Mechanism of zinc oxide retardation in alkali-activated materials: an in situ X-ray pair distribution function investigation. Issue 23 (29th March 2017)

• Record Type: Journal Article
• Authors: Garg, Nishant; White, Claire E.
• Is Part Of: Journal of materials chemistry. Volume 5:Issue 23(2017)
• Page Start: 11794
• Page End: 11804
• Publication Date: 2017-03-29
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c7ta00412e
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : Using in situ X-ray PDF, we elucidate the crucial role of calcium in the retardation mechanism of zinc oxide. 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.