• 한국세라믹학회지
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• 제33권12호
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• pp.1331-1338
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• 1996

In order to investigate the reaction in the system of fly ash-sulfuric acid-calcium hydroxide the hydrates were produced by the addition of Ca(OH)2 to fly ash activated with sulfuric acid at various temperatures. And then they were characterized by XRD. SEM and TG-DTA. It was found that in the reaction of fly ash with sulfuric acid fly ash was not decomposed but Al2O3 and SiO2 component in it were activated. The addition of calcium hydroxide into this system resulted in the formation of ettringite and calcium silicate hydrate (C-S-H) As the concentration of sulfuric acid and reaction temperature increased the amount of calcium hydroxide decreased fast. At this time gypsum produced by the reaction calcium hydroxide with sulfuric acid was consumed to form ettringite. Accordingly the formation of ettringite increased with calcium hydroxide and reaction time. And it showed faster than the formation of C-S-H.

• 한국지반환경공학회 논문집
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• 제13권2호
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• pp.59-65
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• 2012

본 연구에서는 비소 오염 토양의 비소 처리를 위해 고형화/안정화 공법을 적용하였으며, 4가지 종류의 바인더(시멘트, 영가철(Zero Valent iron, ZVI), monosulfate와 ettringite(시멘트계 합성물질))를 이용하였다. 1 N HCl 용출법을 통해 비교한 결과 바인더 함유량 20%에서, 시멘트(71.41%) > monosulfate(47.45%) > ettringite(46.36%) > 영가철(33.08%)의 비소가 용출되었다. 또한, 시멘트에 첨가제(monosulfate, ettringite, calcium sulfoaluminate, CSA)를 혼합하여 바인더를 제작하여 비소 저감 능력을 평가하였다. 1N HCl 용출법을 통해 비교한 결과 3가지 혼합바인더 모두 혼합비 4:1에서 최대의 비소농도 저감효과를 나타냈으며, CSA(86.27%) > monosulfate(84.78%) > ettringite(84.71%) > 시멘트(71.41%)의 비소를 안정화하여 기존의 시멘트만 단독으로 사용했을 경우보다 더 높은 비소(As(V)) 저감 능력을 가지고 있는 것으로 평가된다.

• 대한토목학회논문집
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• 제33권4호
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• pp.1463-1469
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• 2013

고화제로 사용되는 포틀랜드 시멘트와 2가철을 이용하여 염소계 유기화합물을 탈염소화 시키는 기술은 많은 연구로부터 알려져 왔다. 하지만 TCE (trichloroethylene)의 탈염소화에 관계하는 명확한 유효물질 및 기작 규명은 요원한 상태이다. 많은 연구에서 ettringite와 monosulfate와 같은 시멘트 수화물질이 TCE의 탈염소화 반응에 관여할 가능성을 보고한 바 있다. 따라서 본 연구에서는 TCE의 탈염소화 반응에 유효물질로 예상 되어왔던 ettringite와 monosulfate를 별도로 합성하여, TCE 제거 실험을 수행함으로서 기존 시멘트/2가철을 사용한 TCE 분해제거에 관계하는 명확한 유효물질 및 기작을 규명 하고자 하였다. 실험결과, $Fe^{3+}$ 및 $Al^{3+}$로 구성된 ettringite, monosulfate 합성에 성공하였고, 이후 2가철을 첨가하여 TCE 분해실험에서 합성물의 분해능을 확인하였지만 뚜렷한 제거가 나타나지 않았다. 이는 기존문헌의 예상과는 상반된 결과를 나타냈으며, 실험결과를 통해 시멘트/2가철을 사용한 TCE 제거 실험의 분해기작을 예상할 수 있었다. 예상 되는 분해기작으로는 ettringite 및 monosulfate 외의 시멘트 수화물에 의한 것과 C3A외의 시멘트 클링커 화합물 그리고 시멘트 내 trace metal에 의한 영향일 것으로 추측하였다.

• 콘크리트학회논문집
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• 제14권5호
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• pp.631-637
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• 2002

This paper deals with hydration properties of the OPC with CSA-system expansive materials. In OPC using CSA, that was formed monosulfate for the main part. but In OPCs using CSA and gypsum, using CSA and gypsum and lime, that were formed ettringite for the main part. On the shrinkage ratio, the former is larger than the latter And CSA-system with gypsum and lime is smallest of all systems. According to dimension of shrinkage ratios are as follows; OPC using CSA only＞ OPC only＞ OPC using CSA and gypsum＞ OPC using CSA, gypsum and lime. And "R"s are 0.32, 0.37, 0.8, 0.8, 0.8 each others. In OPC with CSA-system expansive materials, we know that expansive properties were depend upon the value of "R". "R" means supplying quantities about demanding quantities for ettringite. In the case of expansive materials with CSA-system and lime, it is to be rich Ca(OH)$_2$ in the solution. so, it is formed small ettringite as the needle shapes. they are contribute to expansive.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.349-352
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• 2005

In this work, effects of limestone powder on hydration of $C_3A-CaSO_4\cdot2H_2O$ system was discussed based on the XRD Quantitative analysis, and the possibility of Delayed Ettringite Formation was also discussed. The early hydration of $C_{3}A$ was delayed by addition of $CaCO_{3}$ powder. The delay effect was enhanced by increasing of $CaCO_{3}$ content and finer powder of $CaCO_{3}$ addition. After consumption of $CaSO_4\cdot2H_2O$, the reaction of $CaCO_{3}$ is started. Delayed Ettringite Formation would take place because monosulfoaluminate is not stable in presence of $CaCO_{3}$. In order to prevent the delayed ettringite formation in $C_3A-CaSO_4\cdot2H_2O-CaCo_3$ system, the reduction of monosulfoaluminate formation is important. Therefore, by increasing the amount of $CaCO_{3}$ addition and finer $CaCO_{3}$ powder addition, the delayed ettringite formation can be prevented.

• 한국세라믹학회지
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• 제39권4호
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• pp.401-408
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• 2002

무기질 지연제인 붕산 첨가시 OPC의 수화지연 특성을 연구하였다. 붕산 무첨가시에는 수화시작 수분안에 침상형의 Ettringite가 활발하게 생성하나 붕산을 첨가함에 따라 Ettringite와 $Ca(OH)_2$의 형성은 지연되었다. 이는 pH의 저하에 따른 Al이온의 안정화로 수화반응이 지연되기 때문이다.

• Environmental Engineering Research
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• 제24권1호
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• pp.24-30
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• 2019

The present study explores the applicability of response surface methodology (RSM) in conjunction with central composite design (CCD) matrix to statistically optimize ettringite crystallization process for the removal of sulphate from landfill leachate. A three factor-five coded level CCD with 20 runs, was performed to estimate the best fitted model. The RSM results indicated that the fitted quadratic regression model could be appropriate to predict sulfate removal efficiency. The pH was identified as the most dominant parameter affecting sulphate removal. 61.6% of maximum sulphate removal efficiency was obtained at pH of 11.06 for a 1.87 of $Ca/SO_4$ and 0.51 of $Al/SO_4$ molar ratios. The operating cost for ettringite crystallization at optimized conditions was calculated to be 0.52 $/$m^3$. The significance of independent variables and their interactions were tested by analysis of variance. Scanning electron microscope (SEM) and SEM coupled with energy dispersive X-Ray spectroscopy results confirmed the formation of ettringite crystal and were used to describe its morphology features.

• 한국세라믹학회지
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• 제48권6호
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• pp.584-588
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• 2011

In this work, effects of limestone powder on hydration of $C_3A-CaSO_4{\cdot}2H_2O$ system was discussed based on the XRD Quantitative analysis, and the possibility of Delayed Ettringite Formation was also discussed. The early hydration of $C_3A$ was delayed by addition of $CaCO_3$ powder. The delay effect was enhanced by increasing of $CaCO_3$ content and finer powder of $CaCO_3$ addition. After consumption of $CaSO_4{\cdot}2H_2O$, the reaction of $CaCO_3$ is started. Delayed Ettringite Formation would take place because monosulfoaluminate is not stable in presence of $CaCO_3$. In order to prevent the delayed ettringite formation in $C_3A-CaSO_4{\cdot}2H_2O-CaCO_3$ system, the reduction of monosulfoaluminate formation is important. Therefore, by increasing the amount of $CaCO_3$ addition and finer $CaCO_3$ powder addition, the delayed ettringite formation can be prevented.

• 한국세라믹학회지
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• 제32권8호
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• pp.873-880
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• 1995

In order to prepare the modified belite (C2S-C4A3S-C4AF-CS) cement with low energy, clinkers were synthesized by converter slag, limestone, gypsum and clay. The synthesized clinkers were characterized and the hydration processes were investigated by XRD, SEM and microconduction calorimetry. The hydrates were mainly C-S-H and ettringite. The needle-like ettringite formed by the hydration of C4A3S at the early stage of hydration was filled in the inner vacant spaces of the hardened body and it might contribute to the rapid-hardening phenomena. The hardened body became stronger due to the hydration of C2S at the later period. The compressive strengths of the cement-3 mortars hydrated for 3, 7 and 28 days were 115, 128 and 211 Kgf/$\textrm{cm}^2$, respectively.

• 한국세라믹학회지
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• 제37권4호
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• pp.388-394
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• 2000

The C4A3S clinker was prepared by the solid-state reaction. The mixture of raw materials; calcite, kaoline and gypsum, was fired at 135$0^{\circ}C$ for 1hr and cooled rapidly in air. C4A3S type expansive was made with C4A3S clinker, CaO and CaSO4. The cement replaced by 10 wt.% C4A3S type expansive was investigated by the measurement of the strength(compressive, tensile, flexural) and length change at various curing conditions. Hydration products were mainly ettringite, monosulfate and Ca(OH)2. The densification and the expansion due to the formation of ettringite during the hydration increased strength and reduced the drying shrinkage of hardened cement.