Thermodynamic properties of sodium aluminosilicate hydrate (N-A-S-H)

Brant Walkley, Xinyuan Ke, Oday Hussein, John L. Provis

Research output: Contribution to journalArticlepeer-review

17 Citations (SciVal)

Abstract

This study presents for the first time a systematic investigation of the thermodynamic properties of sodium aluminosilicate hydrate (N-A-S-H), through dissolution of pure synthetic N-A-S-H gels. Changes to the chemical composition and gel structure of N-A-S-H were determinedviacharacterisation of the solid phase before and after dissolution by multinuclear solid state nuclear magnetic resonance spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, and X-ray diffraction measurements. The correlations between the bulk Si/Al ratio of the N-A-S-H phase and its thermodynamic properties were studied by characterisation of the aqueous phase and calculation of solubility constants. The solubility of synthetic N-A-S-H was compared with the solubility of metakaolin-based geopolymers with similar bulk Si/Al ratios. The solubility (log10 Ksp) of both the synthetic N-A-S-H gels and metakaolin-based geopolymers showed a close to linear correlation with the bulk Si/Al ratio of the phase. Lower solubility was observed for N-A-S-H gels and geopolymers with a higher bulk Si/Al ratio. This new insight is fundamental to understanding the physiochemical properties of geopolymers, and provides essential information for predicting their long-term stability and durability.

Original languageEnglish
Pages (from-to)13968-13984
Number of pages17
JournalDalton Transactions
Volume50
Issue number39
Early online date7 Sept 2021
DOIs
Publication statusPublished - 21 Oct 2021

Bibliographical note

Funding Information:
This work has been funded by the Engineering and Physical Sciences Research Council (EPSRC), UK, through grant EP/ P013171/1. The participation of XK was partly sponsored by a University of Bath Prize Fellowship. We wish to thank and acknowledge Professor Susan Bernal, School of Civil Engineering, The University of Leeds, for insightful discussions related to this work. We also wish to thank and acknowledge Dr Sandra van Meurs, Department of Chemistry, The University of Sheffield, for assistance in acquiring the NMR data and insightful discussions related to this work. We are also very grateful to the PQ Corporation for the provision of alkali silicate solutions for this experimental programme.

Funding Information:
This work has been funded by the Engineering and Physical Sciences Research Council (EPSRC), UK, through grant EP/P013171/1. The participation of XK was partly sponsored by a University of Bath Prize Fellowship. We wish to thank and acknowledge Professor Susan Bernal, School of Civil Engineering, The University of Leeds, for insightful discussions related to this work. We also wish to thank and acknowledge Dr Sandra van Meurs, Department of Chemistry, The University of Sheffield, for assistance in acquiring the NMR data and insightful discussions related to this work. We are also very grateful to the PQ Corporation for the provision of alkali silicate solutions for this experimental programme.

ASJC Scopus subject areas

  • Inorganic Chemistry

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