

Road surface microtexture is essential for pavement skid resistance. Microtexture depends on the changes of coarse aggregate surface used for wearing coarse during the actual traffic conditions. Due to the fact that microtexture existis on a microscopic scale, it is very difficult to assess. An indirect method of assessing microtexture is PSV (Polished Stone Value) of coarse aggregates. However, it is difficult to explain the changes on aggregate surface during polishing process on the basis of PSV. The aim of experiment is to assess changes in the coarse aggregate microtexture with the polishing process based on the analysis of digital images, which are made by optical microscopy. Coarse aggregates from dolomite, granodioryte, gabbro, dolorite, sandstone were chosen for the tests. The polishing process of aggregate was divided into two phases and carried out in the accelerated polishing machine. The standard deviation σh from the histogram of intensities digital image of the surface is a measure of microtexture. During the polishing the asperities of mixrotexture change specific for each type of rock. It was noted that aggregates which included minerals of similar hardness (granodioryte, dolomite, dolerite) were more prone to polishing than others. Regeneration of the microtexture, the recovery to its original asperity, occurred in the case of sandstone.