Business Feature, Earthmoving News, Environment & Research, Road Building

Recycled plastics used to improve Victorian roads

RMIT University has partnered with 10 Victorian councils to demonstrate how the issue of waste plastic can be tackled in an innovative way – by recycling it as a performance enhancer in new Victorian roads.

With growing pressure on councils to find better ways of managing waste plastics, one project currently underway across Victoria is testing the viability of reusing selected plastics within road building.

As part of an RMIT University project that evaluated the engineering properties and environmental impacts of plastic in roads, recycled plastics are currently being used in an asphalt mix to pave local council roads in Melbourne and across regional Victoria.

Led by RMIT professor Filippo Giustozzi, the project has found that recycled plastics can be used to improve performance in asphalt roads – benefiting road users by resisting rutting and cracking of the surface.

“On hot sunny days, the roads tend to soften, especially under slow-moving heavy loads,” Giustozzi says.

“With selected recycled plastics, we can enhance the performance of the road and bring it up to a level where there is no rutting and cracking can be delayed by several years.”

Many trucks and cars are constantly driving over the same spots repeatedly, which erodes and damages the surface over time. The RMIT professor says recycled plastics have the potential to reduce the number of road-replacement works and therefore lead to significant cost savings in road maintenance.

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When asked how this project came to fruition, Giustozzi says it came down to laboratory research that he wanted the public to actually see and benefit from, rather than just be read in a report.

“Having an issue with recycled waste, the Commonwealth government sponsored RMIT back in 2020 to fund research into recycled plastics being used in roads,” he says.

“They went through Austroads, which is the collective of Australian and New Zealand transport agencies, to fund our research.”

Since then, Giustozzi’s team has conducted two years of research, collecting recycled plastic from Australia and New Zealand and analysing it for reuse in asphalt and bitumen. The project also investigated microplastics release, fuming at high temperatures, and future recyclability of plastic-modified asphalt.

The RMIT project team has also partnered with 10 Victorian councils that have already incorporated the recycled plastics into their local government roads.

Results have been successful so far, with each council selecting its own asphalt contractor. Image: Filippo Giustozzi

Council roads

Providing one road each as part of the demonstration project, the 10 Victorian councils involved in the trial are the City of Melbourne, Banyule, Bayside, Moonee Valley, Hobsons Bay, Baw Baw, Latrobe, Casey, Mornington Peninsula and Wyndham.

Results have been positive, with the trial showing that asphalt plants can easily introduce small pellets or flakes of recycled plastics into their day-to-day operations.

Each council selected its own asphalt contractor and found that the recyclable-plastic asphalt mix was easy to produce.

“This shows us that the industry is ready to embrace this kind of technology, and that was the primary assessment for us,” Giustozzi says.

Stage two of this project is currently underway, which involves bringing materials from the road paving sites back to the RMIT laboratory and sampling them.

As part of the project, each council agreed that they would use two asphalt mixes in the road paving – one being a standard everyday mix and the other the recycled plastic mix.

Approximately 130 to 140kg of each mix was collected from every council and brought back to the RMIT laboratory, according to Giustozzi.

“For stage two of this project, we have started doing the analysis of those mixes and our aim is to find out which one performs better in a laboratory perspective,” he says.

Stage three of the project entails on-site monitoring, where Giustozzi says field-monitoring services will be provided by an external company.

“Using special vehicles, we will be able to see which of these two asphalt mixes performs better and have the least amount of damage incurred after over time,” he says.

The recycled plastics used in the asphalt mixes were sourced from local Victorian companies. Image: Filippo Giustozzi

Recycled plastics

Sourced locally from Victorian companies, the RMIT professor says the recycled plastics used included a combination of low-density polyethylene and linear low-density polyethylene – found in many different objects.

“One of the companies that provided the material recycle water tanks,” Giustozzi says.

“They take these water tanks and shred them, clean them, wash them and then recycle them back into new pellets.”

Another company provided a combination of polyethylene and polypropylene, which Giustozzi says can have different origins, including post-consumer plastics and agricultural types of plastics recycled back into another plastic product.

What he found most interesting was the materials used at the Hobsons Bay Council, where the RMIT team engaged with a company called CRDC Global.

“CRDC Global have developed a technology that will allow them to avoid the challenge of separating plastics,” Giustozzi says.

“They put them all together and they get a product, which is like a plastic aggregate, that can be used for construction purposes.”

With this in mind, the Hobsons Bay Council collected its own plastic from council offices and brought it into CRDC Global, which converted that waste into plastic aggregates – eventually used to construct the new roads.

“It’s important to note that we are not taking waste and shovelling it back into the road, as we don’t want roads to be the next landfills,” Giustozzi says.

“These types of plastics have been studied for two years and each and every single small detail has been evaluated, from microplastics to the presence of toxic substances. Everything that was not corresponding to our criteria was disregarded.”

For more information on the project, contact Professor Filippo Giustozzi at filippo.giustozzi@rmit.edu.au

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