ABSTRACT
The recent report by Travers Morgan into High Specification Aggregate has indicated that the predominate source of such aggregates is the Gritstone Trade Group. Greywacke aggregate quarried from the Longford Down Massif forms part of this group. Although there is variation within this group, they predominately consist of medium to fine sand sized particles held together by a matrix of mostly clay and chlorite minerals. The resulting sandpaper type surface texture results in these aggregates having a high level of skid resistance as measured in the laboratory using the Polished Stone Value test method. The results of this method form the basis for all surfacing aggregate specifications in the British Isles. However little is known about the relationship between mineralogy, surface texture and their in-service performance. Indeed doubts are currently being viewed as to the effective use of PSV in relation to skid resistance on the finished surface. This paper considers the relationship between mineralogy, grain size and PSV.
