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Heated Montmorillonite: Structure, Reactivity, and Dissolution

  • Nishant GargEmail author
  • Jørgen Skibsted
Conference paper
Part of the RILEM Bookseries book series (RILEM, volume 10)

Abstract

The dehydroxylated form of the principal 1:1 clay, kaolinite, known as metakaolin, has been widely studied in terms of its structure and reactivity. However, detailed information on the dehydroxylation of the abundant 2:1 clay, montmorillonite, is lacking in this respect. Three montmorillonites, calcined at various temperatures have been characterized by solid-state 29Si MAS NMR. The dehydroxylation (600 – 800 °C) results in progressive distortion of the SiO4 tetrahedra, followed by crystallization of inert, stable phases at higher temperatures. The dissolution kinetics of a structurally pure montmorillonite, SAz-2, calcined at two different temperatures are found to be in good agreement with its pozzolanic reactivity established in an earlier study. It is also found that SAz-2, calcined at its optimum calcination temperature of 800 °C, undergoes incongruent dissolution reaching a molar Si/Al ratio of 3.7 in a 0.1 M NaOH solution after one day of dissolution. It has been reaffirmed that both the degree of dehydroxylation and the type of structural phases (Q3/Q4) have a significant impact on the reactivity of the calcined montmorillonite. The clear identification of inert phases and reactive sites by solid-state NMR may have major implications in the utilization of not only montmorillonites but also other calcined clays.

Keywords

Dissolution Kinetic Octahedral Sheet Supplementary Cementitious Material Incongruent Dissolution Optimum Calcination Temperature 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Notes

Acknowledgments

The Danish National Advanced Technology Foundation is acknowledged for the financial support to the SCM project.

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Copyright information

© RILEM 2015

Authors and Affiliations

  1. 1.Department of Chemistry and Interdisciplinary Nanoscience, Center (iNANO)Aarhus UniversityAarhus CDenmark

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