Analysis of the chemical, rheological, performance and durability properties of highly polymer-modified bitumen produced at large scale

New styrene polymers with high vinyl content in polybutadiene have been recently introduced for bitumen modification. These polymers can potentially ensure higher resistance to oxidation, heat and UV radiation and better compatibility with bitumen compared to conventional SBS (styrene-butadiene-styrene) polymers. Therefore, the polymer content in bitumen can be increased (currently up to 9 %) to produce the so-called highly polymer-modified bitumen (HPMB). Among the limited studies available, most of them investigate laboratory-prepared HPMBs, which may not be representative of large-scale production. Conversely, the studies investigating HPMBs produced at an industrial scale often lack detailed binder composition data, limiting the interpretability and generalizability of the results. To address these limitations, the objective of this study is to characterize the chemical, rheological, performance and durability properties of an HPMB currently under development for use in Italian motorway pavements (“HPMB_A”) and compare this binder with a reference PMB and two commercially available HPMBs. PMB and HPMB_A were produced at large scale using the same base binder and following the same procedure. These four binders were subjected to an extensive laboratory characterization. The results indicate that the HPMBs behave like a “rubber” modified with bitumen rather than a modified bitumen, which leads to significantly improved performance and aging resistance. However, the adhesive properties of HPMBs can be lower than PMB because of the volumetric predominance of the polymer over the bitumen. Moreover, due to the complexity of these binders, common tests and performance criteria adopted for conventional bitumen may not be fully adequate for HPMBs.