Finding an acceptable way to dispose of used tires has been a challenge since the advent of the automobile.
Landfilling them is not practical, even if the landfill will accept them. There have been far too many illegal dump sites for tires over the last several years, and burning them produces a large amount of black smoke that pollutes the atmosphere. The best way to handle any type of waste is to find a beneficial use for it. Used tires are no exception.
In California, individuals are forward thinking with recycling. The Department of Resources Recycling and Recovery has approved a $5 million grant for road improvements in 43 communities throughout the state. In all these projects, rubberized pavement will be utilized. To manufacture rubberized pavement, the rubber from used tires is combined with traditional materials to make a road material that is safer and longer lasting. It lasts around 50 percent longer than regular asphalt. Rubberized pavement is also more resistant to cracking. It is more cost effective, in part because the roads can be surfaced with a thinner layer of pavement. In fact, rubberized pavement can be about half the thickness of traditional pavement. There are performance advantages to rubberized pavement as well. It has proven itself to be more skid resistant and does not create as much spray during rainy conditions. It will also cut down the traffic noise by as much as 5 decibels, which is a significant amount. This pavement resists fading more than traditional asphalt. This helps to keep the lines on the highways visible for longer.
It takes about 2,000 used tires to make enough material to pave a single lane for a mile. Because the pavement is thinner, it requires a smaller amount of the other materials with which the rubber is mixed. This saves on raw material costs and uses fewer natural resources. In California for example, an estimated 38 million tires have been diverted from landfills, recovering enough of them to pave 19,000 miles of road.
The technical term for rubberized pavement is rubberized asphalt concrete (RAC). Prior to the RAC production process, the steel cords are removed from the used tires. The rubber is then ground into granules called crumb rubber. Next, the rubber goes through additional processing to reduce the size of the granules even further. The granules are then sized by passing them through a screen. Rubberized asphalt is the largest use for crumb rubber in the United States, although a significant portion of it goes into padding under artificial turf in stadiums. When used for pavement, the rubber is kept suspended through agitation and must be used within eight hours after production to prevent losing its elasticity.
While the state of California is leading the way in using old tires to repair and pave roads, the Arizona Department of Transportation was among the first to experiment with rubberized asphalt concrete. The original purpose was to see if its use would cut down on highway noise enough to justify the elimination of sound walls. It was soon discovered that the new pavement material exceeded expectations. Not only was the noise reduction more than originally hoped for, but it proved to have advantages in the areas of safety, longevity and cost effectiveness as well. The elasticity of the new pavement made it more resistant to cracking. The product is being tested in some of the northern states to see how well it performs in colder climates.
The use of rubberized asphalt concrete for pavement is currently growing at a rate of around 10 percent per year. As more and more decision makers become informed of its advantages, the growth is sure to continue, especially with the focus on going green. As technology develops, the advantages of rubberized pavement will grow even further. When RAC was newly developed, it was not feasible to use it in smaller applications like parking lots. It could only be used in long continuous stretches of roads. Now, people are realizing that keeping used tires out of the landfill not only makes good economic sense, but, simply put, it is the right thing to do.