REBOUND HAMMER CONSTRUCTION NON-DESTRUCTIVE TESTS

REBOUND HAMMER CONSTRUCTION NON-DESTRUCTIVE TESTS

REBOUND HAMMER

AIM

To assess the likely compresive strength of concrete by using rebound hammer as per IS: 13311 (Part 2) – 1992.

PRINCIPLE

1)The rebound of an elastic mass depends on the hardness of the surface against which its mass strikes.

2)When the plunger of the rebound hammer is pressed against the surface of the concrete,

3) The spring-controlled mass rebounds and the extent of such a rebound depends upon the surface hardness of the concrete.

4) The surface hardness and therefore the rebound is taken to be related to the compressive strength of the concrete.

5) The rebound value is read from a graduated scale and is designated as the rebound number or rebound index.

6) The compressive strength can be read directly from the graph provided on the body of the hammer.

Image result for rebound hammer test Related image

                                                     Rebound hammer

PROCEDURE –

1) Before commencement  of  a  test,  the  rebound  hammer should  be  tested  against  the  test  anvil

2) To  get  reliable results, for which the manufacturer of the rebound hammer indicates the range of readings on the anvil suitable for different types of rebound hammer.

3) Apply light pressure on the plunger – it will release it from the locked position and allow it to extend to the ready position for the test.

4)   Press  the  plunger  against  the  surface  of  the  concrete, keeping the instrument perpendicular to the test surface.

5) Apply  a  gradual  increase  in  pressure  until  the  hammer impacts. (Do not touch the button while depressing the plunger. Press the button after impact, in case it is not convenient to note the rebound reading in that position.)

6) Take the average of about 15 readings.

 

INTERPRETATION OF RESULTS

The rebound reading on the indicator scale has been calibrated by  the  manufacturer  of  the  rebound  hammer  for  horizontal
impact, that is, on a vertical surface, to indicate the compressive strength. When used in any other position, appropriate correction
as given by the manufacturer is to be taken into account.

 

 

 

 

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