Ultrasonic non-destructive testing techniques for diagnosing concrete damage

In this research ultrasonic testing techniques of linear and nonlinear categories were applied to diagnose both initial and peak level damage in concrete. For this purpose standard cubic concrete specimens with different w/c were produced. The specimens were subjected to compression loading in several steps and ultrasonic evaluation of the test specimens at each loading step both in damaged and undamaged states was conducted. The induced concrete damages were diagnosed by analysing recorded waveform data in order to measure attenuation of the ultrasonic waveforms, harmonic generation and pulse velocity. From the test results analysis and comparison, ultrasonic attenuation and harmonic generation (non-linear ultrasonic) measurements were found more sensitive to early age cracking in concrete than pulse velocity (linear ultrasonic) measurements. The non-linear ultrasound technique has higher potential to be employed for in-situ diagnosing of damage in concrete structures.