Some recycling alternatives use whole tires, thus requiring no extensive processing; other alternatives require that tires be split or punched to make products; and still other alternatives involve tires that are finely ground enabling the manufacture of crumb rubber products. Some applications for each alternative are listed below:
Whole tire applications
Artificial reefs and breakwaters Playground equipment Erosion control Highway crash barriers
Split or punched tire applications
Floor mats, belts, gaskets, shoe soles, dock bumpers, seals, muffler hangers, shims, washers, and insulators
Shredded tire applications
Lightweight road construction material Playground gravel substitutes Sludge composting
Rubber and plastic products; for example, molded floor mats, mud guards, carpet padding, and plastic adhesives Rubber railroad crossings Additives for asphalt pavements
All of the tire recycling alternatives listed above are being used to varying degrees. However, the total usage of tires for recycling currently is estimated to be less than 7% of the annual generation. The markets for most of the products may be increased, but, even if increased to their fullest potential, appear to be small compared to the number of tires generated each year. Ground rubber applications hold the greatest promise. The tire recycling alternative with the greatest potential to significantly reduce the scrap tire problem of the United States is in asphalt highway construction.
There are two types of processes for using crumb rubber in pavements. One application, referred to as rubber modified asphalt concrete (RUMAC), involves replacing some of the aggregate in the asphalt mixture with ground tires. The second, called asphalt-rubber, blends/reactivates a certain percentage of the asphalt cement with ground rubber. Both systems are being evaluated by state agencies as well as the federal government.
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