Experimental investigation on the effects of waste plastics in bituminous binders

This thesis has been developed within the framework of the PRIN SWITCH project. The initiative addresses one of the most pressing challenges of modern society: the increasing production of non-biodegradable plastics and their inadequate disposal, which often leads to significant environmental concerns. The road infrastructure sector, especially road engineering, emerges as a promising area for exploring new applications, all while keeping sustainability at the forefront. This research focuses on the characterization and modification of standard bitumen by incorporating recycled polymers to enhance binder performance. The mixtures were assessed using both traditional empirical classification and performance-based methods to evaluate how they behave under various conditions. The experimental campaign is designed to assess the influence of different recycled plastics, selected for their availability and interesting compatibility with bituminous binders. Different types of recycled plastics were employed to modify the binder, each characterized by specific compositions. To evaluate their impact, the investigation combined empirical tests—carried out on all binders in their original state—with performance-based analyses. Rheological properties were studied through the Dynamic Shear Rheometer (DSR) under different ageing conditions, while the Bending Beam Rheometer (BBR) was applied to PAV-aged binders to assess low-temperature performance. This integrated approach allowed for a comprehensive understanding of the materials’ behavior, from their initial condition to advanced ageing scenarios. The results showed that plastics with higher polyolefin content ensured better compatibility with bitumen, facilitating blending. On the other hand, plastics composed of different polymers (e.g. polypropylene) provide more significant benefits in terms of performance, particularly with improvements in the complex modules. Overall, the study confirms the feasibility of using post-consumer plastics as sustainable modifiers to enhance the properties of bituminous binders.