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.

Multi-sensor data collection and fusion using autoencoders in condition evaluation of concrete bridge decks

“…VEI is an NDE technique used to quantitatively estimate the protection offered to steel reinforcement against chloride ion ingress [10][11][12][13][14][15][16][17]. A VEI measurement in a scanning configuration with a large-area electrode is shown schematically in Fig.…”

Instrumentation for multi-channel vertical electrical impedance scanning of concrete bridge decks

“…Ideally, inspection techniques used to assess bridge decks would be both rapid and nondestructive to avoid the need for costly, disruptive, stationary traffic control and testing-related deck repairs. One recently developed inspection technique for concrete bridge decks involves measurement of vertical electrical impedance (VEI) [7][8][9][10][11][12]. Previous research has shown that VEI correlates well with other evaluation techniques such as chloride concentration and half-cell potential [8], which can be useful especially in preventative maintenance programs in cold regions and coastal regions in which concrete bridge decks are regularly exposed to salt.…”

“…While early versions of VEI measurement instruments were single-channel units that required the operator to drill a hole through the concrete to establish an electrical connection to the top mat of reinforcing bar, or rebar, the recent development of a multi-channel unit equipped with a large-area electrode (LAE) has enabled VEI measurements that are both rapid and completely nondestructive [7,11]. This paper documents a new impedance analyzer that has further increased the scanning speed.…”

“…The geometry, placement, and electrical connection of probes needed to perform VEI measurements are important [7,11,17]. To couple the probes electrically to the bridge deck, a coupling fluid, usually water, is placed on the surface [7][8][9][10][11]14].…”

“…The geometry, placement, and electrical connection of probes needed to perform VEI measurements are important [7,11,17]. To couple the probes electrically to the bridge deck, a coupling fluid, usually water, is placed on the surface [7][8][9][10][11]14]. The high-side port of an impedance analyzer, which provides the voltage source and facilitates the current measurement, is connected to a probe on the surface of the bridge deck.…”