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Using carbon to reduce the concrete carbon footprint


A recycled alternative aggregate that blends concrete with carbon dioxide may provide a more emissions-friendly solution to regular concrete aggregates.

With the use of virgin concrete still prevalent across Australia, Western Sydney University Associate Dean (Research and HDR), Associate Dean (International), Discipline Leader (Construction Management) and Professor in Construction Management, Vivian Tam has developed a recycled alternative that mixes carbon dioxide (CO2) to create an aggregate that is equally as strong as regular concrete and more environmentally friendly.

This recycled CO2 Aggregate is strong enough to replace virgin aggregate for concrete production in the construction of major buildings, while also using carbon dioxide in a positive manner – rather than its impact on greenhouse gas emissions.

Another major benefit of CO2 Aoncrete is its properties as a recycled aggregate, meaning it can turn construction waste, which often ends up in landfill, into new aggregates that are just as strong as their traditional counterparts.

Tam first explored recycled concrete alternatives while studying her PhD at City University of Hong Kong in 2005. Today, she is continuing the work she started 20 years ago and is currently received a provisional patent to commercialise the CO2 Concrete through Ecobond, a company that she has co-founded.

“The difference with a CO2 Concrete compared to other recycled concrete is that I’m injecting carbon dioxide into the recycled aggregate,” Tam told Quarry. “It’s an extra process before the mixing where we would carbonate the aggregate before the treatment.”

That process, according to Tam, is confidential. However, it is known that the CO2 Concrete equals the strength of virgin concrete and can save huge costs while reducing emissions. Her method also offers production of the aggregate quickly and efficiently.

“Based on the data that I collected in Sydney, the cost actually at the moment is 10 per cent cheaper than virgin concrete.” she said.

“Ultimately, the CO2 Concrete Ecobond produced actually has a matching strength of virgin concrete at this stage.

“Because of its strength, I cannot see why CO2 Concrete could not be adopted in any application that you would use for virgin concrete.”

CO2 is used alongside concrete to turn calcium hydroxide into calcium carbonate that features small crystals. A benefit of this method is an increase to the material’s strength while decreasing the need for water, leading to cost savings.

Tam said concrete companies have been impressed by the CO2 Concrete’s strength.

“I found that when I promote this product to any concrete companies, they are actually surprised that CO2 Concrete using recycled products can have a matching strength,” she said. “Internationally not many people have mastered this method – if any. The industry is most likely looking into the cost perspective – and the cost of CO2 concrete is low.”

The industry is continuing to seek out greener methods, and Tam hopes that Ecobond can tap into that space.

“That’s also bringing me the interest of further promoting this product as well,” she said.

For more information on Ecobond, visit www.ecobond.com.au


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