Role of aggregate petrography in micro-texture retention of greywacke surfacing aggregate

Aggregates provide more than 90% by weight of bituminous wearing courses that make up the road surface. This paper looked at the role of aggregate petrography towards the micro-texture retention of surfacing aggregate, through resistance to polishing under simulated trafficking conditions using the polished stone value test. For greywacke aggregate it was found that mineral composition, along with the shape of hard mineral grains within a softer clay matrix, had an effect on how aggregate surface polishes under trafficking. This impacts road surface performance, particularly skid resistance, which is a crucial safety aspect of a road surface course.