Non-destructive inspection of concrete structures using ultrasonic sensor

Non-destructive inspection of concrete structures is often made using an ultrasonic sensor. With the conventional methods, however, a high reliable detection of anomalous parts (as cracks and cavities) and their depth measurement are difficult due to the disturbance by a reflected wave from the concrete surface and the overlapping of multi-reflected waves between the crack and surface. This paper proposes first to filter the sensor output with an adequate band pass filter to remove the affect from the disturbance and next to apply a pattern matching method based on a multi-reflected wave model in order to realize a reliable and accurate defect detection and depth measurement. Experiments show that the method detects horizontal and inclined cracks and measures the depth of the cracks accurately. Also, the paper suggests a method to detect vertical cracks.