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Melbourne to become a plastic road test bed

May 30, 2023

Melbourne and nine of its suburban and regional councils will each pave 900m-long stretches of road with asphalt containing recycled plastic developed by RMIT University.

According to RMIT - the Royal Melbourne Institute of Technology - the paving will take place in “the coming months” and the 10 project sites will use an estimated 21,000kg of recycled plastic. RMIT noted that Australians generate 2.6 million tonnes of plastic waste each year.

“If Australia’s 537 local governments each used a small amount of recycled plastic in the many roads they resurface each year, then nationally we’ll have created a large end-market for recycled plastic,” said Filippo Giustozzi, associate professor in RMIT’s School of Engineering and leader of the project.

The RMIT-led project is supported by the Australian Research Council, Austroads and 10 Victoria state councils - City of Melbourne, Banyule, Bayside, Moonee Valley, Hobsons Bay, Baw Baw, Latrobe, Casey, Mornington Peninsula and Wyndham. The recycled plastic will come from consumer and industrial waste, including notoriously stubborn soft plastics, and be incorporated into asphalt as a performance enhancer.

Giustozzi said the team will also produce best-practice guidelines on the use of recycled plastics in asphalt roads. “These guidelines will enable local governments, which control 80% of the nation’s roads, to begin widescale adoption of this innovative recycling solution.”

Melbourne, the capital city of the Australian state of Victoria, has a regional population of just over five million. The port city has a temperate oceanic climate with warm summers and cool winters. Average low temperatures during the winter months of June, July and August are between 6C and 7C. The average high temperatures in summer months are just below 30C but can spike into the 40C plus range. The road network in Victoria state is managed by Vicroads, as part of Victoria’s state Department of Transport.

Extensive laboratory studies conducted by RMIT for Austroads – which combines Australia’s and New Zealand’s transport agencies – show the mixes developed by RMIT are mechanically, chemically and environmentally sound.

"The performance of roads can actually be improved with the additions of recycled material, such as plastic and rubber, to be more durable against traffic and resistant against ageing,” said Giustozzi.

RMIT said that its team’s latest study, funded by Austroads and published in the learned journal Science of the Total Environment*, found the recycled plastic asphalt mixtures had 150% less cracking and 85% less deformation under pressure testing than conventional asphalt.

“These studies tell us that adding specific types of plastic in the right way can generate greater rutting and fatigue resistance,” he said. “In some instances, the performance of the mix was similar to some of the more expensive polymers used in roads and substantially higher than conventional asphalt mixes.”

Geoff Allan, chief executive of Austroads, said the project is being driven by an increasing interest in exploring the viability of repurposing recycled waste plastic. “This project builds on the work completed last year that confirmed recycled plastics can be successfully incorporated in road infrastructure without detrimental effects on the environment, the health and safety of the workers or the future recyclability of plastic-modified asphalt.

“A major contribution of this project will be to develop evidence-based guidance that will provide certainty to road managers about the use of recycled plastics in road surfacing applications, laying the foundation for this solution to be embraced nationally.”

Along with Austroads, the collaboration includes Australia’s leading pavement authorities and specialists, including public works and building bodies, recyclers and contractors.

It will be coordinated under the ARC Industrial Transformation Research Hub for Transformation of Reclaimed Waste Resources to Engineered Materials and Solutions for a Circular Economy (TREMS).

*Engineering properties, microplastics and emissions assessment of recycled plastic modified asphalt mixtures' is published in Science of the Total Environment (DOI: 10.1016/j.scitotenv.2023.164869).

Information for this article came from RMIT University.