• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.513-516
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• 2006

Waste concrete powder(WCP) is a secondary by-product generated while processing waste concrete manufactured to coarse and fine aggregates for concrete. In order to assess the possibility of using WCP as admixture for self-compacting concrete, self-compactability, compressive strength and durability of self-compacting concrete containing waste concrete powder were investigated. Experimental results of this study appeared that in case of SCC mixed with WCP only, self-compactability and compressive strength decreased with increasing mixing ratio of WCP. When Blast-furnace slag(BFS) was added to SCC, self-compactability and compressive strength for a unit amount of cement increased. Also, SCC containing 15% BFS and 15%, 30% and 45% WCP, the dry shrinkage and carbonation depth appeared a tendency to decrease with increasing mixing ratio.

• Bulletin of the Korean Chemical Society
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• 제32권7호
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• pp.2193-2198
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• 2011

We prepared polycatenar 1H-imidazole amphiphiles having a structure in which a 1H-imidazole head was connected through a benzene ring to a pheny group having two or three oligo(ethylene glycol) chains and studied their supramolecular assembly by fluorescence spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM). When the aqueous solutions of the amphiphiles ($5{\times}10^{-5}M{\sim}10^{-3}M$) were deposited onto a carbon-coated copper grid and dried, twisted structures with diameters of ~200-300 nm were imaged by TEM and AFM. We presume that the structures comprised a chain of the amphiphile dimers formed via successive hydrogen bonding between the 1H of the imidazole group and 3N of the neighboring one. In a solution of pH 4, entangled fibers with diameters of several nanometers were observed by TEM. In a pH 10 solution, film-like aggregates formed exclusively. The 1H-imidazole amphiphiles hydrolyzed tetraethoxysilane to induce gelation to form fibrous and spherical silica structures at neutral pH in aqueous solutions. No silica was formed when imidazole was used instead of the amphiphiles, suggesting that the selfassembled aggregates of the amphiphiles were responsible for the gelation.

• Advances in concrete construction
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• 제7권2호
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• pp.97-105
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• 2019

In this paper, the workability and static stability were evaluated using a proposed test method. Workability and static stability represent a key property of self-compacting concrete (SCC) in fresh state. A number of standardized test methods were developed to assess these properties. However, no accelerated test method reliably predicts both workability and static stability of SCC. In the present work, a modified K-slump test method was developed to evaluate workability and static stability of SCC. In order to take implicit mixture variations of SCC constituents that can affect fresh SCC properties, a central composite design was adopted to highlight the effect of gravel to sand ratio (G/S), gravel 3/8 to gravel 8/15 ratio (G1/G2), water to cement ratio (W/C), marble powder to cement ratio (MP/C) and superplasticizer content (SP) on workability measured with slump and flow time (T50) tests and static stability measured with sieve stability test (Pi), segregation test index (SSI), Penetration test (Pd) and the proposed K-slump test (Km). The obtained results show that G/S ratio close to 1 and G1/G2 ratio close to 60% can be considered as optimal values to achieve a good workability while ensuring a sufficient static stability of SCC. Acceptable relationships were obtained between Slump flow, Pi, Pd and Km. Results show that the proposed K-slump test allow to assess both workability and static stability of fresh SCC mixtures.

• 한국구조물진단유지관리공학회 논문집
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• 제27권4호
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• pp.62-69
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• 2023

본 연구에서는 제강 슬래그 (fine steel slag aggregates, FSSAs) 혼입량에 따른 스마트 보수재료 (smart repair materials, SRMs)의 전기역학적 거동을 조사하였다. SRMs는 보수 품질을 스스로 진단하고 보수 부위의 손상을 자체적으로 감지할 수 있다. FSSAs는 SRMs에 모래 중량 대비 0% (FSSA00), 25% (FSSA25), 그리고 50% (FSSA50) 치환되어 혼입되었다. SRMs의 전기저항률은 일반적으로 압축 응력이 증가함에 따라 감소하였다: 재령 7시간 기준 FSSA25의 전기저항률은 압축 응력이 0에서 22.57 MPa로 증가함에 따라 78.16에서 63.68 kΩ-cm으로 감소하였다. FSSAs의 모래 중량 대비 치환율이 0%에서 25%로 증가함에 따라 재령 7시간 기준 응력 민감도 (stress sensitivity coefficient, SSC)는 매트릭스 내 부분적인 전도성 경로 수의 증가로 인해 0.471에서 0.828 %/MPa로 증가하였다. 하지만, 치환율이 50%까지 증가함에 따라 부분적인 전도성 경로들의 일부가 연속적인 전도성 경로로 변화하여 SSC는 0.828에서 0.649 %/MPa로 감소하였다. SRMs는 보수 부위의 전기저항률만을 측정하는 것으로 보수 품질을 진단하고 보수 부위의 추가 손상을 스스로 감지할 수 있을 뿐만 아니라 구조물의 역학적 성능을 빠르게 회복시킬 수 있을 것으로 기대한다.

• 한국재료학회지
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• 제9권1호
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• pp.51-56
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• 1999

The $BaTiO_3$ powders were synthesized by GNP (Glycine-Nitrate process). The powders were prepared using carbonate and alkoxide as starting materials and nitric acid was used as a solvent for starting materials as well as an oxidant for combustion. the effects of aggregates in $BaTiO_3$ powders on green densities, sintering and dielectric characteristics were investigated. When the glycine/cation molar ratio was 1.2, reactivity of self-combustion was most intensive and the degree of aggregates after calcination was low. On sintering at $1400^{\circ}C$, maximum theoretical relative density(94.99%%0 was obtained in case of 1.2 molar ratio of glycine/cation. The dielectric constant of this sintered $BaTiO_3$ was 1919.

• Macromolecular Research
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• 제11권1호
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• pp.2-8
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• 2003

The self-assembly of polymers can lead to supramolecular systems and is related to the their functions of material and life sciences. In this article, self-assembly of Langmuir-Blodgett (LB) films, polymer micelles, and polymeric nanoparticles, and their biomedical applications are described. LB surfaces with a well-ordered and layered structure adhered more cells including platelet, hepatocyte, and fibroblast than the cast surfaces with microphase-separated domains. Extensive morphologic changes were observed in LB surface-adhered cells compared to the cast films. Amphiphilic block copolymers, consisting of poly(${\gamma}$-benzyl L-glutamate) (PBLG) as the hydrophobic part and poly(ethylene oxide) (PEO) [or poly(N-isopropylacrylamide) (PNIPAAm)] as the hydrophilic one, can self-assemble in water to form nanoparticles presumed to be composed of the hydrophilic shell and hydrophobic core. The release characteristics of hydrophobic drugs from these polymeric nanoparticles were dependent on the drug loading contents and chain length of the hydrophobic part of the copolymers. Achiral hydrophobic merocyanine dyes (MDs) were self-assembled in copolymeric nanoparticles, which provided a chiral microenvironment as red-shifted aggregates, and the circular dichroism (CD) of MD was induced in the self-assembled copolymeric nanoparticles.

• 대한토목학회논문집
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• 제29권4A호
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• pp.373-384
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• 2009

다공성 경량골재의 사전흡수수에 따른 콘크리트 수축 저감 효과의 정량적 평가와 부등수축해석모델 상수 제공을 위한 첫번째 단계로서, 수분이동모델을 설정하고 이에 따른 수분이동 특성상수인 유효수분확산계수, 수분용량, 습도공급도, 습도소모도를 물-결합재비, 골재 종류를 변수로 하여 측정하였다. 콘크리트 내, 외부 습도차에 의한 정상상태에서의 유효수분확산계수는 물-결합재비가 낮을수록 낮은 값을 나타내었으며 동일한 물-결합재비인 경우 일반골재를 사용한 배합이 경량골재를 사용한 배합보다 낮은 유효수분확산계수값을 나타내었다. 콘크리트 내 수분의 저장 능력 즉, 수분용량을 산정하기 위해 9가지 습도에서 콘크리트의 수분량을 측정하였으며 경량골재를 사용한 배합이 일반골재를 사용한 배합보다 모든 습도조건에서 수분량이 크게 나타났다. 일반 대기환경 습도 50% 이상 조건에서 적용할 수 있는 경량골재의 습도공급도를 측정하여 정량화 하였으며, 경량골재에서의 수분 방출량은 주변 습도에 반비례하고 시간에 비례하는 뚜렷한 경향을 나타내는 지수함수의 형태로 설정하였다. 시멘트 수화 자기건조에 의한 수분의 내부소모에 따른 콘크리트 내 습도소모도를 측정하였으며, 측정결과 물-결합재비 0.3의 경우 7~10일 이내의 초기재령에서 약 10% 내외의 급격한 습도감소를 나타내었으며 물-결합재비 0.4, 0.5의 경우 완만한 형태로 약 5%, 1% 내외의 습도 감소를 나타내었다.

• Journal of Photoscience
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• 제9권2호
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• pp.347-349
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• 2002

Synthetic zinc chlorins possessing a hydrophylic polyoxyethylene chain at the 17 -position were prepared. An amphiphilic zinc chlorin possessing a single chIorin moiety showed absorption maxima at 675 nm in an aqueous medium, indicating that the zinc chIorin did not form large aggregates but a dimeric structure. In contrast, amphiphilic zinc chlorin dyads in which two zinc chlorin moieties were connected with a hydrophilic polyoxyethylene linkage showed red-shifted absorption band around 720-740 nm in an aqueous medium. The result indicated that the amphiphilic zinc chlorin dyad self-aggregated to form chlorosome-like oligomer.

• Structural Engineering and Mechanics
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• 제67권1호
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• pp.87-91
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• 2018

Concrete is the most widely used building material all over the world, because of its many technical and economic qualities. This pressure on the concrete resource causes an intensive exploitation of the quarries of aggregates, which results in a exhaustion of these and environmental problems. That is why recycling and valorization of materials are considered as future solutions, to fill the deficit between production and consumption and to protect the environment. This study is part of the valorization process of local materials, which aims to reuse marble waste as fine aggregate (excess loads of marble waste exposed to bad weather conditions) available in the marble quarry of Fil-fila (Skikda, East of Algeria) in the manufacture of self-compacting concretes. It consists of introducing the marble waste as sand into the self-compacting concrete formulation, with variable percentages (25%, 50%, 75% and 100%) and to study the development of its properties both in fresh state (air content, density, slump flow, V-funnel, L-box and sieve stability) as well as the hardened one (compressive strength and flexural strength). The results obtained showed us that marble wastes can be used as sand in the manufacture of self compacting concretes.

• 대한토목학회논문집
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• 제42권4호
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• pp.449-455
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• 2022

콘크리트는 가장 많이 사용되는 건설재료이다. 콘크리트의 비교적 높은 자중은 압축강도 발현과 수축저항성에서 이점을 갖지만, 초장대교량이나 초고층빌딩에 적용되기에는 구조물 자체의 무게가 큰 폭으로 증가하게 되어 거대 구조물의 형상을 제약하는 조건이 되기도 한다. 이러한 문제를 해결하고자, 경량골재를 사용하는 경량 콘크리트 개발이 많이 진행되어 왔으나, 경량 골재의 경우 다공질 구조로 인해 자체 강도가 작기 때문에, 일반적으로 경량 콘크리트는 일반 콘크리트에 비해서 낮은 강도를 가지게 된다. 본 연구에서는 기존의 경량 콘크리트의 한계점을 극복한 경량을 유지하면서 고강도를 만족시키는 건설재료를 개발하고자 하였다. 중공 유리 마이크로스피어를 낮은 물-시멘비율의 매트릭스에 다량으로 사용하는 방법을 적용해 보았으며, 네 가지 다른 종류의 마이크로스피어를 사용하여 그 적용성을 살펴보았다. 실험결과, 마이크로스피어의 종류와 관계 없이 밀도 1.7 g/cm³를 유지하면서 압축강도 60 MPa와 80 MPa를 각각 상온양생과 고온양생 조건에서 만족하는 것을 확인할 수 있었다.