The Aggregate Impact Value (AIV) test is an essential procedure in civil engineering and construction to assess the resistance of aggregates against sudden impacts. This test helps determine the durability and suitability of aggregates for various construction applications. Let’s walk through the step-by-step process of conducting the AIV test and the calculation of its results.

Test Apparatus and Materials

To perform the Aggregate Impact Value test, you’ll need the following:

  1. Cylindrical Measure: A cylindrical container with an internal diameter of 75 mm and depth of 50 mm.
  2. Aggregate Impact Testing Machine: This machine consists of a metal hammer mounted vertically and capable of delivering a 14 kg falling weight at a height of 380 mm.
  3. Aggregates: A representative sample of aggregates, thoroughly cleaned and dried.

Test Procedure

Follow these steps to conduct the Aggregate Impact Value test:

  1. Sample Preparation: Obtain a representative sample of aggregates that passes through a 12.5 mm sieve and is retained on a 10 mm sieve. Clean the sample to remove dust and impurities.
  2. Test Apparatus Setup: Set up the aggregate impact testing machine by fixing the base plate securely on a level surface. Place the cylindrical measure on the base plate.
  3. Sample Filling: Fill the cylindrical measure with the prepared sample aggregates until it’s about two-thirds full. Compact the aggregates using 25 strokes of the tamping rod.
  4. Test Execution: Place the machine’s plunger on the aggregates and raise the hammer to its full height. Allow the hammer to fall freely onto the aggregates. The impact should be delivered centrally and perpendicular to the surface.
  5. Impact Application: The aggregates in the cylindrical measure are impacted by the hammer for a total of 15 times. Ensure that each impact is followed by removing the crushed material and re-filling with fresh aggregates.

Calculation of Aggregate Impact Value

The Aggregate Impact Value is calculated using the following formula:

Aggregate Impact Value (AIV)=

(Weight of Material Passing 2.36mm Sieve​ /Original Weight of Sample)×100

Where:

  • Weight of Material Passing 2.36mm Sieve: This is the weight of fines produced from the aggregate sample after impact. Collect the material passing through the 2.36 mm sieve.
  • Original Weight of Sample: This is the weight of the initial aggregate sample used in the test.

Interpretation of Results

Interpret the Aggregate Impact Value as follows:

  • AIV Value less than 10%: Indicates exceptionally strong and durable aggregates suitable for heavy-duty construction.
  • AIV Value between 10% and 30%: Suggests moderately strong aggregates appropriate for general construction purposes.
  • AIV Value greater than 30%: Reflects weaker aggregates that are better suited for light-duty applications.

FAQs:

What is the formula for aggregate impact value?

The formula for calculating the Aggregate Impact Value (AIV) is:
AIV=
(Weight of Material Passing 2.36mm Sieve​ /Original Weight of Sample)×100

What is the use of aggregate impact tester?

The aggregate impact tester is a specialized machine used in civil engineering and construction to assess the resistance of aggregates against sudden impacts. This test helps determine the durability and suitability of aggregates for various construction applications.

What is the aggregate impact value test of WBM?

The Aggregate Impact Value (AIV) test of Water Bound Macadam (WBM) is conducted to evaluate the impact resistance of the aggregates used in WBM road construction. It helps ensure that the aggregates can withstand the stresses and impacts experienced during road usage.

What is the unit of impact value?

Aggregate Impact Value (AIV) is expressed as a percentage. The calculated AIV value indicates the percentage of fines produced from the total weight of the sample aggregates after undergoing the impact test.

Conclusion

The Aggregate Impact Value test is a vital assessment to determine the impact resistance and durability of aggregates. By following the step-by-step process and calculating the AIV value accurately, engineers and construction professionals can make informed decisions about material selection, ensuring the quality and longevity of construction projects.

Know about soundness test of aggregate .