Unlike much outdoor infrastructure, roads are not designed with any sun protection, making them prone to cracking and potentially unsafe to drive on.
Now, RMIT University engineers collaborated with Tyre Stewardship Australia (TSA) to discover the perfect blend that is both UV resistant and withstands traffic loads, with the potential to save governments millions on road maintenance annually. Their new research has found that crumb rubber, which is recycled from scrap tires, acts like sunscreen for roads and halves the rate of sun damage when mixed with bitumen.
Crumb rubber has already shown promise in making concrete stronger and more heat resistant. The new study found that the material acts so effectively as a sunscreen for roads that it actually makes the surface last twice as long as regular bitumen.
To test their idea, researchers added crumb rubber into the top layer of asphalt with different concentrations: from a low concentration of 7.5% to a medium of 15% and a high of 22.5%. The team used a UV machine to simulate the long-term effect of solar degradation in the lab on bitumen. The machine exposed them to high levels of UV light for a month and a half – equivalent to about a year of Melbourne’s UV radiation – and measured the changes in bitumen’s chemical and mechanical properties.
The team found that bitumen mixed with the high concentration of crumb rubber from recycled tires showed 50% less UV damage compared to regular bitumen. While using more rubber was betters in terms of UV resistance, researchers said it was also important to balance this with mechanical performance.
“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 aging,” said Filippo Giustozzi, Associate Professor at RMIT University.
Incorporating recycled rubber not only offers sun protection but provides a promising sustainable solution to the waste rubber tire crisis. After consumption, rubber tires become waste, leading to enlarged landfill areas for used tires and implying additional harm to the environment, so useful ways to recycle are welcome.