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The use of recycled materials -- such as reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) -- in asphalt mixtures reduces natural resources demands and decreases materials dumped in landfills. The aged binders included in the recycled materials alter binders' low-temperature properties included in asphalt mixtures. Therefore, asphalt binders were extracted from asphalt mixtures collected from the field as cores. Due to the limited amount of extracted asphalt binders (EABs), a dynamic shear rheometer was used to examine the low-temperature properties [e.g., true temperature (Tt), continuous temperature (Tc), and delta continuous temperature (ΔTc)]. Using recycled materials in asphalt mixtures increased EABs' low temperatures, Tt and Tc, and decreased EABs' ΔTc values when compared to EABs from mixtures without recycled materials. Using RAS in asphalt mixtures degraded the lowtemperature properties of EABs, Tt and Tc increased and ΔTc decreased, when compared to EABs from mixtures containing RAP. Increasing the asphalt binder replacement (ABR) percentages by recycled materials increased Tc and decreased ΔTc . The flow activation energy (Ea) was related to the Tc and ΔTc values, and very strong relationships were observed between Ea and Tc and Ea and ΔTc. The researchers modelled two low-temperature prediction models to predict Tc and ΔTc depending on the grade of the virgin asphalt binder, ABR types and percentages, and asphalt mixtures ages. [ABSTRACT FROM AUTHOR] more...

Asphalt binder modification by crumb rubber modifier (CRM) could enhance its rheological properties at high and intermediate temperatures by increasing its stiffness and elasticity. To obtain a modified binder blend with more enhanced intermediate- and low-temperature rheological properties, used motor oil (UMO) was introduced to the crumb rubber-modified asphalt (CRMA) binder. The enhanced high- and intermediate-temperature rheological properties of the modified binders were investigated using a temperature sweep test. UMO, used as a rejuvenator, can regulate the CRM role in the modified binder blend by creating a balance between the binder's enhanced stiffness and fluidity. This was achieved by increasing |G*|/sin δ at high temperatures and decreasing |G*|.sin δ at intermediate temperatures. The mutual components between the CRM and the asphalt binder were explored by thermogravimetric analysis and Fourier transform infrared (FTIR) spectroscopy. UMO was found to have similar FTIR bands of the asphalt binder that helped the CRM particles to absorb more low-molecular-weight fractions at the beginning of the interaction time, which caused them to swell more and then dissolve, releasing their polymeric components in the asphalt binder's liquid phase. Adding UMO with two and half percentage by the weight of the neat asphalt binder to the CRMA binder, interacted at 190°C–50 Hz–60 min, could increase the CRM dissolution and cause a greater release of CRM polymeric components into the asphalt binder matrix. This was assured by the presence of FTIR peaks at 911 and 966 cm−1 that are related to the polybutadiene, synthetic rubber in CRM. [ABSTRACT FROM AUTHOR] more...