The Aggregate Impact Value (AIV) test measures the resistance of aggregate to sudden shock or impact, which can differ from its resistance to slow compressive load.
What the Test Measures
AIV expresses the proportion of fines produced when a standard mass of aggregate is subjected to fifteen blows from a falling hammer. A lower AIV indicates a tougher aggregate better able to resist impact in pavements and concrete.
Apparatus Required
- Aggregate impact testing machine with falling hammer and guide
- Cylindrical steel cup and tamping rod
- Test sieves (14.0 mm, 10.0 mm and 2.36 mm)
- Balance and drying oven
NL Scientific manufactures the Aggregate Impact Value Apparatus and the full aggregate & rock testing range, built to ASTM, EN, BS and AASHTO requirements with ISO/IEC 17025 accredited calibration.
Test Procedure
- Prepare aggregate passing 14.0 mm and retained on 10.0 mm; oven-dry.
- Fill the cup in three layers, each tamped 25 times, and weigh the sample (mass A).
- Position the cup and apply 15 blows of the hammer at not less than one-second intervals.
- Remove the crushed sample and sieve it on the 2.36 mm sieve.
- Weigh the fraction passing the 2.36 mm sieve (mass B).
Calculation & Reporting
AIV (%) = (B ÷ A) × 100, reported as the mean of two tests to one decimal place.
Acceptance Criteria
A maximum AIV of about 25–30% is commonly required for surfacing and heavy-duty pavement aggregate, with higher values acceptable for lower-grade applications. Refer to the project specification for exact limits.
Frequently Asked Questions
How does AIV relate to the Ten Percent Fines value?
Both come from BS 812 and assess toughness; AIV is impact-based while Ten Percent Fines is a crushing load test, often used together to characterise aggregate.
Is AIV the same as Aggregate Crushing Value?
No. ACV (BS 812-110) applies a slow compressive load, while AIV (BS 812-112) applies impact. They give related but distinct results.
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