Thermal character of geopolymers synthesized from class F Fly ash containing high concentrations of iron and α-quartz

Abstract

This article reports the thermal characteristics of geopolymers prepared with a class F fly ash containing 15 wt% iron oxide and 20 wt% α-quartz. The characterization techniques used included dilatometry, TGA, DTA, XRD, and SEM. Geopolymer specimens were prepared with nominal ratios of Si:Al=2.3 and Na:Al=0.85. Iron oxide in the fly ash precursor was found to play a critical role in the thermal expansion and morphology of geopolymers at temperatures >500°C. Volume changes of quartz on either side of the α-β phase transition cause only minor variations in thermal expansion. © 2008 The American Ceramic Society.