scholarly journals The size effect of rebars, on the structural integrity of reinforced concrete structures, which are exposed to corrosive environments

2018 ◽  
Vol 188 ◽  
pp. 03009
Author(s):  
Argyro Drakakaki ◽  
Charis Apostolopoulos
Keyword(s):  
Reinforced Concrete ◽  
Structural Integrity ◽  
Chloride Concentration ◽  
Seismic Energy ◽  
Corrosion Damage ◽  
Chloride Ions ◽  
Exposed Surface ◽  
Plastic Hinges ◽  
Corrosive Environments ◽  
Critical Regions

The goal of the present study is to mention the importance of underestimation of the corrosion damage developed in critical load bearing areas, on the column bases, where formation of plastic hinges is attended, mainly during strong seismic events (Figure 1). In such cases, plastic hinges are expected to absorb the seismic energy, owed to seismic vibration. However, chloride induced corrosion is responsible for significant degradation of concrete infrastructures located in coastal areas. Forecasting the life expectancy of such structures, in corrosive environments, is a challenge in engineering, given the fact that existing internal, external, as well as subcutaneous defects, in combination with the aggressive environmental factors, may be responsible for the development of subcutaneous damage on steel reinforcement [1], which may diminish the tolerance of the critical regions of the structures. Moreover, it is widely known that penetration of chloride ions into reinforced concrete varies according to its porosity and its permeability, however, the major factor for corrosion initiation is the threshold of chloride concentration, which strongly depends on the exposed surface area of steel. In the present experimental study, the variation of corrosion damage, on bare specimens, was evaluated and correlated with the geometry of the exposed surface of steel in corrosion [2]. Finally, a correlation between short bare specimens and the “injured” areas of the long embedded specimens is estimated as well.

scholarly journals The electrochemical performance and modification mechanism of the corrosion inhibitor on concrete

2021 ◽  
Vol 28 (1) ◽  
pp. 352-562
Author(s):  
Meiyan Hang ◽  
Minghui Jiang ◽  
Junwei Xu ◽  
Teng Cheng ◽  
Hao Wang ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Electrochemical Performance ◽  
Corrosion Inhibitor ◽  
Electrode Potential ◽  
Concrete Structures ◽  
Corrosion Damage ◽  
Chloride Ions ◽  
Reinforced Concrete Structures ◽  
Chloride Corrosion ◽  
Chloride Environment

Abstract The purpose of this study was to solve the chloride corrosion damage problems of the rebar in reinforced concrete structures under the chloride environment. The effects of 1.0% triethanolamine (abbreviated as 1.0% TEA), 1.0% Ca(NO2)2, and 0.5% TEA + 0.5% Ca(NO2)2 (abbreviated as 1.0% composite corrosion inhibitor) on the electrochemical performance and modification mechanism of the mortar specimens were investigated by combining macro experiment and microanalysis. The results showed that the electrode potential of the rebar was effectively improved by incorporating the 1.0% composite corrosion inhibitor. This composite corrosion inhibitor displayed the ability to stabilize the electrode potential of the rebar; it also formed a passive film on the surfaces of the rebar, protected the rebar from chloride attack, and achieved satisfactory electrochemical performance. In addition, it could also effectively improve the strength of the mortar specimens and possessed the strong ability to bind chloride ions, thus signifying that it could promote cement hydration and accelerate the formation of cement to form AFt crystals. Therefore, the results of this investigation confirmed that this composite corrosion inhibitor could be effectively used in practical engineering to prevent the corrosion of reinforced concrete structures.

Coupling Effects of Chloride Penetrating and Corrosion Damage Evolving Process in Concrete under Marine Environment

2016 ◽  
Vol 846 ◽  
pp. 245-250
Author(s):  
Qin Zhang ◽  
Li Guo ◽  
Xiao Ming Guo
Keyword(s):  
Marine Environment ◽  
Concrete Structure ◽  
Chloride Concentration ◽  
Corrosion Damage ◽  
Internal Variable ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Damage Degree ◽  
User Subroutine ◽  
Chloride Ions Diffusion

Chloride penetration could lead to the rebar corrosion and cause the durability problem in concrete structure under marine environment. It is a coupling process between chloride penetrating and corrosion damage evolving in concrete. This paper proposed an analysis method to deal with this coupling problem. The corrosion damage degree was considered as an internal variable in coefficients of chloride diffusion. Additionally, the interfacial boundary displacement values varied with chloride concentration and service time of concrete structure. This iterative computing algorithm was tackled as user subroutine packaged into software ABAQUS. The numerical examples were given to confirm the reliability of the developed model. The results show that corrosion expanded damage accelerates chloride ions diffusion and vice versa.

scholarly journals CARBONIZATION OF CONCRETE AND CORROSION OF REINFORCEMENT OF REINFORCED CONCRETE STRUCTURES OF UNDERGROUND SEWERAGE SYSTEMS

2021 ◽  
pp. 47-56
Author(s):  
Valeriy Makarenko ◽  
Volodymyr Gots ◽  
Tetiana Khomutetska ◽  
Yulia Makarenko ◽  
Tetiana Arhatenko ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Diffusion Processes ◽  
Concrete Structures ◽  
Corrosion Damage ◽  
Exposure Period ◽  
Chloride Ions ◽  
Reinforced Concrete Structures ◽  
Term Operation ◽  
Nace Solution

The process of carbonization of concrete with different ratio of water to cement (W/C) was studied, and the influence of the environment on corrosion damage of reinforced concrete reinforcement was studied. The results of the study of carbonization of concrete on specially prepared model samples of concrete with a size of 250x250x250 mm with an exposure period in NACE solution for 500 days without external load are presented. Measurements of corrosion damage of reinforcing rods, which were placed inside concrete cubes, were performed. The method of estimating the amount of carbonization of concrete and corrosion of reinforcement is described in detail in known scientific papers. The obtained data testify to the active carbonization of concrete during the whole exposure period of the samples in NACE solution, however, concrete prepared at the ratio W/C = 0.5 and 0.6 is particularly significant in terms of carbonization intensity. Concrete with a ratio of W/C = 0.7 is less susceptible to damage. Moreover, a similar trend is observed for corrosion of fittings. This is due to the fact that the increase of the aqueous medium in the concrete mass facilitates diffusion processes of delivery to the reactive zone of chemically aggressive ingredients such as carbon dioxide, chloride ions, hydrogen, sulfur, sulfate ions, various types of bacteria and the like. The kinetics of concrete carbonization and corrosion of reinforcing bars in chemically aggressive NACE medium depending on the exposure period of the samples in the model solution was experimentally studied. It is established that with the increase of the water-cement ratio W/C from 0.5 to 0.7, the depth of carbonization and the layer thickness of corrosion products increase sharply. The flooding of the surface layers of the reinforcement and their strong embrittlement in the process of long-term operation of the reinforcement in the structure of reinforced concrete, which causes a decrease in crack resistance in general of reinforced concrete structures. The degradation of reinforcing steel during long-term operation in aggressive environments, which leads to premature corrosion damage to the reinforcement with subsequent destruction of the structure, was investigated experimentally with the involvement of high-precision metallographic equipment.

scholarly journals Mechanism analysis and model calculation of chloride ion diffusion in reinforced concrete structure

2020 ◽  
Vol 198 ◽  
pp. 01035
Author(s):  
Faqiang Yu ◽  
Weiwei Gao ◽  
Wenchao Liu
Keyword(s):  
Reinforced Concrete ◽  
Diffusion Mechanism ◽  
Concrete Structures ◽  
Chloride Concentration ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Cumulative Distribution ◽  
Reinforced Concrete Structures ◽  
Mechanism Analysis ◽  
Reinforced Concrete Structure

Chloride-induced corrosion of steel in reinforced concrete structures is one of the major causes of their deterioration over time. The analysis and research on the diffusion mechanism of chloride ions in reinforced concrete structures is still insufficient, and it is necessary to calculate the path of chloride ions based on theoretical models. In this paper, the fick’s second law was used to describe the free chloride concentration evolution in concrete. The Monte Carlo simulation was used to predict the cumulative distribution of corrosion initiation of reinforcing steel.The results show that the calculated results of the established model are in good agreement with the measured results.

Estimation of Corrosion Damage in Steel Reinforced Mortar Using Guided Waves

2005 ◽  
Vol 127 (3) ◽  
pp. 255-261 ◽  
Author(s):  
Henrique Reis ◽  
Benjamin L. Ervin ◽  
Daniel A. Kuchma ◽  
Jennifer T. Bernhard
Keyword(s):  
Reinforced Concrete ◽  
Guided Waves ◽  
Structural Integrity ◽  
Corrosion Damage ◽  
Propagation Mode ◽  
Reinforcing Steel ◽  
Reinforcing Bars ◽  
Accelerated Corrosion ◽  
Testing Method ◽  
Accelerated Corrosion Tests

Corrosion of reinforced concrete is a chronic infrastructure problem, particularly in areas with deicing salt and marine exposure. To maintain structural integrity, a testing method is needed to identify areas of corroding reinforcement. For purposes of rehabilitation, the method must also be able to evaluate the degree, rate, and location of damage. Toward the development of a wireless embedded sensor system to monitor and assess corrosion damage in reinforced concrete, reinforced mortar specimens were manufactured with seeded defects to simulate corrosion damage. Taking advantage of waveguide effects of the reinforcing bars, these specimens were then tested using an ultrasonic approach. Using the same ultrasonic approach, specimens without seeded defects were also monitored during accelerated corrosion tests. Both the ultrasonic sending and the receiving transducers were mounted on the steel rebar. Advantage was taken of the lower frequency (<250kHz) fundamental flexural propagation mode because of its relatively large displacements at the interface between the reinforcing steel and the surrounding mortar. Waveform energy (indicative of attenuation) is presented and discussed in terms of corrosion damage. Current results indicate that the loss of bond strength between the reinforcing steel and the surrounding concrete can be detected and evaluated.

scholarly journals Effect of Chloride on Electrical Resistivity in Carbonated and Non-Carbonated Concrete

2020 ◽  
Vol 10 (18) ◽  
pp. 6272 ◽  
Author(s):  
In-Seok Yoon ◽  
Chun-Ho Chang
Keyword(s):  
Electrical Resistivity ◽  
Resistivity Measurement ◽  
Chloride Concentration ◽  
Corrosion Damage ◽  
Chloride Ions ◽  
Chloride Penetration ◽  
Electrical Resistivity Measurement ◽  
Concrete Resistivity ◽  
Pore Liquid ◽  
The Relationship

The resistivity of a concrete structure exposed to chloride ions indicates the risk of early corrosion damage, because a low resistivity is related to rapid chloride penetration and to a high corrosion rate. Concrete resistivity is a geometry-independent material property that describes the electrical resistance, which is the ratio between the applied voltage and resulting current in a unit cell. The current is carried by ions dissolved in the pore liquid. While some data exist on the relationship between the moisture content and electrical resistivity of concrete, very little research has been conducted to evaluate the effect of chloride on the conduction of electricity through carbonated and non-carbonated concrete. The purpose of this study is to examine the effect of chloride concentration on the surface electrical resistivity measurement of carbonated and non-carbonated concrete. Chloride concentration had influenced the resistivity of concrete and the relationship showed a linear function. However, for concrete under the combined deterioration of carbonation and chlorides, a reduction in porosity due to the carbonation had a greater effect on the electrical resistivity than the increase in conductivity due to the chloride ions. Conclusively, this paper suggested the quantitative solution to depict the electrical resistivity of concrete with various chloride concentrations.

scholarly journals ПОШКОДЖЕННЯ ВІД ЩІЛИННОЇ КОРОЗІЇ В КОНСТРУКЦІЯХ ЛІТАКІВ ТА ЇХ ВИЯВЛЕННЯ

2019 ◽  
pp. 143-155
Author(s):  
Микола Савович Топал ◽  
Володимир Михайлович Андрющенко
Keyword(s):  
Optical Sensors ◽  
Structural Integrity ◽  
Fatigue Cracks ◽  
Corrosion Damage ◽  
Fatigue Loading ◽  
Chloride Ions ◽  
Integrated Sensor ◽  
Aluminum Ions ◽  
Internal Structures ◽  
And Control

Presented examples of destruction of aircraft designs due to corrosion of metals under conditions of fatigue loading. It is shown that slit corrosion, which is an increase in corrosion in crevice and gaps between two metals, as well as in places of untight contact of metal with a nonmetallic material resistant to corrosion, leads to the appearance of corrosion products in the joints of the skin with the power suite, which supports it , which can lead to the swelling of some elements of the joint relative to other elements and provoke the tearing off of the heads of rivets with the further development of fatigue cracks and the destruction of aircraft structures. Shown, that visual inspection is not always effective for the detection of corrosion damage, and sometimes impossible, for example, in closed internal structures. New developments in the field of sensors and equipment for the detection of corrosive substances and corrosion damage are presented. Among them is information on the sensor (organic-ceramic composite) containing the conducting complex. When the composite is exposed to water liquids, its conductivity is lost. When the composite dries, the sensor reaches its initial values of resistance. Information is provided on the optical sensor for detecting corrosion in the construction of the airframe. This sensor is based on the remote detection of aluminum ions formed during corrosion. The development of a multi-parameter integrated sensor for assessing the structural integrity of aluminum alloys, the recording of the concentration of chloride ions, the release of hydrogen, changes in humidity and degradation of the material is presented. Information is provided on fluorescence-based optical sensors used to detect specific ions such as aluminum, indicating the beginning of corrosion of an aluminum alloy. Information is provided on the development of advanced digital X-ray methods for the detection of corrosion in the design of aircraft. The conclusion is made on the necessity of combining visual control and control with the use of means and methods for detecting corrosive substances and corrosion damage.

scholarly journals Degradation Monitoring in Reinforced Concrete with 3D Localization of Rebar Corrosion and Related Concrete Cracking

2021 ◽  
Vol 11 (15) ◽  
pp. 6772
Author(s):  
Charlotte Van Steen ◽  
Els Verstrynge
Keyword(s):  
Reinforced Concrete ◽  
Degradation Mechanism ◽  
Heterogeneous Material ◽  
Corrosion Damage ◽  
Corrosion Process ◽  
Internal Damage ◽  
Rc Structures ◽  
Degradation Monitoring ◽  
Rebar Corrosion ◽  
Width Measurements

Corrosion of the reinforcement is a major degradation mechanism affecting durability and safety of reinforced concrete (RC) structures. As the corrosion process starts internally, it can take years before visual damage can be noticed on the surface, resulting in an overall degraded condition and leading to large financial costs for maintenance and repair. The acoustic emission (AE) technique enables the continuous monitoring of the progress of internal cracking in a non-invasive way. However, as RC is a heterogeneous material, reliable damage detection and localization remains challenging. This paper presents extensive experimental research aiming at localizing internal damage in RC during the corrosion process. Results of corrosion damage monitoring with AE are presented and validated on three sample scales: small mortar samples (scale 1), RC prisms (scale 2), and RC beams (scale 3). For each scale, the corrosion process was accelerated by imposing a direct current. It is found that the AE technique can detect damage earlier than visual inspection. However, dedicated filtering is necessary to reliably localize AE events. Therefore, AE signals were filtered by a newly developed post-processing protocol which significantly improves the localization results. On the smallest scale, results were confirmed with 3D micro-CT imaging, whereas on scales 2 and 3, results were compared with surface crack width measurements and resulting rebar corrosion levels.

scholarly journals Diagnosis and Assessment of Deep Pile Cap Foundation of a Tall Building Affected by Internal Expansion Reactions

Buildings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 104
Author(s):  
Fernando A. N. Silva ◽  
João M. P. Q. Delgado ◽  
António C. Azevedo ◽  
Tahlaiti Mahfoud ◽  
Abdelhafid Khelidj ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
Structural Integrity ◽  
Gas Permeability ◽  
Ettringite Formation ◽  
Dynamic Modulus Of Elasticity ◽  
Pile Cap ◽  
Deterioration Process

Early deterioration of reinforced concrete foundations has been often reported in recent years. This process is usually characterized by an extensive mapping cracking process on concrete surfaces that results from several types of Internal Swelling Reaction (ISR). In this paper, a real case study of a tall reinforced concrete building with a severe deterioration process installed in its deep foundations is discussed. Laboratory tests were performed in concrete drilled cores extracted from a deep pile cap block 19 years after the beginning of construction. Tests to assess the compressive strength, the static and the dynamic modulus of elasticity, the gas permeability, and electron microscopy scanning to find out the primary mechanism responsible for the deterioration observed during in situ inspections. Chemical alterations of materials were observed in concrete cores, mainly due to Delayed Ettringite Formation (DEF), which significantly affected the integrity and durability of the structure. Dynamic modulus of elasticity showed to be a better indicator of damage induced by ISR in concrete than compressive strength. Procedures to strengthen the deteriorated elements using prestressing proved to be an efficient strategy to recover the structural integrity of pile caps deteriorated due to expansions due to ISR.

scholarly journals Numerical Simulation of Non-Uniformly Distributed Corrosion in Reinforced Concrete Cross-Section

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3975
Author(s):  
Magdalena German ◽  
Jerzy Pamin
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Chloride Transport ◽  
Chloride Concentration ◽  
Corrosion Current ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Initiation Phase ◽  
Chloride Corrosion ◽  
Cover Thickness

Reinforced concrete structures can be strongly damaged by chloride corrosion of reinforcement. Rust accumulated around rebars involves a volumetric expansion, causing cracking of the surrounding concrete. To simulate the corrosion progress, the initiation phase of the corrosion process is first examined, taking into account the phenomena of oxygen and chloride transport as well as the corrosion current flow. This makes it possible to estimate the mass of produced rust, whereby a corrosion level is defined. A combination of three numerical methods is used to solve the coupled problem. The example object of the research is a beam cross-section with four reinforcement bars. The proposed methodology allows one to predict evolving chloride concentration and time to reinforcement depassivation, depending on the reinforcement position and on the location of a point on the bar surface. Moreover, the dependence of the corrosion initiation time on the chloride diffusion coefficient, chloride threshold, and reinforcement cover thickness is examined.

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