Evaluating the Low-temperature Properties of Asphalt Binders Extracted from Mixtures Containing Recycled Materials

Abstract

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 low-temperature 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.