Rubber from used tyres acts like sunscreen for roads and halves the rate of sun damage when mixed with bitumen, Australian research has found.
The UV-resistant, anti-ageing blend can also help roads withstand heavy traffic loads, potentially saving taxpayers millions of dollars spent on annual road maintenance.
“We found that the ageing trend is actually slowed down when you add crumb rubber, which is recycled from scrap tyres, into the top layer of a road,” engineer Filippo Giustozzi said.
“This acts so effectively as a sunscreen for roads that it actually makes the surface last twice as long as regular bitumen.”
A team from RMIT University used a UV machine to simulate the long-term effect of solar degradation on bitumen with different concentrations of rubber.
After a month and a half of continuous exposure – the equivalent to about a year of UV radiation – a bitumen mix with 22.5 per cent crumb rubber was found to have 50 per cent less damage compared to bitumen without it.
Associate professor Giustozzi said it was also important to balance the solar performance with a roads’ mechanical performance.
“You don’t want something that is UV resistant but not truck resistant,” the road materials expert said.
“We found adding between 18 per cent and 22 per cent of crumb rubber generates an ideal balance in terms of improving rut and fatigue resistance to traffic loads, while resisting UV ageing.”
Used tyres cannot be exported from Australia, making new methods for recycling and reprocessing them locally increasingly important.
Australia produced around 450,000 tonnes of end-of-life tyres in 2021, according to Tyre Stewardship Australia.
About 70 per cent were recycled or reprocessed.
Australian states and territories spent almost $2.9 billion on road maintenance in 2019/20, the National Transport Commission said.
The study to find a sustainable solution to UV protection for roads was published in the Journal of Cleaner Production on Wednesday.