Radar Investigation of masonry structures: from methodology to practice

The assessment and control of the built heritage rely on well-established methods and techniques. However, they still address challenging research fields, due to normative evolution and development of innovative systems and devices. Particularly, onsite non-destructive techniques are highly desirable in the case of historical architectures, because they provide with diagnostic information on wide investigation areas, without interfering with material integrity and structural stability. Nonetheless, they might set some methodological and operational issues, concerning selection criteria, application procedures, as well as elaboration and interpretation routines. Among several methodologies for masonry structures, radar investigation has recently emerged. It is a valuable tool to qualify construction materials and techniques, to identify morphology and stratigraphy of multi-layered components, to detect inner voids and cavities, to assess construction anomalies and discontinuities, as well as to characterize previous reinforcement works. The paper focuses on operation protocols for radar scanning, in order to point out the potentialities of application on masonry structures. Specifically, it discusses methods and procedures for data acquisition and elaboration in the Customhouse of Molfetta, Italy. For the case study, the radar investigation was correlated with survey of geometry, mapping of state ofconservation, complementary non-destructive and destructive tests. In detail, it concerned: Reinforced masonry walls for 3D tomographic elaboration, in order to qualify the wall inner cavities, as well as the reinforcement metallic bars and concrete mixtures. Unreinforced masonry walls for 2D elaboration, in order to detect construction anomalies, localize inner voids and cavities, and assess the connections between longitudinal and transversal walls. Reinforced masonry vaults for 2D elaboration in order to identify the reinforcement systems. The application highlighted that radar methods and tools require the preliminary assessment of typology and morphology of the expected anomaly. Such an assessment should rely on onsite visual survey and experimental investigation by complementary techniques, e.g. magnetometric tests in the case study. Furthermore, acquisition and elaboration of radar signals might entail very specific and limited samples, as calibration tests of the overall results. In the case study, those tests – i.e. video-endoscopy – only concerned a few areas, which resulted as critical/ representative from the extensive non-destructive diagnostic campaign. Such an approach is particularly helpful in historical buildings, in order to preserve the architectural and constructional integrity, to save time, resources and costs, and to make the diagnosis more accurate and reliable.