Thermal cracking in cold regions’ asphalt mixtures prepared using high polymer modified binders and softening agents

This study was conducted to assess high polymer modified asphalt binders including a corn oil-based softening agent (SA) and their impact on the cracking performance of mixtures in cold regions. Styrene–Butadiene-Styrene (SBS) polymer modifier, corn-oil-based softening agent, and Performance Grade 52–34 binder were proportioned at various dosages to prepare modified binders. The mixtures were aged according to three loose mix aging procedures (short-term, long-term, and extended long-term). It was found that the SBS and corn-oil combination improved both the high and low continuous grade along with percent recovery, and reduced fatigue cracking potentiality based on a reduced negative ΔT_c at the binder level. In addition, at the mixture level, an increase in the Disc-shaped Compact Test (DCT) fracture energy was observed at low temperatures; also an increase in cracking temperature due to thermal stress from Thermal Stress Restrained Specimen Test (TSRST) was observed, indicating better cracking resistance. Regardless of aging, the flexural stress from the beam fatigue test also decreased, indicating higher resistance to fatigue cracking at intermediate temperatures. The study suggests that the balanced application of SBS and corn-oil can lead to the optimum improvement in low temperature cracking performance of the evaluated asphalt mixtures.