• 한국건설순환자원학회논문집
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• 제2권1호
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• pp.66-73
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• 2014

Currently many researches have been performed for enhancing durability of concrete. Rice husk ash has several advantages like early strength of concrete and dense pore structure. A calcium silicate hydrate (CSH) gel around the cement particles due to pozzolanic reaction of rice husk can increase the strength of concrete against cracking. Very limitedly a systematic and detailed investigation on the corrosion performance of rice husk ash and silica fume blended concrete is performed. A realistic approach has been made through compressive strength, bond strength, and split tensile strength etc. Corrosion performance was also evaluated rapid chloride ion penetration test (RCPT) and impressed voltage test, and the results were discussed in the paper.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 춘계학술논문 발표대회 제6권1호
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• pp.97-100
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• 2006

This paper report the result of the investigation on the properties of drying shrinkage for alkali-activated slag mortar in different relative humidity Commonly we know that drying shrinkage means lost more moisture but the mechanism of drying shrinkage of alkali activated slag mortar is not entirely due to the quantity of weight loss of water from mortar. pore size distribution and the calcium silicate hydrate gel characteristics have a critical influence on the magnitude of drying shringkage to alkali activated slag mortar. For this investigation, Ca(OH)2, Na2SiO4 were as alkali activator with 5 dosages(6%, 9%, 12%, 15%, 20%) and curing condition were three different relative humidity(35%, 65%, 95%) at $20{\pm}3^{\circ}C$

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.154-165
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• 1996

As II-anhydrite reacts with C3A(aluminate), C4AF(ferrite) at initial hydration of cement and assists the hydrolysis of C3S(calcium silicate), the production rate of ettringite(3C3A.3CaSO4.32H2O) and C-S-H gel was acclerated. It was known that compressive strength of cement concrete improved due to the effect of II-anhydrite. For the checking these effects of II-anhydrite, the fluidity and compressive strength of cementmortar admixed with II-anhydrite and pozollanic fine powders were investigated. By means of SEM analysis, the surface structure of mortar with the condition of steam curing at curing days=28 was investigated. As a result of this experiment, it was examined that II-anhydrite had an increase on the fluidity of cementpaste and compressive strength of mortar.

• 한국세라믹학회지
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• 제36권5호
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• pp.459-464
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• 1999

A carbon-containing silica glass was prepared from orgaincally modified silicate(Ormosil) by heat treatment in N2 atmosphere after the ormosil was synthesized using sol-gel method. The Ormosil was fabricated from the TEOS as the inorganic component and the PDMS as the organic component. The Ormosil changed to balck-coloured glass by carbon decomposed from the PDMS when the Ormosil was heated to 450$^{\circ}C$ 20hrs. A dense silicon oxycarbide glass with 2.08 g/cm3 was obtained by heating the Ormosil at 1050$^{\circ}C$ 10hrs. The microstructure of the carbon-containing silica glass was observed by SEM and the SiOxC4-x structure was confirmed by XPS measurement. The densification of the glass was studied by measurements of specific surface area linear shrinkage and geometric density.

• 한국세라믹학회지
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• 제29권8호
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• pp.660-666
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• 1992

Pitchstone reacted with CaO in hot water(9$0^{\circ}C$) and increased its sedimentary volume by forming Ca(OH)2 and calcium silicate hydrates. ALC was prepared from gel at 9$0^{\circ}C$ and subsequently autoclaved at 18$0^{\circ}C$ by using the property of swelling and the physical properties of ALC was investigated with experimental conditions. When the ratio of pitchstone/CaO was 2 (CaO/SiO2 mol ratio=0.81), bulk density, modulus of rupture and thermal conductivity of the ALC were 0.75g/㎤, 73kg/$\textrm{cm}^2$ 0.150 kcal/m.hr.$^{\circ}C$, respectively. The crystalline phase of it was mainly tobermorite. Therefore ALC was turned out to be much lightweighted and good thermal insulation.

• Advances in concrete construction
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• 제4권4호
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• pp.305-317
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• 2016

Porous materials such as concrete could be subjected to aggressive ions transport. Durability of cement paste is extremely depended on water and ions penetration into its interior sections. These ions transport could lead different damages depending on reactivity of ions, their concentrations and diffusion coefficients. In this paper, chloride diffusion process in cement hydrates is simulated at atomistic scale using molecular dynamics. Most important phase of cement hydrates is calcium silicate hydrate (C-S-H). Tobermorite, one of the most famous crystal analogues of C-S-H, is used as substrate in the simulation model. To conduct simulation, a nanopore is considered in the middle of simulation cell to place water molecules and aggressive ions. Different chloride salts are considered in models to find out which one is better for calculation of the transport properties. Diffusion coefficients of water molecules and chloride ions are calculated and validated with existing analytical and experimental works. There are relatively good agreements among simulation outputs and experimental results.

• 콘크리트학회논문집
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• 제24권6호
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• pp.745-752
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• 2012

이 연구는 혼합 알칼리 활성화 슬래그 모르타르의 압축강도에 미치는 영향에 관한 것이다. 활성화제의 효과는 활성화제의 종류, 농도 등이 강도에 영향을 미치는 것으로 알려져있다. 혼합 활성화제는 5가지 가소성 알칼리(수산화나트륨, 수산화칼슘, 수산화마그네슘, 수산화알루미늄, 수산화칼륨)와 탄산나트륨($Na_2CO_3$)를 혼합하였다. 배함은 각 활성화제를 1M, 2M, 그리고 3M의 서로 다른 농도로 하였다. 압축강도 결과는 혼합 알칼리 활성화 슬래그 모르타르는 탄산나트륨의 농도가 증가하면 증가하는 것으로 나타났다. 혼합 활성화제를 사용한 알칼리 활성화 슬래그 모르타르는 모든 재령과 시험체가 탄산나트륨을 혼합하지 않은 컨트롤 케이스보다 향상된 강도를 나타내었다. 전자주사현미경(SEM) 관찰 결과 활성화 반응으로 C-S-H와 aluminusilicate gel이 생성된 것을 볼 수 있었다.

• 공업화학
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• 제22권2호
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• pp.209-213
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• 2011

낮은 열전도율, 높은 비표면적과 기공률을 갖는 소수성 실리카 에어로겔 과립을, 저가의 물유리를 실리카 전구체로 사용하고 상압건조하여 제조하였다. 별도의 과립화 첨가제 및 과립화 기구를 사용하지 않고, 산도(~5)를 변화시켜 모노리스 형태의 습윤겔을 먼저 제조하여, 용매치환/소수성화 동시공정과 상압건조공정 과정에서 습윤겔이 깨져 0.5~2 mm 크기의 과립형태 실리카 에어로겔을 제조하였다. 제조된 실리카 에어로겔 과립은 비표면적, 평균기공크기, 기공부피가 각각 $593m^2/g$, 34.9 nm, $4.4cm^3/g$으로 실리카 에어로겔 분말과 거의 유사한 다공도를 가지고 있으며, 열전도율도 $20^{\circ}C$에서 19.8 mW/mK으로 나타나 같은 조건에서 제조된 실리카 에어로겔 분말과 거의 같은 단열성을 나타내었다.

• 자원환경지질
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• 제36권5호
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• pp.365-374
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• 2003

다양한 유해성 화학물질들이 콘크리트의 설치환경에 따라 외부로부터 유입될 수 있다. 해수에 의한 콘크리트의 성능저하 현상은 해수의 다양한 화학성분에 의한 복잡한 작용이 연관되어 있다. 따라서, 본 연구에서는 주요 해수 성분의 영향으로 인한 콘크리트 성능저하에 관련된 이차광물의 형성에 따른 광물학적, 미세 구조적 변화 특성에 대하여 연구하였다. 부산경남의 해안지역의 기존 콘크리트 구조물들에서 성능저하특징을 관찰하고 콘크리트 시료를 채취하였다. 채취된 시료에 대한 암석학적분석과 XRD 및 SEM/EDAX 분석을 실시하여 골재와 시멘트페이스트의 화학적, 광물학적, 미세구조적 변화를 해석하였다. NaCl, CaCl, $MgCl_2$ 및 $Na_2SO_4$용액을 사용한 실내 콘크리트 변질 실험을 실시하였다. 변질실험 결과를 기존 콘크리트 시료에 대한 분석 결과를 비교함으로서 해수의 주성분들이 콘크리트의 성능저하에의 영향과 메커니즘을 분석하였다. 해수의 알칼리성분들은 알칼리-골재 반응을 가속화하며, 콘크리트의 심한 팽창과 균열을 발생하는 알칼리-칼슘-실리카겔을 형성하는 것으로 나타났다. 탄산화작용은 다량의 비교결성의 방해석을 형성하여 시멘트페이스트를 약화시키고 있다. 또한, 탄산화작용은 그 진행 정도에 따라 일부 이차광물들의 성분과 안정도에 현저한 영향을 미치는 것으로 나타났다. 탄산화가 현저히 진행된 콘크리트에는 다량의 석고가 형성되었으나, 탄산화가 약하게 진행된 것에는 사우마사이트가 에트린자이트와 고용체를 형성하여 미세 균열을 발생하고 있다. 실험적으로, 에트린자이트는 염소의 유입으로 인하여 trichloroaluminate로 전이되거나 분해되는 것으로 나타났다. 해수의 Mg 이온은 비교결성의 브루사이트와 MSH (magnesium silicate hydrate)를 형성하여 시멘트 페이스트의 성능저하의 원인이 되는 것으로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제33권4호
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• pp.1279-1284
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• 2012

Silica supported $Cs_{2.5}H_{0.5}PMo_{12}O_{40}$ catalyst was prepared through sol-gel method with ethyl silicate-40 as silicon resource and characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, nitrogen adsorption-desorption and potentiometric titration methods. The $Cs_{2.5}H_{0.5}PMo_{12}O_{40}$ particles with Keggin-type structure well dispersed on the surface of silica, and the catalyst exhibited high surface area and acidity. The catalytic performance of the catalysts for benzene liquid-phase nitration was examined with 65% nitric acid as nitrating agent, and the effects of various parameters were tested, which including temperature, time and amount of catalyst, reactants ratio, especially the recycle of catalyst was emphasized. Benzene was effectively nitrated to mononitro-benzene with high conversion (95%) in optimized conditions. Most importantly, the supported catalyst was proved has excellent stability in the nitration progress, and there were no any other organic solvent and sulfuric acid were used in the reaction system, so the liquid-phase nitration of benzene that we developed was an eco-friendly and attractive alternative for the commercial technology.