Solid-state Al and Si NMR characterization of hydrates formed in calcium aluminate-silica fume mixtures |
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Authors: | P Pena AH de Aza X Turrillas J Sanz |
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Institution: | a Instituto de Cerámica y Vidrio, C.S.I.C., C/ Kelsen, 5, 28049 Cantoblanco-Madrid, Spain b Instituto de Ciencias de la Construcción Eduardo Torroja, C.S.I.C., C/ Serrano Galvache, 4, 28032 Madrid, Spain c Instituto de Ciencia de Materiales, C.S.I.C., C/ Sor Juana Inés de la Cruz, 3, 28049 Cantoblanco-Madrid, Spain |
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Abstract: | Partially deuterated Ca3Al2(SiO4)y(OH)12−4y-Al(OH)3 mixtures, prepared by hydration of Ca3Al2O6 (C3A), Ca12Al14O33 (C12A7) and CaAl2O4 (CA) phases in the presence of silica fume, have been characterized by 29Si and 27Al magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopies. NMR spectroscopy was used to characterize anhydrous and fully hydrated samples. In hydrated compounds, Ca3Al2(OH)12 and Al(OH)3 phases were detected. From the quantitative analysis of 27Al NMR signals, the Al(OH)3/Ca3Al2(OH)12 ratio was deduced. The incorporation of Si into the katoite structure, Ca3Al2(SiO4)3−x(OH)4x, was followed by 27Al and 29Si NMR spectroscopies. Si/OH ratios were determined from the quantitative analysis of 27Al MAS-NMR components associated with Al(OH)6 and Al(OSi)(OH)5 environments. The 29Si NMR spectroscopy was also used to quantify the unreacted silica and amorphous calcium aluminosilicate hydrates formed, C-S-H and C-A-S-H for short. From 29Si NMR spectra, the amount of Si incorporated into different phases was estimated. Si and Al concentrations, deduced by NMR, transmission electron microscopy, energy dispersive spectrometry, and Rietveld analysis of both X-ray and neutron data, indicate that only a part of available Si is incorporated in katoite structures. |
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Keywords: | Cement and concretes Si-hydrogarnet Gibbsite 27Al MAS-NMR 29Si MAS-NMR Neutron diffraction |
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