In 1988, under a legislative mandate, the Florida Department of Transportation (FDOT) began a concentrated effort to evaluate the potential uses for reclaimed tire rubber in asphalt pavement construction. FDOT indicated that the most advantageous use of rubber would be as a binder modifier to improve the performance of friction coursemixtures. Three demonstration projects were constructed. The field construction operations with the rubber-modified mixtures were essentially the same as those with conventional friction course mixtures.Currently all of the test sections are performing well. The optimumrubber content for dense-graded friction course mixtures has been identified as 5 percent (by weight of asphalt cement) using a maximumnominal 80-mesh ground tire rubber. It is believed that the rubber will provide improved elasticity to the binder and therefore greaterresilience for these mixtures in recovery from high strains at intersections. The optimum rubber content for open-graded friction course mixtures was determined to be 12 percent (by weight of asphalt cement) using a maximum nominal 40-mesh ground tire rubber. In open-graded mixtures, the rubber has allowed a significant increase in the total binder content, which increased in the film thickness on the aggregate particles resulting in improved durability. On the basis of these demonstration projects, specifications have been developed forusing ground tire rubber in friction course mixtures as a standard practice.
Abstract