The effects of calcium hydroxide and activator chemistry on alkali-activated metakaolin pastes

Karina M.L. Alventosa, Claire E. White

Research output: Contribution to journalArticlepeer-review

Abstract

The impact of calcium hydroxide as an additive in sodium hydroxide- and silicate-activated metakaolin pastes is presented with a primary aim to ascertain the specific effects of calcium on the reaction kinetics and phase formation. FTIR and XRD are employed to understand the interaction of calcium hydroxide (10 wt% replacement of metakaolin) in 1, 5 and 10 M NaOH-activated pastes (and equivalent molarity Na2SiO3-activated pastes), with a focus on its impact on the nanoscale properties of the sodium-alumino-silicate-hydrate (N-A-S-(H)) gel. In situ FTIR and ICC are used to assess the impact of calcium hydroxide on the reaction kinetics, including the rate of metakaolin dissolution and associated rate of N-A-S-(H) gel growth. It is found that calcium hydroxide is effective at accelerating the reaction kinetics of 5 M Na2SiO3-activated metakaolin due to the formation of an initial calcium-rich gel that promotes additional metakaolin dissolution and enhances N-A-S-(H) gel formation.

Original languageEnglish (US)
Article number106453
JournalCement and Concrete Research
Volume145
DOIs
StatePublished - Jul 2021

All Science Journal Classification (ASJC) codes

  • Building and Construction
  • Materials Science(all)

Keywords

  • Alkali-activated materials
  • Amorphous material
  • Calcium addition
  • Gel formation
  • Metakaolin

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