Stainless Steel Voltammetric Sensor to Monitor Variations in Oxygen and Humidity Availability in Reinforcement Concrete Structures

Ana Martínez-Ibernón,Josep Lliso-Ferrando,José M Gandía-Romero,Juan Soto

doi:10.3390/s21082851

Ana Martínez-Ibernón, Josep Lliso-Ferrando + Show 2 more

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https://doi.org/10.3390/s21082851

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Abstract

The present work presents the results obtained with a stainless steel (SS) voltammetric sensor to detect variations in humidity (H2O) and oxygen (O2) availability in concretes. First, studies in solution were run by preparing several solutions to represent the different conditions that can be found in concrete pores. Second, the sensor’s response was studied by varying O2 availability by argon or synthetic air bubbling. Then concrete conditions with different degrees of carbonation were simulated using solutions with a pH between 13 and 8.45. After characterization in solution, a study by means of concrete samples with several water/cement ratios (0.6, 0.5 and 0.4) was performed, in which sensors were embedded and studied under different O2 and H2O saturation conditions. The obtained results revealed that with the voltagram, it is possible to evaluate O2 availability variation from the slopes of the lines identified logarithmically in the voltagram for the obtained cathodic sweeping. All the results obtained with the sensor were correlated/validated by standard assays to characterize porosity in hardened concretes.

Highlights

The follow up and forecasting of reinforced concrete structures’ (RCS) service lives are some of the main recent objectives for reducing economic and environmental costs that are a direct result of inefficient maintenance actions, repairs that could have been minimized, and even demolishing buildings which could have been avoided if suitable preventive measures had been taken
This basic model distinguishes two periods: the first is the period of initiation, which includes the time from when aggressive agents penetrate the concrete matrix to the time when they reach rebars and bring about their depassivation; the second is the period of propagation, which covers the time from when rebars depassivate to when corrosion starts developing
In accordance with the obtained results, parameters m1 and m2, the slopes of the lines identified logarithmically in the voltagram for the cathodic sweeping obtained with the stainless steel (SS) sensor, are related to the different O2 reduction stages on the sensor’s surface

Summary

Introduction

The follow up and forecasting of reinforced concrete structures’ (RCS) service lives are some of the main recent objectives for reducing economic and environmental costs that are a direct result of inefficient maintenance actions, repairs that could have been minimized, and even demolishing buildings which could have been avoided if suitable preventive measures had been taken. The basic most extensive service life model related to this phenomenon was developed by Tutti [1,5]. This basic model distinguishes two periods: the first is the period of initiation, which includes the time from when aggressive agents penetrate the concrete matrix to the time when they reach rebars and bring about their depassivation; the second is the period of propagation, which covers the time from when rebars depassivate to when corrosion starts developing. The structure’s service life ends when an unacceptable degree of corrosion is reached

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