In a lab in Western Sydney, crushed concrete aggregate — a mix of gravel, sand, and crushed rock — is poured into a chamber and injected with carbon dioxide (CO2).
The CO2 gives the product the same strength and durability as new concrete, according to engineer and Western Sydney University Professor Vivian Tam.
“It will be making use of the landfill waste and also making use of the carbon emissions,” she said.
“I like to turn waste into resources.
“I don’t believe that waste should be classified as waste because it’s just a matter of how you utilise it.”
Professor Tam says her product, CO2 Concrete, will be commercially viable as it represents a 10 per cent cost reduction compared to producing virgin concrete.
Test slabs of the concrete have been in the ground for a few years, including as a footpath at the Blacktown Animal Rehoming Centre.
According to Deakin University construction senior lecturer Reza Hosseini, the building industry tended not to use recycled concrete aggregate because it is seen to lack strength compared to virgin materials.
“Designers, engineers, and people who design buildings and structures don’t take the risk,” Dr Hosseini said.
“They simply recommend virgin materials.”
But Professor Tam said her recycled concrete aggregate typically had 70 per cent of the strength of new aggregate and her CO2 Concrete product had the same strength as virgin concrete.
Building for net zero
With construction responsible for at least 18 per cent of Australia’s carbon emissions, Dr Hosseini said concrete was the worst offender because making cement was very carbon intensive.
“The way that we produce cement, we need [a] high amount of energy,” Dr Hosseini said.
Many construction companies have made pledges to reduce their greenhouse gas emissions.
Lendlease aims to have net zero carbon emissions in 2025, and absolute zero emissions by 2040.
