Coal waste creates fireproof concrete



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SYDNEY: A by-product from coal-fired power stations can be made into a stronger and much safer concrete with far less carbon dioxide emissions, researchers have found.

They say this technology could "revolutionise the world's building and construction industries" and they hope to move the technology towards a large-scale trial and commercialisation.

Materials scientist William Rickard and his colleagues from Curtin University, in Perth, used waste materials called 'fly ash' to create the concrete.

Fireproof concrete may save lives

"The main benefit of using fly ash polymer cements is that they maintain their strength up to 1,200ºC whereas traditional cements start losing their strengths at about 600ºC … In the event of a fire, a building using traditional cement can lose its strength and collapse.

Buildings with fly ash concrete would have a much better chance of surviving a fire, Rickard says. Even coating exposed structural steel with it would reduce the heat that goes through the steel and prevent combustion.

Each year there are approximately 100 fatalities and about 3,000 injuries from structural fires in Australia alone.

Rickard says another application is full replacement with fly ash cement in the building of tunnels. "In Europe there have been cases of tunnels collapsing during a fire … this technology has the potential to save lives there."

Cutting the world's carbon

Over 600 million tonnes of fly ash are produced globally each year, according to Rickard, as a by-product from coal-fired power stations. He says his new cement will "turn a waste product into something useful, stopping it just being dumped."

As well recycling, the fly ash cement will be good for the environment because it releases up to 80% less carbon dioxide than standard cement.

It could make a big different on a global scale. "[Currently] 5–8% of the world's carbon emissions come from the manufacture of traditional cement," says Rickard.

Other cements

Manufacture of traditional cement known as Portland cement or OPC requires that limestone be burnt into lime. But this new cement is different: "It's an inorganic polymer with a different chemistry than traditional cements because it is not calcium based," says Rickard.

"Production of one tonne of Portland cement has been found to release approximately one tonne of carbon dioxide," says Rickard. Rickard's cement requires less energy and the chemical reaction doesn't release carbon dioxide.

Adding fly ash in concrete is not a new concept. Rickard says the use of fly ash in geopolymer cement is based on a different concept. "In Portland cement fly ash is purely there as a filler, whereas in geopolymer cement fly ash is a critical component because it's where the strength comes from," says Rickard.