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 (T_t), continuous temperature (T_c), and delta continuous temperature (ΔT_c)]. Using recycled materials in asphalt mixtures increased EABs’ low temperatures, T_t and T_c , and decreased EABs’ ΔT_c values when compared to EABs from mixtures without recycled materials. Using RAS in asphalt mixtures degraded the low-temperature properties of EABs, T_t and T_c increased and ΔT_c decreased, when compared to EABs from mixtures containing RAP. Increasing the asphalt binder replacement (ABR) percentages by recycled materials increased T_c and decreased ΔT_c . The flow activation energy (E_a) was related to the T_c and ΔT_c values, and very strong relationships were observed between E_a and T_c and E_a and ΔT_c . The researchers modelled two low-temperature prediction models to predict T_c and ΔT_c depending on the grade of the virgin asphalt binder, ABR types and percentages, and asphalt mixtures ages.