"Use of recycled materials has been gaining popularity all over the world to provide a sustainable future for next generations. Crumb Rubber (CR) and Reclaimed Asphalt Pavements (RAP) have been the mostly recycled products in the asphalt industry. Federal and state governments have been searching for alternative methods of either disposing or recycling the large number of waste tires. The use of shredded tire rubber (i.e., crumb rubber - CR) in asphalt pavements is one of the sustainable recycling approaches. Increasing the amount of CR integrated into asphalt pavements reduces various risks involved with stockpiling, burning, damping into landfills and other undesirable disposal methods of scrap tires. Another benefit of using CR is being an alternative for polymer modification. Polymer modification of asphalt binders has gained quite a large popularity in many transportation agencies, primarily due to the superior crack and rut-resistant performance. However, added cost of polymer modification results in an appreciable increase in the initial cost of an asphalt pavement. Use of Recycled Tire Rubber (RTR) is a more economical and sustainable alternative to polymers. Yet, another benefit of CR is the binder softening effect. Addition of RAP in new Hot Mix Asphalt (HMA) construction is a useful practice since it reduces the amount of naturally derived aggregates and virgin binder in the mixture. Increased RAP usage also provides economical savings (e.g., reduced freight cost of the virgin materials) and environmental benefits (e.g., conserves energy that is used while extracting natural aggregates and asphalt cement). Due to the continuous increase in the asphalt binder costs (which is directly related to gasoline costs), utilizing high percentages of RAP (up to 40-50%) is essential for lowering the production costs of asphalt pavements. However, increasing the percentage of RAP in a new asphalt pavement may hinder the economic benefits due to the necessity of expensive softer binders used to compensate for the RAP stiffening effect. Alternatively, this problem may potentially be overcome by use of another recycled material; recycled tire rubber. RTR is known to soften the binder at low/intermediate temperatures, eliminating the need to use soft-expensive binder. Three major contributions of this dissertation can be listed as follows: Interaction between RTR and polymer modified binders have been investigated in terms of performance grading (stiffness), fatigue cracking and rutting.; Interaction between RTR and high volume RAP mixtures has been evaluated in order to eliminate costly soft binders.; Interaction between dry crumb rubber and crumb rubber terminal blend technologies have been studied in order to increase the crumb rubber content without needing expensive plant equipment for crumb rubber wet technology."--Pages ii-iii.
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