## 1 Introduction
### Non-Destructive Methods for Testing Concrete Structures
Table 1 presents a classification of the methods, comparing them across several criteria: 1. Evaluation of rebars: this category assesses the capability to locate reinforcing bars and identify their class and diameter within typical concrete cover thickness ranges (20-50 mm). 2. Evaluation of corrosion: this category evaluates the ability to detect corrosion by examining delamination and diameter reduction, focusing on standard concrete cover thickness ranges. 3. Evaluation of \(h\) (concrete cover thickness): this criterion measures the method's effectiveness in estimating the thickness of the concrete cover within typical ranges. 4. Evaluation of carbonation: this category involves analyzing various changes in the physical properties of concrete that indicate ongoing carbonation processes. 5. Evaluation of concrete: this category serves to assess concrete integrity. The criterion includes the detection of delamination, large air voids, macro heterogeneities, and cracks within the concrete. 6. Area testing (spatial measurement capability): this category highlights the method's ability to conduct measurements simultaneously at many points (creating a measurement matrix). 7. Commercial viability: this criterion evaluates the method's usability for commercial applications, including cost measurements and any technical limitations that may affect its utility. The analysis in Table 1 indicates that the range of NDT methods applicable to examining reinforced meshes is limited. Radiography is highly effective, designed for area testing, and the obtained results are relatively easy to interpret. However, the technique has several significant limitations. Typically, both the source and detector must be positioned on opposite sides of the object, which can complicate the testing process or make it impossible in many instances. Additionally, this method causes health risks to personnel and is relatively costly, rendering it impractical for most applications [4; 5; 14]. Ground-penetrating radar (GPR) enables the detection of rebar from several centimeters to over ten meters, significantly exceeding the maximum detection range of the eddy current (EC) and magnetic flux leakage (MFL) methods (which are limited mainly to less than 200 mm). GPR is particularly effective (and primarily used) for rapid area assessments. However, the interpretation of the results can be challenging. The accuracy of the method is limited. Additionally, this method is unsuitable (in most cases) for typical concrete cover thicknesses (which are too low for radar), limiting its practical application. Furthermore, GPR equipment costs are high [10; 11; 12; 13]. In many cases, ultrasonic testing (UT) can be a viable alternative to eddy current (EC) and magnetic flux leakage (MFL) methods. UT is versatile, capable of locating reinforcing bars, evaluating their parameters, and sometimes detecting corrosion. Additionally, it can be used for area testing, such as with the total focusing method. Specific variants of UT can effectively assess concrete cover thicknesses greater than 0.5 m. However, UT methods were