• Architectural research
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• v.7 no.2
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• pp.81-89
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• 2005

Over the years, existing bridges have had various degrees of maintenance to extend the service life. As the existing bridges continue to deteriorate, however, each Department of Transportation (DOT) of the United States of America faces increasing demands on the limited funds available for bridge maintenance. Therefore, it is very important for State Department of Transportations to establish Maintenance, Repair, and Rehabilitation (MR&R) strategies for bridge structures such that funds get allocated for appropriate maintenance over the service life. This paper identifies the state-of-art and the state-of-practice of MR&R actions and the use of MR&R strategies in concrete bridge decks. In addition, a questionnaire survey was conducted to identify the type and timing for MR&R actions as well as existing MR&R strategies taken in concrete bridge deck by each DOT. This paper also presents the results of the survey.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.323-327
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• 1996

Reinforced concrete(R/C) structures need repair and rehabilitation due to the deterioration such as a crack, spalling and disintergration. Numerous repair materials which are currently used in construction fields without any regulation are examined in terms of their serviceabilities and effectiveness. In this paper section of existing R/C beams are enlarged with repair materials, that is, epoxy, latex or premix. And then they are strengthened with rebar, steel poate of CFRP on the tension face. Structural behaviors of strengthened beams are investigated both statically and dynamically and they are compared with each. This paper summarizes the overall research plan.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.1017-1022
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• 2003

The hydraulic structures such as aqueduct tunnels and the drainage canal of the hydroelectric power plant in Japan are almost old. Therefore, the concrete surface of the aqueduct tunnel has received damage by wear-out and the crack, etc. This study was to develop repair mortar mixed a coal ash coarse powder by using two kinds of high early strength cements. As a result, the repair mortar was obtained by substituting the EF cement (maid in Japan) and the MT cement (maid in South Korea) at a rate of 60:40, and substituting the coal ash 30% and the mixing rate 35% of the artificial aggregate for natural fine aggregate.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.1235-1240
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• 2005

In this status no inspection standard of quality in repair of present concrete structure has a problem to repair for simple experience. In this paper for this problem improvement, it made an analysis of relation to injection quantity of crack width, injection time of crack width, injection pressure of crack width, injection pressure and time, injection quantity of structural size, injection quantity of structural individual crack position, injection time about crack width. and structural thickness. The data gained in analysis result be judged that it will help in systematic quality control about concrete structural repair.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.625-628
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• 2006

In this study, the beam which is repaired as high toughness cementitious composites evaluated on flexural performance. As for the test results, it was found that high toughness performance of beams of the repair as high toughness cementitious composites showed more better than the existing repair method and demonstrated about 95% semi-reinforcement to compare with reinforcement of carbon fiber sheets of one layer without interface and brittle failure. Therefore, appling on using PVA fiber reinforced high toughness cementitious composites, the repaired concrete structures can be increased to flexural performance.

• Journal of the Korea Concrete Institute
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• v.11 no.6
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• pp.89-100
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• 1999

Service life of concrete structures that are exposed to the environmental attack is largely influenced by the corrosion of reinforcing bare due to the chloride contamination. Chloride ions penetrate continuously into concrete from the environment, and chloride diffusion velocity is governed by a mechanical steady stage. In this study, a method is developed to predict corrosion initiation of reinforcing bars in the sea-shore structures, based on governing equations that take into account the diffusing of chloride ions and a mechanical steady state. As a result of this study, Corrosion Prediction System (CPS) is developed, and it can be used to determine an optimal time for repair and rehabilitation actions need to be taken. Futhermore, CPS assists the concrete mixing structures by predicting of chloride concentrations in concrete mixture, exposed to salt concentrations and service environment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.1 no.1
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• pp.125-132
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• 1997

This study was intended to investigate the effects of epoxy grout on compressive strength for damaged concrete structures. For this purpose, concrete molds were manufactured and tested for compressive strength at 28 days after water curing. Two kinds of Korea-made and one Japan-made epoxy grouts were injected into the broken concrete molds with the automatic low-pressure injecting method or the hand injecting method.

• Smart Structures and Systems
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• v.7 no.5
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• pp.329-348
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• 2011

Large-scale earthquakes pose serious threats to infrastructure causing substantial damage and large residual deformations. Superelastic (SE) Shape-Memory-Alloys (SMAs) are unique alloys with the ability to undergo large deformations, but can recover its original shape upon stress removal. The purpose of this research is to exploit this characteristic of SMAs such that concrete Beam-Column Joints (BCJs) reinforced with SMA bars at the plastic hinge region experience reduced residual deformation at the end of earthquakes. Another objective is to evaluate the seismic performance of SMA Reinforced Concrete BCJs repaired with flowable Structural-Repair-Concrete (SRC). A $\frac{3}{4}$-scale BCJ reinforced with SMA rebars in the plastic-hinge zone was tested under reversed cyclic loading, and subsequently repaired and retested. The joint was selected from an RC building located in the seismic region of western Canada. It was designed and detailed according to the NBCC 2005 and CSA A23.3-04 recommendations. The behaviour under reversed cyclic loading of the original and repaired joints, their load-storey drift, and energy dissipation ability were compared. The results demonstrate that SMA-RC BCJs are able to recover nearly all of their post-yield deformation, requiring a minimum amount of repair, even after a large earthquake, proving to be smart structural elements. It was also shown that the use of SRC to repair damaged BCJs can restore its full capacity.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.671-676
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• 2001

Reinforcement corrosion is major problem for those who own and maintain reinforced concrete structures exposed to chlorides. It is well understood that the form of corrosion is more problematic than corrosion found elsewhere, Because concrete has no apparent signs that there is anything amiss until the process of deterioration is relatively far advanced. The objective of this research is to develop the ladder system which monitors the corrosion of reinforcing steels in concrete. This system can be used to assess the corrosion condition and corrosion rate of steel in concrete, which can give timely repair and strengthening of steel in concrete structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.79-88
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• 2007

Concrete structures undergo degradation of durability performance and it generally propagates to the structural problems. Recently. a lot of materials for surface protection for concrete are developed, however, performance is not clearly improved due to the difficulties such as repair construction technique and quality of materials for repairing. In this study, liquid inorganic impregnant for concrete structures is developed and durability performance for impregnated concrete specimens is carried out. Furthermore, the performances of the concrete specimens with developed impregnant is also compared with those of the specimens with impregnant conventionally used. Additional CSH gel is formed through the reaction of calcium hydroxide ($Ca(OH)_2$) and impregnant with silicate. As a result of the reaction, impregnated concrete is evaluated to have more denser surface and resistance to deterioration. Finally it is experimentally verified that the concrete specimens with developed impregnant show better durability performance than normal specimens and those with conventional impregnant.