• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.401-404
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• 2008

균열은 콘크리트에 염소이온과 같은 유해한 물질의 침투경로가 되어 내구성에 심각한 열화를 야기한다. 따라서 고내구성 재료를 사용한 콘크리트 휨부재에서의 균열 발생에 따른 염소이온 침투특성을 검토하고자 하였다. 이를 위해, 고내구성 재료를 적용한 보에 하중을 가하여 휨균열을 도입시키고, 촉진 염화물 침투실험(RCPT)과 장기 염화물 침투실험을 실시하여 염화물 침투 특성을 파악하였다. 실험결과에 따르면, 고내구성 재료를 적용한 부재는 균열이 발생하여도 일반 콘크리트 부재에 비해 높은 염화물 침투 저항성을 보였다. 특히 고로슬래그 미분말을 적용한 경우, 균열 부재의 장기 염화물 침투 실험에서 탁월한 염화물 침투 저항성을 보였다.

• 한국건축시공학회지
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• 제13권2호
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• pp.139-147
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• 2013

The purpose of this study was to investigate the durability performance of concrete that includes rice husk ash. Chloride diffusion coefficient obtained through a rapid chloride penetration test and depth of $CO_2$ penetration obtained through a rapid carbonation test were used to evaluate latent durability. Durability characteristics for rice husk ash replacement and age were determined. Through the experiment, it was found that when the replacement ratio of rice husk ash was increased from 0% to 10%, the compressive strength of concrete containing rice husk ash was similar to that of concrete containing silica fume. This shows that the durability performance of concrete containing rice husk is excellent compared to other concretes containing admixtures.

• Computers and Concrete
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• 제6권5호
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• pp.391-401
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• 2009

This paper presents a study of the strength and chloride penetration of blended Portland cement mortar containing ground palm oil fuel ash (POA) and ground river sand (GS). Ordinary Portland cement (OPC) was partially replaced with POA and GS. Compressive strength, rapid chloride penetration test (RCPT) and chloride penetration depth of mortars were determined. The GS only asserted the packing effect and its incorporation reduced the strength and the resistance to chloride penetration of mortar. The POA asserted both packing and pozzolanic effects. The use of the blend of equal portion of POA and GS also produced high strength mortars, save cost and excellent resistance to chloride penetration owing to the synergic effect of the blend of POA and GS. For chloride depth, the mathematical model correlates well with the experimental results. The computer graphics of chloride depth of the ternary blended mortars are also constructed and can be used to aid the understanding and the proportioning of the blended system.

• 한국항해항만학회지
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• 제34권10호
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• pp.787-792
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• 2010

콘크리트는 물시멘트비에 상응하는 공극을 가지게 되며, 공극을 통한 염소이온의 확산을 평가하기 위하여 해안가 폭로 및 해수 침지실험이 널리 사용된다. 이상의 실험은 경우에 따라서 다년간의 시간을 요하는 경우도 있어, 최근에는 전기 영동법에 기초한 급속 염소이온 확산시험을 실시하는 경우가 많으나, 그 값이 폭로 및 침지 시험에서 얻은 값과 상이한 경우가 많아 데이터의 실용성을 높이기 위하여 그 원인 규명이 절실한 실정이다. 본 연구에서는 평가 방법으로써 Nernst-Einstein의 식을 통한 염화물 이온 이동계수의 산정방법을 사용하였으며, NT BUILD 492법 및 해수 침지실험을 통한 확산 특성과 비교하여 값의 차이에 대하여 고찰하였다. 그 결과 실험인자의 변화가 염소이온 확산에 미치는 영향은 미비한 것으로 평가되어져 실험조건에서 발생하는 영향은 거의 없는 것으로 규명되었으며, NT BUILD 492법과도 거의 동일한 값이 구해졌다. 침지실험 결과와의 상이는 염소이온 확산에서 경계조건의 차이 및 염소이온의 시멘트 수화물과의 고정화에 의한 것으로 판단되어진다.

• Advances in concrete construction
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• 제7권2호
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• pp.75-85
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• 2019

The present study is focused on the mechanical and durability properties of ternary blended cement concrete mix of different grades 30 MPa, 50 MPa and 70 MPa. Three mineral admixtures (fly ash, silica fume and lime sludge) were used as a partial replacement of cement in the preparation of blended concrete mix. The durability of ternary blended cement concrete mix was studied by exposing it to acids HCl and $H_2SO_4$ at 5% concentration. Acid mass loss factors (AMLF), acid strength loss factor (ASLF) and acid durability factor (ADF) were determined, and the results were compared with the control mix. Chloride ions penetration was investigated by conducting rapid chlorination penetration test and accelerated corrosion penetration test on control mix and ternary blended cement concrete. From the results, it was evident that the usage of these mineral admixtures is having a beneficiary role on the strength as well as durability properties. The results inferred that the utilization of these materials as a partial replacement of cement have significantly enhanced the compressive strength of blended concrete mix in 30 MPa, 50 MPa and 70 MPa by 42.95%, 32.48% and 22.79%. The blended concrete mix shown greater resistance to acid attack compared to control mix concrete. Chloride ion ingress of the blended cement concrete mix was low compared to control mix implying the beneficiary role of mineral admixtures.

• 한국안전학회지
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• 제18권4호
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• pp.105-109
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• 2003

Structure surfaces damaged due to many causes are repaired by several special mortars. But wide studies about the permeability of these mortars were rarely conducted. In this study compressive strength test, flexural strength test and bond strength test of these mortars were conducted. And chloride ion penetration test was also conducted to explore the permeability charcteristics of selected repair mortars. This test was carried out following the standard ASTM C1202-91. Colouriemtric penetration depth can be drawn from these test results using a relationship equation between colourimetric penetration depth and charge passed which C. Andrade suggested. Diffusion coefficient can be calculated by CTH rapid method. To the end, the present study can provide a firm base for the application of repair mortars to concrete structures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.635-640
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• 2001

In this study, a mathematical model is established for prediction of chloride penetration in unsaturated cracked early-age concrete. The model is combined with models for thermo-hygro dynamic coupling of cement hydration, moisture transport and micro-structure development. Chloride permeability and water permeability at cracked early-age concrete specimens are evaluated using a rapid chloride permeability test and a low-pressure water permeability test, respectively. Then, a homogenization technique is introduced into the model to determine equivalent diffusion coefficient and equivalent Permeation coefficient. Increased chloride transport due to cracks at the specimen could be predicted fairly well by characterizing the cracks using proposed model. Proposed model is verified by comparing diffusion analysis results with test results.

• Structural Engineering and Mechanics
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• 제47권5호
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• pp.701-711
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• 2013

People started to replace natural aggregate with recycled aggregate for a number of years due to disposal problem and certain other potential benefits. Though there are number of drawbacks with use of recycled aggregates like lesser modulus of elasticity, low compressive strength, increase in shrinkage, there are results of earlier studies that use of chemical and mineral admixtures improves the strength and durability of recycled concrete. The use of recycled aggregate from construction and demolition wastes is showing prospective application in construction as alternative to natural aggregates. It conserves lot of natural resources and reduces the space required for the landfill disposal. In the present research work, the effect of recycled aggregate on strength and durability aspects of concrete is studied. Grade of concrete chosen for the present work is M50 (with a characteristic compressive strength of 50 MPa). The recycled aggregates were collected from demolished structure with 20 years of age. Natural Aggregate (NA) was replaced with Recycled Aggregate (RA) in different percentages such as 25, 50 and 100 to understand its effect. The experiments were conducted for different ages of concrete such as 7, 14, 28, 56 days to assess the compressive and tensile strength. Durability characteristics of recycled aggregate concrete were studied with Rapid chloride penetration test (as per ASTMC1202), sorptivity test and acid test to assess resistance against chloride ion penetration, capillary suction and chemical attack respectively. Mix design for 50 MPa gives around 35 MPa after replacing natural aggregate with recycled aggregate in concrete mix and the chloride penetration range also lies in moderate limit. Hence it is understood from the results that replacement of NA with RA is very much possible and will be ecofriendly.

• Advances in concrete construction
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• 제14권3호
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• pp.205-214
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• 2022

Due to seawater's physical and chemical deterioration effects on concrete structures, it is crucial to investigate the durability of these structures in marine environments. In some conditions, concrete structures are exposed to seawater from the first days of construction or because of the lack of potable water, part of the concrete curing stage is done with seawater. In this research, the effects of exposure to seawater after 7 days of curing in standard conditions were evaluated. To improve the durability of concrete, fly ash has been used as a substitute for a part of the cement in the mixing design. For this purpose, 5, 15, and 30% of the mixing design cement were replaced with type F fly ash, and the samples were examined after curing in seawater. The resistance of concrete against chloride ion penetration based on the rapid chloride penetration test (RCPT), water permeability based on the depth of water penetration under pressure, and water absorption test was done. The changes in the compressive strength of concrete in different curing conditions were also investigated. The results show that the curing in seawater has slightly reduced concrete resistance to chloride ion permeation. In the long-term, samples containing FA cured in seawater had up to 10% less resistance to chloride ion penetration. The amount of reduction in chloride ion penetration resistance was more for samples without FA. Whiles, for both curing conditions in the long-term up to 15%, FA improved the chloride ion penetration resistance up to 40%. Curing in seawater slightly increased the penetration depth of water under pressure in samples containing FA, while this increase was up to 12% for samples without FA. In the long-term the compressive strength of samples cured in seawater is not much different from the compressive strength of samples cured in plain water, while at the age of 28 days, due to seawater salts' accelerating effects the difference is more noticeable.

• Advances in concrete construction
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• 제2권1호
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• pp.39-56
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• 2014

Corrosion in RCC structures is one of the most important factors that affects the structure's durability and subsequently causes reduction of serviceability. The most severe cause of this corrosion is chloride attack. Hence, to prevent this to happen proper understanding of the chloride penetration into concrete structures is necessary. In this study, first the mechanism of this chloride attack is understood and various parameters affecting the process are identified. Then an FEM modelling is carried out for the chloride diffusion process. The effects of fly ash and slag on the diffusion coefficient and chloride penetration depth in various mixes of concretes are also analyzed through integrating Virtual RCPT Lab and FEM.