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Rebound hammer

The rebound (Schmidt) hammer is one of the oldest and best known methods of comparing the concrete in various parts of a structure and indirectly assessing concrete strength. It is actually a measure of surface hardness. The rebound hammer should be considered as a means of determining variations of strength within a structure rather than an accurate means of assessing strength. The surface under test should be clean and smooth. Dirt or other loose material on the surface can be removed using a grinding stone prior to the test. Rough surfaces cannot be tested as they do not give reliable results.

If it is to be used as a means of assessing strength the correlation between rebound hammer reading and strength needs to be determined for the actual concrete under investigation. A procedure for doing this is given in BS EN 12504-2. The values obtained by using the hammer may be influenced by the particular operator, so care must be taken when considering results from different operators.

 

Image courtesy of ELE International
 
Acknowledgement: The Concrete Society
 

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