New warning sensors to detect corrosion risk in reinforced concrete

Mahdi Khadra,Myriam Bouichou,Christian Crémona,Stéphanie Vildaer,Elisabeth Marie-Victoire,M.G Grantham,C Mircea

doi:10.1051/matecconf/201928906002

Mahdi Khadra, Myriam Bouichou + Show 5 more

Open Access

https://doi.org/10.1051/matecconf/201928906002

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Abstract

Corrosion is the most frequent but also the most deleterious deterioration mechanism affecting reinforced concrete. In addition to the economic impact of the repair works, for historical concrete structures, corrosion can generate irreversible losses of original material of great cultural value. If the usual non-destructive electrochemical methods have highlighted their efficiency in evaluating on-going corrosion activity, they also have pointed out their drawbacks for accurate extrapolation and prevention. To prevent the corrosion phenomenon, by detecting the penetration of aggressive agents, a new warning sensor system has been developed. The principle of the technique is to embed thin metallic sheets (called orphan blades) in the concrete cover, at different distances from the surface to the reinforcing bars. Then the corrosion of those very reactive orphan blades is followed during the propagation of the carbonation front and/or the penetration of chloride ions using stimulated infrared thermography. The corrosion of the sensors at different depths is indicative of the ingress speed of the front and can alert about the risk of corrosion of reinforcing bars in the concrete. The purpose of this study is to present this new technique and the first results obtained in the laboratory on corroded and non-corroded sensors.

Highlights

Nowadays, concrete has become the most used material in construction
The intensity of the hot spot and the elevation of the apparent temperature are higher for the sound sensor than that of the corroded sensor
When plotting the curve of these maximal apparent temperatures versus time, sound and corroded sensors can be clearly distinguished (Fig.10), so that this parameter can be considered as a quantitative indicator of corrosion

Summary

Introduction

Concrete structures interact with the external environment which leads to their degradation over time [1]. Atmospheric CO2, in the presence of moisture, reacts with the main constituents of concrete [2]. This reaction, called carbonation, reduces the pH of the interstitial solution, which is initially basic (12 to 13) to a value lower than 9, which initiates corrosion of the reinforcing bars [3]. In marine environments or in areas frequently exposed to de-icing salts, chloride ions can gradually penetrate concrete structures until they reach the reinforcement, and when the concentration of chloride ions exceeds a critical threshold, active corrosion can develop [3,5]. Corrosion causes major problems for conservation in reinforced concrete structures listed as historical monuments [4]

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