Corrosion Diagnostics Performed on Cores Drilled from Concrete Structures, Using the Laboratory Simulation of Temperature and Relative Humidity Impact (original) (raw)
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Procedia Engineering, 2017
This paper presents a method of conducting diagnostic tests for corrosion rate in concrete structures, which has been patented by the authors. The method consists in drilling cores with embedded pieces of steel reinforcement from cylindrical structures, and arranging a three-electrode system on such cores to measure polarization with a potentiostat. The three-electrode arrangement uses a piece of steel reinforcement in concrete core as the working electrode, a stainless steel sheet placed on one of the core bases – as the counter electrode, and an electrode of constant and known potential as the reference electrode. Determining the maximum and minimum corrosion rate of a steel bar in the concrete core is the most important element of the developed method, in which changeable temperature and humidity conditions are modelled around the tested structure. Extremely adverse and highly favourable values of temperature and humidity are determined for individual tested structures. Those parameters can be monitored in a climatic chamber while measuring polarization resistance of the reinforcement. This paper also includes examples of practical application of this method in diagnostic tests conducted by the authors on responsible reinforced concrete structures
Construction and Building Materials, 2021
Steel corrosion is the main cause of deterioration of reinforced concrete (RC) structures. We provide an up-to-date review on corrosion mechanisms and recent advances in electrical methods for corrosion monitoring. When assessing corrosion mechanism, the inherent heterogeneity of RC structures and the significant effect of environmental factors remain major issues in data interpretations. The steel surface condition and local inhomogeneities at the steel-concrete interface appear to have an important effect on corrosion initiation. Considering uniform corrosion in atmospherically exposed reinforced concrete, the two main influencing factors of the corrosion process are the water content and the pore structure at the steel-concrete interface. However, irrespective of the depassivation mechanism, i.e. carbonation or chloride-induced corrosion, nonuniform corrosion is expected to be the main process for RC structures due to local variations in environmental exposure or the presence of interconnected rebars with different properties. Future studies may then be focused on their effect on macrocell corrosion to gain further insights in the corrosion mechanisms of RC structures. Concerning corrosion monitoring using electrical methods, the half-cell potential technique with potential mapping is accurate for locating areas with a high corrosion risk. Recent developments in the measurement of concrete resistivity have shown that the use of electrical resistivity tomography allows to consider appropriately the inherent heterogeneity of concrete and provides more insights on transport phenomena (e.g. water and salts ingress) in the material. Nevertheless, during the corrosion propagation stage, the polarization resistance remains the most important parameter to be determined as it provides quantitative information of the corrosion rate. If conventional three-electrode configuration methods can supply an accurate determination in the case of uniform corrosion, they often fail in the case of macrocell corrosion in field experiments. Recent advances have shown that a four-electrode configuration without any connection to the rebar can rather be used for the non-destructive testing and evaluation of corrosion. If studies are still required to quantify the corrosion rate, this method appears sensitive to localized corrosion and thus more suitable to field investigations. Finally, the coupling of numerical simulations with complementary electrical and other non-destructive testing methods is essential for consolidating the results to provide a better diagnosis of the service life of RC structures.
Monitoring corrosion in concrete by means of Electrical Resistance Probes
2012
Carbonation and chlorides are the main reasons for deterioration of concrete, caused by corrosion of rebars. Controlling the corrosion in concrete by means of a system able to monitor corrosion’s parameters, such as potential, pH or corrosion rate, represents a powerful way to prevent concrete deterioration and to reduce restoration’s cost of the damaged structure. The aim of this work was to test Electrical Resistance Probes (ERP), usually applied to corrosion measurements in pipelines or tanks, by embedding them in concrete to monitor and estimate rebars corrosion rate. Five ERP probes were embedded into two cylindrical concrete samples, together with four steel rebars. The samples were exposed to chloride penetration and carbonation. Free corrosion potential and corrosion rate values of the rebars were monitored, by means of corrosion resistance polarization measurements (1), in comparison with the loss of metal provided by the ERP system. At first, samples were submitted to acce...
Corrosion assessment and control techniques for reinforced concrete structures: a review
Journal of Building Pathology and Rehabilitation, 2019
Steel corrosion is the main source of damage and early failure of reinforcement concrete structures that in turns create huge economical loss and creating environmental problems. In the past, several corrosion assessment techniques such as potential measurement, gravimetric weight loss measurement, electrical resistivity measurement, sensors and electrochemical methods for instance potentiodynamic polarization, linear polarization resistance, galvanostatic pulse, and electrochemical impedance have been developed to detect corrosion condition of steel in concrete. Though the potential measurement, resistivity measurement and sensors can only provide the qualitative information about the steel corrosion. The weight loss measurement is an efficient technique for corrosion rate measurement of steel, but it is destructive and requires long exposure times. The electrochemical techniques are non-destructive in nature and are used to determine corrosion rate of steel in laboratory as well as field studies. However each of these methods possesses certain advantages and limitations, therefore a combination of these techniques is recommended to use to obtain the corrosion condition of steel. As far as corrosion control techniques for steel reinforced concrete are concerned, several methods such as cathodic protection, electrochemical chloride extraction, surface treatments of the steel, surface treatment of concrete, utilization of mineral admixtures and chemical corrosion inhibitors have been developed in the past. Each of these methods offers some advantages and disadvantages. Thus, more researches are required to develop such methods of corrosion protection of steel that are economical, durable, environmentfriendly and do not cause any adverse effect on the structural performance of concrete and steel.
Mapping corrosion of steel in reinforced concrete structures
This report presents the results from a research project financed by the Swedish National Road Administration. In this project an instrument composed of computerised galvanostatic supplier and data acquisition system has been developed at SP for electrochemical measurement. With the help of this instrument, different measurement conditions and parameters could be evaluated and many electrochemical measurement data could be collected for later analysis. A numerical model based on a 2-D FEM (2-Dimensional Finite Element Method) has been established for modelling the corrosion measurement. With the help of this model, the measurement parameters could be optimised and the effectively confined current could be evaluated. Based on the results of numerical modelling and the studies on the small and big reinforced concrete slabs, a rapid method for measuring corrosion rate has been developed. The method involves a short time galvanostatic pulse measurement followed with the numerical calculation for correcting the preset polarisation current from the measured data, so as to produce "true" resistance values related to the confined area. Owing to its rapidity (in a few seconds per measurement), this method provides a useful tool for mapping corrosion rate of reinforcement steel in concrete structures. The results from a comparative measurement on both small and big reinforced concrete slabs show that the corrosion rate measured by the new rapid method is quite comparable with that measured by Gecor, which uses the modulated confinement technique. The results from the field measurements on two old concrete bridges also show that the corrosion extent measured by the new rapid method is in good agreement with the visual observations.
Corrosion Science, 2005
In situ measurements of steel corrosion rate in large reinforced concrete structures face difficulties of different types. The paper discusses some of the problems connected with the determination of the true value of the polarisation resistance from (i) the time constant value associated with the corrosion process, and (ii) the use of a guard ring for confining the electrical signal to a definite reinforcement area. In (i), results corroborate the assumption of a time constant value independent of the area affected by the electrical signal, albeit with some exceptions. In (ii), it is shown the great importance of achieving a critical ratio between the current intensities that flow from the guard ring and counter-electrode.
2000
1359-5997/00 © RILEM tivity for loss of protection or the severity of corrosion. Most non-destructive tests are electrochemical methods: potential mapping, polarisation resistance testing, concrete electrical resistance measurement. Embedding probes allows to monitor various factors involved in corrosion and environmental inf luences. To address these items, RILEM has set up TC 154-EMC on Electrochemical Techniques for measuring Corrosion of Steel in Concrete. Through its existence, TC 154 has set out to prepare RILEM Technical Recommendations on: – Half cell potential measurements – Test methods for on-site corrosion rate measurement of concrete reinforcement by means of the polarisation resistance method – Test methods for on site measurement of resistivity of concrete – Embedded probes for corrosion. The present document intends to describe methods to assess concrete resistivity on site for various purposes related to corrosion and protection of steel reinforcement.
Embeddable reference electrodes for corrosion monitoring of reinforced concrete structures
Materials and Corrosion, 2009
Mixed-metal oxide (MMO), graphite and laboratory-made Ag/AgCl electrodes were electrochemically characterized to be used as reference electrodes embedded in concrete structures. Electrodes were studied in both, aqueous solutions of pH ranging from 7 to 13.5 and embedded into cement mortars; and the electrochemical studies were carried out in the absence and presence of chloride ions. Potential evolution, polarisation behaviour, galvanostatic pulse response and impedance characteristics of the electrodes were carried out in aqueous solutions. Besides, the electrochemical stability of the electrodes embedded in mortar was studied for an exposure period of two years. It was found that the MMO pseudo-reference electrode is pH-sensitive, the graphite pseudo-reference electrode is oxygen sensitive and the Ag/AgCl pseudoreference electrode is chloride sensitive. Then, regarding the corrosion monitoring of steel rebars, care should be taken to avoid misleading interpretations of the corrosion potential measurements. However, any of them can be used to measure the corrosion rate of the rebars by means of traditional electrochemical techniques.