√Australian researchers develop roads with recycled plastics
The use of recycled plastics to replace materials normally used in the manufacturing of asphalt could remove tonnes of waste from landfill, while also improving the durability of our roads.
Scientists at Melbourne’s RMIT University have been working on a project which could result in recycled plastics being incorporated into Australian roads.
With support from the Australian Research Council, Austroads, and a number of local governments, scientists have been working on a way to reuse plastic normally destined for the tip.
Speaking to Drive, project lead Associate Professor Filippo Giustozzi confirmed the use of recycled plastic simply replaced polymers that have traditionally been used in road construction for decades.
“We measured surface friction in the lab, and the presence of plastics had no discernible effect,” Assoc Prof Giustozzi responded when asked about the effect on braking distances.
“We intend to incorporate a range of 0.5 to 1 per cent recycled plastics into the entire road mix,” which he says will be melted during the manufacturing of the asphalt – replacing the aforementioned polymers – rather than simply being chunks of plastic.
“What does significantly affect friction, however, is the micro- and macrotexture of the aggregate [such as gravel and crushed stone] but, as I said, the plastic will undergo melting at the production temperature.”
While 0.5 to 1 per cent may not sound like much, it has the potential to remove tonnes of plastic that would normally end up being thrown out.
It’s expected 21 tonnes of recycled plastic will be saved from landfill in the coming months, used instead in a total of nine kilometres of road across 10 trial sites across Melbourne.
“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,” Assoc Prof Giustozzi said.
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As well as reducing the amount of plastic going to landfill, the researchers claim the recycled materials also improve the performance of the roads, being “more durable against traffic and resistant against ageing”.
A study published in the journal Science of The Total Environment – an international, peer-reviewed publication – found the recycled plastic asphalt mixtures had 150 per cent less cracking and 85 per cent 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.”
However, the engineer dismissed questions about whether the use of recycled plastics would increase the amount of so-called ‘microplastic’ emissions entering the environment.
“Our intention is not to introduce a greater quantity of microplastics than what is already prevalent in current practices, such as the use of other polymer materials in roads,” he told Drive.
“For example, road markings are already composed of plastic polymers,” he added.
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While developing the practice of incorporating recycled plastics into asphalt, the RMIT-led project discovered there was no threshold or standard for evaluating microplastics that come from roads.
“As a result, we had to develop a testing standard for this purpose, which is the first of its kind worldwide. This standard is set to become a national standard in Australia,” Assoc Prof Giustozzi said.
“During our experimental campaign, we discovered that there is no discernible difference between roads that incorporate polymers commonly used in road construction and those made with recycled plastic, when testing for the presence of microplastics.”
It’s expected the trial will help form “evidence-based guidance” to road-making companies, with the hope the increased use of recycled plastics in roads will gain traction nationally.
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