Prediction of UK surfacing skid resistance using Wehner Schulze and PSV

Skid resistance has been the most important property of a surface layer in the UK for many years. It has been provided by the use of aggregate with high polished stone value and mixes designed with high texture. However, in recent years this traditional approach has been subject to investigation and the simplistic relationship between texture depth and polished stone value questioned. The polished stone value test has been found to be a ranking method dependant on the stressing conditions imposed during the tests i.e. vary the stress during testing and different aggregates will react in different ways to achieve a new equilibrium level. The German Wehner Schulze test is now proposed within Europe as a replacement to the polished stone value test. This method subjects either laboratory prepared asphalt samples or cores extracted from the pavement surface to simulated trafficking and measures change in skidding resistance with time. The method has been accepted by German contractors to predict performance of the mix. This paper details an investigation of the Werner Shultz equipment to assess UK asphalt surfacing mixes