Roads always seem to be in need of repair, but changing up the recipe could help them last longer. Researchers in Australia have now shown yet another advantage of adding rubber from old tires to asphalt – extra Sun protection that could help roads last up to twice as long before cracking.

Anyone who’s ever touched a road on a hot day knows that those things hold heat. And despite being out in the elements all day, every day, nothing is added to protect them against Sun damage, leading to the cracks and potholes every driver is familiar with.

In a new study, researchers at Australia’s RMIT University have found an environmentally friendly way to shore up roads against the onslaught of the Sun’s rays. The key is to add crumb rubber, a form of ground-up material made from waste rubber products like old tires. It’s already shown promise in making concrete stronger and more heat resistant, and the researchers wondered whether it could protect asphalt from UV light degradation.

To test out the idea, the team added crumb rubber into the top layer of asphalt, at three different concentrations – 7.5 percent, 15 percent and 22.5 percent. Then, these samples were placed in a machine that exposed them to high levels of UV light for a month and a half, an accelerated aging process that’s the equivalent of what local roads would endure over the course of a year. Finally, changes in the chemical and mechanical properties of the asphalt were measured.

The team found that the samples with the highest concentration of rubber showed half the UV damage of regular asphalt. However, putting too much in might start to detract from the road’s resistance to mechanical damage.

“We found adding between 18 percent and 22 percent of crumb rubber generates an ideal balance in terms of improving rut and fatigue resistance to traffic loads, while resisting UV aging,” said Filippo Giustozzi, lead author of the study. “This acts so effectively as a sunscreen for roads that it actually makes the surface last twice as long as regular bitumen. We knew that UV would be a factor in road degradation, but not by what degree or how to protect against it, as nobody has really been looking at this aspect.”

The other advantage of the technique is that it gives old tires a new lease on life. These waste products are a major environmental hazard that keeps building up, so useful ways to recycle them are welcome.

The research was published in the Journal of Cleaner Production.