More than 2 billion waste tires are stockpiled across the country. In addition, the united states disposes of 279 million waste tires each year, representing over 4 million tons of scrap waste. Although a limited number of waste tires are used for resource and energy recovery, the majority go to landfills or are disposed of in an environmentally unacceptable manner. In an effort to clean up old stockpiles of used tires and to promote the recycling of today's used tires, many road agencies are evaluating the use of discarded tires to modify asphalt cement mixtures. Ground tire rubber from waste tires has been used as an additive in various types of asphalt pavements inrecent years. The use of rubber is of interest to the paving industry because of the additional elasticity imparted to the binder and enhanced safety related to improved roadway skid resistance. However, it is the additional benefit of resource recovery, recycling used tires into rubber granulate for use in rubber-modified asphalt concrete, that has prompted a growing interest in its use. There are two primary reasons why rubber-modified asphalt mixes have not achieved widespread use. First, the capital costs for these surfacing alternatives is higher than conventional asphalt mixtures by 40 to 80%. Second, there is a lack of dissemination of information regarding properties and performance of these surfacing alternatives. Three different asphalt paving systems are described and the economics of each system is compared to conventional asphalt concrete. Also, a potential solution to the mentioned obstacles is described. This paper appearsin transportation research record no. 1310, Construction innovations 1991.
Abstract