Recycled tyres use in bitumen helps lifespan of roads

Recycled tyres use in bitumen helps lifespan of roads

In new research conducted by RMIT University in Australia it was found that rubber from used tyres in the composition of asphalt, halves the rate of sun damage. Researchers say that this mix acts like sunscreen for roads and reduces the rate of sun damage when rubber from used tyres is mixed with bitumen.

Researchers at RMIT University have discovered a bitumen blend that is both UV-resistant and withstands traffic loads, with the potential to save governments millions on road maintenance annually. For instance in the US alone, most of the over 300 million scrap tyres end up in landfills since they are almost impossible to recycle using conventional methods.

Unlike much outdoor infrastructure – such as playground equipment and outdoor furniture – roads are not designed with any sun protection, making them prone to cracking and potentially unsafe to drive on.?

While most research so far has mainly focused on enhancing road durability in terms of traffic load, little attention has been given to the wear and tear, thermal ageing and the weather. The stripping of pavement markings on both parking lots and roads is often owed to the asphalt oxidation due to chemical reactions caused by UV rays.

The researchers employed a UV machine specially designed for asphalt studies that can simulate the long-term effect of solar degradation on roads. They fired this machine in the lab at bitumen mixed with three different types of rubber concentrations: a low concentration of 7.5%, a medium one of 15%, and a high concentration of 22.5%. The machine operated continuously for a month and a half, simulating about a year of UV radiation around Melbourne

When they measured the chemical and mechanical properties of the bitumen, they found that the bitumen with a high concentration of crumb rubber exhibited 50% less UV damage compared to conventional asphalt.

“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,” said Associate Professor Filippo Giustozzi at RMIT University, lead author of the new study.

The results, published in the?Journal of Cleaner Productionalso point to?50% less UV damage compared to regular bitumen.

While using more rubber was better in terms of UV resistance, Giustozzi said it was also important to balance this with mechanical performance. 

“You don’t want something that is UV resistant but not truck resistant,” he said.? 

“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.” 

Giustozzi also said an added advantage of crumb rubber was that it was already widely in use, including in some roads, but that state authorities using it were not aware of this ‘sunscreen’ effect revealed in the research.