Confirmation of Candidature - Candidate : Adrian Rex

One of the legacies left from over 100 years of burning coal for power generation is the large volumes of Coal Combustion Products (CCPs) stored in ash repositories (over 600M t of CCPs in Australia, and over 2,000M t in the USA).  These repositories are, in the main, unlined and have resulted in some releasing potentially toxic materials into the groundwater.  CCPs can be harvested from the ash repositories (hence the use of the term "Harvested Ash" in this project) and beneficially used (as supplementary cementitious materials, road stabilisers, in mine backfill, etc.).  However, such is the volume of CCPs being stored that ash repositories will be a feature of the landscape for many years.  In the short term there is a need to seal ash repositories to prevent the leaching of potentially toxic materials into the groundwater.
The aim of this project is to investigate the potential to cost effectively produce a geopolymer mortar using unprocessed Harvested Ash (HA) as a precursor material which can be used to seal the base of the ash repository.  The CCPs in the ash repository can then be harvested economically over a long period of time for beneficial use.

Current (limited) research into geopolymers using HA has concentrated on developing a mortar with similar properties to one produced using cement as a binder.  The HA is ground to increase fineness, and the mortar cured at elevated temperatures to achieve these properties.  However, the most important properties of a sealant mortar are durability and low permeability rather than high compressive strength, as well as a low-cost precursor (hence the use of unprocessed HA).

This research will commence with defining the characteristics (mechanical, chemical, and physical) and reactivity of unprocessed HA sourced from several ash repositories across Australia.  These characteristics (for example, the proportion of amorphous phase, and the fineness) will be used to design a range of geopolymer mortars with properties suitable for use as a sealant.  The range of mortars will include geopolymers produced from liquid activators, cured at room temperature, and from different precursor (unprocessed HA) sources.  The mechanical, chemical, and physical properties (for example the workability, setting time, compressive strength, mineralogy, and shrinkage) of these geopolymer mortars will be assessed.  Statistical analysis of the precursor characteristics and the mortar properties will be used to refine and further develop the geopolymer precursor Reactivity Index.  The leachability and permeability of the geopolymer mortars will be investigated to understand their suitability for use as a sealant grout.

For more information, please email the Graduate Research School or phone 0746 311088.