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Studies using Al MAS NMR of AFm and AFt phases and the formation of Friedel's salt |
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| Authors: | MR Jones DE Macphee G Hunter R Talero |
| Affiliation: | a Department of Civil Engineering, University of Dundee, Dundee DD1 4HN, Scotland, UK b Department of Chemistry, University of Aberdeen, Aberdeen AB24 3FX, Scotland, UK c Division of Physical and Inorganic Chemistry, School of Life Sciences, University of Dundee, Dundee DD1 4HN, Scotland, UK d Instituto de Ciencias de la Construcción “Eduardo Torroja,” Madrid, Spain |
| Abstract: | This paper describes the application of the magic angle spinning (MAS) NMR spectroscopy to study the chemical environment of 27Al-bearing phases in Portland cement-based concrete. A specific methodology is described that allows reliable spectra to be determined for combinations of different types of cements and fillers (in this case, Portland cement, fly ash, slag, silica fume, metakaolin and limestone filler). As well as the study of ‘molecular structure’ of cement matrix, the paper reviews the mechanism of Friedel's salt formation in cement systems. Mechanisms based on ion exchange of chloride for hydroxide in hydroxy-AFm and on chloride absorption on formation are discussed. Finally, the nature of the chloride/hydrate binding phenomena are described to provide a reasonable robust and fundamental picture of the role different cements can play in the provision of overall concrete durability to chloride ingress from a chemical perspective. |
| Keywords: | MAS NMR spectroscopy Portland cement Chloride Monosulphate Friedel's salt formation |
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