Performance characterization of warm mix asphalt for porous wearing courses and base layers produced with highly polymer modified bitumen

Increasing road traffic demands have led to the need for longer lasting, higher performing pavements. To improve pavement durability, extend its service life and reduce maintenance costs, highly polymer modified bitumen (HiPMB) containing ad hoc styrene polymers has been introduced to the market. The objective of this study is to evaluate the performance of warm mix asphalt (WMA) produced with HiPMB to be used for porous wearing courses and base layers of motorway pavements. Specifically, three HiPMBs (two available on the European market and one under development, each one with styrene polymer content ≥ 7.5%) are examined and compared with a reference polymer modified bitumen (PMB) containing 3.8% SBS polymers. The porous mixtures were subjected to workability analysis, indirect tensile strength (ITS), semi-circular bending (SCB) and Cantabro tests (all carried out after both dry and wet conditioning). As for the base mixtures, testing included indirect tensile stiffness modulus (ITSM) and indirect tensile fatigue tests (ITFT), in addition to workability and ITS analysis. The results indicate that, in some cases, asphalt mixtures produced with HiPMB perform better than asphalt mixtures produced with PMB. The issues in terms of adhesion with aggregates observed for the HiPMBs could explain some penalized performance characteristics of the related mixtures.