Aggregate Crushing Value Test: 40-Tonne Load and Limits

The aggregate crushing value (ACV) tells you how well stone holds up when it is squeezed rather than hit. Under a pavement, most of the work is steady pressure: wheel loads pass over and press stone against stone. Weak particles crumble at their contact points and turn into fines, which loosen the structure and can hold water. The crushing test puts a bed of stone under a slowly rising 40-tonne load and measures how much powder it makes.

Crushed stone calculator →

Quick facts

Standards: IS 2386 (Part 4); BS 812-110 in the UK.
Size fraction: passing 12.5 mm, retained on 10 mm.
Mould: open-ended steel cylinder about 15 cm across, with a plunger and base plate.
Load: 40 tonnes, reached at a uniform rate over 10 minutes.
Result: percent passing 2.36 mm; lower is stronger.

Step-by-step procedure

Prepare the sample. Sieve out the 12.5 to 10 mm fraction and dry it. Fill the standard measure in three layers, tamping each 25 times with the rod, level the top and weigh it (A).
Fill the cylinder. Place the cylinder on its base plate and add the stone in three layers, giving each 25 strokes of the rod. Level the surface and set the plunger on top so it sits flat.
Load it. Put the assembly in a compression machine and raise the load evenly so it reaches 40 tonnes in 10 minutes. Then release.
Sieve. Take out the crushed stone, sieve it on 2.36 mm and weigh the fines that pass (B).
Repeat on a second sample and average the two.

Formula and worked example

ACV = (B ÷ A) × 100

Made-up example: the sample weighs 2,850 g. After crushing, 640 g passes the 2.36 mm sieve. ACV = 640 ÷ 2,850 × 100 ≈ 22.5%. A second sample comes in at 23.4%, so the mean of about 23% is reported.

Limits you will see

IS 383, concrete for wearing surfaces (roads, runways, spillways and similar): 30% maximum.
Over 30%: run the ten percent fines test instead; the load that produces 10% fines must be at least 50 kN for those uses.
Very high-strength concrete (M65 and above): IS 383 tightens the crushing value limit to 22%.

Road agencies set their own limits by layer, and surface courses are almost always held to tighter numbers than base or sub-base. The contract specification governs.

The ten percent fines variation

Weak stone can crush so badly under 40 tonnes that the ACV stops telling stones apart. The ten percent fines test runs the same mould with a smaller, chosen load and adjusts until the sample makes between 7.5% and 12.5% fines, then works out the load that would give exactly 10%. The answer is a force, so a higher number is better, which is the opposite of the ACV.

What affects the result

Rock type: dense, fine-grained igneous rock like basalt or trap rock usually beats soft limestone or sandstone.
Shape: flaky and elongated pieces snap more easily, so a quarry with poor crusher settings can fail even with good rock. See our guide to flat and elongated particles.
Moisture: some stones lose strength when wet. A soaked test exposes that.
Loading rate: loading too fast changes how particles break, which is why the 10-minute rate is fixed.

Crushing value vs impact value

The aggregate impact value uses sudden hammer blows on a smaller sample. It is quicker and the machine is cheaper, and IS 383 lets the impact value stand in as an alternative to the crushing value. Most quarries that supply road stone in India and the UK have both numbers on file. In the US, toughness is more often judged with the Los Angeles abrasion test.

Questions people ask

What is aggregate crushing value?

It is the percentage of fines produced when a standard sample of stone is crushed under a slowly applied load. A low value means the stone resists crushing well under the steady weight of traffic.

What load is used in the aggregate crushing value test?

IS 2386 (Part 4) applies a total load of 40 tonnes through a plunger, raised at a uniform rate so the full load is reached in 10 minutes.

What is the ACV formula?

ACV = (mass of fines passing the 2.36 mm sieve / original sample mass) x 100. Two tests are averaged and reported to the nearest whole number.

What is the limit for aggregate crushing value?

IS 383 sets 30% maximum for aggregate used in concrete wearing surfaces such as roads and runways. If the crushing value is over 30%, the ten percent fines test is run instead, and the load needed to make 10% fines must be at least 50 kN.

What is the ten percent fines test?

It is a variation on the same apparatus for weaker stone. Instead of a fixed 40-tonne load, the lab finds the load that produces 10% fines. A higher load means stronger stone.

Is crushing value the same as compressive strength?

No. Compressive strength is measured on a cut cylinder or cube of rock. Crushing value is measured on a bed of loose particles, so it also reflects particle shape and how the pieces bear on each other.

As an Amazon Associate, AsphaltTons.com earns from qualifying purchases. Product links below are sponsored.