The test measures resistance of aggregates to surface wear by abrasion.
The test involves in subjecting a cylindrical specimen of 25 cm height and 25 cm diameter to the abrasion against rotating metal disk sprinkled with quartz sand. The loss in weight of the cylinder after 1000 revolutions of the table is determined.
The hardness of the rock sample is expressed in an empirical formula.
Hardness = 20 – (Loss in Grams/3)
Good aggregate should show an abrasion value of not less than 17. A aggregate sample with a value of less than 14 would be considered poor.