In the first trial of its kind, the city of Sydney, Australia, has taken industrial waste from coal-fired power stations and steel manufacturing to create a new roadway made from environmentally-friendly geopolymer concrete.
Working with researchers from the University of New South Wales (UNSW), engineers at Australia’s largest city have replaced a section of roadway on Wyndham Street in the suburb of Alexandria to test the ‘green’ concrete’s durability. Made from fly ash and blast furnace slag, the new geopolymer concrete is a sustainable blend of concrete and recycled materials. Geopolymer generates just 300kg (661lbs) of CO2 per tonne of cement, compared to 900kg (1984lb) from traditional cement production. The carbon emissions savings is equivalent to the electricity used by an average household every two weeks. With 70% of the concrete currently being produced going into road pavements and footpaths, using products such as geopolymer concrete has great potential to further lower emissions from roadway operations.
As a major road leading to Sydney Airport, Wyndham Street’s high traffic volume provides the perfect conditions for the trial. Nine sensors have been positioned under the concrete to monitor and compare how the geopolymer concrete performs, and University of NSW researchers will monitor the road performance for up to five years. The UNSW team and the Cooperative Research Center for Low Carbon Living will use results from the trial to create the first set of industry guidelines for geopolymer concrete. Research has been undertaken since the 1990s, but it is only now that this concrete blend is being explored as a product that is not only better for the environment, but is also commercially viable. The low CO2 concrete has the potential to put the 400 million cubic tonnes of globally documented waste from the coal and steel industries to good use. While a small amount is currently used in construction, much of it is currently stored on site.
“This trial is a huge step forward and 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,” commented Professor Stephen Foster, head of the UNSW’s school of civil and environmental engineering, who is the project lead. “While we’ll monitor the road performance for up to five years, a lot of the data collected in the first 3 to 12 months of this world-first trial will be used to confirm our models and strengthen our predictions. Concrete contributes 7% of all greenhouse gas emissions and in 2018 the world produced about 4.1 billion tonnes of cement, which contributed about 3.5 billion tonnes of CO2. Alternative, low CO2 concrete materials offer potential benefits in reducing the greenhouse gas emissions associated with conventional concrete. 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.”