• 대한토목학회논문집
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• 제32권6A호
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• pp.427-435
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• 2012

본 연구는 보통 및 혼합시멘트계 모르타르의 황산염침식 저항성에 대한 노출조건의 영향을 평가하기 위하여 수행되었다. 모르타르를 제조한 후, 3종류 노출조건, 즉 1) 연속 완전침지, 2) 연속 반침지 및 3) 건습반복 조건에서 모르타르의 팽창, 강도, 밀도 등 역학적 성능변화를 52싸이클까지 주기적으로 관찰하였다. 실험결과에 따르면, 연속 반침지(Exposure B) 조건에 노출된 OPC 모르타르가 황산염침식에 의한 다량의 균열이 발생하므로써, 연속 완전침지 조건 및 건습반복 조건에 노출된 모르타르에 비하여 성능저하가 상대적으로 크게 나타났다. 그러나, 고로슬래그미분말 및 실리카퓸을 사용한 혼합시멘트계 모르타르는 낮은 투수성 및 조직구조의 밀실화효과에 의하여 노출조건에 관계없이 우수한 황산염침식 저항성을 보였다. 따라서, 콘크리트 구조물이 황산염침식 환경에 노출될 경우, 노출조건에 대한 고려가 반드시 이루어져야 할 것으로 판단된다.

• Geomechanics and Engineering
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• 제10권6호
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• pp.807-826
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• 2016

In this study, aiming to investigate the effects of sulfate attack on cement stabilized highly plastic clay; an experimental study was carried out considering the effects of cement type, sulfate type and its concentration, cement content and curing period. Unconfined compressive strength and chloride-ion penetration tests were performed to obtain strength and permeability characteristics of specimens cured under different conditions. Test results were evaluated along with microstructural investigations including SEM and EDS analyses. Results revealed that use of sulfate resistance cement instead of normal portland cement is more plausible for soils under the threat of sulfate attack. Besides, it was verified that sulfate concentration is responsible for strength loss and permeability increase in cement stabilized montmorillonite. Finally, empirical equations were proposed to estimate the unconfined compressive strength of cement stabilized montmorillonite, which was exposed to sulfate attack for 28 days.

• Journal of Microbiology and Biotechnology
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• 제12권5호
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• pp.849-853
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• 2002

Metal ions have an adverse effect on anaerobic digestion. In an acetate degradation test of upflow of anaerobic sludge blanket granules with $Cu^{2+}$, not all of the acetate that disappeared was stoichiometrically converted to methane. In the presence of 400 mg/g-VSS (volatile suspended solids) $Cu^{2+}$, only 26% of the acetate consumed was converted to methane. To study acetate conversion by other anaerobic microorganisms, sulfate and nitrate reductions were investigated in the presence of $Cu^{2+}$ Sulfate and nitrate reductions exhibited more resistance to $Cu^{2+}$than methanogenesis, and the granules reduced 2.2 mM and 5.4 mM of nitrate and sulfate, respectively, in the presence of 400 mg/g-VSS copper ion. However, the acetate degraded by sulfate and nitrate reductions was only 24% of the missing acetate that could have been stoichiometrically converted to $CO_2$. Accordingly, 76% of the acetate consumed appeared to have been converted to other unknown compounds.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.425-428
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• 2000

When concrete structures are exposed to sulfate or marin environments, sulfate ions penetrated into concrete make it deteriorate. An accelerated test under potential difference method was performed to evaluate not only the sulfate ion diffusivity in ordinary portland cement and ground granulated blast-furnace slag cement concretes but the effect of slag replacement and water-cement ratio on the sulfate ions diffusivity. As the result of this study, we assumed the sulfate ion diffusivity was significantly related with total passed charge and initial current in concrete. Moreover sulfate ions penetration resistance of ordinary portland cement concrete was superior to that of ground granulated blast-furnace slag cement concrete.

• 한국세라믹학회지
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• 제44권9호
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• pp.465-470
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• 2007

This paper presents an experimental study of the sulfate resistance of mortars and pastes exposed to sodium sulfate solutions up to one year. In order to check deterioration modes due to sulfate attack, the sodium sulfate solution was varied at three concentration steps (3,380, 10,140 and 33,800 ppm of $SO_4^{2-}$ ions), and maintained at ambient temperature. The tests include a visual examination, expansion and compressive strength loss measurements as well as x-ray diffraction tests. The experimental data indicated that the use of cement with a low $C_3A$ content and low silicate ratio has a beneficial effect on the sulfate attack of mortars. In contrast, the mortars with a high $C_3A$ content and high silicate ratio became severely degraded due to the formation of ettringite, gypsum and/or thaumasite in the cement matrix.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.683-688
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• 2001

In case of constructing the concrete structures under seawater environment, the concrete suffers from deterioration due to penetration of various ions such as chloride, sulfate and magnesium in seawater. Tn the present study, Immersion tests with artificial seawater were carried out to investigate the resistance to seawater attack of antiwashout underwater concrete. From the results of compressive strength, it was found that blended cement concrete due to mineral admixtures such as fly ash(FA) and ground granulated blast-furnace slag(SGC), were superior to ordinary portland cement concrete with respect to the resistance to seawater attack. Moreover, XRD analysis indicated that the formed reactants of ordinary portland cement paste by sulfate and magnesium ions led to the deterioration of concrete. As expected, however, the blended cements with FA or SGC have a good resistance to seawater attack. This paper would discuss the mechanism of seawater deterioration and benefical effects of antiwashout underwater concretes with mineral admixtures.

• Corrosion Science and Technology
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• 제15권6호
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• pp.259-264
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• 2016

With a specially designed electrochemical cell, the changes in impedance behavior for Inconel 600 and aluminide diffusion coatings under molten sulfate film with thermal cycles (from $800^{\circ}C$ to $350^{\circ}C$) were monitored with electrochemical impedance measurements. It was found that corrosion resistance for both materials increased with lower temperatures. At the same time, the state of molten salt was also monitored successfully by measuring the changes in impedance at high frequency, which generally represents the resistance of molten salt itself. After two thermal cycles, both Inconel 600 and aluminide diffusion coatings showed excellent corrosion resistance. The results from SEM observation and EDS analysis correlated well with the results obtained by electrochemical impedance measurements. It is concluded that electrochemical impedance is very useful for monitoring the corrosion resistance of materials under molten salt film conditions even with thermal cycles.

• 한국건축시공학회지
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• 제22권6호
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• pp.663-672
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• 2022

왕겨분말 혼입 지오폴리머의 황산마그네슘 저항성을 평가하기 위해, 비교대상으로 보통 콘크리트, 실리카 흄 혼입 콘크리트, 플라이애시와 고로슬래그를 혼입한 2성분계 지오폴리머를 비교대상으로 선정하여 황산마그네슘 용액침지시험을 실시하였다. 재령별 압축강도를 이용하여 산출한 황산염 열화지수는 황산마그네슘 용액 침지재령 56일에서 보통 콘크리트의 경우 6.75%이었으나, 왕겨분말 혼입 지오폴리머의 경우 모든 시편에서 1.28~1.87%의 낮은 수준을 보였다. 이는 실리카 흄 혼입 콘크리트의 2.48%보다 낮게 나타나 왕겨분말이 황산마그네슘 침식 저항성에 큰 도움이 되는 것으로 판단된다. 또한, 콘크리트 내부 미세균열과 외부열화에 대한 평가를 위해 시험체의 중량변화율의 경우 황산마그네슘 용액 침지재령28일 이후부터 모든 시험체에서 중량이 크게 변화하였으며, 침지재령 56일에서 보통 콘크리트는 3.78%로써 황산마그네슘에 의한 열화가 가장 심각한 수준임을 알 수 있었다. 그러나, 왕겨분말 혼입 지오폴리머의 경우 0.9~1.45%의 작은 중량변화율을 보였다. 지오폴리머 내의 에트린자이트 생성 정도를 X선 회절 분석법을 통하여 확인하였으며, 왕겨분말 혼입 지오폴리머에서는 소량으로 생성되어 있는 것을 확인할 수 있어, 황산마그네슘 침식 저항성에 높은 상관성이 있음을 알 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.421-424
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• 2008

본 연구에서는 산 및 황산염 저항성에 미치는 시멘트 종류의 영향을 평가하기 위하여 물-결합재 비 32% 및 43%에 대해서 보통 포틀랜드 시멘트(OPC), 2성분계 시멘트(BBC), 및 3성분계 시멘트(TBC)와 같은 3종류의 시멘트를 사용한 콘크리트 공시체를 제작하였다. 제작된 콘크리트 공시체에 대해서 JSTM C 7401에 따라 5% 황산, 10% 황산나트륨 나트륨 및 10% 황산마그네슘 용액에 의한 침지실험을 통하여 재령에 따른 외관 변화 및 질량 감소율을 평가하였다. 재령 91동안의 침지실험 결과로부터, 콘크리트의 산 및 황산염에 대한 저항성은 물-결합재비가 감소할수록 증가하고, BBC와 TBC 콘크리트가 OPC 콘크리트보다 우수한 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.755-760
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• 2002

The concrete structures in marine environment has been used type V cement(sulfate-resisting Portland cement), but according to the study results reported recently, the question has been raised for effect of the resistance to salt attack of the concrete using type V cement. It is increased the demands on the use of mineral admixtures such as fly ash, ground granulated blast-furnace slag instead of type V cement in order to improve the durability of concrete structures. Therefore, this study focused on the durability evaluation of concrete containing fly ash under marine environment, and the tests such as salt attack, carbonation, sulfate attack, and freezing-thawing were performed. Test results showed t]hat the resistance to salt attack, sulfate attack and freezing-thawing was improved, and the carbonation was in some disadvantage compared with normal concrete. Nevertheless, the durability of fly ash concrete would be maintained during the service life of structures.