• Journal of the Korea Institute of Building Construction
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• v.15 no.1
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• pp.9-16
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• 2015

The goal of this research was evaluating and suggesting the solution of preventing carbonation of concrete replaced high-volume of slag. The concrete mixtures were prepared with high-volume slag and recycled aggregate, and the concrete samples were evaluated the carbonation depth with various surface treatment methods. For various surface treatment methods and surface protecting sheets, bonding strength and carbonation depth were measured. Basically, from the results, the carbonation of concrete was completely prevented with any type of surface treatment method and surface protecting sheet as far as the surface treatment materials were remained. Therefore, in this research, it was known and suggested that the easiness of handling and sufficient bonding performance was much important than the quality of surface protecting sheets.

• Journal of the Korean Society for Railway
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• v.14 no.2
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• pp.151-159
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• 2011

This study performed an experimental study for air-tightness performance evaluation of concrete tube structures with joints. The test specimens consist of a continuous concrete tube, a concrete tube with a joint in the middle, and a segmented concrete tube. The test is performed in such a way that the inner pressure of the tube is dropped down to 0.1atm and the increase of the pressure is monitored with time. An equivalent air permeability is then calculated based on the test results. The results show that, as expected, a structure with more joints or bonds tends to be less air-tight. A sensitivity study shows that the system air-tightness performance level becomes higher as either the diameter or the thickness of the tube increases. Moreover, the increase in the diameter or the thickness of the tube makes an effort to enhance the air-tightness more effective.

• Journal of the Korean Society for Railway
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• v.14 no.2
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• pp.143-150
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• 2011

This paper presents a preliminary study for air-tightness evaluation of vacuum tube structures for super-speed tube railway systems. The formula for flow rate of the air caused by the pressure difference of the inside and outside of the tube structure is derived based on Darcy's law. A test is then performed to measure the air-permeability of concrete with various compressive strengths, the result of which is used for analytical simulation of the air intrusion for a tube structure with a preliminarily defined section. It has been shown that concrete with the compressive strength of at least more than 50MPa is recommended for effective operation and maintenance of the vacuum pump systems, as the air-permeability of concrete is inversely proportional to the exponent of its compressive strength.

• Tunnel and Underground Space
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• v.20 no.6
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• pp.434-445
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• 2010

Underground compressed air energy storage (CAES) system in a lined rock cavern is considered one of the promising large-scale energy storage technologies. In this study, permeabilities of concrete lining block and its construction joint, which are the major components of an air tightness system of the undeground CAES, were measured from a model experiment. From the experiment, it was found that intrinsic permeability of construction joint was larger than that of concrete block by the order scale of $10^1{\sim}10^4$, so that it would be very important to control the quality of construction joints in-situ in order to secure air tightness of storage system. And the permeability of construction joint could be decreased as low as that of the concrete block by pasting an acryl-type adhesive on bonding surfaces. Higher degrees of water saturation of the concrete block resulted in the lower permeability, which is more preferable in the viewpoint of air tightness of storage cavern.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.3
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• pp.377-385
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• 2018

Super-speed vacuum tube system, where the air resistance is minimized to obtain high speed of the vehicle, is considered to be a viable alternative transportation system. Air-tightness is one of the most important design requirements of the system, because the internal pressure of the system needs to be maintained significantly lower than the atmospheric pressure. This study performed an experimental test, where a series of concrete tube specimens were applied by external loads to induce cracks and the effective air-permeability of the cracked tube structures were measured. The test results indicates that the information on the length and the width of the load-induced cracks are not enough to anticipate the system air-tightness, whereas the load-induced displacement has higher correlation with the systems air-tightness. Based on these results, a direction of future research for effect of the load-induced cracks on the system air-tightness is suggested.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2011.09a
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• pp.47-65
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• 2011

• Journal of the Korean Society for Railway
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• v.17 no.3
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• pp.186-192
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• 2014

In this paper, a reliability analysis is performed where the pressure change inside a concrete tube is probabilistically estimated considering the uncertainties inherent in the material and the system discontinuity. A set of uncertain quantities related to the equivalent system air permeability and the atmospheric pressure, are defined as random variables with specific distribution. The pressure change inside a concrete tube is then probabilistically described using both analytical and simulation approaches. The reliability analysis confirms that the geometric configuration of a concrete tube needs to be changed from the initial configuration obtained from the deterministic analysis.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.27-28
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• 2013

This study investigates the effect of a protective layer on the level of carbonation resistance of concrete. For the protective layer, a PE film, bubble sheets, double layered bubble sheets and styroform were placed in a mold before placing the concrete. In addition, PE film was retrofitted by attaching on the surface of the substrate concrete with a glue. Results showed that the carbonation depths of the control concrete were 4.6 mm and 5.2 mm at one week and two weeks exposure in an accelerated carbonation chamber, whereas the concrete with all types of protective layer except PE flim did not allow the ingress of carbon dioxide during the same period.

• Magazine of the Korea Concrete Institute
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• v.7 no.2
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• pp.126-135
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• 1995

Thermal cracks are occured when thermal stress due to the hydration of cement exceeds the tens~le strength of concrete. Since crackmg causes poor durability of concrete, the effect of ther ma1 cracking should be includod for the design and construction of massive concrete structures. In this study, an experiment is performed for the investigation of time dependent thermal stress history. In order to evaluate thermal stress. two methods are employed. One 1s the evaluation method of thermal stress based on the measurement from embedment stram gauge with non-stress strain gauge and the other 1s based on the measurement from concrete stress gauge. As a result of this study, the value corrected by the former shows good agreement with the latter. The validity of the proposed method for the evaluation of thermal stress 1s explored.

• 한국가스학회:학술대회논문집
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• 2003.10a
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• pp.65-72
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• 2003

현행 가스법상 지상식 LNG 저장탱크에 있어서 일정 용량의 저장탱크 주위에는 액상의 가스가 누출된 경우에 그 유출을 방지할 수 있는 방류둑(Dike) 또는 이와 동등 이상의 효과가 있는 시설을 설치하도록 규정하고 있어, 실제로 모든 지상식 LNG 저장탱크에 대해서 별도의 방류둑 설치를 의무화하고 있다. 또한, 예외규정으로 국제기준(international codes and standards)에 의해 설계되는 저장탱크는 심의를 통해 방류둑 기능을 인정할 수 있도록 하고 있다. 외국의 경우 LNG 저장탱크는 일반적으로 자국내 법령보다는 국제기준에 의해 건설됨으로써 1차 탱크로부터 일정거리의 둘레에 방류둑이 필요한 단일방호식 저장탱크 이외에 이중방호식, 완전방호식(full-containment) 및 멤브레인식(membrane) 저장탱크의 경우 외부(콘크리트, 강재)탱크가 방류둑 기능을 가지고 있어 별도의 방류둑이 필요없는 구조로 규정하고 있다. 멤브레인 LNG 저장탱크의 경우 프랑스, 일본 및 한국이 설계기술을 보유하고 있고, 최근 프랑스 및 한국에서 별도의 방류둑 없는 지상식 멤브레인 저장탱크 건설이 추진되고 있으나 양국 모두 자국법의 방류둑 규정에 의해 건설의 장애요소로 작용하고 있다. 따라서 지상식 멤브레인 LNG 저장탱크의 방류둑 기능에 대한 각 국의 법령 및 기준을 조사하고, 방류둑 일체형 저장탱크(완전방호식 및 멤브레인 저장탱크)의 형식별 안전성 평가 자료를 비교 검토함으로써 방류둑 일체형 멤브레인 저장탱크의 국내 도입의 타당성을 검토하고자 하였다. 조사결과 유럽, 미국 및 일본에서는 이중벽 LNG 저장탱크의 경우 콘크리트 외부탱크가 방류둑 기능을 가지는 것으로 규정하고 있으며, 특히 EN 1473과 제정중인 prEN 265002에서는 멤브레인 저장탱크의 경우 내부 멤브레인 탱크 누출시 단열시스템과 함께 외부 콘크리트 탱크가 액밀성 및 기밀성을 동시에 가지는 것으로 별도의 방류둑이 불필요함을 규정하고 있다. 프랑스 및 일본의 방류둑 일체형 LNG 저장탱크에 대한 위험성 평가 결과를 검토한 결과 멤브레인 저장탱크와 완정방호식 저장탱크는 안전성 차원에서 거의 동일한 것으로 나타났다. 따라서 국내에서 개발한 지상식 멤브레인 LNG 저장탱크 설계모델에 대한 안전성 제고 및 안전성 평가 등을 통해 객관적인 안전성 근거가 확보된다면 동 탱크의 경우에도 완전방호식 LNG 저장탱크와 같이 외부콘크리트 저장탱크의 방류둑 기능인정이 가능할 것으로 판단된다.