Electrochemical Behavior, Microstructural Analysis, and Morphological Observations in Reinforced Mortar Subjected to Chloride Ingress

Koleva, D.A.; Breugel, K. van; Wit, J.H.W. de; Westing, Epm van; Boshkov, N.; Fraaij, A.L.A.

doi:10.1149/1.2431318

Cited by 30 publications

(39 citation statements)

References 58 publications

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“…63-67͒. In addition, in order to consider previously reported investigation for similar systems as the hereby investigated ones, 45,46,54 the derived pseudocapacitance values were recalculated as pure capacitance ͓based on known relations of CPE and C, e.g., for a given frequency , the following relation between the imaginary part of the impedance of the CPE ͑Z CPE ͒ and the impedance of the fitted capacitance ͑Z C ͒ is valid: 68 A comparison of C red and C ct for the investigated cases in relation to OCP values is given in Fig. 5.…”

Section: Resultsmentioning

confidence: 99%

Corrosion Performance of Carbon Steel in Simulated Pore Solution in the Presence of Micelles

Koleva

Wit

et al. 2011

J. Electrochem. Soc.

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This study presents the results on the investigation of the corrosion behavior of carbon steel in model alkaline medium in the presence of very low concentration of polymeric nanoaggregates ͓0.0024 wt % polyethylene oxide ͑PEO͒ 113 -b-PS 70 micelles͔. The steel electrodes were investigated in chloride-free and chloride-containing cement extracts. The electrochemical measurements ͑electrochemical impedance spectroscopy and potentiodynamic polarization͒ indicate that the presence of micelles alters the composition of the surface layers ͑i.e., micelles were indeed absorbed to the steel surface͒ and influences the electrochemical behavior of the steel, i.e., the micelles lead to an initially increased corrosion resistance of the steel whereas no significant improvement was observed within longer immersion periods. Surface analysis, performed by environmental scanning electronic microscopy, energy-dispersive x-ray analysis, and x-ray photoelectron spectroscopy, supports and elucidates the corrosion performance. The product layers in the micelles-containing specimens are more homogenous and compact, presenting protective ␣-Fe 2 O 3 and/or Fe 3 O 4 , whereas the product layers in the micelles-free specimens exhibit mainly FeOOH, FeO, and FeCO 3 , which are prone to chloride attack. Therefore, the increased "barrier effects" along with the layers composition and altered surface morphology denote for the initially increased corrosion resistance of the steel in chloride-containing alkaline medium in the presence of micelles. A well-known fact is that corrosion of steel reinforcement can cause reinforced concrete deterioration and thus affect civil structures durability.1,2 Logically, corrosion-related issues result in a significant economic loss. For example, in the United States, the annual direct cost of bridge infrastructure corrosion was estimated to be $8.3 billion, and the indirect cost was reported to be many times higher. 3In normal conditions, the reinforcing steel embedded in cementbased materials ͑i.e., cement paste, mortar, and concrete͒ is in a passive state because of the high alkalinity ͑pH = 12.6-13.5͒ of the pore solution and the cement paste, respectively. 4,5 However, corrosion can be initiated due to carbonation or chloride contamination. 6 Carbonation can result in a pH drop ͑to about 8-9͒ 7,8 in the pore solution of the bulk cementitious matrix, leading to a general corrosion of the reinforcing steel. In the event of chloride penetration and chloride arrival at the steel/cement paste interface, localized corrosion is initiated; the local pH can drop to even below 6, resulting in fast corrosion propagation. This will cause accelerated damage of the reinforcing steel and possible rapid failure of reinforced concrete. 9To minimize the corrosion processes, various methods and techniques are used. Among them, the polymer-based organic corrosion inhibitors are widely applied because they can provide an easy handling, cost-effective corrosion prevention, delaying corrosion initiation.10-14 The organic inh...

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Section: Resultsmentioning

confidence: 99%

Corrosion Performance of Carbon Steel in Simulated Pore Solution in the Presence of Micelles

Koleva

Wit

et al. 2011

J. Electrochem. Soc.

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“…All specimens were cured in a fog room (20°C and 98% relative humidity) for 28 days and further lab conditioned (in tap water for control cases or 5% NaCl solution for corroding cases, respectively) until the end of the testing period of 86 days (the experimental set-up is as previously used and reported in [26,27]). There were three monitored replicates for each group and relevant test procedure.…”

Section: Methodsmentioning

confidence: 99%

“…Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) were employed, using a common three-electrode cell arrangement, the steel bar serving as the working electrode and MMO Ti mesh served as a counter electrode (the set-up is as generally used and reported [26,27]). All results from electrochemical measurements (performed in immersed condition) are reported with respect to a saturated calomel electrode (SCE); all measurements were performed after stabilization of open circuit potential (OCP); the PDP measurements were performed in the range of -0.2 to ?1.2 V versus OCP at a scan rate 0.5 mV/s after OCP stabilization; The EIS measurements were carried out in the frequency range of 50 kHz to 10 mHz by superimposing an ac voltage of 10 mV.…”

Section: Electrochemical Methodsmentioning

confidence: 99%

“…3a, comprises two time constants in series with the electrolyte resistance (the circuit is as previously used and reported for reinforced mortar [26,33]). The elements of the equivalent circuit present the following physical meanings: R el?b is the mortar resistance, including the contribution of the electrolyte resistance; the first time constant (R pn and Q pn ) is attributed to the properties of the bulk matrix in terms of connected pore network; the second time constant (Q ct and R ct ) is normally used to evaluate charge transfer process in combination with mass transport process.…”

Section: Electrochemical Impedance Spectroscopy (Eis)mentioning

confidence: 99%

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Corrosion performance of reinforced mortar in the presence of polymeric nano-aggregates: electrochemical behavior, surface analysis, and properties of the steel/cement paste interface

Koleva

Breugel

2012

J Mater Sci

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This study reports on the effect of admixed polyethylene oxide-b-polystyrene (PEO 113 -b-PS 70 ) micelles on corrosion behavior of reinforced mortar. The electrochemical measurement shows that the corrosion performance of the reinforcing steel was not significantly improved. However, surface analysis and microstructural investigation at the steel/cement paste interface reveal that the admixed micelles lead to a steel surface layer with enhanced barrier properties in terms of morphology and composition. Therefore, the presence of micelles further minimized and halted the corrosion process, despite the very aggressive, chloride-containing environment of 5% NaCl. The reasons and mechanisms behind the hereby observed corrosion behavior of reinforced mortar in the presence of micelles are related to the influence of these nano-aggregates on microstructural properties. These further results in altered water/ion transport and chloride-binding mechanisms in the bulk mortar matrix and thus steel product layer modifications towards enhanced corrosion resistance.

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“…[1][2][3][4][5][6][7] Whether they are represented in terms of total or free chloride concentrations, or chloride-to-hydroxide concentration ratio, Cl − /OH − , reported values of chloride thresholds for carbon steel reinforcement in concrete cover a wide range and have a large degree of variability. 9,10 The surface conditions of rebar, in particular, the presence of mill scale on the steel surface, is one of the potential causes of the reported uncertainty and variability in chloride thresholds.…”

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confidence: 99%

Numerical Investigation of the Role of Mill Scale Crevices on the Corrosion Initiation of Carbon Steel Reinforcement in Concrete

Karadakis

Azad

Ghods

et al. 2016

J. Electrochem. Soc.

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A numerical investigation was conducted to test the hypothesis that the composition of the pore solution in mill scale crevices on carbon steel rebar surfaces in concrete might be different from that of the bulk concrete pore solution, and this difference may create the necessary conditions for the premature breakdown of the passive film. The modeling was performed using a non-linear transient finite element algorithm, which involved the solution of coupled extended Nernst-Planck and Poisson's equations in a domain that represented typical mill scale crevices on carbon steel rebar. The numerical simulations showed that the chemistry of the pore solution, in particular pH and Cl − /OH − , within mill scale crevices provided more favorable conditions for depassivation than the bulk concrete pore solution. Local acidification and increase in Cl − /OH − within crevices were observed in all simulations, albeit to different degrees. Crevice geometry has been found to be the most important parameter affecting local acidification and the increase in Cl − /OH − . Simulations supported the hypothesis that the chemical composition of the pore solution within the crevices differs from that of the bulk solution through a process similar to the suggested mechanism of typical crevice corrosion. Within the alkaline environment of concrete, carbon steel reinforcement is protected against corrosion by a passive film, but chlorides from deicing chemicals or marine salts might cause the loss of this film when their concentrations exceed threshold values. [1][2][3][4][5][6][7] Whether they are represented in terms of total or free chloride concentrations, or chloride-to-hydroxide concentration ratio, Cl − /OH − , reported values of chloride thresholds for carbon steel reinforcement in concrete cover a wide range and have a large degree of variability. 9,10The surface conditions of rebar, in particular, the presence of mill scale on the steel surface, is one of the potential causes of the reported uncertainty and variability in chloride thresholds. 8,[11][12][13][14][15] It has been widely reported that higher chloride thresholds were observed for rebars with modified surfaces (i.e., without mill scale) through sandblasting, polishing or pickling than those in as-received conditions with mill scale. 12,13,15,16 In some cases, it was observed that corrosion did not initiate in highly-polished rebar even after the specimens were exposed to chloride concentrations in excess of that is typically found in sea water.11 In addition, modifying the rebar surface leads to reduced variability and fluctuations in electrochemical measurements, which can be explained by the fact that modified surfaces are nearly uniform, whereas as-received surfaces are locally much more diverse and complex due to the presence of mill scale. 17 These results suggest that the variability associated with the reported chloride thresholds may be partially attributed to the variability in mill scale properties resulting from the variability in manufacturing.In a recent...

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Electrochemical Behavior, Microstructural Analysis, and Morphological Observations in Reinforced Mortar Subjected to Chloride Ingress

Cited by 30 publications

References 58 publications

Corrosion Performance of Carbon Steel in Simulated Pore Solution in the Presence of Micelles

Corrosion Performance of Carbon Steel in Simulated Pore Solution in the Presence of Micelles

Corrosion performance of reinforced mortar in the presence of polymeric nano-aggregates: electrochemical behavior, surface analysis, and properties of the steel/cement paste interface

Numerical Investigation of the Role of Mill Scale Crevices on the Corrosion Initiation of Carbon Steel Reinforcement in Concrete

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