Introduction

The Aggregate Impact Value  Test (AIV) Test measures the resistance of coarse aggregates to impact or sudden shocks. It is one of the most essential mechanical property tests for determining the toughness of aggregates used in road and highway construction.

Objective

To determine the AIV of a sample and assess its suitability for pavement layers such as Granular Sub-base, Cement treated Sub-base (CTGSB), Wet Mix Macadam, Cement treated Base (CTB), BM, DBM & BC and other surface courses.

Reference Standards

• • IS: 2386 (Part IV) – 1963: Methods of Test for Aggregates for Concrete (Mechanical Properties).

• • MoRTH Section 1000 – Table 100-6: Specifications for Road Works.

Apparatus / Equipment

• • The total weight of Impact Machine should not be more than 60 kg nor less than 45 kg.

• • This should have metal bas weighing between 22 kg and 30 kg with a plane lower surface of not less than 300mm dia and shall be supported on a level and plane concrete or stone block or floor at lease 450mm thick. The machine shall be prevented fro rocking either by fixing it to the block or floor or by supporting it on a level and plane metal plate cast into the surface of the block or floor.

• • A cylindrical metal measure, tared to the nearest gram, made of rigid material to withstand rough handling, having internal dimensions of 75 mm diameter and 50 mm depth.

• • A cylindrical steel cup (102mm internal dia and 50mm depth) and not less than 6.3mm thick with its inner surface case hardened, that can be rigidly fastened at the center of the base and easily removed for empying.

• • The testing apparatus includes a metal hammer (13.5–14.0 kg) with a case-hardened cylindrical end (100 mm diameter, 50 mm length, 2 mm chamfer) designed for precise impact testing. The hammer moves freely between vertical guides, ensuring perfect alignment with the test cup. It features an adjustable drop height of 380 ± 5 mm for controlled impact and a support mechanism for safe handling during cup attachment or removal. This setup ensures accurate, consistent, and reliable test results in material testing applications.

• • The test shall be conducted using IS Sieves of sizes 12.5 mm, 10 mm, and 2.36 mm, as specified in IS standards for material grading and particle size analysis.

• • Tamping Rod: A straight metal rod with a circular cross-section of 10 mm diameter and 230 mm length, rounded at one end for uniform compaction.

• • Balance: A weighing balance with a minimum capacity of 500 g (accuracy ± 1 g)

• • Oven: A well-ventilated drying oven capable of maintaining a uniform temperature of 100–110 °C.

• • Metal tray and brush

Sample Preparation

• • Take 500g aggregates passing 12.5 mm and retained on 10 mm IS sieve.

• • Oven-dry the sample for 4 hours at 100–110 °C and cool to room temperature for at least 30min.

• • Weigh the sample accurately (W₁).

         Detailed Test Procedure

• • Divide the sample into three equal parts.

• • Fill the cylindrical measure with the first part, approximately one-third of its volume, and tamp 25 times using the rounded end of the tamping rod.

• • Add the second part, tamp again 25 times, and then add the third part, tamping 25 more times.

• • Level the surface by striking off any excess aggregate using the tamping rod as a straight edge. (this process ensures uniform compaction and accurate measurement of the aggregate’s bulk weight.)

• • Record the net weight of the aggregate to the nearest gram as Weight (A).

• • Now transfer the sample to the impact test mould and gently level it.

• • Secure the mould on the impact machine.

• • The cup shall be fixed firmly in position on the base of the machine and the whole of the test sample placed in it and compacted by a single tamping of 25 storkes of the tamping rod.

• • Hammer Drop: Unlock the hammer and raise it in such a way that its lower face is 380 mm ± 5 mm  above the surface of the sample in the cup and allow it to fall freely total of 15 blows, with each blow delivered at an interval of at least one second..

• • Sieving: Remove the crushed aggregate from the cup and sieve it through a 2.36 mm IS sieve until no significant material passes within one minute.

• • Weighing:
    • Fraction passing the sieve: weigh to 0.1 g accuracy (Weight B).

     

    • • Fraction retained on the sieve: weigh as Weight C.

• • Validation: If the sum of Weight B and Weight C is less than the initial Weight A by more than 1 g, discard the test and repeat.

• • Repetition: Perform two separate tests for accuracy.

• • This ensures reliable measurement of aggregate impact value according to IS standards.

• • Calculate AIV using the formula below.

Calculation

Formula:

AIV=(W2/W1)×100,   

Example:

AIV=75/350×100=21.4%. The result found within specification limit. Hence, satisfactory.

Result

Aggregate Impact Value (AIV) = 21.4 %

Acceptance Criteria (as per MoRT&H / IS)

Significance / Field Application

• • Ensures aggregates can withstand impact loads from traffic.

• • Used for quality control in bituminous and granular layers.

• • Aids in source selection and material approval for highway projects.

Precautions

• • Ensure free fall of hammer—no jerks or obstruction.

• • Dry samples completely before testing.

• • Avoid uneven tamping and ensure uniform filling.

• • Perform duplicate tests for consistency.

Result Interpretation

• • AIV ≤ 20 %: Excellent, strong aggregate (heavy-duty pavement).

• • AIV 20–30 %: Good for normal road works.

• • AIV > 35 %: Unsuitable for surface layers under heavy traffic.

Conclusion

The Aggregate Impact Value Test provides an essential measure of the toughness and shock-resisting capacity of aggregates. Following IS 2386 (Part IV) and MoRTH standards ensures that materials meet the durability and performance criteria required for long-lasting, safe road construction.