Corrosion Of Steel Rebar Research Articles

Research on corrosion detection for steel reinforced concrete structures using the fiber optical white light interferometer sensing technique

In this paper, a novel kind of steel rebar corrosion monitoring technique for steel reinforced concrete structures is proposed, designed, and tested. The technique is based on the fiber optical white light interferometer (WLI) sensing technique. Firstly, a feasibility test was carried out using an equal-strength beam for comparison of strain sensing ability between the WLI and a fiber Bragg grating (FBG). The comparison results showed that the sensitivity of the WLI is sufficient for corrosion expansion strain monitoring. Then, two WLI corrosion sensors (WLI-CSs) were designed, fabricated, and embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion. Their performance was studied in an accelerated electrochemical corrosion test. Experimental results show that expansion strain along the fiber optical coil winding area can be detected and measured accurately by the proposed sensor. The advantages of the proposed monitoring technique allow for quantitative corrosion expansion monitoring to be executed in real time for reinforced concrete structures and with low cost.

Influence of aggregate shapes on drying and carbonation phenomena in 3D concrete numerical samples

This study aims at generating numerical 3D samples of concrete so as to study the effects of the granular inclusions shape on the macroscopic kinetics of reactive transport phenomena. Two types of mesostructure configurations are considered: the first one is composed of a matrix of mortar in which are randomly distributed inclusions corresponding to the concrete coarse aggregates, and the second one also includes a steel rebar. The choice of a mesoscopic modeling for the mortar matrix is based on the need to obtain numerical structures of reasonable size. In particular, the Interfacial Transition Zones (ITZs) are assumed to be incorporated into the homogenized mortar properties. This study is applied to the case of drying and atmospheric carbonation by using simplified models solved by the finite element code Cast3M. The purpose is to quantify the influence of the aggregate shape on the kinetics of macroscopic transfer and the isovalue lines for some physical variables representative of the reactive transport problems: saturation degree for drying, and porosity, calcite and portlandite concentrations for carbonation. Basic aggregates shapes are studied (spheres, cubes), as well as more complex ones (Voronoi particles) which are supposed to be more representative of real aggregates. The effects of ‘non-isotropic’ shapes (oblate and prolate ones) are also investigated. It is shown that the influence of the aggregate shapes appears negligibly small on macroscopic indicators, except for oblate shapes with aspect ratios of 3. This latter case also exhibits substantial local delayed effects and a more important variability, which may have some importance for a precise description and estimation of degradation processes related to steel rebar corrosion.

Experimental and numerical studies on the cyclic behavior of R/C hollow bridge piers with corroded rebars

A comprehensive experimental program of cyclic tests on 1:3-scale models of bridge piers is going to be carried out at the Laboratory of Structures and Materials of the University of Basilicata. The testing models include eight RC single shaft piers with hollow circular cross section. Four piers have been realised using corroded steel rebars. In this paper, the results of preliminary numerical simulation analyses of the cyclic behaviour of the piers, carried out with Opensees using fiber-based models, are presented. Pull-out and lap-splice effects of steel rebars have been taken into account in the numerical analyses. First, the experimental specimens and the test set up are presented. Next, the results of the numerical analyses are discussed. In the numerical analyses, different configurations and levels of corrosion have been considered. The effective stiffness and equivalent damping of the piers is reported as a function of pier ductility and pier drift.

Seismic Performance of Degraded Shear Walls for Long-Term Compliance Periods

Seismic performance evaluations of nuclear facilities are usually based on seismic probabilistic risk analyses that do not include the effects of concrete aging, which may decrease the capacity of reinforced concrete (RC) components with time. This study relates the physical mechanisms that take place during aging of concrete (e.g., cracking, and rebar corrosion) and the deterioration of mechanical properties that affect the system capacity under seismic events. The seismic performance evaluation uses available experimental data of steel reinforcement corrosion and variability of concrete parameters as a function of time. To obtain the variation in the system capacity caused by concrete aging, detailed numerical models of RC components and models of the selected structural systems are developed. The probability of unacceptable performance, or seismic failure, is computed by convolving the fragility data and selected hazard curves. The calculation includes the gain of concrete compressive strength with time. However, this gain in strength does not overcome the degradation of seismic performance caused by concrete cracking and corrosion of steel rebars. The results indicate that aging effects on RC components are largely influenced by seismic hazard at the site.

Bond Behaviour between Recycled Aggregate Concrete and Corroded Steel Rebars

In this paper, corrosion percentages ranged from 0 to 7.62% of steel rebar for pulling out specimens was controlled by the accelerated method of electrochemistry. According to the RILEM standard, pulling out test with dimensions of 200×200×200mm3 and recycled aggregate concrete (RAC) of C30 was carried out, and the load versus slip curves between RAC and corroded steel rebars with different corrosion percentages were recorded. Based on the experimental results, the effect of RAC and reinforcement corrosion on the bond behaviour between steel rebars was investigated. The results show that the bond strength between RAC and deformed bars increases with corrosion up to a certain amount, and then the bond strength decreases as the corrosion rate further increases, which is similar to that of normal concrete. However, the decreasing rate of the bond strength between RAC and corroded steel rebars is much faster than that between normal concrete and corroded steel bars. According to the testing results, the relationship of bond stress-slip between corroded bars and RAC was given in the end.

Analysis of the Electromagnetic Signature of Reinforced Concrete Structures for Nondestructive Evaluation of Corrosion Damage

This paper presents a nondestructive corrosion damage detection method for reinforced concrete structures based on the analysis of the electromagnetic signature of the steel rebar corrosion. The signature of the corrosion on the scattered field upon microwave illumination is first numerically analyzed. First-order quality factor parameters, the energy and the mean propagation delay, are proposed to quantify the corrosion amount in the structure. To validate the model, low-profile ultra-wide-band antennas (3-12 GHz) are fabricated and measured. Measurements on 12 reinforced concrete samples with induced corrosion are performed, using three different antenna setups. The experiments demonstrate a good correlation between an increase in the corrosion amount with a decrease in the energy and an increase in the time delay of the propagated signal.

Characterization of a water-based paint for corrosion protection

Corrosion of steel rebars in reinforced concrete is one of the major problems in the construction industry. Carbonation reactions of concrete with carbon dioxide and, mainly, the chloride salts action are the main causes responsible for concrete degradation. Protective coatings help to improve the durability of concrete structures by acting as a physical barrier against the corrosion agents. Waterborne paints are usually used for concrete protection rather than solvent-based paints since they are less pollutant. The aim of this work is to investigate the influence of the pore size and porosity on the permeability of the paints films toward sodium chloride. Three characterization methods from membrane science were implemented to characterize paint coatings. The time-lag method was used to determine the permeability toward the sodium chloride and toward helium and argon, these for approximately 100% relative humidity. From the seven waterborne paints formulated, only one was found to be suitable for surface protection of reinforced concrete, since its permeability toward NaCl was smaller than 10−14 m2 s−1, the threshold value required by National Laboratory of Civil Engineering (LNEC) in Portugal. For the formulated paints, it was observed that the average pore size correlates well with the permeability toward sodium chloride. This is an important result since obtaining the permeability toward sodium chloride of corrosion protective paints is very time consuming, while the average pore size can be obtained in a much shorter time.

Modelling the Performance of Sodium Nitrite and Aniline as Inhibitors in the Corrosion of Steel-reinforced Concrete

The performances of sodium nitrite and aniline inhibitors on the corrosion of concrete steel rebar partially immersed in sodium chloride and sulphuric acid media were investigated in this study. The open circuit potential corrosion monitoring technique was employed for the marine and acidic simulating environments and potential readings were taken in accordance with ASTM C 876. Inhibiting quality and uniformity of the inhibitors were then analyzed using the Weibull probability density distribution as an extreme value statistical modelling approach to study performance effectiveness and predict the most efficient inhibitor in each media. In the statistically analyzed experimental results for each of the inhibitor concentrations employed, (0.679 M) sodium nitrite is identified as exhibiting the best inhibiting quality in sodium chloride while (0.137 M) aniline was predicted as showing the lowest probability of corrosion risk in sulphuric acid medium. The synergetic admixtures employed in the study performed poorly in inhibiting effectiveness compared to the control specimens in the two media considered. The overall probabilistic results predicted preferences of sodium nitrite as inhibitors in the sodium chloride medium simulating saline environments and aniline in sulphuric acidic medium simulating sewage or underground microbial environments

Non-destructive electrochemical characterizations of reinforced concrete corrosion: basic and symbolic data analysis

Reinforcement corrosion is one of the major structural performance issues that need to be solved to extend the service lifetime of a concrete structure. It is influenced, on the one hand, by the concrete itself sound or contaminated (with chloride or carbonated) and, on the other hand, by the environmental conditions such as temperature and relative humidity (controlled or outdoor). To characterize the corrosion of steel rebar in concrete prisms, several electrochemical measurements such as half-cell potential, linear polarization resistance and impedance were performed and corrosion rates were then calculated. A database containing > 3000 values has been established. These data have been firstly analyzed with basic statistics and secondly they have been modeled as symbolic data and studied with a principal component analysis. It is shown that symbolic principal component analysis is a powerful tool leading to more refined results.

Brillouin Corrosion Expansion Sensors for Steel Reinforced Concrete Structures Using a Fiber Optic Coil Winding Method

In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring.

A phenomenological model for the chloride threshold of pitting corrosion of steel in simulated concrete pore solutions

PurposeThis work seeks to present a systematic study that aimed to provide quantitative understanding of the fundamental factors that influence the chloride threshold of pitting corrosion of steel in concrete, by conducting a set of laboratory tests to assess the corrosion potential (Ecorr) and pitting potential (Epit) of steel coupons in simulated concrete pore solutions.Design/methodology/approachWith the aid of artificial neural network, the laboratory data were used to establish a phenomenological model correlating the influential factors (total chloride concentration, chloride binding, solution pH, and dissolved oxygen (DO) concentration) with the pitting risk (characterized by Ecorr−Epit). Three‐dimensional response surfaces were then constructed to illustrate such predicted correlations and to shed light on the complex interactions between various influential factors.FindingsThe results indicate that the threshold [Cl−]/[OH−] of steel rebar in simulated concrete pore solutions is a function of DO concentration, pH and chloride binding, instead of a unique value.Research limitations/implicationsThe limitations and implications of the research findings were also discussed.Practical implicationsThis research could have significant practical implications in predicting the service life of new or existing reinforced concrete in chloride‐laden environments.Originality/valueThis study further advances the knowledge base relevant to the chloride‐induced corrosion of steel rebar in concrete.

강섬유 보강 콘크리트의 수송계수 및 부식저항효과

This study investigated the corrosion properties of reinforced concrete with the addition of steel fibers. The transport properties of steel fiber-reinforced concrete such as permeable void, absorption by capillary action, water permeability and chloride diffusion were first measured to evaluate the relationship with the corrosion of steel rebar. Test results showed a slight increase on the compressive strength with the addition of steel fibers as well as considerable improvement of penetration resistance to mass transport of harmful materials into concrete. The addition of steel fibers in reinforced concrete accelerated the initiation of steel corrosion contrary to the expected results based on the measured transport properties. The NaCl ponding surface showed the spalling failure due to the corrosion expansion of steel fibers and the cut-surface around the steel rebar showed the localized steel fiber`s corrosion. The wet-dry cycling with high chloride ions as well as high temperature seems to induce the increase of salt crystallization on the pores continually and the increased pressure with the steel fiber`s corrosion on the pores caused the spalling failure on the exposed surface. The microcracking on the surface therefore accelerated the movement of water, chloride ions and oxygen into the embedded steel rebar. The mechanism affecting corrosion of embedded steel reinforcement with steel fibers in this study are not yet fully understood and require further study comprising of accurate experimental design to isolate the effect of steel fiber`s potential mechanism on the corrosion process.

Performance Evaluation of Potassium Dichromate and Potassium Chromate Inhibitors on Concrete Steel Rebar Corrosion

This study investigated the performance of potassium dichromate and potassium chromate inhibitors on the corrosion of steel rebar in concrete partially immersed in sulfuric acid and sodium chloride medium. The open circuit potential corrosion monitoring technique was employed for the acidic and marine simulating environments, and potential readings were taken in accordance with ASTM C 876. Inhibiting quality and uniformity of the inhibitors were then analyzed using an extreme value statistical modeling approach of the Weibull probability density distribution for determining the most efficient inhibitor. In the inhibitor concentrations used, the statistically analyzed experimental results identified 0.145 M potassium chromate as exhibiting the best inhibiting quality in sulfuric acid whereas the synergetic admixture of 0.032 M potassium dichromate and 0.097 M potassium chromate was predicted as showing the lowest probability of corrosion risk in sodium chloride solution. However, the overall probabilistic results rated potassium chromate as the best inhibitor compared to potassium dichromate in most of the other concentrations investigated in the study, especially in concrete structures exposed to saline environments.

Corrosion behavior of steel rebar in coal gangue-based mortars

Corrosion of steel rebar is the most important durability problem of reinforced concrete. The aim of this research was to investigate the corrosion behavior of steel rebar in simulated pore solutions and gangue-blended cement mortar. The simulated pore solutions were based on the pore solution composition of gangue-blended cement. The pH and Cl− concentration of simulated pore solutions had significant effects on corrosion potential. However, an increase in pH reduced the influence of Cl− concentration on corrosion potential. The corrosion behavior of steel rebar in gangue-blended cement is different from that in simulated solutions. The gangue cementitious mortar surrounding steel rebar provides stable passivity environments for steel, leading to a decrease in ion diffusion coefficients. Alternating current impedance (ACI) analysis results indicated that the indicator Rc for concrete resistivity is higher for gangue mortar than for ordinary Portland cement (OPC), which improves its corrosion potential. The results from energy dispersive X-ray analysis (EDX) showed more aluminates and silicates at the rebar interface for gangue-blended cement. These aluminates improve the chloride binding capacity of hydrates in mortar, and increase the corrosion protection of steel rebar.

CFRP Rebar로 보강한 콘크리트 보의 휨 거동

철근의 부식을 해결하기 위해 철근의 대체 재료로 적용 가능한 FRP에 대한 연구의 적용성이 대두되었다. 그러나 취성적인 성질과 탄성계수가 낮은 단점을 가지고 있어, FRP rebar로 보강된 휨 부재의 사용성 평가 즉 처짐에 대한 연구가 필요하다. 본 연구에서는 보강비를 변수로 한, CFRP rebar로 보강된 콘크리트 보의 휨 실험을 수행하였다. 실험 결과, CFRP rebar로 보강된 실험체는 보강비가 증가함에 따라 내력 및 강성이 증가하는 양상을 보였으며, 철근 실험체와 동일한 단면성능을 발휘하기 위해서는 약 1.3배의 보강비가 요구되는 것으로 나타났다. 또한 유효단면2차모멘트에 대한 기존 제안식의 비교 결과, Bischoff & Scanlon이 제안한 식이 가장 정밀해에 가까운 처짐을 예측하였다. To address the problems caused by the corrosion of steel rebar, active research has recently been carried out on members where fiber-reinforced polymer (FRP) is used in place of rebar. As FRP bar is highly brittle and has a low modulus of elasticity, further research is needed on the evaluation of serviceability, in other words on the deflection of flexural concrete members reinforced with FRP rebars. Taking the reinforcement ratio as a variable, this paper analyzes the flexural capacity of concrete beams reinforced with CFRP rebar. The test results of specimens reinforced with CFRP rebar show an increase in stiffness and resisting force along with an increase in the reinforcement ratio. A reinforcement ratio of about 1.3 is needed for the member reinforced with CFRP rebar to show same section property of a steel member. Through a comparison for the value of an effective moment of inertia, the equation suggested by Bischoff & Scanlon predicted values closest to the actual results.

Experimental and analytical studies on one-way concrete slabs reinforced with GFRP molded gratings

Corrosion of steel rebars in bridge decks which are faced to harsh conditions, is a common problem in construction industries due to the porosity of concrete. In this research, the behavior of one-way concrete slabs reinforced with Glass fiber reinforced polymer (GFRP) molded grating is investigated both theoretically and experimentally. In the analytical method, a closed-form solution for load-deflection behavior of a slab under four-point bending condition is developed by considering a concrete slab as an orthotropic plate and defining stiffness coefficients in principal directions. The available formulation for concrete reinforced with steel is expanded for concrete reinforced with GFRP molded grating to predict ultimate failure load. In finite element modeling, an exact nonlinear behavior of concrete along with a 3-D failure criterion for cracking and crushing are considered in order to estimate the ultimate failure load and the initial cracking load. Eight concrete slabs reinforced with steel and GFRP grating in various thicknesses are also tested to verify the results. The obtained results from the models and experiments are relatively satisfactory.

The effect of processed fly ashes on the durability and the corrosion of steel rebars embedded in cement–modified fly ash mortars

Abstract This paper deals with the study of corrosion level of reinforcing steel bars embedded in Portland cement mortars containing different types of fly ash. Fly ashes used were obtained by physico-chemical treatments of an original F class fly ash to modify their magnetic properties and reduce their particle size. An original fly ash (T0) and three types of modified ashes were tested according to treatment duration and magnetic properties (T60, ground fly ash; TNM, non-magnetic fraction; TM, magnetic fraction). Corrosion tests on reinforced mortar specimens with and without different types of fly ashes, cured at 40 °C, and under accelerated carbonation conditions and seawater immersion, have been performed in order to obtain conclusions on durability. From the corrosion point of view the addition of TNM in mortars showed to be much more effective than addition of the original T0 fly ash.

Corrosion of steel bars in OPC mortar exposed to NaCl, MgCl2 and CaCl2: Macro- and micro-cell corrosion perspective

In North America, corrosion of the steel rebar commonly occurs due to chloride attack from deicing salts. In Canada, based on the severity and temperature of the ambient environment, three different deicing salts, or combination of them, are used: NaCl, MgCl2 and CaCl2. In this paper, the effect of each of these salts on the corrosion of steel rebar and their impact on the durability of the mortar have been investigated. The results show that CaCl2 has the most negative effect on the steel and, in high concentrations, on the integrity of the mortar. MgCl2 also deteriorates the mortar if used in high concentration, while NaCl has no apparent effect on mortar durability even in high concentration.

Effects of Recycled Coarse Aggregates on the Carbonation Evolution of Concrete

Concrete exposing to atmosphere suffers from changes in its internal structure, for instance loss of alkalinity of the cover concrete and corrosion of steel rebar due to carbonation, which in extreme cases affect the safety, the reliability and the durability or the service life of the structure. Carbonation is one of the key environmental actions that may cause structural failure. This study aims to gain some new information on the carbonation resistance when recycled coarse aggregates are used to mix new concrete. The concrete’s resistance to carbonation is determined by measuring the carbonation depth of 100mm×100mm×300mm concrete prisms in according to GBJ 82-85. Two series of tests including 9 groups of recycled aggregate concrete specimens are carried out, in which the effects of the quality and replacement of recycled coarse aggregates on the carbonation behavior of recycled concrete are evaluated. The essential test results are presented and discussed in this paper. Based on the findings of the present study, in order to reduce the unfavorable effects of recycled coarse aggregates on the recycled concrete, limiting the compressive strength grade of original concrete and the replacement of recycled coarse aggregate is a good option under the condition of using recycled concrete in considered projects.

Frequency considerations for a system using phase information to detect and image corrosion in steel rebars located at distances of 8–9 cm

Professor Gaydecki's group at The University of Manchester have imaged steel rebars using a system comprising of a square DC field generating coil with an array of sensors underneath, which produces an image without using a scanner. A square coil was used to generate an AC magnetic field allowing the skin depth principle to be used to detect corrosion. Also the receiver was placed in an orthogonal position instead of the original vertical position, enabling corrosion to be detected at deeper distances, particularly when using the phase information. When generating images of an area there is an optimum frequency range to enable the changes due to corrosion to be visualized.