• Journal of the Society of Disaster Information
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• v.11 no.2
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• pp.253-261
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• 2015

Deterioration of reinforced concrete structures in corrosive environment is tend to be accelerated due to ingress of aggressive ion such as chloride ion. Chloride-induced corrosion is affected by various factors such as cover concrete qualities, width of existing cracks, and cover depth of concrete. However, the allowable crack width of RC structure in design code does not consider the concrete material properties and conditions of construction except the cover depth. In this paper, an equation for allowable crack width is proposed to consider the cover concrete quality, crack width, and cover depth. Crack width, cover depth, and water-cement ratio of concrete are selected as influencing factors on corrosion of reinforcement for rapid chloride tests. From test results, the relationships between the factors and corrosion are derived. Finally, the equation for allowable crack width is derived in terms of concrete compressive strength and cover depth. The presented equation is verified by comparative calculations with design code variables.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.681-687
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• 2008

This study presents a technique to quantitatively measure the corrosion level of a reinforcing bar using infrared thermography system. We found out electric heating method having an important effect on thermal data in previous study. This study purposed an efficient way for grip standardization to reduce constriction resistance problem, and providing reliable thermal data using infrared thermographic method. Using vise type earth clamp, the surface resistance of rebar was smaller than that of traditional plier type earth clamp through temperature-distribution relationship. Also this study contains experiments with toque wrench to improve heating contact problem.

• Journal of the Korean Society for Railway
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• v.16 no.6
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• pp.466-472
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• 2013

The use of a concrete track is gradually growing in urban and high-speed railways in many part of the world. The resilient pad, which is essentially when concrete tracks are used, plays the important role of relieving the impact caused by train loads. The simple fatigue test[1] to estimate the variable stiffness of resilient pads is usually performed, but it differs depending on the practical conditions of different railways. In this study, the static stiffness levels of used resilient pads according to passing tonnages levels were measured in laboratory tests. Also, the simple fatigue test and the multi-stress accelerated degradation test for new resilient pads were performed in a laboratory. The static stiffness of the used pad was compared with the results of tests of usage times and cycles. The results of the comparison showed that the variable static stiffness levels of the used pad were similar to results of the multi-stress accelerated degradation test considering the fatigue and heat load. With a T-NT equation related to the degree of the multi-stress accelerated degradation, a model of multi-stress accelerated degradation for a resilient pad was devised. It was found through this effort that the total acceleration factor was approximately 2.62. Finally, this study proposes an equation for a multi-stress accelerated degradation model for polyurethane resilient pads.

• Journal of the Korean Institute of Educational Facilities
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• v.4 no.3
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• pp.5-14
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• 1997

The purpose of this study is to present basic data in order to improve the efficiency and the objectivity of diagnosing educational structures built with the reinforced concrete. For achieving the purpose, this paper, firstly, researches damage aspects of 22 public educational of facilities in Seoul, and summarizes the results of that research. Through the analysis and the evaluation of damage aspects, this paper shows the conclusions as follows; (1) Main damage to reduce structural capacities of building is the differential settlement. (2) Though the steel corrosion is occurred by several factors, the main cause is the faulty construction. (3) To prevent the damage development, a proper repair strategy is very important.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.10a
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• pp.350-354
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• 2005

본 연구에서는 건설폐기물에 포함되어있는 폐콘크리트를 사용하여 $200^{\circ}C,\; 300^{\circ}C,\;400^{\circ}C,\;500^{\circ}C$로 각 온도에 따라 열화 처리한 후 분쇄하여 시멘트 페이스트 분리량과 골재의 물리적 특성을 파악하였다. 열화 처리의 온도가 높아질수록 시멘트 페이스트의 분리율은 높아졌으며, 압축강도는 낮아지는 경향을 보였다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.146-147
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• 2016

Concrete has been recognized as a material which is resistant to high temperatures, but chemicophysical property of concrete is changed by the high temperature. So, mechanical properties of concrete may be reduced. So, concrete at high temperature is evaluated mechanical properties for safety inspection. However, research of ultrasonic method is not much. Therefore, the purpose of this study is to NDT(non-destructive test) of 30, 70, 110MPa concrete exposed high temperature using ultrasonic pulse velocity.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.38-39
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• 2021

Recently, 67% of defect and tenant lawsuits were identified as leaks due to cracks. In particular, when the final finish of the roof of a building is designed with base concrete, complex deterioration occurs due to the harsh environment such as shrinkage and expansion due to external temperature changes, freezing and thawing, and the use of calcium chloride due to snow accumulation. Therefore, it is intended to secure long-term durability by reducing cracks in the base concrete by using waste fibers, which are industrial by-products.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.146-147
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• 2021

In this study, the deterioration of concrete subjected to high temperature was evaluated using harmonics. When concrete is exposed to high temperatures, its mechanical properties deteriorate. In order to evaluate this deterioration, a method of analyzing the waveform of elastic waves was applied. As the heating temperature increased, the fundamental wave of the 50 kHz elastic wave passing through the concrete decreased. In addition, harmonics were generated at each temperature, and the higher the heating temperature, the greater the ratio of harmonics. The higher the compressive strength, the greater the amplitude of the fundamental wave, and this phenomenon is thought to be due to the internal structure of concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.267-268
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• 2023

Out of an estimated 7 million buildings nationwide, approximately 38% of them have been standing for over 30 years, and this number is expected to continue to increase. Additionally, due to the Building Act, safety inspections will be mandatory for approximately 70,000 buildings annually, leading to an increase in demand for building safety inspections. However, the current building safety diagnosis heavily relies on manpower, making it difficult to diagnose locations that are hard to access, and requiring lengthy investigation periods. Therefore, this paper presents the basic research results of a non-contact concrete damage depth estimation technique using laser technology aimed at remote building safety diagnosis and shortening investigation periods.

• Magazine of the Korea Concrete Institute
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• v.18 no.5 s.94
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• pp.73-82
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• 2006

다양한 조인트를 갖도록 제작된 콘크리트 실험체내 철근의 부식에 대한 상세한 조사가 이루어졌다. 실험체들은 25년 동안 조수간만대에 노출되었다. 몇몇 실험체들은 25년 후에 가속챔버내에서 보다 가혹한 열화환경에 노출되었다. 실험항목은 부착강도, 중성화깊이, 염분농도, 부식의 전기화학적, 물리적 측정, 그리고 조인트부 생성물이다. 에폭시나 라텍스 페이스트로 처리된 조인트면을 제외하고 조인트면에 자동생성되는 생성물은 콘크리트 내 철근의 부식을 막는다. 철근과 콘크리트 계면에서의 공극은 국부부식의 주원인이다. 조인트 표면의 레이탄스 제거가 조인트면의 중성화 깊이를 줄인다. 레이턴스 제거 후 모르타르 코팅처리가 라텍스 페이스트나 에폭시코팅처리에 비해 가장 작은 중성화 깊이를 보인다. 레이턴스 제거후 에폭시코팅처리는 가장 강한 부착력을 갖지만 절점부 콘크리트 내 철근부식 방지에는 가장 우수한 성능을 보이지 못한다.