Evaluation of pretreatment effects on high-content crumb rubber asphalt binder modified with recycled low-density polyethylene (LDPE)

• Asphalt binders modified with pretreated high-content crumb rubber, LDPE, and sulfur. • The physical properties, storage stability, chemical properties, and rheological properties were studied. • Pretreated high-content crumb rubber reduced the softening point difference by 93.83%. • The correlation coefficient for the storage stability and chemical properties was R 2 = 0.96. • LDPE improved high-temperature performance. The utilization of waste materials such as high-content crumb rubber (CR), waste cooking oil (WCO), and low-density polyethylene (LDPE) in asphalt binder significantly reduces environmental waste while providing sustainable environmental and economic advantages for asphalt pavement applications. This paper aims to evaluate the effect of WCO-pretreated CR on the properties of LDPE-modified high-content crumb rubber asphalt binder (HCRMAB) to establish a linear correlation between chemical composition and storage stability. The viscosity tests demonstrated significant reductions in binder viscosity when incorporating 20% pretreated high-content crumb rubber (PHCR) compared to 20% untreated high-content crumb rubber (UHCR). The viscosity decreased by 56.77% at 135 °C, with substantial reductions of 41.73%, 30.84%, 44.12%, and 53.79% observed at 150 °C, 165 °C, 180 °C, and 195 °C, respectively. Storage stability tests indicated that 20% PHCR-modified asphalt binder showed a 93.83% lower softening point variation than 20% UHCR-modified asphalt binder. These results indicate that waste oil pretreatment significantly improves the workability and storage stability of pretreated high-content crumb rubber asphalt binder (PHCRMAB). Moreover, the addition of LDPE to PHCR-modified asphalt binder, particularly the addition of 20% PHCR+4% LDPE+0.60% sulfur, showed enhanced storage stability. Fourier transform infrared spectroscopy (FTIR) confirmed chemical interactions during modification, with a strong correlation ( R 2 = 0.96) between storage stability and chemical properties. Results from dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests revealed LDPE improved high-temperature properties but reduced low-temperature cracking resistance. These findings promote the practical application of pretreated high-content crumb rubber-modified asphalt (PHCRMA) in sustainable pavement construction.