European highways today are nearly 75,000 kilometers and are constantly being expanded. Besides to the road construction, maintenance existing highways is an essential task to keep the traffic rolling and thus also economic growth on the old continent.
In addition, since 1975, the number of vehicles per 1000 inhabitants has more than doubled within the European Union. Long-distance road freight transport has also increased significantly. More and more trucks are on the road with increasingly large axle loads, posing new challenges for road surfaces.
Asphalt blends containing rubber have been used in the United States for many decades now, and long-term studies there have verified significant improvements in stability. “The European market for elastomer-modified road surface has been growing for a few years,” says Frank Lindner, the sales and new business development manager for VESTENAMER®. “Its positive properties are obvious, because it significantly reduces the formation of ruts and potholes, as well as the susceptibility of the road surface to cracking—and that extends product life.”
Another one of our senses supports the use of rubber-modified bitumen as well: crumb rubber is often used in open-pored silent asphalt, where it reduces traffic noise. Scientific studies have shown that increasing the proportion of rubber used in pavement can lower noise levels by one to two decibels—a huge success, as Lindner points out, because reducing noise by three decibels cuts the perceived traffic volume down by half.
The addition of VESTENAMER® also delivers additional advantages over other rubber modifiers: using the process enhancer, he says, reduces the mixing temperature required to produce a homogeneous blend. “One consequence of that is a significant reduction in energy consumption. Another is the release of fewer emissions,” Lindner explains.
Making worthwhile use of scrap tires
Using recycled tires makes environmental sense every time: “Recycling used tires protects valuable resources,” points out Dr. Sandra Reemers, who is responsible for the specialty polymers business. “The tires aren’t classified as garbage—they’re instead considered to be valuable materials that shouldn’t just go, say, to a landfill. And that makes the disposal question moot: instead of burning tires, we give them a new life on the road, albeit one as an elastomer in the road surface instead of a horsepower-driven one on the road.”
One recognized certification body conducted a study providing information on the environmental performance of the system: the study found that, for each metric ton of crumb rubber used, recycling eliminated roughly 1.7 metric tons of carbon dioxide emissions that would otherwise result from incineration. Use of this material, in other words, takes us a long way toward optimizing our carbon footprint, Reemers observes, noting that, when the road surface then needs to be replaced at some point, the asphalt can be recycled. “So you end up with a closed loop,” Reemers explains. In addition, the system developed by Evonik generates enormous potential for reducing CO2, as a life cycle assessment conducted by the Genan company has demonstrated. Growing numbers of European towns and cities are deciding to use elastomer-modified asphalt more and more often. Plus, polymer-modified asphalt blends were incorporated into road construction regulations in the spring of 2013.