• Journal of the Korea Institute of Building Construction
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• v.14 no.4
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• pp.359-368
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• 2014

Photocatalytic cement has been receiving attention due to its high oxidation power that reduces nitrogen oxide, thus contributing to a clean atmospheric environment. However, there has not yet been a thorough investigation on the effect of photocatalytic reactions on the durability of cementitious material, the parent material. In this study, photocatalytic cement samples were exposed to nitric oxide gas and UV along with cycles of wetting and drying to simulate environmental conditions. The surface of samples was characterized mechanically, chemically, and visually during the cycling. The results indicate that that the photocatalytic efficiency decreased with continued NO oxidation. The pits found from SEM indicated that chemical deterioration, such as acid attack or leaching, did occur. However, this was not confirmed by X-ray diffraction. The hardness was not affected, probably due to the formation of CSH as evidenced by the XRD pattern. In conclusion, it was found that photocatalysis could alter cementitious materials both chemically and mechanically, which could further affect long-term durability.

• Journal of the Korean housing association
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• v.17 no.2
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• pp.19-26
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• 2006

Building would be deteriorated with time elapse, influenced by its geographic situation, climate and other environmental conditions. In addition, the systematic maintenance could be provided to keep the resident a recent living condition. The existing breakdown maintenance will be changed into the preventive maintenance. The preventive maintenance is required to get the repair time, the repair scope and frequency. In this paper, it aimed at providing the repair time range over the building components, utilizing the relation between the determination curve and the performance recovery through repair. Results of this study are as follows : First, the forecast of the repair time over the building components could be calculated and equalized with the deterioration and performance degree. Second, the repair time range of building components would be provided into five categories and 3rd repair time. Results of this study will set up the long-term repair plan of building, and finally keep an housing condition comfortable.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.6
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• pp.780-785
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• 2014

To assess the deterioration condition of stator insulation, diagnostic and AC dielectric strength tests were performed on five high voltage (HV) motors (2,000 HP, 6.6 kV) for boiler feed-water pump (BFP). Two HV motors for BFP were installed per unit. Following the long term rewinding program, the diagnostic test was performed on five 6.6 kV motors during the planning maintenance period. After completing diagnostic test, AC dielectric strength test was done on the stator windings of HV motors. The AC dielectric strength test was conducted at 15 kV for one minute. Dielectric strength test and diagnostics test results confirmed that the stator insulation was judged to be in serviceable condition in the five 6.6 kV motors.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.157-160
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• 2004

If concrete structure is exposed to high temperature such as long-term fire, damages affecting partial or whole structure system may occur. Therefore accurate diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary. Especially, the amount of fire damage done to concrete depends on the materials, the standard design compressive strength of concrete, and heated temperature. So, the object of this study is to present data for supposed heated Temperature of deteriorated concrete by fire.

• Computers and Concrete
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• v.23 no.2
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• pp.107-119
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• 2019

In-service reinforced concrete structures are simultaneously subjected to a combination of multi-deterioration environmental actions and mechanical loads. The combination of two or more deteriorative actions in environments can potentially accelerate the degradation and aging of concrete materials and structures. This paper reviews the coupling and synergistic mechanisms among various deteriorative driving forces (e.g. chloride salts- and carbonation-induced reinforcement corrosion, cyclic freeze-thaw action, alkali-silica reaction, and sulfate attack). In addition, the effects of mechanical loads on detrimental environmental factors are discussed, focusing on the transport properties and damage evolution in concrete. Recommendations for advancing current testing methods and predictive modeling on assessing the long-term durability of concrete with consideration of the coupling effects are provided.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.31-32
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• 2020

Concrete changes its internal moisture distribution depending on the external environment, and changes in the condition of the material's interior over time affect the performance of the concrete. These effects are closely related to the long-term behavior and durability of concrete, and the degree of deterioration varies from climate to climate in each region. In this study, we use actual climate data from each region with distinct climates. A multi-physical analysis based on the method was conducted to predict the difference and degree of deterioration rate by climate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.258-259
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• 2019

Corrosion of rebar in RC structures, which results in premature deterioration of reinforced concrete structures, is a very serious problem. Most corrosion monitoring and sensing technologies require some type of wired or wireless connection between the sensor and monitoring electronics. This causes significant problems in their installation and long-term use. In this paper we describe a corrosion monitoring technology of rebar in reinforced concrete structures. Especially, it is emphasize that the development of sensors and monitoring system not only occurrence of rebar corrosion but also penetration of deterioration factor such like chloride ion and carbon dioxite etc..

• Earthquakes and Structures
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• v.25 no.1
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• pp.69-78
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• 2023

Life-cycle performance analysis of a reinforced concrete box section bridge was generated. Moreover, Monte Carlo simulation with important sampling (IS) was used to simulate the bridge material and load uncertainties. The bridge deterioration model was generated with the basic probabilistic principles and updated according to the measurement data. A genetic algorithm (GA) with the response surface model (RSM) was used to determine the deterioration rate. The importance of health monitoring systems to sustain the bridge to give services economically and reliably and the advantages of fiber-optic sensors for SHM applications were discussed in detail. This study showed that the most effective loss of strength in reinforced concrete box section bridges is corrosion of the reinforcements. Due to reinforcement corrosion, the use of the bridge, which was examined, could not meet the desired strength performance in 25 years, and the need for reinforcement. In addition, it has been determined that long-term health monitoring systems are an essential approach for bridges to provide safe and economical service. Moreover the use of fiber optic sensors has many advantages because of the ability of the sensors to be resistant to environmental conditions and to make sensitive measurements.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.41-42
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• 2012

High temperature / high pressure spray equipment using a conventional method, unlike spray polyurea adjustable pot life and yellowing caused by UV light and chemicals do not occur, or discoloration of Self-Leveling Type of rugged hand-polyurea resin for technology development is underway. This new concept of polyurea resin roller, brush, airless spray, and they installed easily using the unfamiliar labor, and curing time of approximately four hours to gain control of the glass because it is Pot. Construction, but does not like the spray polyurea resin, compared to the existing degradation of the adhesion strength is concerned. In this study, Self-Leveling Type Manual of polyurea resin adhesion strength of target deterioration Let's minimize problems by reviewing existing domestic and infrastructure long-term durability for long life of the facility is to obtain.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.557-564
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• 2004

This paper introduces a study carried out to investigate sodium sulfate attack caused by various reactive products. Experiments were performed on mortar and paste specimens made with ordinary Portland cement (OPC) conforming to KS L 5201 Type I. The water-cement ratios were varied from 0.35 to 0.55. It was found from the laboratory study that the water-cement ratio may be a key to control the deterioration of OPC matrix during sodium sulfate attack. Furthermore, X-ray diffraction (XRD) confirmed that ettringite, gypsum and thaumasite were the main products formed by sodium sulfate attack. These findings were well supported by thermal analysis through differential scanning calorimetry (DSC), and confirmed the long-term understanding that deterioration mechanism by sodium sulfate attack is a complicated process. Most importantly, deterioration due to sodium sulfate attack is characterized as the drastic reduction in compressive strength as well as the expansion (especially in cement matrix with a higher water-cement ratio).