Methodology For Aggregate Impact Value (AIV) Test

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The Aggregate Impact Value (AIV) test is a standard test method used to assess the resistance of aggregates to impact. It is outlined in the Indian Standard IS 2386 Part IV. Here is a general methodology for conducting the Aggregate Impact Value test as per the Indian Standard:

Apparatus:

  1. Impact testing machine: The machine should conform to IS: 2386 (Part IV)-1963.
  2. Cylindrical steel cup: The cup shall be of internal diameter 102 mm and depth 50 mm, with minimum wall thickness of 6.3 mm.
  3. Metal hammer: Circular, about 75 mm in diameter and between 13 to 15.6 kg in weight.
  4. Balancing scale: The balance shall be sensitive to 0.5 g and its capacity at least 500g.

Sample Preparation:

  1. The aggregate sample: The aggregate used for the test should consist of particles passing through 12.5 mm and retained on 10 mm sieve.
  2. Test sample: The test sample should be dried to a constant mass at a temperature of 100 to 110°C.

Procedure Aggregate Impact Value (AIV) test :

  1. The cup: Fix the cup firmly in the machine and place the whole of the test sample in it.
  2. The hammer: Raise the hammer until it falls freely on the aggregate, allowing it to impact on the surface of the aggregate for 15 times.
  3. Repeat the test: Carry out the test in the same manner with the remaining portion of the aggregate.
  4. Calculation: Calculate the aggregate impact value by dividing the weight of the fines passing through the specified IS sieve to the total weight of the sample.

Calculation Formula:

Interpretation:

  • The aggregate impact value should not exceed 45% for aggregate to be used in concrete for wearing surfaces.
  • For bituminous concrete, the maximum permissible value is 30%.

Precautions:

  1. The test should be conducted in a dry place.
  2. The aggregate should be free from dust.
  3. The cup and the hammer should be cleaned before each test.
  4. Care should be taken to avoid unnecessary shock or vibration during the test.

Always refer to the latest version of the Indian Standard (IS 2386 Part IV)

EXAMPLE OF Aggregate Impact Value (AIV) test

A hypothetical example of conducting an Aggregate Impact Value (AIV) test.
Suppose you have an aggregate sample with the following details:

  • Weight of the aggregate sample = 2000 grams
  • Aggregate passing through 12.5 mm sieve = 1200 grams
  • Aggregate retained on 10 mm sieve = 800 grams
  • Weight of fines passing through 2.36 mm sieve = 150 grams

Calculation:

Interpretation:

In this example, the Aggregate Impact Value (AIV) is 7.5%, which is well below the permissible limit for concrete wearing surfaces (45%) and bituminous concrete (30%). This suggests that the tested aggregate has good resistance to impact.

Remember, this is a simplified example, and actual values may vary based on the specific characteristics of the aggregate and the testing conditions. Always follow the precise procedures outlined in the relevant standards for accurate and reliable results.

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