Corrosion Of Reinforced Concrete Structures Research Articles

Exploring chloride-induced corrosion in reinforced concrete structures through embedded piezo sensor technology: an experimental and numerical study

Corrosion of steel in concrete is one of the major problems with respect to the durability of reinforced concrete (RC) structures. Thus, monitoring the corrosion in real-time is essential to prevent structural damage. However, one of the main challenges is to simulate the real-time development of corrosion in the RC structure. In recent years, smart aggregates, also called embedded piezo sensors (EPS), have become increasingly popular for monitoring localized and corrosion damage in RC structures using electro-mechanical impedance (EMI). This paper presents the experimental and numerical investigation of corrosion in RC structures subjected to the chloride-laden environment using EPS via the EMI technique. To fulfil this objective, the study has been carried out in two stages such as; in the first stage, the experiments are conducted on the RC specimen, and the EMI response was obtained both in a pristine state and when accelerated corrosion progressed. In the second step, a numerical model of the RC specimen has been developed based on the experimental data in the COMSOL software, and the effect of corrosion in the form of varying mass loss percentages has been simulated. Based on the results, it is concluded that the experimental and numerical conductance signatures before and after corrosion are matched. The deterioration in terms of stiffness loss in the RC specimen was 18.20% at 30% mass loss.

Resistivity Method Evaluation of Corroded OPS-Concrete

Many reinforced concrete (RC) structures are built around coastal areas or above the sea, which has very high risk of corrosion. Steel reinforcement corrosion in RC structures can cause failure of structural if not taken into account. Therefore, in this research, it is very important how durable oil palm shells (OPS) in corrosive area. One way to determine the durability of concrete without damaging it is to use the non-destructive testing method, which in this research uses the resistivity method. The method can evaluate the durability of concrete due to corrosion in OPS concrete. The effect of the percentage addition of OPS (10%, 20%, 30%, and 40%) and the addition of corrosion level (0.5%, 1%, 1.5%, 2%, 3%, and 4%) were also analysed. The results show that adding an oil palm shell (OPS) and the corrosion rate with natural and impressed current methods reduce the flexural strength of the concrete and the value of the resistivity of the concrete. The results show that adding an oil palm shell (OPS) and the corrosion rate with natural and impressed current methods reduce the flexural strength of the concrete and the value of the resistivity of the concrete. The resistivity value decreases along with the addition of the corrosion rate on each specimen.

Corrosion Assessment in Reinforced Concrete Structures by Means of Embedded Sensors and Multivariate Analysis-Part 1: Laboratory Validation.

Reinforced Concrete Structures (RCS) are a fundamental part of a country's civil infrastructure. However, RCSs are often affected by rebar corrosion, which poses a major problem because it reduces their service life. The traditionally used inspection and management methods applied to RCSs are poorly operative. Structural Health Monitoring and Management (SHMM) by means of embedded sensors to analyse corrosion in RCSs is an emerging alternative, but one that still involves different challenges. Examples of SHMM include INESSCOM (Integrated Sensor Network for Smart Corrosion Monitoring), a tool that has already been implemented in different real-life cases. Nevertheless, work continues to upgrade it. To do so, the authors of this work consider implementing a new measurement procedure to identify the triggering agent of the corrosion process by analysing the double-layer capacitance of the sensors' responses. This study was carried out on reinforced concrete specimens exposed for 18 months to different atmospheres. The results demonstrate the proposed measurement protocol and the multivariate analysis can differentiate the factor that triggers corrosion (chlorides or carbonation), even when the corrosion kinetics are similar. Data were validated by principal component analysis (PCA) and by the visual inspection of samples and rebars at the end of the study.

Combined GPR and Self-Potential Techniques for Monitoring Steel Rebar Corrosion in Reinforced Concrete Structures: A Laboratory Study

Steel rebar corrosion is one of the main causes of the deterioration of engineering reinforced structures. Steel rebar in concrete is normally in a non-corroding, passive condition, but these conditions are not always achieved in practice, due to which corrosion of rebars takes place. This degradation has physical consequences, such as decreased ultimate strength and serviceability of engineering concrete structures. This work describes a laboratory test where GPR and SP geophysical techniques were used to detect and monitor the corrosion phenomena. The laboratory tests have been performed with several reinforced concrete samples. The concrete samples were partially submerged in water with a 5% sodium chloride (NaCl) solution. Therefore, an accelerated corrosion phenomenon has been produced by a direct current (DC) power supply along the rebar. The geophysical measurements were performed with a 2.0 GHz centre frequency GPR antenna along several parallel lines on the samples, always being the radar line perpendicular to the rebar axis. The GPR A-scan amplitude signals were elaborated with the Hilbert Transform approach, observing the envelope variations due to the progress of the steel rebar corrosion in each concrete sample. Moreover, Self-Potential acquisitions were carried out on the surface of the concrete sample at the beginning and end of the experiments. Each technique provided specific information, but a data integration method used in the operating system will further improve the overall quality of diagnosis. The collected data were used for an integrated detection approach useful to observe the corrosion evolution along the reinforcement bar. These first laboratory results highlight how the GPR should give a quantitative contribution to the deterioration of reinforced concrete structure.

Deterministic and probabilistic approaches for corrosion in RC structures: A direct proposed model to total service life predictions

In this paper the negative effects of the chloride ions attack in reinforced concrete (RC) elements have been studied. For this the vertical and horizontal chloride diffusivity has been treated by several models to identify the more relevant factor affecting the chloride concentration. The pitting corrosion has been treated to define the resistance losses of the shear forces and bending moments. An alternative deterministic/probabilistic procedure, by a direct and systematic new model, has been proposed to estimate the total time of service life for RC elements at the design phase. Several detailing configurations of steel bars in a RC beam, water/cement ratio and level of aggressiveness have been analysed to compare the model predictions. In this sense, this paper should provide useful results for analysts in terms of probability of failure for resistance losses and time of corrosion initiation. The goal is not only to provide practical results but also to evaluate the issue in a more modern risk analysis throughout the proposed prediction model.

Real-time monitoring of residual strength in corroding steel reinforcement using ultrasonic-guided waves and multi-physics modelling

Corrosion-induced material strength degradation is a major threat to the service life of reinforced concrete (RC) structures. Continued mass loss and pit formation after the initiation of corrosion in reinforcing steel consequently results in strength degradation. In this study, a non-destructive structural health monitoring (SHM) approach using ultrasonic guided waves with multi-physics modelling to monitor and forecast strength degradation of corroding steel is presented. Surface-bonded piezoelectric wafer transducers (PWTs) are used for actuating and sensing of guided waves in order to correlate the group velocity and amplitude of flexural wave modes with the strength reduction. The major findings of the work are presented in the form of empirical relationships between guided wave characteristics with reduced yield, ultimate, and buckling strength of corroded steel. It is observed that for a rebar of 12 mm diameter having slenderness ratio between 8 and 10, a 10% increase in amplitude and 8.44% increase in group velocity of flexural mode for corroding steel indicates a corresponding reduction of 10.278% in yield strength, 10.277% in ultimate strength, and 4.45% in buckling strength in progression phase of corrosion. A multi-physics numerical model of corrosion in RC structures that considers the effect of local exposure and environment is then elucidated with deviation less than 6.34% from experimental results in order to forecast the mass loss. The presented data fusion strategy, which combines guided wave-based monitoring and multi-physics modelling finds valuable application in assessing the current state of degradation in structural performance and strength-based service life prediction.

Carbonation and Corrosion Problems in Reinforced Concrete Structures

Reinforced concrete (RC) has been commonly used as a construction material for decades due to its high compressive strength and moderate tensile strength. However, these two properties of RC are frequently hampered by degradation. The main degradation processes in RC structures are carbonation and the corrosion of rebars. The scientific community is divided regarding the process by which carbonation causes structural damage. Some researchers suggest that carbonation weakens a structure and makes it prone to rebar corrosion, while others suggest that carbonation does not damage structures enough to cause rebar corrosion. This paper is a review of the research work carried out by different researchers on the carbonation and corrosion of RC structures. The process of carbonation and the factors that contribute to this process will be discussed, alongside recommendations for improving structures to decrease the carbonation process. The corrosion of rebars, damage to passive layers, volume expansion due to steel oxidation, and crack growth will also be discussed. Available protection methods for reducing carbonation, such as rebar structure coating, cathodic protection, and modifier implementation, will also be reviewed. The paper concludes by describing the most significant types of damage caused by carbonation, testing protocols, and mitigation against corrosion damage.

Mechanical model for the shear strength prediction of corrosion-damaged reinforced concrete slender and non slender beams

Steel corrosion in RC structures leads to a reduced reinforcement area, changes in steel mechanical properties, cracking and, eventually, concrete cover spalling, among other phenomena. Stirrups are generally small in diameter and, given their small concrete cover, they are more susceptible to corrosion than longitudinal reinforcement. Hence their corrosion significantly affects shear strength. Most existing models that deal with reduction in the shear strength of corrosion-damaged reinforced concrete (RC) structures are empirical; that is, they have been numerically fitted to test results. In this context, conceptual models based on structural mechanics principles and verified for corrosion-damaged members are still needed.In this paper, the Compression Chord Capacity Model (CCCM), a shear mechanical model previously derived by the authors, is adapted to predict the shear strength of corrosion-damaged RC beams. For this purpose, the model parameters that can be affected by steel corrosion in RC beams were identified and modified accordingly. CCCM predictions were compared to the experimental results of 146 slender and non slender beams failing in shear, in which stirrups and/or longitudinal reinforcement was subjected to corrosion. The CCCM achieved very satisfactory shear strength predictions when reductions in reinforcement areas and web width were taken into account, with a mean value of the Vtest/Vpred ratio equaling 1.19 and a 19.5% coefficient of variation. Finally, a parametric analysis was performed to show the predicted reductions in shear strength according to the CCCM compared to the experimental results of some especially relevant tests.

Assessment of corroded prestressed and posttensioned concrete structures: A review

AbstractPrestressed structures are commonly used all over the world. They might be subjected to degradation, such as corrosion of the prestressing steel. This can influence the resistance of these structures and induce early failure. Hence, prediction of the corrosion level is important in the assessment of existing prestressed structures. For this purpose, the corrosion process and the accompanying influences on the structure should be modeled. For reinforced concrete (RC) structures, a lot of research and guidelines are available to model the corrosion process. Nevertheless, this corrosion process might differ for prestressed structures, due to the different structural composition, the different geometry of the strands or tendons compared with reinforcement bars, the presence of the prestress, and so on. Moreover, for posttensioned structures, initiation and propagation of corrosion are even more different from corrosion in RC structures, due to the location of the steel in ducts and the lack of direct contact with the surrounding concrete. In this paper, a state‐of‐the‐art on the assessment of prestressed and posttensioned structures subjected to corrosion is given based on a literature review. Different models for the corrosion process and their influence on the structure are discussed. Comparison is made between reinforced, prestressed, and posttensioned structures. Furthermore, some assessment procedures are indicated and relevant topics for further research are given.

Probabilistic estimation of flexural loading capacity of existing RC structures based on observational corrosion-induced crack width distribution using machine learning

Corrosion-induced crack width can provide effective information on the deterioration level of in situ corroded reinforced concrete (RC) structures. However, the uncertainty associated with the relationship between corrosion-induced crack width and steel corrosion in RC structures is quite large. In this study, a probabilistic framework for estimating the structural capacity of corroded RC structures using the observational corrosion-induced crack width distribution and machine learning is proposed. Based on the experimental results of corroded RC beams, random field theory, and finite element (FE) analysis, artificial samples composed of corrosion-induced crack width and steel weight loss distributions over the RC beams are generated. Two machine learning-based models are then developed using these samples to estimate the steel weight loss distribution from the observational corrosion-induced crack distribution. Finally, a Monte Carlo-based FE analysis with the estimated steel weight loss distribution as the input data is conducted to obtain the probability density function (PDF) of the structural capacity of corroded RC beams. For illustrative purposes, the effect of observational corrosion-induced crack width distribution on the PDF of flexural capacity of an existing RC beam is investigated using the proposed framework. The results show that the proposed framework using a machine learning-based model is a reliable and computationally efficient approach for estimating the structural capacity of corroded RC members and demonstrates the potential for assessing the deterioration condition of existing RC structures based on the corrosion-induced crack width distribution.

Manufacturing and structural performance of glass-fiber-reinforced precast-concrete boat ramp planks

Glass-fiber-reinforced-polymer (GFRP) bars are an ideal solution for eliminating the problems of steel corrosion in reinforced-concrete structures exposed to marine environments. The potential long-term benefits of the reduced maintenance costs and increased service life of GFRP-reinforced concrete structures have not been fully realized due to these reinforcing materials being more costly than steel bars. This study aims to demonstrate the cost-effectiveness of GFRP bars as internal reinforcement in precast-concrete boat-ramp planks. This is the first study that provided a comparative evaluation of the manufacturing and structural performance of planks reinforced with GFRP bars or galvanized-steel bars to fully convince engineers and asset owners of the economic benefits of specifying and using GFRP bars in infrastructure projects. The results of the study revealed that the fabrication and installation of the reinforcing mesh constituted the main differences between planks reinforced with GFRP or galvanized steel. Overall, fabricating precast-concrete boat-ramp planks with two layers of GFRP bars required less labor and equipment, and yielded better serviceability and structural performance than the current plank design using galvanized steel. These benefits led to approval and publication of the standard drawings for a new plank design for implementation in boating-infrastructure projects in Australia.

Carbonation Induced Corrosion in Reinforced Concrete Structures - A Review

Carbonation Induced Corrosion in Reinforced Concrete Structures - A Review

On the use of Strain-Hardening Cementitious Composite covers to mitigate corrosion in reinforced concrete structures

Previous research has shown the effectiveness of Strain-Hardening Cementitious Composites (SHCC) in mitigating corrosion-induced damage in reinforced-concrete (RC) structural members due to the inherently limited crack widths of this material. The objective of this research is to investigate whether using SHCC only in the cover of a RC member is as effective in mitigating corrosion-induced damage as using SHCC in the entire member. Potentiostatic accelerated macro-cell corrosion experiments with wetting and drying cycles were used to simulate corrosion-induced damage in four different types of cylindrical specimens with steel reinforcement: type (a) made entirely with normal concrete, type (b) made entirely with SHCC, type (c) made with a conventional concrete core and an intact SHCC shell, and type (d) made with a conventional concrete core and a pre-damaged SHCC shell. Results show that the extent of corrosion damage, as measured by rebar mass loss over time, in types (b) and (c) is similar. Furthermore, in spite of the pre-existing damage, type (d) specimens offer corrosion protection similar to type (a) specimens. These results, combined with additional investigations on shrinkage and bond strengths between SHCC and concrete, demonstrate the feasibility of using precast SHCC shells for effective mitigation of corrosion in RC structures.

Tests on seismic performance of corroded reinforced concrete shear walls repaired with basalt fiber-reinforced polymers

Abstract Reinforcement corrosion caused by carbonation of the concrete cover or excessive chloride concentration primarily leads to the deterioration of reinforced concrete (RC) structures. To address the issue of reinforcement corrosion in RC structures, basalt fiber-reinforced polymer (BFRP) is today slowly gaining acceptability as an effective alternative to repair corroded RC structures in seismic areas. The present paper aims to evaluate the feasibility of using BFRP as externally bonded jackets applied on the surface of the RC shear walls. Seven medium-rise walls with aspect ratios of 1.6 were tested under the combination of constant axial load and cyclic lateral load, including one original mock-up, three corroded mock-ups with various corrosion rates, and three corroded mock-ups repaired with BFRP jackets. The seismic performance of original and repaired mock-ups with respect to failure mode, hysteretic behavior, stiffness, ductility, energy dissipation capacity, and strength was discussed. In addition, a strut-and-tie model in consideration of reinforcement corrosion and FRP confinement as well as a model for confining stress distribution of cross-sections featuring large aspect ratio (over 2) were proposed. The test and theoretical results show that application of BFRP jackets is able to minimize the corrosion concerns and restore the seismic performance of corroded RC shear walls.

Theoretical and practical aspects of improving the durability of steel reinforcement in transport designs, using passivation and plasticizing chemical additives

The article deals with the problem of steel reinforcement corrosion in reinforced concrete structures exposed to aggressive media, in particular in reinforced concrete construction of transport infrastructure, in snowy areas, and subject to the influence of chlorides contained in applied deicing agents. Basic schemes for preventing the reinforcement corrosion in reinforced-concrete structures have been considered and analyzed. Prospects of primary protection against corrosion of reinforcement by introducing chemical additives with plasticizing/passivating action in a concrete mixture with mixing water have been considered in detail. The physical/chemical mechanism of the protective action of a superplasticizer together with a passivator has been highlighted.

Numerical Simulation of Chloride Ion Induced Corrosion of Reinforced Concrete Structures in Marine Environment

A numerical simulation method of chloride ion induced corrosion was proposed. Based on the different corrosion mechanisms of submersion zone, tidal zone, splash zone and atmosphere zone, a series of theoretical equations were built by taking into account the effect of temperature, humidity, concrete age, chloride ion concentration and seawater convection etc. Further,a numerical simulation program was developed to simulate the service status of a bridge pier of Qingdao bay bridge by means of COMSOL coupled with factors such as temperature, humidity and chloride ion transmission etc. The results show that: (1) the numerical method can simulate chloride ion induced corrosion well; (2) the place where depassivation occurred for the reinforced steel bar corresponds to submersion zone, tidal zone, tidal zone and atmosphere zone in turn; (3) for this living example, the first depassivation of reinforced steel bars for a bare reinforced concrete bridge pier may 定稿日期:2014-09-09 基金项目:山东省自然科学基金项目(ZR2012EEL23)资助 作者简介:程旭东,男,1971年生,博士,教授 通讯作者:程旭东,E-mail:chengxd@upc.edu.cn,研究方向为土木工程、油田地面工程结构及LNG储罐 DOI:10.11902/1005.4537.2014.146 2期 程旭东等:沿海钢筋混凝土结构Cl侵蚀数值模拟方法研究 occur in the place about -2.200 m (near to the center of tidal range zone) after in service for 25 a.

Probability-Based Durability Design for Concrete Structure with Crack: Bimodal Distribution of Chloride Diffusion

* (Received March 3, 2015 / Revised March 24, 2015 / Accepted March 25, 2015)Chloride ions in RC (Reinforced Concrete) structures can cause very severe corrosion in reinforcement steel. It is generally in formed that chloride penetration can be considerably accelerated by enlarged chloride diffusion due to cracks. These cracks play a rol e in main routes through which chloride ions penetrate into the concrete, and also lead to steel corrosion in RC structures exposed to ch loride attack, such as port and ocean structures. In this paper, field survey including evaluation of crack and chloride concentration distribution in concrete is performed to investigate an effect of crack on chloride diffusion. The service life of cracked conc rete exposed to the marine environmental condition is estimated considering the crack effect on chloride diffusion. For this purpose , diffusion coefficients in cracked concrete are obtained based on the field survey. Using the relationship between diffusion coe fficientsin the cracked concrete and the crack widths, service life of the cracked concrete is predicted in a probabilistic framework. A bimodal distribution with two peaks, consisting of a weighted sum of two normal distributions is introduced to describe chloride diffus ion of the concrete wharf with crack. Keywords : Chloride diffusion, Crack width, Service life, Probability, Bimodal distribution* Corresponding author E-mail: jjuni98@hannam.ac.kr

Research on Corrosion of Reinforced Concrete Structures by Chloridion in Port Engineering Construction

In port engineering construction, the source of chloridion is concrete raw materials, admixtures and the penetration of seawater. Chloridion makes rebar corrosion, and makes the expansion and crack of reinforcement concrete, leading to concrete structural damage. By selecting the right concrete raw material, appropriate admixtures and to ensure concrete construction quality, in order to effectively avoid chloridion to the damage of reinforced concrete structures in construction.

Service life prediction of concrete wharves with early-aged crack: Probabilistic approach for chloride diffusion

Early-aged cracks due to hydration heat and drying shrinkage occur unavoidably in reinforced concrete (RC) structures. These cracks may be the main routes through which chloride ion penetrates into the concrete and also can be one of the major reasons of steel corrosion in RC structures exposed to chloride, such as port and ocean structures. In this paper, the service life of RC structures exposed to the marine environment conditions is predicted considering the crack effect on chloride penetration. First, diffusion coefficients in sound and cracked concrete of wharf structures are obtained through field investigations. Then, through the relationship between diffusion coefficients and crack widths, service life of the cracked concrete is predicted in the probabilistic framework of Monte Carlo Simulation. Furthermore, the predicted service life derived from the field investigations is compared with the values obtained from the traditional method based on allowable crack width concept.

Reflexiones sobre los métodos electroquímicos de rehabilitación de las estructuras corroídas de hormigón armado

Electrochemical realkalinisation and electrochemical chloride removal have shown their capacity to eliminate, in just a few weeks, the causes of corrosion of reinforced concrete structures (RCS), and for this reason are currently receiving very special attention. This communication seeks to answer some fundamental questions that continue to arouse great controversy, which are summarized in the question: removing the causes of corrosion in RCS suffice to stop rusting? To this end an analysis is made of the responses of clean and precorroded electrodes in a solution that simulates the aqueous phase of the concrete pore network. According to the results obtained, the efficiency of electrochemical rehabilitation methods depends heavily on the degree of precorrosion of the rebars.