An Australian research team found a way to recycle soft plastic into concrete – and it could have broader applications in construction

Plastic has been recycled into concrete in a new project. Image: Getty
  • Engineers from RMIT partnered with Australian recycling companies to make concrete out of soft plastics.
  • The concrete was used for Coles Horsham’s car park and a footpath in Frankston.
  • RMIT’s Jonathan Tran described the broader implications of this process for Australia’s construction industry.
  • Visit Business Insider Australia’s homepage for more stories.

RMIT engineers teamed up with Victorian-based recycling and engineering companies RED Group, Replas and SR Engineering to create concrete from soft plastic.

The engineering team, together with the three Aussie businesses, developed Polyrok – a plastic aggregate created from soft plastics. This aggregate was then added to the mix when concreting Coles Horsham’s car park and a footpath in Frankston.

It’s a way to recycle soft plastic, particularly after the federal government recently passed legislation that banned the export of waste overseas.

Red Group is behind the REDCycle recycling bins for soft plastics, which you can often find outside of supermarkets like Coles and Woolworths. Each day, Australians return two million pieces of soft plastic into those bins but the problem is that plastic bags, cling wraps and wrappers are challenging to recycle.

“Glass can be easily recycled and turned into things such as sand replacement, but plastic is much harder,” Dr Jonathan Tran, senior lecturer at RMIT’s Civil and Infrastructure Engineering department said in a statement.

Tran led the sustainable concrete project and told Business Insider Australia that while hard plastic – like milk bottles – can go into a household recycling bin, soft plastics can’t. He explained that soft plastics aren’t suited for sorting machines at recycling plants as they can get lodged in conveyor belts and potentially halt the recycling process. Instead, soft plastics end up in general waste.

“We have nowhere to recycle it,” Tran said. “We basically dump it into general waste [bins], it ends up in landfill and it’s really difficult to recollect.”

With this recycling process, he said soft plastics can be put to good use. The Coles Horsham car park alone saved more than 900,000 pieces of plastic from landfill.

“Every year Australia’s construction industry is pouring about 13 million cubic metres of concrete materials,” Tran said. “If we just use up to 20% of this aggregate in concrete by using this Polyrok, it could end up using pretty much all of this soft plastic waste that we collect.”

Diverting soft plastics from landfill

According to RMIT, it was the first time this technology has been used in an Australian commercial project. The project began in June 2020, with Tran adding that it was challenging to combine concrete and plastic.

“Mixing concrete and plastic is difficult, as the two don’t naturally bond,” he said in a statement. “Replas and SR Engineering came to RMIT because of our unique facilities to develop the best way to bond the two components together.”

The companies have since diverted more than 1.3 billion pieces of soft plastic from landfill, with the potential for 105,000 tonnes to be condensed into this new material each year.

“In the future, we’re hoping to explore the production of sustainable concrete structures using a new large-scale concrete 3D printer at RMIT’s Bundoora campus,” Tran said in a statement.

Beyond carparks, Tran sees this new material being used in a whole range of applications, such as sound barrier walls around highways (to protect communities from noise) and building bushfire shelters. It also signals a positive step for Australia’s construction industry.

Polyrok. Image: RMIT

Broader applications in Australia’s construction sector

Polyrok combined with concrete makes a lighter material that can also absorb sound and heat. Being lightweight makes the material easy to assemble (and disassemble) and can reduce both transportation and construction costs.

On top of that, the material can be recycled again if need be. For example, if you had a traditional wall that is broken down, you’d need to figure out how to recycle all the materials it was made of. But if the wall used the Polyrok material it can be processed and recycled again – giving it what Tran calls “a second life”.

Red Group considers recycling a circular process that requires opportunities for products to be made from recycled materials.

“There is a really great opportunity here for Australia to embrace recycling manufacturing, and in turn create more employment opportunities for the nation,” a Red Group spokesperson told Business Insider Australia. “In turn, it is vitally important that consumers understand the importance of a true circular economy, and the increasing need to create more robust markets for products made from recycled materials.”

The company ultimately wants to see the the use of recycled materials become more normalised.

“Our focus at the moment is driving a change in culture from people and councils purchasing products and roads made from virgin materials, to one where purchasing recycled goods is more commonplace,” the spokesperson added. “This is the key to successful recycling.”

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