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

8 Citations (SciVal)


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
Issue number39
Early online date7 Sept 2021
Publication statusPublished - 21 Oct 2021

ASJC Scopus subject areas

  • Inorganic Chemistry


Dive into the research topics of 'Thermodynamic properties of sodium aluminosilicate hydrate (N-A-S-H)'. Together they form a unique fingerprint.

Cite this