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Abstract
Quality of bitumen plays a key role in the performance related properties of asphalt mixes. The rapid increase in the number of commercial vehicles combined with overloading of trucks and substantial variation in daily and seasonal temperature of the pavement have been responsible for premature failure of the flexible pavements in India. The bitumen obtained from Indian refineries meets the existing specifications, but the studies have shown that the premature failure of flexible pavements in India is mainly occurring due to inability of conventional asphalt mixes to sustain repeated application of wheel load. The quality of bitumen can be improved by adding additives to the bitumen. This paper presents laboratory investigations on the performance of the styrene butadiene styrene (SBS) and linear low-density polyethylene (LLDPE) modified mixes. The optimization of polymer is normally done on the basis of empirical tests in many countries including India, in this study, the optimum dose of modifier is determined on basis of SHRP scientific parameter G*/sin δ. The physical and mechanical properties of polymer modified binders and binder aggregate mixes are evaluated. There is an improvement in the strength characteristics and moisture susceptibility of the polymer modified mixes. The resistance to permanent deformation in wheel tracking and dynamic creep tests of polymer modified mixes was better than that of unmodified mix. The fatigue lives of the polymer modified mixes are, respectively, 4.6 and 2.2 times higher than those of the corresponding unmodified asphalt mix.