Green concrete put to the test in Sydney

A new type of environmentally-friendly concrete which generates just one third of carbon dioxide per tonne in production compared to traditional cement is being road tested in Sydney…quite literally.

Geopolymer concrete is a sustainable blend of concrete and industrial waste material from coal-fired power stations and steel manufacturing such as fly ash and blast furnace slag.

In addition to reusing material that will otherwise go into the waste pile, the sustainable concrete emits much less carbon dioxide in production than conventional concrete - up to 600kg per tonne less, according to experts at UNSW.

To test the geopolymer concrete’s durability, the City of Sydney has laid 15 metres of traditional concrete and 15 metres of Geopolymer concrete to replace a 30 metre section of roadway on Wyndham Street in Alexandria, NSW.

According to City of Sydney, the road provides the perfect conditions for the trial as it is a high traffic volume road that leads to Sydney Airport.

Nine sensors have been positioned under the concrete to monitor and compare how the Geopolymer concrete performs.

UNSW Sydney researchers and the CRC for Low Carbon Living (CRCLCL) will then use results from the trial to create the first set of industry guidelines for Geopolymer concrete.

City of Sydney Lord Mayor, Clover Moore, said the City was committed to finding new ways to lower carbon emissions.

“I’m proud that the City of Sydney was Australia’s first carbon-neutral local government and that we’re continuing to take significant steps to reduce our carbon footprint,” the Lord Mayor said.

“Projects like this Geopolymer trial can result in new products that make a real difference in slashing carbon emissions.

“With 70 percent of the concrete produced today going into pavements and footpaths, there’s great potential to further lower emissions from our operations.”

UNSW Sydney researchers will monitor the road performance for five years. Project lead Professor Stephen Foster, who is also UNSW’s Head of School of Civil and Environmental Engineering, described the trial as a “huge step forward”.

“This trial will help drive step change in the industry. Many concrete companies are already doing a lot to change, but this trial really gives it another push,” he said.

“Research into Geopolymer has been undertaken since the 90s, but it’s only now that it’s starting to be commercialised.

“While we’ll monitor the road performance for up to five years, a lot of the data collected in the first three to 12 months of this world-first trial will be used to confirm our models and strengthen our predictions.”

According to Foster, concrete contributes seven per cent of all greenhouse gas emissions. In 2018, the world produced about 4.1 billion tonnes of cement, which contributed about 3.5 billion tonnes of carbon dioxide.

“Alternative, low carbon dioxide concrete materials offer potential benefits in reducing the greenhouse gas emissions associated with conventional concrete,” he said.

“This trial is important because we need demonstration projects to accurately assess the performance of Geopolymer over time so that there can be broader uptake.”

Geopolymer concrete has the potential to put 400 million cubic tonnes of globally documented waste from the coal and steel industries to good use, and is a sturdy product to boot, experts said.

“Our collaboration with organisations such as the City of Sydney and the publication of the research findings will further de-mystify and promote the use of Geopolymer concrete in construction,” said Australian (Iron and Steel) Association and Ash Development Association executive director, Craig Heidrich.

“Geopolymer concrete has great engineering properties. It is a durable, high performance product that has a low carbon footprint when used in construction,” Heidrich added.

According to UNSW Associate Professor of Sustainability Research, Dr Tommy Wiedmann, if all concrete produced in one year was Geopolymer instead of traditional concrete, this would save 12,000 kilotonnes of carbon dioxide per year.

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