Issue 23, 2017

Mechanism of zinc oxide retardation in alkali-activated materials: an in situ X-ray pair distribution function investigation

Abstract

Alkali-activated materials are a new class of sustainable materials that can help supplant highly CO2-intensive ordinary Portland cement (OPC). Chemical admixtures and additives that manipulate the hydration and setting of OPC are readily utilized in the construction industry. However, for alkali-activated materials, the impact of these additives on the evolution of the atomic structure of the binder gel is largely unknown. Here, we utilize nano-ZnO (nanoparticles of zinc oxide), a known retarder for OPC hydration, and investigate its influence on the alkali-activation reaction in high and low calcium alkali-activated materials (slag and metakaolin systems, respectively). Using isothermal calorimetry and in situ X-ray pair distribution function analysis, the mechanism of nano-ZnO retardation in alkali-activated materials is uncovered, revealing that calcium plays a pivotal role in dictating whether nano-ZnO has an impact on the alkali-activation reaction. These results also provide important insight on the ability of slag and metakaolin-based alkali-activated materials to effectively immobilize zinc within the binder gel, which is of relevance to the waste solidification/stabilization community.

Graphical abstract: Mechanism of zinc oxide retardation in alkali-activated materials: an in situ X-ray pair distribution function investigation

Supplementary files

Article information

Article type
Paper
Submitted
12 Qun 2017
Accepted
22 Cig 2017
First published
22 Cig 2017

J. Mater. Chem. A, 2017,5, 11794-11804

Mechanism of zinc oxide retardation in alkali-activated materials: an in situ X-ray pair distribution function investigation

N. Garg and C. E. White, J. Mater. Chem. A, 2017, 5, 11794 DOI: 10.1039/C7TA00412E

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