• 한국건설순환자원학회논문집
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• 제6권1호
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• pp.8-15
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• 2018

본 연구에서는 순환굵은골재의 혼입률에 따른 콘크리트의 강도 특성을 실험을 통해 확인하고, 다량의 순환골재를 콘크리트에 활용하기 위한 기초적 자료로 사용하는 것을 목적으로 한다. 이를 위해, 목표설계기준 압축강도는 40MPa로 하였으며, 순환골재 실용화를 고려하여 순환잔골재의 혼입률을 0, 30%로 하고, 순환굵은골재의 혼입률은 0, 30, 60, 100%로 설정하여 굳지 않은 콘크리트 및 굳은 콘크리트에 대한 실험을 통해 콘크리트 제조에 순환골재 사용의 유효성을 확인하였다. 또한, 전과정 평가(LCA, Life Cycle Assessmet) 기법을 이용하여 순환골재의 전과정 환경영향을 평가하여 콘크리트를 제조함에 있어서 순환골재 사용이 유효성을 확인하였다.

• 콘크리트학회논문집
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• 제16권2호
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• pp.261-268
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• 2004

RC 구조물이 해양 환경에 노출되거나 염화물 환경에 놓이면 콘크리트 속의 매립철근의 부식이 발생한다. 철근의 부식은 구조물의 내구성을 감소시키게 되며, 이러한 부식은 염화물의 침투로 인해 발생하게 된다. 이에 본 연구에서는 염화물 침투실험을 통하여 콘크리트 물성과 시험법이 염화물 확산에 미치는 영향을 살펴보았다. 실험 결과에 따르면, W/C비와 시험법 모두 콘크리트의 확산계수에 영향을 미치는 것으로 나타났다. W/C비가 증가함에 따라 확산계수도 증가하였으나, 비례하여 증가하지는 않았다. 또한, 시험법에 따른 확산계수의 경우, W/C비의 영향은 잘 반영하나 시험법에 따라 확산계수의 차이가 보인다. 본 연구에서는 W/C비에 따른 확산계수 추정식을 제안하였다.

• Composites Research
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• 제28권5호
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• pp.285-290
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• 2015

구조전지에서 멀티스케일로 일어나는 다중물리현상은 기계적 물성을 테스트하는 것을 어렵게 한다. 본 연구에서는 구조전지 셀에 적합한 기계적 물성 테스트 방법을 이용하여 탄소섬유직물의 전해질 코팅이 기계적 성능에 미치는 효과를 알아보았다. 이를 위해 ASTM의 표준 시편 규격을 참고하여 2가지 종류의 시편을 제작하였다. 기계적 물성 실험은 탄소섬유직물에 전해질을 도포하여 전해질 코팅을 수행하고 이를 다시 에폭시에 경화를 시켜 시편을 만들고 만능 인장시험기를 이용하여 인장실험을 진행하였다. 실험결과, 탄소섬유직물에 전해질의 코팅이 기계적물성에는 큰 영향을 주지 않음을 확인할 수 있었다. 또한 실험에 이용한 축소된 규격의 시편이 타당함을 확인할 수 있었다.

• Restorative Dentistry and Endodontics
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• 제22권1호
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• pp.156-169
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• 1997

This study was designed to evaluate the influences of evaporation of liquid of dental cements by drying during long term using. Zinc phosphate cement, polycarboxylate cement, and glass ionomer cement were used, and evaluated the properties as follows; consistency, setting time, film thickness, solubility, and compressive strength according to the ADA specification. The specimens of control group were made by mixing the newly opened liquid using the powder-liquid ratio recommended by the manufacturer, and the specimens of ES groups were made by mixing the 10% evaporated liquid by drying with the powder-liquid ratio recommeded by the manufacturer, and the specimens of EM group were made by mixing the 10% evaporated liquid with the powder-liquid ratio modified for standard consistency. The following conclusions were drawn ; 1. The viscosity of mixture of all kinds of cements were increased by the evaporation of liquid, especially the viscosity of glass ionomer cement were influenced significantly. 2. The amount of liquid should be increased to get a standard consistency at the using of evaporated liquid of cement, the most significant increase of liquid amount was required on Ketac-Cem. 3. The setting times were increased at both cases of mixing of evaporated liquid with powder - liquid ratio recommended by manufacturer or modifided through consistency test. 4. At an experimental group of mixing of the evaporated liquid with powder-liquid ratio recommended by manufacturer, solubility was decreased and film thickness was increased. 5. By the result of evaporation of cement liquid, the compressive strength of polycarboxylate cement was increased slightly and it of glass ionomer cement was increased, however, by the increase of amount of liquid to be possible to manipulate the compressive strength were decreased.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 춘계학술논문 발표대회 제6권1호
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• pp.35-38
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• 2006

This study investigated fundamental properties of lightweight foamed concrete using cement kiln dust (CKD) and both fly ash(FA) and stability agent. Test results showed that concrete incorporating more amounts of admixture decreased slump flow and it caused increase of superplasiticizer in order to secure the fluidity performance. In addition concrete adding stability agent showed stable flow state, resisting segregation of materials and decreasing bleeding capacity. Sinking depth of concrete incorporating 20% of CKD and adding 0.002% of stability agent was indicated at 0mm. For the properties of hardened concrete. compressive strength of concrete incorporating CKD declined due to a lower appearance density, compared with other specimens. The difference of that was not very significant and the value of ail specimen was higher than KS range. Moreover strength of concrete incorporating CKD was even higher at curing temperature $5^{\circ}C$. Tensile strength ratio of concrete incorporating CKD was indicated between 0.50 to 0.59, which is higher value than control concrete. Heat conductivity of concrete incorporating FA was under the KS range while concrete incorporating 20% of CKD was satisfied in KS. Concrete adding stability agent improved insulation performance due to the lower heat conductivity. In conclusion, it is possible that concrete incorporating 20% of CKD and adding 0.002% of stability agent can secure high quality of lightweight foamed concrete.

• 콘크리트학회논문집
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• 제17권6호
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• pp.939-946
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• 2005

비균질 재료인 콘크리트의 강성 특성과 성능저하 현상을 웨이블릿 변환을 이용한 다중해상도해석을 통해 각 관찰 규모에 따라 동질화 과정의 적용성 및 거시적 손상지수의 평가 등을 연구하였다. 연속적인 Haar 웨이블릿 변환은 기존 강성행렬의 특성을 연속적인 축소규모로의 복제를 통해 미세규모로부터 거시규모로의 축소 또는 복원 과정을 나타내었고 이는 선형구조계의 크기별 스펙트럼 특성의 보존, 즉 타원성, 철면성 그리고 양의 정부호성을 보존하여 각 규모별 해의 유효성을 확인하였다. 웨이블릿 계수를 이용한 기존 강성의 평균은 거시단계의 변형에너지와 상호관계를 가지고 아래 단계로의 축소, 윗 단계로의 복원을 자유롭게 할 수 있는 장점이 있다. 이러한 다중해상도해석의 예제로서 1차원 및 2차원 2상복합체를 가지고 유한요소해석을 통해 기존 이론의 검증과 최소고유치의 각 크기단계별 변화 과정, 원 축소 구조계의 해의 유일성 그리고 국부적 손상지수의 동질화 여부 등을 검사하였다. 이러한 동질화 축소 과정은 자유도가 큰 비선형 구조계로의 적용의 첫 단계를 제공하였다.

• 콘크리트학회논문집
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• 제15권3호
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• pp.462-469
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• 2003

본 논문에서는 습식스프레이 공법에 의하여 타설되는 고인성 섬유보강 모르타르(ECC)을 구조물의 보수에 적용함으로써 구조물의 내구성을 증진시키는 효과에 대하여 연구하였다. 이를 위하여 굳지않은 상태에서는 스프레이 공정에 적합한 유동특성을 갖고 있으면서, 굳은 후에는 인장변형경화거동을 나타내는 ECC를 스프레이 공법으로 타설하여 시험체를 제작하여 실험하였다. 실험 결과, 스프레이된 ECC의 역학적 특성(인장 및 휨거동)이 일반적인 타설법에 의하여 제작된 ECC와 거의 일치하는 것으로 나타났으며, 이 때에 ECC의 균열폭은 평균 30${\mu}m$로 제어되었다. 구콘크리트/ECC 합성보의 에너지 흡수능력은 구콘크리트/상용 스프레이 모르타르(PM) 합성보에 비하여 매우 우수한 것으로 나타났으며, 경계면의 부착성능도 양호한 것으로 평가되었다. ECC 고유의 균열제어능력과 더불어 보수된 부재(구콘크리트/ECC 합성보)의 탁월한 휨변형능력, 에너지 흡수능력 등은 구조물의 내구성을 증진하는데 큰 이점으로 작용하게 될 것이다.

• 한국세라믹학회지
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• 제51권2호
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• pp.72-81
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• 2014

The main mineral phases of natural hydraulic lime (NHL) as a hydraulic lime binderare $Ca(OH)_2$, $C_2S$, $C_3S$, $C_3A$, and $SiO_2$ residues. Also, NHL has the characteristic of setting and hardening by a hydration reaction with water and by carbonation reactions with carbon dioxide from the air. In this study, in an effort to investigate changes of the mineral phases by NHL hydration and carbonation reactions, transitions of mineral phases and the microstructures of hardened pastes were analyzed by XRD, DSC, SEM, and by pore size distributions using domestic and foreign-sourced NHL pastes after curing at 1, 3, 7, and 28 days. On the basis of the analysis results, it was confirmed that domestic low-grade limestone can be used for the manufacturing of NHL. The main hydration mineral phases were $Ca(OH)_2$, $CaCO_3$, $C_2S$, and $SiO_2$ residues, while in the case of foreign-sourced NHL, a small amount of an aluminium hydration phase formed. Also, the $CaCO_3$ content after the carbonation reaction increased with an increase in the curing time. After hydration for 28 days, NHL containing considerable amounts of $C_2S$ and $C_3S$ showed higher carbonation ratios than others types.

• 한국건축시공학회지
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• 제2권4호
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• pp.89-98
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• 2002

Self-leveling material(SLM) is one of the floor finishing materials which make flat surface like as water level by itself in a short time. So it is possible to increase construction speed and enhance economical efficiency In this study, author intended to develop SLM for the industrial warehouse and factory loading heavy weight machinery and vehicles. The demanded properties for this type of SLM are above 200mm of flow value and above 300kgf/$cm^2$ of 28-days compressive strength. To possess demended strength and fluidity, SLM have to be composed of many types of binders and chemical additives. So it is difficult to decide suitable mixing proportion of composition materials. In this study, author investigated the weight percentage effect of main composition materials for high-strength self-leveling material, by experimental design such as tables of orthogonal arrays and simplex design, and by statistical analysis such as analysis of variance and analysis of response surface. Variables of experiments were ordinary Portland cement(OPC), alumina cement(AC), anhydrous gypsum(AG), lime stone(LS) and sand, and properties of tests were fluidity of fresh state and strength of hardened state. Results of this study are showed that suitable mix proportions of binders for the high strength self-leveling materials are two groups. One is 78~85.5% OPC, 7.5~9.5% AC, 9~12.5% AG and the other is 72.5~78% OPC, 9~12.5% AC, 13~15% AG.

• 콘크리트학회논문집
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• 제17권2호
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• pp.293-302
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• 2005

This study describes data from determination of the optimum mix proportion and site application of the mass concrete placed in bottom slab and side wall having a large depth and section as main structures of LNG in-ground tank. This concrete requires low heat hydration, excellent balance between workability and consistency because concreting work of LNG in-ground tank is usually classified by under-pumping, adaptation of longer vertical and horizontal pumping line than ordinary pumping condition. For this purpose, low heat Portland cement and lime stone powder as cementitious materials are selected and design factors including unit cement and water content, water-binder ratio, fine aggregate ratio and adiabatic temperature rising are tested in the laboratory and batch plant. As experimental results, the optimum unit cement and water content are selected under $270kg/m^3$ and $l55{\~}l60 kg/m^3$ separately to control adiabatic temperature rising below $30^{\circ}C$ and to improve properties of the fresh and hardened concrete. Also, considering test results of the confined water ratio($\beta$p) and deformable coefficient(Ep), $30\%$ of lime stone powder by cement weight is selected as the optimum replacement ratio. After mix proportions of 5cases are tested and compared the adiabatic temperature rising($Q^{\infty}$, r), tensile and compressive strength, modulus of elasticity, teases satisfied with the required performances are chosen as the optimum mix design proportions of the side wall and bottom slab concrete. $Q^{\infty}$ and r are proved smaller than those of another project. Before application in the site, properties of the fresh concrete and actual mixing time by its ampere load are checked in the batch plant. Based on the results of this study, the optimum mix proportions of the massive concrete are applied successfully to the bottom slab and side wall in LNG in-ground tank.