Nitto CTS-02V4, User Manual, Page: 16 / 37

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3.4 Measured Value
Three index values, STR Value (Strength), INDX Value (Index), STAT Value (Status), can
be calculated based on a waveforms of impact force in CTS-02V4. The calculated values can
be seen in the display.
＜
STR Value
＞
・
STR value is an index value of strength of the concrete.
・
Both of the mechanical impedance index value and the spring constant index value can be
used to estimate the compressive strength of the concrete.
・
By means of set-up of parameters, you can select for which value should be used.
*Difference between Mechanical Impedance Index Value and Spring Constant Index Value
Mechanical Impedance Index Value
・
The strength calibration chart should be used to estimate the compressive strength of the
concrete based from the measured STR value.
・
Even if the variance of STR values was small, the variance of estimated compressive
strength of the concrete may be significantly large by the calibration chart.
Example: When the STR value is less than 1.37, change of 0.01 units in STR value results
in a change of an average of 0.67 N/mm
2
.
When the STR value is 1.37 and more, change of 0.01 units in STR value
results in a change of an average 2.09 N/mm
2
.
Spring Constant Index Value
・
Spring constant index value is an index value of spring constant per unit area of the
concrete surface and of an estimated strength of concrete.
・
The value corresponds to the cube of mechanical impedance index value (in case of high
compressive concrete, the value corresponds to the fourth power of mechanical impedance
index value).
・
The measured STR value can be read directly as the estimated compressive strength
(N/mm
2
).
・
Each of measured values will be varied widely if compared to mechanical impedance index
value.
＜
INDX Value
＞
・
INDX value is an index value of surface deterioration.
・
The value shows the rate between the initial velocity when the hammer contacts the
concrete and the velocity of rebound.
・
If the measured body is ideally elastic, the value becomes 1; if the surface is deteriorated,
the INDX value will increase.
・
When the INDX value is over than 1.5 at any time, the strength may be underestimated.
・
In such case, it is necessary to polish the concrete surface.