Physical and Rheological Properties of High-Performance Modified Asphalt Binder Utilizing Comingled Waste Plastic and Rubber Alloy

Incorporating waste plastics into asphalt not only has the potential to enhance pavement durability and strength but also presents a sustainable approach to plastic recycling. However, due to the immiscibility of plastics with asphalt, storage stability of asphalt becomes a challenge. This study investigates a novel approach by combining various types of waste plastics [polyethylene (PE) and polypropylene (PP)] with rubber to produce modified materials. Unlike previous studies that mainly focused on single plastic types, this study emphasizes the fusion of comingled common waste plastic with rubber to create a modified asphalt binder, aiming to improve its storage stability and reduce the cost of waste screening. Additionally, the study assesses the potential of recycled plastic-rubber (rPR) modified asphalt as a viable alternative to styrene-butadiene-styrene (SBS) modified asphalt. The rPR-modified binders were produced using a reactive extrusion process that involved different plastic and rubber ratios. Their physical and rheological properties were assessed through a comprehensive set of tests, including softening point, separation, rotational viscosity (RV), dynamic shear rheology (DSR), multiple stress creep recovery (MSCR), and bending beam rheometer (BBR). The results indicate that optimizing the plastic-rubber ratio significantly enhances the modified asphalt’s stability and performance. Furthermore, rPR-modified binders demonstrated comparable rheological properties to SBS-modified binders, meeting the required performance standards for road applications.