# Ultrasonic Pulse-Echo Signals for Quantitative Assessment of Reinforced Concrete Anomalies
)1 College of Engineering and Computer Sciences, Marshall University, Huntington, WV 25755, USA; [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (H.N. )1 College of Engineering and Computer Sciences, Marshall University, Huntington, WV 25755, USA; [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (H.N. )1 College of Engineering and Computer Sciences, Marshall University, Huntington, WV 25755, USA; [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (H.N. )1 College of Engineering and Computer Sciences, Marshall University, Huntington, WV 25755, USA; [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (H.N. )1 College of Engineering and Computer Sciences, Marshall University, Huntington, WV 25755, USA; [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (H.N. )1 College of Engineering and Computer Sciences, Marshall University, Huntington, WV 25755, USA; [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (H.N. )1 College of Engineering and Computer Sciences, Marshall University, Huntington, WV 25755, USA; [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (H.N. )1 College of Engineering and Computer Sciences, Marshall University, Huntington, WV 25755, USA; [EMAIL_ADDRESS] (W.Z. )1 College of Engineering and Computer Sciences, Marshall University, Huntington, WV 25755, USA; [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (H.N. )1 College of Engineering and Computer Sciences, Marshall University, Huntington, WV 25755, USA; zatar@marshall. through the material to the receiver. The receiver converts the mechanical energy back to electrical energy, amplified as an echo, and recorded as an A-scan [11; 12; 13]. Figure 1 shows the schematic of a typical ultrasound reflection principle in a UPE device, with a transmitting and a receiving transducer. Equation (1) allows for accurate calculation of the depth of the reflecting interface of the defect, \(Z\). \(C_{s}\) refers to the material's shear-wave speed, \(\Delta t\) is the travel time measured, and X is the horizontal spacing between the transmitter and the defect location (Equation (1)) [7; 11]. To understand the physical properties of material better, it is essential to consider its density (\(\varphi\)), Poisson's ratio (\(\mu\)), modulus of elasticity (\(E\)), and shear modulus (\(G\)). By analyzing these factors, we can gain valuable insights into the behavior and characteristics of the material (Equation (2)). \[Z=\sqrt{\left(C_{s}\frac{\Delta t}{2}\right)^{2}-X^{2}} \tag{1}\]  
\[C_{s}=\sqrt{\frac{E}{\varphi}\frac{1}{2(1+\mu)}}=\sqrt{\frac{G}{\varphi}} \tag{2}\]  
If applied effectively, UPE devices can be employed in the construction industry to inspect and evaluate the quality of reinforced concrete structures. Commercially available UPE devices, such as MIRA, EyeCon, and Pundit, utilize the tomography technique to generate images of the interior concrete, which can help identify potential imperfections [14; 15; 16]. In this study, the dry-point-contact transducer array unit was used to enhance the accuracy of the inspection further. The UPE device used in this study is a low-frequency ultrasonic shear-wave tomography device with a surface longitudinal spacing of 30 mm, making it an excellent tool for detecting even the smallest defects in concrete structures. Conventional software of UPE (v7.3.5) devices has limited the application to image concrete structures because of the assumption of a single-layer homogeneous, isotropic medium for concrete. A concrete bridge deck is a complex structure with multiple layers of different materials, each with varying shear-wave velocities. Due to this variation, the software used for inspection may provide inaccurate information about the multi-layered bridge deck, including depth, thickness, and internal defects. Furthermore, the software's signal processing may not accurately present reflected waves at the surface and defects. The real heterogeneous materials may result in the generation of non-linear features in wave propagation. The irregular surface texture may cause sensor contact variation and create a stochastic signal.