EVALUATION OF RUBBER-MODIFIED ASPHALTIC CONCRETE

The effective disposal of waste tires has become an increasing problem that will grow if something is not done to alleviate it. With this concern in mind, legislation has been passed to encourage the public and private sector to find ways to reuse tires. Other State DOTs have been incorporating waste tire rubber into many different asphaltic materials, primarily as a crack sealant. Some have experimented with adding ground tire rubber to asphaltic mixes in hope that it will solve the dilemma of growing waste tires and produce improved road surfaces. This report evaluated rubber-modified asphaltic concrete mix using the wet process in comparison to the Pennsylvania Department of Transportation's standard ID-2 bituminous wearing mix. The wet process pre-blends the ground rubber into the liquid asphalt and then adds the rubber-modified asphalt to the aggregate. The control mix and the rubber-modified asphalt mix were compared over a performance period of 5 years, and the rubber-modified asphalt mix results were unfavorable. The rubber-modified asphaltic mix showed enhanced signs of wear and cracking, while the standard ID-2 mix showed normal wear and minor cracking. Therefore at this time, utilizing waste tires in rubber-modified asphalt concrete using the wet process is not recommended for use by the Department as an alternate roadway mix.