Comparative Evaluation of Mechanical Parameters of Bitumen Modified with SBR and LDPE Polymers Produced in Iran and Imported SBS Polymer

An increase in traffic volume accompanied by an increase in axle load will induce higher stresses in pavement structures as a result early failure of the asphalt surface layer of pavement structures is observed. In the past two decades, modification of bitumen with polymeric materials has become a common practice to improve bitumen resistance against rutting and fatigue cracking. In this study, SBS, SBR, and LDPE are used with sasobit as a catalyst substance to evaluate fatigue characteristics of bitumen modified with these polymeric materials. Common tests recommended by SHRP researchers for evaluation and classification of neat bitumen as well as the linear amplitude sweep (LAS) test suggested for modified binders are conducted in this study. Dynamic shear rheometer (DSR) test results indicated that modification of neat bitumen with SBS, SBR, and LDPE polymers improved rutting index and increases high performance temperature of binders by three levels. Also, Sasobit reduced the rotational viscosity of polymer-modified binders and increased the high performance temperature of SBS-modified binders by one level. In addition, results of the BBR test showed that these additives did not have a positive effect upon the low-performance temperature of the modified binders. A comparison of fatigue performance of polymer modified binders based on the LAS test results also showed that SBR polymer had the most effect on increasing the fatigue life of the base binder. Besides, Sasobit increased the fatigue life of polymer-modified binders at high strain levels.