Tire recycling is the process of converting end-of-life or unwanted old tires into material that can be utilized in new products. End-of-life tires typically become candidates for recycling when they become no longer functional due to wear or damaged and can no longer be re-treaded or re-grooved.
According to the tire industry, tire recycling is a major success story. The stockpile of scrap tires has shrunk from over a billion in 1991 to just 60 million by 2017 and the asphalt industry is a big factor in shrinking the number of tires in landfills.
Ground rubber applications accounted for 25% of scrap tire usage in 2017. Ground rubber is used to manufacture a number of products but the largest use of ground rubber is for asphalt rubber, utilizing approximately 220 million pounds or 12 million tires annually. The largest users of asphalt rubber are the states of California and Arizona, followed by Florida, with usage anticipated to grow in other states as well.
Recycled tire rubber (RTR) from waste tires has been used in asphalt by the paving industry since the 1960’s. RTR has been used as an asphalt binder modifier and asphalt mixture additive in gap-graded and open-graded asphalt mixtures and surface treatments.
What is RTR?
Recycled tire rubber is basically recycled tire rubber which has been ground into very small particles to use as an asphalt modifier. Adding ground tire rubber to asphalt can contribute to improved rutting resistance, skid resistance, ride quality, pavement life and reduced pavement noise levels. Adding rubber to the asphalt liquid retards aging and oxidation of the resulting binder, which increases pavement life by lessening brittleness and cracking.
How is RTR Made?
The handling and shredding of tires is a carefully planned and monitored process to produce a clean and highly consistent rubber material. The crumb rubber is produced through a process of grinding rubber tires into very small particles.
During the process, the tire’s reinforcing wire and fiber is removed. The steel is removed by magnets and the fiber is removed by aspiration. Processing the tires using cryogenic fracturing involves cutting up the larger tire pieces into smaller, typically 50 mm particles, using sharp steel cutters. These smaller pieces are then frozen and fractured. The rubber particles are sieved and separated into different size fractions, as specified by the customer. The resulting rubber particles are consistently sized and very clean. Automated bagging systems help ensure proper bag weights and eliminate cross contamination.
Where to Learn More
The National Asphalt Pavement Association (NAPA), will be hosting the Where the Rubber Meets the Road Webinar Series this summer on recycled tire rubber and asphalt.
Here are the upcoming events:
- Wednesday, May 29. Where the Rubber Meets the Road: Recycled Tire Rubber and Modern Asphalt Pavements Episode 2: Tires – Just the Way You Like Them. 2 p.m. EDT.
- Wednesday, June 12. Where the Rubber Meets the Road: Recycled Tire Rubber and Modern Asphalt Pavements Episode 3: When the Rubber’s in the Road. 2 p.m. EDT.
- Date TBD: Proof in Performance
- Date TBD: Binder Testing