Embedded system for ultrasonic imaging of under-water concrete structures

Abstract

Many of the modern concrete structures such as sea-links and bridges are built in water. They require structural health monitoring (SHM) and audit to ascertain the quality and estimation of remaining useful life. To meet these requirements, a single-channel ultrasonic imaging system has been designed and developed to detect defects, porosities and rebar locations inside the Concrete/ Reinforced Cement Concrete (RCC) structures. This real-time and reconfigurable embedded system whas evaluated by carrying out under-water imaging of Concrete and RCC test blocks. Conventionally, Ultrasonic Pulse Velocity (UPV) method is being utilized over three decades in Transmit-Receive (T-R) mode to estimate the density and strength of the concrete structure under test. UPV method requires a skill to interpret the data provided by the UPV instrument. The novelty of the single-channel system discussed in this paper is that it is capable of inspecting Concrete/ RCC structures both in Pulse Echo (PE) as well as in T-R mode. An application software has been developed using C# in a visual environment for image acquisition and the control of Data Acquisition (DAQ) hardware has been interfaced to the computer via USB. The imaging system performs data acquisition and coherent averaging of the RF bipolar data to achieve Signal-to-Noise Ratio (SNR) higher than 20 dB. The performance of the system was evaluated by acquiring B-Scan images of the water submerged concrete test blocks having Side Drilled Hole (SDH) and RCC blocks with one as well as two steel rebars, using 54 kHz water immersion transducer in PE mode. The acquired B-Scan images have revealed the internal details of the sample test blocks, resembling the defects generated in the test blocks. High voltage tone burst bipolar pulser with maximum output of (± 350 V) has been specifically designed for this system to inspect highly attenuative porous and non-homogeneous Concrete/ RCC materials for the detection of SDH and reinforced steel bars in the concrete test blocks, using B-Scan imaging technique.