Humboldt H-2987 Concrete Rebound Hammer - Manual (Page 3)

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Taking a Measurement
Selecting a Surface for Testing
Select a concrete surface that is:
• Smooth, dry, and fixed in place
• At least 4 inches (or 102 mm) thick
• Mature— at least 14 days old
• Free of any decay or scaling
If necessary grind a section of rough concrete smooth before taking your
readings. A grind stone in a plastic case is provided with the hammer for this
purpose.
Surfaces to Avoid
Avoid testing concrete that is:
• Frozen
• Honeycombed or excessively porous
• Known to have rebar 2 cm or less below the surface
• Carbonated on the surface
If you must test a mature concrete surface that is damp from rain or flowing
water, or if you must test new concrete, keep in mind that you will probably get
As long as you hold the Rebound Hammer firmly against the concrete, the re-
bound number will remain on the scale. Record your reading. When you pull the
hammer away and allow the piston to re-extend, the scale will return to zero.
The Rebound Hammer is now ready for another test. If desired, once you get a
reading, you may press the button on the handle to lock the piston in place. This
makes your test results easier to read, as it will also lock the indicator. Do not
touch the button until you get a reading. To release the piston again for the
next test, press against a hard surface. When you are finished using the Rebound
Hammer, lock the piston inside the Rebound Hammer for storage, as described
above.
Figure 3: Push the piston in as far as it will go