• Title/Summary/Keyword: fly ash

Search Result 2,009, Processing Time 0.192 seconds

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
    • /
    • v.8 no.5
    • /
    • pp.59-65
    • /
    • 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.

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
    • /
    • v.46 no.5
    • /
    • pp.99-106
    • /
    • 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.

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
    • /
    • v.10 no.2
    • /
    • pp.133-137
    • /
    • 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.

  • PDF

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
    • /
    • v.4 no.1
    • /
    • pp.51-54
    • /
    • 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.

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
    • /
    • /
    • pp.376-379
    • /
    • 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.

  • PDF

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
    • /
    • /
    • pp.477-483
    • /
    • 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.

  • PDF

A Fundamental Study on the Mix Design in High Volume Fly-Ash Concrete (플라이애시를 대량 사용한 콘크리트의 배합설계를 위한 기초적 연구)

  • 심재형;김재환;최희용;강석표;최세진;김무한
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • /
    • pp.641-646
    • /
    • 2001
  • Generally, when Fly-Ash was used as replacement material of cement in concrete, it might occur retardation of setting and hardening. So, it is unable to use a large amount of Fly-Ash as replacement for cement. However, if it is used as replacement material of fine aggregate in concrete, we can use a large amount of Fly-Ash and settle a problem of natural-aggregate exhaustion. Furthermore, engineering properties of High Volume Fly-Ash Concrete Is better than that of plain concrete But, the larger Fly-Ash is replaced, the more fluidity of High Volume Fly-Ash Concrete decrease, because porous organization of Fly-Ash adsorb water and Superplasticizer. In this study, after appending additional water to High Volume Fly-Ash Concrete in proportion to weight of Fly-Ash, we intend to find proper ratio which doesn't affect strength and satisfy fluidity As a result of this study, it was found that fluidity of mortar with 25~28 percentage of additional water was satisfied with fluidity of plain mortar, and compressive strength of that was similar to plain mortar's

  • PDF

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
    • /
    • v.47 no.5
    • /
    • pp.426-429
    • /
    • 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.

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
    • /
    • /
    • pp.91-96
    • /
    • 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)

  • PDF

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
    • /
    • v.11 no.6
    • /
    • pp.25-33
    • /
    • 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.