---
title: "AIV, AAV, ACV and flakiness/elongation"
subject: "Transportation Engineering I"
chapter: 6
key: "semester_6/transportation_engineering_i:aggregate-impact-abrasion-crushing"
source: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/aggregate-impact-abrasion-crushing
site: BCT Engineering
---

# AIV, AAV, ACV and flakiness/elongation

Transportation Engineering I · Chapter 6: Highway Materials

- Asked in: 2064 Poush (old course), 6+2 marks
- Video: [Flakiness and Elongation Test of Aggregate | Shape test](https://www.youtube.com/watch?v=V_KpeEem0kM) — Civil Site visit
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/transportation_engineering_i/aggregate-impact-abrasion-crushing
- Whole chapter: https://www.bctengineer.com/md/semester_6/transportation_engineering_i/chapter-6

## Question

Distinguish between Aggregate Impact Value, Aggregate Abrasion Value and Aggregate Crushing Value. Why is it necessary to determine flakiness and elongation indices of an aggregate sample?

## Short answer

Aggregate Impact Value measures toughness by 15 hammer blows, % passing 2.36 mm. Los Angeles Abrasion Value measures hardness by 500 revolutions, % passing 1.7 mm. Aggregate Crushing Value measures strength under 40 t load, % passing 2.36 mm. Flakiness and elongation indices limit weak, poorly interlocking particles that reduce stability and increase binder demand.

## Answer

#### Distinguishing the three values

| Point | Aggregate Impact Value (AIV) | Aggregate Abrasion Value (LAAV) | Aggregate Crushing Value (ACV) |
|---|---|---|---|
| Property measured | Toughness: resistance to sudden impact | Hardness: resistance to wear by abrasion and impact | Strength: resistance to gradually applied compressive load |
| Test | Impact machine, 14 kg hammer, 380 mm fall, 15 blows | Los Angeles machine, steel balls, 500 revolutions at 30-33 rpm | Cylinder, 40 t load in 10 min |
| Sample | 10-12.5 mm, 3 layers 25 tamps | 5 or 10 kg of graded aggregate | 10-12.5 mm, 3 layers 25 tamps |
| Result | % fines passing 2.36 mm | % passing 1.7 mm | % fines passing 2.36 mm |
| Formula | $W_2/W_1 \times 100$ | $(W_1 - W_2)/W_1 \times 100$ | $W_2/W_1\times 100$ |
| Typical limit | Not more than 30% (surface), 45% (base) | Not more than 30% (surface), 40-50% (base) | Not more than 30% (surface), 45% (base) |

Good aggregates give low values in all three tests.

#### Why flakiness and elongation indices are needed
- **Flaky** particles (least dimension less than 0.6 times the mean size) and **elongated** particles (length more than 1.8 times the mean size) have a poor shape.
- They are weak and **break easily** under rollers and traffic, which changes the grading.
- They do not interlock or pack well, leaving more voids and giving lower stability and poorer compaction.
- They tend to orient in the same direction, creating weak planes.
- They need more binder for coating in bituminous mixes.

So their quantity is controlled (combined flakiness and elongation index not more than about 30-35%) by determining these indices.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How does the impact value differ from the crushing value?
   A. Impact uses sudden blows (toughness); crushing uses a gradually applied compressive load (strength)
   B. Impact uses steel balls; crushing uses a hammer
   C. Both use the Los Angeles machine
   D. Impact measures weathering
   Answer: A. AIV is toughness, ACV is strength under slowly applied load. (Key point: Impact vs crushing)

2. The abrasion value is the percentage passing which sieve?
   A. 2.36 mm
   B. 1.7 mm
   C. 12.5 mm
   D. 0.075 mm
   Answer: B. AIV and ACV use 2.36 mm; LAAV uses 1.7 mm. (Key point: Abrasion result)

3. Why are flaky and elongated particles undesirable?
   A. They improve interlock
   B. They reduce voids
   C. They break easily, pack poorly and need more binder
   D. They increase stability
   Answer: C. Poor shape reduces stability and compaction. (Key point: Flaky particles)

4. Elongated particles have length more than
   A. 0.6 times the mean size
   B. 3 times the mean size
   C. 0.18 times the mean size
   D. 1.8 times the mean size
   Answer: D. Flaky: least dimension below 0.6 times mean; elongated: length above 1.8 times mean. (Key point: Definition)

## Related in Transportation Engineering I

- [Aggregate crushing value test](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Acrushing-value) — Transportation Engineering I, chapter 6, asked 7×
- [Aggregate impact value test](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Aimpact-value) — Transportation Engineering I, chapter 6, asked 3×
- [Flakiness and elongation index tests](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Afi-ei-test) — Transportation Engineering I, chapter 6
- [Los Angeles abrasion test](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ala-abrasion) — Transportation Engineering I, chapter 6, asked 10×

## Related in other subjects

- [Aggregate crushing value determination](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aaggregate-crushing-value) — Concrete Technology and Masonry Structure, chapter 1
- [Fineness modulus of coarse aggregate (numerical)](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Afineness-modulus-numerical) — Concrete Technology and Masonry Structure, chapter 1