• Title/Summary/Keyword: Fume

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Veriation of Pore Structure of High Strength Concrete Including Silica Fume Exposed to High Temperature (고온에 노출된 실리카퓸 혼입 고강도 콘크리트의 공극구조 변화)

  • Song Hun;Soh Yang-Seob
    • Journal of the Korea Concrete Institute
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    • v.16 no.5 s.83
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    • pp.597-604
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    • 2004

  • This work involves quantitatively investigating the correlation between reductions in strength and variations in pore structure under high temperature that can be utilized as estimation for predicting the inner temperature of member damaged by fire. The experimental results were remarkedly affected by micro-filling effect of silica fume and the different water-binder ratios. The increase of the exposure temperature caused the increase of porosity, which resulted from the reason that evaporable water in gel pore or capillary pores as well as chemically bound water was eliminated from hardened cement paste due to the dehydration of C-S-H and $Ca(OH)_2$. Thermal shrinkage of hardened cement paste gives rise to micro-crack, which cause the increase of porosity. Based on the experimental result that the increase of porosity is in charge of exposure temperature, how porosity is distributed can predict temperature-time history and assess the performance of concrete damaged by fire.

  • https://doi.org/10.4334/JKCI.2004.16.5.597 인용 PDF KSCI

Durability Performance Evaluation On Early-Aged Concrete with Rice Husk Ash and Silica Fume (Rice Husk Ash와 실리카퓸을 혼입한 초기재령 콘크리트의 내구성능 평가)

  • Saraswathy, Velu;Kwon, Seung-Jun
    • Journal of the Korea Concrete Institute
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    • v.27 no.4
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    • pp.343-351
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    • 2015

  • Currently, lots of researches have been performed for reducing cement usages due to increasing social/engineering problems caused by $CO_2$ emission. Supplementary cement materials like fly ash, slag, and silca fume are usually employed for cement replacement, and nowadays rice husk ash (RHA) is widely studied for enhancement of concrete performance as mineral admixture. In this paper, concrete samples with RHA and SF which is known for its engineering advantages are prepared and a resistance to chloride attack is evaluated in early-aged concrete. For the work, replacement ratios of 10~30% for RHA concrete and 2~8% for SF concrete are considered, and various durability tests such as density, void, sorptivity, current measurement, and chloride diffusion coefficient are performed including mechanical test like compressive and tensile strength. Replacement of RHA 10~15% shows better improvement of corrosion resistance and strength than that of SF 2~4% and normal concrete, which shows a strong applicability for utilization as construction materials.

  • https://doi.org/10.4334/JKCI.2015.27.4.343 인용 PDF KSCI

Evaluation of Carcinogenic Metals in Particulate Using New ISO Standard Method (국제표준규격에 의한 입자상 물질 중 발암성 금속의 평가)

  • Park, Ji Young;Yoon, Chung Sik;Ha, Kwon Chul
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.18 no.2
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    • pp.99-107
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    • 2008

  • We quantified the human carcinogenic metals (chromium, nickel) in fumes from flux cored arc welding using stainless steel (FCAW/SS) wires. Zinc and calcium were also quantified because of their possibility of zinc chromate and calcium chromate, respectively. Welding was performed in an American Welding Society standard fume collection chamber. Insoluble and soluble forms of metals were analyzed by ISO 15202 method. Total chromium (insoluble+soluble) content and total nickel content were lower in FCAW/SS fumes (4.65%, 1.05%, respectively)than in stainless steel content (ca. 18%, 8%,respectively). Insoluble fraction in total chromium was 79.8 (range 64.5~95.1)% and 94.4(range 90.1~98.1)% in total nickel. Atomic emission spectroscopy used in this study does not differentiate the chromium valence status while ACGIH defines its carcinogenicity according to the valence status. From this study and previous study, we estimated the hexavalent chromium content in FCAW/SS was 0.2~1.1% and about 85% of them was soluble. The content of zinc and calcium, which can be existed as chromate forms, was low (0.02 %, 0.04% respectively) in FCAW/SS. Exposure assessment for zinc chromate and calcium chromate is possible because chromium in both compounds is used as a surrogate even though it is not well known that what compounds of zinc and calcium are formed in welding fume.

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