Sample Collection: The Standard aggregate should pass through 14.0 mm sieve and retain on a 10.0 mm sieve.
Apparatus:
1) An AIV testing machine is showing below and consists of:
* Weight should be 45-60 kg.
* Machine shall have a circular metal base weighing between 22-39 kg, with a plane lower surface of not less than 300 mm diameter and supported on a level and plane concrete or stone block or floor at least 450 mm thick.
* A cylindrical steel cup with an internal diameter of 102 mm and internal depth of 50 mm.
* A metal hammer weighing 13.5 kg to 14.0 kg of cylindrical shape.
2) Test sieve of sizes 14.0 mm, 10.0 mm and 2.36 mm.
3) A cylindrical metal measures of sufficient rigidity to retain its form under rough usage and with an internal diameter of 75(+/-)1 mm and an internal depth of 50(+/-)1 mm.
4) A tamping rod of 10 mm diameter, 230 mm long, rounded at one end.
5) A balance of capacity not less than 500 gm and accurate to 0.1 gm.
Test Procedure:
1) Rest the impact machine, upon the level plate, block or floor, so that it is rigid and the hammer guide columns are vertical.
2) Fix the cup firmly in position on the base of the machine and place the whole of the sample in it and compact by a single tamping of 25 strokes of the tamping rod.
3) Adjust the height of the hammer so that its lower face is 380(+/-)5 mm above the upper surface of the aggregates in the cup and then allow it to fall freely on the aggregates. Subject the test sample to a total of 15 such blows, each being delivered at an interval of not less than 1 second. No adjustment for hammer height is required after the first blow.
4) Then remove the crushed aggregates by holding the cup over a clean tray and hammering on the outside with a suitable rubber mallet until the sample particles are sufficiently disturbed to enable the mass of the sample to fall freely on the tray. Transfer fine particles adhering to the inside of the cup and the underside of the hammer to the tray by means of a stiff bristle brush. Sieve the whole of the sample in the tray, for the standard test, on the 2.36 mm (#8) test sieve until no further significant amount passes in 1 min.
5) Repeat the whole procedure starting from the beginning using a second sample of the same mass as the first sample.
Calculation:
1) The ratio of the mass of fines formed to the total sample mass in each test shall be expressed as a percentage, the result being recorded to the first decimal place.
Percentage of the fraction passing the 2.36 mm (#8) sieve = ( B*100)/A
where,
A = weight of surface-dry sample.
B = weight of fraction passing the 2.36 mm (#8) sieve
* the average of two determination is taken as the Aggregate Impact Value ( AIV)
Now Classification of aggregate using Aggregate Impact Value are as follows:
Aggregate Impact Value | Classification |
| <20% | Exceptionally strong |
| 10-20% | Strong |
| 20-30% | Satisfactory for road surfacing |
| >35% | Weak for road surfacing |
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