Bricks from waste

Scientists at the University of New South Wales in Sydney Australia have turned the ash waste from coal-fired power stations into a new range of high-strength, lightweight building materials.

The first 100 per cent ’made from waste’ bricks, pavers and aggregates are now coming off a production line at a plant in China. UNSW’s commercial arm, NewSouth Innovations, is also negotiating to license the technology in Australia, India, Indonesia, the US, and the Middle Eastern construction hubs of Dubai and Kuwait.

’The environmental consequences are enormous,’ said inventor Dr Obada Kayali, a senior lecturer in civil engineering at the university.

The new lightweight fly ash aggregate, known as Flashag, replaces quarried rocks which are usually mixed with cement to make concrete.

’The amount of building going on in China - and the pollution - is unbelievable. If we can reduce the use of cement as much as possible there that is a very big gain, not only for China but for the global environment,’ Dr Kayali said.

The 100 per cent fly ash bricks and pavers, known as Flash Bricks, are about 20 per cent lighter and stronger than their clay counterparts. This means that less steel and shallower concrete foundations are needed for the same sized structures.

Globally, coal-fired power generation has produced billions of tonnes of fly ash waste over the past century, with annual production now at about 800 million tonnes.

A small percentage of the world’s fly ash is already absorbed by the construction industry as an additive to cement or is mixed with clay in bricks. However, earlier fly ash aggregates have needed more cement, not less, to achieve the same strength, immediately losing much of the environmental advantage.

’My research was about finding a way to produce a lightweight aggregate from fly ash which used less cement - this is the big difference,’ said Dr Kayali.