Thermal, Chemical and Rheological Properties of Asphalt Binders Extracted from Field Cores

Abstract

Asphalt binders were extracted and recovered from field cores that were collected from different routes. These cores were for asphalt mixes containing virgin asphalt binders (VABs) with different performance grades (PGs) and different asphalt binder (ABR) replacement percentages by reclaimed asphalt pavement (RAP) and/or recycled asphalt shingles (RAS). These mixes had ages between 4 and 14 years during the sampling process, thus the extracted asphalt binders (EABs) were treated as long-term aged binders. Using RAP/RAS in asphalt mixes alters the performance of EABs at intermediate temperatures. Thus, the resistance of EABs to fatigue cracking was explored through rheological testing that included Superpave fatigue cracking parameter (|G*|.sinδ) and the number of load repetitions to failure (Nf). Thermal properties of EABs were evaluated using thermogravimetric analysis; different parameters were evaluated from the thermal analysis [e.g., percentage of residue (%R) and onset temperature (Tonset)]. The chemical properties of EABs were examined by a Fourier transform infrared (FTIR) spectroscopy through evaluating carbonyl (ICO), sulfoxide (ISO), aromatic (ICC), and aliphatic (ICH) indices. The relationships between the resistance of EABs to fatigue cracking, thermal and chemical properties were scrutinized. Ages of mixes, ABR percentage by RAP/RAS, and PGs of VABs controlled the resistance of EABs to fatigue cracking. Direct relationships were observed between |G*|.sinδ and %R, ISO and Nf, ICH and Nf, ICO and %R, and ICC and %R. Inverse relationships were found between Nf and Tonset, Nf and %R, Nf and ICO, Nf and ICC, %R and ISO, and %R and ICH.