Theory:

Aggregate impact value is measured of toughness of aggregate . Toughness is the property of material which indicate its capacity which impact in sudden. Tougher the aggregate more suitable for wearing surface such as road surface. Lower the impact value stronger the aggregate, again the impact these for good quality concrete , aggregate with lower AIV (Aggregate Impact Value) is prepared. AIV should not be exceed 30 % for concrete used for wearing surface such as road work or runways or earth force or airport. AIV should not be exceed 45 % for concrete used for any non-wearing concrete work such as beam, slab, column etc.

Application:

If follow the toughness that is resistance of the aggregate to impact and thus to decide its suitability for used in concrete.

Items Required:

1.     Aggregate Impact Testing machine.
2.     Tamping rod.
3.     Balance 500 gm over aggregate
4.     Aggregate sample size layer than 10 mm
5.     I.S. sieve 12.5 mm, 10 mm, 2.36 mm

Procedure:

1.    Sample of aggregate is prepared by sieve of aggregate. The sample is passed through 12.5 mm sieve and retained at 10 mm sieve.
2.     Sample is dried in an oven at temperature  between 1000c to 1100c for four hours. Then it is cooled.
3.    Feel the cylindrical level in layer. Each layer was temp by tamping rod. The weight of the sample is noted. (W)The cylindrical steel cup was fixed to the base plate and tamp it with 25 stroks.
4.     Raise the hammer till its lower face is 380 mm above upward surface of the sample and allowed it to fall freely on the sample at an interval not less than 1 second.
5.     The crushing aggregate is removed from the cup and sieved is through 2.36 mm sieve.
6.     Weight the friction pass through 2.36 mm sieve (W1).

Precaution:

1.     The aggregate sample should be sieved and weight correctly.
2.     Each layer should be tamped 2 to 3 time with the help of tamping rod.
3.   The cylinder of test aggregate with aggregate is carefully leveled and the plunger inserted horizontally on the surface.
4.   The hammer weighing 14 kg is raised to a height of 380 mm above the appear surface of aggregate.
5.     Measure the total blows on material not less than one second.

Diagram:


Calculation:

1.       w1/w X 100 = 31/501 X 100 = 6.18 %

2.       w1/w X 100 = 22.5/525 X 100 = 4.16 %

Aggregate % percentage = A+B/2
                                       = 6.18 + 4.16 / 2
                                       = 5.17 %

Observation:

OBS No.
Weight of aggregate      (w)
Weight of fraction passing through        2.36 sieve
% Percentage
1
501 gm
31
6.18 %
2
525 gm
22.5
4.16 %

Observation:

1.       Weight of dry sample w
2.       Weight of the friction passing through 2.36 mm sieve  w1

Sample calculation:

Aggregate Impact Value = w1/w X 100

Conclusion:

1.      The aggregate impact value of the given aggregate is 5.17 %
2.       It is suitable for any road other than road concrete work.

Result:

Aggregate Impact Value (AIV) of given aggregate is = 5.17 %