Large-area electrode design for vertical electrical impedance scanning of concrete bridge decks.

Abstract

Vertical electrical impedance (VEI) testing is a method that was developed specifically for quantifying the level of protection against chloride ingress in concrete bridge decks. A significant operational difficulty associated with VEI testing has been establishing the required rebar tap as a ground reference. As described in this work, the use of a large-area electrode (LAE) can potentially remove the need for a rebar tap and therefore significantly simplify and accelerate the VEI testing process. The specific objective of the research was to develop both theoretical and practical guidance for the design of an LAE for VEI testing. To investigate several variables that can affect the accuracy of VEI measurements obtained using an LAE connection, including various combinations of deck cover and water resistivity values, electrode separation distance, counter electrode (CE) effective area, and area ratio between the LAE and the CE, an analytical model (AM) and a finite-element model (FEM) were developed and validated with laboratory and field experiments. From the results of the AM and FEM simulations and the results of the laboratory and field experiments, LAE design considerations were developed for each of these variables that should allow proper implementation of a VEI measurement system using an LAE connection.