# Non-Destructive Testing in Civil Engineering
## 6 Interesting Case Studies in the Field of Non-Destructive Testing in Civil Engineering  
In article [14], it was shown that active thermography methods, such as step heating thermography, show a good correlation with the solar load system. Solar load thermography is an approach that has recently gained the attention of scientists. It is beneficial because it is particularly easy to set up and can measure objects on a large scale due to the fact that the sun is the main source of heat. This work also introduces the concept of using a pyranometer as a reference point for evaluation algorithms by providing a direct measurement of the intensity of solar radiation. In addition, a recently introduced method of estimating thermal efficiency is assessed using thermograms of the environment.  
Article [15] presents the portable X-ray sources that were developed in the last 10 years and which are based on a linear electron accelerator with a power of 950 keV/3.95 MeV in the X band (9.3 GHz). Moreover, it also describes the inspections of prestressed concrete bridges. A bridge with a T-shaped PC girder, 200-400 mm thick, and a bridge with a box-shaped PC girder, 200-800 mm thick were subjected to tests. X-ray images of the defects of the tendon ducts were observed. An attempt to quantify unfilled mortar was made. This is due to the fact that this is the major defect that causes corrosion. On the taken X-rayimages, gray values were obtained, which correspond to the X-ray attenuation coefficients of filled and unfilled mortars in tendon ducts. The gray ratio of the filled/unfilled tendon ducts was then compared in order to determine the degree of filling. For this purpose, data obtained from an actual T-shaped post-tensioned concrete bridge and model samples were used to validate the method.  
Precise evidence of the thermal conductivity of walls is essential for selecting the proper energy-saving measures in existing buildings. For reliable testing using the heat meter method (HFM), good thermal contact should be provided between the heat meter plate and the surface of the wall. The aim of the article [16] was to assess the effect of an imperfect thermal contact of the heat meter plates on the accuracy of the in-situ measurements of the U value of the facade after applying foil. The foil was applied in order to avoid damage to the surface of the wall, which is a normal procedure during the operational phase of a building. The results show that the deviations between the measured U-values and the values obtained using the HFM directly on the wall surface and when HFM was installed with a PVC film were significantly different from the theoretical values.  
Article [17] concerned the application of geophysical techniques in the urban environment of the city of Nicosia in Cyprus. The main goal of the research, being part of the Ebertheria Square redesign project, was to visualize subsurface properties in order to reduce the impact of threats on old buildings (and thus to preserve the cultural heritage of the site) and new infrastructure under construction. Since 2008, various phases of the project have used electrofusion tomography, radar, and also electromagnetic induction methods to provide an understanding of the geological stratigraphy of buried objects (archaeological and underground structures) and unexpected events (such as water infiltration). The results of geophysical research confirmed the effectiveness of the adopted methods, and added cognitive value with regard to the studied area. The new information gathered helped public administration technicians to plan direct and targeted interventions and to modify the original design in line with the discovery of archaeological finds.  
This research received no external funding.  
The authors declare no conflict of interest.