# Ultrasonic Pulse-Echo Signals for Quantitative Assessment of Reinforced Concrete Anomalies
## 5 Conclusions  
This study aims to quantitatively evaluate void defects in concrete deck slabs using the ultrasonic pulse-echo technique.  
* Advanced signal processing methods are used to accurately evaluate the location of the void defects in concrete decks, whereas the imaging of commercialized ultrasonic devices usually gives qualitative information about defects.
* A concrete deck slab specimen with artificial void defects is used for validation. A commercial ultrasonic pulse-echo device, based on the ultrasonic shear-wave test method using dry-point-contact transmitting and receiving transducers, and extended SAFT were employed to map the internal void defect of the validation concrete deck slab specimens.
* The recorded data from the ultrasonic pulse-echo device was analyzed by using the proposed methods to accurately evaluate the void defect locations in the concrete deck slab specimen. The new method consists of benchmark envelope estimation and the denoise of the echo signal, which identifies the weak stochastic and non-stationary echo signal from void defects.
* The results demonstrated that the proposed method accurately located the void defects in the concrete deck specimen. In contrast, the commercial ultrasonic pulse-echo device's map for the void defects of the concrete deck can only give qualitative results.
* The cost of application of the new method and procedure is low, as the A-scan is always available for UPE testing, and all the related algorithms have been well developed.
* The direction to extend the current study is to apply and evaluate the proposed method to other kinds of subsurface anomalies of concrete, such as irregular crack, rebar/corrosion, etc.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Method** & **Experimental Specim** & **UPE Device** & **New Method** \\ \hline Distance from surface (mm) & 83 & 70–75 & 82 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of the void location.  
Figure 8: A-scan of RC specimen with void and the extracted envelope from A-scans without void.  
**Author Contributions:** Conceptualization, W.Z.; Methodology, W.Z. and G.C.; Software, H.N.; Validation, W.Z., G.C. and F.X.; Formal analysis, W.Z., G.C. and F.X.; Investigation, W.Z.; Resources, W.Z.; Data curation, W.Z., G.C. and H.N.; Writing--original draft, G.C.; Writing--review & editing, W.Z. and H.N.; Supervision, W.Z.; Project administration, W.Z.; Funding acquisition, W.Z. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by West Virginia Department of Transportation grant number [RP328].  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author (due to restrictions from the funding agency).  
**Acknowledgments:** [PERSON] and [PERSON] would like to express their appreciation for the financial support provided by the West Virginia Department of Transportation (WVDOT) through the research project entitled \"Corrosion Research to Maintain and Sustain Infrastructure in West Virginia\". The findings, conclusions, or recommendations expressed in this study are those of the authors and do not necessarily reflect the viewpoints of the WVDOT. The authors would like to thank [PERSON], [PERSON], [PERSON], and [PERSON] for their support while conducting this research project's experiments.  
**Conflicts of Interest:** The authors declare no conflict of interest.