Crumb rubber in asphalt mix ‘can double road surface life’

Rubber from used tyres acts like sunscreen for roads, halving the rate of sun damage when mixed with bitumen, new 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 from scrap tyres into the top layer of a road,” RMIT University’s Filippo Giustozzi said last week.

“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 six weeks of continuous exposure – the equivalent to about a year of UV radiation – a bitumen mix with 22.5 percent crumb rubber was found to have 50 percent less damage compared to bitumen without it.

Associate Professor Giustozzi said it was also important to balance the solar performance with a road’s 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 percent and 22 percent of crumb rubber generates an ideal balance in improving rut and fatigue resistance to traffic loads, while resisting UV ageing.”

Australia produced around 450,000 tonnes of end-of-life tyres in 2021, according to Tyre Stewardship Australia. About 70 percent were recycled or reprocessed.

The study to find a sustainable solution to UV protection for roads was published in the Journal of Cleaner Production.