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## What Is Aggregate Impact Value?

** It **is the** ability of aggregates **that resist sudden **impact or shock load on it.** Also, it can be defined as** **the** resistance of aggregate** to failure by **impact load** is known as the** Impact Value **of Aggregate**.**

The** characteristic **of any material to** resist sudden impact** is known as **toughness. **When we use **aggregate **in roads and pavement on which vehicular movement is done and there is a **possibility **of impact load on **aggregate**.

This **impact load** can break aggregate into **smaller **pieces and which results in the** failure of roads **and **pavements.**

Therefore, the **aggregate **used for such a proposal should have **sufficient **toughness to resist their disintegration due to the **impact**. This important property of **aggregate **is **determined **by the **aggregate **impact value test.

This** resistance of aggregate** may differ from resistance to gradual load which we measure in the **crushing value test.**

**Importance of Impact Test on Aggregates**

The **impact test on aggregate** is carried out to know the **response **of aggregates to different kinds of loads that the **aggregates **will be subjected to **during **their service life.

The need **impact value test **is used to measure the **toughness **of aggregates which is nothing but the ability of **aggregates **to resist the sudden **loading **or impact loading.

Finding out the impact** resistance of aggregate** is important because, **during **service life, the **aggregates **will be actually **subjected **to this type of load. For **example**, aggregates will be subjected to impact after **speed **breaker, when the vehicle is moving on the **undulating **road, etc.

So, by **AIV Test, **we can find out the response of **aggregates** to sudden loading. If the result is **satisfactory**, we use those aggregates in pavement. If not, **aggregates **are rejected.

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

**Objectives of Impact Value Test**

**This method of test is **used to measure the impact value of **aggregate **use in the construction of Highway pavement and **concrete structures.**

**Reference:-** Aggregate impact value test IS Code is** 2386 (Part 4) – 1963 PDF **

**Test ****Apparatus**

**Apparatus**

**1. Impact testing machine**

**2.** The **total weight of the machine **used in the test is not **more than **60kg or not less than** 45 kg.**

**3.** **A steel cup shape** as a** cylinder** usually has internal **dimensions**:

**Diameter = 102mm**

**Depth = 50mm**

**Thickness = 6.3mm**

**4. 13.5 to 14 kg hammer with the end of cylindrical shape** is used for the impact load:-

**Diameter = 100mm**

**Length = 50mm**

**Chamfer at lower edge = 2mm**

**5. Sieves:-** The following** IS sieves** are used

**12.5mm****10mm****2.36mm**

**6. Measure**

The **cylinder** was made with the **steel **used.

**The following internal dimensions are:**

**Diameter = 75mm****Depth = 50mm**

**7. Tamping rod**

A **straight tamping **rod made with the metal of **circular c/s **is used to **tamp **the aggregate. Rounded at the end.

**The following are the dimension of the rod:**

**Diameter = 10mm****Length = 230mm**

**8. Balance**

A **balanced **used for the weight **measure **is not less than 500 gm, or it is readable or its accuracy is up to** 0.1gm.**

**9. Oven**

The oven used for drying the **aggregates **is well ventilated or is **thermostatically controlled **to maintain the **temperature **in the oven from **100 to 110 °C**.

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

**Preparation of Aggregate Sample**

- The
**aggregate**uses for the**sample**are passed through the**12.5mm IS sieve**and retained on the**10mm IS sieve.** - The aggregate which is retained on the
**10mm sieve**is dried in an oven for a time period of**4 hours**at the oven**temperature**of**100 to 110º C.** - The
**cylindrical measure**used for the collection**sample**filled about**1/3 full**with the aggregates and it**tamped 25 stokes**with help of the**rounded**end of the tamping rod. Further**similar 1/3 quantity**of aggregates are filled in it and again**25 stokes**are given. Then measure is finally**filled**to overflowing then apply 25 stokes again and the extra aggregates are removed from the**measure**with the help of the**straight**portion of the**tamping rod**.

**The Procedure of Impact Test of Aggregate**

- The
**impact machine**is rest on a**horizontal flat surface**like the level plate, block, or floor without any**packing**. So, the application of a hammer is**straight**and vertical. - The
**cup**is fixed in a**proper position**on the base of the**impact machine**. - Transfer
**aggregate**sample from**cylindrical measure**to cut fitted in an impact test machine and apply**25 strokes**of the rod to**compact it**. - Then the
**hammer**is lifted 380mm and falls on the**upper surface**of the**aggregate**which fills in the**cup**. - A total of
**15 blows**are applied to the cup each**delivered**at an interval of not less than 1**second**. - The
**crushed aggregates**are removed from the cup and the**crushed sample**is sieved from the 2.36mm**IS****sieve**. - Weight the fraction of sample
**passing**through**2.36mm IS sieve**accuracy up to**0.1 gm. (W1)** - Weight the fraction of sample retains on the
**2.36mm IS sieve.**( weight W2) - The total weight of the
**sample (W1 + W2**) is less than the initial weight (weight W) by more than one**gram**than the result**discarded**.

**Calculation**

- The aggregate impact value is the ratio of the weight of the fraction passing through 2.36 mm (weight W2) by the total weight of the sample (weight W1 + W2).

**Aggregate Impact Value =** (W2/ (W1+W2)) * 100

= 80 gm / 300 gm

** = 26.67 **(Impact Value)

Where,

W1= Weight of the fraction passing through a 2.36 mm IS sieve. (220 gm)

W2= Weight of sample retained on 2.36 mm IS sieves. (80 gm)

W1+W2 = Total Weight of Sample (220 + 80 = 300 gm)

**Result: **The Aggregate Impact Value is _________.

**Recommended Aggregate Impact Test Values**

**Recommended Aggregate Impact Test Values**

Aggregate Impact value | Nature |

<20% | Exceptionally strong |

10-20% | Strong |

20-30% | Satisfy for surface course |

>35% | Weak for surface course |

**Maximum Allowable Impact Value of Aggregate for Different Types of Pavements**

Sr. No. | Types of Pavements | Aggregate Impact Values (Max.) |

1 | Water Bound Macadam (WBM) Sub-Base Course | 50 |

2 | Cement Concrete, Base Course | 45 |

3 | i) WBM base course with bitumen surfacing | 40 |

ii) Built up- Spray grout, base course | ||

4 | Bituminous macadam, base course | 35 |

5 | i) WBM, surface Course ii) Buit-up spray grout, surface course iii) Bituminous penetration macadam iv) Bituminous macadam, binder Course v) Bitumen surface dressing vi) Bitumen carpet vii) Bituminous / Asphaltic concrete | 30 |

## FAQs:

**What Is the Aggregate Impact Value Test?**

**Aggregate Impact Value **is the** ability of aggregates **that resist sudden **impact or shock load on it.** Also, it can be defined as the** resistance of aggregate** to failure by **impact load** is known as the **Impact Value of Aggregate.**

**What is the Main Objective of the Aggregate Impact Test?**

The **aggregate impact value** test is carried out to know the response of aggregates to different kinds of loads that the **aggregates** will be subjected to **during their service life. **Finding out the impact** resistance of aggregate** is important because, during service life, the aggregates will be actually subjected to this type of load.

**Is code for Impact Test of Aggregate?**

**Aggregate Impact** Value **Test** is conducted as per IS 2386 (Part 4)-1963.

**What is the Use of the Impact Test?**

The **aggregate impact value** test is carried out to know the response of aggregates to different kinds of loads that the aggregates will be subjected to during their service life.

**Impact Value**

**It **is the** ability of aggregates **that resist sudden impact or shock load on it. Also, it can be defined as the** resistance of aggregate** to failure by **impact load**. This **impact load** can break aggregate into smaller pieces and which results in the** failure of roads and pavements.**

**Impact Test of Aggregate**

**It **is the** ability of aggregates **that resist sudden **impact or shock load on it.** Also, it can be defined as the** resistance of aggregate** to failure by **impact load** is known as the **Impact Test of Aggregate**

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