29Si MAS NMR spectroscopic investigation of alkali silica reaction product gels
| Autor: | R. James Kirkpatrick, Xiandong Cong, Sidney Diamond |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
Magic angle
Chemical shift Analytical chemistry Building and Construction Nuclear magnetic resonance spectroscopy Cristobalite chemistry.chemical_compound Nuclear magnetic resonance chemistry Yield (chemistry) Magic angle spinning Alkali–silica reaction General Materials Science Calcium silicate hydrate |
| Zdroj: | Cement and Concrete Research. 23:811-823 |
| ISSN: | 0008-8846 |
| DOI: | 10.1016/0008-8846(93)90035-8 |
| Popis: | 29 Si magic angle spinning NMR spectroscopy and 1 H 29 Si cross-polarization MAS results are reported for gels prepared by reactions of a nevada opal, Beltane opal, and cristobalite with KOH in the presence and Ca(OH 2 ). The extents of the reaction can be followed as functions of time. The opals react much more rapidly than cristobalite. In the presence of calcium, the predominantly Q 4 sites of the starting materials change to predominantly Q 2 and Q 3 sites. Q 1 sites are less abundant and in part transient. Cross-polarization experiments confirm that all the reaction products are hydrous. Poor signal to noise ratios for the cross-polarization experiments at room temperature and increased signal/noise at −80°C suggest that most of the protons are loosely bound at room temperature and may occur predominantly in water molecules. The chemical shifts of the Q 1 and Q 2 sites observed for these products suggest local environments suprisingly similar to those of the calcium silicate hydrate gel produced in portland cement hydration. Gel products produced in the absence of caclium yield broad peaks corresponding to Q 3 , Q 2 , Q 1 sites, but the spectra vary in a non-monotomic way with reaction time. |
| Databáze: | OpenAIRE |
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