Mineralogical and microstructural controls on the surface texture of high polished stone value aggregates

The number of stone aggregate sources that provide a high polished stone value and therefore a high skid resistance on road surfaces is relatively small. The factors that influence polished stone value have traditionally been associated with mineralogical and mechanical properties of specific rock-types. This study examines a group of variable lithologies from a single source, that exhibit similar laboratory measured polished stone value readings. It can be shown that multiple properties, including microstructural fabrics, can influence the potential PSV of an aggregate. 3D areal surface measurements of the aggregate surface, obtained using z-stacked digital images, can be combined with traditional mineralogy and microstructural observations, to track the development of surface microtexture from the source through to in-service trafficked sites. These combined methodologies can provide a detailed picture of how specific rock-types or regional geological settings can influence the polished stone value of aggregates and how different and varied factors can control the maintenance of a textured surface throughout its use.