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Luca Bertolini - One of the best experts on this subject based on the ideXlab platform.
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Effect of electroosmotic flow of aqueous suspension of nanosilica on the properties of Carbonated Concrete
Materials and Corrosion-werkstoffe Und Korrosion, 2017Co-Authors: Elena Redaelli, Federica Lollini, F. Torabian Isfahani, Luca BertoliniAbstract:The paper investigates the possibility to use electroosmosis to transport nanosilica (NS) particles inside Carbonated Concrete, in order to exert a filler effect and enhance its durability performance. This method aims to extending possible beneficial effects of NS to existing reinforced Concrete structures, where the presence of a Carbonated layer of Concrete is very likely. Injection tests were performed with electrochemical cells on Carbonated Concrete discs with water/cement (w/c) ratios of 0.50, 0.55 and 0.65, using a NS aqueous suspension at the anode. The results indicated that a flow did occur through the Concrete disc and it was directed from the anode towards the cathode. A linear relationship between flux and applied voltage gradient was obtained, which is typical of electroosmotic phenomena. The bulk properties of Concrete, such as density, water absorption and sorptivity, were not affected by the injection tests, whilst electrical resistivity increased indicating a mild ‘sealing’ effect on the surface. Also microstructural analyses highlighted the local presence of NS that decreased the local porosity close to the surface.
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Cathodic protection with localised galvanic anodes in slender Carbonated Concrete elements
Materials and Structures, 2014Co-Authors: Elena Redaelli, Federica Lollini, Luca BertoliniAbstract:A combined experimental and numerical investigation was carried out with the aim of determining whether few localised galvanic anodes per unit length could protect the reinforcement of slender Carbonated Concrete elements, exposed to atmospheric conditions, which could not be repaired with traditional methods. Initially, the cathodic behaviour of steel under galvanostatic polarisation was determined on small-size specimens obtained from a real element. A correlation of potential versus applied current was obtained. The current distribution in slender elements was then determined through finite elements simulations, considering various scenarios of carbonation and humidity. Results showed that, in spite of the high electrical resistivity of Carbonated Concrete, anodes with spacing of 0.45 m are enough to protect corroding reinforcement in most exposure conditions, even in thin parts of element. Estimated anode durations were of the order of several years or even decades; however, it was shown that also reinforcement in dry (Carbonated or alkaline) Concrete, which does not need to be protected, contributes to anode consumption. Although other aspects play a role on the performance of a cathodic protection system (such as the effectiveness of anode-encasing material and of electrical connection to reinforcement), the results obtained are supportive of a repair strategy based on the use of localised galvanic anodes and can be generalised to slender elements exposed to atmospheric conditions suffering carbonation induced corrosion.
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Electrochemical Realkalization as a Conservation Technique for Reinforced Concrete
International Journal of Architectural Heritage, 2012Co-Authors: Luca Bertolini, Sonia Lupica Spagnolo, Elena RedaelliAbstract:Electrochemical realkalization (ER) is a repair technique aimed at restraining corrosion of steel in Carbonated Concrete. ER is based on the application of a current to restore Concrete alkalinity—the favorable environment for the protection of steel from corrosion. The treatment lasts from few days to weeks; then, when the entire Concrete cover is realkalized, the external anode that supplied the current is removed, leaving the surface unchanged. Moreover, ER does not require the replacement of Carbonated Concrete if it is not damaged, so it can be advantageous compared with the traditional repair, which usually requires the removal of large amounts of mechanically sound (although Carbonated) Concrete. Although ER treatment was introduced in the 1980s, debate continues on some aspects connected with its application. This study presents the preliminary results of a long-term experimental research aimed at investigating this technique. The results obtained allowed determining ER effects in terms both of re...
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Electrochemical repair techniques in Carbonated Concrete. Part II: cathodic protection
Journal of Applied Electrochemistry, 2011Co-Authors: Elena Redaelli, Luca BertoliniAbstract:The role of several factors such as Concrete composition, exposure condition and pre-corrosion of steel reinforcement in Concrete on the effectiveness of the electrochemical realkalisation ( ER ) technique was discussed in Part I of this article (Bertolini and Redaelli in J Appl Electrochem, doi: 10.1007/s10800-011-0301-4 , 2011 ). Here the same factors will be considered in the case of cathodic protection ( CP ). CP differs from ER since it is a permanent technique with much lower applied current density. It was originally introduced to protect steel from corrosion in chloride-contaminated Concrete; however, it can be advantageous even in Carbonated Concrete, in particular compared to conventional repair. CP tests were carried out on reinforced specimens made with six different types of Concrete, subjected to accelerated carbonation. CP was applied with a current density of 10 mA m^−2 of steel preceded by a start-up current density of 100 mA m^−2 for 3 weeks. Reference specimens in the same conditions were also considered.
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Electrochemical repair techniques in Carbonated Concrete. Part I: electrochemical realkalisation
Journal of Applied Electrochemistry, 2011Co-Authors: Elena Redaelli, Luca BertoliniAbstract:Corrosion induced by Concrete carbonation can be controlled through the application of electrochemical techniques such as cathodic protection (CP) or electrochemical realkalisation (ER). These methods are generally considered effective in the repair of structures; however, few data are available on the effects of different parameters such as the Concrete composition or the exposure conditions. For the temporary technique of ER, moreover, scarce information exists on the durability of the treatment. An experimental research was carried out, aimed at investigating some aspects connected with the application of these techniques in reinforced Carbonated Concrete. Six different types of Concrete mixes were considered. The tests were performed both in a wet and a dry environment. The effect of the pre-corrosion of the reinforcement in Concrete was also considered. This article presents results obtained with the technique of ER and discusses the role of the different factors considered. The technique of CP will be discussed in Part II.
Carla Conti - One of the best experts on this subject based on the ideXlab platform.
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Corrosion resistance of galvanized steel reinforcements in Carbonated Concrete: effect of wet–dry cycles in tap water and in chloride solution on the passivating layer
Cement and Concrete Research, 2014Co-Authors: G. Roventi, Tiziano Bellezze, G. Giuliani, Carla ContiAbstract:The effect of wet–dry cycles in tap water and in 3.5% NaCl solution on the passivating products of galvanized steel after Concrete carbonation was investigated. The results show that carbonation destroys the passivating layer of calcium hydroxyzincate with the formation of the amorphous products ZnCO3 and Zn5(CO3)2(OH)6, which are also protective. The exposure to wet–dry cycles in tap water after Concrete carbonation does not significantly increase the corrosion rate of the galvanized steel with respect to the values measured in non-Carbonated Concrete. On the contrary, the exposure to chloride solution after Concrete carbonation leads to a marked decrease in the chloride threshold for galvanized steel corrosion with respect to that found in non-Carbonated Concrete.
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corrosion resistance of galvanized steel reinforcements in Carbonated Concrete effect of wet dry cycles in tap water and in chloride solution on the passivating layer
Cement and Concrete Research, 2014Co-Authors: G. Roventi, Tiziano Bellezze, G. Giuliani, Carla ContiAbstract:The effect of wet–dry cycles in tap water and in 3.5% NaCl solution on the passivating products of galvanized steel after Concrete carbonation was investigated. The results show that carbonation destroys the passivating layer of calcium hydroxyzincate with the formation of the amorphous products ZnCO3 and Zn5(CO3)2(OH)6, which are also protective. The exposure to wet–dry cycles in tap water after Concrete carbonation does not significantly increase the corrosion rate of the galvanized steel with respect to the values measured in non-Carbonated Concrete. On the contrary, the exposure to chloride solution after Concrete carbonation leads to a marked decrease in the chloride threshold for galvanized steel corrosion with respect to that found in non-Carbonated Concrete.
Arnaud Castel - One of the best experts on this subject based on the ideXlab platform.
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Influence of pre-existing oxides layer and interface condition with Carbonated Concrete on active reinforcing steel corrosion
Materials and Corrosion Werkstoffe und Korrosion, 2015Co-Authors: Arnaud Castel, Abdelkader NasserAbstract:This work focuses on carbonation-induced corrosion in Concrete. This paper presents specific experiments which were developed in order to assess the influence of both pre-existing oxides layer at the surface of the steel bars and steel-Concrete interface condition on active corrosion. Two types of active corrosion are studied: Microcell corrosion and galvanic corrosion. Results show that pre-existing oxide layer contributes to reduce both galvanic and microcell corrosion. Steel-Concrete interface defect leads to a strong increase in galvanic corrosion but does not affect significantly microcell corrosion in Carbonated Concrete. The quantity of pre-existing oxides is highly scattered and these scatters can be superior to the mass of new oxides formed during relatively short-term corrosion tests in natural condition which makes mass loss analysis very difficult.
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Microcell versus galvanic corrosion currents in Carbonated Concrete
Magazine of Concrete Research, 2014Co-Authors: Arnaud Castel, Abdelkader NasserAbstract:This paper presents specific experiments developed to assess galvanic corrosion currents in Carbonated Concrete. The work investigated the influence of both the steel–Concrete interface condition and the cathodic to anodic surface ratio. Galvanic corrosion currents were compared with microcell corrosion currents. In the quasi-saturated condition, galvanic corrosion currents were systematically found to be much higher than microcell corrosion currents. Moreover, the presence of defects at the interface between the anodic steel surface and Concrete leads to a significant increase in the macrocell driving potential and, therefore, in the galvanic corrosion current. Furthermore, the galvanic current density strongly increased with increasing cathodic to anodic surface ratio. The coupling of a high cathodic to anodic surface ratio and the presence of steel–Concrete interface defects at the anodic surface leads to huge galvanic corrosion current densities.
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Influence of pre‐existing oxides layer and interface condition with Carbonated Concrete on active reinforcing steel corrosion
Materials and Corrosion-werkstoffe Und Korrosion, 2013Co-Authors: Arnaud Castel, Abdelkader NasserAbstract:This work focuses on carbonation-induced corrosion in Concrete. This paper presents specific experiments which were developed in order to assess the influence of both pre-existing oxides layer at the surface of the steel bars and steel–Concrete interface condition on active corrosion. Two types of active corrosion are studied: Microcell corrosion and galvanic corrosion. Results show that pre-existing oxide layer contributes to reduce both galvanic and microcell corrosion. Steel–Concrete interface defect leads to a strong increase in galvanic corrosion but does not affect significantly microcell corrosion in Carbonated Concrete. The quantity of pre-existing oxides is highly scattered and these scatters can be superior to the mass of new oxides formed during relatively short-term corrosion tests in natural condition which makes mass loss analysis very difficult.
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influence of steel Concrete interface condition on galvanic corrosion currents in Carbonated Concrete
Corrosion Science, 2010Co-Authors: Abdelkader Nasser, S. Laurens, Antoine Clement, Arnaud CastelAbstract:Abstract This paper presents specific experiments which were developed in order to assess galvanic currents in macrocell corrosion specimens involving active steel in Carbonated Concrete and passive steel in sound Concrete. The influence of the steel–Concrete interface condition on the galvanic current was also experimentally investigated. To focus on macrocell corrosion rate assessment, the initiation time of the corrosion process (Concrete carbonation) was accelerated. FEM simulations were carried out in order to enhance the physical comprehension of these corrosion experiments. It was found that, in realistic condition, the electrical coupling of active and passive steel areas leads to high galvanic currents and consequently high corrosion levels according to RILEM recommendation. Moreover, steel–Concrete interfacial defaults significantly increase the macrocell driving potential and, therefore, the galvanic corrosion current.
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Influence of steel–Concrete interface condition on galvanic corrosion currents in Carbonated Concrete
Corrosion Science, 2010Co-Authors: Abdelkader Nasser, Antoine Clement, Stéphane Laurens, Arnaud CastelAbstract:Abstract This paper presents specific experiments which were developed in order to assess galvanic currents in macrocell corrosion specimens involving active steel in Carbonated Concrete and passive steel in sound Concrete. The influence of the steel–Concrete interface condition on the galvanic current was also experimentally investigated. To focus on macrocell corrosion rate assessment, the initiation time of the corrosion process (Concrete carbonation) was accelerated. FEM simulations were carried out in order to enhance the physical comprehension of these corrosion experiments. It was found that, in realistic condition, the electrical coupling of active and passive steel areas leads to high galvanic currents and consequently high corrosion levels according to RILEM recommendation. Moreover, steel–Concrete interfacial defaults significantly increase the macrocell driving potential and, therefore, the galvanic corrosion current.
Bernhard Elsener - One of the best experts on this subject based on the ideXlab platform.
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Corrosion rate of carbon steel in Carbonated Concrete – A critical review
Cement and Concrete Research, 2018Co-Authors: Matteo Stefanoni, Ueli Angst, Bernhard ElsenerAbstract:Reinforced Concrete with lower environmental footprint (lower CO2emission) can be obtained by reducing the clinker content in the cements. As the carbonation of Concrete is faster, corrosion of steel in Carbonated Concrete during the propagation phase is becoming important both for science and practice. The present literature review summarizes the state of the art, reporting corrosion rate data for a broad range of cement types, w/b ratios and environmental conditions. Correlations between corrosion rate and the main influencing parameters are elaborated and discussed. It confirms that the corrosion rate of steel in Carbonated Concrete is not under ohmic control. More important are the degree of pore saturation and the effective steel area in contact with water filled pores. It also emerges that the new blended cements have to be systematically studied with respect to the corrosion behavior of steel in Carbonated Concrete in order to make reliable service life prediction.
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corrosion rate of carbon steel in Carbonated Concrete a critical review
Cement and Concrete Research, 2018Co-Authors: Matteo Stefanoni, Ueli Angst, Bernhard ElsenerAbstract:Abstract Reinforced Concrete with lower environmental footprint (lower CO2 emission) can be obtained by reducing the clinker content in the cements. As the carbonation of Concrete is faster, corrosion of steel in Carbonated Concrete during the propagation phase is becoming important both for science and practice. The present literature review summarizes the state of the art, reporting corrosion rate data for a broad range of cement types, w/b ratios and environmental conditions. Correlations between corrosion rate and the main influencing parameters are elaborated and discussed. It confirms that the corrosion rate of steel in Carbonated Concrete is not under ohmic control. More important are the degree of pore saturation and the effective steel area in contact with water filled pores. It also emerges that the new blended cements have to be systematically studied with respect to the corrosion behavior of steel in Carbonated Concrete in order to make reliable service life prediction.
W. Dridi - One of the best experts on this subject based on the ideXlab platform.
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Rebar corrosion in Carbonated Concrete exposed to variable humidity conditions. Interpretation of Tuutti’s curve
Corrosion Science, 2009Co-Authors: Patrick Dangla, W. DridiAbstract:This paper deals with the modelling of the rebar corrosion kinetics in unsaturated Concrete cover. The Concrete is assumed Carbonated resulting in an active corrosion of steel. The corrosion kinetics is coupled with the ionic transport processes. Free corrosion in different Concretes is studied in terms of ambient relative humidity. The numerical results obtained by the finite volume method are discussed and compared with a reported experiment performed on a Carbonated Concrete.
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rebar corrosion in Carbonated Concrete exposed to variable humidity conditions interpretation of tuutti s curve
Corrosion Science, 2009Co-Authors: Patrick Dangla, W. DridiAbstract:This paper deals with the modelling of the rebar corrosion kinetics in unsaturated Concrete cover. The Concrete is assumed Carbonated resulting in an active corrosion of steel. The corrosion kinetics is coupled with the ionic transport processes. Free corrosion in different Concretes is studied in terms of ambient relative humidity. The numerical results obtained by the finite volume method are discussed and compared with a reported experiment performed on a Carbonated Concrete.