• Title/Summary/Keyword: fluosilicic acid

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Investigation on the Ratio and Type of Gypsum for Early Strength Improvement of Blast Furnace Slag Powder (고로슬래그 미분말의 초기강도 향상을 위한 석고 종류 및 첨가량 검토)

  • Jeong, Yong;Yoo, Jung-Hoon;Shin, Jae-Kyung
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.4
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    • pp.106-113
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    • 2010
  • We were tried to draw a conclusions related to additive amount of gypsum in blast furnace slag in the study. In the result, fluidity of concrete decreased with an increase of gypsum and was not satisfied with KS standard in the cases of natural gypsum and limestone sludge more than 2.6% addition. Early compressive strength of concrete containing desulfurized gypsum, fluosilicic acid gypsum and phosphoric acid gypsum were improved respectively but calcined lime sludge and lime powder were not influenced on strength. If available, additive gypsum should be managed less than 2.0% owing to low fluidity. In low temperature, fluosilicic acid gypsum was to advantages on the fluidity while desulfurized gypsum was in high temperature. There also are conclusions that additive gypsum was to be 2.6% in winter and in summer; it's to be fewer than 2.6%.

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Experimental Study on Engineering Properties of Concrete Using Fluosilicates Based Composite (규불화염계 복합 조성물을 혼입한 콘크리트의 공학적 특성에 관한 실험적 연구)

  • Yang Il-Seung;Yun Hyun-Do;Kim Do-Su;Khil Bae-Su;Han Seung-Gu
    • Journal of the Korea Concrete Institute
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    • v.17 no.5 s.89
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    • pp.769-774
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    • 2005
  • Fluosilicic acid(H2SiF6) is recovered as an aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded H3PO4 or HF. Generally, fluosilicates are the salts produced by the reaction of H2SiF6 and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. This study was performed to know mechanical properties and watertightness using fluosilicates based composite made from fluosilicates and other compounds. Mix proportions for experiments were modulated at 0.45 of water to cement ratio and $0.0-2.0\%$ of adding ratio of fluosilicates based composite. Evaluation for mechanical properties of concrete was conducted to know fresh state of concrete, hardening state of concrete, and watertightness. Evaluation for watertightness of concrete was carried out permeability, absorption test and porosity analysis. In addition. Scanning Electron Microscopy(SEM) and Energy Dispersive X-Ray(EDX) used for investigating micro-structure and atomic component distributed in hardened concrete. It is ascertained that characteristics of mechanical properties and watertightness was more improved than non-added because of packing role of fluosilicates based composite and pozzolanic reaction of soluble $SiO_2$. Also, concrete added fluosilicates based composite had a tendency to delay setting time and only $0.5\%$ addition of fluosilicates based composite delayed 150 minutes compared with non-added.

Durability and Crack Control of Concrete Using Fluosilicates Based Composite (규불화염계 복합 조성물을 혼입한 콘크리트의 균열제어 및 내구성)

  • Yun, Hyun-Do;Yang, Il-Seung;Kim, Do-Su;Khil, Bae-Su;Han, Seung-Gu
    • Journal of the Korea Concrete Institute
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    • v.18 no.1 s.91
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    • pp.57-64
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    • 2006
  • The crack presented in concrete structures causes a structural defect, the durability decrease, and external damages etc. Therefore, it is necessary to improve durability through the effort to control the crack. Fluosilicic acid($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicates prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. Mix proportions for experiment were modulated at 0.45 of water to cement ratio and $0.0{\sim}2.0%$ of adding ratio of fluosilicate salt based inorganic compound. To evaluate correlation of concrete strength and adding ratio of fluosilicate salt based inorganic compound, the tests were performed about design strength(21, 24, 27 MPa) with 0.5% of adding ratio of fluosilicate salt based inorganic compound. Applications of fluosilicate salt based inorganic compound to reduce cracks resulted from plastic and drying shrinkage, to improve durability are presented in this paper. Durability was evaluated as neutralization, chloride ion penetration depth, freezing thawing resistant tests and weight loss according reinforcement corrosion. It is ascertained that the concrete added fluosilicate salt based inorganic compound showed m ability to reduce the total area and maximum crack width significantly as compared non-added concrete. In addition, the durability of concrete improved because of resistance to crack and watertightness by packing role of fluosilicate salt based inorganic compound obtained and pozzolanic reaction of soluble $SiO_2$ than non-added concrete.

Changes in Hydration and Watertightness of Cement Containing Two-Component Fluosilicate Salt Based Chemical Admixture (2성분 규불화염계 혼화제가 첨가된 시멘트의 수화반응 및 수밀성 변화)

  • Kim, Jae-On;Nam, Jae-Hyun;Kim, Do-Su;Khil, Bae-Su;Lee, Byoung-Ky
    • Journal of the Korean Ceramic Society
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    • v.41 no.10 s.269
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    • pp.749-755
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    • 2004
  • Fluosilicic acid ($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicate salts prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicate salts to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. In this study, two-component fluosilicate salt based chemical admixtures (MZ) of $4\%,\;6\%$, and $8\%$ concentration were prepared by the reaction of $H_2SiF_6$ ($25\pm2\%$) and metal salts. The effect of concentration of MZ at a constant adding ratio on the hydration and watertightness of cement were investigated respectively. In a cement containing MZ, metal fluorides such as $CaF_2$ and soluble silica by hydrolysis were newly formed during hydration. The total porosity of the hardened cement was lower in the presence of U because of packing role of metal fluoride and pozzolanic reaction of soluble $SiO_2$. Consequently, the watertightness of the hardened paste containing MZ was more improved than non-added (plain) due to an odd hydration between cement and MZ.

Fluidity and Hydration Properties of Cement Paste Added Zinc Fluosilicate(ZnSiF6, aq.) (규불화아연(ZnSiF6, aq)이 첨가된 시멘트의 유동성과 수화특성)

  • Kim, Do-Su;Khil, Bae-Su;Lim, Heon-Seong;Nam, Jae-Hyun;Rho, Jae-Seong
    • Journal of the Korean Ceramic Society
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    • v.39 no.2
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    • pp.178-183
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    • 2002
  • Zinc fluosilicate ($ZnSiF_6$, 15% aqueous solution) was prepared using zinc oxide (ZnO) and fluosilicic acid ($H_2SiF_6$) by soluiton synthetic method. The fluidity and hydration properties of cement which was added $ZnSiF_6$ (aq.) as an additive for cement were studied. At water to cement ratio (W/C) equals to 0.45, the initial fluidity and slump loss of cement paste which the addition of $ZnSiF_6$ (aq.) was increased from 1.0% to 4.0% based on cement weight were investigated. Initial fluidity of cement paste was measured by mini-slump test and slump loss was examined by measuring the fluidity variation of cement paste with time elapsed from 0 min to 120 min at intervals 30 min. Also, the effect of $ZnSiF_6$ addition on the setting and hydration of cement paste when $ZnSiF_6$ increased in the addition range 1.0% to 3.0% were investigated. The fluidity of cement paste which was added 2.1% $ZnSiF_6$ (aq.) presented the highest value among all addition ranges. The setting time of cement paste was retarded gradually and the heat evolution of hydrated cement was reduced with the increasing of $ZnSiF_6$ addition.