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Created: 2025/07/27 22:20
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## Detn of F.I of Aggregates

- If thickness < 0.6 × mean size, the particle is too thin.
- Such particles are unstable under traffic loads and tend to snap or wear out.
- Poor interlock, increased voids

## Detn of E.I of Aggregates

- If length > 1.8 × mean size, the particle is too long and slender.
- These can bend, twist, or crush under compaction and live loads.
- Difficult compaction, weak structure

**Effects:**

- Lower workability 
- Possibility of breaking down
- Difficulty in meeting VMA in surface courses
- Imped compaction

**Why is the largest size (63–50 mm) omitted for Elongation Index (EI), but included for Flakiness Index (FI)?**

It's excluded by standard due to **handling difficulty**, **low statistical frequency**, and **negligible influence** on overall EI.

**Limits:**

- For asphalt: F.I < 30%; 10% < E.I < 35%
- For concrete: both <= 2.5%

## Detn of Angularity Number

The least angular (most rounded) aggregates are found to have about 33% voids and the angularity number is defined as the amount by which the percentage of voids exceeds 33. The angularity number ranges from 0 to about 12.