Optimised bitumen-rubber blend shows enhanced resistance to UV and loading

Melbourne, Australia - Engineers at Melbourne’s RMIT Universityhave developed a road-surfacing material incorporating rubber recyclate, which offers enhanced resistance to both UV and traffic loads.

Working in collaboration with Tyre Stewardship Australia (TSA), the RMIT team sought to address the effects of intense sunlight on roads, which makes them prone to cracking and potentially unsafe to drive on. 

Incorporating recycled rubber offers sun protection and a “sustainable solution to Australia’s used-tire crisis,” said RMIT - noting that Australia has banned the export of used tires since December 2020.

According to the TSA,  while Australia produced around 450,000 tonnes of end-of-life tires in 2021, only around 70% of those were recycled or reprocessed.

While research efforts have focused on improving the durability of roads in terms of traffic load, the university said thermal ageing and other weather-related damage has received little attention.

“We found that the ageing trend is actually slowed down when you add crumb rubber, which is recycled from scrap tires, into the top layer of a road,”  said study leader Filippo Giustozzi, associate professor at RMIT.

“This acts so effectively as a sunscreen for roads that it actually makes the surface last twice as long as regular bitumen, said Giustozzi, who is a leading road engineer in Australia.

The team used a specialised lab machine to simulate the long-term effect of solar degradation with different concentrations of crumb rubber, from 7.5% to 22.5%.

The results showed that bitumen mixed with the higher concentrations of crumb rubber from recycled tires showed 50% less UV damage compared to regular bitumen.

And, reported Giustozzi: “We found adding between 18% and 22% of crumb rubber generates an ideal balance in terms of improving rut and fatigue resistance to traffic loads, while resisting UV ageing.”