The Swiss hammer, or rebound hammer, is a tool used to measure the strength of concrete. It is fairly simple to use and is considered a good way to gauge the durability and surface strength of concrete walls, floors and structural elements. ASTM C805 provides detailed instructions in the proper use of the Swiss hammer to measure concrete and check its strength for comparison to local building codes.
Test the Swiss hammer against the test anvil. Press the plunger end (with the plunger retracted) at a 90-degree angle against the test spot of the anvil until the internal hammer fires. Holding it against the anvil, check the gauge for the rebound number. If you move the hammer away from the anvil, the gauge will reset to zero, so be sure to check it before you move the hammer. Check this rebound number against the label on the test anvil to ensure your hammer is measuring accurately.
Smooth the test spots on your concrete surface with the abrasive stone. A rough surface texture can affect your results negatively. It does not need to be absolutely smooth, but any obvious tool marks or ridges should be ground down to the level of the main surface.
Using the same method as on the anvil (holding the hammer firmly at a 90-degree angle to the surface), test several spots on your concrete. Write these down on a piece of paper to keep track of your test numbers, always rounding to the nearest full number. Check with the manufacturer for the rebound numbers of your particular concrete mix to ensure your concrete is as strong as it should be.