Compositional effects and microstructure of fly ash-based geopolymers

© 2001 Dr. John W. PhairIn the context of the concrete industry, geopolymers are an added-value approach to decommodifying the application of Portland cement-based construction materials. In particular, fly ash-based geopolymers are attracting growing interest due to their low cost, environmental advantage and readily available feedstock that allows them to be produced en masse. The development of geopolymers for construction applications, stabilisation technologies, fire resistant panels and a host of other applications, is still relatively new and therefore requires considerably more research. Materials science is one approach which can offer considerable insight into the properties and behaviour of geopolymers as a function of composition, and can also explain the reasons for these properties, based on a vast repository of scientific observations. Thus this approach gives an objective basis for collecting meaningful information on fly ash-based geopolymers which will greatly benefit the manufacturing and process design for any application. This thesis reports the analysis and development of experimental methods typical in the fields of materials science and surface chemistry to describe the microstructure and material properties of fly ash-based geopolymers. An emphasis is placed on describing the microstructure of fly ash-based geopolymers as it remains an ongoing objective of material scientists to link microstructural features to the material properties and macrostructure as a function of composition. More specifically, this thesis explores the positive effect of adding zirconia to fly ash-based geopolymers including the mechanism of incorporating zirconia within the matrix. This thesis also examines the fundamental surface chemistry associated with the inclusion of zirconia. Important processing variables of geopolymer synthesis are highlighted and their influence on the immobilisation of heavy metals is examined. Finally, the advantages of using an alternative alkali activator, sodium aluminate, is reported for both micro and macroscopic properties