Researchers reveal sun-smart bitumen blend

Rubber from used tyres acts like sunscreen for roads and halves the rate of sun damage when mixed with bitumen, new research has found. RMIT University engineers collaborated with Tyre Stewardship Australia (TSA) to reveal a bitumen blend that is both UV-resistant and withstands traffic loads, with the potential to save governments millions on road maintenance annually. The new study led by Associate Professor Filippo Giustozzi at RMIT University points to a sustainable solution to UV protection for roads, with results published in the Journal of Cleaner Production. “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,” Professor Giustozzi said. “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.” RMIT is one of the few universities in Australia to have a UV machine for asphalt studies, which can simulate weather-related ageing and is usually used for testing outdoor furniture paints. Giustozzi’s team used this machine to simulate the long-term effect of solar degradation in the lab on bitumen with different concentrations of crumb rubber: from a low concentration of 7.5 per cent to a medium of 15 per cent and a high of 22.5 per cent. After a month and a half of continuous exposure in the UV machine – equivalent to about a year of Melbourne’s UV radiation – they measured the changes in bitumen’s chemical and mechanical properties. Professor Giustozzi said bitumen mixed with the high concentration of crumb rubber from recycled tyres showed 50% less UV damage compared to regular bitumen. Associate Professor Filippo Giustozzi, RMIT University. While using more rubber was better in terms of UV resistance, Professor 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 per cent and 22 per cent of crumb rubber generates an ideal balance in terms of improving rut and fatigue resistance to traffic loads, while resisting UV ageing.” Professor Giustozzi said crumb rubber was already widely in use, including in some roads, but that the councils and state authorities using it were not aware of this ‘sunscreen’ effect revealed in the research.

Researchers reveal sun-smart bitumen blend

Industry Queensland

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