Practical Interpretation of Electrical Resistivity in Cracked Reinforced Concrete using the Four-Point Wenner Method

Electrical resistivity (ER) is widely used for durability assessment of reinforced concrete, especially for evaluating corrosion-related deterioration. However, its interpretation becomes increasingly challenging with corrosion-induced cracking, as the governing mechanism evolve with damage progression. This study investigates the influence of cracks on ER measurements using a combined numerical–experimental approach, based on the decomposition of ER response into material-driven and geometry-driven effects. In the early stages of corrosion, ER variations are governed by material-driven effects associated with microstructural and interfacial deterioration, which modify the effective conductivity of the concrete. In contrast, at advanced stages, geometry-driven effects caused by surface-breaking cracks dominate, primarily through distorsion of the current-field. Finite element simulations and laboratory experiments confirm this transition and identify threshold crack dimensions below which geometry-driven effects remain limited (within ~10% deviation), corresponding to surface-breaking cracks narrower than 0.6 mm and internal cracks narrower than 0.4 mm. These findings establish a mechanism-based framework that delineates the transition between material-dominant and geometry-dominant regimes, providing a quantitative basis for interpreting ER measurements in cracked concrete. • ER response in cracked concrete is governed by geometry-driven and material-driven effects. • FE simulations quantify current-field distortion induced by crack geometry. • Threshold crack widths define when geometry-driven effects on ER remain limited. • A framework distinguishes when ER indicates durability versus crack severity.