Laboratory Evaluation of the Effect of Natural Bitumen Powder (Gilsonite) On Performance of Stone Matrix Asphalt Mixtures

Coarse aggregate constitute main part of Stone Matrix Asphalt mixtures (SMA). In consideration appropriate workability of SMA to rutting it is required excellent lock and bind between coarse aggregate particles, bitumen and fibers are required, to fill the gaps and voids. Although there are numerous recourses of gilsonite in Iran, but there are limited studies about this modifier. So, there is a need to investigate the effects of using this material as a modifier. In this study different percentage of Gilsonite (0%, 5%, 10% and 15% compared to the total asphalt binder used in mixture) was used and bitumen characteristics including softening point, penetration test and viscosity were examined. The performance tests including, marshal stability, flow, resilient modulus and dynamic creep test are carried out on unmodified and modified SMA mixtures with UTM system. According to the results of laboratory tests and assessment of the results it can be said that by increasing the Gilsonite to the SMA mixtures, Marshal stability of specimens increases, in addition resilient modulus and dynamic creep parameters have significant increase which leads to enhancement in rutting performance.