Brisbane to follow 'green' footpaths to the future - Brisbane Times

Two years ago the idea of "green concrete" was new to the Queensland industry.

In June 2011 it was winning praise at the previous Queensland Government's Sustainable Industry Awards.

Now we're walking on it and every new footpath in Brisbane is set to use green concrete.

Brisbane councillor David McLachlan, who chairs the council's Field Services Committee, said green concrete could be provided at the same price and at the same time as regular concrete.

However it does not contain cement, dramatically cutting carbon emissions.

"In our context green concrete means reducing the amount of cement in the concrete, because there is a lot of heat used in the making of cement," Cr McLachlan said.

"So if you reduce the amount of portland cement content, you are reducing the amount of heat that is needed to produce its key components.

"And therefore you are reducing the amount of C02 that you are using," he said.

"You can use recycled water and you can use different materials in the aggregate."

"Portland" cement is made by roasting limestone and clay in giant kilns in a process that sends nearly a tonne of carbon dioxide skywards for every tonne of concrete that is made.

In its trials to produce 20 cubic metres of concrete Brisbane City Council saved 2.5 tonnes of carbon.

"So it is now being used in our footpaths and it reduces our carbon footprint," Cr McLachlan said.

"We produce hundreds of kilometres of footpaths and from now on it will be the standard concrete used in our footpaths."

Back in 2011, the Toowoomba company that designed the product, Wagners, estimated it could save 9.2 tonnes of carbon emisisons in every 300 square metre house slab.

It has not yet been trialled commercially for house slabs.

Wagners general manager Michael Kemp said in 2011 the company's carbon-free concrete used common waste products, with very little carbon, fly ash and slag from blast furnaces.