• 제목/요약/키워드: chlorides

검색결과 454건 처리시간 0.025초

Resistance of Cementitious Binders to Chloride Induced Corrosion of Embedded Steel by Electrochemical and Microstructural Studies

  • Song, Ha-Won;Ann, Ki-Yong;Kim, Tae-Sang
    • Corrosion Science and Technology
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    • 제8권2호
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    • pp.74-80
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    • 2009

  • The high alkaline property in the concrete pore solution protects the embedded steel in concrete from corrosion due to aggressive ions attack. However, a continuous supply of those ions, in particular, chlorides altogether with a pH fall in electrochemical reaction on the steel surface eventually depassivate the steel to corrode. To mitigate chloride-induced corrosion in concrete structures, finely grained mineral admixtures, for example, pulverized fuel ash (PFA), ground granulated blast furnace slag (GGBS) and silica fume (SF) have been often advised to replace ordinary Portland cement (OPC) partially as binder. A consistent assessment of those partial replacements has been rarely performed with respect to the resistance of each binder to corrosion, although the studies for each binder were extensively looked into in a way of measuring the corrosion rate, influence of microstructure or chemistry of chlorides ions with cement hydrations. The paper studies the behavior of steel corrosion, chloride transport, pore structure and buffering capacity of those cementitious binders. The corrosion rate of steel in mortars of OPC, 30% PFA, 60% GGBS and 10% SF respectively, with chloride in cast ranging from 0.0 to 3.0% by weight of binder was measured at 7, 28 and 150 days to determine the chloride threshold level and the rate of corrosion propagation, using the anodic polarization technique. Mercury intrusion porosimetry was also applied to cement pastes of each binder at 7 and 28 days to ensure the development of pore structure. Finally, the release rate of bound chlorides (i.e. buffering capacity) was measured at 150 days. The chloride threshold level was determined assuming that the corrosion rate is beyond 1-2 mA/$m^3$ at corrosion and the order of the level was OPC > 10% SF > 60% GGBS > 30% PFA. Mercury intrusion porosimetry showed that 10% SF paste produced the most dense pore structure, followed by 60% GGBS, 30% PFA and OPC pastes, respectively. It was found that OPC itself is beneficial in resisting to corrosion initiation, but use of pozzolanic materials as binders shows more resistance to chloride transport into concrete, thus delay the onset of corrosion.

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$\beta$-Ketoacetoanilide 염화물의 조합 라이브러리 합성 및 주요 식물병원균에 대한 항균활성 (Synthesis of combinatorial library of $\beta$-ketoacetoanilide chlorides and their antifungal activity against main plant pathogens)

  • 한호규;남기달;배수열;양범승;이선우;조광연
    • 농약과학회지
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    • 제8권1호
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    • pp.8-15
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    • 2004

  • 베타-케토아세트아닐라이드 염화물 유도체의 합성 및 이들 화합물의 대표적인 6종의 식물병원균에 대한 항균력을 조사하였다. Carousel Reaction Stations 장치를 이용하여 조합 합성 기법을 통하여 키틴 이합 체를 염소와 아닐린 유도체와 차례로 반응시켜 89종의 베타-케토아세트아닐라이드 클로라이드 유도체를 얻었다. 합성된 화합물 라이브러리의 항균력(in vivo)을 벼 도열병, 벼 잎집무늬마름병, 토마토 잿빛곰팡이병, 토마토 잎마름역병, 밀 붉은녹병, 보리 흰가루병 등의 주요 식물병에 대한 항균력 시험을 수행하였다. 일반적으로 페닐기의 4위치 (para) 치환체가 존재하는 화합물의 경우에 선택적으로 토마토 잎마름역병을 방제하였다.

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