An initial read of the headline might sound alarm bells in neighborhoods across the country. But think about it: If you’re a safety-conscious RVer, you know that the recommended lifespan of RV tires is but five years. That could produce a lot of old tires. Where are they gonna go? How about in your driveway? No, NOT ON your driveway, but IN your driveway.
Researchers at the University of South Australia got a “gee-whiz” idea. Why not replace some of the sand in concrete used on slabs with “crumb rubber.” This stuff is the remains of ground-up tires, chopped to a fine size, about equivalent to that of sand. Steel and other reinforcing materials are removed in the production process. By mixing the crumb rubber with cement, water, and other normal concrete ingredients, scientists working with concrete plant operators were able to prepare a concrete mix. They used this to form two reinforced concrete slabs at the entrance to the civil engineering laboratory.
University folk constructed the two old tire rubber slabs in 2018. At the same time, they also installed two conventional concrete slabs for comparison. After three years of use, the slabs were compared. Results?
“Superior to conventional—in some ways”
“We found that reinforced crumb rubber concrete (with up to 20 percent sand replacement by volume) is superior to conventional concrete in some ways, with higher impact resistance, toughness and ductility, a higher damping ratio, better thermal and acoustic insulation, and a lighter weight,” said study author Dr. Osama Youssf.
But what about the installation work? How does concrete made with old tires stack up from a labor and equipment perspective? “With respect to pumping, screeding, or finishing the concrete surface using a power trowel, contractors also reported no difference between using the crumb rubber concrete and conventional concrete, saying that the crumb rubber mix actually required less physical effort across all aspects,” concluded the report. Concrete truck drivers reported that cleaning the crumb rubber concrete out of the cement truck was easier than conventional concrete.
“The results clearly show that crumb rubber cement is a viable and promising alternative to conventional concrete in the residential concrete market,” said study author Professor Yan Zhuge. “We strongly recommend that the concrete industry considers crumb rubber concrete as a sustainable alternative to conventional concrete in reinforced residential constructions in Australia.”
But then there’s the cost
More tires recycled means fewer tires taking up space in landfills, or piling up forming mosquito breeding ponds. That’s a plus! There may be some amount of resistance in terms of cost. At present, a ton of sand sells for an average of $21. Crumb rubber is a bit more expensive, selling for more than $200 a ton. But keep in mind, crumb rubber weighs nearly five times less per cubic foot than sand. With that, the cost difference works out to be about twice the cost for rubber versus sand.