Wider Use of Recycled Tires in Asphalt- Plastjoo

Polymers Pave Way for Wider Use of Recycled Tires in Asphalt
 

Polymers Pave Way for Wider Use of Recycled Tires in Asphalt 

 
Each year, about 27 million tires end up in landfills, dumps and stockpiles, where they pose health and environmental hazards. Because rubber is so resilient, scrap tires persist in the environment for a long time, creating fire hazards and breeding grounds for rodents and mosquitoes. This durability could make tires advantageous for producing rubber asphalt –– a mixture of ground tire rubber and bitumen (asphalt) used to pave and repair roads. Rubberized asphalt concrete (commonly known as RAC) is a road paving material made by blending ground-up recycled tires with asphalt

 

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RAC is a proven product--one that has many benefits, including being cost effective, durable, safe, and an environmentally friendly alternative to traditional road paving materials


•    Cost-effective. In most applications, RAC can be used at a reduced thickness compared to conventional asphalt overlays--in some cases at half the thickness of conventional material--which may results in significant material reduction and cost savings. In addition there may be life-cycle cost savings from the reduction in maintenance costs and longevity of RAC


•    Durable, Safe. RAC is long lasting. It resists cracking, which can reduce maintenance costs. Case studies have demonstrated repeatedly that RAC, when designed and constructed properly, lasts much longer--often 50 percent longer--than conventional materials. Additionally, RAC provides better skid resistance, which can provide better traction. Moreover, RAC retains its darker color longer so that road markings are more clearly visible


•    Environmentally Friendly


but blends of ground tires and asphalt can be unstable. Currently, about half of U.S. states use ground tire rubber as a component of asphalt mixes, citing better performance than regular asphalt, cost-effectiveness and environmental benefits. However, the material has two major challenges that limit wider use


high viscosity-
tendency to separate into rubber and bitumen layers during storage-

 

  
 Now, researchers have identified polymer additives that increase the storage stability of asphalt rubber

 

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The researchers studied the stability of rubber asphalt made by blending and extruding different amounts of the polymers cis-isoprene, trans-isoprene, polybutadiene or polyisobutylene with ground tire rubber. The team found that, when mixed with asphalt, blends of ground tire rubber with trans-isoprene or polybutadiene in a 3:1 ratio performed the best. These mixtures reduced the density of ground tire rubber so that it was similar to asphalt and did not settle during storage. The polymers also helped reduce the viscosity of the rubber asphalt so that the material was easier to work with. According to the researchers, the polymer additives are cost-effective, resulting in savings of about 7 to 10 percent compared with regular asphalt

 

Editor: Nasim Rashidi Nezhad
 

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