Created: 2025/07/27 22:20
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.