Inadequate abrasion resistance of road surfacing aggregates means an early loss of the texture depth required to maintain high speed skidding resistance. The Cooper-Wessex Aggregate Abrasion machine determines the Aggregate Abrasion Value by testing the measure of the resistance of aggregate to surface wear by abrasion.
Two specimens are pressed against the surface of a steel disc rotating in a horizontal plane, with a force of 0.365 Newton’s per sq. centimetre. Sand, fed by hoppers, is used as an abrasive. After 500 disc revolutions the amount of material abraded is measured by calculation of the weight loss of the aggregate. The percentage loss in mass of chippings is known as the ‘Aggregate Abrasion Value’ (AAV), and ranges from about 1 for hard flints to over 16 for aggregates normally considered too soft for use in road surfacing.