Evaluation of the effect of coarse and fine rubber particles on laboratory rutting performance of asphalt concrete mixtures

The nation faces ecological problems due to the accumulation of waste automobile and truck tires. In this study, the effect coarse ground tire rubber (GTR) and crumb rubber on rutting performance of Superpave asphalt concrete mixtures as measured in the laboratory were evaluated. A percentage of the locally available coarse rubber, uniformly graded is used as a substitution for aggregate particles, at nine levels of rubber percentages, 0%, to 4.0 % at 0.5%, increments, while maintaining the well-graded Superpave gradation. In addition to coarse rubber, fine crumb rubber particles (minus No 80 and No. 20 mesh) in proportions of 5% and 15%, were evaluated using the compaction characteristics of the Superpave Gyratory Compactor to determine the optimum percentage of coarse and fine rubber particles that can be used in the asphalt concrete mixture. The coarse rubber particles exhibit increased rutting resistance as percentage of rubber increased up to 3.5 %. On the other hand, crumb rubber dissolved in the binder and stiffened to increase its rutting resistance. Even though only up to 2.5% coarse rubber particles could be were used as compared to 15 % of crumb rubber, the processing cost of coarse of rubber is much less than crumb rubber to make it cost effective.