Why This Test Matters in Highway Construction

In highway and pavement engineering, aggregates form the backbone of structural layers such as Sub-Base, Base, and Surface Courses. Their strength directly influences the ability of pavements to resist traffic loads, impacts, and repeated loading without excessive crushing or breakdown.

The Aggregate Crushing Value (ACV) test provides a relative measure of the resistance of aggregates to crushing under gradually applied compressive loads, as defined by IS 2386 (Part IV). Aggregates with a low ACV (i.e., lower percentage of fines) indicate higher strength and durability, which is critical for long-lasting road surfaces and reduced maintenance costs.

As per standard practice, the ACV of aggregates used in wearing surfaces (e.g., concrete pavements) should be controlled rigorously to ensure structural performance over the design life. Aggregates failing this test may lead to premature rutting, surface degradation, and loss of serviceability.

Apparatus

Item	Specification / Notes
Steel cylindrical measure	Internal diameter 115 mm, height 180 mm
Plunger / piston	Diameter 150 mm (for main apparatus)
Tamping rod	Diameter 16 mm (rounded end), length 450–600 mm
Balance	Capacity ≈ 3 kg with 0.01 g accuracy
Compressive testing machine	40 tonnes capacity, uniform loading rate 4 tonnes/min
IS sieves	12.5 mm, 10 mm, and 2.36 mm

Sample Selection & Preparation

Use aggregate passing 12.5 mm and retained on 10 mm IS sieve.
Ensure the aggregates are surface-dry (no visible free moisture).
Sample weight: as required by the cylinder capacity — record dry weight (W1).

Procedure (Step-by-step)

The aggregate passing 12.5 mm IS sieve and retained on 10 mm IS sieve shall be selected for standard test.
The aggregate should be in surface dry condition before testing.
The cylindrical measure shall be 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.
After the third layer is tamped, using the tamping rod as a straight edge levels off the aggregate at the top of the cylindrical measure.
Weigh the sample and repeat the test for another trial.
The cylinder of the test apparatus shall be placed in position on the base plate; place one third of the test sample in this cylinder and tamp 25 times by the tamping rod.
Similarly, the other two parts of the test specimen are added, each layer being subjected to 25 blows.
The surface of the aggregates shall be levelled and insert the plunger so that it rests on this surface in level position.
Keep the cylinder with the test sample and the plunger in position and place on the compression testing machine.
Load is then applied through the plunger at a uniform rate of 4 tons per minute until the total load is 40 tonnes, and then release the total load.
Remove the aggregates including the crushed portion from the cylinder and sieve on a 2.36 mm IS sieve. Collect the material, which passes this sieve.
The above crushing test shall be repeated on second sample of the same weight in accordance with above test procedure. Thus two tests are made for the same specimen for taking an average value.

Calculation

Aggregate Crushing Value (ACV) is the percentage ratio of crushed fines to the total sample weight.

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Aggregate Crushing Value = (W2 / W1) × 100
Where:
W1 = Total dry weight of sample
W2 = Weight of material passing 2.36 mm IS sieve
Report: Mean of two test results

Results & Reporting

Report the mean of the two test values as the final ACV for the aggregate sample. Include:

Sample identification and date
Apparatus used and calibration status
W1 and W2 values for both trials and the mean ACV
Any deviations from standard procedure

Acceptance Limits

Application	Maximum ACV (%)
Cement concrete pavements	30
Wearing surfaces	45

Frequently Asked Questions

Why do we use a 2.36 mm sieve for fines?

2.36 mm is the standard IS limit for defining crushed fines in this test — it provides a consistent basis to compare strength characteristics across aggregate sources.

What if my aggregate grading differs?

If grading is outside the specified range (12.5–10 mm) use a representative fraction or follow the standard practice for coarse/fine fractions as specified in the relevant code.

Notes & Best Practices

Always run two trials and report the mean to reduce random error.
Ensure the compression machine platen and the plunger are clean and parallel before applying load.
Record ambient conditions and any visible degradation of sample during handling.

Aggregate Crushing Value (ACV) Test — Procedure, Calculation & Acceptance Limits

Overview