Aggregate crushing value determination

Aggregate crushing value (ACV) measures the resistance of an aggregate to crushing under a gradually applied compressive load (IS 2386 Part 4). It indicates the strength of the aggregate.

Apparatus

A steel cylinder of 150 mm diameter with a plunger and base plate, compression testing machine, tamping rod (16 mm dia, 45-60 cm long), balance, IS sieves 12.5 mm, 10 mm and 2.36 mm.

Procedure

1. Take aggregate passing the 12.5 mm and retained on the 10 mm sieve, oven-dried at 100-110 °C for 4 hours and cooled.
2. Fill the cylinder in three layers of equal depth, tamping each layer with 25 strokes; level the surface; weigh the sample ($W_1$, about 3 kg).
3. Place the plunger on the sample and position the assembly in the compression machine.
4. Apply the load at a uniform rate so that 400 kN is reached in 10 minutes; then release.
5. Take the crushed aggregate out and sieve over the 2.36 mm IS sieve; weigh the portion that passes ($W_2$).
6. Repeat with a second sample and take the average.

$$\text{ACV} = \frac{W_2}{W_1} \times 100\ \%$$

Limits (IS 383)

ACV not more than 45% for aggregates used in concrete other than wearing surfaces and 30% for wearing surfaces such as roads and pavements. A smaller value means stronger aggregate.