Polishing behaviour of asphalt surface course containing recycled materials

Skid resistance is a key road safety factor indicating the provided friction of a pavement’s surface, which deteriorates over its service life mainly due to traffic polishing. Hence, the polishing behaviour of a pavement’s surface course is important for the provided road safety. For this reason, there have been many studies related to the assessment of polishing behaviour of asphalt mixtures. Besides, during the last decades the introduction of recycled materials in pavements has increased in order to face environmental challenges. However, investigations regarding the surface course are mainly centred around aspects of structural performance of the recycled materials. Contrariwise, it appears that the investigation for the provided skid resistance of asphalt mixtures containing recycled materials is limited. On these grounds, the present study investigates skid resistance performance through the polishing behaviour of asphalt mixtures containing recycled materials under the effect of traffic, simulated by the Wehner/Schulze machine. The investigated mixtures include conventional Hot-Mix Asphalt (HMA), as well HMA containing varying contents of Reclaimed Asphalt Pavement (RAP) material or recycled rubber in the form of Crumb Rubber (CR) originating from waste tyres. Analysis results demonstrate that the friction level of the tested asphalt mixtures containing RAP or CR is slightly lower than the conventional ones, but their overall performance seems to present an almost similar trend under the polishing effect. Generally, the study suggests a methodological approach towards the assessment of the skid resistance potentials for asphalt mixtures of a surface course that contain the investigated recycled materials, in an effort to act as a precursor for the enrichment of the related knowledge gap.