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Asphalt rubber (AR) is a sustainable paving material with merits including waste tire consumption, low traffic noise, and enhanced mechanical performance. However, the poor workability and storage stability limited its further application. This study attempted to alleviate these two concerns of AR simultaneously by incorporating heavy bio oil (HBO). To achieve this goal, bio-AR binders with three different mixing sequences were prepared. A series of rheological and chemical tests were conducted. Test results prove that the bio-AR binders exhibited superior rutting and fatigue resistance compared to AR binder. The viscosity values of bio-ARs were closed to AR modified with commercial warm mix additive, which indicates enhancement in workability. Due to the relatively high density of HBO, the density difference between the asphalt liquid phase and crumb rubber in the bio-AR system narrowed, which brought improved storage stability. Among bio-ARs prepared with different mixing sequences, the direct mixing one (ARB) had the most satisfied overall performance. The early incorporation of HBO had limited negative influence on binder performance, but allowed for more energy saving during the bio-AR binder production. Future study will be conducted on performance of bio-AR mixtures and quantitative estimation of its energy saving during the blending and compacting process. [ABSTRACT FROM AUTHOR]

This study investigated the interaction among different components of asphalt binders collectively modified with crumb rubber and warm mix additives through thermal gravimetric analysis (TGA) and differential scanning calorimeter (DSC) testing. The modified binders were divided into two parts for analysis purpose, namely the extracted crumb rubber modifier (CRM) by removing all asphalt components and the separated binder system by removing insoluble CRM particles. The main findings of this study include that: (1) the interaction between CRM and base asphalt was a component exchange process, i.e., natural rubber and styrene-butadiene rubber were released from CRM and blended with asphalt molecules; (2) wax-based warm mix additives penetrated into CRM during the mixing process; (3) the incorporation of warm mix additives especially the wax-based additives, promoted the component exchange between rubber and asphalt. [ABSTRACT FROM AUTHOR]

This study aims to investigate the rheological and chemical characteristics of asphalt rubber (AR) binders modified with four non-foaming warm mix asphalt (WMA) additives: Evotherm-DAT, Sasobit, conventional paraffin wax, and combined Evotherm-DAT and Sasobit. The main findings of this study include that: (1) all selected WMA additives are effective in enhancing AR’s workability; (2) using combined Evotherm-DAT and Sasobit is not a viable option to reduce the construction temperature of AR mixture; (3) paraffin wax is a potential WMA additive for AR; and (4) WMA additives may affect the dissolution status of crumb rubber in base asphalt. [ABSTRACT FROM AUTHOR]