Rebar Corrosion In Concrete Research Articles

A New Avrami-Based Exponential Model for Predicting Fiber-Reinforced Polymer Bar Service Life: A Comparison with Existing Models Using a Large Database.

The fiber-reinforced polymers (FRP) bar is a promising solution to problems caused by steel rebar corrosion in concrete. To assess the service life of the FRP bar based on accelerated test results, it is crucial to have a reliable model. Here, a modified exponential (MEP) model is proposed based on the Avrami equation. The Avrami equation provides a theoretical foundation for the empirical exponential (EP) model and does not a priori fix the power of the exposure time to one. A database containing 903 data points from 74 groups of test specimens is assembled to compare the reliability of the MEP model vis-a-vis the EP, single logarithmic, double logarithmic, and power function models. The combination of Root Mean Square Error (RMSE), the Mean Absolute Error (MAE), and the coefficient of determination (R2) criteria is proposed for assessing model reliability. It is shown that in certain cases the combined criteria, versus R2 alone, significantly increase the number of test groups meeting the acceptable performance limit. Observed test data aberrations are found to have minor influence on the results of the EP model, but they significantly influence the results of the other four models. The EP model generally predicts the lowest activation energy and the smallest strength retention for similar groups of bars, while the predicted values of the other four models exhibit a relatively small difference. The difference between the predicted strength retention values of the EP and MEP models shows an increasing trend with the increase of the absolute value of (1 - n), where n is the power of the exposure time in the MEP model.

Study Of The Impact Of Several Coatings In Minimizing The Rebar Corrosion In Concrete

This paper represents experimental study to examine the influence of several coatings to decrease the rebar corrosion. The experiments were carried out for three types of coatings. Those have been painted on the steel and select the best type of coatings in decreasing the steel corrosion rate. Testing program included experiments to select the best one within three types of coatings (Isonem MS Polymers, Sika Zink Rich-1, Isonem PU Floor) are used and available in market. The result of corrosion rate for rebar in uncoated samples in level five (after 70 days) was loss of more than 50% from its weight. While, the result of corrosion rate for rebar in samples with coating type (C) ”Isonem PU Floor” was loss of less than 2% from its weight which is the most effective type and the best coating.

Deep learning-based extraction and quantification of features in XCT images of steel corrosion in concrete

The corrosion of rebars in concrete has been regarded as one of the most predominant factors for the degradation of reinforced concrete (RC) structures. The accurate predictions of corrosion damages are the basis for the safety assessment of in-service RC structures and the enhancement of new structure designs. X-ray computed tomography (XCT), known for its non-destructive capabilities, has been widely utilized to understand the corrosion process inside the concrete, offering three-dimensional (3D) visualization and aiding in the identification of the parameters in the predictive model of steel corrosion. This study uses U-Net, a deep learning network, to detect various phases of steel corrosion evolution in concrete, including the identification of rebar, corrosion products, pores, cement mortar, and corrosion-induced cracking. A galvanostatic accelerated corrosion test was conducted to simulate rebar corrosion within the mortar. The XCT test was performed, producing a series of XCT images that revealed the corrosion-induced cracks in the concrete. This set of images formed a comprehensive training database for the U-Net model. The performance of the model was significantly improved by data augmentation within the training dataset, thereby enabling it to recognize corrosion-induced cracking and pores. The U-Net model proved effective in accurately segmenting the XCT images into different phases, demonstrating a high accuracy rate of 99.18% on the validation dataset. A mean Intersection over Union (IoU) of 82.1% and a mean F1 score of 89.1% are observed on the test dataset, showing superior segmentation performance on XCT images. This significant advancement has automated the process of visualizing and 3D reconstructing the steel corrosion process inside the concrete. Concurrently, it has enabled the quantification of the volumetric expansion coefficient of corrosion products. The findings reveal spatial and temporal variations in this coefficient due to the migration of the corrosion product through the cracks.

Detection of the Rebar Corrosion in Concrete Using a New IOT-Based Device Constructed by the Solid-Phase Electrodes and Pressure Sensors

Detection of the Rebar Corrosion in Concrete Using a New IOT-Based Device Constructed by the Solid-Phase Electrodes and Pressure Sensors

Inhibition Mechanism of Oxalhydrazide on Reinforcing Steel in Pore Solution Contaminated by 3.5%NaCl - Experimental and Theoretical Study

Concrete is one among the most consumed materials on the planet secondary to water. However, the degradation of concrete happens due to the corrosion of reinforcement. Although the pore solution of concrete is alkaline, the corrosion of rebars in concrete is triggered due to aggressive ions like chlorides entering the concrete. The most common method of corrosion inhibition is by utilising corrosion inhibitors which when added to the concrete stays in the pore solution and prevents the corrosion of surface of rebars from aggressive ions. Although there are number of inhibitors, the rise in corrosion deterioration demands the need for new potential inhibitors which are highly effective in different aggressive environments. This study is based on the corrosion of rebars in simulated concrete pore solution in the presence of 3.5% NaCl with oxalhydrazide as the potential inhibiting material. The corrosion behaviour of rebar is obtained by electrochemical studies using EIS and potentiodynamic polarization and theoretically analysed employing molecular mechanics and molecular dynamics simulations. The experimental results revealed that the inhibitor is effective in reducing the corrosion and the values of binding energy of the inhibitors on rebar surface also go well with the experimental results. Oxalhydrazide is found effective in minimizing the attack of chloride ion on rebar in pore solution.

Studies on corrosion monitoring of reinforced concrete in a chloride environment using an embedded solid-state reference electrode

In the present study, the corrosion status of steel rebars embedded in concrete with various cover thicknesses and exposed to conditions simulating a marine environment (3.5 % NaCl) was monitored by an embedded solid-state reference electrode (ESSRE). Electrochemical impedance spectroscopy (EIS) results confirm that corrosion initiation of the steel rebars occurred at 702, 1144, 1469 and 2454 h for C10, C15, C20 and C30 concrete specimens, respectively. Further, the relationship between the free and bound chlorides for C15, C20 and C30 specimens were defined by Temkin isotherm. In addition, the time to crack initiation was predicted by the El Maaddawy model. This study has successfully demonstrated that the solid-state MnO2 electrode is reliable for monitoring the onset of steel rebar corrosion in concrete by a non-destructive method.

Phenomenological process of rebar corrosion in reinforced concrete evaluated by acoustic emission and electrochemical noise

Rebar corrosion was evaluated by monitoring reinforced concrete specimens. An electrical corrosion test accelerated the corrosion, and non-destructive evaluation of the acoustic emission (AE) and electrochemical noise (EN) was applied. Because AE phenomena were detected during rebar corrosion, the rise time and maximum amplitude increased, showing waveform variations. The AE activity was attributed to oxide film peeling of the rebar surface. The pitting index of the EN analysis ranged from –1 to 0, indicating localized corrosion. The EN method can detect pitting corrosion on rebar surfaces. AE and EN can be combined to phenomenologically evaluate early-stage rebar corrosion in concrete.

Nondestructive Evaluation of Localized Rebar Corrosion in Concrete Using Vibro-Radar Based on Pulse Doppler Imaging

Early nondestructive inspection of rebar corrosion in reinforced concrete structures is important, but a practical, accurate, high-speed, and high-resolution method has not yet been proposed. We have proposed a vibro-Doppler radar (VDR) method for quantitative evaluation of rebar corrosion based on vibration displacement of a rebar sinusoidally vibrated by an excitation coil. However, this method is not practical because it is not quick enough, requiring two minutes for a measurement at one point. In this paper, a VDR system based on a pulse radar, which is 100 times faster than the conventional system, was developed, and its effectiveness was verified using a concrete specimen. As a result, it was found that a 30-cm section could be scanned in about 2 min. Furthermore, the vibration displacements spatially distributed on the rebar were monitored while the rebar was corroded by electrolytic corrosion tests. As a result, it was found that the vibration displacement increased locally with a width of a few centimeters, and their positions corresponded to the positions of sectional loss of rebar due to corrosion, indicating that this method can be used for nondestructive evaluation of localized rebar corrosion.

Evaluation of Preventative Methods against Rebar Corrosion in Concrete

Prevention of rebar corrosion is achieved in the design and construction phases, by means of suitable mix design, casting and curing, and adequate cover depth; this approach have been introduced in international standards (EN 206) and design codes (Eurocode 2). Additional protection methods (cathodic protection, stainless steel or galvanised rebars, corrosion inhibitors, concrete coatings) can be used in very aggressive environment, especially in presence of chlorides, or when increased service life is required. In this work a simplified performance-based approach, based on Monte Carlo simulation, has been used to evaluate the service life (initiation time of corrosion) in chloride containing environments. The results confirmed that cathodic prevention and stainless steels are the most effective protection methods to guarantee a safe working condition in a severe environment. The use of pozzolanic or slag cement is confirmed as an effective way to slow chloride transport and by this way to increase the service life.

Detection of early-stage rebar corrosion using a polarimetric ground penetrating radar system

As a non-destructive testing method, ground penetrating radar (GPR) has been applied to monitor the corrosion of reinforced bar (rebar) in concrete. However, a traditional GPR system employs a pair of antennas, and can only measure single-polarization radar signals. In this paper, a hybrid-polarization GPR system is proposed for detection and evaluation of rebar corrosion. It can record rebar reflections in two orthogonal polarimetric channels, from which a full-polarimetric scattering matrix can be estimated through polarimetric decomposition and calibration. An accelerated corrosion experiment was conducted and the results prove that radar signal in the polarization channel perpendicular to the rebar orientation is more sensitive to the corrosion, compared with the commonly-used parallel polarization channel. Analysis of the scattering mechanism through H-Alpha decomposition shows that the corroded rebar shifts from the low-entropy dipole scattering to the low-entropy surface scattering. By filling the migrated GPR image with the color of the H-Alpha scattering classification, it is able to visually evaluate the early-stage corrosion of rebar in concrete.

Corrosion of rebar in concrete. Part IV. On the theoretical basis of the chloride threshold

A theory is developed for calculating the chloride threshold (CT) from the Point Defect Model (PDM). CT is defined as the ratio [Cl−]/[OH−] at which the passivity breakdown voltage (Eb) equals the corrosion potential, ECP. CT is sensitive to the T, ECP, pH, and Eb, because all four appear in the exponent X in CT = 10X. Small uncertainties in these parameters translate into a large uncertainty in CT, emphasizing the need for accurate T, ECP, pH, and Eb data. We demonstrate the theory by successfully calculating CT using data for selected systems.

Non-Destructive and Quantitative Evaluation of Rebar Corrosion by a Vibro-Doppler Radar Method.

It is well known that evaluation of rebar corrosion is important for the maintenance of reinforced concrete structures, but, it is difficult to simply, quickly and quantitatively evaluate the amount of corrosion of rebars embedded in concrete by conventional non-destructive evaluation (NDE) methods such as electrical, electromagnetic and mechanical method. This paper proposes a vibro-Doppler radar (VDR) measurement method to quantitatively evaluate rebar corrosion by measuring the vibration ability of the rebar forcibly vibrated in concrete by an excitation coil. It is experimentally demonstrated in RC test pieces that the rebar vibration displacement obtained by developed VDR method is valid and is less affected by the moisture in the concrete. In addition, simultaneous monitoring of the rebar vibration displacement of the test pieces is performed through an electrolytic corrosion test and the measured vibration displacement is compared to the rebar corrosion loss evaluated. As the results, it is cleared that the rebar vibration displacement starts to increase from slightly before the occurrences of corrosion crack on the concrete surface as the corrosion loss increases. It is also shown that the rebar vibration displacement becomes 4 times higher than that in initial condition at the rebar corrosion loss of 250 mg/cm2. This implies that the VDR has potential to nondestructively and quantitatively evaluate rebar corrosion in concrete.

Corrosion of rebar in concrete. Part III: Artificial Neural Network analysis of chloride threshold data

Active corrosion of carbon steel in reinforced concrete occurs when the chloride ion concentration exceeds the chloride threshold (CT). CT is affected by many physical and chemical parameters including primary variables (pH, corrosion potential, breakdown potential, and temperature) and secondary variables (cemenet composition, concreete porosity, and water/cement ratio). A Kohonen-self organized map (KSOM) and regression artificial neural network (ANN) coupled methodology was developed to find the missing values of independent variables in the sparse database and for quantitatively evaluating the effects of these variables on CT values that are expressed in %TotalCl/cem (or %FreeCl/cem), and [Cl−]/[OH−].

Corrosion of rebar in concrete. Part II: Literature survey and statistical analysis of existing data on chloride threshold

The literature is reviewed with respect to defining, measuring, and interpreting the chloride threshold (CT). CT was defined with a strong fundamental basis in the Point Defect Model. which also dictates the nature of the statistical analysis of surveyed CT values. A database of CT for various primary and secondary independent variables has been established. Statistical analyses reveal that CT is lognormally distributed, in accordance with the PDM, with most probable values being 0.85, 0.69, and 1.19 for %total Cl/cem, %free Cl/cem, and [Cl−]/[OH−], respectively. The breakdown and corrosion potentials follow normal distributions with means of 0.056 and -0.322 VSCE, respectively.

Corrosion of rebar in concrete. Part I: Calculation of the corrosion potential in the passive state

Knowledge of the corrosion potential (ECP) in the passive condition is important in assessing corrosion in reinforced concrete structures. While ECP is routinely measured, great scatter is reported, because the ECP is a sensitive function of many variables (T, [O2], pH, [Cl−], and the poorly defined mass transfer conditions). In this paper, a Mixed Potential Model (MPM) is used to calculate the ECP. The ECP shifts sharply in the negative direction when the passive current exceeds the limiting current density for oxygen transport to the steel surface. This shift is frequently misinterpreted as indicating passivity breakdown of the steel only.

Influence of bauxite residue (red mud) on corrosion of rebar in concrete

This paper examines the corrosion of rebar embedded in concrete when cement is partially replaced with toxic bauxite residues, known as red mud (RM). The concrete mixtures were made with 100% ordinary Portland cement (OPC), and OPC replaced with 5% of RM (95% OPC + 5% RM). In order to evaluate the rebar corrosion in aforesaid concrete mixes, 5% calcium chloride was admixed while preparing the concrete. The corrosion performance of rebar in OPC concrete and concrete blended with RM was monitored by corrosion potential and linear polarization resistance. In addition, the performance of concrete blended with RM is evaluated through IR (Ohmic drop) compensated electrical resistivity. After 420 days of corrosion monitoring, concrete samples were broken, and visual observations were made on the rebar. X-ray powder diffraction analysis is also carried out on concrete powder samples collected from the steel–concrete interface. The experimental results have shown that the RM blended concrete performed better to resist the corrosion of rebar as compared to OPC concrete across the testing period of 420 days in the case of concrete made of w/cm 0.48. However, the overall corrosion current density increased in RM blended concrete as compared to normal concrete for the w/cm 0.51.

Corrosion of Rebar in Concrete Using Seawater as Mixing Water

Corrosion of Rebar in Concrete Using Seawater as Mixing Water

The influence of some solution candidate on the performance of boundary element inverse analysis in detecting rebar corrosion

The purpose of this research is to study the effect of some solution candidate to the performance of boundary element inverse analysis (BEIA) that utilized for detecting corrosion of reinforcing steel/rebar in concrete. BEIA was developed by combining the boundary element method (BEM) and particle swarm optimization (PSO). BEM was used to calculate the electrical potential on the whole domain of reinforced concrete. While PSO was to optimize cost function to detect the rebar corrosion in concrete. BEIA was applied by using several measured electrical potential data as a reference such as from half-cell potential measurement. Numerical simulation on reinforced concrete with single rebar show that the increase of some solution candidate would resulting in increasing the number of iterations for the solution become convergence. However, the average error from the actual solution would be smaller by increasing solution candidate number. Therefore, the number of solution candidate affect the performance of BEIA in detecting rebar corrosion in concrete.

Effect of sodium molybdate and sodium tungstate in concrete rebar corrosion

PurposeThis paper aims to identify an inhibitor to protect rebar corrosion in concrete.Design/methodology/approachThe authors use the simple method of polarization and calculate the change in open-circuit potential and corrosion current density.FindingsSodium molybdate is an efficient inhibitor compared with sodium tungstate for rebar corrosion in concrete.Research limitations/implicationsThis paper has limitation of 0.0001 M concentration of inhibitors for 400 days of exposure in 3.5 per cent sodium chloride solution.Originality/valueThe research focused on the concentration of both inhibitors in the range from 0.1 to 0.0001 M, which resulted in greater structural protection from corrosion in adverse conditions, such as coastal areas.

Effect of binary mixtures on chloride induced corrosion of rebars in concrete

Effect of binary mixtures on chloride induced corrosion of rebars in concrete