Impact Products Digital Concrete Test Hammer CN652 - Manual (Page 21)

8 Appendix
8.1 Derivation of the PROCEQ Standard Conversion Curves
The conversion curves Fig. 8.1 and Fig. 8.2 for the concrete test hammer are
based on measurements taken on very many sample cubes. The rebound values
R of the sample cubes were measured using the concrete test hammer. The
compressive strength was then determined with the pressure testing machine. In
each test, at least 10 test hammer impacts were performed on one side of the
sample cube which was lightly clamped in the press.
Material of the sample cubes:
All cubes were made from concrete consisting of good quality fine gravel
(maximum particle size Ø 32 mm) and Portland cement.
Empirical values:
The conversion curve is practically independent of the:
- Cement content of the concrete
- Particle gradation
- Diameter of the largest particle in the fine gravel mixture, providing the diameter
of the maximum particle is < 32 mm
- Water/cement ratio
8.2 Standard Conversion Curves
Standard Conversion Curve for Concrete Test Hammer Model ND
Mean value has already been corrected in relation to the impact direction
Fig. 8.1 Model ND: Conversion curve based on the average compressive strength of a
cylinder and the rebound value R
: average compressive strength of a cylinder (probable value)
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