Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV): Test Procedures and Applications

Aggregates form the structural backbone of concrete and road pavements, yet their performance under mechanical stress varies widely. Two standardised tests—Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV)—quantify how well aggregates resist sudden shock and gradual compression. These properties directly influence the long-term durability of concrete">reinforced concrete structures and highway surfaces subjected to repeated loading.

What is Aggregate Impact Value?

The Aggregate Impact Value measures an aggregate's resistance to sudden impact or shock loading. This characteristic, known as toughness, becomes critical in applications where materials face abrupt force—vehicle braking zones, speed breakers, or undulating road profiles. The test quantifies the fraction of material that fractures into fines when subjected to standardised hammer blows.

During the test, aggregate samples passing through 12.5 mm sieves and retained on 10 mm sieves are placed in an impact testing machine cup in three layers, each tamped 25 times. A hammer falls 15 times from a height of 38 cm. The crushed material is then sieved through a 2.36 mm sieve, and the fraction passing through is weighed. The AIV is calculated as the ratio of the weight of material passing through the sieve (W2) to the total sample weight (W1), expressed as a percentage.

Interpreting AIV Results

Lower AIV values indicate better resistance to impact loading. Typical thresholds for aggregate quality include:

For engineers selecting aggregates for ready-mix concrete or pavement design, these values provide a direct comparison of material toughness across suppliers and quarries.

What is Aggregate Crushing Value?

The Aggregate Crushing Value test evaluates an aggregate's resistance to crushing under a gradually applied compressive load. This differs fundamentally from the sudden impact measured in AIV testing. The ACV test simulates the sustained pressure aggregates experience beneath pavement layers or within high-strength concrete mixes.

The test procedure mirrors the AIV setup: aggregate samples passing through 12.5 mm sieves and retained on 10 mm sieves are placed in a cylindrical measure in three layers, tamping each layer 25 times. The sample is then subjected to a compressive load applied gradually at a rate of 4.5 kN/s until crushing occurs. After crushing, the material is sieved through a 2.36 mm sieve, and the fraction passing through is weighed. The ACV is calculated using the same formula as AIV: the ratio of crushed material (W2) to total sample weight (W1), multiplied by 100.

ACV Thresholds for Construction Applications

Lower ACV values indicate stronger aggregates with better load-bearing capacity:

These thresholds guide material selection for projects where sustained compression—rather than shock—dominates the load profile. For instance, aggregates in graded base courses must resist long-term consolidation without excessive fines generation.

How AIV and ACV Differ

Both tests measure mechanical degradation, but their loading regimes reflect distinct failure modes. AIV simulates sudden, dynamic forces—hammering, vehicle impact, or repeated shock—while ACV replicates slow, static compression typical of deep pavement layers or structural concrete under permanent load. Aggregate performance in one test does not predict performance in the other. A material with excellent crushing resistance may still disintegrate under repeated impact if its internal grain structure is brittle.

Engineers must therefore consult both values when specifying aggregates. Highway surface courses, exposed to braking and acceleration forces, demand low AIV. Deep base layers, subjected to sustained vehicle loads, require low ACV. In reinforced concrete beams or columns, both properties matter: aggregates must withstand construction handling (impact) and long-term service loads (compression).

Practical Selection Criteria

For concrete pavements and structural applications, aggregates with ACV below 30% and AIV below 30% ensure adequate strength and toughness. Bituminous road surfaces tolerate slightly higher ACV values—up to 45%—if traffic volumes and axle loads remain moderate. Where aggregates fail either test, engineers must either source alternative materials or adjust mix designs to compensate, often by increasing binder content or adding supplementary cementitious materials like fly ash or ground granulated blast-furnace slag.

Both tests are governed by IS Code 2386 (Part 4) – 1963, providing standardised procedures that enable cross-project and cross-regional comparisons. Quarry operators and aggregate suppliers routinely publish AIV and ACV data, allowing procurement teams to pre-qualify materials before mix design trials commence.

Why Both Tests Matter

Aggregates represent 60–80% of concrete volume and form the load-bearing skeleton of pavements. Material failure—whether through brittle fracture under impact or gradual crushing under compression—initiates surface cracking, pothole formation, and structural distress. By quantifying toughness and crushing strength, AIV and ACV tests give engineers the data needed to match materials to loading conditions, extend service life, and avoid costly premature failure. For projects ranging from high-performance concrete to highway rehabilitation, these simple yet robust tests remain indispensable tools for material qualification.