Monitoring and characterization of creation of geopolymers prepared from fly ash and metakaolin by X‐ray photoelectron spectroscopy method

Abstract

The formation of geopolymers from fly ash (FA) and metakaolin (MK) was investigated. The effect of different reactivity of FA and MK was studied by X‐ray photoelectron spectroscopy method. Geopolymer materials were obtained by an alkaline activation of aluminosilicate sources. The aim of this work is to develop methods for working properties prediction of geopolymer materials based on the starting materials. Selection of a geopolymerization scheme is found to be a key factor to realize a beneficial effect of improved reactivity. Finally, a descriptive model of the mechanism of geopolymer formation, taking into account the quality of starting materials was proposed. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 841–849, 2015

Influence of mechanical activation of fly ash on the properties of geopolymers investigated by XPS method

“…A small change in specific surface area was observed for milled fly ashes MH and MS, increase of their specific surface area was by approximately only 20% and 26%, respectively. In our X-ray photoelectron microscopy spectra, we observed differences in formation of geopolymers from four different sources-MH,MS, F and G. Progressive monitoring these samples showed that the formation of the polymer chain is best in geopolymer prepared The peak positions of atoms of MH and MS polymers do not change too much, but the spectrum changes its shape, suggesting formation of intermediate silanol SiAOH group and production of basic siloxo Si-O-Si group in accordance with literature [1,14]. Solidification of the four samples indicates a significant decrease of oxygen.…”

“…The peak positions of atoms of MH and MS polymers do not change too much, but the spectrum changes its shape, suggesting formation of intermediate silanol SiOH group and production of basic siloxo Si‐O‐Si group in accordance with literature . Solidification of the four samples indicates a significant decrease of oxygen.…”

“…The alumino‐silicate gel contains Al atoms with different coordination numbers. The coordination number of Al can cause different reactivity of materials . The shift at 78.0 eV means the rupture and rebuilding of Al–O interatomic bonds and this causes the changes in the geopolymer properties.…”

“…Solidification of the four samples indicates a significant decrease of oxygen. Peak positions of atoms of C, O, Si, and Al confirm condensation of orthosialat molecules via reactive groups of Si and SiAOAAlAOH, with formation and creating cyclo-tri-sialat structure and the formation of the poly-sialat chain (Figure 4) [1,14].…”

Evolution of geopolymer binders: a review

“…The negative charge of the aluminate groups is balanced by joining the alkali cations [15]. According to Davidovits [4], geopolymers has been described by the structural formula Mn[-(SiO 2 ) z -AlO 2 ) n .wH 2 O where M represents any alkali cations, z is 1, 2, 3, w is the number of water molecules, and n represents the degree of polycondensation.…”