Structure refinement of fly ash in connection with its reactivity in geopolymerization

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

View graph of relations

Author(s)

Detail(s)

Original languageEnglish
Pages (from-to)350-359
Journal / PublicationWaste Management
Volume118
Online published11 Sep 2020
Publication statusPublished - Dec 2020

Abstract

It's an oversimplification to evaluate the reactivity of fly ash in geopolymerization using bulk elemental ratios like Si/Al. In this study, quantitative XRD by means of Rietveld refinement was employed to proportionate the mineral and glass phases of five fly ashes. The chemical environment of Si and Al in the fly ashes was investigated by 29Si and 27Al MAS NMR spectra. By counting the contributions of Al phase from mullite, the proportion of different coordination states of Al in the glass phase was speculated. The results reveal that the coordination number of Al is directly associated with the amount of alkali cations present in the glass phase for the most fly ashes, whereby higher the alkali content, the more four fold coordinated Al species are present in the system. Five and six fold coordinated Al as well as highly polymerized silicate species are also present in the glass structure of the fly ash. All these results point to an inherent inhomogeneous glass structure in fly ash. Despite that, a reactivity index derived from the NBO/T ratio (Non-Bridging Oxygen per Tetrahedral network former, e.g. SiO44-, AlO45-) modelled in a simplified glass setup, correlates well with the reaction heat of the geopolymers.

Research Area(s)

  • Fly ash, Geopolymer, Microstructure, Reactivity

Citation Format(s)

Structure refinement of fly ash in connection with its reactivity in geopolymerization. / Jin, Yu; Feng, Weipeng; Zheng, Dapeng; Dong, Zhijun; Cui, Hongzhi.

In: Waste Management, Vol. 118, 12.2020, p. 350-359.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review