Storage Stability and Performance Assessment of Styrene-Butadiene-Styrene: Waste Polyethylene-Modified Binder Using Waste Cooking Oil

This study investigated the compatibility of waste plastic, a serious environmental and recycling concern, with styrene-butadiene-styrene (SBS) in asphalt binders. An extensive storage stability analysis of binders modified with varying dosages of low-density polyethylene (LDPE) from postcommercial usage with SBS as a compatibilizer and the understanding of behaviors of each component was conducted in this study. Although SBS-LDPE blends were stable with separation index in terms of G*/sin, percent recovery from multiple stress creep recovery (MSCR) detected nonhomogeneity of polymer dispersion in the asphalt blend. To address this nonhomogeneity, waste cooking oil was used to pretreat LDPE to enhance the dispersion and reaction with the binder. Ultimately, 4.5% SBS + 1.5% oil-treated LDPE (TLDPE) was observed to yield a stable SBS-TLDPE blend with a top-bottom separation index ratio of 1.0 in terms of G*/sin and percent recovery difference of 3.5% and 1.4% at 0.1 and 3.2 kPa, respectively. The study identified that the presence of LDPE negatively influences the recovery and cracking performance of asphalt binders at low temperatures. From critical temperature differential (Tc), Glover-Rowe (G-R) parameter and Black space diagrams at different aging levels, it was concluded that unlike SBS, SBS + LDPE combination had resistance against extended long-term aging.