Research
Geopolymers Program
Program Leader: Prof Arie van Riessen, Curtin University of Technology
Geopolymers are a class of inorganic polymers formed by the reaction between an alkali and an aluminosilicate source. These materials have a structure that gives geopolymers properties which make them an ideal substitute for Ordinary Portland Cement (OPC) in a whole range of applications. Many by-products produced by industry can be used as feedstocks for geopolymers, including fly ash, mine tailings and bauxite residues. This would have the advantage of using large volumes of waste material and also reduce the emissions of greenhouse gases associated with the production of Ordinary Portland Cement.
It is estimated that cement and concrete production worldwide produces 5-7 percent of total global greenhouse gas emissions. Geopolymer and other cement substitutes can reduce this figure by as much as 80 percent. In addition, geopolymer concrete has structural properties and fire and acid resistance that make it a durable material.
CSRP research has been investigating the microstructure of geopolymers and developing demonstration products for large scale applications of geopolymer concrete.
Achievements
- Two of Australia's first geopolymer concrete paths laid – one using a combination of two Australian fly ashes.
- Formation of a Geopolymer Alliance to bring together stakeholders to cooperatively develop mutually beneficial applications for geopolymer technology – with 13 founding members.
- Successful demonstration of mine backfill using geopolymer concrete as a replacement for OPC – large scale implementation would result in significant reductions in both energy usage and greenhouse gas emissions.
- Geopolymers with impressive physical properties successfully manufactured from Bayer residue – a new source material that opens up opportunities for utilisation of significant amounts of industry by-product.
- PhD student, William Rickard, in the top four presenters at the CRC Association's annual Showcasing Early Career Scientists event in 2009 for his research on fireproof geopolymers.
- Compilation of a comprehensive reference database of more than 500 refereed papers, conference presentations and theses.
- Publication of over 100 papers on CSRP's geopolymer technologies.
- The use of geopolymers to encapsulate lead, chromium (III), barium and silver to pass the US Environmental Protection Agency recommended toxicity characteristic leaching procedure (TCLP) test for landfills.
- Immobilisation of caesium, strontium and uranium in geopolymers to pass regulatory tests for radioactive nuclear waste has been demonstrated.
- Technique development for measuring stiffness during curing and processing windows for geopolymer pastes.
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Impacts
- Production of conventional concrete contributes an estimated two billion tonnes per year of global carbon dioxide emissions– being 5-7 percent of the world's GHG emissions or equivalent to 450 million cars! Since 2003, CSRP has been developing technologies and expertise in geopolymer concrete – which generates 80 percent less GHG emissions than conventional concrete.
- Geopolymers produce a more durable, stronger, acid resistant and fire resistant concrete – resulting in concrete products with longer service lives.
- Reduced power station waste to landfill. A major advantage of geopolymer concrete is that it can be made using "waste" feed stocks such as fly ash (from coal-fired power stations), mine tailings and bauxite (alumina) residues. Millions of tonnes each year of these potential feed stocks are currently being disposed of in large and costly containment facilities – which could instead be diverted to the more beneficial use of making geopolymer concrete products.
- Reduced need for land clearing for lime quarries – instead,"waste" feedstocks provide the necessary components to make geopolymers.
- Reduced energy consumption in cement kilns – no need to burn lime to make geopolymers.
- Fly ash based geopolymers exhibit remarkable fire resistance whilst also maintaining a high degree of mechanical strength– maintaining structural integrity in situations where conventional OPC fails.
- The toxicity characterisation leaching procedure (TCLP) is one of the four characteristics used to identify whether a particular hazardous waste is adequately immobilised in a solid to be used for landfill disposal. CSRP has been able to immobilise lead, chromium (III), barium and silver in a geopolymer matrix separately to pass the TCLP test for 1 percent by weight of the metal.
- Radioactive elements caesium and strontium have half-lives of about 30 years and are soluble in water, especially caesium. They therefore pose a significant threat to the biosphere if they are not immobilised in a solid to prevent leaching for at least 300 years. By using simulated caesium and strontium added as hydroxides it was possible to immobilise them in a geopolymer matrix containing up to 5 percent by weight of the equivalent
element. A regulatory test for high level radioactive borosilicate glass was used. Uranium was also similarly immobilised at levels of up to 2 percent by weight.
- Geopolymer concrete compositions passed two regulatory tests for toxicity leaching and immobilisation of radioactive elements– proving it to be a truly value-added product.
Completed Projects
More Information
Contact
Prof Arie van Riessen
Centre for Materials Research
Curtin University
p. 08 9266 7090
e. a.vanriessen@curtin.edu.au
