Relationship of apparent electrical resistivity measured by four-probe method with water content distribution in concrete

The electrical resistivity of concrete is an important value for designing electrochemical anti-corrosive methods or a durability indicator of reinforced concrete structures. It is well known that the four-probe method (the Wenner method) can be useful one for non-destructive evaluation of electrical resistivity. however, it has been pointed out that the measu i-cd results must be identified as an apparent value including the effect ot water content gradient in concrete. In order to consider the engineering property of apparent electrical resistivity, this study evaluated the water content gradient dep cndcncv of the measured results b experimental approach and numerical analysis with FEM. As a result, this study explained the mechanism about the probe spacing dependency of apparent electrical resistivity of concrete ith water content gradient in depth direction. Moreover, it was pointed out that the apparent electrical resistivity of concrete ith water content gradient as correlated with the electrical resistivity at a depth about equal to the probe spacing, and measuring apparent electrical resistivity does not necessarily mean that the four probe method can evaluate the electrical resistivity of the immediate surface of concrete in dry conditions. In addition to this, it was recommended to compare the apparent electrical resistivities measured by several distance of the probe spacing in order to clarify the presence or abs ence of the etThct ot the water content gradient in concrete.