Electrical Resistivity Measurements for Quality Control During Concrete Construction

For the production of new concrete structures in severe environments, requirements to chloride diffusivity are increasingly being used as a performance-based specification for concrete durability. As a basis for the concrete quality control during concrete construction, however, the testing of chloride diffusivity is both time-consuming and elaborate. Therefore, the relationship between chloride diffusivity and electrical resistivity of the given concrete based on the Nernst-Einstein equation should first be established. Then the chloride diffusivity can indirectly be controlled by routine-based measurements of the electrical resistivity during concrete construction. There are several test methods for measuring the electrical resistivity of concrete. Also, there are several factors that may affect such measurements. To provide more information about some of those factors that may affect the results and establish some simple procedures for a routine-based quality control of the electrical resistivity during concrete construction, an experimental program was carried out. The test program was mainly based on the four-electrode (Wenner) testing of the electrical resistivity and included different probe spacing and different geometry of the test specimens. For comparison, some two-electrode measurements were also carried out. To describe the effect of the various factors that may affect the resistivity, the test results are mostly presented as relative resistivities obtained by the two different test methods. The results show that, for given testing conditions, the electrical resistivity obtained by the Wenner method is different from that obtained by the two-electrode method. It was concluded, however, that for a given type of concrete specimen with given moisture and temperature conditions, the Wenner method appears to be a suitable and reliable test method for performance-based quality control of electrical resistivity, and hence concrete durability, during concrete construction. [PUBLICATION ABSTRACT]