ERJ staff report (TP)
North Dakota – An environmental engineering professor is working on techniques to use ground-up old car tires to improve the surface of ageing roads while reducing both traffic noise and landfill, reported Olivia Solon for Wired.
Magdy Abdelrahman from North Dakota State University has been funded by the National Science Foundation to experiment with ground up old tires – which form "crumb rubber" – and other materials in order to improve the rubberised road materials that can be used to improve aging asphalt.
In the US alone, more than 300m scrap tires are generated each year. These usually end up in landfill or get illegally dumped. Finding new uses for these discarded tires is an area of growing interest, and road surfacing offers a large market for ground rubber – with a current need of around 100m kilograms of rubber per year, according to the US Environmental Protection Agency. Adding ground rubber allows for longer lasting, quieter (by as much as 25 percent) road surfaces.
"It's very durable," says Abdelrahman, "We mix it with different materials and in different percentages, and in different conditions, to find the best ways to add rubber to asphalt.
"The technology of adding tire rubber to asphalt pavement is not new. It was developed in the late 1960s and is proven to work, but we want to make it work much, much better."
The technique of "rubberising" road surfaces is much more widely used in the US – where 20,000 miles (32,187 km) of road are treated in this way – than it is in the UK. Trials have taken place in Scotland, but it hasn't caught on -- this partly due to a lack of regulatory encouragement and a conservatism in the road surfacing industry.
Having said that, the EU banned the disposal of tires in landfill sites in 2006, which leaves 480,000 tonnes of recyclable rubber annually. Reducing the noise of roads is particularly desirable for health reasons as noise pollution can cause hearing damage, high blood pressure and sleep disturbance. One in five Europeans are regularly exposed to sound levels at night that could significantly damage their health, according to the World Health Organisation.
In his research Abdelrahman is studying the interactions between the crumb rubber and other chemicals. He's also trying to work out whether heavy rain will cause chemical leakages from some of the recycled materials and whether that might have an impact on soil or groundwater.
"Traditional, that is, normal, asphalt-rubber materials will not cause harm to the soil or the ground water. But some additives may," he explains.
The biggest challenge of the research has been the variability of the properties of the source material, Abdelrahman said.
"Asphalt is a by-product. Tire rubber is a solid-waste material. Both materials were not manufactured specifically to be blended and used for road applications."
The work is supported to the tune of $400,000 (€289,245) over five years, but the grant is tied in with an educational component: Abdelrahman has developed a course on recycled materials applications and is keen to spread the word to the wider community, holding classes in schools to encourage recycling.
Marlene Cimons from the National Science Foundation explains: "It is really important for them to understand that if we keep using new materials, that our grandchildren won't have anything left.
“We're trying to get them to think about what will be available to the next generation in the way of resources if we cannot, or do not, use recycled materials. The goal is to educate high school, middle school and elementary school children, and show them that this is what needs to be done."
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Full story from Wired