STANTMRD
- IS: 2386 (Part4) 1963.
DEFINITION
- Aggregate Impact value is the ratio between the weights of the fines passing 2.36 mm IS sieve and the total sample.
APPARATUS
- Standard Impact Testing machine.
- Cylindrical steel cup 6.3 mm thick and having internal diameter of 102 mm and depth of 50 mm.
- A straight metal tamping rod of circular cross section 10 mm diameter and 230 mm long, rounded at one end.
- 12.5mm, 10 mm and 2.36mm IS sieves, Balance of capacity 500 gms and sensitivity 0.1 gram.
- Thermostatically controlled oven with capacity up to 250 °C.
PROCEDURE
- Take representative sample of aggregates passing 12.5mm IS sieve and retained on 10mm IS sieve.
- Keep the sample in the oven for a period of four hours till the time the weight becomes constant at a temperature of 105 to 110 °C and cool to room temperature.
- Fill the cup in three equal layers, each layer being subjected to 25 strokes with the rounded end of the tamping rod.
- Struck off the surplus aggregates using tamping rod as a straight edge.
- Determine the net weight (A) of the aggregate in the cup.
- Now transfer the material in to the cup of Impact machine, which is fixed firmly in position.
- Compact the material in the cup by a single tamping of 25 strokes with the tamping rod.
- Subject the test sample to a total of 15 blows by the hammer (weighing 13.50 Kg to 14 Kg) of the Impact machine each being delivered at an interval of not less than one second and from a height of 380 ± 5 mm above the upper face of the aggregate.
- Remove the crushed aggregates from the cup and sieve the whole sample on the 2.36 mm IS sieve till no further significant amount passes through the sieve in one minute and weigh (B).
- Weigh the material that has passed through the sieve (C).
- If the total weight (B+C) is less than the original weight (A) by more than one gram, discard the result and conduct a fresh test.
CALCULATIONS
Aggregate Impact Value, (%) = (C/A) x 100
- A Original weight of the oven dried sample.
- C Weight of the material passing through IS sieve 2.36 mm.
REPORT
- Report the individual and the mean results to the nearest second decimal.
PRECAUTION
- Care shall be taken that the Impact machine shall rest with out wedging or packing upon the level plate, block or floor, so that it is rigid and the hammer guide collars are vertical.
DETERMINATION OF AGGREGATE IMPACT VALUE
IS:2386 (Part 4)1963
| Description |
Test I |
Test 2 | Test 3 |
Average |
| Weight of oven dry sample (A) | . | |||
| Weight of fraction retained on 2.36 mm IS sieve after Impact test (B) | ||||
| Weight of fraction passing 2.36 mm IS sieve after impact test (C) | ||||
| Total weight of sample after Impact test(B+C) | ||||
| Impact Value = (C/A) x 100 | ||||
| Specified Limit: 30% Maximum | ||||
| Remarks:
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