Influence of alkali activator type and proportion on strength performance of calcined clay geopolymer mortar

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Abstract

The global abundance of low purity kaolin clay and the low embodied energy associated with its calcination makes it a promising aluminosilicate source that will extend the application of geopolymers. In this paper, the compressive strength and microstructure of iron rich, calcined clay based geopolymer mortars activated by two forms of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solutions were studied and reported. The samples were cured either in the air or under sealed conditions. The result shows that the 28 days strength of the mortars achieved by reacting the calcined clay with hydrous sodium silicate powder, dissolved under normal atmospheric conditions and sodium silicate solution produced in a pressure reactor vessel are 0.5 MPa and 28.8 MPa respectively. The former produced a non-geopolymer mortar that has a discrete undensified and uncompacted structure with heavy presence of residual particles, thus, achieving a strength that is 1.7% of the latter. The functional group analysis reveals that the binding phase of the peak strength mortar is ferro sialate (Fe-Si-O-Al).
Original languageEnglish
Article number120446
Pages (from-to)(In-Press)
JournalConstruction and Building Materials
Volume(In-Press)
Early online date18 Nov 2020
DOIs
Publication statusE-pub ahead of print - 18 Nov 2020

Keywords

  • Calcined clay
  • sodium silicate
  • sodium hydroxide
  • geopolymer
  • mortar
  • compressive strength
  • microstructure

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