, Waste Treatment and Conditioning Research Department, F-30207 Bagnols sur Ceze (France)
- Clermont Universite, UBP, Laboratoire des Materiaux Inorganiques, F-63000 Clermont-Ferrand (France)
Spectroscopic studies ({sup 1}H, {sup 23}Na and {sup 27}Al MAS NMR and Raman spectroscopy) have been used to characterize three series of C-S-H samples (0.8<Ca/Si<1.7): one C-S-H series, one aluminum inserted C-S-H series (named C-A-S-H series), and one sodium and aluminum inserted C-S-H series (named C-N-A-S-H series). Previous Rietveld analyses have been performed on the two first series and have clearly shown that (1) a unique 'tobermorite M defect' structural model allows to describe the C-S-H structure whatever the Ca/Si ratio and (2) the insertion of aluminum into the C-S-H structure led to the degradation of the crystallinity and to a systematic increase of the basal spacing of about 2 A regardless the Ca/(Si+Al) ratio (at a constant Al/Si ratio of 0.1). Spectroscopic investigations indicate that the main part of the Al atoms is readily incorporated into the interlayer region of the C-S-H structure. Al atoms are mainly inserted as four-fold coordinated aluminates in the dreierketten silicate chain (either in bridging or paired tetrahedra) at low Ca/Si ratio. Four-fold aluminates are progressively replaced by six-fold coordinated aluminates located into the interlayer region of the C-S-H structure and bonded to silicate chains. Investigation of the hydrogen bonding in C-S-H indicates that the main part of the hydrogen bonds is intra-main layer, and thus explains the low stacking cohesion of the C-S-H structure leading to its nanometric crystal size and the OD character of the tobermorite like structures. - Graphical abstract: The insertion of aluminum atoms into the C-S-H structure has been investigated by spectroscopic analyses ({sup 27}Al and {sup 1}H MAS NMR and Raman). The previously determined structural continuity, when increasing the C/S ratio from the C-S-H(I) type to the C-S-H(II) type, has been confirmed even in the presence of aluminum.
- OSTI ID:
- 21372428
- Journal Information:
- Journal of Solid State Chemistry, Vol. 182, Issue 12; Other Information: DOI: 10.1016/j.jssc.2009.09.024; PII: S0022-4596(09)00459-9; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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