Using old tyres to make permeable pavements that filter rainwater

3 minute read

Melbourne CBD road flooded

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Porous Lane, a new company using University of Melbourne technology to develop highly permeable pavements using old tyres is supplying water for  the city's parks and gardens, diverting landfill and ensuring less pollution in our waterways.

Key points

  • Porous Lane draws on University of Melbourne research to manufacture permeable pavements from recycled tyres
  • These environmentally-friendly pavements filter rainwater to reduce stormwater runoff, support healthy tree growth and protect our urban environment against flooding
  • Porous Lane pavements are cheaper, more durable, easier to maintain and offer better water infiltration than their competitors, with the added benefit of using at least 50 per cent recycled content

The outcome

The permeable pavement was trialled in 2019, at a carpark in the City of Mitcham in South Australia.

Research revealed the site required less maintenance, offered superior performance for traffic loading, was more cost efficient compared to other existing technologies and had higher levels of water infiltration compared to competitor products. It also showed the pavement uses around three old tyres per square metre equating to more than 1000 tyres removed from landfills just in one single project.

The trial won the Excellence in Sustainable and Environmentally Responsible Infrastructure Management award at South Australia’s Local Government Leadership Excellence Awards in 2020.

"The reason we’ve had so much momentum is because we involved everyone and listened to them," says Associate Professor Mahdi Disfani, a geotechnical engineer from the University's Faculty of Engineering and Information Technology. "That included Sustainability Victoria, Tyre Stewardship Australia, the City of Mitcham (among other councils), urban planners, tree experts and Porous Lane. For example, our product was developed in the lab but it has to be laid outside, so we learned a lot about the procedure that councils’ contractors use on site."

Since then, Porous Lane has started operating commercially. Its clients include other local councils in South Australia and Victoria, such as Boroondara, Darebin, Moreland, Yarra and Banyule. So far, its pavements have primarily been used for tree protection zones, footpaths and bicycle paths.

Porous Lane’s permeable pavements are a particularly popular option for inner city suburbs facing population growth and development, where there are increased flash flooding risks due to large areas of impermeable surfaces and the need to maintain a healthy green canopy.

With a healthy number of projects in line, the next steps for Porous Lane include attracting investment to boost production and establishing automated manufacturing, which will enable better quality control. It will also enable the team to scale-up production, reduce costs and remove the limitations of weather on project installations.

This means tens of thousands of tyres averted from Victorian landfills, more water for trees and less pollution in our precious waterways.

The need

Australia’s cities are growing bigger and denser. This means more ground is being covered with impermeable surfaces, like concrete and asphalt, that do not allow water to get to the ground. These surfaces can damage the environment in a number of ways:

  • Stormwater runoff picks up pollutants like microplastics and heavy metals and carries them into waterways
  • Aquifers are not sufficiently replenished, so trees and other plants do not receive the water they need to be healthy and this impacts the green canopy we need in our urban areas
  • The risk of flash-flooding increases, which can damage property and cause soil erosion.

In Europe, permeable pavements have been used for decades to help reduce these environmental impacts. These surfaces are now growing in popularity in Australia too. However, existing products use crushed quarried rock, which is not a sustainable option. Mining this rock damages the environment, and it requires carbon-intensive processing before use.

Australia also has a significant tyre waste problem, with around 56 million waste tyres generated every year. The majority of these go to landfill or, worse still, are illegally stockpiled on private properties.

Existing applications for recycling tyres (such as surfaces in children’s playgrounds) use a small proportion of old tyres and are limited in volume. But researchers had been unable to engineer a recycled tyre solution that can bear heavier loads like cars and bikes.

Developing the solution

Associate Professor Mahdi Disfani from the Faculty of Engineering and Information Technology at the University of Melbourne is an expert in geo-materials made from recycled aggregates.

He experimented with different solutions to find the right combination of recycled tyre, rigid rock aggregate and binder that was sufficiently permeable as well as mechanically strong enough to tolerate traffic load.

He found a solution comprising at least 50 per cent recycled tyre that is capable of sustaining traffic loads. It provides some flexibility to reduce cracks caused by natural ground movement or tree roots, but not so much that it becomes unstable under traffic loads.

"With a lot of recycled products, it can be a struggle just to achieve the expected performance. So when we tested the mixture in the lab under pavement conditions and saw its performance was significantly higher than expected, it was really exciting," Associate Professor Disfani says.

He also worked closely with the Translating Research at Melbourne team (a division of the University dedicated to helping academics commercialise their research) to ensure the final product met end users’ needs. These needs included cost-effectiveness, ease of maintenance and ability to install under different weather conditions.

The project was supported from research through to commercialisation by Tyre Stewardship Australia and the University of Melbourne Technology Transfer team.

Partner

Tyre Stewardship Australia

City of Mitcham

City of Melbourne

Funding

Tyre Stewardship Australia

City of Mitcham

Faculty of  Engineering and Information Technology, University of Melbourne

Patents

Intellectual Property is protected by the University of Melbourne and fully licensed to Porous Lane.

Publications

Mechanical Performance of Tire-Derived Aggregate Permeable Pavements Under Live Traffic Loads, 4th International Conference ofTransportation Geotechnics – Chicago, US, 2021

Experiments and Dimensional Analysis of Waste Tire-Based Permeable Pavements, Geosynthetics International 2021, https://doi.org/10.1680/jgein.21.00029

Infiltration Rates of Recycled Tyre-Based Permeable Asphalt Pavements and Future Maintenance, Conference: Stormwater 2021 – Melbourne, Victoria, Australia

Field performance monitoring of waste tire-based permeable pavements, Transportation Geotechnics, 2020, https://doi.org/10.1016/j.trgeo.2020.100384

People

Professor Mahdi Disfani, Faculty of Engineering and IT

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