• Title, Summary, Keyword: black-coring

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Analysis of Pore Characteristics on the Porous Body-Porosity Index of Ic and Is in Light Weight Aggregate (다공체 소지의 기공 특성 분석-경량골재에서의 기공지수 Ic와 Is에 대하여)

  • 권영진;이기강
    • Journal of the Korean Ceramic Society
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    • v.41 no.2
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    • pp.176-181
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    • 2004
  • EAF (Electric Arc Furnace) dust is classified as special wastes containing heavy metal contaminants may cause to damage an environment such as underground water contamination if they were not treated properly. For reutilizing the EAF dust, the porous body was made from EAF dust/clay composition system, and analyzed pore characteristics. It was found that a light-aggregate body was made up two different microstructures. One was non-black and dense microstructure which located near surface, and the other was black and porous microstructure (black coring) which located inner part. For systematizing the relationship of the black-coring area and the bloating degree, we defined the Ic(core index) and Is(shell index). It was found that the optimal bloating conditions of artificial light-weight aggregate were more than 0.5 of Ic and 0.4 of Is.

Manufacturing of Artificial Lightweight Aggregates using a Coal Fly Ash Discharged from Fluidized Bed Combustor (유동층(流動層) 연소기(撚燒器)로 부터 발생(發生)된 석탄(石炭) 비산(飛散)재를 이용(利用)한 인공경량골재(人工輕量骨材) 제조(製造))

  • Kang, Min-A;Kang, Seung-Gu
    • Resources Recycling
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    • v.20 no.1
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    • pp.54-60
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    • 2011
  • The spherical artificial aggregates (AAs) with a diameter of 8 mm, which contains fly ashes discharged from the fluidized bed combustion in a thermal power plant and clay were manufactured by direct sintering method at $1050{\sim}1250^{\circ}C$ for 10 minutes. The effect of fly ash contents on the bloating phenomenon in the AAs was analyzed. The AAs containing fly ash of the amount under 50 wt% showed the black-coring and bloating phenomena. The AAs containing fly ash of the amount over 5Owt%, however, the specific gravity was increased and the color of specimens fully changed to black. These color change phenomena were caused from the formation of FeO by the reduction reaction of almost $Fe_2O_3$ component by the excessive reducing atmosphere formed simultaneously with the rapid emission of the gases generated from the high contents of unburned carbon of with increasing the added fly ash amount. Specific gravity was decreased as fly ash contents increased in the case of sintering at the same temperature condition. Water absorption of all specimens except of the specimens containing 10 wt% fly ashes decreased with increasing sintering temperature. These were because a liquid phase was formed as the increasing the sintering temperature. In the case of the specimens manufactured in this study containing fly ashes discharged from the fluidized bed combustor in a the thermal power plant and 10~90 wt% of clay, the specific gravity was 0.9~1.8 and the water absorptivity was 8~60%, therefore it is considered that those results can be applied to the light or heavy aggregates.

Influence of red mud additive on lightening of artificial aggregates containing coal bottom ash (석탄바닥재가 포함된 인공골재의 경량화에 미치는 적니 영향)

  • Kang, Min-A;Kang, Seung-Gu
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.21 no.1
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    • pp.41-46
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    • 2011
  • The artificial aggregates (AAs) composing of 2 wastes, coal bottom ash and dredged soil (7 : 3, weight ratio) were fabricated as a function of red mud contents,0~30 wt% using direct sintering method at $1050{\sim}1250^{\circ}C$ for 10 min, and those physical properties were evaluated. Especially, in order to analyze the red mud addition effect on the bloating phenomenon of AAs manufactured, the specific gravity and water absorption were measured and studied linked with the microstructural observation results. The lightening of AAs was enhanced due to increased bloating with increasing temperature and red mud contents. The AAS sintered at $1050{\sim}1150^{\circ}C$ showed well-developed black-coring structure, but for the specimens containing red mud sintered over $1200^{\circ}C$ generated excessive liquid and gas caused by reduction of $Fe_2O_3$, thus the black-coring part was gradually burst open out of shell of AAs. Particularly, all specimens containing 30 wt% red mud was burst up when sintered over $1100^{\circ}C$. The AAs containing no red mud sintered at $1200^{\circ}C$ had a specific gravity of about 1.2 and those containing 20 wt% had below 1.0 which are characters of lightweight aggregate.