Understanding geopolymer binder-aggregate interfacial characteristics at molecular level

Ming-Feng Kai, Jian-Guo Dai

Research output: Journal article publicationJournal articleAcademic researchpeer-review

Abstract

The interfacial characteristics of geopolymer binder to aggregate composites are poorly understood, especially at molecular level. Herein, molecular models are developed to study, for the first time, the geopolymer-aggregate interface. Chemically, various forms of interfacial bonding are characterized, including Al-O-Si bonding through condensation reactions, Na[sbnd]O and H-bonding. An atomic-level interfacial transition zone (ITZ) is identified, attributed to the concentration of –OH groups. Increasing the Si/Al ratio of geopolymer is found to decrease the ITZ density, but have limited effect on the ITZ width. A heterogeneous diffusion characteristic occurs in geopolymer, due to the weak interfacial interaction. Mechanically, lowering the Si/Al ratio promotes the interfacial strength due to the stronger interfacial interaction and higher cross-linking degree in geopolymer. Under loading the interfacial fracture undergoes three stages: crack propagation, chain bridging (including aluminosilicate and ionic bridging) and breakage. The above atomic-level findings may facilitate a better design of geopolymer concrete in engineering.

Original languageEnglish
Article number106582
JournalCement and Concrete Research
Volume149
DOIs
Publication statusPublished - Nov 2021

Keywords

  • Chemical bonding
  • Heterogeneous diffusion characteristic
  • Interfacial fracture
  • Interfacial strength
  • Interfacial transition zone

ASJC Scopus subject areas

  • Building and Construction
  • Materials Science(all)

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