• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.257-260
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• 2006

This paper reports results of a study conducted to assess the effect of degree of corrosion of reinforcing steel bar on their mechanical properties. Reinforcing steel bars, 13mm in diameter, that were corroded by electrically accelerated corrosion method in concrete specimens were removed and tested in tension. Results indicated that the level of reinforcement corrosion influenced yield point, the tensile strength and elongation of steel bars.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.581-584
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• 2006

The durability of reinforced concrete structures is severely degraded by mainly corrosion due to seawater attack and chloride ion diffusion in concrete. The deterioration of durability causes high repair cost for maintenance of marine concrete structure. In this paper, high-durability materials for prevention of rebar corrosion are investigated to promote the durability in marine concrete structures. For these, the effect of the mineral materials addition(SF, FA and BFS), the modified steel(stainless and coating steel). and corrosion inhibitors are compared.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.458-466
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• 2023

Structures in our surroundings deteriorate over time due to environmental and chemical factors, resulting in a decrease in their performance. The primary causes of degradation in concrete structures are carbonation, salt damage, and freeze-thaw cycles. Various maintenance methods exist to address these degradation issues. However, research and technological development for existing maintenance methods have been ongoing, but the accuracy and effectiveness of repair materials and techniques have not been extensively validated. Therefore, in this study, we conducted a material performance evaluation of various manufacturers' repair materials. Based on this evaluation, we applied corrosion inhibitors and epoxy, which are the methods most closely related to crack repair, to assess the durability performance against carbonation, salt damage, and freeze-thaw cycles. The results show approximately a two-fold performance improvement against carbonation and salt damage, and a 5% enhancement in repair performance against freeze-thaw cycles. Thus, it is considered effective in preventing rebar corrosion when appropriate maintenance is carried out according to environmental and chemical factors during structural repairs.

• Magazine of the Korea Institute for Structural Maintenance and Inspection
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• v.16 no.3
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• pp.10-18
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• 2012

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.173-181
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• 2021

Reinforced concrete structures are exposed to various environments, resulting in reinforcement corrosion due to moisture and ions penetration. Reinforced concrete corrosion causes a decrease in the durability performance of reinforced concrete structures. One solution to mitigate such issues is using FRP rebars, which offer several advantages such as high tensile strength, corrosion resistance, and light-weight than conventional rebars, in reinforced concrete instead of conventional steel rebars. The FRP rebar used should be examined at the limit state because FRP reinforced concrete has linear behavior until its fracture and can generate excessive deflection due to the low elastic modulus. It should be considered while designing FRP reinforced concrete for flexure. In the ultimate limit state, the flexural strength of FRP reinforced concrete as per ACI 440.1R is significantly lower than the flexural strength by applying both the environmental reduction and strength reduction factors accounting for the material uncertainty of FRP rebar. Therefore, in this study, the experimental results were compared with the deflection of the proposed effective moment of inertia referring to the local and international standards. The experimental results of GFRP and BFRP reinforced concrete were compared with the flexural strength as determined by ACI 440.1R and Fib bulletin 40. The flexural strength obtained by the experimental results was more similar to that obtained by Fib bulletin 40 than ACI 440.1R. The flexural strength of ACI 440.1R was conservatively evaluated in the tension-controlled section.

• Steel and Composite Structures
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• v.29 no.6
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• pp.689-701
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• 2018

Corrosion of steel reinforcement is a principal cause of deterioration of RC columns. Making these corrosion-damaged columns conform to new safety regulations and functions is a tremendous technological challenge. This study presented an experimental investigation on steel-concrete jacketed corrosion-damaged RC columns. The influences of steel jacket thickness and concrete strength on the enhancement performance of the strengthened specimens were investigated. The results showed that the use of steel-concrete jacketing is efficient since the stub strengthened columns behaved in a more ductile manner. Moreover, the ultimate strength of the corrosion-damaged RC columns is increased by an average of 5.3 times, and the ductility is also significantly improved by the strengthening method. The bearing capacity of the strengthening columns increases with the steel tube thickness increasing, and the strengthening concrete strength has a positive impact on both bearing capacity, whereas a negative influence on the ductility. Subsequently, a numerical model was developed to predict the behavior of the retrofitted columns. The model takes into account corrosion-damage of steel rebar and confining enhancement supplied by the steel tube. Comparative results with the experimental results indicated that the developed numerical model is an effective simulation. Based on extensive verified numerical studies, a design equation was proposed and found to predict well the ultimate eccentric strength of the strengthened columns.

• Journal of the Korea Institute of Building Construction
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• v.17 no.2
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• pp.157-166
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• 2017

In general, carbonation and chlorine ions are the most harmful causes of deterioration of concrete structures. Recently, a method has been developed to control the corrosion of rebar in concrete containing chloride by impregnating a Surface coating material with a inhibitor. In this study, accelerated carbonation and differential thermogravimetric analysis (TG-DTA) and CASS tests were carried out to evaluate the characteristics of Surface coatings containing Organic Corrosion inhibitors which are excellent in corrosion inhibition and fix degradation causes $CO_2$ and $Cl^-$. As a result of the experiment, TG-DTA analysis and accelerated carbonation showed that $CO_2$ was directly reacted with amine derivative in concrete by the incorporation of Organic Corrosion inhibitor. In other words, $CO_2$ was immobilized and carbonation inhibition effect was confirmed. In addition, in the CASS test, the specimen coated with the Surface coating material containing the Organic Corrosion inhibitor with $Cl^-$ fixing property showed no corrosion until the 28th day and had excellent performance in preventing corrosion of a rebar by the chloride ion.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.4
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• pp.149-160
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• 2000

As systematic methodologies are required for the evaluation on the durability of reinforced concrete structure, it is necessary to study and examine every factor which deteriorates the durability of structures. This paper aims to define factors affecting rebar corrosion and to establish a basis for a prediction of serviceability, regarding a state of harmful corrosion as a state when crack begins on the surface of concrete. The study results are followings; The corrosive current has changed by types of mixture, and this property enables the evaluations of corrosion resistance by mixture and concrete cover. The specimen using AE superplasticizer has better corrosion-resistance properties than non-AE specimen, as well those having low W/C and high unit cement weight. The procedure for calculation of durable year in this study is able to use as an indicator to establish mixture factors such as unit cement weight, W/C, amount of admixture, etc.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1031-1036
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• 2000

In this study, a numerical simulation that can effectively predict the strengthening effect of repaired aged RC structures is developed using the axial deformation link elements. In repaired structures, concrete and interface are modeled as quasi-brittle materials. An elastic-perfectly plastic constitutive relationship is introduced for reinforcing bars. Also, a linear-elastic relationship for repair materials such as FRP or CFS. Structural deterioration in terms of corrosion of steel rebar is considered. The interfacial property between steel and concrete which is reduced by corrosion of steel rebar is obtained by comparing numerical results with experimental results of pull out tests. Obtained values are used in repaired reinforced concrete structures under flexural loading conditions. To investigate strengthening effect of the structures repaired with carbon fiber sheet(CFS), repaired and unrepaired RC structures are analyzed numerically. From analysis, rip-off, debonding and rupture failure mechanisms of interface between substrate and CFS can be determined. Finally, strengthening effect according to the variation of interfacial material properties is investigated, and it is shown that interfacial material properties have influence on the mechanical behavior of repaired structure systems Therefore, the developed numerical method using axial deformation link elements can use for determining the strengthening effects and failure mechanism of repaired aged RC structure.

• Structural Monitoring and Maintenance
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• v.2 no.3
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• pp.253-267
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• 2015

Corrosion has significant adverse effects on the durability of reinforced concrete (RC) structures, especially those exposed to a marine environment and subjected to mechanical stress, such as bridges, jetties, piers and wharfs. Previous studies have been carried out to investigate the corrosion behaviour of steel rebar in various concrete structures, however, few studies have focused on the corrosion monitoring of RC structures that are subjected to both mechanical stress and environmental effects. This paper presents an exploratory study on the development of corrosion monitoring and detection techniques for RC structures under the combined effects of external loadings and corrosive media. Four RC beams were tested in 3% NaCl solutions under different levels of point loads. Corrosion processes occurring on steel bars under different loads and under alternative wetting - drying cycle conditions were monitored. Electrochemical and microscopic methods were utilised to measure corrosion potentials of steel bars; to monitor galvanic currents flowing between different steel bars in each beam; and to observe corrosion patterns, respectively. The results indicated that steel corrosion in RC beams was affected by local stress. The point load caused the increase of galvanic currents, corrosion rates and corrosion areas. Pitting corrosion was found to be the main form of corrosion on the surface of the steel bars for most of the beams, probably due to the local concentration of chloride ions. In addition, visual observation of the samples confirmed that the localities of corrosion were related to the locations of steel bars in beams. It was also demonstrated that electrochemical devices are useful for the detection of RC beam corrosion.