Disposal of scrap tires in stockpiles is one of the most significant environmental problems in the U.S. In order to reduce the negative effects of the scrap tires, tire management programs have been developed by different states. One method of beneficially re-using the scrap tires is the construction of crumb rubber (CR) modified asphalt pavements. Today, many states, local agencies and municipalities are using crumb rubber modified asphalt mixtures in pavement construction. There are currently three major methods of introducing CR in asphalt mixtures, namely; wet process (CRWet), dry process (CRDry), and the terminal blend process (CRTB). Most past research focused on each of these technologies individually and compared with traditional or polymer modified asphalt mixtures. There is a need to comparatively evaluate the performances of these technologies and unmodified (traditional) asphalt mixtures. In order to address this issue, a comprehensive study of three different CR types (CRWet, CRDry and CRTB) was conducted in this research. The scope of this study included both asphalt binder tests (Brookfield viscosity, resilience, needle penetration and softening point tests) and asphalt mixture tests (Dynamic modulus (|E*|) test, flow number (FN) test, four point bending beam (FPBB) test and tensile strength ratio (TSR)). Samples were compared in terms of their rutting, fatigue cracking and moisture susceptibility performances. The scope of this research also included sustainability-based analysis of CR modified HMA pavements. Four sustainability rating tools (LEED, Greenroads, GreenLITES and INVEST) were studied and compared to each other in terms of their applicability to CR modified HMA's.
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