Evaluation of the polishing resistance characteristics of fine and coarse aggregate for asphalt pavement using Wehner/Schulze test

Traffic safety is influenced strongly by the skid resistance of pavements. Moreover, the long-term skid resistance of pavements depends mainly on the polishing resistance of the specific aggregate present on the surface. The polishing resistance is a measure which describes the roughness of aggregate after a polishing load has been induced by traffic loads. Specifications for the polishing resistance of aggregate are given only for coarse aggregate. However, given the various mixture types it is questionable if the fraction of fine aggregate (up to 55 M.-%) ought to be neglected, particularly since the polishing resistance of fine aggregate is higher than that of coarse aggregate. This paper aims to quantify the polishing resistance of various aggregate size fractions with particular focus on the properties of fine aggregate, and to demonstrate the suitability of the Wehner/Schulze test (W/S) in this regard. The results show that the initial skid resistance and the polishing resistance of fine aggregate are generally greater than that of coarse aggregate. It is notable that the initial skid resistance decrease is far more pronounced for fine aggregate. The polishing resistance does not exhibit a uniform development across all aggregate sizes. It is to be expected that fine aggregate may play a significant role for the skid resistance of asphalt pavements; however only coarse aggregate is considered in the design process. Further research is needed to precisely determine the effect of fine aggregate to allow for more economically feasible pavement designs.