• Title, Summary, Keyword: fly ash

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Effect of fineness of high lime fly ash on pozzolanic reactivity and ASR mitigation

  • Afshinnia, Kaveh;Rangaraju, Prasada R.
    • Computers and Concrete
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    • v.20 no.2
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    • pp.197-204
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    • 2017
  • Typically, high lime fly ash (Class C) has been characterized as a fly ash, which at lower replacement levels is not as effective as the low lime (Class F) fly ash, in mitigating alkali-silica reaction (ASR) in portland cement concrete. The influence of fineness of Class C, obtained by grinding virgin fly ash into finer particles, on its pozzolanic reactivity and ASR mitigation performance was investigated in this study. In order to assess the pozzolanic reactivity of mortar mixtures containing virgin or ground fly ashes, the strength activity index (SAI) test and thermo-gravimetric analysis (TGA) were conducted on the mortar cubes and paste samples, respectively, containing virgin fly ash or two ground fly ashes. In addition, to evaluate any improvement in the ASR mitigation of ground fly ashes compared to that of the virgin fly ash, the accelerated mortar bar test (AMBT) was conducted on the mortar mixtures containing different dosages of either virgin or ground fly ashes. In all tests crushed glass aggregate was used as a highly reactive aggregate. Results from this study showed that the finest fly ash (i.e., with an average particle size of 3.1 microns) could increase the flow ability along with the pozzolanic reactivity of the mortar mixture. However, results from this study suggested that the fineness of high lime fly ash does not seem to have any significant effect on ASR mitigation.

Unburnt Carbon Combustion in the Production of Light Weight Sintered Fly ash (Fly ash 경량골재 생성 중 미연탄소의 연소 현상 규명)

  • 주윤정;오명숙
    • Proceedings of the Korea Society for Energy Engineering kosee Conference
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    • pp.91-96
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    • 2002
  • 본 연구는 화력발전소에서 발생하는 fly ash의 재활용 분야중 하나인 fly ash 경량골재 생산과정에서 소성(sintering)온도를 결정하는 미연탄소의 연소 현상을 분석함으로서 공정에 적용 가능한 단일 입자 연소 모델 개발을 목적으로 한다. fly ash 경량골재는 미연탄소를 포함한 fly ash를 점결제를 이용하여 성형하고, 함유된 미연탄소를 연소시켜, 그 연소열을 이용하여 fly ash를 소성 시켜 형성된다.(중략)

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Removal of Unburned-Carbon from Fly-Ash of Bituminous Coal by Froth Flotation (포말부유선광법에 의한 유연탄 비산회의 미연탄소분 제거연구)

  • Son, Sung-Geun;Kim, Jung-Duk;Park, Byung-Wook
    • Resources Recycling
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    • v.5 no.3
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    • pp.44-49
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    • 1996
  • One of the most serious problems in utilizing the fly-ash produced from damcstic coal-firing power plants is lhc unburned-carbon mntained m the fly-ash In this shldy, the effects of fruther and collector an the yield,recuvery,unburnedcarbon rejectiou peiccntage,and process efficiency of product (cleaned fly-ash) wcrc examined when convzntional froth flotation was applied to rejcct the unburned-carbon included in the fly-ash of bituminous coal Alsa,the ash analysis for both thc raw and the clcaned fly-ash was conducted to review the change in thc major elements of fly-ash. Experimental results shawcd lhat tlle rcjectlon oI the unburned-cubon of thc raw fly-ash sample is available upto 92.4% using fiath flotalian and that the putity ol the pmdud(c1eancd fly-ash) attains up to 99.4%.

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Utilization of Electrostatic Precipitator as Fly ash Classifier (Fly ash 분급기(分級機)로서 화력발전소(火力發電所) 전기집진기(電氣集塵機)의 활용(利用))

  • Lee, Seung-Heun
    • Resources Recycling
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    • v.19 no.2
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    • pp.3-9
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    • 2010
  • In most coal fired power plants, fly ashes collected from each of hoppers in the electrostatic precipitator are transported and stored in a silo. However the properties of the fly ashes collected from each of hoppers in electrostatic precipitator varies with the distance of the collection field from the boiler. The more distance hopper gets fly ash with larger specific surface area. Therefore, in electrostatic precipitator the hopper itself is expected to have the effect of classifying fly ashes. This study examines the physical, chemical and mineralogical properties of fly ash, collected from each of hoppers attached to an electrostatic precipitator in the coal fired power plant and looks into the possibility of the electrostatic precipitator being used as a classifier. Also, the study reviewed the possibility of acquiring high quality fly ash.

A Study on Development of Shotcrete Material using Fly Ash (Fly Ash을 이용한 Shotcrete 재료의 개발에 관한 연구)

  • 한오형;강추원
    • Explosives and Blasting
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    • v.21 no.2
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    • pp.21-30
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    • 2003
  • Currently, the shotcrete used as basic support in the tunnel excavation, has the advantages of maintaining high-level strength in condition of early shooting with thin thickness based on the excavation characteristics of rock mass. Therefore supreme equipment and materials were developed and the great strides have continued. Also, the development of measurement technology and the rocks behaviors of undergound are evaluated in detail and the designs of strength and thickness are made. The reinforcement materials development of new material is carried on. Most of the coal fly ash produced in Korea fire power plant is fly ash and bottom mash. Fly ash has been producing to be applied in many fields such as cement, aggregate, construction, civil, agriculture and fisheries. Also a lot of experiments are actively on the way. Therefore in this experiment, in order to use the fly ash mixed with concrete as a material of shotcrete, the experiment was performed in the best content to reduce the compression strength and the shooting rebound ratio of the excavated surface to use fly ash as a substitute material of concrete. As a result, when 15%.wt substitution was made to the fly ash, about 10% of compression strength and 6% of rebound ratio was reduced.

Nitrogen Oxides Adsorbing Capacity of High Carbon Fly Ash Containing Cementitious Materials (탄소함량이 높은 플라이애쉬를 함유한 시멘트 페이스트의 질소산화물 흡착 성능)

  • Lee, Bo Yeon
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.34 no.3
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    • pp.37-42
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    • 2018
  • The use of fly ash in construction materials is increasing worldwide due the various advantages of using it, such as to produce durable concrete, or to use less cement and thus lower carbon dioxide emissions. The quality of fly ash is often determined by loss on ignition value (LOI), where an upper limit of LOI is set in each country for quality control purpose. However, due to many reasons, production of high LOI fly ash is increasing that cannot be utilized in concrete, ending up in landfill. In this study, the effect of fly ash use in cementitious materials on nitrogen oxides adsorption is examined. In particular, the effect of using high LOI, and thus high carbon content fly ash on nitrogen oxides adsorption is investigated. The results suggest that the higher carbon content fly ash is related to higher nitrogen dioxide adsorption, although normal fly ash was also more effective in nitrogen dioxide adsorption than ordinary portland cement. Also, higher replacement rate of up to 40% of fly ash is beneficial for nitrogen dioxide adsorption. These results demonstrate that high carbon fly ash can be used as construction materials in an environmentally friendly way where strength requirement is low and where nitrogen oxides emissions are high.

Prediction of Maximum Fly Ash Conveying Capacity of Fly Ash System in a Power Plant (발전 보일러용 비회 이송설비에서 최대 비회 이송량 예측)

  • Jin, Kyung-Yong;Moon, Yoon-Jae;Lee, Jae-Heon;Moon, Seung-Jae
    • Plant Journal
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    • v.11 no.1
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    • pp.50-57
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    • 2015
  • This study presents prediction of maximum fly ash conveying capacity of fly ash system in a power plant. The mixture ratio and pressure drop characteristics of air-fly ash flow in piping system are not well understood due to the complexity of particle motion mechanism. In this paper, the researcher investigated the optimum mixture ratio when the pressure drop of fly ash conveying system is equal to maximum static pressure of displacement fly ash transport blower and the capacity of fly ash transport according to the optimum mixture ratio by experimenting the fly ash conveying system of domestic D coal thermal power plants, which is currently in operation. The experiment results showed that the maximum fly ash conveying capacity of fly ash system were founded under the condition of maximum air volume 5,040 m3/h, static pressure of trip condition 1,163 mmH2O. In addition, it was predicted maximum mixture ratio of the air-fly ash was 8.66 and maximum capacity of fly ash conveying was 52,600 kg/h under these conditions.

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Influence of Fly Ash Content with Respect to the Fresh and Mechanical Properties in Concrete (플라이애쉬 함유량이 콘크리트의 굳기전 성질 및 역학적 특성에 미치는 영향)

  • 이진용;최수홍;강석화;이광명
    • Journal of the Korea Concrete Institute
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    • v.11 no.6
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    • pp.25-33
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    • 1999
  • The role of fly ash in concrete become impotant with finding the charateristics of fly ash in which it is used as cement replacement material. An experimental study is carried out to investigate the characteristics of concrete containing fly ash. The loss of slump and air content of fly ash concrete tested up to 120 minutes are lower than those of ordinary concrete, but the setting time and bleeding are increased with increasing fly ash content. The compressive and tensile strength of fly ash concrete are slightly lower than those of ordinary concrete between 7 and 28 days, however, the long-term (at 180 days) compressive strength of fly ash concrete is significantly higher. In addition, fly ash reduces the heat of hydration and peak of temperature rise in concrete.

Prediction of fly ash concrete compressive strengths using soft computing techniques

  • Ramachandra, Rajeshwari;Mandal, Sukomal
    • Computers and Concrete
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    • v.25 no.1
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    • pp.83-94
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    • 2020
  • The use of fly ash in modern-day concrete technology aiming sustainable constructions is on rapid rise. Fly ash, a spinoff from coal calcined thermal power plants with pozzolanic properties is used for cement replacement in concrete. Fly ash concrete is cost effective, which modifies and improves the fresh and hardened properties of concrete and additionally addresses the disposal and storage issues of fly ash. Soft computing techniques have gained attention in the civil engineering field which addresses the drawbacks of classical experimental and computational methods of determining the concrete compressive strength with varying percentages of fly ash. In this study, models based on soft computing techniques employed for the prediction of the compressive strengths of fly ash concrete are collected from literature. They are classified in a categorical way of concrete strengths such as control concrete, high strength concrete, high performance concrete, self-compacting concrete, and other concretes pertaining to the soft computing techniques usage. The performance of models in terms of statistical measures such as mean square error, root mean square error, coefficient of correlation, etc. has shown that soft computing techniques have potential applications for predicting the fly ash concrete compressive strengths.

Assessment of potential environmental impact from fly ash landfill (국내 석탄회 육상매립의 오염 잠재성 평가)

  • Lee, Sang Hoon
    • Journal of Environmental Impact Assessment
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    • v.8 no.4
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    • pp.25-35
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    • 1999
  • Fly ash, by-product from coal fired power station, has long been regarded as a potential contamination source for heavy metals and inorganics due to their enriched concentrations and associations with particle surface. Feed coal and fly ash samples were collected from two power stations; Yongdong deliang with domestic anthracite coals and Boryong with imported bituminous coals. The coal and fly ash samples were analyzed for chemical composition and mineral components, using XRF and XRD. Batch leaching experiments were conducted by agitating samples with deionised water for 24 hours. Anthracite coals are generally higher in Al and Si contents than bituminous coals. This is due to the higher ash contents of the anthracite coal than bituminous coal. The chemistry of the two fly ash samples shows broadly similar compositions each other, except for the characteristically high contents of Cr in anthracite coal fly ash. Leaching experiments revealed that concentrations of metals gradually decreased with leachings in general. However, measurable amounts of metals were present in the effluent from weathered ash and the samples subjected to the leaching procedure. These metals are likely to indicate that the metals in fly ash were incorporated into glass fraction as well as associated with particle surface of samples. Dissolution of aluminosilicate glass would control releasing heavy metals from fly ash as weathering progresses during landfill with implication of possible groundwater contamination through fly ash landfill.

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