The strength values shown in this diagram are directly based on compressive
strength testing in a laboratory, using concrete 14 to 56 days old. The tests use
concrete cylinders, 6 inches wide and 12 inches high (15cm x 20cm), or concrete
cubes six inches high.
According to ASTM C-805-08, you should discard any readings that differ
from the average value rebound number by more than six units. Then, take an
average for the remaining readings. If more than two readings differ by more
than six units from the average value, throw out all of your readings and perform
the test over again. Take ten new readings with your Rebound Hammer in a
different section of the concrete but in the same test area.
Note that some countries have set their own national standards for calculating
test results. Therefore, follow the standards of the country where you are using
your Rebound Hammer.
Maintenance
We recommend that you calibrate your Rebound Hammer regularly using
the Humboldt Calibration Anvil, H-2972, ordered separately. For a Rebound
Hammer, you should start verifying the readings after approximately 2,000
uses (or completed tests). You should also verify the readings if you have
reason to suspect that your Rebound Hammer is giving you false data.
Verifying Performance of Rebound Hammer
When tested against the Anvil, the rebound number must be a value of 80 ±2.
As the Rebound Hammer approaches 2,000 uses, it may start to read outside of
the range of 80 ±2 on the test Anvil. At this point an inspection by our service
center is suggested.
Safety:
• When using this device wear safety glasses
• Do not fire the Rebound Hammer against any body part
Specifications:
Humboldt Concrete Rebound Hammer: H-2987H
Weight: 2lbs (0.9 kilograms)
Size: 10.5" (267mm) with plunger retracted
Shipping weight: Six pounds (2.7 kilograms)
Carrying case: 15½ inches x 11½ inches x 2½ inches
