EXPERIMENT of Rebound Hammer Test

Purpose

The rebound hammer test is one of the non-destructive tests used to check the compressive strength of concrete. Rebound hammer test (Schmidt Hammer) is used to provide a convenient and rapid indication of the compressive strength of concrete. It consists of a spring controlled mass that slides on a plunger within a tubular housing.

Standard Designation

ASTM C805

Scope

• This test method covers the determination of a rebound number of hardened concrete using a spring-driven steel hammer.
• The values stated in inch-pound units are to be regarded as the standard.
• This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Apparatus

Rebound Hammer

Procedure

• Should be tested against the test anvil.
• Apply light pressure on the plunger and allow it to extend to the read position for the test.
• Apply a gradual increase in pressure until the hammer impacts.
• Take the average of about 15 readings.

Interpretation of Results

The rebound reading on the indicator scale has been calibrated by the manufacturer of their bound hammer for horizontal impact.

Average Rebound Number	Quality of concrete
>40	Very good hard layer
30-40	Good layer
20-30	Fair
<20	Poor concrete
0	Delaminated

Conclusion

1.    The rebound value can be measured discretionary, whereas the number of crushed specimens is limited.

2.    The combination of both methods is the best and most reliable procedure to determine the compressive strength of concrete structures.

3.    The method does not damage the structure like the classical method, where cores must be taken for the evaluation of the compressive strength.

4.    It is a fast, inexpensive and easy to perform method using light and portable test equipment.