Influence of different polishing conditions on the skid resistance development of asphalt surface

The development of the skid resistance of asphalt road surfaces was simulated in a laboratory. Asphalt plates were taken from a test track. They were polished using the Aachen Polishing Machine (APM) with real tires under various conditions and their skid resistances were determined using the Wehner/Schulze machine (W/S). The process of binder removal and polishing of the aggregate can be accurately described using a five-parameter skid resistance model. It was observed that the asphalt plates showed different skid resistance behaviors and reached different final states under varying polishing conditions. It can be concluded that wetness conditions, polishing agents and the affinity between aggregate and bitumen were decisive for the skid resistance development. They could influence the removal speed of the bitumen film, the peak value as well as the final value of the skid resistance. The polishing using the W/S test could lead to an overestimation of the predicted skid resistance level when the grain size and composition of dust on the road surface deviates excessively from that of the standard polishing agent applied in the W/S test. For a realistic skid resistance prediction, it is therefore recommended that the asphalt specimen should be polished using a polishing agent with similar gradation to that of the dust on the road surface.