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

Aminu Bature Shinkafi, Morteza Khorami, Esmaiel Ganjian, Mark Tyrer

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26 Citations (Scopus)
270 Downloads (Pure)


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
JournalConstruction and Building Materials
Early online date18 Nov 2020
Publication statusPublished - 18 Jan 2021

Bibliographical note

NOTICE: this is the author’s version of a work that was accepted for publication in Construction and Building Materials. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Construction and Building Materials, 267, (2021) DOI: 10.1016/j.conbuildmat.2020.120446

© 2020, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International


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

ASJC Scopus subject areas

  • Materials Science(all)
  • Building and Construction
  • Civil and Structural Engineering


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