• 콘크리트학회지
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• 제2권4호
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• pp.83-90
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• 1990

최근 개발되어 사용되고 있는 초속경시멘트는 그 조성광물중에 Cakcium-aluminate(11 Cao \ulcorner7Al2O3\ulcornerCaF2) 및 그 수화물이 존재하고 있어 이것들이 산과 극렬반응을 일으켜 시멘트 경화체에 균열과 붕괴현상을 가져온다. 본 연구는 이러한 초속경 시멘트를 사용한 경화체가 Polymet에 의한 개길로 어느 정도의 내산성을 발휘할 수 있는지를 실험한 내용으로 P/C=15 및 20%에서는 다른 시멘트를 사용한 경우와 비슷한 내산성이 있음을 알 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제17권3호
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• pp.89-96
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• 2013

1990년대 후반부터 사용된 폴리머 콘크리트로 제작된 맨홀은 이 맨홀이 가지고 있는 다양한 장점 때문에 현재까지 널리 이용되고 있다. 그러나, 고유가 시대로 접어들면서 석유화학 재료의 가격인상과 더불어 폴리머 콘크리트의 제조원가가 상승되고 이에 따른 폴리머 콘크리트의 약점이 대두되고 있다. 따라서, 고가의 폴리머 콘크리트로 제작된 맨홀의 뛰어난 휨강도를 대체할 수 있는 경제적인 시멘트 콘크리트 맨홀의 개발이 요구되어 왔다. 본 연구에서는 비정질 칼슘알루미네이트 (Armorphous calcium aluminate, ACA)계의 속경형 시멘트기술을 기반으로 플라이 애쉬와 고로슬래그, 실리카 퓸, 메타카올린 등의 산업부산물을 이용하여 시멘트의 사용량을 최소화시킴으로써 $CO_2$를 저감시킬 수 있는 친환경적인 맨홀용 고인성 콘크리트를 개발하고자 하였다. 연구결과, 경제적이고 친환경적이면서도 요구성능을 만족시키는 시멘트 콘크리트 맨홀을 개발하였다.

• 한국세라믹학회지
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• 제24권4호
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• pp.329-334
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• 1987

Diffusion of SO4-- ion in hardened cement paste with slag and siliceous powders such as silica fume and white carbon was investigated. Ca(OH)2 from hardenend cement paste was dissolved by sea-water and then gypsum was formed from the reaction of Ca++ in hardenend cement paste and SO4-- ions in MgSO4 solution. A part of the gypsum by reaction with calcium aluminate hydrates formed ettringite. Amounts of SO4-- ions passed through hardened cement paste was less than that of Cl- ions(Dcl-) in hardened cement paste were 0.1∼0.6${\times}$10-11$\textrm{cm}^2$/sec and 1∼4${\times}$10-8$\textrm{cm}^2$/sec respectively.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.475-476
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• 2010

Hydration products formed on the steel surface may impose the resistance to corrosion of steel when a concrete is exposed to a salt environment. In the present study, ordinary Portland cement (OPC), calcium aluminate cement (CAC) and calcium hydroxide are applied as coating materials on the steel surface to consider the hydrations of each binder at corrosion. Corrosion is measured in terms of the corrosion potential and galvanic current to detect the effects in mitigating the corrosion behavior.

• 한국건축시공학회지
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• 제18권5호
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• pp.403-412
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• 2018

최근 순환골재의 활용에 관한 필요성이 증대되고 있으나, 순환골재의 강알칼리성으로 인해 다양한 문제들이 발생되고 있다. 순환골재의 강알칼리성은 대부분 골재 표면에 완전히 제거되지 못한 시멘트 페이스트에 의해 발현되는 것으로써 이를 해결하기 위해 이산화탄소를 활용하여 순환골재의 pH를 저감하기 위해 노력이 지속되어왔다. 그러나 기존의 이산화탄소를 이용한 처리 방법에 의해 중성화 처리된 순환골재는 시간이 지남에 따라 pH가 다시 회복된다는 문제점을 가지고 있다. 따라서 본 연구에서는 이러한 문제점을 해결하기 위한 방법으로 반응성이 뛰어난 초임계이산화탄소의 활용을 제안하며, 이를 위해 초임계상의 이산화탄소와 수화된 시멘트 페이스트간의 반응 메커니즘을 분석하였다. 그 결과 입자 형태 및 $scCO_2$ 주입량에 따라 중성화 반응정도가 현저하게 달라지는 것으로 나타났다. 특히 powder 형태 시험체에서 $scCO_2$ 주입량이 많은 고온 고압 상태에서 중성화 반응은 활발하게 이루어졌다. 이때 시멘트의 높은 pH를 주도하는 portlandite가 대부분 calcite와 aragonite의 형태로 변환되었으며, ettringite, hemicarbonate 및 monocarbonate와 같은 calcium aluminate 수화물 또한 안정적으로 존재하지 못하고 분해된 것으로 나타났다. 반면, 10mm 크기의 수화된 시멘트 페이스트는 $scCO_2$가 시험체 내부깊이 침투하지 못하고 표면에서만 반응하여, 반응 후에도 내부에 portlandite와 calcium aluminate 수화물이 잔존한다. 이로 인해 시간이 경과할수록 내부의 portlandite가 점차 용출되어 pH가 다시 상승하는 것으로 나타났다.

• 대한금속재료학회지
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• 제46권7호
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• pp.437-442
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• 2008

The synthesis and hydration of Calcium Sulfo Aluminate[$3CaO{\cdot}3Al_2O_3{\cdot}CaSO_4(C_4A_3{\overline{S}})$, CSA cement utilizing secondary steelmaking refining slags is studied for recycling the discarded steel plant wastes to meet the environmental requrations imposed on the steel industry. Raw materials of secondary refining slag, lime sludge, gypsum and bauxite were prepared to be sintered at $1,250^{\circ}C$. The sintered samples were hydrated for 1, 3 and 7 days to evaluate the mineralogical and physico-mechanical properties. The hydration products evaluated with the aid of SEM and XRD analyses confirmed the formation and the continuing growth of ettringite phase with the further hydration times, which plays a role in developing the early strength and the expansion properties of cements. The physico-mechanical properties of hydrated CSA products employing the recycled steelmaking refining slags determined in terms of compressive strength and linear expansion of hydrated products are found to be superior to those of the Ordinary Portland Cement(OPC) or the other commercial CSA cements.

• Advances in concrete construction
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• 제5권3호
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• pp.289-301
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• 2017

The synergistic interactions of supplementary cementitious materials (SCMs) with ordinary portland cement (OPC) in multi-blended systems could enhance the mechanical and durability properties of concrete and increase the amount of cement that can be replaced. In this study, the characteristics of the hydration products as well as paste microstructure of blended cement containing 20% coal fly ash, 10% rice hull ash and 10% sugar mill lime sludge in quaternary blended system was investigated. Portlandite content, hydration products, compressive strength, pore size distribution and microstructural architecture of hydrated blended cement pastes were examined. The quaternary blended cement paste showed lower compressive strength, reduced amount of Portlandite phases, and higher porosity compared to plain hardened cement paste. The interaction of SCMs with OPC influenced the hydration products, resulting to the formation of ettringite and monocarboaluminate phases. The blended cement paste also showed extensive calcium silicate hydrates and calcium aluminate silicate hydrates but unrefined compared to plain cement paste. In overall, the expected synergistic reaction was significantly hindered due to the low quality of supplementary cementitious materials used. Hence, pre-treatments of SCMs must be considered to enhance their reactivity as good quality SCMs can become limited in the future.

• 한국세라믹학회지
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• 제37권5호
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• pp.438-443
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• 2000

This dissertation is focused on the study over the improvement for the early strength of belite-rich cement(BRC). For this purpose, the initial hydration behaviors according to addition of different calcium sulfate types were evaluated. From the observations by XRD, DSC and SEM, the BRC II and III with the addition of natural anhydrate and flue gas desulphurization(FGD) gypsum, respectively, formed much ettringite after 7 days more than the BRC I with the addition of chemical gypsum. The compressive strength of the BRC II and III developed outstandingly due to the formation of calcium aluminate hydrate within pores of hardened BRC paste. Especially, in the case of BRC III adding FGD with low impurities, the early as well as long term compressive strengths were shown very high, compared with other specimens.

• 한국세라믹학회지
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• 제16권3호
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• pp.164-168
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• 1979

In the previous paper, it was reported that formation of desirable calcium alunimate(CA) in clinker was considerably affected by sulfur-contaminated alumina which was prone to form a disadvantageous mineral, $C_4A_3S$. In this study, however, sulphate-free alumina cement was made from sulfur-free alumina refined from alunite and corresponding materials. The major minerals in the clinker were identified by X-ray diffraction patterns as calcium aluminate (CA), calcium dialuminate $(CA_2)$ and dicalcium alumino silicate $(C_2AS)$. The formation of CA was more effective with decreasing contents of silica to 2 per cent or less and sulfur in the refined alumina. Physical properties of prepared alumina cement such as setting time, stability and compressive strength were measured. The values were similar to those of commercial alumina cements.

• 한국세라믹학회지
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• 제17권4호
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• pp.217-221
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• 1980

Hydration of granulated blastfurnace slag-gypsum-$C_4A_3\bar{S}$ clinker/modified converter slag clinker was investigated to develop the cement of slag-gypsum system. In the hydration of granulated slag-gypsum-$C_4A_3\bar{S}$ system clinker, the hydrates such as ettringite, CSH gel and $AH_3$ gel were formed, and the strength of hardened body would be increased by forming compact microstructure. The modified converter slag clinker which contains alite and calcium aluminate was synthesized, and the hydration reactivity of the cement from this clinker, gypsum and granulated slag is similar to usual portland cement, and the hydrates were mainly CSH, ettringite, and $Ca(OH)_2$.