High-Resolution X-ray Diffraction and Fluorescence Microscopy Characterization of Alkali-Activated Slag-Metakaolin Binders

Authors

  • Susan A. Bernal,

    Corresponding author
    1. Department of Materials Science and Engineering, University of Sheffield, Sheffield, United Kingdom
    • School of Materials Engineering, Composite Materials Group, Universidad del Valle, Cali, Colombia
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  • John L. Provis,

    Corresponding author
    1. Department of Materials Science and Engineering, University of Sheffield, Sheffield, United Kingdom
    • School of Materials Engineering, Composite Materials Group, Universidad del Valle, Cali, Colombia
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  • Volker Rose,

    1. Advanced Photon Source and Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439
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  • Ruby Mejía de Gutiérrez

    1. School of Materials Engineering, Composite Materials Group, Universidad del Valle, Cali, Colombia
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Authors to whom correspondence should be addressed. e-mails: j.provis@sheffield.ac.uk and s.bernal@sheffield.ac.uk

Abstract

The effect of the activator concentration on the structure of alkali silicate-activated slag/metakaolin pastes is assessed through synchrotron radiation-based X-ray techniques. As main reaction products, both calcium aluminosilicate hydrate (C–A–S–H) and sodium/calcium aluminosilicate hydrate [(C,N)–A–S–H] type gels are formed in activated binders solely based on slag, along with the zeolitic products gismondine and garronite. In activated blended pastes, the inclusion of metakaolin in the binder hinders the formation of zeolite products, instead favoring the formation of a (C,N)–A–S–H type gel consistent with the activation of metakaolin in the presence of high concentrations of Ca. The formation of the two distinct binding products is confirmed by high-resolution X-ray fluorescence microscopy, where the “inner” products and the “outer” products have compositions consistent with (C,N)–A–S–H and C–A–S–H type gels, respectively. These results provide important new insights into the gel chemistry and micro/nanostructure of blended alkali-activated binder systems.

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