The aggregate impact value is defined as a relative measure of the resistance of an aggregate to sudden shock or impact, which (in some aggregates) may differ from its resistance to a slow compressive load.


The aggregate impact value test is an important test of aggregates. It is done to obtain the resistance and impact of aggregates (stones). In this test a machine is used, which is called impact testing machine.


The aggregates have sufficient toughness to resist their disintegration due to impact. This property is measured by aggregate impact value test. So that aggregate impact value test is used to determine the relative measure of the resistance of aggregate to sudden shock or impact, which in some aggregate differs from its resistance to a slowly applies compressive load.


The advantages of aggregates impact value test are that the apparatus and procedure of the test are simple. With this test, we can obtain the resistance and impact of aggregates (stones) even in field condition. The test can be done in a short period whether it is at construction site.


Impact value test determines the amount of energy absorbed by a material during fracture. This absorbed energy gives a measure of toughness of a given material and acts as a tool to study temperature-dependent brittle-ductile transition. It is used to determine whether the material is brittle or ductile in nature.


Impact testing machine is commonly used to determine the service life of a part or material. It evaluate an object's capacity to withstand high-rate compressive loading. Impact resistance can be among the most challenging qualities to measure which is measured by impact testing machine. The capacity evaluate this characteristic is particularly useful in assessing product liability and safety.

Aggregate Impact Value Test Procedure, IS 2386 Part 4-1963

Aggregate Impact Value Test Procedure as per IS: 2386 Part-4 (1963)


Hi friends, you are welcomed in the world of Civil Allied Gyan. Here I have explained about Aggregate Impact Test. Read definition, apparatus, IS code, procedure, observations, formula, result and lab report about aggregate impact value test.


  • Impact testing machine
  • Cylinder
  • A straight metal tamping rod of circular cross-section 16 mm in diameter, 45 cm to 60 cm in length and rounded at one end.
  • IS Sieves
  • Oven
  • Weighing balance


  • IS: 2386 (Part 4) -1963, Methods of test for aggregate for concrete
  • IS: 383: 1970, Specification of coarse aggregate and fine aggregate from natural source for concrete
  • IS: 9377: 1979, Specification of apparatus for aggregate impact value test

Aggregate Impact Value Test Procedure, IS 2386 Part 4-1963

Procedure of Aggregate Impact Value Test:-

  1. Take test samples of aggregates passing through 12.5 mm IS sieve and retained on 10 mm IS sieve.
  2. Dry theme in an oven for 4 hours at a temperature of 100 °C to 110 °C and then cool at room temperature.
  3. Fill the aggregates up to about 1/3 full in the cylindrical measure and tamp for 25 times with rounded end of the tamping rod.
  4. Fill the rest portion of the cylindrical measure by two layers (1/3 + 1/3) and tamp each layer for 25 times.
  5. Cut off the overflow of aggregates in cylindrically measure by tamping rod using its straight edge or by a knife.
  6. Then weigh the entire aggregates sample of the measuring cylinder with an accuracy to 0.01 g.
  7. Transfer the aggregates carefully from the cylindrical measure into the cup, which is firmly fixed in position on the base plate of machine.
  8. Then tamp it for 25 times with rounded end of the tamping rod.
  9. The hammer is raised until its lower face be 38 cm above the upper surface of aggregate in the cup and allow it to fall freely on the aggregates.
  10. The test sample (aggregate) is subjected to a total of 15 such blows each being delivered at an interval of not less than 1 second.
  11. Then remove the crushed aggregate from the cup and sieve the whole of it on 2.36 mm IS sieve until no significant amount passes through the sieve.
  12. Weigh the fraction (aggregates) passing through the 2.36 mm IS sieve with an accuracy to 0.1 g.
  13. Repeat the above steps with other fresh sample.
  14. Let the original weight of the oven dry sample of aggregates be W1 g and the weight of fraction (aggregates) passing 2.36 mm IS sieve be W g.
  15. Then aggregate impact value is expressed as the percentage of fines formed in terms of the total weight of the sample.


Observations:-
Table: Impact value of sample aggregates
Observation
Trail 1
Trail 2
Total weight of the aggregate filling the cylindrical metal measures W g


Weight of aggregate  passing  through 2.36 mm sieve W g


Aggregate impact value
= (W/W) 100 %




Calculations:-
Formula for Aggregate Impact Value Test:
Aggregate Impact Value Test Procedure, IS 2386 Part 4-1963

Result:-
Aggregate Impact Value = ………. %


Recommended Values of Aggregate Impact Test:-
Classification of aggregates using Aggregate Impact Value is as given below:
Aggregate Impact Value
Classification
<20%
Exceptionally Strong
10 – 20%
Strong
20-30%
Satisfactory for road surfacing
>35%
Weak for road surfacing


Specified limits of percent aggregate impact value for different types of road construction by Indian Roads Congress are given below:
Sl. No.
Type of Pavement
Aggregate Impact Value Should Not More Than
1.
Wearing Course
30
a)
Bituminous surface dressing
b)
Penetration macadam
c)
Bituminous carpet concrete
d)
Cement concrete
2.
Bitumen bound macadam base course
35
3.
WBM base course with bitumen surfacing
40
4.
Cement concrete base course
45