• International Journal of Concrete Structures and Materials
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• 제11권1호
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• pp.99-113
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• 2017

The effects of different lightweight functional fillers on the properties of cement-based composites are investigated in this study. The fillers include fly ash cenospheres (FACs) and glass micro-spheres (GMS15 and GMS38) in various proportions. The developed composites were tested for compressive, flexural and tensile strengths at 10 and 28-day ages. The results indicated that both FACs and GMS38 are excellent candidates for producing strong lightweight composites. However, incorporation of GMS15 resulted in much lower specific strength values (only up to $13.64kPa/kg\;m^3$) due to its thinner shell thickness and lower isostatic crushing strength value (2.07 MPa). Microstructural analyses further revealed that GMS38 and GMS15 were better suited for thermal insulating applications. However, higher weight fraction of the fillers in composites leads to increased porosity which might be detrimental to their strength development.

• 한국공간구조학회논문집
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• 제10권4호
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• pp.85-92
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• 2010

콘크리트의 사용은 건축 및 토목분야에서 널리 사용되어 왔으며, 센서는 콘크리트에 기능적 특성을 위해 사용되어 왔다. 손상을 스스로 나타내는 콘크리트는 이미 개발되고 있는 중에 있다. 본 연구에서 온도보상센서는 금속의 선형팽창과 체적변형을 이용한 센서이다. LED는 광센서로 고휘도이며, 이들 센서의 가격은 저가격이다. 화재하중으로 인하여 콘크리트 보의 온도보상센서가 동작하는 동안 지상 보의 LED동작으로 콘크리트 부재의 온도상승을 예측한다. 본 연구에서는 부재의 손상감지를 위해 간단한 계측방법을 이용하여 화재자현을 스스로 나타내는 콘크리트 보를 개발하기 위한 기초적 연구이다.

• Structural Engineering and Mechanics
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• 제41권6호
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• pp.691-710
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• 2012

One of the most popular and commonly used strengthening techniques to protect against earthquakes is to infill the holes in reinforced concrete (RC) frames with fully reinforced concrete infills. In some cases, windows and door openings are left inside infill walls for architectural or functional reasons during the strengthening of reinforced concrete-framed buildings. However, the seismic performance of multistory, multibay, reinforced concrete frames that are strengthened by reinforced concrete wing walls is not well known. The main purpose of this study is to investigate the experimental behavior of vulnerable multistory, multibay, reinforced concrete frames that were strengthened by introducing wing walls under a lateral load. For this purpose, three 2-story, 2-bay, 1/3-scale test specimens were constructed and tested under reversed cyclic lateral loading. The total shear wall (including the column and wing walls) length and the location of the bent beam bars were the main parameters of the experimental study. According to the test results, the addition of wing walls to reinforced concrete frames provided significantly higher ultimate lateral load strength and higher initial stiffness than the bare frames did. While the total shear wall length was increased, the lateral load carrying capacity and stiffness increased significantly.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 추계학술발표회 발표논문집
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• pp.1383-1384
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• 2004

• 한국도로학회논문집
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• 제14권4호
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• pp.51-61
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• 2012

PURPOSES : This study deals with the working life of polymer concrete, which is typically used as a repair or overlay material for portland cement concrete pavements. METHODS : In the scope of this study, laboratory testing was conducted on fresh MMA modified UP polymer concrete, which uses an MMA monomer for viscosity adjustment and strength improvement of UP resin. The experimental variables were temperature (-20 to $+20^{\circ}C$) and binder components (MMA, MEKPO, and DMA). RESULTS : The result showed that the optimum binder ratios for polymer concrete production were 12, 11, and 10 wt.% when the MMA contents were 20, 30, and 40 wt.%, respectively. The working life of polymer concrete depending on temperature and binder components could be expressed by a logarithmic functional formula. The coefficient of variation for each binder component was the highest for DMA content while the lowest for MEKPO content. Also, the contents of each binder component for ensuring the working life of 60 minutes were proposed. CONCLUSIONS : Ultimately, the present study derived a linear regression equation estimating 60 minutes working life based on the setting times of each binder component.

• Nuclear Engineering and Technology
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• 제47권6호
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• pp.756-765
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• 2015

Background: Fibers have been used in cement mixture to improve its toughness, ductility, and tensile strength, and to enhance the cracking and deformation characteristics of concrete structural members. The addition of fibers into conventional reinforced concrete can enhance the structural and functional performances of safety-related concrete structures in nuclear power plants. Methods: The effects of steel and polyamide fibers on the shear resisting capacity of a prestressed concrete containment vessel (PCCV) were investigated in this study. For a comparative evaluation between the shear performances of structural walls constructed with conventional concrete, steel fiber reinforced concrete, and polyamide fiber reinforced concrete, cyclic tests for wall specimens were conducted and hysteretic models were derived. Results: The shear resisting capacity of a PCCV constructed with fiber reinforced concrete can be improved considerably. When steel fiber reinforced concrete contains hooked steel fibers in a volume fraction of 1.0%, the maximum lateral displacement of a PCCV can be improved by > 50%, in comparison with that of a conventional PCCV. When polyamide fiber reinforced concrete contains polyamide fibers in a volume fraction of 1.5%, the maximum lateral displacement of a PCCV can be enhanced by ~40%. In particular, the energy dissipation capacity in a fiber reinforced PCCV can be enhanced by > 200%. Conclusion: The addition of fibers into conventional concrete increases the ductility and energy dissipation of wall structures significantly. Fibers can be effectively used to improve the structural performance of a PCCV subjected to strong ground motions. Steel fibers are more effective in enhancing the shear performance of a PCCV than polyamide fibers.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 추계 학술논문 발표대회
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• pp.143-144
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• 2018

This study the workability of synthetic resin form was examined through field application. results there was no warping or bulging of the mold during concrete placement in the field application. Also, the concrete surface finish of synthetic resin form was better than that of euro-form.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.225-231
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• 1996

The dense graded asphalt concrete materials have been used for construction of pavement for a long time. The performance of asphalt concrete pavement, however, is influenced by various factors including high temperature and heavy axle loads which cause plastic deformation. The plastic deformation is one of the main functional disadvantages of flexble pavement. In this study, the semi-rigid pavement is considered to solve the problem. A set of experimental evaluation on semi-rigid pavement material has been coducted in laboratory to obtain it's physical properties and serviceabilities. The results of tests, including compressive strength, flexural strength, ravelling and wheel tracking, show that the semi-rigid pavement has a good mechanical properties and serviceabilities. Consequently, the semi-rigid pavement may be suitable to bridge deck, tunnel, slow lane and parking area pavements.

• Computers and Concrete
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• 제19권2호
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• pp.179-189
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• 2017

Concrete shear walls are one of the major structural lateral resisting systems in buildings. In some cases, due to the change in the occupancy of the structure or functional requirements like architectural and even mechanical ones, openings need to be provided and installed in structural walls after their construction. Providing these openings may significantly influence the structural behavior of the constructed wall. This paper considers the results of a nonlinear finite element analysis of shear walls with opening strengthened by carbon fiber reinforced polymer (CFRP) strips with different configurations. Details of bond-slip constitutive model of link elements to simulate the connections of FRP strips to concrete surface is presented. The proposed model in this research has been validated using experimental results available in the literature. The results indicated that the proposed configuration of CFRP strips significantly improved the lateral resistance and deformation capacity of the shear walls with opening.

• 콘크리트학회논문집
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• 제22권4호
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• pp.547-557
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• 2010

이 연구는 미생물의 생체광물형성작용 중 미생물의 방해석 석출 작용(micro-biologically induced calcite precipitation, MICP)을 이용하여 환경적인 문제를 배려한 차세대 스마트 콘크리트의 개발이 목적이다. 현재 콘크리트의 개질(改質) 및 성능향상을 목적으로 미생물의 방해석 석출 작용을 이용한 기술은 대표적 미생물인 Sporosarcina pasteurii에 의해 그 가능성이 제안되어 왔다. 이 연구에서는 이러한 미생물의 방해석 석출작용을 이용하는 것으로서 선행 연구의 Sporosarcina pasteurii외에 콘크리트 구조물에서 탐색하여 16S rDNA 염기서열 분석법에 의해 동정된 4종의 신규 유용미생물자원들을 추가적으로 이용하였으며, 이렇게 확보된 방해석을 석출하는 유용미생물자원들에 대한 소개와 미생물의 방해석 석출 작용에 따른 시멘트 결정성을 평가하였다. 또한 콘크리트의 개질 및 성능 향상을 목적으로 이러한 유용미생물자원들을 우선적으로 모르타르 환경에 적용하여 양생조건별 압축강도의 특성을 평가하고, 모르타르에 인위적 균열을 만들어 미생물의 방해석 석출 작용에 따른 균열의 충전 가능성을 검토하였다. 이러한 유용미생물들의 적용에 따른 효과는 보수 기능뿐만 아니라 환경 문제를 배려한 새로운 재료로서의 개발로 이어져 향후 더욱 더 중요한 연구주제의 하나가 될 것으로 기대된다. 또한 이 연구의 큰 의미는 실제 콘크리트 구조물에 상생하고, 자연환경에서 방해석을 석출하는 미생물을 이용한다는 것이며, 긴 시간동안 자연환경에서 살아남은 이 미생물들은 환경적으로 안전할 뿐만 아니라 새로운 환경 저부하성 기능재료로서의 이용이 가능할 것으로 판단된다.