The stone aggregates used for the construction of road pavements should possess satisfactory resistance to crushing under the roller during construction and under the application of heavy wheel loads on the pavements during its service life.

The strength of coarse aggregate may be assessed by aggregate crushing test. The aggregate crushing value provides a relative measure of resistance to crushing under gradually applied compression load. Aggregates possessing high resistance to crushing or low aggregate crushing value are preferred for use in high quality pavements.

The apparatus for the standard test consists of a steel cylinder 152 mm diameter with a base plate and a plunger, compression testing machines, cylindrical measure of diameter 115 mm and height 180 mm, tamping rod and sieves.

Dry aggregate passing 12.5 mm IS sieve and retained on 10 mm sieve is filled in the cylindrical measure in three equal layers, each layer being ramped 25 times by the tamper. The test sample is weighted (equal to $W_1 \ g)$ and placed in the test cylinder in three equal layers, tamping each layer 25 times. The plunger is placed on the top of specimen and a load of 40 tonnes is applied at a rate of 4 tonnes per minute by the compression machine. The crushed aggregate is removed and sieved on 2.36 mm IS sieve. The crushed material which passes this sieve is weighted equal to $W_2 \ g.$. the aggregate crushing value is the percentage of the crushed material assuming 2.36 mm sieve in terms of original weight of the specimen.

Aggregate crushing value = $ \frac{100 \ W_2}{W_1} \ percent$