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Created: 2025/06/29 22:31
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**Experiment No.: 01**

**Name of Experiment:** Determination of Elongation Index of Aggregate Sample

**Method:** BS 812 (Part 1)

**Objectives of the Test:**

* To determine the Elongation Index (E.I.) of a given aggregate sample.
* To identify the proportion of elongated particles in the sample.
* To evaluate the suitability of the aggregate for use in concrete and asphalt works.

**Significance of the Test:**

* Elongated particles can adversely affect the workability and strength of mixes.
* Ensures the aggregate meets shape requirements for specific construction uses.
* Supports appropriate material selection in roads and structural applications.

**Apparatus Used:**

- Oven
- Balance
- Sieve shaker
- Tray
- Thickness gauge
- Sieves

**Datasheet:**

![](../../Resources/image-1.png)

**Test Result:**

The obtained Elongation Index for the aggregate sample was 21.11%.

**Discussion:**

The elongation index of the tested aggregate sample was found to be 21.11%. This indicates that roughly one-fifth of the particles are elongated in shape, meaning their length exceeds 1.8 times their mean dimension. Such elongated shapes can lead to poor interlocking, reduced strength, and workability problems in concrete, which is why standards restrict their use in cement concrete to no more than 2.5%. However, for asphalt mixes, an elongation index between 10% and 35% is generally acceptable, making this sample suitable for flexible pavement construction.

This result is useful for deciding whether such particle may be used for a construction project. While it does not predict the overall performance of aggregates alone, it helps eliminate unsuitable particles that may compromise mix behavior under load. 

The assumed conditions for the test—such as proper sieve sizing, and adequate sample mass per fraction appear to have been met. Each size fraction exceeded the minimum mass required (5%), and elongated particles were identified using the elongation gauge.

The test has some limitations. The classification of elongated particles depends on human judgment, especially for borderline cases. Slight variations in particle positioning during measurement may introduce inconsistency. Also, it was observed in some cases that particles broke during handling leading to further inconsistencies. Despite these issues, the test is relatively reliable when conducted with care.