Effect of granular polymers on rutting performance of SMA with respect to modification process

The aim of this research is to investigate the effect of two types of modification processes for granular polymers, Polymer Modified Bitumen and direct addition of polymer into mix, on rutting performance of Stone Matrix Asphalt (SMA). In this research, granular polymers including Rheofalt and Ethylene-Copolymer-Bitumen (ECB), namely Lucobit, were used and their impact on rutting resistance improvement were compared with SBS modified and unmodified mixtures. Results of performing dynamic creep test revealed that, with respect to both modification types, Rheofalt modified mixtures resulted in significantly greater rutting resistance than ECB modified ones. Moreover, it was found that although ECB modified bitumen is effective to rutting enhancement, there is no improvement as a result of direct addition of it into mixtures. On the other hand, results showed that Rhefalt is influential in direct addition into mixtures but not as efficient as introduction of Rheofalt modified bitumen into mixes. Finally, investigating resilient modulus vs. cycle curves, it was revealed that SBS with elastomeric property predominance resulted in resilient modulus reduction as the content increases while Rheofalt and ECB showed reverse trend with their content increase.