Compatibility studies between N-A-S-H and C-A-S-H gels: study in the ternary diagram Na2O-CaO-Al2O3-SiO2-H2O

I. Garcia-Lodeiro, A. Palomo, A. Fernandez-Jimenez, D. E. Macphee

Research output: Contribution to journalLiterature review

355 Citations (Scopus)

Abstract

Sodium aluminosilicate hydrate (N-A-S-H) gel, the main reaction product of the alkali-activated aluminosilicates, differs of the aluminium-modified calcium silicate hydrate (C-A-S-H) gel of PC pastes. Increasing the level of SCM to reduce PC content of binders are being considered to address reduction in CO2 emissions, activation of the additional SCM content by alkali activation represents a possible environmentally sustainable solution. Therefore, mixtures of C-A-S-H and N-A-S-H gels might be anticipated and the present study assesses the compatibility relationships between them.

Compositional diagrams are provided to indicate phase compositional ranges and the phase assemblages obtained under equilibrium conditions. In calcium-rich formulations (pH in excess of 12), C-A-S-H and C(2)ASH(8) form as stable phases. However, in the lime poor part of the diagram an amorphous gel (N,C)-A-S-H precipitates but its stability is dependent on system pH and available Ca. (N,C)-A-S-H gels are de-stabilised by Ca to give C-A-S-H gels in suitable systems. (C) 2011 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)923-931
Number of pages9
JournalCement and Concrete Research
Volume41
Issue number9
Early online date12 Jun 2011
DOIs
Publication statusPublished - Sep 2011

Keywords

  • CSH
  • TEM
  • stability
  • alkali activated cement
  • N-A-S-H
  • cement

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