Fireproof ash

The 13.5 million tonnes of fly ash produced each year by Australasia’s coal-fired power stations could become a valuable source material for fireproof concretes.


Research by William Rickard and his colleagues at the Cooperative Research Centre for Sustainable Resource Processing at Curtin University of Technology in Perth has shown that fly-ash-based geopolymers exhibit remarkable fire resistance while maintaining a high degree of mechanical strength.


The team has made geopolymers, a cement-like material formed by dissolving materials that contain silicon and aluminium, such as fly ash, in a highly alkaline solution for use in high-temperature applications such as fireproofing and building insulation.


Rickard said: ‘Because of their amorphous polymeric structure, geopolymers maintain structural stability to much higher temperatures than conventional concrete.’


About 46 per cent of the fly ash from power stations – worth some $120m (£75m) annually – is reused, with the greatest part employed as filler for cement.


For example, the concrete Seacliff Bridge between Sydney and Wollongong includes 25 per cent fly ash from the Eraring power station in the NSW Hunter Valley.


As well as using a waste product from burning coal in power stations and providing a strong construction material designed to insulate against fire, geopolymers also reduce greenhouse gas emissions.


Beyond reducing source material cost and lessening the amount of fly ash being dumped in landfill, making geopolymers produces 80 per cent less greenhouse gases than Portland cement.


Cement manufacture contributes five to eight per cent of the world’s greenhouse gas emissions.