Relative importance of Al(V) and reinforcement to the flexural strength of geopolymer composites

Devon M. Samuel, Andre Sutrisno, Waltraud M. Kriven

Research output: Contribution to journalArticlepeer-review


We prepared 1 cm × 1 cm × 10 cm geopolymer bars from sodium silicate and six commercial metakaolins, both unreinforced and reinforced with 20 wt% of 55-μm wollastonite (CaO·SiO2) needles, to evaluate the relative contributions of five-coordinated aluminum in the metakaolin and the presence of a reinforcing phase to the flexural strength of geopolymers. Two metakaolins, with about 20 at% and lower of five-coordinated aluminum content, did not react sufficiently with our processing method and could not be tested. The flexural strengths of the other four geopolymers were similar at about 11–14 MPa unreinforced and 22–29 MPa reinforced. The effect of reinforcement on flexure strength is more significant than the choice of metakaolin provided that the metakaolin is reactive. The geopolymerization reaction depends on the amount of five-coordinated aluminum present in the metakaolin and is the primary difference between the samples that reacted and those that did not react.

Original languageEnglish (US)
Pages (from-to)3452-3460
Number of pages9
JournalJournal of the American Ceramic Society
Issue number7
StatePublished - Jul 2021
Externally publishedYes


  • composites
  • geopolymers
  • processing
  • strength

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry


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