Potential Use of Ground Tire Rubber in Stone Matrix Asphalt (SMA) -- A Laboratory Evaluation

Stone Matrix Asphalt (SMA) is a gap-graded stone-to-stone mix whereby stiffer asphalt cement is required to bind the stones within the matrix together. Although various asphalt additives are traditionally available, the use of crumb rubber in SMA is still relatively new. Many developed and developing countries around the world are facing the serious problem of reject or discarded tires and some gains have been reported on practical use of these tires. This research project was a collaborative work between University of Putra Malaysia and South Dakota State University, USA. Commercial truck tires which have approximately 70% natural rubber were ground and supplied by Sime Tire Technology of Malaysia. The ground tire rubber was pre-blended with 80-100 penetration asphalt for use in SMA mixtures. This paper looks into the laboratory performance of rubberized SMA in terms of stability, resilient modulus, dynamic creep and tensile strength ratio. It was observed that the performance of SMA with ground tire rubber is far superior as compared to SMA Mix with unmodified asphalt. Sulfur and Styrene Butadiene Rubber (SBR) were used in rubberized SMA mixes as additives to test the sensitivity of SMA mixtures.