Transportation Engineering Lab Manual
Exp No 1: Aggregate Crushing Value Test
The strength of coarse aggregates is determined by aggregates crushing test. The
aggregate crushing value provides a relative measure of resistance to crushing under a
gradually applied compressive load. To achieve a high quality of pavement, aggregate
possessing low aggregate crushing value should be preferred.
The apparatus for the standard aggregate crushing value test consists of the following:
1. Steel cylinder with open ends and internal diameter 15.2 cm, square base plate,
plunger having a piston of diameter 15 cm, with a hole provided across the stem
of the plunger so that a rod could be inserted for lifting or placing the plunger in
2. Cylindrical measure having internal diameter of 11.5 cm and height 18 cm.
3. Steel tamping rod with one rounded end, having a diameter of 1.6 cm and length
45 to 60 cm.
4. Balance of capacity 3 kg with accuracy upto 1 g and IS sieve of sizes 12.5 mm,
10mm and 2.36 mm for sieving the aggregates.
5. Compression testing machine capable of applying load of 40 tonnes, at a uniform
rate of loading of 4 tonne per minute.
1. The aggregate passing 12.5 mm sieve and retained on 10 mm IS sieve is selected
for standard test. The aggregate is dried by heating at a temperature 1000 C to 1100
C for a period of 4 hours, and then is tested after cooling to room temperature.
2. The cylindrical measure is filled by the test sample of aggregate in three layers of
approximately equal depth, each layer being tamped 25 times by the rounded end
of the tamping rod.
3. The surface of the aggregates is levelled ant the cylindrical measure is weighed.
4. The aggregates are transferred from cylindrical measure to the steel cylinder
resting on the base plate in three layers, each layer being subjected to 25 blows
and the surface is levelled.
5. On top of the sample in the cylinder, plunger is inserted so that it rests on the
surface in level position. Load is applied at a uniform rate of 4 tonnes per minute
until the total load is 40 tonnes and then load is released.