• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.905-908
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• 2008

보통 포틀랜드 시멘트(Ordinary Portland Cement 이하 OPC)에 혼화재료를 사용하는 기존의 콘크리트는 초기 고강도를 발현하는데에 많은 어려움을 지니고 있다. 이에 본 연구에서는 그 방안으로 초미립자 시멘트(Micro Cement 이하 MC)의 사용에 대해 연구하고자 실험을 진행하였다. 실험 결과 MC는 OPC보다 플로우에서 취약함을 보였으나 초기강도에서 우수한 강도특성을 보였고 28일 강도에서도 OPC를 상회하는 것을 알 수 있었다. GBFS(granulated Blast Furnace Slag이하 GBFS라 함)의 경우 플로우는 감소하며, 초기강도는 증가하는 것으로 나타났다. MC의 경우 플라이애시 혼입시 강도발현에 있어 도움이 되지 않는 것으로 나타났다.

• Geomechanics and Engineering
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• 제31권4호
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• pp.409-422
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• 2022

The use of calcium sulfoaluminate (CSA) cement as a rapid-hardening cement admixture or eco-friendly alternate for ordinary Portland cement (OPC) has been attempted over the years, but the cost of CSA cement and availability of suitable aluminium resource prevent its wide practical application. To propose an effective ground improvement design in sandy soil, this study aims at blending a certain percentage of CSA with OPC to find an optimum blend that would have fast-setting behavior with a lower carbon footprint than OPC without compromising the mechanical properties of the cemented sand. Compared to the 100% CSA case, initial speed of strength development of blended cement is relatively low as it is mixed with OPC. It is found that 80% OPC and 20% CSA blend has low initial strength but eventually produces equivalent ultimate strength (28 days curing) to that of CSA treated sand. The specific OPC-CSA blend (80:20) exhibits significantly higher strength gain than using pure OPC, thus allowing effective geotechnical designs for sustainable and controlled ground improvement. Further parametric studies were conducted for the blended cement under various curing conditions, cement contents, and curing times. Wet-cured cement treated sand had 33% lower strength than that of dry-cured samples, while the stiffness of wet-cured samples was 25% lower than that of dry-cured samples.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.33-39
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• 1999

This study was conducted to confirm the effect of bypass dust on the hydration and mechanical properties of the cement pastes and mortar obtained from ordinary Portland cement (OPC), OPC-slag and OPC-fly ash system. The rate of heat evolution is accelerated with the content of By-pass Dust(BD). total heat evolution increased because alkali-chlorides activated the hydration of blended cement. Compressive strength and bound water content show maximum value at 5wt% By-pass Dust(BD) on each curing time in ordinary Portland cement and slag blended cement. Ca(OH)2 content of Ordinary Portland Cement increased as the content of BD and curing time. In blended cement, the formation of Ca(OH)2 is active at early hydration stage. By pozzolanic reaction, the content of Ca(OH)2 is decreased as curing time goes by. According to the BD content stable chlorides complex of Friedel's salt (C3A·CaCl2·10H2O) is created. Due to the hydration activation effect of chlorides and alkali we observed Type II C-S-H, which developed into densest microstructure.

• 한국세라믹학회지
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• 제44권9호
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• pp.477-482
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• 2007

The effect of the mixing ratio of compounds in a slag-OPC-Gypsum system on the physical properties of Slag cement is investigated in this study. $Na_2SO_4$ was used as an alkali activator. Blast furnace slag cement was prepared from a mixture of blast furnace slag, ordinary Portland cement and anhydride gypsum. The fluidity and the compressive strength according to the ratio of each mixture were analyzed in statistical analyses in order to discover the parameters influencing the fluidity and compressive strength. The results showed that the hydration of blast furnace slag took place with the addition of $Na_2SO_4$ and that column-crystalline ettringite was created as the main hydration product of the blast furnace slag. In addition, it was found that the compressive strength of blast furnace slag cement tends to increase when the ordinary Portland cement content is higher up to three days. However, it is known that the compressive strength tends to increase as the blast furnace slag content becomes higher with increases in the level of OPC after 28 days. As a result of this analysis, it is believed that the ordinary Portland cement content influences the initial compressive strength of blast furnace slag cement, and that in later days this is highly influenced by the slag content.

• 콘크리트학회논문집
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• 제16권4호
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• pp.557-564
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• 2004

This paper introduces a study carried out to investigate sodium sulfate attack caused by various reactive products. Experiments were performed on mortar and paste specimens made with ordinary Portland cement (OPC) conforming to KS L 5201 Type I. The water-cement ratios were varied from 0.35 to 0.55. It was found from the laboratory study that the water-cement ratio may be a key to control the deterioration of OPC matrix during sodium sulfate attack. Furthermore, X-ray diffraction (XRD) confirmed that ettringite, gypsum and thaumasite were the main products formed by sodium sulfate attack. These findings were well supported by thermal analysis through differential scanning calorimetry (DSC), and confirmed the long-term understanding that deterioration mechanism by sodium sulfate attack is a complicated process. Most importantly, deterioration due to sodium sulfate attack is characterized as the drastic reduction in compressive strength as well as the expansion (especially in cement matrix with a higher water-cement ratio).

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표회 논문집(I)
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• pp.76-81
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• 1998

The physical properties of cement sludge treated with hydrofluosilicic acid were investigated. The compressive strength of cement mortar substituted cement sludge was decreased than that of OPC(ordinary portland cement) mortar. Cement sludge, for improving its physical properties, was treated with hydrofluosilicic acid. And compressive strength of cement mortar substituted TCS was greatly improved than that of OPC mortar. Particularly, cement mortar substituted TCS had the higher value in water-proofness than of OPC.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.649-652
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• 2008

본 연구는 황토결합재로 시멘트를 대체함으로써 시멘트의 수화 반응 등에 의한 콘크리트 내부발열과 건조수축 문제의 해결 가능성을 연구하였다. 소형모형에서 HBC는 28일 압축강도가 18${\sim}$33MPa으로 보통강도 콘크리트의 강도를 발현할 수 있으면서, OPC에 비해 양생시 내부의 최고온도가 1/4 정도로 낮게 나타나고 건조수축 역시 HBC는 OPC에 비하여 50% 감소하였다. 대형시편에서도 HBC는 낮은 수화열로 인해 내부온도가 OPC에 비해 50% 낮게 나타났으며 건조수축 역시 60일 기점으로 OPC의 50% 정도의 수축률을 나타났다. 따라서 황토 결합재를 이용하여 매스 구조물을 제작하면 시멘트에 비하여 수화열과 건조수축의 문제를 해결하는데 상대적으로 유리할 것으로 사료된다.

• 한국세라믹학회지
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• 제26권5호
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• pp.609-616
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• 1989

For the development of high durable portland cement, it was tested that the some physical properties of ordinary portland cements (OPC) treated with 0.3-1.5wt.% asphalt and 0.5-1.0wt.% carbon black. From the results, the contact angles of water against cements treated with more than 0.6wt.% asphalt were increased over 80 degrees, the initial and the final setting times of cement paste were delayed about 20min. according to the every 0.3wt.% increase of asphalt. The first and the second pick heights of the hydration curve of the cement were considerabely decreased and the induction period of that was increased. And so, the cumulative hydration heat of the cement which was treated with 0.6wt.% asphalt and 0.5wt.% carbon black was lower about 10cal/g than that of ordinary portland cement during 42 hydration times.

• 한국농공학회지
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• 제40권5호
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• pp.59-67
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• 1998

The object of this study is to investigate the strength characteristics and the freeze-thaw resistance of high strength concrete incorporating fine blast furnace slag. Major experimental variables were the water/cement ratio, maximum size of coarse aggregate, and cement types such as ordinary portland and slag cement. The results were as follows ; The workability of fresh concrete incorporating fine blast furnace slag was better than that of OPC(ordinary Portland cement) in terms of slump. The freeze-thaw resistance showed better than that of OPC, keeping more than 90% of relative modules of elasticity after 506 cycles and showing only a hair crack at surface without serious damage. Thus, the fine blast furnace slag might be recycled at concrete to make high strength concrete at fields.

• 한국세라믹학회지
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• 제41권5호
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• pp.417-424
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• 2004

메톡시폴리에틸렌글리콜모노메타크릴레이트(MPEGMAA)와 메타크릴산(MAA)을 공중합시킨 폴리카복실레이트계 고유동화제(PCA)의 그라프트 사슬인 폴리에틸렌옥사이드(PEO)의 길이가 다를 경우, 보통포틀랜드시멘트(OPC)의 수화 반응에 미치는 영향을 Fourier Transform Infrared Spectroscopy(FT-IR), X-Ray Diffraction(XRD)과 Differential Scanning Calorimetry (DSC)를 이용하여 조사하였다. PCA의 그라프트 사슬의 길이에 따라 초기 재령에서 수화 반응에 미치는 영향은 달라지나, 장기 재령에서는 큰 차이가 없었다. 또한 PCA가 첨가된 경우의 Ca(OH)$_2$의 상대 피크 강도의 비(I[001］/I［101］)는 OPC에 비해 감소하였다.