IMPACT VALUE TEST OF COARSE AGGREGATE

IMPACT VALUE TEST OF COARSE AGGREGATE 

AIM:

To determine the Impact Value of the coarse aggregate.



APPARATUS:

1. Sieve size of 12.5mm, 10mm, 2.36mm

2. Aggregate Impact tester

3. Weighing balance                                  

4. Measuring Cylinder

5. Tamping rod

6. Oven

PROCEDURE: 

1. Take the sample of aggregate collected from IS Sieve passing 12.5mm and retained on 10mm.

2. Dry the aggregate at 100 - 1100 C in oven for not exceeding 4 hours and then cool it.

3. The cylindrical steel cup is filled with 3 equal layers of aggregate and each layer is tamped 25 strokes by the rounded end of tamping rod.

4. The net weight of aggregate in the cylindrical steel cup is determined and noted as WA.

5. The impact machine shall rest without wedging or packing upon the level plate, block or floor, so that it is rigid and hammer guide columns are vertical.

6. The cup is fixed firmly in position on the base of the machine and the whole of the test sample is placed in it and compacted by a single tamping of 25 strokes of tamping rod.

7. The hammer of 14 Kg is raised 380mm above surface of the aggregate in cup and allowed to fall freely onto the aggregate 15 times, each being delivered at an interval of not less than one second.

8. The crushed aggregate is removed from the cup and sieved on 2.36 mm.

9. The fraction passing the sieve is weighed to an accuracy of 0.1 g (WB).

NOTE: The aggregate retained on the sieve shall be weighed (Wc). If the total weight of WB and Wc is less than initial weight of WA by more than one gram the result shall be discarded and the test to be repeated.

CALCULATION:

Aggregate Impact Value in % = (WB / WA) x 100  

WA - weight of oven dried sample

WB – weight of aggregate passing through 2.36mm IS sieve


NOTE:

Acceptable Value – Impact value should not be more than 45% 


REFERENCE: 

IS: 2386(PART 4)-1963 




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