Apparatus for Aggregate Impact Test The apparatus as per IS 2386 (Part IV) - 1963 consists of (i) A testing machine weighing 45 to 60 kg and having a metal base with a painted lower surface of not less than 30 cm in diameter. It is supported on a level and plane concrete floor of a minimum 45 cm thickness. The machine should also have provisions for fixing its base. (ii) A cylindrical steel cup of internal diameter 102 mm, depth 50 mm and minimum thickness 6.3 mm. (iii) A metal hammer or tup weighing 13.5 to 14.0 kg the lower end being cylindrical in shape, 50 mm long, 100.0 mm in diameter, with a 2 mm chamfer at the lower edge and case hardened. The hammer should slide freely between vertical guides and be concentric with the cup. Free fall of the hammer should be within 380±5 mm. (iv) A cylindrical metal measure having an internal diameter of 75 mm and depth of 50 mm for measuring aggregates. (v) Tamping rod 10 mm in diameter and 230 mm long, rounded at one end. (vi) A balance of capacity not less than 500g, readable and accurate up to 0.1 g. The property of a material to resist impact is known as toughness. Due to movement of vehicles on the road the aggregates are subjected to impact resulting in their breaking down into smaller pieces. The aggregates should therefore have sufficient toughness to resist their disintegration due to impact. This characteristic is measured by the impact value test. The aggregate impact value is a measure of resistance to sudden impact or shock, which may differ from its resistance to gradually applied compressive load. Procedure of Aggregate Impact Test The test sample consists of aggregates sized 10.0 mm 12.5 mm. Aggregates may be dried by heating at 100-110° C for a period of 4 hours and cooled. (i) Sieve the material through 12.5 mm and 10.0mm IS sieves. The aggregates passing through 12.5mm sieve and retained on 10.0mm sieve comprises the test material. (ii) Pour the aggregates to fill about just 1/3 rd depth of measuring cylinder. (iii) Compact the material by giving 25 gentle blows with the rounded end of the tamping rod. (iv) Add two more layers in similar manner, so that cylinder is full. (v) Strike off the surplus aggregates. (vi) Determine the net weight of the aggregates to the nearest gram(W). (vii) Bring the impact machine to rest without wedging or packing up on the level plate, block or floor, so that it is rigid and the hammer guide columns are vertical. (viii) Fix the cup firmly in position on the base of machine and place whole of the test sample in it and compact by giving 25 gentle strokes with tamping rod. (ix) Raise the hammer until its lower face is 380 mm above the surface of aggregate sample in the cup and allow it to fall freely on the aggregate sample. Give 15 such blows at an interval of not less than one second between successive falls. (x) Remove the crushed aggregate from the cup and sieve it through 2.36 mm IS sieves until no further significant amount passes in one minute.

1. Experiment Name: Aggregate Impact Value
Prepared By
Nurmohammad
Department of Civil Engineering
Dhaka International University

2. Experiment Name: Aggregate Impact Value
IS 2386 (PART-IV)

3. The impact test is a type of quality control test for highway pavements that
is used to determine the suitability of aggregates for use in highway
pavement construction. Aggregates used in road construction should be
strong enough to resist abrasion, crushing, and impact load.
Objective
Based on the impact value, we can decide whether the coarse aggregate is
suitable for construction or not. This test is performed to ensure the
aggregate toughness, which is used in road construction to work as a base
layer, and sub-base layer.
Significance and use

4. Apparatus
A testing machine weighing 45 to 60 kg and having a
metal base with a painted lower surface of not less
than 30 cm in diameter. It is supported on level and
plane concrete floor of minimum 45 cm thickness.
The machine should also have provisions for fixing its
base.
Impact Testing Machine

5. Apparatus
A cylindrical steel cup of internal
diameter 102 mm, depth 50 mm
and minimum thickness 6.3 mm.
102 mm
50 mm
Cylindrical Steel Cup

6. Apparatus
75 mm
50 mm
Cylindrical Metal Measure
A cylindrical metal measure having
internal diameter 75 mm and depth 50
mm for measuring aggregates.

7. Apparatus
A metal hammer or tup weighing 13.5 to
14.0 kg the lower end being cylindrical in
shape, 50 mm long, 100.0 mm in
diameter, with a 2 mm chamfer at the
lower edge and case hardened. The
hammer should slide freely between
vertical guides and be concentric with the
cup. Free fall of hammer should be within
380±5 mm.
Hammer

8. Apparatus
Tamping rod 10 mm in diameter and 230
mm long, rounded at one end.
Tamping Rod

9. Apparatus
Weighing Balance
A balance of capacity not less than
500g, readable and accurate up to
0.1 g.

10. 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.
Drying Oven
Apparatus

11. Apparatus
Sieves
12.5 mm, 10 mm and 2.36 mm IS sieves
are required for this test.

12. Apparatus
Tray

13. Preparation Of Test Specimen
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.

14. Preparation Of Test Specimen
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.

15. Preparation Of Test Specimen
6. Then weigh the entire aggregates sample of the measuring cylinder with an
accuracy to 0.01 g.

16. Preparation Of Test Specimen
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.

17. Procedure
9. The hammer is raised until its lower face be 380 mm 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.

18. Procedure
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.
2.36mm IS
Sieve

19. 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 W₂ g.
15. Then aggregate impact value is expressed as the percentage of fines formed
in terms of the total weight of the sample.
Procedure

20. Observations Sample 1 Sample 2
Total weight of dry sample (W1 gm) 357.7 342.8
Weight of portion passing 2.36 mm sieve (W2 gm) 25.3 30.5
Aggregate Impact Value (percent) =
𝑊2
𝑊1
X 100 7.07% 8.89%
Mean (percent) 7.98%
Calculation
Result of Impact Test= 7.98%

21. Recommended Aggregate Impact Test Values
Aggregate Impact Value Classification
<20% Exceptionally Strong
10 – 20% Strong
20-30% Satisfactory for road surfacing
>35% Weak for road surfacing

22. Thank You