Aggregate Crushing Value Test: Procedure, Calculation, and Limits

A truck parked on a pavement presses its load into the stone below — slowly, steadily, for hours. That is a very different kind of punishment from the sharp hammer blows of moving traffic. The aggregate crushing value (ACV) test measures how aggregate behaves under this slow, crushing load: it gives the crushing strength of the stone, expressed as the percentage of fines produced when the sample is squeezed under a 40-tonne load.

The crushing value test of aggregate is one of the first mechanical tests a site laboratory runs on a new aggregate source — before a single truck is approved for the project. If the aggregate impact value tells you about toughness, the crushing value tells you about strength. Good road and concrete specifications ask for both.

What the Test Measures

Crushing value is the relative resistance of aggregate to crushing under a gradually applied compressive load. The test crushes a standard sample in a steel cylinder under a compression testing machine and measures how much of it breaks down into fines passing a 2.36 mm sieve. A lower percentage means stronger aggregate.

The Standards

• IS 2386 (Part IV) – 1963 — Methods of test for aggregates for concrete; Part 4 covers mechanical properties including the crushing value
• BS 812-110 — Testing aggregates; method for determination of aggregate crushing value (ACV)

Both use the same sample size, the same 2.36 mm sieve, and equivalent loading — BS 812-110 specifies the load in force terms (400 kN reached over 10 minutes, roughly 40 tonnes), while IS 2386 states it directly as 40 tonnes.

Apparatus

Item	Specification
Steel cylinder	Open-ended, 150 mm internal diameter, with plunger and base plate
Compression testing machine	Capable of applying up to 40 tonnes at a controlled rate of 4 tonnes per minute
Cylindrical measure	115 mm internal diameter × 180 mm deep, for preparing the sample
Tamping rod	Straight steel rod, 16 mm diameter, 450–600 mm long, rounded at one end
Balance	Capacity 3 kg, accurate to 1 g
IS sieves	12.5 mm, 10 mm, and 2.36 mm
Oven	For drying the sample at 100–110 °C

Sample Preparation in Detail

The crushing value test of aggregate is only as honest as its sample. A careless sample gives a flattering number that collapses the first time a real load arrives. Do it properly:

1. Collect from several points. Scoop aggregate from at least 4–6 points across the stockpile or from several trucks — never just the top of the heap, where weathered and weaker stone collects.
2. Quarter it down. Mix the collected material thoroughly, form a cone, flatten it, and divide into four quarters. Discard two opposite quarters and repeat until you have roughly the quantity needed. This quartering is what makes the small lab sample represent the whole stockpile.
3. Sieve to size. Pass the reduced sample through 12.5 mm and 10 mm sieves. Use only the fraction passing 12.5 mm and retained on 10 mm — the test is standardised on this narrow size band so results are comparable between labs.
4. Wash if dusty. If the aggregate carries crusher dust or clay coating, wash it and re-sieve. Dust on the surface breaks down into extra fines and inflates the result unfairly.
5. Dry and cool. Dry at 100–110 °C for about 4 hours, then cool to room temperature in a dry place. Testing warm or damp aggregate changes the fracture behaviour.

Practical note: On site, I always prepare the ACV sample on the same day I prepare the impact value sample — the size fraction and tamping are identical, so one quartering session serves both tests and the two results can be honestly compared.

Test Procedure

1. Prepare the sample. Sieve aggregate through 12.5 mm and 10 mm sieves; use the fraction passing 12.5 mm and retained on 10 mm. Dry it at 100–110 °C for about 4 hours and cool to room temperature.
2. Fill the measure. Place the sample in the cylindrical measure in three layers, tamping each layer 25 times with the tamping rod. Level the surface with the rod used as a straight edge. Weigh the sample (this is A).
3. Transfer to the cylinder. Put the test cylinder on its base plate, pour in the sample, level the surface, and insert the plunger so it rests horizontally on the aggregate without jamming against the cylinder walls.
4. Apply the load. Place the whole assembly in the compression testing machine. Apply load at a uniform rate of 4 tonnes per minute so that the full 40-tonne load is reached in 10 minutes. Then release the load.
5. Sieve the crushed material. Remove all the material from the cylinder — take care not to lose any fines — and sieve it on the 2.36 mm IS sieve.
6. Weigh the fines passing the sieve (this is B).

Conduct two tests on the material and report the mean.

Practical note: The 4-tonnes-per-minute rate matters. Ramping the load faster gives a falsely low value because the aggregate has less time to fracture; creeping up slower wastes lab time and can give a falsely high value. Set the machine rate before the test, not during it.

Calculation

Aggregate Crushing Value (ACV) = (B / A) × 100

• A = total weight of the dry sample (g or kg)
• B = weight of fines passing the 2.36 mm sieve (g or kg)

Report the result to the first decimal place.

Worked Example 1

A sample of crushed stone intended for a concrete pavement is tested:

• Weight of dry sample, A = 2.840 kg
• Weight of material passing 2.36 mm sieve, B = 0.625 kg

ACV = (0.625 / 2.840) × 100 = 22.0%

A repeat test gives 21.3%. Mean = 21.7%.

Interpretation: 21.7% is well under the 30% limit for wearing surfaces, so this aggregate is acceptable for the pavement surface course. (See the limits table below.)

Worked Example 2 — A Borderline Result

A second source, a limestone quarry, is tested for a base course:

• Weight of dry sample, A = 2.910 kg
• Weight of material passing 2.36 mm sieve, B = 0.902 kg

ACV = (0.902 / 2.910) × 100 = 31.0%

The repeat test gives 30.2%. Mean = 30.6%.

Interpretation: 30.6% exceeds the 30% wearing-surface limit — this stone cannot go in the surface course — but it is under the 45% limit for base courses and general concrete work. The decision: approve for base course, reject for wearing course. This is exactly the kind of split decision the crushing value test of aggregate exists to support.

Limits: Where Can the Aggregate Be Used?

Use	Maximum ACV
Wearing surfaces — roads, runways, pavements	30%
Other concrete and road work (base courses, general construction)	45%

These are the commonly specified limits under IS 383 (specification for coarse and fine aggregate). Project specifications — for example national highway works — may set tighter values for premium layers, so always check the contract documents.

Typical Crushing Values of Common Rock Types

Knowing what number to expect helps you spot a bad test before it becomes a bad decision. Typical ranges (they vary with quarry and weathering — always test your own source):

Rock type	Typical ACV range	Remarks
Basalt	10 – 15%	Very strong; premium road stone
Granite	12 – 20%	Strong; widely used in concrete
Quartzite	15 – 20%	Hard and durable
Limestone (dense)	20 – 28%	Good for most work; check the quarry
Limestone (soft/chalky)	28 – 35%	Borderline for wearing courses
Sandstone	25 – 35%	Variable — test every new face
Laterite	30 – 40%	Usually only for sub-base and low-grade work

Practical note: If your basalt tests at 32%, don’t blame the rock — suspect the test. Wrong size fraction, lost fines, or a jammed plunger are far more likely than a quarry changing its geology overnight. Re-run before rejecting a source.

Site QC Checklist for the Crushing Value Test

Before you sign the test report, run through this:

• Sample collected from multiple points and quartered — not scooped from the top
• Correct size fraction (12.5–10 mm) confirmed by sieving
• Sample oven-dried and cooled to room temperature
• Three layers × 25 tampings in the measure, surface levelled
• Plunger slides freely, sits level on the aggregate
• Machine rate set to 4 tonnes/min before loading; 40 tonnes reached in 10 minutes
• All material recovered from cylinder — fines brushed off plunger and walls
• Sieving on 2.36 mm complete; fines weighed to 1 g
• Two determinations done; mean reported to one decimal place
• Result compared against the specification limit for the intended use

Common Mistakes in the Crushing Value Test

• Testing an unrepresentative sample. Scooping stone from the top of a stockpile gives you the weathered, weaker fraction. Sample from several points and quarter it down properly.
• Losing fines during transfer. The fines are literally the result you are measuring. Brush every last particle out of the cylinder and off the plunger before sieving.
• Forgetting the second test. The standard requires two determinations and the mean. A single test tells you nothing about repeatability — and one bad tamping job can swing the result several percent.
• Ignoring the plunger fit. If the plunger jams or tilts in the cylinder, the load is no longer uniform and the test is void. It should slide in freely and sit level on the aggregate surface.

ACV vs AIV: Know the Difference

Students and even experienced technicians mix these two up. Here is the clean distinction:

	Crushing value (ACV)	Impact value (AIV)
Measures	Crushing strength — resistance to gradual load	Toughness — resistance to sudden impact
Loading	40 tonnes applied steadily over 10 minutes	15 blows of a 14 kg hammer dropped 380 mm
Apparatus	Steel cylinder + plunger in a compression testing machine	Impact machine with cup and hammer
Sample	12.5–10 mm aggregate, 3 layers × 25 tampings	12.5–10 mm aggregate, 3 layers × 25 tampings
Fines measured on	2.36 mm sieve	2.36 mm sieve
Standard	IS 2386 Part IV / BS 812-110	IS 2386 Part IV / BS 812-112
Wearing-course limit	30%	30%

The identical sample preparation is deliberate: it lets you compare the two numbers directly. A stone that passes ACV but fails AIV is strong but brittle — fine under a parked load, dangerous under traffic shock. A stone that fails both should never go near a pavement.

For a broader picture of how aggregate is qualified for road work, see our roundup of lab tests for water-bound macadam roads.

Frequently Asked Questions

What is the aggregate crushing value test?
A test that measures the crushing strength of coarse aggregate by applying a 40-tonne load gradually over 10 minutes to a standard sample and expressing the fines produced (passing 2.36 mm) as a percentage of the sample weight.

What is the formula for aggregate crushing value?
ACV = (B / A) × 100, where A is the total weight of the dry sample and B is the weight of material passing the 2.36 mm sieve after loading.

What load is applied in the aggregate crushing value test?
40 tonnes, applied at a uniform rate of 4 tonnes per minute so the full load is reached in 10 minutes. BS 812-110 states the equivalent as 400 kN.

What is the maximum crushing value allowed for wearing surfaces?
30%. For other concrete and road work the commonly specified maximum is 45%.

What is the difference between aggregate crushing value and impact value?
ACV measures resistance to a gradually applied crushing load (strength); AIV measures resistance to repeated hammer blows (toughness). Road specifications usually require both.

What sample size is used in the crushing value test of aggregate?
The fraction passing the 12.5 mm sieve and retained on the 10 mm sieve, filled into the standard cylindrical measure in three layers with 25 tampings per layer. The same size fraction is used for the impact value test so the two results are directly comparable.

My crushing value test of aggregate gave 33% — can I still use the stone?
It depends on the use. At 33% the aggregate fails the 30% wearing-surface limit but passes the 45% limit for base courses and general concrete work. Before deciding, re-run the test to rule out sampling or procedure errors — a single high reading should always be confirmed.

Why does the crushing value test take 10 minutes to apply the load?
Because the test simulates a gradually applied (static) load, not an impact. The 4-tonnes-per-minute rate is standardised so every lab fractures the aggregate at the same speed — faster loading gives falsely low values, slower loading wastes time and can inflate the result.

Which is more important for road aggregate — crushing value or impact value?
Both, for different reasons. The crushing value test of aggregate governs slow, heavy loading (parked trucks, compactors); the impact value governs traffic shock. Specifications for wearing courses typically cap both at 30%.

Can recycled concrete aggregate pass the crushing value test?
Sometimes, for low-grade uses. Recycled aggregate usually gives higher ACV values (weaker) because of the old mortar attached to the particles. Test it like any new source and judge it against the same limits — don’t assume it passes.

Final Thoughts

The crushing value test is slow — between drying, tamping, a 10-minute loading cycle, and sieving, one determination takes the better part of a day. But it is the closest laboratory analogue to what aggregate actually endures under heavy, slow-moving loads. Pair it with the impact value, hold surface-course stone to 30%, and you will rarely be surprised by a pavement that starts ravelling from weak stone.

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Written by Mohsin Raza Adil — BSc Civil Engineering Technologist (NTC-registered), Pakistan.