## Flakiness and Elongation Index Test

**Flakiness and Elongation Index** **Test **are very **important tests** to be performed on **aggregate **in the laboratory. This test gives the **percentage **of **flaky and elongate aggregate **present in the **total aggregate sample.**

**Aggregate shape, size, and surface texture** majorly affect the **properties **of freshly mixed **concrete **more than the properties of **hardened concrete.**

**Angular, flaky, rough-textured, and elongated aggregate **particles require** more water** to produce **workable concrete **than the **smooth, rounded compact aggregate**. Also, such **irregular**–**shaped aggregate **cement content must also be **increased **to maintain the **water-cement ratio.**

**Elongated and flaky aggregate, **when used in the **construction **of pavement may result in failure of the **pavement **due to their** random position **under repeated **loading and vibration**.

It is **important **to keep the amount of **flaky and elongated aggregate** within **permissible **levels. **Generally**, **flaky **and **elongated aggregate** are avoided or are **limited to about 15 % by the weight of the total aggregate**.

**Read More:** **Aggregate Impact Value Test, Procedure, Result & Standard****s**

**Flakiness Index**

The **flakiness index of aggregate** is the % by** weight of the particles** (aggregates) whose thickness is** less than 3/5 ^{th}(0.6 times)** of their mean dimension.”

**Elongation Index**

The El**ongation index of aggregate** is the % by weight of the **particles **(aggregates) whose length is greater than **1 and 4/5 ^{th} (1.8 times)** of their

**mean dimension.”**

**Objectives**

This **method** uses to measure the **Flakiness Index **and **Elongation index **of aggregate use in the construction of **Highway pavement** and **concrete structures.**

**Reference:- IS 2386 (Part 1) – 1963 PDF.**

**Apparatus**

**Balance**

The **balance **used to measure the **aggregate **has sufficient capacity. Its **accuracy **is 0.1% of the weight of the** test sample.**

**Metal gauge**

The** metal gauge **used to measure the **thickness/elongation** is looked like this figure shown below:

**The IS Sieves: **63 mm, 50 mm,** 40 mm, 31.5 mm**, 25 mm, 20 mm, **16 mm, 12.5 mm**, 10 mm, **6.3 mm**.

SIZE OF AGGREGATES | ||||

PASSING THROUGH IS SIEVES | RETAINED ON IS SIEVE | THICKNESS GAUGE | LENGTH GAUGE | |

1 | 2 | 3 | 4 | |

63 MM | 50 MM | 33.90 MM | 0 | |

50 MM | 40 MM | 27.00 MM | 81.0 MM | |

40 MM | 31.5 MM | 19.50 MM | 58.5 MM | |

31.5 MM | 25 MM | 16.95 MM | 0 | |

25 MM | 20 MM | 13.50 MM | 40.5 MM | |

20 MM | 16 MM | 10.80 MM | 32.4 MM | |

16 MM | 12.5 MM | 08.55MM | 25.6 MM | |

12.5 MM | 10 MM | 06.75 MM | 20.2 MM | |

10 MM | 6.3 MM | 04.89 MM | 14.7 MM |

The **Dimension **shown in the **thickness gauge** is equal to **0.6 times the mean sieve size.**

The Dimension shown in the **length gauge **is equal to** 1.8 times the mean sieve size**

**Read More: Aggregate Crushing Value Test – Procedure and Result**

**Flakiness and Elongation Test Procedure**

**Sample Preparation**

**Prepare** **aggregate **sample for the test by **sieving **between** IS sieve 6.3 mm size **at the bottom and** 63 mm IS sieve **at **top**.

A **separate sample **retains on **each sieve.**

The **collected aggregate **sample should have at least **200 numbers **of individual **aggregate** for **accurate test **results from each range of** IS sieve**.

We take a range of **aggregate samples **retained on** 6.3 mm IS Sieve. **(Separate test can be **conducted **on each range of Sieve).

Take the **weight **of the** total aggregate sample** collected for tests as W1.

**Note: **Test can be **conducted** for each range of **Flakiness gauge slot**.

**Test Procedure for Flakiness Index**

**Separation of Flaky Material**

Try to pass the aggregate width-wise through the slot of** 10mm to 6.3 mm **on a flakiness gauge.

A **separate **sample **passed **through this **slot and weight (W2)**

**Note: **Test can be **conducted **for each range of **Flakiness gauge slot.**

**Observation Table**

Passing through IS sieve(mm) | Retained on IS sieves(mm) | Flakiness Gauge(mm) | Weight passing on Flakiness Gauge (W1) |

63MM | 50MM | 33.90MM | |

50MM | 40MM | 27.00MM | |

40MM | 31.5MM | 19.50MM | |

31.5MM | 25MM | 16.95MM | |

25MM | 20MM | 13.50MM | |

20MM | 16MM | 10.80MM | |

16MM | 12.5MM | 08.55MM | |

12.5MM | 10MM | 06.75MM | |

10MM | 6.3MM | 04.89MM | |

Total |

**Flakiness Index **= Weight of aggregate passed through width gauge 10 mm to 6.3 mm (W2) / Total weight of aggregate sample taken (W1)

** = (W2/W1) x 100**

For example, **Weight **of **aggregate passed **through width gauge of **10 mm to 6.3mm**(W2) = 200 gm and **Total weight of aggregate** sample = **1000 gm**

**Flakiness Index = (200 gm / 1000 gm) x 100 = 20%**

**Result **

The **percentage **of **flaky aggregate **in the range of **10 mm to 6.3 mm** is **20%.**

**Read More: Abrasion Test on Aggregate (Los Angeles Test)**

**Test Procedure for Elongation Index**

**The Following is the procedure for elongation index,**

**Separation of Elongation Material**

Try to pass the **aggregate length**-wise through the slot of **10mm to 6.3 mm **on the **length gauge**.

**A separate sample **retains on this **slot **and **weighted it(W2).**

**Note: **Test can be **conducted **for each range of **elongation gauge** slot**.**

**Observation Table **

Passing through IS sieve(mm) | Retained on IS sieves(mm) | Elongation Gauge(mm) | Weight retain on length Gauge (W2) |

63MM | 50MM | 0 | |

50MM | 40MM | 81.0MM | |

40MM | 31.5MM | 58.5MM | |

31.5MM | 25MM | 0 | |

25MM | 20MM | 40.5MM | |

20MM | 16MM | 32.4MM | |

16MM | 12.5MM | 25.6MM | |

12.5MM | 10MM | 20.2MM | |

10MM | 6.3MM | 14.7MM | |

Total |

**Flakiness Index = ** weight of aggregate retained on length gauge of 10 mm to 6.3 mm (W2) / Total weight of aggregate sample taken (W1)

** = (W2/W1) x 100**

For example, the Weight of aggregate retained on length gauge of 10 mm to 6.3mm(W2) = 150 gm, and Total weight of **aggregate sample **= 1000 gm

**Elongation Index** = **(150 gm / 1000 gm) x 100 = 15%**

**Read More: Aggregate Testing | 7 Test On Aggregates | Coarse Aggregate Test**

**Result**

The **percentage **of** flaky aggregate** in the range of **10 mm to 6.3 mm** is **15%**.

**IRC recommended the Flakiness Index Value**

**IRC recommended the Flakiness index value for road construction be below 35%.**

SR NO. | TYPE OF CONSTRUCTION | ALLOWABLE FLAKINESS INDEX |

1 | WBM construction | |

Wearing surface | 15% | |

lower granular layer | 15% | |

2 | Concrete construction | |

3 | Bituminous construction | 25% |

4 | Two coat bituminous surface dressing | 25% |

5 | Bituminous macadam | |

Base course | 25% | |

Binder course | 25% | |

6 | Dense bituminous macadam | 35% |

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