Characterization of Damage Using Ultrasonic Testing on Different Types of Concrete

Concrete is a common material used for structures like buildings and bridges. To assess the structures periodically, nondestructive testing needs to be practical in its cost and application. In this paper, 36 cylindrical specimens are casted with nine different concrete mixtures. These mixtures are classified as follows: varying water-cement ratio (WC) in percentages of 40, 50, and 60 mixed with well-graded aggregates as ordinary concrete (ORC); varying WC of 40, 50, and 60 mixed with short steel fibers as fiber-reinforced concrete (FRC); and WC50 mixed with varying aggregate sizes classified as small (5 to 10 mm aggregates), medium (10 to 15 mm aggregates), and large (13 to 20 mm aggregates). Averaged time domain and frequency domain waveforms are recorded and analyzed to obtain linear and nonlinear ultrasonic parameters. Linear ultrasonic parameters are ultrasonic pulse velocity (UPV) and peak-to-peak amplitude (PPA), while the nonlinear ultrasonic parameter is the second harmonic ratio (SHR). The parameters are measured in two states-undamaged and damaged-under ultimate compressive stress. The UPV and PPA measurements proved to be less sensitive in damage measurements for all nine different types of concrete due to their minimal percentage difference from the undamaged to damaged state. However, this technique may be used to quickly determine the consistency of concrete and its macroscopic state of damage. In nonlinear ultrasonic test parameters, it is found that SHR percentage difference from the undamaged to damaged state has the following behaviors: (1) it is inversely proportional to WC for ORC; (2) it is directly proportional to WC for FRC; and (3) no trend is found for concrete with varying aggregate size at WC50, showing that the strength of concrete is dependent on the combination of maximum aggregate size and WC.