The role of zinc in metakaolin-based geopolymers

Lei Wang, Daniel A. Geddes, Brant Walkley, John L. Provis, Viktor Mechtcherine, Daniel C.W. Tsang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

30 Citations (Scopus)

Abstract

Geopolymers are low-calcium, sustainable cementitious materials. The role of Zn, a known retardant used in Portland cement, in geopolymer systems is not well understood. This study scrutinises the effect of Zn on metakaolin-based geopolymer reaction mechanisms and kinetics, and investigates the incorporation mechanism of Zn in geopolymer gels. Isothermal calorimetry and X-ray diffraction analyses show that substitution of ZnO (20 mol% c.f. metakaolin) significantly hinders reaction, likely due to preferential formation of a Na/K-Zn containing phase. Solid-state nuclear magnetic resonance spectroscopy shows that Zn2+ partially substitutes for Na+/K+ in charge-balancing sites within the geopolymer gel. Setting time and leaching tests show that the retarding effect of Zn on reaction kinetics is significantly greater in Na-activated geopolymers compared with K-activated geopolymers, whereas Na-activated geopolymers exhibit superior fixation capacity to Zn. A lab-scale experiment demonstrates that metakaolin-based geopolymers are promising candidates for the stabilisation/solidification of Zn-rich hazardous waste.

Original languageEnglish
Article number106194
JournalCement and Concrete Research
Volume136
DOIs
Publication statusPublished - Oct 2020

Keywords

  • Alkali-activation
  • Geopolymer
  • Hazardous waste immobilisation
  • Reaction kinetics
  • Retarding mechanism
  • Zn leachability

ASJC Scopus subject areas

  • Building and Construction
  • Materials Science(all)

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