• Title/Summary/Keyword: Chlorides

Search Result 454, Processing Time 0.02 seconds

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
    • /
    • v.8 no.2
    • /
    • pp.74-80
    • /
    • 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.

  • PDF KSCI

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

  • Hahn, Hoh-Gyu;Nam, Kee-Dal;Bae, Su-Yeal;Yang, Bum-Seung;Lee, Seon-Woo;Cho, Kwang-Yun
    • The Korean Journal of Pesticide Science
    • /
    • v.8 no.1
    • /
    • pp.8-15
    • /
    • 2004

  • A synthesis of new $\beta$-ketoacetoanilide chloride derivatives and anti fungal activity of these compounds library against 6 typical plant pathogens were described. Reaction of ketene dimer with chlorine followed by treatment of aniline derivatives gave 89 kinds of the corresponding $\beta$-ketoacetoanilide chlorides through combinatorial synthetic technology using Carousel Reaction Stations. Evaluation of antifungal activity (in vivo) of this chemical library against rice blast, rice sheath blight, tomato aray mold, tomato late blight, wheat leaf rust and barley powdery mildew was carried out. In general, $\beta$-ketoacetoanilide chlorides which present a substituent at 4 in phenyl group(para) of the compounds showed selective control activity against tomato late blight caused by Phytophthora infestans.

  • PDF KSCI