Crushing value test of Aggregate

The strength of coarse aggregate may be assessed by the aggregate crushing test. The aggregate crushing value provides a relative measure of resistance to crushing under gradually applied compressive load.

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

Dry aggregate passing 12.5 mm IS sieve and retained 10 mm sieve is filled in the cylindrical measure in three equal layers, each layer ramped 25 times by the tamper. The test sample is weighed (W₁) and placed in the test cylinder in three equal layers. The plunger is placed on the top of the specimen and a load of 40 tones are applied at a rate of 4 tones per min by the compressive machine. The crushed aggregate is removed and sieve on a 2.36 mm IS sieve. The crushed material which passes this sieve is weighed equal to W₂g.

Aggregate crushing value = 100W₂/W₁ percent.