26. February 2024 © Copyright 2024, PROCEQ SA 23
Understanding the echoes:
Small echoes are in the blue scale, while strong echoes are in the areas from yellow to orange
to red (typical from concrete to air boundaries).
Figure 16: A-scan interpretation.
Ultrasound waves are reflected by materials with a different acoustic impedance than concrete.
The air (cracks, voids) completely reflects the signal, while the steel (rebars, PT ducts) reflects
part of it. This is why ultrasounds are perfectly fit for finding air defects and can be used in
some cases for finding rebars.
Figure 17: Acoustic impedance.
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