# Non-Destructive Testing in Civil Engineering
## 3 Complementary Applications of the Non-Destructive Testing Methods  
Article [6] presents resonance frequency tests of bent concrete samples. These frequencies were determined simultaneously using the sonic resonance method and the impulse excitation technique, with the two methods then being compared. The samples differ in used material and shape. The mean values and corresponding values of standard deviations of the resonance frequencies were compared. The performed tests showed the equivalence of both methods of measuring the resonance frequency. The obtained difference between the values measured using the sonic resonance method and the impulse excitation technique were not significant. The relationship between the resonant frequencies, which is presented graphically, is linear with a slope of 0.9993. Fibrous reinforcement in high-performance cement materials is widely applied in many areas of the construction industry. One of the most frequently studied features of steel fiber reinforced concrete is the slower development of cracks, which in turn results in the better durability of such concrete. Additional benefits are related to structural properties, as fibers can significantly increase the ductility and tensile strength of concrete. In some applications, it is even possible to completely replace conventional reinforcement with fiber reinforcement, leading to significant logistical and environmental benefits. However, it can have disadvantages, as the fibers can induce anisotropic behavior of the concrete if they are not properly oriented. For the safe use of steel fiber reinforced concrete, non-destructive testing (NDT) methods should be used in order to assess the orientation of the fibers in the hardened concrete. For this purpose, article [7] uses complementary methods of ultrasound, electrical impedance and X-ray computed tomography. The article also demonstrates the capabilities of each of these techniques separately when measuring fiber orientation. Based on these results, conclusions were drawn regarding the most promising areas for future research and development. Article [8] examines the use of a heat flux meter and quantitative infrared thermography to assess the difference between the predicted and real thermal conductivity of house facades under steady-state conditions in the Mediterranean basin. First, the suitability of NDT techniques was tested experimentally, and then a single-family house was verified in a real environment. The outcomes of this study show that both techniques quantified the difference between the design and real U-value of a house facade. The quantitative infrared thermography method was faster than the heat flux meter method, although the flux meter method has higher accuracy. The presented results will help when choosing the most appropriate test method. Analysis of the Results of Non-Destructive Testing, Including the Use of Sophisticated Mathematical Algorithms and Artificial Intelligence  
Until now, the analysis of cores obtained from a structure by drilling is the main option to obtain knowledge about the depth of damage due to water penetrating the floors of buildings. The time-consuming and costly procedure is an additional burden for building insurers, who mention water damage caused by leaking pipelines as the most common claim against insurers. The radar method, due to its high sensitivity to water, can be an important and non-destructive support for this problem. Therefore, the article [9] describes a modular sample, which was developed to obtain the appropriate thickness of screed and insulation material. The resulting dataset was then used to examine the corresponding characteristics of a signal in order to classify three situations: dry insulation, damaged insulation, and damaged screed. It was highlighted that the analysis of the statistical distributions of the scans allows for an accurate identification of damage on floors.