Abstract
The concrete electrical resistivity is a prominent parameter in structural health monitoring, since, along with corrosion potential, it provides relevant qualitative diagnosis of the reinforcement corrosion. This study proposes a simple expression to reliable determine resistivity from the concrete electrical resistance (RE) provided by the corrosion sensor of the Integrated Network of Sensors for Smart Corrosion Monitoring (INESSCOM) we have developed. The novelty here is that distinct from common resistivity sensors, the cell constants obtained by the proposed expression are intended to be valid for any sensor implementation scenario. This was ensured by studying most significant geometrical features of the sensor in a wide set of calibration solutions. This embedded-sensor approach is intended to be applicable for RE measurements obtained both using potential step voltammetry (PSV, used in the INESSCOM sensor for corrosion rate measurement) and alternating current methods. In this regard, we present a simple protocol to reliably determine RE, and therefore resistivity, from PSV measurements. It consists in adding a very short potentiostatic pulse to the original technique. In this way, we are able to easy monitor resistivity along with corrosion rate through a single sensor, an advantage which is not usual in structural health monitoring.
Highlights
The service life of reinforced concrete structures depends largely on the extent of reinforcement corrosion, known to begin when certain aggressive agents such as CO2 and chloride ions come into contact with and destroy the passive film formed on the steel rebars [1]
Recommendations for correlating the probable corrosion risk and concrete resistivity are presented in the literature [8], where the corrosion risk of reinforcement is divided into four levels according to the magnitude of resistivity (ρ) as exemplified at Table 1 together with corrosion risk criteria based on the corrosion rate value, expressed in terms of current density, according to references [9,10]
The sensor measurement is based on the Potential Step Voltammetry (PSV), whereas common methods for resistivity measurement are based on alternating current methods
Summary
The service life of reinforced concrete structures depends largely on the extent of reinforcement corrosion, known to begin when certain aggressive agents such as CO2 and chloride ions come into contact with and destroy the passive film formed on the steel rebars [1]. The importance of concrete cover quality, for it is the sole physical-chemical barrier between the steel and the exposure environment. Corrosion rate depends on ionic transport in the concrete between the anode and cathode of the electrolytic cells forming in the reinforcement [2]. Concrete physical-chemical properties determine the corrosion rate. Concrete cover resistivity is an important parameter to take into account to study reinforcement durability, as it provides information about the concrete quality and its saturation degree, directly related with the corrosion process [4]. Several authors have revealed an inversely proportional relationship between concrete resistivity and reinforcement corrosion rate [5,6]. Resistivity, along with corrosion potential, is a prominent parameter in most inspection and monitoring systems [7]. Recommendations for correlating the probable corrosion risk and concrete resistivity are presented in the literature [8], where the corrosion risk of reinforcement is divided into four levels according to the magnitude of resistivity (ρ) as exemplified at Table 1 together with corrosion risk criteria based on the corrosion rate value, expressed in terms of current density (iCORR ), according to references [9,10]
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