New environmentally friendly plastics, bricks and concrete can be made by recycling the great quantities of waste ash left over when coal is burnt in thermal power stations, according to UNSW researchers.
Known as fly ash, only some of the waste material is presently recycled - the rest is dumped in landfill sites around the world. China alone produces more than 200 million tonnes a year of fly ash.
But three UNSW research teams are aiming to take the ash out of the waste stream and use it to produce new materials, easing the pressure on the planet's natural resources at the same time.
Details of their research projects will be presented today and tomorrow at the annual symposium of the UNSW Centre of Sustainable Materials Research & Technology (SMaRT Centre), with a focus on sustainable materials, processes and technologies.
The symposium brings together a distinguished international group of experts in sustainable materials, with a wide-ranging program that includes alternative steelmaking technologies, recycling of rubber tyres, sustainable replacements for fibreglass, improvements in product design and bio-based panel materials for furniture-making in South America.
A team led by Associate Professor Sri Bandyopadhyay, in the School of Materials Science and Engineering, is working out how to use fly ash to replace materials such as talc, calcium carbonate, quartz, mica, silica flour and various clays that are now widely used as fillers to add bulk or special properties to many polypropylene plastics.
These fillers can meet specific properties required by industries, such as light weight, high strength, corrosion resistance and the ability to be tailored to specific engineering applications.
For his doctoral research, team member Dr Akhmad Zaeni found that fly ash is cheaper than many other fillers, because is a waste material. Using fly ash samples obtained from two of Cement Australia's 11 thermal power stations, Dr Zaeni also found that fly ash is very light, meaning that smaller quantities are needed to replace calcium carbonate. It also has superior mechanical properties than some other fillers, adding stiffness to the end product.
One distinct disadvantage of fly ash is its dark grey colour - resulting in composites which can sometime be visibly unattractive. Dr Zaeni has worked out how to whiten fly ash to close the whiteness of calcium carbonate, increasing the value of the ash as a commodity material.
Meanwhile, in the UNSW School of Civil and Environmental Engineering, Professor Stephen Foster and doctoral student Tian Sing Ng are tackling the task of creating concrete that contains none of its usual main ingredient - Portland cement. A key ingredient of Portland cement is usually limestone (calcium carbonate), the mining of which disturbs large areas of land and cave systems.
Professor Foster notes that water is the only substance used more on the planet than concrete, the manufacture of which generates about 800kg of the greenhouse gas carbon dioxide for every tonne of cement produced.
His team is studying geopolymer concrete - an inorganic polymeric concrete that can be produced from waste materials such as fly ash, blast-furnace slags, clays and tailings.
Research has shown that geopolymer concrete may have some superior properties when compared to traditional concrete, such as high early strength, improved durability and low creep and shrinkage. The team is developing a systematic and scientific approach for designing of geopolymer concrete and testing a fibre-hybrid, light-weight, geopolymer concrete that provides for high compressive and tensile strengths.
Dr Obada Kayali and colleagues at the UNSW@ ADFA campus in Canberra have already developed bricks and building aggregate that can be made entirely from fly ash http://www.unsw.edu.au/news/pad/articles/2006/aug/fly_ash.html .
Dr Kayali is now turning his attention to what is now known as engineered cementitious composites - in effect, they are designer concretes that use unconventional fibres and ingredients to create tough and durable new concretes that resist cracking.
He will tell the symposium that he has explored the effect of high volume fly ash on the role of steel fibres and found that its use in fibre reinforced concrete has resulted in large increases in its mechanical characteristics.
SMaRT@ UNSW Symposium on Sustainable Materials, Processes and Technologies
Identify future pathways for reducing greenhouse gas impact of materials
WHEN: 9 and 10 September 2009.
WHERE: Building F8 - Lecture Theatre G02.
For information contact Susan Lundy: s.lundy@ unsw.edu.au - 02 9385 4426
About SMaRT@ UNSW:
The Centre for Sustainable Materials Research and Technology (SMaRT@ UNSW) brings together researchers from the Faculties of Science, Engineering, Built Environment and UNSW@ ADFA to work with industry on the development of innovative, sustainable materials and manufacturing processes.
The overall aim of the Centre is to develop innovative, sustainable materials and processes through world-class research, with strong emphasis on environmental and economic benefits.
The centre's website is here:
Bob Beale, UNSW Faculty of Science 0411 705 435 email@example.com