The Aggregate Crushing Value (ACV) test is a standardized procedure used to determine the resistance of coarse aggregates to crushing under a gradually applied compressive load. The test is specified by ASTM C131/C131M (for aggregates smaller than 37.5 mm) and ASTM C535 (for larger aggregates, up to 75 mm).
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ASTM C131/C131M – Standard Test Method for Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Mach
*(Includes ACV-related procedures for smaller aggregates.)*
Key Steps in the Aggregate Crushing Value Test (General Procedure):
1. Sample Preparation:
– Dry the aggregate sample and sieve it to obtain the required size fraction (typically 12.5–10 mm for ASTM C131).
– Fill a cylindrical mold (internal diameter ≈ 152 mm, height ≈ 100–115 mm) in three layers, compacting each layer with a tamping rod.
2. Loading:
– Place the aggregate-filled mold on the compression testing machine.
– Apply a gradually increasing load up to 400 kN (≈40 tons) over 10 minutes.
3. Crushing & Sieving:
– After crushing, remove the sample and sieve it through a 2.36 mm sieve.
– Weigh the material passing the sieve (fines) and retained on it.
4. Calculation of ACV:
\[
\text{ACV (\%)} = \left( \frac{\text{Mass of fines passing 2.36 mm}}{\text{Total mass of sample}} \right) \times 100
\]
A lower ACV indicates stronger, more durable aggregate.
Acceptable Limits:
– For high-quality base courses, ACV should generally be ≤30%.
– For sub-base layers, values up to 45% may be acceptable.
Comparison with Other Standards:
– BS 812-110 (British Standard): Similar but uses a different loading rate and mold size.
– IS 2386-4 (Indian Standard): Follows a comparable method but specifies slightly different sieves.
Would you like details on ASTM C535 for larger aggregates or other related tests like the Los Angeles Abrasion Test?
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