Understanding geopolymer binder-aggregate interfacial characteristics at molecular level

Ming-Feng Kai, Jian-Guo Dai

Research output: Journal article publicationJournal articleAcademic researchpeer-review


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
Publication statusPublished - Nov 2021


  • 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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