Non-destructive monitoring methods and continuous monitoring systems based on them are crucial elements of modern systems for the management and maintenance of assets which include reinforced concrete structures. The purpose of our study was to summarise the data on the most common sensors and systems for the non-destructive monitoring of reinforced concrete structures developed over the past 20 years. We considered systems based on electrochemical (potentiometry, methods related to polarisation) and physical (electromagnetic and ultrasonic waves, piezoelectric effect, thermography) examination methods. Special focus is devoted to the existing sensors and the results obtained using these sensors, as well as the advantages and disadvantages of their setups or other equipment used. The review considers earlier approaches and available commercial products, as well as relatively new sensors which are currently being tested.
The marine environment is highly corrosive for mild and low alloy steels. This study aimed to enhance the corrosion resistance of the AH36 steel in a saline medium by coating it with a copper particles reinforced polyaniline (PANI) layer. PANI and Cu particles were grown on the steel surface by electrodepositing methods. Firstly, PANI was electropolymerized in the presence of oxalic acid, followed by the electrodeposition of Cu particles at different deposition times. The coating showed a well-distribution of Cu particles in the polymer matrix and excellent adhesion. Furthermore, the Cu particles and PANI-coated steels exhibited corrosion resistance significantly in the saline medium compared to the bare substrate and pristine PANI-coated samples. The improved corrosion protection of a Cu@PANI coating on the AH36 steel could contribute to forming a physical barrier by filling Cu particles on the PANI pores.
This paper presents the results of a study on the corrosion of steel reinforcement in concrete pore solutions contaminated with chloride ions. With increasing chloride concentration, the open-circuit potential and the anodic polarization curve shift towards more negative potential values, the passive potential region of the anodic polarization curve decreases. The corrosion rate of reinforcement was evaluated according to the linear polarisation resistance technique. Accordingly, the corrosion rate of steel reinforcement is 4.53 µA/cm2 in the solution containing 1 M Cl-. In this study, galvanic electrochemical sensors with low carbon steel anodes and copper cathodes were developed. In an environment with no or low Cl- concentration, where the reinforcement is passivated, the corrosion current density of the sensor does not exceed 10.0 µA/cm2. The corrosion current of the sensor increases sharply under cathodic control with increasing chloride content. Thus, the developed sensor has a high sensitivity to chloride corrosion and is capable of detecting pitting corrosion caused by chlorides at an early stage.
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