Development of a multi-ring resistivity cell and multi-electrode resistivity probe for investigation of cover concrete condition

Abstract

Direct Current (DC) electrical resistivity is a material property well known to be sensitive to various aspects of concrete condition related to corrosion risk. This paper describes the development of a multi-ring electrical resistivity cell for the evaluation of concrete. A multi-electrode surface resistivity probe for on-site applications is also presented. The multi-ring resistivity cell is capable of assessing the homogeneity of the investigated specimen, which is an important requirement for obtaining representative bulk resistivity results. The multi-electrode surface probe is used for depth investigation of cover concrete to identify moisture and chloride gradients by means of electrical resistivity tomography (ERT). The paper focuses on the development of these two resistivity devices, and the numerical modelisation, calibration, validation and cross-correlation thereof.The development of the resistivity cell will enable future work to establish master curves relating DC-resistivity to parameters indicative of concrete condition (particularly water content, chloride content and porosity). The final aim is then to estimate these state parameters for in situ concrete by means of the combination of electromagnetic non-destructive evaluation (NDE) techniques such as Electrical Resistivity Tomography (ERT), capacitive method and Ground Penetrating Radar (GPR).