Hi friends, you are welcomed in the world of Civil Allied Gyan. In this article I have explained about rebound hammer test  for concrete, which is also known as non destructive test (NDT) for concrete.


By the help of this blog you can easily find the compressive strength of concrete by using the rebound hammer test for concrete. So please continue to the end & keep your love and support on me.

Rebound Hammer test is a Non-destructive testing method of concrete to find out the compressive strength of concrete using the Rebound Hammer as per IS : 13311 : 1992 (PART– 02). This test provides a convenient and rapid indication.

Rebound Hammer Test  for Concrete Surface or Non – Destructive Test (“NDT”) for Concrete


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

APPARATUS REQUIRED FOR THE TEST:-

  • IS:13311:1992 (PART – 02)


PROCEDURE OF THE TEST:-
  1. Hold the instrument firmly so that the plunger is perpendicular to the test surface.
  2. Gradually push the instrument toward the test surface until the hammer impacts. After impact, maintain pressure on the instrument and if necessary depress the button on the side of the instrument to lock the plunger in its retracted position. 
  3. Read the rebound number on the scale to the nearest whole number and record the rebound number. Take ten readings from each test area. No two impact tests shall be closer together than 25 mm (1 in).
  4. Examine the impression made on the surface after impact, and if the impact crushes or breaks through a near-surface air void, disregard the reading and take another reading.
READING YOUR RESULTS:-
  1. Make at least ten readings from a concrete surface and discard the highest and lowest rebound numbers.
  2. Average the remaining eight numbers. If desired, take a few test readings before you complete your series of ten regular tests.
  3. Use the average rebound number to estimate the strength of the concrete.
  4. Compare your average rebound number to the chart shown on your Concrete Rebound Hammer. 

˃40
Very good hard layer
30 to 40
Good layer
20 to 30
Fair
˂20
Poor concrete

 O
 O
 O
 O
 O
 O
 O
 O
 O
 O

No two impact tests will be closer together than 25 mm (1 in).


https://civilalliedgyan.blogspot.com/2020/03/compressive-strength-test-of-concrete-by-using-rebound-hammer.html
Rebound Hammer

A Schmidt hammer, also known as a Swiss hammer or a rebound hammer or concrete hammer, is a apparatus to measure the elastic properties or strength of concrete or rock, mainly surface hardness and penetration resistance. Rebound Hammer was invented by Ernst Schmidt, a Swiss engineer.

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