Updated: May 1, 2020



To assess the likely compresive strength of concrete by using

rebound hammer as per IS: 13311 (Part 2) - 1992.


The rebound of an elastic mass depends on the hardness of the

surface against which its mass strikes. When the plunger of the

rebound hammer is pressed against the surface of the concrete,

the spring-controlled mass rebounds and the extent of such a

rebound depends upon the surface hardness of the concrete. The

surface hardness and therefore the rebound is taken to be

related to the compressive strength of the concrete. The rebound

value is read from a graduated scale and is designated as the

rebound number or rebound index. The compressive strength can

be read directly from the graph provided on the body of the





i) Before commencement of a test, the rebound hammer

should be tested against the test anvil, 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.

ii) 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.

iii) Press the plunger against the surface of the concrete,

keeping the instrument perpendicular to the test surface.

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.)

iv) Take the average of about 15 readings.


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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