Monitoring chloride diffusion in BFS concrete using an Electrical Resistivity Tomography device

Abstract

Corrosion of steel bars in Reinforced Concrete (RC) due to the penetration of chlorides coming from seawater is one of the main pathologies leading to degradation of marine structures. Destructive Evaluation (DE) methods like coring from concrete in such marine environment are difficult and expensive for the survey of marine RC structures. Whereas, Non-Destructive Evaluation (NDE) methods based on the wave propagation (electric and electromagnetic) can reduce the number of cores necessary to evaluate the health of the studied structures. The aim of this work is to study the chloride ingress into saturated concrete by using the NDE methods and especially the Electrical Resistivity Tomography device. Accordingly, chlorides diffusion campaign with two different chloride concentration ([NaCl] = 35 and 90 g/L) was carried out on two slab of concrete contains slag addition. Apparent resistivities are then inverted in order to obtain a resistivity profile versus depth with two different software: Res1D and Ceris. Moreover, resistivity measurements were performed regularly on the slabs to obtain the resistivity profiles. On the other hand, a calibration method was realized to relate the resistivity to the chloride content for each type of concrete. The chloride profiles evaluated by NDT are then compared to those obtained by a destructive method (potentiometric titration) at three different exposure periods. The long-term goal is to use directly the NDE results in the model of chloride ingress into saturated concrete