Comparative Performance Evaluation of Asphalt Binder Modified with High-Content Pretreated Crumb Rubber and Various Additives

The addition of high-content crumb rubber (HCCR) in asphalt can effectively address waste tire pollution and provide sustainable environmental and economic advantages. However, the practical application of conventional rubberized binders is significantly limited by high viscosity and poor storage stability. To address these issues, researchers have pretreated crumb rubber (CR) with oil, but high-temperature performance remains insufficient. Therefore, this study aimed to optimize the viscosity, storage stability, and rheological properties of high-content crumb rubber-modified asphalt (HCCRMA) by varying the pretreatment levels of CR and incorporating various additives, including styrene-butadiene-styrene (SBS), deoiled asphalt (DA), or recycled low-density polyethylene (RLDPE). In addition, CR was pretreated with waste cooking oil (WCO) at various ratios, pre-swelling temperatures, and times. The results show that DA exhibits excellent storage stability and lower viscosity compared with other modifiers in HCCRMA, and the 4% RLDPE with pretreated HCCR has the greatest high-temperature rutting resistance. The inclusion of RLDPE increases the stiffness and elasticity of the modified asphalt, which results in greater high-temperature performance. Additionally, the fluorescence microscopy (FM) test confirms that SBS exhibits better dispersion than other modifiers and forms a more homogeneous phase separation in the HCCRMA. All in all, this research achieved an optimal balance of storage stability and rheological properties in asphalt modified with pretreated HCCR and 6% SBS, which provides a valuable reference for performance improvement of HCCR-modified binders.