A Comprehensive Review on Asphalt Modification using Polycarbonate and Polyurethane: From Binder Rheology to Mixture Elastic Response

Polymer-modified asphalt (PMA) has become essential for enhancing pavement performance under increasing traffic loads and environmental stresses. While conventional modifiers like styrene-butadiene-styrene (SBS) have proven effective, their high cost and petroleum dependence necessitate exploration of alternative polymers. This review examines two distinct polymer modifiers: polycarbonate (PC) as a rigid plastomer potentially sourced from electronic waste, and polyurethane (PU) as an elastomeric modifier with reactive capabilities. A comprehensive analysis of 30 recent studies (2018-2025) reveals that PU modification significantly improves binder rheological properties, with increases in rutting parameter (G*/sinδ) of 50-200% at high temperatures and enhanced elastic recovery through multiple stress creep recovery (MSCR) testing. As demonstrated by an increase in dynamic modulus (E*) (30% to 80%), and resilient modulus (Mr) values, polyurethane (PU)-modified mixtures have high elastic response. The chemical studies prove that PU is produced as reactive networks through isocyanate-polyol condensation, and polycarbonate (PC) modification is based on physical blending. However, there is still a research gap in the critical: the literature is rich in PU data, but lacks experimental studies on PC-modified asphalt, although PC theoretically can be a rigid modifier of recycled components. The review summarizes existing PU knowledge, discusses the theoretical applicability of PC, and emphasizes critical researchers in comparative PC-PU studies combining micro-scale binder rheology with macro-scale mixture behavior.