• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.47-48
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• 2023

Reinforced concrete structures are an integrated structure in which reinforcing bars are placed on the tensile side of the beam to compensate for concrete that is strong in compression but weak in tension, so that the concrete receives compressive force and the reinforcing bars receive tensile force. It is durable, fire-resistant, economical, and adapts to the shape and dimensions of the structure. It has been widely used for a long time because it can be made freely without restrictions. However, reinforced concrete structures have the disadvantage that cracks occur easily, so they are repaired using a cross-sectional construction method. During this process, problems such as the repair part falling off occurred, so in order to solve the problem, stress changes due to changes in the size of the repair part were examined. As a result, based on the elastic modulus ratio of 1.0, the stress tended to increase as the size of the repair part decreased when it was less than 1.0, and the opposite tendency was seen when it was more than 1.0. This is believed to be due to an increase in the area of the part with a large elastic modulus.

• Journal of the Korea Institute of Building Construction
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• v.6 no.2 s.20
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• pp.91-98
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• 2006

The purpose of this study is to investigate the problem of crack repair materials and methods in existing concrete structure and to propose the effective injection method on crack repair by packer type. The result of this study is as follows. It is investigated that the crack width in the inner matrix of concrete structure is decreased about 30-40% than that in the sulfate of the concrete structure. Also it is showed that the possibility which could be monolithic with injection part became higher if the injection part if installed near to surface of concrete on the punching method to vertical direction against crack area. The injection of repair material can be poured smoothly under about $10N/mm^2$ pressure on the condition that cracks are monolithic with injection part without dust by drill. The effective method to pour the injection repair material is the punching method by coredrill but several research to minimize injection pressure should be continually.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.539-541
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• 2005

The purpose of this study is to accurately understand the flexural behavior in RC beam with strrup on repair thickness of DFRCC. Using a four-point bending test, the shear strengths and shear stress-deflection relations of DFRCC repair RC specimens are obtained. The results show that DFRCC can be effectively used for repairing materials for concrete structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.397-400
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• 2006

Most of the civil structures in Korea and abroad have many kinds of damages when they are facing over-loaded traffics, long-term serviceability, and severe environmental conditions. Repair, rehabilitation, and retrofit are important for maintaining the serviceability of structures. In recent year, VES-LMC has been widely used as repair material for bridge deck repair and rehabilitation, because the VES-LMC has a various benefits such as traffic opening after 3 hours of curing, higher durability and bond strength. In case of any structure repaired or rehabilitated with VES-LMC, those were influenced capacity of bond between the base layer of slab and VES-LMC as well as physical properties of each other materials. The capacity of bond depended on purity of interface, micro cracks, curing of VES-LMC and so like. A kind of popular concrete repair technique, High pressure water jetting equipment is extremely efficient at removing damaged concrete. Removing damaged or poor quality concrete from sensitive structures such as bridge, tunnels, multi-story car parking decks and runways, using the high pressure water jetting could remove damaged or poor quality concrete remaining healthy and sound concrete. Accordingly, the purpose of this study is that it was to evaluate effect of hydrodemolition on the bond strength of VES-LMC overlay compared with effects of other method such as breaker, untreated. Also, it was evaluated the effect of surface moisture.

• Structural Engineering and Mechanics
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• v.82 no.3
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• pp.343-354
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• 2022

An understanding of the mechanism of concrete girders repaired with CFRP plates and its influence on the dynamic parameters is presented in this paper. Dynamic parameters are governed by the relationship with the physical properties of concrete girders and CFRP plates as well as the adhesive layer between them. A brief explanation of the mechanism of the composite action of concrete girders repaired with CFRP is also given in this paper. Experimental work was carried out to validate the theory of the composite action. The results show a decrease in the modal parameters of CFRP repaired girders that were turned over during the repair procedure, which contrasts with the proven static-based results that CFRP plates increase the stiffness of repaired girders. The composite action theory has explained the results based on the tension and compression forces' growth at the adhesive layer between the CFRP plates and girder surface during the repair procedure. Other girders were prepared and repaired without turning over in order to avoid tension and compression forces at the adhesive layer. The experimental results show an increase in the dynamic parameters of CFRP repaired girders that were not turned over during the repair procedure, which aligns with the static-based results. The study concludes that the dynamic parameters are excellent indicators for the assessment of CFRP repaired concrete girders. The study also suggests that researchers should not turn over damaged concrete girders to repair them with CFRP plates if they intend to study the dynamic parameters, in order to avoid the proposed composite action effect on modal parameters.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.343-346
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• 2003

Confirmation of a damage degree and repair about a damage part are very hard for an underwater structure. And quality control of a construction is very complicated even if repair work is carried out on a damaged structure because repair work is carried out in water. If repair work is carried out while a defect part of the structure which there is in water keeps dry state, a efficient of repair is maximized. However, as for the repair technology about an underwater structure, a systematic researcher is not enough because of the environmental trouble. And, as for the effect about repair method to be applied to a currently underwater structure, it is not certainly proved. In this study The repair work of an underwater structure damaged applied the method that used a fiber panel form work. And a efficient of structure repaired was evaluated.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.571-578
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• 1997

In the repair and repair works, epoxy resins are widely used as repair materials. The successful concrete repairs and retrofit works depends on the quality of the repair and retrofit materials. Although many materials for the repairs and retrofit have been developed in many contries, information on the repair methods are somewhat limited. Futhermore, the repairs and retrofit methods are also largely dependent on those froms in other developed contries, it is necessary to initiate rather fundamental repair-related research. The purpose of this study is to investigate th physical and mechanical properties of epoxy resin which is commonly used in repairing concrte crack in RC structures. The basic physical properties such as specific gravity, gel point and shrinkage ratio as well as the mechanical properties such ad the tensile and compressive strength, elastic modulus were acquired by the standard test method (KS code). For the test results, the great deviations of physical and mechanical properties among the test materials were discovered and is, therefore, recommended that careful attentions should be give in selecting the epoxy resin by considering the characteristics of the repair materials and repair works.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.1
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• pp.9-20
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• 2023

For highway concrete structures, the deterioration of the structure is accelerated due to the increase in the use of deicing materials, and sectional repair work is being frequently carried out to restore performance. However, after the repair work, re-damage such as cracks, delamination, and poor bond performance is exhibited in the repaired sectional area. In this study, overseas repair material requirements were first analyzed, and present domestic requirements were improved repair material performance through field surveys of common concrete structures, laboratory experiments, and test construction on a disused concrete bridge. In addition, performancebased quality requirements were presented so that all materials that meet the required performance can be applied, and different test methods for each material were unified into concrete test methods for consistent test results analysis. The considered performance requirements were compression strength, bending strength, and bond strength for structural properties, and length change rate, crack resistance, thermal expansion coefficient, and elasticity coefficient were for dimensional behavior. For resistance to chloride penetration resistance and freeze-thaw resistance were presented as durability. The proposed requirements for concrete repair materials are expected to contribute to the improvement of the quality of concrete sectional repair work in Korea.

• Computers and Concrete
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• v.9 no.2
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• pp.99-118
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• 2012

Marine Structures are very costly and need a continuous inspection and maintenance routine. The most effective way to control the structural health is the application of an expert system that can evaluate the importance of any distress on the structure and provide a maintenance program. An extensive literature review, interviews with expert supervisors and a national survey are used to build a decision support system for concrete structures in sea environment. Decision trees are the main rules in this system. The system input is inspection information and the system output is the main cause(s) of distress(es) and the best repair method(s). Economic condition, severity of distress, distress situation, and new technologies and the most repeated classical methods are considered to choose the best repair method. A case study demonstrates the application of the developed decision support system for a type of marine structure.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.337-340
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• 2006

Utilize several kinds of reinforcement fibers to control workability and surface crack in occasion of mortar used in dilapidated concrete section repair public law. Polypropylene or poly vinyl alcohol that is hydrophilic fiber etc. is used much usually with this reinforcement fiber. Reinforcement fiber does important action that control crack that enhances coherence between material and happens at dry contraction. In this study, wished to use Sepiorite that inorganic materials and affinity such as cement are excellent nature inorganic world fiber and improve repair mortar performance. In this study, as reinforcement fiber, wished to grasp physical characteristics that uses Sepioraiteu and happens this time and grasp application possibility of concrete's repair mortar.