Corrosion Rate Of Reinforcing Steel Research Articles

Evaluation of the Corrosion Activity of Reinforcement in Drainage Gallery of Concrete Dam using Half-cell Potential (HCP)

Dams are essential structures for water management, providing various benefits crucial for human survival and economic growth. However, steel corrosion in concrete dams poses a significant threat, leading to structural deterioration and potential collapse. Detecting corrosion in the early stage is critical to prevent catastrophic failures. This study investigates corrosion risk in a concrete dam's drainage gallery using half-cell potential (HCP) measurements, a common method for assessing corrosion activity in reinforced concrete. The electrochemical process of steel corrosion in concrete, influenced by factors like chloride or carbonation exposure and temperature, is discussed. The HCP method is a nondestructive technique for determining the corrosion rate of steel reinforcement in concrete structures. It involves measuring the potential difference between reinforcing steel and reference electrodes; typically, a copper/copper sulphate electrode is used. The potential difference between the two electrodes is then used to calculate the corrosion rate of the reinforcing steel. The HCP method is a reliable and cost-effective way to identify potential corrosion problems before they become severe. The present study used CorMap II® to measure HCP on the upstream face of the dam's drainage galleries. Results indicate predominantly low corrosion risk across tested locations, with minimal uncertainty. However, interpretations must consider environmental factors' influence on measurements. The study's findings offer valuable insights for future corrosion assessments and underline the importance of preventive measures for concrete dam integrity.

On-line monitoring the corrosion rate of reinforcing steel in concrete under natural conditions using bimetallic batch sensors along the coast of Khanh Hoa (Vietnam)

A bimetallic batch sensor was proposed to assess the corrosion rate of steel reinforcement in concrete in the presence of chlorides under laboratory and marine conditions. The prepared sensor could generate an electric current independently, indicating the corrosion process's intensity. Moreover, this sensor did not require any external polarization, resulting in reducing the device's cost and power consumption. These advantages are very important when using sensors for autonomous monitoring systems away from energy sources. Laboratory tests in an aqueous extract of concrete have shown the possibility of a sensor to detect the transition from a passive state to corrosion with an increase in the concentration of chlorides. Activation was received when 0.010 < CCl ≤ 0.10 mol·dm−3. The boundary between the passive state and corrosion was obtained at a current density of 8.6 ± 0.5 μA·cm−2. The measurement results on the sensor coincided with the data of the anode polarization curves and the polarization resistance method. In addition, the monitoring system based on sensors was tested in the field conditions of Khanh Hoa (Vietnam) for four exposure conditions for nine months. The correspondence of the measured current for sensors with standard monitoring methods was obtained: the half-cell potential and the electrical resistivity. The most intense corrosion occurred for the samples placed in the splash zone or immersed to a depth of 1 m. The coefficient of conversion of the current on the sensor and the corrosion rate by the polarization resistance method for concrete samples was set to 69.9. Therefore, it is possible to use the current value on the sensor to predict the time to structural failure using well-known models based on data on the corrosion rate of reinforcement. The sensors could retain their functionality and integrity after 9 months of field tests. The current findings suggest a continuous monitoring system of the corrosion rate of steel reinforcement in marine conditions for practical applications.

Nghiên cứu chế tạo cảm biến điện hóa galvanic giám sát trạng thái ăn mòn cốt thép trong môi trường xâm thực bởi ion clorua

This paper presents the results of a study on the corrosion of steel reinforcement in concrete pore solutions contaminated with chloride ions. With increasing chloride concentration, the open-circuit potential and the anodic polarization curve shift towards more negative potential values, the passive potential region of the anodic polarization curve decreases. The corrosion rate of reinforcement was evaluated according to the linear polarisation resistance technique. Accordingly, the corrosion rate of steel reinforcement is 4.53 µA/cm2 in the solution containing 1 M Cl-. In this study, galvanic electrochemical sensors with low carbon steel anodes and copper cathodes were developed. In an environment with no or low Cl- concentration, where the reinforcement is passivated, the corrosion current density of the sensor does not exceed 10.0 µA/cm2. The corrosion current of the sensor increases sharply under cathodic control with increasing chloride content. Thus, the developed sensor has a high sensitivity to chloride corrosion and is capable of detecting pitting corrosion caused by chlorides at an early stage.

Chloride induced corrosion of steel reinforcement in alkali activated slag concretes: A critical review

Alkali activated materials (AAMs) have been recognised as potential alternatives to Portland cement concretes in specific applications in the construction industry due to their environmental benefits such as substantially reduced CO2 emissions and utilisation of industrial wastes. While many studies reported the superior performance of AAM concretes over Portland cement concretes in protecting steel from corrosion, some other studies indicated an opposite view. Hence, there is a need for further research on the long-term corrosion studies of AAM concretes in the laboratory as well as in the field. Among many important areas of investigation is the resistance of AAMs to chloride induced corrosion of steel reinforcement which is not well understood. In this paper, the above aspect is reviewed including chloride ingress, chloride binding and chloride induced corrosion rate of steel reinforcement in AAMs. Chloride ingress in AAMs involves both open and closed pore systems. Chloride binding in AAMs is predominantly physical and not chemical. The chloride threshold levels initiating steel corrosion in AAMs are significantly different in comparison to Portland cement concretes.

Effect of Corrosion Inhibitors Admixtures on Corrosion Rate of Steel Reinforcement in Concrete (Dept.C)

Reinforcement corrosion is the main cause of damage and early failure of reinforced concrete structures. The protection system of embedded steel reinforcement from chloride induced corrosion involves several methods and techniques. One of these methods and techniques is using corrosion inhibitors admixtures (CIA) which added to concrete mix during mixing stage of concrete. These research aims to evaluate these admixtures (Sika Ferrogard®-901) in prevent corrosion of steel in concrete and their effect on concrete properties for fresh and hardened concrete. In this paper (CIA) used with different concrete contents and proportions. In this study, 150-mm concrete cubes specimens with high tensile steel bar grade (36/52) of 10 mm in diameter and 150 mm in length were embedded in each specimen during its casting such that 100 mm was fixed inside the concrete while the reminder 50 mm was kept outside. Three thicknesses of concrete cover were used; 25, 50 and 75 mm. After 28 days of water curing, specimens were transferred to dry for 24 hour, then the specimens were partially submerged in plastic tank filled with 6% NaCl solution Acceleration of corrosion rate test is achieved by continuous electrical current produced from power supply 30 volts for 240 hour, where volts difference was measured in volts between resistance 100 ohm and the reading was record every 12 hour. The corrosion current (Icon in Ampere) was calculated during the accelerated corrosion regime by using ohm's law by knowing measured volts difference and resistance. Faraday's law describes the relationship between section loss and corrosion current. Hence, calculate corrosion rate of steel reinforcement in concrete. The results show that for all mixes the increasing of concrete cover thickness reduces the corrosion rate of steel. Using 5% (CIA) by weight of cement where the optimum dosage of Corrosion inhibitors admixture from experimental tests is 5% by weight of cement reduce corrosion rate by 80 % with no side effect on concrete properties except bond strength decreased by 10%.(CIA) gave best results with concrete mixes which contains 15% silica fume and water to cement ratio 0.35 · (CIA) decreasing concrete cover required to prevent corrosion from 75 mm to 50 mm. (CIA) accelerate setting time of concrete, so it needs a retarded when used with concrete mixes.

Productivity Performance Estimation in Egyptian Construction Projects Based on Regression Analysis (Dept.C)

Reinforcement corrosion is the main cause of damage and early failure of reinforced concrete structures. The protection system of embedded steel reinforcement from chloride induced corrosion involves several methods and techniques. One of these methods and techniques is using corrosion inhibitors admixtures (CIA) which added to concrete mix during mixing stage of concrete. These research aims to evaluate these admixtures (Sika Ferrogard®-901) in prevent corrosion of steel in concrete and their effect on concrete properties for fresh and hardened concrete. In this paper (CIA) used with different concrete contents and proportions. In this study, 150-mm concrete cubes specimens with high tensile steel bar grade (36/52) of 10 mm in diameter and 150 mm in length were embedded in each specimen during its casting such that 100 mm was fixed inside the concrete while the reminder 50 mm was kept outside. Three thicknesses of concrete cover were used; 25, 50 and 75 mm. After 28 days of water curing, specimens were transferred to dry for 24 hour, then the specimens were partially submerged in plastic tank filled with 6% NaCl solution Acceleration of corrosion rate test is achieved by continuous electrical current produced from power supply 30 volts for 240 hour, where volts difference was measured in volts between resistance 100 ohm and the reading was record every 12 hour. The corrosion current (Icon in Ampere) was calculated during the accelerated corrosion regime by using ohm's law by knowing measured volts difference and resistance. Faraday's law describes the relationship between section loss and corrosion current. Hence, calculate corrosion rate of steel reinforcement in concrete. The results show that for all mixes the increasing of concrete cover thickness reduces the corrosion rate of steel. Using 5% (CIA) by weight of cement where the optimum dosage of Corrosion inhibitors admixture from experimental tests is 5% by weight of cement reduce corrosion rate by 80 % with no side effect on concrete properties except bond strength decreased by 10%.(CIA) gave best results with concrete mixes which contains 15% silica fume and water to cement ratio 0.35 · (CIA) decreasing concrete cover required to prevent corrosion from 75 mm to 50 mm. (CIA) accelerate setting time of concrete, so it needs a retarded when used with concrete mixes.

Analysis of the corrosion behavior of steel reinforcement protected by phosphate coatings

The influence of phosphate coatings on the corrosion behavior of steel reinforcement in a chloride-containing environment was studied to determine the need for additional protection against corrosion. The main indicators of the corrosion rate of steel reinforcement with phosphate coatings in chloride-containing solutions were determined, confirming the high protective properties of these coatings. It was found that the corrosion rate of steel reinforcement protected by phosphate coatings is reduced by 3 times. The processes of electrochemical corrosion of steel reinforcement of strength class A500S from steel grade St3ps in concrete under the influence of aggressive environments containing chloride ions (2 % MgCl2 solution and HCl solution with pH = 5) were studied. The kinetics of the corrosion process of steel reinforcement with and without protective phosphate coatings in solutions of various compositions has been studied. The change in mass of steel reinforcement protected by phosphate coatings is 3-4 times less than that of samples without coating. The surface potential of steel reinforcement with phosphate films changes significantly more slowly than that of unprotected samples.

Effect of nano-silica and nano-waste material on durability and corrosion rate of steel reinforcement embedded in high-performance concrete

The corrosion rate of reinforcing steel present in high-performance concrete (HPC) was examined in the presence of nano fly ash, nano-silica fume, and nano coal as nano-waste material (NFA, SF, NC), respectively. A replacement to ordinary Portland cement (OPC) was carried out to some extent with nano-waste materials at 1, 2, 3, 4, 5, and 6% by cement weight to yield the (NFA, NSF, NC) HPC, as well as different percentages of NS (1, 2, 3 and 4%) were used. The corrosion rate of reinforcing steel present in HPC and nano-silica- and nano-waste materials-HPC was monitored and estimated using the half-cell potential (HCP). In addition to, water permeability, water absorption and aggressive attack media (immersed in sewage water) of hardened HPC and nano-silica- and nano-waste materials-HPC were also studied. All the samples of steel reinforcement were immersed in Qaron’s Lake water up to 6 months of exposure. The lowest corrosion rate results, compared with ordinary HPC, were obtained when nano-silica and nano-waste materials were used in concentrations 3,4, 4 and 2% (NS, NFA, NSF, and NC), respectively. Furthermore, HPC implanted with nano-silica (NS) is slightly better results than NFA. From the obtained data, the replacement with NFA gives the best milled waste material compared to NSF and NC, which improve the durability of nano fly ash-HPC.

Numerical model for corrosion rate of steel reinforcement in cracked reinforced concrete structure

The presence of cracks in concrete will accelerate the corrosion of steel reinforcement causing the performance degradation of reinforced concrete (RC) structure. Based on the electrochemical principle, a numerical model of macro-cell corrosion has been developed to predict the corrosion rate of steel reinforcement in cracked RC members. In this model, the areas of the separate anode and cathode are established by the crack width, and the electric resistivity of concrete material is modified by considering the effects of water-binder ratio and other factors. When the corrosion rate of steel reinforcement is taken as the mean value of the corrosion current density of anode zone, the corrosion rate can then be numerically solved from the proposed model with given boundary conditions. Test data from the 2-year laboratory experiments of authors and literature has been collected to verify the proposed model. The comparisons between the test and prediction results show that the proposed model is of capability to predict the corrosion rate with a good accuracy. Finally, the parametric studies show that the crack width, water/cement ratio, chloride concentration, thickness of concrete cover, and relative humidity has significant influences on the corrosion rate of reinforcement in cracked RC structure.

Corrosion of steel in concrete due to one and two dimensional chloride ingress

This paper presents results of an ongoing research of the effect of 1D and 2D chloride ingress on concrete resistivity and corrosion rate of steel reinforcement. 12 concrete beams made with concrete of binder blend PC(50)/GGBS(50), w/b = 0.40, 10 mm steel reinforcement rods at concrete cover of 20 mm were used in this laboratory based experiment. The steel reinforcement bars were placed at the middle or at an orthogonal corner of the concrete beams subjected to 1D and 2D chloride ingress respectively. A single crack was induced using 3-point bending on one-half of the beams. The beams were exposed to a repeated cycle of 2 weeks ponding in 5% NaCl and then air drying in ambient laboratory condition for 2 weeks. The corrosion rate of both cracked and uncracked specimens exposed to 2D chloride ingress was significantly higher than that of beams exposed to 1D chloride ingress. The uncracked specimens had lower concrete resistivity values compared to the cracked specimens even though higher corrosion rates were measured.

Improved numerical model for steel reinforcement corrosion in concrete considering influences of temperature and relative humidity

An improved numerical model for steel reinforcement corrosion in concrete was developed to investigate the influences of temperature and relative humidity on process control and corrosion rate of steel reinforcement in concrete. In order to overcome the limitations of current numerical corrosion models which oversimplify the activation overpotential, the influences of both forward and reverse electrode reactions on the activation overpotential were considered based on the original formulation of the Butler-Volmer equation. Meanwhile, the influences of temperature and relative humidity on the kinetic parameters of corrosion and the properties of concrete pore solution were considered simultaneously. Moreover, the applicability and efficiency of the proposed numerical model for steel reinforcement corrosion were verified by comparing with current empirical prediction models as well as available experimental data of both artificially accelerated and natural exposure corrosion tests. Finally, the influences of temperature and relative humidity on process control and corrosion rate of steel reinforcement in concrete were investigated comprehensively. Furthermore, the influences of temperature, water-to-cement ratio, concrete cover depth, and chloride content on the critical relative humidity were also discussed.

Effect of Na3PO4 inhibitor on chloride diffusion in mortar

The penetration of chloride ions by diffusion has become among the most important factors that lead to concrete reinforcement deterioration. To solve the corrosion problem and achieve the expected service life of reinforced concrete structures, many procedures can be employed such as the use of corrosion inhibitors. In this paper a phosphate based inhibitor (Na3PO4·12H2O) has been used to study its effectiveness against corrosion and its influence on chloride ions diffusion. This study has been conducted in steady-state conditions using a specific diffusion cell. This simple and effective technique was complemented by the use of a non-destructive method for measuring the concentrations of free chloride ions, diffused through the mortar containing or not phosphate inhibitor, which is the specific chloride electrode (ORION 96-17). The Inhibitor effect, the period and the chloride corrosion threshold of steel reinforcement has been followed using electrochemical techniques. Characterization methods were employed in order to study the behavior of the mortar in absence and presence of phosphate inhibitor. From these methods, it was possible to calculate the evolution of chloride diffusivity over the whole range of chloride concentrations. Results show that the addition of phosphate inhibitor in mortar can reduce significantly the corrosion rate of steel reinforcement in chloride solution, and also increases the critical period of pitting initiation from 30 to 100days. In these conditions, the calculated chloride diffusion coefficient was estimated at 0.103×10−11m2/s, value obviously lower than that obtained in the case of the mortar without inhibitor (0.22×10−11m2/s), during the same period. Thus it can be concluded that the presence of this phosphate inhibitor in mortar reduces the chloride diffusion rate.

Probabilistic evaluation method for corrosion risk of steel reinforcement based on concrete resistivity

In order to overcome the disadvantages of traditional deterministic methods, a probabilistic evaluation method to assess the corrosion risk of steel reinforcement in concrete was proposed based on the probabilistic prediction model of concrete resistivity. The influences of major influential factors including water-to-cement ratio, chloride content, ambient temperature and ambient relative humidity on concrete resistivity were investigated first. Then a probabilistic prediction model of concrete resistivity in terms of the above major influential factors was developed by using the Bayesian theory and the Markov Chain Monte Carlo (MCMC) method. Meanwhile, the evaluation criterion for corrosion risk of steel reinforcement based on concrete resistivity was proposed according to the relationship between concrete resistivity and corrosion rate of steel reinforcement. Finally, a probabilistic evaluation method for corrosion risk of steel reinforcement in concrete was developed by means of the proposed probabilistic prediction model of concrete resistivity. Analysis results show that the proposed probabilistic evaluation method can not only identify the dominant risk of reinforcement corrosion, but also determine the probabilities of steel reinforcement under different corrosion risk levels (e.g. negligible, low, moderate, and high), which could avoid the misjudgment of corrosion risk of steel reinforcement often encountered by the traditional deterministic evaluation methods.

Prediction of Steel Corrosion in Porous Building Materials by Means of a New Hygrothermal Model

Decay of ancient buildings is often due to corrosion of metallic reinforcements, which are embedded in the construction in order to improve its structural behaviour or to prevent the propagation of cracks. If wet conditions occur on the surface of steel, corrosion can start. Corrosion may weaken reinforcements and produce expanding oxides that lead to the detachment of covering materials, thus being harmful for the durability of the construction and challenging for its restoration. When dealing with heritage buildings, however, the problem becomes even more complex due to the need of non-invasive and reversible techniques. Here the only possibility is often to limit the corrosion rate by controlling moisture and temperature conditions in the assembly or the indoor climate. To this end, a method has been developed which focuses on the corrosion behaviour of steel reinforcements in constructions, considering the complex transient processes of corrosion chemistry and the local hygrothermal conditions. In particular, the model is based on the correlation between the transient hygrothermal conditions (i.e. temperature, relative humidity and water content) and the corrosion rate of steel reinforcements embedded in porous building materials i.e. mortars and bricks. It allows the prediction of the temperature and humidity dependent corrosion rate of the steel over time. The model has been validated through several laboratory tests, showing a good agreement between measured and simulated results. It assesses the corrosion risk depending on parameters which are easy to monitor and allows both preventive conservation/restoration of cultural heritage buildings and safe design of new durable building components. Concerning the former point, the model permits state-of-preservation assessments when material sampling is not possible and enables to define measures to reduce/stop corrosion of steel reinforcements.

Modeling the Corrosion Rate of Steel Reinforcement in FRP-Wrapped Concrete

AbstractA model to predict the corrosion rate of steel reinforcing bars in fiber-reinforced polymer (FRP) wrapped concrete columns is presented. A model proposed by the author to predict the reinforcement corrosion rate and cracking of the concrete cover due to diffusion of chloride ions and oxygen in concrete members is modified to predict the corrosion rate of reinforcing bars inside FRP-wrapped columns. As corrosion progresses and rust layers build up, oxygen has to diffuse through three different layers to be consumed in the cathodic reaction: the FRP wrap, the concrete cover, and the rust layer. As the rust layer thickness increases, the corrosion rate decreases until it reaches a very slow steady-state descent. The predicted corrosion rate is compared with experimental results reported in the literature. Initially, the model proposed previously by the author was used to predict the corrosion rate of an unwrapped pile to calibrate parameters such as the diffusion coefficient of oxygen with experiment...

Effects of Steel Slag Substitution in Geopolymer Concrete on Compressive Strength and Corrosion Rate of Steel Reinforcement in Seawater and an Acid Rain Enviroment

The effect of steel slag substitution as coarse aggregate on compressive strength in fly ash based-geopolymer concrete was studied. The compressive strength was evaluated by measuring the maximum acceptable load using compression testing equipment. Compressive strength depends on several factors, such as time and temperature of curing and the mixing proportion. The compressive strength of geopolymer concrete with steel slag substitution was higher compared to geopolymer concrete with gravel aggregate. The optimum compressive strength was found on the third day of curing at a temperature of 60 o C for both the geopolymer concrete with steel slag substitution and normal geopolymer concrete. Reinforcement corrosion was evaluated by measuring the corrosion current density using a linear polarization potentiostatic scan. The corrosion rate of reinforcing steel in geopolymer concrete with steel slag substitution was found to be higher compared to normal geopolymer concrete without steel slag in seawater medium, whereas in an acid rain environment, steel slag substitution increased corrosion resistance. The corrosion rate of geopolymer concrete with steel slag substitution was found to be lower compared to normal geopolymer concrete. The corrosion rate was found to be very high at an early stage and decreased with time.

Effectiveness of inhibitors in increasing chloride threshold value for steel corrosion

This investigation was aimed at evaluating the effectiveness of corrosion inhibitors in increasing the chloride threshold value for steel corrosion. Three types of corrosion inhibitors, calcium nitrite (Ca(NO2)2), zinc oxide (ZnO), and N,N′-dimethylaminoethanol (DMEA), which respectively represented the anodic inhibitor, cathodic inhibitor, and mixed inhibitor, were chosen. The experiment was carried out in a saturated calcium hydroxide (Ca(OH)2) solution to simulate the electrolytic environment of concrete. The inhibitors were initially mixed at different levels, and then chloride ions were gradually added into the solution in several steps. The open-circuit potential (Ecorr) and corrosion current density (Icorr) determined by electrochemical impedance spectra (EIS) were used to identify the initiation of active corrosion, thereby determining the chloride threshold value. It was found that although all the inhibitors were effective in decreasing the corrosion rate of steel reinforcement, they had a marginal effect on increasing the chloride threshold value.

Influence of Stay-in-Place Forms on Concrete Bridge Deck Corrosion

This research is focused on the influence of stay-in-place (SIP) forms on the corrosion of reinforcement in concrete bridge decks. The laboratory study plan contained a total of 27 specimens—nine cells of three specimens each. The nine cell test conditions were with and without SIP forms, one and two cathode bars for each anode bar, and spacing distances between cathode and anode of 2, 3, and 4 in. (51, 76, and 102 mm). The specimens were maintained at a constant temperature and humidity throughout the 45-month chloride ponding cycles with testing periods between 0 to 14 months and 35 to 45 months. Corrosion testing during the two test periods included concrete resistivity, half-cell potential, corrosion rate, and macrocell currents with chloride concentrations and autopsies at 45 months. The effects of SIP forms on micro- and macrocell corrosion of reinforcement were investigated by statistically comparing the performance of specimens with and without SIP forms. It was determined that microcell corrosion was the principal corrosion mechanism. The presence of SIP forms showed a reduction in macrocell currents; however, it had no significant influence on the corrosion rate of steel reinforcement.

Practical model for predicting corrosion rate of steel reinforcement in concrete structures

A practical model for predicting the corrosion rate of steel reinforcement in concrete structures was proposed. The numerical model with nonlinear boundary conditions for the macrocell corrosion of steel reinforcement in concrete structures was established based on the electrochemical principles and the Bulter–Volmer equation. The influences of various parameters such as anode-to-cathode (A/C) ratio, relative humidity, concrete resistivity, cover thickness on the corrosion control mode and corrosion rate of steel reinforcement in concrete structures were then investigated. Finally, a practical model for predicting the corrosion rate of steel reinforcement in concrete structures was proposed based on a comprehensive nonlinear regression analysis with easily quantifiable engineering parameters, such as water-to-cement (W/C) ratio, chloride content, thickness of concrete cover and relative humidity. Model comparison and experimental verification demonstrate that the proposed prediction model is of good accuracy and applicability to real life scenarios in terms of capturing the corrosion behavior of steel reinforcement in different situations.

コンクリートの中性化後における鉄筋の腐食速度に関する研究

In this paper corrosion rate of steel reinforcements after carbonation of concrete was studied using AC impedance technique and weight loss measurements taking the effects of cement type, water to binder ratio, cover thickness,relative humidity and the like into account. Based on the study a corrosion rate eguation that includes the above factors and the relative humidity of 40 to 95% as variables was proposed by modifying Stern-Geary eguation. Ways of applying the eguation to the inside and outside environments of buildings were discussed, which resulted in a proposal of estimated corrsion rates after carbonation.