Multistep nucleation and growth mechanism of aluminosilicate gel observed by cryo-electron microscopy

Zhao Qing Tang, Felipe Basquiroto De Souza, Roger J. Mulder, Kwesi Sagoe-Crentsil, Wenhui Duan

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Although sodium aluminosilicate hydrate (NASH) gel governs the physicochemical properties of geopolymer concrete, its nucleation and growth mechanism remain poorly understood. Here, time-resolved cryogenic transmission electron microscopy (cryo-TEM), in addition to other characterization techniques, were applied to probe the nanostructural evolution of NASH gel from early age up to 7 days. We found that the nucleation and growth of NASH gel is not a one-step process and that intermediate phases precede the formation of the geopolymeric network. More specifically, we detected the formation of prenucleation clusters (~1–2 nm) in the first minute of geopolymerisation, which then agglomerated into partially polymerized globules (~15 nm). As geopolymerisation proceeded, these globules transformed into the more stable, highly polymerized NASH gel. These findings suggest the nucleation pathway of NASH can be more accurately depicted by non-classical nucleation theory, which paves the way for the development of more robust nanoscale models of geopolymer binders.

Original languageEnglish
Article number106873
Number of pages12
JournalCement and Concrete Research
Volume159
DOIs
Publication statusPublished - Sep 2022

Keywords

  • Calorimetry
  • Characterization
  • Cryo-TEM
  • Geopolymer
  • Metakaolin
  • Reaction
  • Spectroscopy

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