Aggregate Impact Value and Crushing Value: What the Numbers Mean

Introduction

You've ordered 100 tons of coarse aggregate for your Bengaluru construction project. The supplier claims it's "Grade A quality, perfect for M25 concrete." But how do you verify this claim?

The answer lies in two critical tests: Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV). These numbers tell you whether your aggregates can withstand the stresses of mixing, handling, and most importantly—load-bearing in hardened concrete.

In this guide, we'll decode what these tests measure, how they're performed, and what the numbers mean for your construction quality in Bengaluru.

Why Aggregate Testing Matters in Concrete Quality

Aggregates (coarse gravel and fine sand) make up 70-80% of concrete volume. While cement gets most attention, aggregate quality is equally critical:

• Weak aggregates crush under load → Concrete loses strength
• Poor impact resistance → Aggregates break during mixing and compaction
• Flaky/elongated particles → Poor interlocking, voids in concrete
• High dust content → Interferes with cement-aggregate bond

In Bengaluru, aggregates come from various sources: - Crushed granite: From quarries in surrounding districts (Kolar, Chikkaballapur) - River sand: Increasingly scarce due to mining restrictions - Manufactured sand (M-sand): Growing alternative, but quality varies

Testing is the only way to ensure your aggregates meet IS code requirements.

Understanding Aggregate Impact Value (AIV) Test

What Is Aggregate Impact Value?

AIV measures the toughness of aggregates—their ability to resist sudden shocks or impact loads without breaking.

Why it matters: - During concrete mixing: Aggregates are subjected to impact from mixer blades - During compaction: Vibrators apply dynamic loads - In pavement construction: Vehicle loads create repeated impact stresses

If aggregates have poor impact resistance, they'll break down into finer particles: - Increases surface area → requires more cement (cost increase) - Creates weak zones in concrete - Reduces durability

AIV Test Procedure (IS 2386 Part IV)

Equipment: Impact testing machine with a 14 kg hammer falling from 380mm height

Steps:

1. Sample preparation:
2. Take aggregates passing 12.5mm sieve, retained on 10mm sieve
3. Fill cylindrical mold in 3 layers
4. Tamp each layer 25 times

5. Total sample weight ~500g

6. Impact application:

7. Raise 14 kg hammer to 380mm height

8. Drop hammer 15 times on the aggregate sample

9. Measurement:

10. Remove crushed sample from mold
11. Sieve through 2.36mm sieve

12. Weigh the material passing through sieve (fines)

13. Calculation:

AIV (%) = (Weight of fines passing 2.36mm / Total sample weight) × 100

AIV Interpretation and Acceptance Criteria

IS 383:2016 Limits: - For concrete: AIV should be < 30% (preferably < 25%) - For pavement construction: AIV should be < 30% (flexible pavements) / < 25% (rigid pavements)

Rule of thumb: Lower AIV = Stronger aggregate = Better concrete quality

Understanding Aggregate Crushing Value (ACV) Test

What Is Aggregate Crushing Value?

ACV measures the compressive strength of aggregates—their ability to resist crushing under gradual compressive loads.

Why it matters: - In structural concrete, aggregates bear compressive stresses - Weak aggregates get crushed, creating voids and reducing strength - Critical for foundations, columns, and load-bearing elements

ACV simulates the crushing action that aggregates experience when concrete is loaded in compression.

ACV Test Procedure (IS 2386 Part IV)

Equipment: Compression testing machine (CTM)

Steps:

1. Sample preparation:
2. Aggregates passing 12.5mm sieve, retained on 10mm sieve
3. Fill cylindrical steel mold in 3 layers
4. Tamp each layer 25 times

5. Level the surface

6. Compression loading:

7. Place mold in CTM
8. Apply load gradually at 4 tonnes per minute

9. Stop when total load reaches 40 tonnes (for 15 minutes hold time)

10. Measurement:

11. Remove crushed sample
12. Sieve through 2.36mm sieve

13. Weigh fines passing through sieve

14. Calculation:

ACV (%) = (Weight of fines passing 2.36mm / Total sample weight) × 100

ACV Interpretation and Acceptance Criteria

IS 383:2016 Limits: - For concrete: ACV should be < 30% (preferably < 25%) - For wearing surfaces (pavements): ACV should be < 30%

Rule of thumb: Lower ACV = More crushing resistance = Stronger concrete

AIV vs ACV: What's the Difference?

Key takeaway: Both tests measure aggregate strength, but in different ways. Strong aggregates score low in both AIV and ACV.

How Aggregate Strength Affects Concrete Performance

1. Compressive Strength

• Weak aggregates (high ACV) limit maximum concrete strength
• Even with high-quality cement testing and proper mix design, weak aggregates = weak concrete

2. Durability

• Crushed particles create microcracks
• Water ingress → corrosion of reinforcement
• Freeze-thaw damage (less relevant in Bengaluru, but critical in cold climates)

3. Workability

• Broken aggregates increase fines content
• Fines increase water demand
• Poor workability → difficult compaction → voids in hardened concrete

4. Economy

• Strong aggregates allow leaner cement mixes (cost savings)
• Weak aggregates require more cement to compensate (higher cost)

Other Important Aggregate Tests

While AIV and ACV are critical, a complete aggregate testing suite includes:

1. Specific Gravity and Water Absorption

• Measures density and porosity
• High absorption → more water required, affects mix design

2. Flakiness and Elongation Index

• Flat/elongated particles create voids
• IS 383 limits: Flakiness < 15%, Elongation < 15%

3. Gradation (Sieve Analysis)

• Particle size distribution
• Proper grading ensures dense packing, less voids

4. Clay and Silt Content

• Dust/clay coats aggregate surface
• Interferes with cement-aggregate bond
• IS 383 limit: < 5% for coarse aggregate, < 8% for fine aggregate

5. Abrasion Value (Los Angeles Test)

• Measures wear resistance
• Critical for pavement aggregates

For comprehensive quality verification, test all parameters at a NABL accredited lab.

Aggregate Testing Procedure: Step-by-Step

Step 1: Sampling

• Collect representative samples from different parts of aggregate pile
• Sample size: ~10-15 kg for lab testing
• Avoid contamination with dust, soil, or foreign materials

Step 2: Sample Preparation

• Wash aggregates to remove dust
• Dry in oven (or air-dry)
• Sieve to required size fractions

Step 3: Laboratory Testing

• Tests performed per IS 2386 (Parts I-IV)
• AIV, ACV, gradation, specific gravity, flakiness, etc.

Step 4: Report Interpretation

• Compare results against IS 383:2016 limits
• Accept/reject aggregate batch based on compliance

Turnaround time: Typically 5-7 working days for complete aggregate testing.

When Should Builders Test Aggregates?

Mandatory Scenarios:

✅ New aggregate supplier or source ✅ Every 100 cubic meters of concrete (or as per project QA/QC plan) ✅ If concrete cube test results are unexpectedly low ✅ For high-strength concrete (M30 and above) ✅ Infrastructure projects (roads, bridges, pavements)

Recommended Frequency:

• At least once per project for residential buildings
• Every batch for commercial/high-rise projects
• Regular monitoring for ready-mix concrete plants

Choosing an Aggregate Testing Lab in Bengaluru

Look for:

✅ NABL Accreditation: Ensures ISO/IEC 17025:2017 compliance ✅ IS code compliance: Tests per IS 2386, IS 383 ✅ Complete testing suite: AIV, ACV, gradation, flakiness, absorption ✅ Fast turnaround: 5-7 days for full aggregate test report

V2 Civil Diagnostics offers comprehensive aggregate testing services, serving Bengaluru builders with reliable, IS code-compliant testing and transparent reporting.

Frequently Asked Questions (FAQs)

1. What is a good aggregate impact value?

For structural concrete, AIV should be < 20%. Values < 10% indicate exceptionally strong aggregates suitable for high-performance concrete. AIV > 30% is unsuitable for load-bearing concrete.

2. What's the difference between impact value and crushing value?

Impact Value (AIV) measures resistance to sudden shocks (dynamic loading). Crushing Value (ACV) measures resistance to gradual compression (static loading). Both indicate aggregate strength.

3. Can I use aggregates with high crushing value?

Aggregates with ACV > 30% are considered weak and not suitable for structural concrete. They may be acceptable for non-structural applications like lean concrete, leveling, or backfill.

4. How often should aggregates be tested?

Test aggregates at least once per new source/supplier. For ongoing projects, test every 50-100 cubic meters of concrete or as specified in your QA/QC plan.

5. What if my aggregates fail AIV/ACV tests?

Reject the batch and request compliant material from supplier. Alternatively, blend failed aggregates with stronger aggregates to improve overall quality (requires expert guidance and retesting).

Conclusion: Strong Aggregates = Strong Concrete

Aggregate Impact Value and Crushing Value aren't just lab numbers—they're indicators of your concrete's future performance. Low AIV and ACV mean strong, durable concrete that will stand the test of time.

Whether you're building a villa in Yelahanka or a commercial complex in Whitefield, never compromise on aggregate quality. Testing is a small investment that prevents massive structural failures.

Ready to Test Your Aggregates?

V2 Civil Diagnostics offers complete aggregate testing services including AIV, ACV, gradation, and all IS 383 compliance tests. NABL accredited, fast turnaround, serving all of Bengaluru.