THE IMPORTANCE OF FLY ASH PROPERTY IN THE MANUFACTURE OF GEOPOLYMERS

Three typical Class Ffly ashes obtained from different Australian power stations were characterized and used to manufacture geopolymer pastes, by activation with NaOH and Na2O center dot 1.5SiO(3) solutions. The particle size distribution and surface area of fly ash are tested to be substantially different when its source varies. The Rietveld refinement XRD shows that the three fly ashes contain different amounts of amorphous phases. By examining the compressive strengths of their resulting geopolymer pastes under different ageing conditions, the surface areas and the amount of amorphous phase are unlikely sufficient to interpret their reactivity under the geopolymerization conditions. More important factors seem to relate to the glass chemistry of fly ash. This preliminary work suggests the requirement of performing more fundamental work on feedstock characterization for the engineered geopolymer manufacturing.