PSV tyre / test specimen contact

The PSV test has been used for many years. It is the harmonised European standard method for predicting an aggregates polishing resistance. This paper considers the test tyre / test specimen interface. This was done by painting the PSV test specimen surface and subjecting it to a period of accelerated polishing. Digital images of the test specimen were analysed using 2d and 3d techniques. Tyre / aggregate contact area was found to range from 17 % to 92 % of the test specimen area. Factors such as particle shape (convex, concave, flat) and particle orientation in the test specimen influence contact. The contact interface relates to the uppermost 1 to 2 mm of the test specimen surface. A weak relationship was found showing contact area to increase as wet skid resistance decreased. Whilst aggregate micro-texture remains an important factor the research suggests addi-tional scales of texture and contact influence water films at the interface. The findings of this paper impact attempts to measure road skid resistance using non-contact methods of measurement.