Ultrasonic Testing of Lightweight Fine Aggregate Concrete in Time and Frequency Domains

Abstract

Non-destructive techniques (NDT) have been used to assess the condition of existing concrete structures, to predict future performance, and to monitor the conditions of repaired systems and so on. One of the widely known NDT is the ultrasonic pulse velocity (USPV) method, which determines the travel time of the ultrasonic pulse through the tested material. Most studies were focused on the results expressed in time domain. However, the signal of ultrasonic pulse in time domain can be transformed into frequency domain, through Fast Fourier Transform (FFT). This paper shows a comparison of changes in the pulse velocity and frequency domain signals of concrete for various load histories using lightweight fine aggregates. The results demonstrate that the signals in frequency domain of ultrasonic pulse of lightweight fine aggregate concrete does not show any significant difference comparing with those of normal concrete. The reduction trend of peak frequency was found to be more influenced by the stress levels rather than the ultrasonic pulse velocity.