Aggregate Abrasion Value (AAV)
The abrasion test assesses the ability of aggregates to resist surface wear. Insufficient abrasion resistance of aggregates used in road surfacing can result in the loss of texture depth required to maintain skid resistance at high speeds. The relevant standards for this test include British Standard BS 812-3 and European Standard EN 1097-8 Aggregate Abrasion Value (AAV) Test. Although specified in an earlier version of BS 812, the current AAV test, which was introduced in 1951, has superseded the Dorry Abrasion Test.
Test Method
Title: Aggregate Abrasion Value (AAV) Test
Objective: To measure the resistance of aggregates to surface wear by abrasion and determine the percentage loss in mass of chippings, which is known as the Aggregate Abrasion Value (AAV).
Apparatus
A robust welded steel fabrication carrying a steel lap wheel
A precision ground steel shaft located in sealed ball bearings
A grease-filled totally enclosed reduction gearbox
A v-belt drive calibrated to ensure the correct speed of rotation
A resilient-mounted electric motor
Adjustable hoppers for feeding abrasive material
Rotating blades for collecting abrasive material
Steel moulds for manufacturing twin specimens
Procedure
Place two specimens in the steel moulds and compact them.
Mount the specimens on the lap wheel and load them to a specified weight.
Feed abrasive material on to the lap wheel from adjustable hoppers.
After 500 disc revolutions, remove the specimens from the lap wheel.
Collect the abrasive material by rotating blades and transfer it to a collecting hopper for recycling.
Calculate the weight loss of the specimens to determine the Aggregate Abrasion Value (AAV) as a percentage loss in mass of chippings.
Record the AAV value.
Result
The AAV value ranges from about 1 for hard flints to over 16 for aggregates normally considered too soft for use in road surfacings.
Related Test
The Polished Stone Value (PSV) for road surfacing aggregates