The waveform of impact force in below is obtained by tapping concrete with CTS. This wave form is measured by an accelerometer that installed on the hammer unit. Measured wave form can be divided into two part. The first half of the waveform shows the process that the hammer is pushing on the concrete surface. This process includes plastic deformation first, then elastic deformation of concrete surface. The second half of the waveform is the process that the hammer is rebounding from the concrete surface. In other words, the second half of the waveform is only affected by the characteristics of elasticity of concrete, and compressive strength of the concrete that is not affected by deterioration of concrete surface can be estimated. Besides, degree of deterioration of concrete surface can be determined from the ratio of the first half and the second half of the waveform.
The first half of the waveform called Active process that includes plastic deformation of concrete surface.
The second half of the waveform called Reactive process that shows the effect of spring coefficient of concrete itself.
ZR=Compressive strength value(STR)(Unit:N/mm2)
ZA/ZR= Index value of deterioration(INDX)
Number of local peaks= Index value of delamination(STAT)
Measurement method & Measurement display
[Decide measurement point and confirm the measurement value]
After selecting the Site number, CTS becomes lookup mode. Measurement data can be confirmed at this mode. Move the measurement point by selecting cursor keys. In case there is a previous data at the point, measured value (average value) will be displayed. If there is no previous data, CTS does not show any value. To start your measurement, please confirm there is no previous data, then press “D” button. To delete previous data, press “D” button at the point you want to delete.
[Compressive strength estimation]
When you select “Point mode” at the parameter setting, measurement data that is beyond 20% of the average of 20 times measurement will be automatically removed from the calculation. After 20 times measurement, the data that is within 20% range of average will be taken into the calculation. However, the data that is removed from the calculation is still recorded on CTS.