Corrosion Of Steel Bars Research Articles

Potential application of Ginkgo biloba extract as a green corrosion inhibitor for carbon steel reinforcement in chloride-polluted simulated concrete pore solution

The present work describes the development of a green and sustainable corrosion inhibitor using the extract of Ginkgo biloba fruit (GBFE). The screening of the inhibitory performance of GBFE was done in a simulated concrete pore solution (SCPS). The results report that GBFE inhibits B450 ribbed steel bar (RSB) corrosion and represents a significant decrease in corrosion rate with the rising dose at 50 °C temperature. Electrochemical experiments manifest that GBFE can restrain reactions of the cathode and anode of RSB. The molecular adsorption of GBFE is governed by Langmuir adsorption isotherm. The main active components were classified using Fourier Transform Infrared Spectrometer (FTIR) and Mass spectrometry (MS). The morphology maps of surface analysis support the creation of an inhibitive layer of GBFE over the RSB surface. DFT and MC describe the adsorption of GBFE over the RSB.

Characteristics of the non-uniform corrosion of the steel bars extracted from the marine transportation infrastructures

This paper investigates the spatial morphological characteristics of non-uniform corrosion of reinforced concrete in coastal areas. A series of naturally corroded reinforced concrete specimens were retrieved from marine transportation infrastructure. Non-destructive tests were conducted by X-ray computed tomography (CT). The morphological propagations of the corrosion pits were explored, and the spatial distribution of non-uniform corrosion of the steel bars was analyzed in both longitudinal and circumferential directions. The results show that the non-uniformity of corrosion is related to both the corrosion degree and the morphology of corrosion pits. When the morphology of corrosion pits is similar, non-uniformity decreases exponentially with the corrosion degree of the steel bars. The morphologies of corrosion pits can be divided into two main categories: surficial corrosion pits and deep corrosion pits. The morphologies are related to the non-uniformity of the concrete surrounding the steel bar. When the corrosion degrees are similar, deep corrosion pits are more significant than surficial corrosion pits for the non-uniformity of the corrosion. The eccentricity was adopted to quantify the corrosion non-uniformity of bars with high corrosion degrees. These results provide a new perspective for evaluation on the non-uniform corrosion of steel bar in the marine transportation infrastructures.

Evaluation of combined addition of nitrite and chloride on the corrosion behavior of steel bars in modified magnesium oxysulfate cement paste

Magnesium oxysulfate (MOS) cement, a new breed of eco-friendly and carbon-efficient material, boasts exceptional corrosion resistance, especially in harsh environments such as high salt and high humidity. Understanding how it affects the corrosion of steel bars is crucial for its widespread application in coastal concrete engineering. Nitrite-based inhibitors are known for their rust-preventing qualities in cementitious materials. However, more research is needed to determine if nitrite remains effective in MOS cement mixed with chloride salts. This study focuses on the combined effect of chloride and nitrite salts on the corrosion of steel bars in MOS cement. Methods like corrosion area rate, weight loss rate, natural potential, and electrochemical station are employed to study the corrosion behavior of steel in MOS cement. Microscopic techniques help unravel the influence mechanism of phase composition and microstructure on these materials. Furthermore, the study examines how chloride and nitrite contents affect the concentration of free nitrite and chloride ions in MOS cement paste. The analysis model is also established to compare simple linear adsorption, Langmuir adsorption, and Freundlich adsorption. The results indicate that chloride accelerates steel corrosion, while nitrite slows it down in the environment of mixed chloride and nitrite. In low-chloride environments, nitrite content has minimal impact on steel corrosion, but its effect becomes more pronounced in high-chloride settings. The MOS cement mixed with chloride and nitrite primarily consists of Mg(OH)2, MgCl2, MgCO3, MgO, and the 5Mg(OH)2·MgSO4·7 H2O (517 phase). The phase content of passive film on the surface of steel bar is composed primarily of Fe2O3, FeO, Fe, and FeOOH in descending order. As nitrite content increases, the absorption and concentration of free nitrite ions in the MOS cement paste gradually rise, exhibiting a linear trend. Based on the fitting calculations for three distinct adsorption relationships, notably, due to the limited adsorption capacity of MOS cement for nitrite, there's a considerable difference between the simple linear adsorption relationship and the two nonlinear adsorption models in high nitrite environments. However, in low nitrite concentrations, the difference among these three fitting adsorption relationships is little. This research can provide theoretical basis for enhancing the corrosion resistance and durability of coastal concrete engineering with high chloride exposure.

Research Progress on the Transport and Prediction of Chloride Ions in Concrete Structures

Reinforced concrete structures are widely used in practical engineering, and the durability issues of such structures under chloride environments have been a hot research topic. Chloride ions can cause corrosion of internal steel bars in structures under the action of chloride salt, leading to structural cracking, decreased bearing capacity, and ultimately affecting the structural safety during service life. Therefore, comprehensive and systematic research on chloride ion transport and prediction in concrete structures is crucial. This paper reviews the recent research progress on chloride ion transport in concrete structures both domestically and internationally, introduces the latest research results on chloride ion transport mechanisms, transport laws, prediction methods, and points out the limitations and future research directions in existing research on chloride ion transport and prediction in concrete structures.

Characteristics of corrosion products of steel bars in modified magnesium oxysulfide cement containing chloride salts

The effects of chlorides on the corrosion of steel bars within a matrix comprising modified magnesium oxysulfide (MMOS) cementitious materials was investigated. The phase composition, morphology and distribution of steel corrosion products (SCPs) were studied. There was basically no corrosion of the steel bars in the MMOS cement without chlorides. A high chloride content and a high water/cement (w/c) ratio in the MMOS matrix had adverse effects on the steel bar corrosion. The primary SCPs in the MMOS mixes were iron oxyhydroxides (FeOOH) and ferric oxide (Fe2O3), while ferrous oxide (FeO) was only observed at low w/c ratios, indicating a lower degree of oxidation. The presence of di-iron nonacarbonyl (Fe2(CO)9) at high w/c ratios suggested a higher degree of oxidation. At lower w/c ratios, rust products readily diffused. Conversely, at higher w/c ratios, these products accumulated close to the steel bars, resulting in a compact structure.

The Impact of Climate Change and Carbonation on the Durability of Concrete Structures in Afghanistan

Infrastructure plays an important role in human settlements, offering essential facilities such as buildings, transportation and other necessary systems. However, the impacts of climate change, whether direct or indirect, create various challenges for human settlements and ecosystems. This study investigates the dual impact of climate change and carbonation on the durability of concrete structures in Afghanistan. The durability of reinforced concrete is significantly affected by the corrosion of steel reinforcement, and carbonation is the main factor causing corrosion of steel bars in concrete. With shifting climate patterns influencing environmental conditions, this study aims to analyze how these changes contribute to the carbonation process in concrete and the results will contribute to a deeper understanding of the challenges posed by climate-driven changes and carbonation, thereby providing the basis for necessary measures to minimize the environmental impacts. To facilitate this investigation, (75x75x75mm) concrete cubes were prepared and after 28 days of curing in laboratory conditions, the specimens were exposed in four different regions: Afghanistan, Japan, Indonesia and Malaysia. The carbonation depths were measured at the ages of 6 months and one year. Considering the environmental and climatic conditions of all mentioned regions, despite Kabul's lower humidity and temperature, the carbonation was still significant compared to the other regions. This substantial carbonation poses a threat to structures, emphasizing the need for special attention in the design phase to ensure resilience against climate-induced challenges.

Oxygen diffusion into unsaturated seawater and sea sand concrete and its effect on non-uniform corrosion of steel bars

Oxygen diffusion in reinforced concrete (RC) is a crucial factor affecting the corrosion of steel bars under a high chloride environment, while it is also controlled strongly with the saturation degree of the concrete. Therefore, the objective of this work is to elucidate the diffusion of oxygen in unsaturated concrete and its effect on the corrosion of steel bars. In this work, a self-made device is developed to study the oxygen diffusion in seawater and sea sand concrete (SSC) and the wire beam electrode (WBE) technique is innovatively used to investigate the effect of oxygen on the corrosion of steel bars. The oxygen diffusion coefficient of SSC was decreased maximum by 97.3 % with the internal relative humidity (RH) of concrete increasing from 12 % to 88 %, it was increased by 96.5 % when the water-binder ratio increased from 0.18 to 0.48. A multi-factor coupling model considering the relative humidity and strength of concrete was developed to estimate the oxygen diffusion coefficient of concrete. The corrosion process of steel bars was tracked by the WBE technique and it presented as the formation and propagation of the local anode zone. However, the electrodes were still in a passivation state after corrosion for 120 d when the water-binder ratio was lower than 0.28 or the oxygen concentration was lower than 21 % even in SSC. Therefore, the pitting anode zone will be shrunk and the corroded steel bars were re-passivated with insufficient oxygen supply during the late service process.

Combined deterioration effects of freeze–thaw and corrosion on the cyclic flexural behavior of RC beams

Reinforced concrete (RC) stands as the predominant construction material, and with the growing prevalence of aging infrastructure, the safety assessment of deteriorating structures has emerged as a pressing and critical concern. This study presents an experimental investigation into the combined effects of freeze–thaw cycles (100, 200, and 300 cycles) and corrosion (corrosion ratio: 3% and 10%) on the cyclic behavior of RC beams. Seven RC beam specimens with varying types and levels of deterioration were fabricated, and static tests were conducted using a four-point bending method to assess the behavior of RC beams under each degradation factor. The experimental results revealed that increasing freeze–thaw cycles significantly impact RC beam behavior, leading to intensified crack formation due to cyclical frost-heaving pressure. This ultimately results in reduced yield loads ranging from 3% to 11% and peak loads reduced by 1–2% compared to the reference specimen A-0-0. Corrosion of steel bars in RC beams alters failure modes, with corroded specimens (C-0-3 and C-0-10) experiencing substantial decreases in yield load, a 15% reduction in C-0-3, and a 26% decrease in C-0-10, compared to A-0-0. Displacement at yield load and peak load also decreased, highlighting the detrimental impact of corrosion on beam mechanical properties. The combined deterioration from freeze–thaw cycles and corrosion further exacerbates these reductions, resulting in a substantial decrease in yield load (32%) and peak load (24%) in D-3-10 compared to the reference specimen A-0-0. Additionally, energy dissipation capacity and cumulative energy dissipation capacity exhibit dynamic changes influenced by the progression of freeze–thaw cycles, corrosion, and their combined effects.

Time-dependent seismic fragility analysis of reinforced concrete columns subjected to chloride-induced corrosion

This paper presents a stochastic methodology to perform time-dependent seismic fragility analysis for reinforced concrete (RC) columns subjected to chloride attacks. Numerical modelling methods considering the increasing variability of reinforcement mechanical properties were proposed based on the stochastic constitutive model for corroded steel bars. Depending on the finite element model validated by test data for uncorroded and corroded RC columns, two novel stochastic cases and a traditional deterministic case were introduced and then applied to pushover analysis, incremental dynamic analysis and seismic fragility analysis. The results of damage limit states (DLSs) determined by stochastic pushover curves indicated that the seismic capacity/DLSs for columns along the service life were time-dependent and followed lognormal distributions. The incremental dynamic analysis curves and seismic fragility curves implied that chloride-induced corrosion typically led to a substantial increase in the failure probability of columns. In comparison with the correlated stochastic method, considerable underestimations of component level fragility across different damage limit states were obtained using the deterministic approach, which highlighted the importance of accounting for the variability of mechanical properties of corroded steel bars in the time-dependent seismic fragility analysis.

Performance degradation of steel rebar considering corrosion spatial variability in concrete

The corrosion of steel bars is the main issue affecting the durability of reinforced concrete structures, which is nonuniform owing to the material properties and external environmental effects. In this study, the performance degradation of steel rebars in concrete is estimated considering corrosion spatial variability. With the aid of a three-dimensional measurement technique, a finite element model based on the scanning result was established to examine the corrosion effect on the tensile behaviour of the corroded bars, which was validated with the experimental results and digital image correlation observation. To assess the deformation behaviour of the corroded steels, a semi-analytical model was developed based on the cross-sectional area distribution and material properties. Subsequently, the spatial weight loss distributions with different degrees of corrosion were generated using a random field model. The model parameters were determined by combining engineering judgement and estimation of the experimental results. Finally, probabilistic model of degraded performance was established using the deterministic assessment and simulated steel weight loss distribution.

Application of wavelet transform techniques for corrosion assessment of embedded rebars in RC elements using electromechanical impedance

Corrosion of steel reinforcement embedded in concrete significantly influences the integrity and durability attributes of reinforced concrete structures. Monitoring of the early age corrosion of the reinforcements can contribute to an effective planning of structural maintenance and restoration. This paper demonstrates an innovative approach of monitoring the rate of corrosion (mass loss due to corrosion) of steel bars embedded in concrete by capturing conductance signature using Piezoelectric sensors (PZT) by Electromechanical Impedance Technique. In the recent times Wavelet Transform (WT) based different techniques have been proved to be promising techniques for different structural health monitoring assessment. This study aims to comprehensively use the WT techniques based on EMI signals to assess the corrosion levels in the reinforcement embedded in RC members. Specifically, the study focuses on capturing the progression of corrosion levels using the RMSD index derived from the DWT, CWT and WPT analysis of conductance signatures. WT techniques provides energy values of conductance signatures. Energy level of the signatures decreases with the increase of corrosion levels and deviation of energy level between current and pristine stage is measured using statistical index Root Mean Square Deviation (RMSD). Robust relationship between the RMSD index and the corrosion mass loss ratio through nonlinear curve fitting have been derived and presented using data captured from the 48 specimens of concrete cylinders with embedded reinforcement. At last, the comparison between the actual mass loss ratio and the predicted mass loss ratio derived from these techniques have been made for the validation of the proposed relation of predicted mass loss due to corrosion.

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Unification and calibration of steel corrosion models based on long-term natural corrosion

The corrosion of steel bars in concrete has a significant influence on the durability deterioration of reinforced concrete structures. The purpose of this study is to investigate the prediction models of steel corrosion rate and the main influencing factors in the case of natural corrosion. The experimental results are obtained from the long-term natural corrosion induced by accelerated chloride erosion. Then, based on electrochemical corrosion kinetics, Ohm’s law, and potential field theory, numerical models for uniform and local corrosion are established respectively, and compared with the experimental results. The main parameters and influencing factors are deeply analyzed through the numerical models. The main conclusions are as follows: (1) The cell model based on Ohm’s law can be well adapted to uniform corrosion, especially when the resistivity of concrete is the controlling factor. (2) Among the parameters of electrode polarization, the cathode Tafel slope has the greatest influence on the numerical results, followed by the anode equilibrium potential.

Tensile behaviour of pitting corroded steel bars: Laboratory investigation and probabilistic-based analysis

Localised corrosion in steel bars has been a long-standing issue in the durability of reinforced concrete structures, but a comprehensive scheme for the analysis of pitting corroded steel bars, especially with respect to the deformation capacity, is not currently available. In this study, the morphological characteristics of 27 pitting steel bars were captured using a 3D scanner. The measured data were used to establish the probability distribution model of the cross-sectional areas of the corroded bars. Uniaxial tensile tests were conducted, and the evolving deformation field of the corroded bars was recorded through Digital Image Correlation (DIC). Based on the 3D reconstructed model and DIC results, an analytical method for evaluating the mechanical properties of pitting steel bars was developed and validated. The results show that the two-component Gaussian mixture distribution model outperforms conventional unimodal distribution models. Comparison of the analytical results with experimental data demonstrates that the proposed procedure is capable of predicting not only the ultimate strength but also the gauge length-dependent ultimate strain of corroded bars. Additionally, there exists a strengthening effect in the ultimate stress at the critical sections and this effect should not be ignored for accurate predictions.

Insights on the chloride adsorption stability in cement mortar under current field and sulfate attack: From experiments to molecular dynamics simulation

The destabilization together with boundary chloride ions releasing leads to the corrosion of steel bars, posing nonnegligible risks to the durability of structures. This work attempted to design the typical pore solution of underground constructions via methods of combining NaCl with Na2SO4 along with conducting a stray current continuously. The bound chloride stability of mortar under the action of electric current was systematically determined. The reaction mechanisms were tested by quantitative XRD, TG-DTG, FTIR, FESEM, and X-CT. Molecular dynamics was utilized to simulate the physical binding processes of C–S–H of Cl−/SO42- and their interaction under the actions of electric field by comparing the ions displacement trajectory, radial distribution function, and moving ability. The experimental results showed that the SO42- weakened the chemical chloride binding capacity with the Friedel's salt, portlandite, and calcium silicate decomposed to produce gypsum or ettringite. The electric field demonstrated less impact on the stabilities of chemical-bound Cl−, but promoted SO42- redistributions, causing substantial pore coarsening. The simulation revealed that the physical binding contained short-range ion Coulomb-interactions and long-range van der Waals interactions. The SO42- inhibited the binding of the C–S–H on Cl− by fact that the deposition large cluster of Na–SO4 blocked the nano-meter channels and competitive adsorption occurred at the SiOCa+ sites, while the introduction of electric field weakened the dominating effects of Coulomb-interactions and improved the ions desorption gradually. Hopefully, the transport and adsorption mechanisms of the Cl− in the cement-based materials can help guide the underground concrete with durability.

Seismic performance of corroded prefabricated column-footing joint with grouted splice sleeve connection: Experiment and simulation

Steel corrosion is a critical factor in the seismic performance degradation of prefabricated concrete structures. In this study, the constant current accelerated corrosion method was employed to achieve targeted corrosion levels in steel bars within prefabricated column-footing joints connected by a grouted splice sleeve (GSS). Following that, a quasi-static cyclic experiment and numerical simulation method were employed to investigate the seismic performance of the specimens under various corrosion levels. Seismic performance indicators of specimens including the hysteresis curves, skeleton curves, bearing capacity, ductility coefficient, stiffness, and cumulative energy dissipation are examined. The results demonstrate that the failure modes of all column-footing joints are flexural failures. Specimens with steel bar corrosion levels below 14.1 % show negligible impact on the seismic performance. However, as the corrosion level increases, both the bearing capacity and cumulative energy dissipation capacity of the specimens significantly decrease. The horizontal displacement and ultimate displacement corresponding to the maximum bearing capacity are only 50.5 % and 45.2 %, respectively, compared to the non-corroded specimen. Additionally, a refined finite element model of prefabricated column-footing joints with GSS connections under different corrosion levels is developed and the hysteresis and skeleton curves obtained by numerical simulation are verified to be in good agreement with the experimental results. The numerical simulation outcomes regarding peak load and corresponding horizontal displacement maintain a relative error within 15 % compared to the experimental results.

A Review on Durability Analysis of FRP Bars based on Different Factors in Alkaline Environment

The primary issue with concrete structures is steel bar corrosion. Therefore, FRP (Fiber Reinforced Polymer) bars are often to substitute steel bars to tackle the issue of concrete swelling and cracking brought about by steel corrosion. FRP bars feature improved corrosion resistance, a stronger strength-to-quality ratio, and better fatigue resistance. However, the alkaline environment will affect the long-term strength and durability of FRP, according to certain research, which will cause the FRP bars mechanical characteristics to deteriorate. In this paper, the properties of FRP bars under alkaline conditions are reviewed, considering the harsh external environment and physical properties of FRP bars. Comprehensive investigation concludes that lowering the PH value of concrete and changing the kind of fiber material may considerably increase the endurance of FRP in alkaline environments. By demonstrating the microscopic breakdown process of FRP bars in an alkaline conditions using scanning electron microscopy. The Arrhenius acceleration theory was used to construct the present model for forecasting the long-term mechanical behavior of FRP bars, which shows how this material degrades under alkaline circumstances. This study may be utilized as a reference for FRP bars used in alkaline environments in terms of durability studies.

Nanoindentation analysis of corrosion products and induced expansion stress in reinforced concrete exposed to marine environments

Reinforced concretes are widely used in construction owing to their ultrahigh mechanical properties and long-term durability. However, the corrosion of steel bar within concrete poses a substantial threat to the structural integrity of buildings, impeding advancements in ocean engineering and necessitating expensive maintenance measures. In this study, the corrosion mechanisms of reinforced concrete under marine environments were investigated. The elastic modulus of corrosion products and the identification of rust compositions in different corrosive environments were comprehensively investigated using nano indentation technique and microscopic characterizations. The average young's modulus of rust products in chloride, sulfate, and chloride-sulfate composite solutions were measured to be 47.6 GPa, 37.59 GPa, and 61.52 GPa, respectively. And the analysis identified the presence of two distinct layers of rust product, providing valuable insights into the corrosion process. In addition, the real-time and in-situ monitor of corrosion expansion stress shows that the rust expansion stress generated in chloride solution was almost twice as high as that under sulfate solution and 1.3 times higher than that in the composite solution. The advanced wire beam electrode technique was employed to compare and analyze the different stages of depassivation, pitting corrosion and corrosion rate during the whole process. The corrosion process under chloride solution showed larger and more serious corrosion than under sulfate solution, with the anodic peak current spreading and reaching 4.00 μA cm-2 after 300 days. This work reveals valuable insights into the corrosion behaviour of reinforced concrete in three corrosive conditions and can be used to inform the development of strategies for corrosion prevention and mitigation.

Modelling of long-term performance of RC beams under coupling steel corrosion and bond deterioration

The steel-to-concrete bond deterioration due to corrosion in the reinforced concrete (RC) structures still needs more investigation because the existing models were established based on pull-out tests, which do not represent the real RC beams owing to the flexural cracks. This paper presents a new approach that discusses the bond deterioration of corroded steel bars embedded in RC beams. The study presents simulations for an experimental database of existing corroded RC beams from previous papers using a nonlinear finite element model. The simulated specimens were divided into two categories: accelerated and long-term (after 14,23, and 28 years) corroded beams to identify the key corrosion parameters in these two conditions. The results indicated that the behavior of the RC beams, which corroded via the accelerated method, failed by concrete crushing after steel yielding, and it could be simulated considering the reduction of both steel area and bond strength only. On the other hand, the spalling pressure is a key parameter to simulate the long-term corroded RC beams because it controls the ultimate deflection, and the failure is governed by concrete cover spalling due to concrete deterioration. As an innovative result, a novel bond-slip model was proposed to predict bond deterioration due to corrosion in the RC beams, and it showed excellent accuracy compared to the existing models.

Effect of Adding Styrene-Butadiene Rubber (SBR) on Corrosion Resistance for Reinforced Concrete Columns

Corrosion in steel bars has the biggest effect on the concrete strength as well as its durability. Problems, such as increasing the crack widths, deflections, increasing stresses and decreasing concrete strength, are some subsequences of steel corrosion. Therefore, preventing these undesirable consequences, needs to address by researchers. Some additive materials which can be used in concrete might be the most effective cheap solution. In this research, Styrene Butadiene Rubber (SBR) was utilized in the concrete mixture to reduce water permeability in concrete. In order to test the effect of SBR on steel corrosion in structural members, seven reinforced concrete columns of circular cross section were casted with different contents of SBR, from one percent to six percent of water content. Using accelerated corrosion cells, major tests were done after twenty days. Results show that SBR improved the compressive strength of the concrete up to thirty – one percent with using one percent of SBR. Moreover, the compression strength of the reinforced concrete columns increased about thirty – two percent with using six percent of SBR. Not only the concrete strength improved with adding SBR, but also the steel corrosion resistance increased and steel weight losing decreased.