• Title, Summary, Keyword: Fly Ash

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Fundamental Study on Evaluation method of Activity Factor of Fly Ash (플라이애시의 활성도지수 평가에 관한 기초적 연구)

  • Park, Sang-Joon
    • Journal of the Korea Institute of Building Construction
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    • v.8 no.5
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    • pp.59-65
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    • 2008
  • In the evaluation method of KS on the activity factor of fly ash, same amount of cement should be replaced with fly ash. Therefore, contradictory effects on concrete strength exist, i. e. strength decease due to low content of cement and strength increase of strength due to filling-pore-function of fly ash. European Committee for Standardization (CEN) specifies the method 1 to 4. adding fly ash without reducing the content of cement, for the evaluation method on activity factor of fly ash. This study investigates the applicability of the method 2 of CEN to mix design of concrete. The followings are derived ; There is a key ratio of f)y ash mixing which enhances the incremental ratio of mixing water to improve fluidity of mortar. The incremental ratio of mixing water is maximized about 11% ratio of fly ash mixing. Compressive strength most slightly increases at that ratio of fly ash mixing. Activity factor of fly ash increases as water-cement ratio becomes low and contents of fly ash becomes high. Moreover, quality of fly ash and condition of mix design affect the applicable amount of fly ash and available range of water-cement ratio. However, this method has some problems for practical purpose because activity factors of fly ash for some cases are over 1.0. Further research should be conducted to develop more useful method of evaluating activity factor of fly ash.

Effect of fly ash on the physico-chemical properties (Fly Ash가 토양(土壤)의 물화학성(物化學性)에 미치는 영향(影響))

  • Park, Man;Hur, Nam-Ho;Choi, Jung
    • Korean Journal of Environmental Agriculture
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    • v.10 no.2
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    • pp.133-137
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    • 1991
  • The inorganic constituents in flay ash such as Ca, Mg, Al and Si were extracted by water and 0.5N-Acetic acid, and changes of the physical properties of the fly ash-treated soils were examined to find out the effect of fly ash on the chemical and physical properties of the soils. The dominant day minerals of fly ash were quartz and mullite. More inorganic constituents were extracted from the fly ash by acetic acid than by water. Si and A1 in fly ash were hardly extracted by water. Addition of fly ash to soil below 10%(W/W) caused improvement in the water permeability and the field moisture capacity of the soil, but did not influence the shrinkage and hardness of the soil. Therefore, it was apparent that the effect of the fly ash on the chemical and physical properties of the soils greatly dependedon soil reaction, the organic acid contents, and the amount of fly ash used in treatment.

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Sequential Extraction을 이용한 Fly ash의 Cd 흡착 양상 평가

  • 이광헌;이승학;이아라;명동일;박준범;김형석
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.376-379
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    • 2004
  • pH has been regarded as a master variable governing the heavy metal sorption on fly ash. However, the chemical constituents in the fly ash could also suggest a potential sorption site for heavy metals. So, in this study sequential extraction method is employed to evaluate the sorption behavior of fly ash for cadmium. Two different fly ashes (S-fly ash, T-fly ash) were obtained from different power plants in Korea. First, cadmium is adsorbed under four different initial pHs. And, Cd sorbed in fly ash was sequentially desorbed following the sequential extraction method suggested by Tessier. In test results, the effect of pH increase was differently exerted in two fly ash. In S-fly ash, exchangeable fraction was dominated in low initial pH, however, as increasing initial pH, the fraction bound to carbonate increased. In the T-fly ash, regardless of initial pH the fraction bound to carbonate was major part of sorption estimated. The fraction bound to Fe/Mn oxide was about 10% in T-fly ash, and 5% in S-fly ash at high pH.

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Geotechnical Properties of Clay-Fly Ash Mixtures (점토-플라이 애시 혼합물의 지반공학적 특성)

  • Kwon , Moo-Nam;Chung , Sung-Wook;Lee, Sang-Ho;Goo , Jung-Min;Kim , Hyun-Ki
    • Journal of The Korean Society of Agricultural Engineers
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    • v.46 no.5
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    • pp.99-106
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    • 2004
  • Although fly ash has possesses viable engineering properties, an overwhelming majority of fly ash from coal combustion is still placed in storage or disposal sites. This study was undertaken to investigate the physical and mechanical properties of clay-fly ash mixture and to furnish engineering data when fly ash utilized as engineering materials. This paper includes geotechnical properties of fly ash, clay-fly ash mixtures and results of compaction test, unconfined strength test, direct shear test, leaching test and stability analysis of clay-fly ash bank slope. If proper amount of fly ash was put in clay, the clay-fly ash mixture has an increase of unconfined strength and stability of bank slope.

The Analysis of Slope Stability on Clay-Fly Ash Mixtures Embankment (점토-Fly Ash 혼합물로 된 제체의 사면안정 해석(지반공학))

  • 권무남;정성욱;김현기
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • pp.477-483
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    • 2000
  • Fly ash is the unburned residue resulting from the combustion of coal in utility and industrial boilers such as thermal power plants. Annually about 5 million tons of fly ash is being produced in korea. Less than 25 percent of total volume of fly ash is currently being used effectively for some ways. In the future, the volume of fly ash discharge from thermal power stations will be increasing more and more, and the development of the utilization of high volume fly ash is required. Fly ash has a lower compacted density and specific gravity than coarse grained natural aggregates but equivalent strength properties indicating that the fly ash could be used as a structural fill materials. So, clay-fly ash mixtures can be used as a fill material in the construction of embankments. Laboratory tests have been carried out to determine the physical, chemical, and geotechnical characteristics of the clay and fly ash. The fly ash is mixed with the clay in different proportions and the geotechnical characteristics of the mixtures have been studied also. In this study describes the results of the experimental study. The implications of the use of clay and clay-fly ash mixtures on the stability of embankments are discussed.

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Experimental and SEM Analyses of Ground Fly Ash in Concrete

  • Brueggen, Beth;Kang, Thomas H.K.;Ramseyer, Chris
    • International Journal of Concrete Structures and Materials
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    • v.4 no.1
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    • pp.51-54
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    • 2010
  • Fly ash is used in concrete to improve the fresh and hardened properties of concrete, including workability, initial hydration temperature, ultimate strength and durability. A primary limitation on the use of large quantities of fly ash in blended cement concrete is its slow rate of strength gain. Prior studies investigated the effects of grinding fly ash and fly ash fineness on the performance of concrete containing fly ash. This study aims to discover the sources of those effects, to verify the compressive strength behavior of concrete made with raw and processed Class C fly ash, and to investigate the properties of fly ash particles at the microscopic level. Concrete cylinder test results indicate that grinding fly ash can significantly benefit the early age strength as well as the ultimate strength of concrete with ground fly ash. Therefore, it is demonstrated that grinding fly ash increases its reactivity. Scanning Electron Microscopy was then used to investigate the physical effects of the grinding process on the fly ash particles in order to identify the mechanism by which grinding leads to improved concrete properties.

Strength Improvement of Lime-treated Soil with Fly Ash and Rice Husk Ash (Lime - Fly Ash / Rice Husk Ash에 의한 해성퇴적토의 강도특성 개선)

  • 민덕기;황광모;이경준;김현도
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.55-62
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    • 2000
  • In this paper, a laboratory investigation was carried out to estimate the strength improvement of quicklime mixture with fly ash and rice husk ash for the effective use of surplus soils, and the shear strength with curing time was estimated at lime 10 percent with the change of fly ash and rice husk ash content. The effect of strength improvement has been established through the change of fly ash and rice husk ash content from the samples taken at Samsan region, Ulsan. The test results indicated that the presence of lime with fly ash and rice husk ash encouraged the stabilization efficiency of lime with fly ash and rice husk ash, and increased shear strength. Furthermore, it is necessary for inquiring into the relationship between the characteristics of strength and the chemical components.

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Fabrication of Concrete Containing Mechanochemically Surface Treated(MST) Fly Ash (Mechanochemical 표면처리한 Fly Ash 혼화 Concrete의 제조)

  • Lee, Hyung-Jik;Koo, Ja-Hun;Yoo, In-Sang;Song, Doo-Gyoo;Joung, Hae-Kyoung;Kwon, Hyouk-Byoung;Yoon, Sang-Ok;Lee, Hyung-Bock;Lee, Hong-Lim
    • Journal of the Korean Ceramic Society
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    • v.39 no.2
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    • pp.135-144
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    • 2002
  • Fabrication of high strength structural concrete was investigated by using a mechanochemically Surface Treated Fly Ash(MSTFA) induced by mechanochemical processing through ball-milling of (90 wt% As Recevied Fly Ash(ARFA) + 10wt% cement) mixture, which was compared to the specimen fabricated by using As Received Fly Ash(ARFA) in terms with compressive strength and microstructures. The compressive strength of concrete specimen fabricated by using MSTFA represented 10-20% and 2-7% higher value than that for the case of using ARFA and BPFA in each cases. Increased compressive strength as above mentioned is considered to be caused by mutually increased affinity generated between cement and fly ash during mechanochemical processing.

A Study on Physical Properties of Mortar Mixed with Fly-ash as Functions of Mill Types and Milling Times

  • Seo, Sung Kwan;Chu, Yong Sik;Shim, Kwang Bo;Jeong, Jae Hyun
    • Journal of the Korean Ceramic Society
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    • v.53 no.4
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    • pp.435-443
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    • 2016
  • Coal ash, a material generated from coal-fired power plants, can be classified as fly ash and bottom ash. The amount of domestic fly ash generation is almost 6.84 million tons per year, while the amount of bottom ash generation is 1.51 million tons. The fly ash is commonly used as a concrete admixture and a subsidiary raw material in cement fabrication process. And some amount of bottom ash is used as a material for embankment and block. However, the recyclable amount of the ash is limited since it could cause deterioration of physical properties. In Korea, the ashes are simply mixed and used as a replacement material for cement. In this study, an attempt was made to mechanically activate the ash by grinding process in order to increase recycling rates of the fly ash. Activated fly ash was prepared by controlling the mill types and the milling times and characteristics of the mortar containing the activated fly ash was analyzed. When the ash was ground by using a vibratory mill, physical properties of the mortar mixed with such fly ash were higher than the mortar mixed with fly ash ground by a planetary mill.

Influence of the Character of Fly Ash on the Fluidity of Fly Ash Cement Paste

  • Lee, Seung-Heun;Sakai, Etsuo
    • Journal of the Korean Ceramic Society
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    • v.47 no.5
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    • pp.426-429
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    • 2010
  • The Influence of the character of fly ash on the fluidity of cement paste with a polycarboxylic acid type superplasticizer was investigated in connection with the particle size distribution, unburned carbon content, specific surface area and shape of the fly ash. The fluidity of the fly ash cement paste with an added 20 vol% fly ash increases with an increasing roundness of the fly ash and it decreases with an increasing n-value of the fly ash cement. There is a linear correlation between the roundness/n-value and the fluidity of fly ash cement paste.