Relationship of Apparent Electrical Resistivity Measured by Four-Probe Method with Water Content Distribution in Concrete

摘要

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 measured results must be identified as an apparent value including the effect of water content gradient in concrete. In order to consider the engineering property of apparent electrical resistivity, this study evaluated the water content gra-dient dependency of the measured results by 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 with water content gradient in depth direction. Moreover, it was pointed out that the apparent electrical resistivity of con-crete with water content gradient was correlated with the electrical resistivity at a depth about equal to the probe spac-ing, 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 absence of the effect of the water content gradient in concrete.