Soft plastics become sustainable concrete for Coles carpark

RMIT engineers have partnered with Victorian recycling organisations Replas, RED Group and SR Engineering to develop a concrete material made from lightweight recycled plastic. Polyrok — a sustainable aggregate alternative — has enhanced durability and is lighter to work with than traditional concrete.

Australians return 1.3 million pieces of soft plastic per day via REDCycle recycling bins, but cling wraps and plastic bags have been a problematic plastic to recycle. With new legislation to phase out soft plastic exports taking effect only last week, this project highlights an innovative solution to the problem.

RMIT’s Dr Jonathan Tran and his team worked with industry to create Polyrok — a plastic aggregate made from soft plastics — which was used in the concreting of Coles Horsham’s carpark and a footpath in the City of Frankston.

Dr Tran said his team were able to identify the best strategy to design the concrete mix, optimising the strength and acoustic energy absorption of the material.

“Glass can be easily recycled and turned into things such as sand replacement, but plastic is much harder,” he said.

“Mixing concrete and plastic is difficult, as the two don’t naturally bond.

“Replas and SR Engineering came to RMIT because of our unique facilities to develop the best way to bond the two components together.”

RMIT researchers used X-ray computed tomography to design optimal strength and acoustic energy absorption.

Dr Tran said the opportunity to work with industry and create a considerable impact to society was a rewarding experience.

“Since the partnership, our industry partners Replas, Red Group and Coles have diverted over 1.3 billion pieces of soft plastic from landfill,” he said, adding that there is the potential for 105,000 tonnes of soft plastics to be converted into the dense plastic aggregate every year in a local factory in Melbourne.

The Coles carpark in Horsham saw over 900,000 pieces of plastic packaging saved from landfill and incorporated into the concrete.

“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,” Dr Tran concluded.