Cakir, Mehmet2026-09-012026-09-0120262079-9292http://dx.doi.org/10.3390/electronics15122742https://hdl.handle.net/20.500.12403/8449Electromagnetic shielding has become a practical concern in buildings and structures exposed to persistent interference. This paper reports experimental measurements of the frequency-dependent shielding properties of a square-resonator-integrated double-concrete structure, using a free-space S-parameter setup built around WR229 waveguide adaptors and horn antennas. Three variables were tested: concrete thickness D, relative permittivity epsilon r, and relative magnetic permeability mu r. Both epsilon r and mu r were characterized experimentally from carbon-fibre- and copper-slag-modified concrete rather than taken from standard tables. The novelty of the study lies in combining experimentally characterized concrete electromagnetic properties, an embedded square-resonator geometry, and explainability-driven machine learning analysis within a single experimental framework for cement-based EMI shielding design. A total of 96 parameter combinations were evaluated using calibrated S11 and reference-corrected S21 responses across 3.3-4.9 GHz. Thickness and electromagnetic material properties interacted-neither governed shielding performance on its own. The strongest transmission attenuation occurred at D = 5, epsilon r = 7, and mu r = 1.2, where minimum S21 reached approximately -62.98 dB at 3.6392 GHz. S11 varied considerably less than S21 across the tested combinations, suggesting transmission suppression is the dominant mechanism rather than reflection enhancement. A machine learning analysis confirmed that nonlinear ensemble models outperformed the linear baseline and identified thickness as the most influential predictor of minimum S21.eninfo:eu-repo/semantics/openAccessElectromagnetic ShieldingConcrete-Based StructureSquare ResonatorS-Parameter AnalysisMachine LearningExplainable Artificial IntelligenceArticle151210.3390/electronics151227422-s2.0-105043083763N/AWOS:001802209000001Q2