Revisiting the ASTM C876 standard for corrosion of reinforcing steel: On the correlation between corrosion potential and polarization resistance during the curing of different cement mortars
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... According to Eq. (8), increasing R p means a lower corrosion current and better corrosion resistance. When the steel bar is considered to be passive, the limited corrosion current was 0.1 μA=cm 2 (Koga et al. 2018). If the Stern-Geary equation is used with the polarization equation, the polarization resistance of the steel in its passive state can be calculated (about 10 kΩ). ...
... However, the polarization resistance was similar at the later high current densities for all specimens with and without PAC. Previous studies (Koga et al. 2018;Nguyen and Castel 2020;Zhou et al. 2018) showed that under chloride environments, the steel bar was considered to be passive at various conditions after the polarization-depolarization cycles at incrementally imposed current. However, the polarization resistances of all samples were higher than 10 kΩ at each imposed current, which indicated that no pitting corrosion was actively taking place in any specimen. ...
The effect of polyaluminum chloride (PAC) on the durability, microstructure, and corrosion sensitivity of slag-cement pastes was investigated in this research. Various experimental tests were performed to assess the mechanical properties (compressive strength test), durability (rapid chloride migration test, water permeability test, capillary water absorption test, chloride binding test, accelerated carbonation test), microstructure (scanning electron microscopy, X-ray diffraction, mercury intrusion porosimetry), and corrosion sensitivity (accelerated corrosion sensitivity, initial chloride concentration). Experimental results showed that adding 1.5% PAC increased compressive strength by 77.0%, 53.8%, and 19.4% at 3, 7, and 28 days. Resistance to chloride migration, water permeation, capillary water absorption, and carbonation was improved. These results were consistent with the microstructural analysis, which showed that adding PAC facilitated the formation of Friedel's salt and development of pore structure, which was the key factor for the improved durability of the slag-cement paste. Adding 1.5% PAC had a limited influence on the corrosion sensitivity despite introducing the additional chloride ions into the system. These results promote the further practical application of PAC.
... Fig. 3 presents OCP and R p values of 00Cr10MoV and 20MnSiV steels in alkaline solutions at the passivation and corrosion stages. As reported in the previous study [46], passive film breakdown may occur if OCP values of steel are more negative than − 276 mV SCE . In addition, R p kΩ cm 2 , depassivation of steel can be recorded [41,46]. ...
... As reported in the previous study [46], passive film breakdown may occur if OCP values of steel are more negative than − 276 mV SCE . In addition, R p kΩ cm 2 , depassivation of steel can be recorded [41,46]. ...
Prior to natural carbonation, a protective passive film could be formed naturally on reinforcing steel when exposure to alkaline concrete environment. To evaluate the modification of passive films caused by carbonation on a corrosion-resistant steel containing Cr and Mo in alkaline concrete pore solution, the passivation capability and passive film composition were investigated in moderate carbonation (pH = 11) and severe carbonation (pH = 9) conditions using various electrochemical measurements (OCP, LPR, EIS, M − S and CV) and X-ray photoelectron spectroscopy (XPS). The results revealed that carbonation with various contents of carbonate/bicarbonate ions could exert different effects on naturally passivated corrosion-resistant steel by modification of the chemical composition of passive films, thus providing new insights into the field application of corrosion-resistant steels in carbonated concrete.
... According to Eq. (8), increasing R p means a lower corrosion current and better corrosion resistance. When the steel bar is considered to be passive, the limited corrosion current was 0.1 μA=cm 2 (Koga et al. 2018). If the Stern-Geary equation is used with the polarization equation, the polarization resistance of the steel in its passive state can be calculated (about 10 kΩ). ...
... However, the polarization resistance was similar at the later high current densities for all specimens with and without PAC. Previous studies (Koga et al. 2018;Nguyen and Castel 2020;Zhou et al. 2018) showed that under chloride environments, the steel bar was considered to be passive at various conditions after the polarization-depolarization cycles at incrementally imposed current. However, the polarization resistances of all samples were higher than 10 kΩ at each imposed current, which indicated that no pitting corrosion was actively taking place in any specimen. ...
Due to the rapid urbanization and increased population, the production of municipal solid waste incineration fly ash (MSWI-FA) has become enormous and attracted attention worldwide. This study feasibly utilizes MSWI-FA as an immobilization host to co-dispose of ferronickel slag (FNS) through geopolymer technology. Due to the high content of heavy metals in MSWI-FA and FNS, the leachate of the geopolymer was tested with two leaching methods, in terms of acetic acid buffer solution method (AAM) and sulphuric acid & nitric acid method (SNM). Results showed that the leaching concentrations of heavy metal ions in geopolymers were less than the upper limit of Chinese landfill standard. For instance, the value of Cu, Zn, and Cr leachate in geopolymers are far lower than 100, 100, and 5 mg/L. Furthermore, various microstructural tests were performed to evaluate the stabilization/solidification behavior of MSWI-FA and FNS geopolymer, including electrochemical impedance spectroscopy (EIS) test, scanning electron microscope (SEM)/energy dispersive spectrometer (EDS), X-ray diffraction (XRD) test, and mercury intrusion porosimeter (MIP) test. The EIS results showed that geopolymer with the combination of 60 wt.% MSWI-FA, 20 wt.% ground granulated blast furnace slag (GGBS), and 20 wt.% silica fume (SF) exhibited a compact and dense microstructure, which was beneficial to the physical encapsulation of heavy metal ions. The MIP result also confirmed that the capillary pore structure of geopolymer is also developed. The SEM, EDS, and XRD results showed that the C-A-S-H, Friedel's salts, and NaCl were the main hydration products in geopolymers. The C-A-S-H was capable contributed to improve the physical encapsulation of heavy metal ions. Friedel's salts were observed to adsorb heavy metal ions on its surface and had the good binding capacity of heavy metal ions. Based on these findings, the feasibility of geopolymers are confirmed, which promote the co-disposal of MSWI-FA and FNS and provide valuable information on the MSWI-FA based construction materials.
... Peak fitting was analyzed by Thermo Avantage Version 5.52 software. (Fig. 1a), which is close to the indicator of steel passivation (E corr > − 126 mV SCE ) in alkaline solutions [26]. It is evident from Fig. 1b that E corr values of 2304 SS are slightly more negative than those for LC steel in OPC extract solution. ...
The influence of red mud (RM) on electrochemical behaviour, chemical composition, surface morphology and thickness of passive films naturally formed on low-carbon steel and 2304 stainless steel in alkaline concrete pore solutions was investigated using electrochemical measurements, XPS, AFM and SEM/EDS. Furthermore, chloride-induced pitting corrosion of passivated steels was characterized with and without RM. Results show that RM was detrimental to the passivity of steels by forming defective passive films with reduced thickness. Despite the formation of a less protective passive film on low-carbon steel, beneficial role of RM was highlighted in preventing chloride-induced depassivation and corrosion propagation.
... Many studies have tried to relate the corrosion potential to the corrosion rate, but no quantitative correlation has been found. When measurements are made in highly controlled conditions (RH, T), a robust correlation exists between the two parameters for small specimens, especially for the high corrosion probability range [285]. However, in field investigation, the environmental factors cannot be so controlled. ...
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 RC structures, 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, non-uniform 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.
... Still noteworthy from an economic point of view, the feasibility of BYF production in conventional cement plants has been demonstrated in industrial trials [6,7]. The possibility of using inexpensive steel rebars as reinforcement has also been confirmed based on the electrochemical responses of the mild steel | BYF interface in terms of both passivation ability and film breakdown related to endogenous or exogenous chloride contamination [8][9][10][11] as well as their corrosion risk assessment [12]. Beyond economic concerns, BYF cements have been proposed as a less-polluting binder to produce building materials, as their production may release up to 30% less CO 2 into the atmosphere compared to the OPC manufacturing [6]. ...
This work reports the evolution of the phase assemblage, pore solution, porosity, and mechanical resistance of Belite-Ye'elimite-Ferrite (BYF) cement pastes. Different water-to-cement (w/c) ratios were considered and the addition of fly ash (FA) evaluated. The initial 1-day hydration of BYF cement paste was characterized by the ye'elimite hydration accompanied by a pronounced alkalinity increase controlled mainly by the molar ratio of calcium sulfate to ye'elimite. Throughout the 1-year test, the phase assemblages of 0.50 and 0.67 w/c samples were similar, composed of ettringite, AFm, strätlingite, silicious hydrogarnet, and C-S-H. The hydration of the 0.40 w/c cement paste was almost complete within a month. Additions of 25 wt% FA increased the fraction of strätlingite and ettringite without long-term strength losses compared to plain BYF cement paste with the same water-to-binder ratio. Results from different characterization techniques for both liquid and solid phases at early-age (first 24 h) were complemented by thermodynamic calculations.
... For RC structures, the occurring electrochemical processes at the passive layer (a region between the concrete and the surface of the steel) along with reinforcement corrosion complicate understanding and measurement [8]. However, ASTM C876 [9] standard was developed as a guideline for monitoring reinforcement corrosion through empirical-based potential measurement. ...
Corrosion initiation time of embedded steel is an important service life parameter, which depends on concrete material make-up, exposure environment, and duration of exposure. Early and accurate determination of corrosion initiation time will aid in designing durable reinforced concrete, saves cost and time. This study leveraged on the power of ensemble machine learning by combining the performances of different models in estimating the corrosion initiation time of steel embedded in self compacted concrete using corrosion potential measurement. The concrete specimens were prepared with limestone powder as supplementary addition to Portland cement and was exposed to 5% sodium chloride in accordance with the requirements of ASTM C876-15 for 8 months. During the exposure, corrosion potential of the embedded steel was measured, and the recorded datasets were used in training five different machine learning models. With cement, limestone powder, coarse aggregate, fine aggregate, water and exposure period.as input variables, five different models were developed to estimate the corrosion initiation time (determined from the corrosion potential measurements) of the embedded steel. With respect to model predictive performance, the acquired results demonstrated that the random forest (RF) ensemble model amongst other trained models performed best with 85/15 dataset percentage split for the training and testing. RF ensemble performed best with CC and RMSE of 99.01% and 18.2747 mV for training, and 98.67% and 25.0298 mV for testing respectively. Hence, due to its superior and robust performance, this study proposes RF ensemble model in the estimation of corrosion initiation time of embedded steel in reinforced limestone-cement blend concrete.
... This is the case of free chlorides deriving from seawater and deicing salts, which can promote corrosion of reinforced concrete whose lifespan is therefore reduced. The reliable assessments of the performance of reinforced cementitious structures regarding chloride-induced corrosion are essential for predicting the service life of reinforced structures exposed to chloride sources as well as to develop good practices during the design phase to avoid premature corrosion [16][17][18]. ...
Reinforced Belite-Ye'elimite-Ferrite (BYF) mortars cured for different times and exposed for 90 and 182 days to a chloride-rich solution (full immersion and dry/wet cycles) were compared to Portland equivalents in terms of porosity, corrosion, chloride ingress and sorptivity. The effect of fly ash addition was also considered. BYF- and Portland-embedded rebars remained passivated through 182-day testing. The apparent chloride diffusion coefficients were about 10−12 m² s-1, except for 28-day-cured BYF mortars containing fly ash, which exhibited higher values. The results contribute to a better assessment of durability issues concerning BYF matrices, indicating they can be a reliable alternative to Portland.
... Potential readings were recorded versus time at room temperature (20 ± 1°C). The data acquisition and interpretation were based on the ASTM C876-09 [21] and RILEM TC 154-EMC [22]; the validity of the ASTM C876 was recently verified and the standard has shown to be a reliable tool to evaluate the corrosion risk of reinforced OPC and BYF matrices [23]. LPR measurements were performed with a 20 mV amplitude, 10 mV min −1 scan rate, being the ohmic drop compensation considered as per [7]. ...
Carbon steel rebars passivate in Belite-Ye'elimite-Ferrite mortars, despite the initial low pH of the pore solution compared to Portland equivalents. Besides passivation ability, another important durability issue is the maximum allowed chloride content in the fresh mix beyond which passivation is prevented, normally 0.4% of chloride by cement mass for reinforced Portland concretes. This work aims to evaluate the impact of different endogenous chloride contents on the evolution of the electrochemical and physicochemical responses of reinforced mortars and neat cement pastes. It is shown that steel in BYF mortars contaminated with up to 0.4% of chlorides effectively passivate but the time needed to passivation is longer than for OPC mortars. Sodium chloride contamination was also found to retard the BYF hydration due to a delayed belite and ferrite hydration. Results showed that higher w/c ratio decreases the tolerable chloride content from 0.4%, BYF (w/c = 0.50) to 0.2%, BYF (w/c = 0.67).
Limestone calcined clay cement (LC3) concrete has attracted world-wide attention as a newly promising low-carbon concrete. In this study, long-term reinforcement corrosion in LC3 concrete was investigated. Both chloride and carbonation-induced reinforcing bar corrosion were examined. Open circuit corrosion potential, polarization resistance, Tafel constants were monitored at regular intervals up to 500 days. Gravimetric mass loss was measured and compared to the loss of mass calculated using electrochemical methods. The performance of concrete with flash calcined clay and limestone was similar to that of traditional Portland cement concrete in long-term investigation. Traditional corrosion methods and classifications used widely to assess of steel in concrete can be applied to concrete containing LC3 providing a recalibration of polarization resistance range for passitivity condition.
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.
A research work was carried out to investigate the effectiveness of high-strength self-compacting concrete (SF-R) in controlling corrosion of embedded steel. Reinforced concrete cylinders and plain cubes were subjected to 5% NaCl solution. Slump flow, J-ring, V-funnel, compressive strength, electrical resistance, and electrochemical tests were conducted. Corrosion resisting characteristics of steel were examined by monitoring corrosion potential, polarization resistance, corrosion currents, and Tafel plots. The relationship between corrosion current density and corrosion potential was established. Results were compared with characteristics of a grade 40 MPa reference concrete (R) and grade 70 MPa conventional self-compacting concrete (SP). Results indicated that at 270 days of exposure, the corrosion currents for steel in SF-R were 63- and 16-fold lower compared to those of steel in R and SP concretes, respectively. This concrete showed a considerable increase in electrical resistance and compressive strength of 96 MPa at 28 days of exposure. Relying on corrosion risk classification based on corrosion current densities and corrosion potentials, the steel in SF-R concrete is definitely in the passive condition. The splendid durability performance of steel in SF-R concrete linked to adorable self-compacting features could furnish numerous opportunities for future structural applications in severe environmental conditions.
The article discusses the half-cell potential measurements for reinforced concrete structures. The half-cell potential measurements can be performed on structures with ordinary or stainless steel reinforcement. The method can be applied regardless of the depth of concrete cover and the rebar size and detailing. The measurements indicate corroding rebars not only in the most external layers of reinforcement facing the reference electrode but also in greater depth.
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![Nicholas J. Carino]()
A critical step in selecting the most appropriate repair strategy for a distressed concrete structure is to determine the corrosion status of reinforcing bars. Because of the complexity of the corrosion process, it is prudent to involve personnel who are experienced in the corrosion of steel in concrete. The corrosion engineer may employ a variety of tools to help make an assessment of the corrosion conditions. This paper provides an overview of the corrosion of steel in concrete and presents some nondestructive electrochemical tools that are commonly used in corrosion investigations. The objective is to provide the repair specialist with basic information to allow effective communication with the corrosion engineer. Electrochemical principles involved in the corrosion of steel in concrete are reviewed. Subsequently, the half-cell potential method, the concrete resistivity test, and the linear polarization method are discussed. The principles of operation and the inherent limitations of these methods are emphasized.
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![Ueli Angst]()
This paper summarizes the grand societal, economic, technological, and educational challenges related to corrosion of steel in concrete, and presents the state-of-the-art of the most relevant issues in the field. The enormous financial impact of infrastructure corrosion seems to be inadequately balanced by educational and research activities. This presents a unique opportunity in many countries for maintaining or improving their competitiveness, given the major technological challenges can be solved. The main technological challenges are (1) the ever-increasing need to cost-effectively maintain existing, ageing reinforced concrete structures, and (2) designing durable, thus sustainable new structures. The first challenge arises mainly in industrialized countries, where there is a need to abandon conservative, experience-based decision taking and instead move to innovative, knowledge-based strategies. The second challenge regards mainly emerging countries expanding their infrastructures and where thus a major beneficial environmental impact can still be made by providing long-lasting solutions. This means to be able to reliably predict the long-term corrosion performance of reinforced concrete structures in their actual environments, particularly for modern materials and in the absence of long-term experience. During the second half of the last century, civil engineers, materials scientists, and chemists have in many countries made considerable attempts towards understanding corrosion of steel in concrete, but many of the approaches got bogged down in empiricism. From reviewing the state-of-the-art one can conclude that transport modeling in concrete is relatively well-advanced, at least in comparison with understanding corrosion initiation and corrosion propagation, where many questions are still open. This presents a number of opportunities in scientific research and technological development that are discussed in this paper.
An extensive experimental program was designed to investigate the passivation of reinforced low carbon-release Belite-Ye'elimite-Ferrite (BYF) cement mortars compared to the passivation of reinforced conventional Portland equivalents (OPC). The influence of formulation parameters such as the water-to-cement ratio and the presence of fly ash on the steel rebar passivation was evaluated by conventional corrosion measurements such as corrosion potential readings and linear polarization resistance. Visual observations were carried out as a complement. A negligible corrosion rate was reached after 28 days with BYF cement against 14 days with OPC equivalent. This difference is attributed to the pH of the medium in the BYF mortars, which is lower than in the OPC mortars at a very early age, before becoming strongly basic. The exploitation of the Tafel slopes showed that the corrosion current can be evaluated by the Stern and Geary equation with an identical B coefficient for the samples of BYF and OPC basis. Despite some differences compared to the passivation in Portland mortars, the present study clearly points to the BYF mortars intrinsically passivating nature regarding mild steel reinforcing bars.
- S. Feliu
- J. A. González
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![Cid Andrade]()
A review on the available electrochemical methods is presented for the on-site determination of rebar corrosion rate. In real size structures the methods available at present may be classified in three groups: A) Confinement of the applied electrical signal, B) Measurement of the lateral spreading of the electrical signal and C) Minimization of this lateral spreading. From these three alternatives, the first one has been implemented in a device that is now currently used for on-site measurements. This device is based in a "controlled" guard ring. In real size structures, the normal values of corrosion rates recorded are of the same order of magnitude of those previously measured in laboratory experiments The levels are classified in: negligeable, low, moderate and high. The gaps in the knowledge which still need to be investigated are also, commented: 1) unconfined measurements, 2) effect of counterelectrode size, 3) the true meaning of the corrosion rate measured, 4) constant B value, 5) current distribution around rebar perimeter 6) relation between mean corrosion rate and maximum pit depth and 7) identification of local corrosion. Finally, the role of embedded sensors on the monitoring of rebar corrosion risk, is mentioned.
Reinforced concrete prisms with varying surface conditions (sealed, partially sealed, and unsealed) and curing environments (in air and submerged in water) were used to vary the oxygen concentration in laboratory experiments. The experiment results (current rate and half-cell potential) of these tests were used to establish the time-dependent influence of oxygen concentration on passive film formation and corrosion of the reinforcement steel embedded in concrete under various defined conditions. It was found that the adequate availability of free oxygen during the initial curing stage is crucial for the proper formation of the passive layer. This suggests ways to improve passive layer development, and thus the durability of reinforced concrete structures, through the use of curing procedures that control both moisture and oxygen availability.
- Brian B. Hope
- Alan K.C. Ip
The effects of chloride in concrete containing admixed calcium chloride dihydrate and chloride-bearing aggregates on microcell corrosion were studied. Concrete slabs, each containing three electrically isolated steel rods, were subjected to various outdoor and indoor exposure conditions. Corrosion of the rods was examined by the linear polarization and AC-impedence techniques, visual inspection, and gravimetric mass loss method. Chloride and pH measurements for the concretes were also conducted. Electrical resistivities of the concrete increased with increasing admixed chloride content, and pH of the concretes was in a range from about 12 to 12. 5, regardless of the chloride content and aggregate type.
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![Bernhard Elsener]()
- H. Bohni
The results of potential mapping surveys of bridge decks of the Swiss highways, using a new eight-wheel electrode measurement system, are reported here. A comparison of the state of corrosion of the rebars (obtained by visual inspection after removing the concrete cover), including the potential fields in addition to theoretical considerations, clearly demonstrates that an absolute potential value (that is, - 350 mV copper sulfate electrode (CSE) as proposed in ASTM Test for Half-Cell Potentials of Uncoated Reinforcing Steel in Concrete (C 876-80) for the identification of active corrosion of steel in concrete does not exist. Combining the local potential gradient on the surface with information on the electrical resistivity of the concrete (measured with the four-point method or a-c impedance) allows determination of a rough estimate of the corrosion rate in a single macrocell. Impedance spectroscopy, well suited for studying corrosion mechanisms in the laboratory, was found to be too time consuming and difficult to interpret in field measurements. Instead, a very rapid new technique-using galvanostatic pulse measurements-was tested successfully on site. It gives clear, unambiguous results on the corrosion state of the rebars, when half-cell potential measurements are uncertain.
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![Muhammad Wasim]()
Corrosion of reinforced concrete is one of the most critical durability concerns in the construction field. Researchers and engineers are examining and determining the performance of various types of reinforced concrete in saline and under various environmental conditions. This research is also a contribution to such corrosion studies and it aims at investigating passive film formation and the corresponding corrosion and its extent in the ordinary (OC), self-compacting (SSC) and lightweight concrete (LWC) structures at normal and elevated temperature. For this purpose total of 18 specimen including 6 specimens of each OC, SCC and LWC were prepared with 5% and 3% total chloride, respectively and kept in environmental chambers at 30, 40 and 50 °C. After six months of corrosion observations i.e., corrosion potentials, currents and gravimetric mass loss, interesting and novel results were obtained on comparing the corrosion observations of all the above types of concrete.
- Laura Kotovsky
- R. Baillargeon
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![Olivier Baujard]()
- S. Feliu
This paper experimentally confirms the participation of diffusion in the response of reinforced concrete specimens to the different electrical signals applied. Therefore, in the modelling of the steel-concrete system, it seems necessary to incorporate elements representing the diffusion together with the effects of the corrosion reaction and the non-ideal capacitative behaviour at the interface. A knowledge of the interaction between all these phenomena is indispensable for interpreting the response of the system to the application of DC and AC signals, and for the correct estimation of the corrosion rate of reinforcements. An examination is made of which equivalent circuit might be most suitable for modelling the system.
- S. J. Ford
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![John Shane]()
- T. O. Mason
This paper presents a systematic study of the features seen in typical Nyquist plots (-imaginary vs. real impedance) for cement-paste/steel systems and discusses the assignment of each feature to its appropriate origin, e.g., bulk, contact, interface, product layer, etc. Assignments are made based upon as many considerations as possible—dc measurements, sample geometry, capacitance, local chemical modifications, alternative electroding schemes, etc. In addition to three distinct arcs from lowest (mHz) frequency to highest (MHz) frequency (due to product layer, interfacial reaction, and bulk, respectively), a fourth arc is sometimes observed between the bulk and interface arcs. When this occurs in paste-only systems, this arc is attributable to imperfect electrodes due to drying/shrinkage. In composite systems, e.g., cement with conductive chopped fibers added, this arc is clearly a "bulk" feature and an important indicator of microstructural inhomogeniety.
1. SCOPE This Recommendation covers the description of non- destructive electrochemical test methods for the estimation in large size concrete structures of the instantaneous corrosion current density, ioorr, expressed in gA/cm 2, by means of the so-called Polarization Resistance technique, R o, in order to assess the condition of embedded steel reinforcement related to its corrosion. The values of i~orr, Can be used to assess the rate of degradation of concrete structures affected by reinforcement corrosion. However, they cannot give information on the actual loss in steel cross section which, at present, only can be assessed by means of direct visual observation. Values of the free corrosion potential or half-cell potential, Ecorr (V), of the embedded reinforcing steel and of the electrical concrete resistance, Re (f)), are obtained as preliminary steps of the Rp measurements. Values of the concrete resistivity, P (~m), can be calculated from Re values providing the geometrical arrangement of the electrodes enables this calculation. Both parameters, Ecorr and Re (or P) may be used to complement the reliability of the ico~r measurements.
- U. Bertocci
- F. Huet
- P. Rousseau
- R.P. Nogueira
Removing direct current (DC) trends before calculating standard deviations and power spectral densities is a necessary operation, but the choice of method is probably one of the most difficult problems in electrochemical noise measurements. The procedure must be simple and straightforward and must effectively attenuate the low-frequency components without eliminating useful information or creating artifacts. Several procedures are presented, including moving average removal (MAR), linear detrending, polynomial fitting, and analog or digital high-pass filtering. Their effect on electronic and electrochemical signals is discussed. The results show that the best technique appears to be polynomial detrending. In contrast, the recently proposed MAR method was found to have considerable drawbacks and its use is not recommended.
- RN COX
- KWJ TREADAWAY
- BL BROWN
A ten-year exposure study has examined the performance of reinforcing steels with higher than normal corrosion resistance embedded in concrete. The steels included in the programme were a weathering steel, galvanized steel, types 405 and 430 ferritic and types 302, 315 and 316 austenitic stainless steels. The performance was compared with that of grit-blast cleaned and pre-rusted high-yield steel. The concretes examined (1:6 and 1:8 cement: aggregate mixes) contained a range of added chloride to enhance corrosion activity. The results have illustrated the excellent resistance of the austenitic stainless steels in comparison with all the other steels when embedded in concrete containing the highest concentrations of chloride. They have also indicated the corrosive nature of the chloride ion and underline the need to control chloride concentrations to the limits now set in BS 8110.
- Han-Young Moon
- Kook-Jae Shin
This study aims to evaluate frost durability and steel-bar corrosion in antiwashout-underwater concrete, which has been neglected to date. To achieve this goal, repeated freezing and thawing and accelerated steel-bar corrosion tests have been performed for three types of antiwashout-underwater concrete specimens.The results of repeated freezing and thawing test reveal that adding mineral admixtures has little effects on frost durability because of the large and uneven entrapped-air imprisoned by the cellulose-type antiwashout-underwater admixture. Slight improvement of frost durability was observed through the action of air-entrained (AE) agent in the case of SG50 which presented an air content of 6 ± 0.5%.Measurement results using the half-cell potential showed that, among the entire specimens, steel-bar in Control specimen manufactured under artificial seawater was the first one that exceeded the threshold value, −350 mV proposed by ASTM C 876, at 14 cycles, where the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 μA/cm2 and 0.258%, respectively. For the other specimens, potential values became below −350 mV later than 18 cycles.
The aim of this study is to examine the influence of N,N′-dimethylaminoethanol (DMEA) as an inhibitor on the chloride threshold level for corrosion of steel in a concrete contaminated by chlorides. The experiment has been carried out in a saturated Ca(OH)2 solution and chloride contaminated concrete containing different chloride and DMEA level. The critical point of corrosion onset is concluded by combining the open-circuit potential (Ecorr) with corrosion current (Icorr), which is decided by electrochemical impedance spectra (EIS) in the solution. Besides, the EIS has also been applied to determinate the chloride threshold level in the chloride contaminated concrete. It has been found that the presence of DMEA represented as an amino-alcohol inhibitor, exerts little influence on the chloride threshold level for corrosion of steel in the solution. Similarly, the effect of the DMEA on the chloride threshold level in the chloride contaminated concrete, is also negligible.
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![Paul Lambert]()
- C.L. Page
- P. R. W. Vassie
Corrosion rates of steel rods embedded in concrete specimens similar to those of Part 1 have been determined by linear polarization. For specimens exposed to external sources of chloride the probability of depassivation increased with the chloride: hydroxyl concentration in the pore solution, beyond a threshold ratio of approximately 3. Thereafter corrosion was subject to anodic control. Chlorides introduced as admixtures tended to promote corrosion at somewhat lower chloride: hydroxyl ratios. Rankings of the materials and exposure regimes studied in terms of their corrosion severity have been established, and problems in relating the behaviour of laboratory specimens to that of reinforced concrete structures are considered.
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![Shamsad Ahmad]()
Reinforcement corrosion has been widely reported in the literature over the last two to three decades. It is one of the major durability problems, mainly when the rebar in the concrete is exposed to the chlorides either contributed from the concrete ingredients or penetrated from the surrounding chloride-bearing environment. Carbonation of concrete or penetration of acidic gases into the concrete, are the other causes of reinforcement corrosion. Besides these there are few more factors, some related to the concrete quality, such as w/c ratio, cement content, impurities in the concrete ingredients, presence of surface cracks, etc. and others related to the external environment, such as moisture, oxygen, humidity, temperature, bacterial attack, stray currents, etc., which affect reinforcement corrosion. The assessment of the causes and extent of corrosion is carried out using various electrochemical techniques. Prediction of the remaining service life of a corroding RC structure is done with the help of empirical models and experimental methods. In this paper a review is presented on the mechanism of reinforcement corrosion, techniques utilized to monitor reinforcement corrosion and methodologies that are utilized for the prediction of remaining service life of structures.
The chloride threshold to develop active corrosion of the reinforcing steel does not seem to be a unique value and it depends on several factors, such as concrete mix proportions, cement type, C3A content of cement, blended materials, water/cement ratio, temperature, relative humidity, steel surface conditions and source of chloride penetration among others. Numerous studies have been already devoted to the study of the chloride threshold value for depassivation of the steel embedded in concrete. One of the reasons found for the scatter is the large number of variables that influence the chloride amount for depassivation. The other reason is the lack of accordance for the definition of the chloride threshold itself, either on the determining parameters (visual observation, corrosion potential or corrosion current) or on the expression of the threshold (as Cl−/OH− ratio or by weight of cement or concrete).The present paper presents chloride thresholds that were studied in mortar based on corrosion current measurements and expressed as total, free and Cl−/OH− ratio. For this study, mainly smoothed bars were used, but also some ribbed bars were tested. Chloride thresholds in the range of 1.24–3.08% and 0.39–1.16%, by weight of cement, for total and free chlorides, respectively, and in the range of 1.17–3.98 for Cl−/OH− ratio were found for chlorides admixed in the mixing water. Active corrosion is considered when, in a small exposed area, the corrosion rate of the rebar is higher than 0.1 μA/cm2. The threshold in the case of Cl−/OH− results a bit higher than that found in a previous work for synthetic pore solution, although the two types of data can be fitted together finding a good correlation.
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![Obada Kayali]()
- B. Zhu
High-strength reinforced silica fume–cement concrete slabs with a compressive strength of 70 MPa were tested for chloride diffusion and corrosion activity after partial immersion in a 2% chloride solution. Similar slabs with 32 MPa conventional concrete were tested in the same environment. Chloride diffusion in high-strength concrete was extremely low. In contrast, a high level of chloride concentration well beyond the depth of steel was noted in 32 MPa concrete. The corrosion potentials in 32 MPa concrete continued to gain larger negative values, far more than the threshold value of −350 mV (CSE). The potential values in high-strength concrete remained fairly stable and were in the vicinity of −200 mV (CSE). Corrosion current density in 32 MPa concrete acquired active values in relatively short time. In high-strength concrete, corrosion current density did not approach the threshold activation value. There is evidence that improvement in corrosion resisting property in high-strength concrete continues after the first 28 days of curing while such improvement does not occur in conventional concrete of 32 MPa. It is concluded that high-strength concrete containing 10% silica fume possesses exceedingly high corrosion resistance.
Under field conditions, steel is embedded in concrete for a long period of time before chlorides penetrate. In studying the corrosion behaviour of steel in concrete, mortar or in simulated pore solution, it is essential to allow enough time for the steel to create a passive layer which is the subject of this study. This time is given to steel in chloride free concrete, naturally; while it should be provided to steel in synthetic pore solution, before adding chloride to the solution. For determining this time, samples were made with steel with different surface conditions: as-received with mill scales and sand-blasted. One set of steel bars (as-received and sand-blasted) were embedded in mortar and one set were immersed in synthetic pore solution. Corrosion of each steel bar was monitored every hour by LPR technique for total time of 300 h. Also, half-cell potential of steel bars was measured during that time. Results show that steel needs to be kept at least three days in synthetic pore solution and seven days in mortar to be passivated.
- P. Gu
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![J. J. Beaudoin]()
An engineer is interested in half-cell potential measurements because they give an idea about the possible state of corrosion of the steel reinforcement in concrete. Interpreting such measurements is trickier than just slapping one electrode here and another one there, and reading something meaningful from a voltmeter. After all, the concrete in the structure may have undergone carbonation, suffered chloride ion intrusion, and been mixed with anodic or cathodic corrosion inhibitors. The measurements are influenced by these and many other factors. Therefore, their correct interpretation is a matter of knowing what exactly the influences amount to. Les ingénieurs s'intéressent aux relevés de potentiel par demi-pile parce que ceux-ci donnent une idée du degré de corrosion de l'armature d'acier contenue dans le béton. Pour interpréter ces relevés, il ne suffit pas de flanquer une électrode ici et une autre là, et de faire la lecture des résultats sur un voltmètre. Après tout, le béton dont est fait l'ouvrage peut avoir subi une carbonatation, sa concentration en ions chlorure peut avoir augmenté, ou on peut lui avoir ajouté un inhibiteur de corrosion anodique ou cathodique. Ces facteurs, et bien d'autres, influent sur les relevés. Pour interpréter correctement ceux-ci, il faut donc connaître l'effet exact de ces facteurs. PRAC
- J P Broomfield
J.P. Broomfield, Corrosion of Steel in Concrete, 1st ed., Taylor & Francis, Abingdon, UK, 1997, https://doi.org/10.4324/9780203414606.
Corrosion of Steel in Concrete
- L Bertolini
- B Elsener
- P Pedeferri
- R B Polder
L. Bertolini, B. Elsener, P. Pedeferri, R.B. Polder, Corrosion of Steel in Concrete, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, FRG, 2003, https://doi.org/10. 1002/3527603379.
Standard Test Method for Half-cell Potentials of Uncoated Reinforcing Steel in Concrete
ASTM C876-09, Standard Test Method for Half-cell Potentials of Uncoated Reinforcing Steel in Concrete, ASTM International, West Conshohocken, 2009, https://doi.org/10.1520/C0876-09.2.
Monitoring the Corrosion of Concrete Reinforcement Using Control Curves
- N Birblis
- B W Cherry
- B Gerritsen
- M Forsyth
N. Birblis, B.W. Cherry, B. Gerritsen, M. Forsyth, Monitoring the Corrosion of Concrete Reinforcement Using Control Curves, in: Int, Conf. Durab. Build. Mater. Components, Brisbane, 2002, pp. 1-6 http://dro.deakin.edu.au/view/ DU:30029980.
- G Y Koga
G.Y. Koga et al. Electrochemistry Communications 94 (2018) 1-4
Source: https://www.researchgate.net/publication/326526814_Revisiting_the_ASTM_C876_standard_for_corrosion_of_reinforcing_steel_On_the_correlation_between_corrosion_potential_and_polarization_resistance_during_the_curing_of_different_cement_mortars
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