Rubberized Asphalt Concrete (RAC)
What happens when you mix regular asphalt concrete with ground up, used tires -- called “crumb rubber”? You get Rubberized Asphalt Concrete, also known as RAC.
RAC has generated a lot of interest because not only does it divert zillions of old tires from taking up space in landfills, it also reduces road noise. The rubberized element of this interesting paving material cuts down the decibels of road noise so effectively that it’s also considered a possible material for use in constructing sound walls along busy highways.
Rubber Pavements Association (RPA) is a non-profit industry association with members in 15 states in the U.S. and 10 countries worldwide. This gives an indication of the spreading interest and use of RAC, which this organization refers to as CRM (Crumb Rubber Modified) Asphalt. Some salient tidbits from the organization’s FAQ page include:
- The first successful time/temperature formula for incorporating scrap tire rubber into an asphalt paving material was developed by Charles McDonald in Phoenix, AZ, in the 1960s.
- About 10 million tires are recycled each year in paving applications.
- In this age of conservation of natural resources and recycling, the reduced thickness of rubberized asphalt can save on the amount of aggregate required to resurface a road. That means less aggregate material will be mined from diminishing reserves and transported to the job site.
With a focus on education, the RPA has a variety of ways it makes information available to government agencies of transportation, scrap tire recycling agencies, and other environmental protection interest groups, to name a few.
One of these government agencies is part of the U.S. Environmental Protection Agency (EPA): The GreenScapes Program, which “encourages more holistic decisions regarding waste generation and disposal and the associated impacts on land, water, air, and energy use.” In one of the Roads and Highways articles featured in GreenScapes’ Success Stories Section, an example of effective use of RAC is given:
“Maine's Department of Transportation saved $8.7 million by constructing a rural bridge from trash! 170,000 previously used shredded tires—20 percent of the waste tires generated in Maine in a year—were used in this project to support the roadbed, along with old bridge railings, roadside guard rails, and geotextiles.”
Another example says, “Plagued by 10 million waste tires a year, Los Angeles county has saved landfill space by using recycled rubber in paths, playgrounds, and under structures throughout its district.” This indicates that RAC is being used effectively for more applications than paving roads, with more applications being developed as this new technology grows.