scholarly journals Synthesis and sintering of high-temperature composites based on mechanically activated fly ash

2012 ◽  
Vol 44 (2) ◽  
pp. 135-146 ◽  
Author(s):  
A. Terzic ◽  
Lj. Pavlovic ◽  
N. Obradovic ◽  
V. Pavlovic ◽  
J. Stojanovic ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Fly Ash ◽  
Mechanical Activation ◽  
Power Plants ◽  
Sem Analysis ◽  
Fly Ashes ◽  
Physico Chemical ◽  
Fly Ash Utilization ◽  
And Behavior

Amount of fly ash which is and yet to be generated in the coming years highlights the necessity of developing new methods of the recycling where this waste can be reused in significant quantity. A new possibility for fly ash utilization is in high-temperature application (thermal insulators or/and refractory material products). As such, fly ash has to adequately answer the mechanical and thermal stability criteria. One of the ways of achieving it is by applying mechanical activation procedure on fly ash. In present study, fly ashes from two different power plants were mechanically activated in a planetary ball mill. Mechanically treated fly ashes were cemented with two different binders: standard Portland cement and high-aluminates cement. Physico-chemical analysis and investigation of mineralogical components of composites are emphasized, due to the changes occurred in fly ash during mechanical activation and sintering of composites. Macro-performance of the composites was correlated to the microstructure of fly ash studied by means of XRD and SEM analysis. Thermal stability of crystalline phases was investigated with DTA. Highlight was placed on determination of relationship between mechanically activated fly ash and obtained composites microstructure on one side and behavior of sintered composites on the other side.

scholarly journals Leaching of the potentially toxic pollutants from composites based on waste raw material

2012 ◽  
Vol 18 (3) ◽  
pp. 373-383 ◽  
Author(s):  
Anja Terzic ◽  
Zagorka Radojevic ◽  
Ljiljana Milicic ◽  
Ljubica Pavlovic ◽  
Zagorka Acimovic
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Microstructural Analysis ◽  
Construction Materials ◽  
Significant Risk ◽  
Raw Material ◽  
Fly Ashes ◽  
X Ray ◽  
Toxic Pollutants ◽  
Physico Chemical

The disposal of the fly ash generated in coal based power-plants may pose a significant risk to the environment due to the possible leaching of hazardous pollutants, such as toxic metals. Also, there is a risk of leaching even when fly ash is built-in the construction composites. Fly ashes from various landfills were applied in several composite samples (mortar, concrete and brick) without any physical or thermal pre-treatment. The leachability of the potentially toxic pollutants from the fly ash based products was investigated. The leaching behavior and potential environmental impact of the 11 potentially hazardous elements was tracked: Pb, Cd, Zn, Cu, Ni, Cr, Hg, As, Ba, Sb and Se. A detailed study of physico-chemical characteristics of the fly ash, with accent on trace elements and the chemical composition investigation is included. Physico/chemical properties of fly ash were investigated by means of X-ray fluorescence, differential thermal analysis and X-ray diffraction methods. Scanning electron microscope was used in microstructural analysis. The results show that most of the elements are more easily leachable from the fly ash in comparison with the fly ash based composites. The leaching of investigated pollutants is within allowed range thus investigated fly ashes can be reused in construction materials production.

scholarly journals DETERMINING THE ROLE OF INDIVIDUAL FLY ASH PARTICLES IN INFLUENCING THE VARIATION IN THE OVERALL PHYSICAL, MORPHOLOGICAL, AND CHEMICAL PROPERTIES OF FLY ASH

2016 ◽  
Vol 56 (4) ◽  
pp. 265-282 ◽  
Author(s):  
Usman Haider ◽  
Zdenek Bittnar ◽  
Lubomír Kopecky ◽  
Vít Šmilauer ◽  
Jaroslav Pokorny ◽  
...  
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Thermal Power ◽  
Chemical Properties ◽  
Cementitious Materials ◽  
Individual Particle ◽  
Particle Analysis ◽  
Fly Ashes ◽  
Alumino Silicate ◽  
Individual Particles

The properties of fly ashes vary because of the differences in the properties of their individual particles, and the determination of variation in these properties is of interest to the industries which use pulverized raw fly ash in applications, such as in cementitious materials and in the recovery of certain rare elements from raw fly ash. To investigate the differences in individual particles, four pulverized raw fly ashes from thermal power plants of the Czech Republic were used in this research. It was observed from FE-SEM that all four fly ashes consist of glassy hollow spherical, solid spherical, porous spherical, bright spherical, porous slaggy and compact slaggy particles. Box and whisker diagrams were plotted from the data of EDX individual particle analyses, which showed that the data of percentages for the Si, Al, and Fe elements is more scattered as compared to other elements. It was further observed from ternary phase diagrams and pseudo coloured images, that nature of fly ash particles changes from alumino silicate glassy to alumino silicate calcite metallic to pure ferro-metallic,where glassy particles showed high percentages and pure calcite particles were absent in fly ashes. Furthermore, a comparison between the XRF, the EDX total area analyses, showed that the EDX individual particle analysis gives more realistic and reliable data with median, mean, and the standard deviation for percentages of each element present in the fly ashes.

Transmitted and Reflected Visible Light Microscopy of Two Bituminous Fly Ashes

1984 ◽  
Vol 43 ◽  
Author(s):  
Donald L. Biggs ◽  
Joseph J. Bruns
Keyword(s):  
Fly Ash ◽  
Light Microscopy ◽  
Silicate Glass ◽  
Power Plants ◽  
Magnetic Fraction ◽  
Fly Ashes ◽  
Complete Replacement ◽  
Replacement Product ◽  
Nonmagnetic Particles ◽  
Ferrite Spinel

AbstractFly ashes of high magnetic content taken from two midwestern power plants were examined to determine the mineralogy of the magnetic and nonmagnetic fractions. Fly ash spheres from the magnetic fraction are predominantly composed of ferrite spinel, hematite and silicate glass. The hematite appears to be a replacement product of the original ferrite spinel. Nonmagnetic phases include mullite, lime, small amounts of hematite and silicate glass. Quartz morphology indicates that it did not fuse in the furnace. Mullite and lime have morphologies indicative of crystallization in the furnace. Hematite is bonded to the nonmagnetic particles or as a complete replacement of ferrite spinel spheres.

The Suitability of Fly Ash for Use in Concrete According to EN 450 Based on their Particle Size

2018 ◽  
Vol 276 ◽  
pp. 110-115
Author(s):  
Martin Ťažký ◽  
Martin Labaj ◽  
Rudolf Hela
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Catalytic Reduction ◽  
Raw Materials ◽  
Thermal Power ◽  
Combustion Process ◽  
Thermal Power Plants ◽  
Mechanical Parameters ◽  
Fly Ashes ◽  
The Impact

The by-products of energy industry are nowadays often affected by new limits governing the production of harmful gases discharged into the air. These stricter and stricter criteria are often met by electricity producers by changing the combustion process in thermal power plants itself. Nowadays, the SNCR (selective non-catalytic reduction) application is quite common in the combustion process in order to help reduce the nitrogen oxide emission. This article deals with the primary measures of thermal power plants, which in particular consist of a modified treatment of raw materials (coal) entering the combustion process. These primary measures then often cause the formation of fly ash with unsuitable fineness for the use in concrete according to EN 450. The paper presents the comparison of the physico-mechanical parameters of several fly ashes with a different fineness values. The primary task is to assess the impact of non-suitable granulometry in terms of EN 450 on the other physico-mechanical parameters of fly ashes sampled within the same thermal power plant. Several fly ashes produced in the Czech Republic and surrounding countries were evaluated in this way.

Relationship Between Pozzolanic Activity and Chemical and Physical Characteristics of Selected Canadian Fly Ashes

1985 ◽  
Vol 65 ◽  
Author(s):  
R. C. Joshi ◽  
V. M. Malhotra
Keyword(s):  
Fly Ash ◽  
National Standard ◽  
Fly Ashes ◽  
Bureau Of Reclamation ◽  
Supplementary Cementing Materials ◽  
University Of Calgary ◽  
Fly Ash Utilization ◽  
The University ◽  
Pozzolanic Properties ◽  
The U.S

Raymond E. Davis and his associates appear to have coined the term “fly ash” in 1937. Following the pioneering studies by the U.S. Bureau of Reclamation for the Hungry Horse Dam, the use of fly ash for massive hydroelectric structures increased rapidly in the U.S., with ASTM issuing the first standard in 1954. In 1982, Canada issued a National Standard, CAN 3-A23.5-M82, entitled “Supplementary Cementing Materials and Their Use in Concrete Construction.” Because of the increasing interest in fly ash utilization, Canada Centre for Mineral and Energy Technology (CANMET) initiated research in the area of supplementary cementing materials in the early 1970's and has since published several comprehensive reports on the subject [1,2]. At the University of Calgary, we are studying Canadian fly ashes and their use in concrete, through an investigation of the physical, chemical, mineralogical and pozzolanic properties of fly ashes from fourteen sources across the country. We report here preliminary results from this study.

scholarly journals Separation of Cenospheres from Fly Ashes by Floatation Method

2010 ◽  
Vol 13 (1-2) ◽  
pp. 89 ◽  
Author(s):  
L.M. Manоcha ◽  
K.A. Ram ◽  
S.M. Manocha
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Thermal Power ◽  
Ceramic Particle ◽  
Composition Analysis ◽  
High Concentration ◽  
Fly Ashes ◽  
Power Station ◽  
Different Types ◽  
Chemical Composition Analysis

Fly-ashes are non-combustible mineral residues which are produced from coal in thermal power plants. Four different types of fly ashes were collected from different power station in Gujarat. Characterization through SEM shows that fly ash contains cenosphere i.e. gas bubble containing ceramic particle independent of their bulk density. Floatation technique was used for the separation of cenosphere from fly ash. Two solvents with extremely different densities were used for the separation of cenospheres. All methods gave approximately yield of less than 1 % cenosphere in fly ash. Color of cenospheres varied from gray to almost white and the value of density range from 0.4 – 0.8 g/cc. Further, chemical composition analysis revealed that cenospheres do not contain any high concentration of hazardous elements.

scholarly journals Stabilization of Indian Fly Ashes with Soils, Cement, and Randomly Oriented Fibers

2012 ◽  
Vol 3 ◽  
pp. 1-8
Author(s):  
Shenbaga R. Kaniraj ◽  
V. Gayathri ◽  
V.G. Havanagi
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Thermal Power ◽  
Experimental Studies ◽  
Fly Ashes ◽  
Strength Criteria ◽  
Permeability Characteristics ◽  
Polyester Fibers ◽  
Soil Mixtures ◽  
Pavement Base

 Experimental studies were carried out on fly ashes from two Indian thermal power plants, namely Rajghat and Dadri, with the aim of improving the utilization of fly ash in geotechnical engineering applications. It was attempted to improve the engineering performance of fly ash by several means such as by mixing fly ash with soils, cement, and polyester fibers. The research program included the study of: a) physical properties, chemical composition and morphology of the fly ashes; b) compaction, strength, and permeability characteristics of the fly ashes and fly ash-soil mixtures; c) compaction and strength characteristics of fly ash-soil mixtures stabilized with fibers alone, with cement alone, and with both cement and fibers. Results showed that addition of fly ash to soils would result in lighter and stronger fills. Fiber inclusions increased the strength of fly ash-soil specimens significantly and altered their behaviour from brittle to ductile. Even small cement contents increased the strength of the fly ash-soil mixtures significantly. With higher cement contents of up to 18% it was possible to prepare fly ash-cement design mixes that satisfied the strength criteria for pavement base courses.

scholarly journals Influence of Activators on Mechanical Properties of Modified Fly Ash Based Geopolymer Mortars

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1033 ◽  
Author(s):  
Piotr Prochon ◽  
Zengfeng Zhao ◽  
Luc Courard ◽  
Tomasz Piotrowski ◽  
Frédéric Michel ◽  
...  
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Thermal Power ◽  
Biomass Combustion ◽  
Fly Ashes ◽  
Binding Properties ◽  
Alkali Activated ◽  
Modified Fly Ash ◽  
Scanning Electron ◽  
And Calorimetry

The aim of this work was to study the influence of the type of activator on the formulation of modified fly ash based geopolymer mortars. Geopolymer and alkali-activated materials (AAM) were made from fly ashes derived from coal and biomass combustion in thermal power plants. Basic activators (NaOH, CaO, and Na2SiO3) were mixed with fly ashes in order to develop binding properties other than those resulting from the use of Portland cement. The results showed that the mortars with 5 mol/dm3 of NaOH and 100 g of Na2SiO3 (N5-S22) gave a greater compressive strength than other mixes. The compressive strengths of analyzed fly ash mortars with activators N5-S22 and N5-C10 (5 mol/dm3 NaOH and 10% CaO) varied from 14.3 MPa to 5.9 MPa. The better properties of alkali-activated mortars with regular fly ash were influenced by a larger amount of amorphous silica and alumina phases. Scanning electron microscopy and calorimetry analysis provided a better understanding of the observed mechanisms.

scholarly journals Effect of mechanical activation of fly ash added to Moroccan Portland cement

2018 ◽  
Vol 149 ◽  
pp. 01074 ◽  
Author(s):  
H. Ez-zaki ◽  
A. Diouri ◽  
M. Maher ◽  
A. Aidi ◽  
T. Guedira
Keyword(s):  
Fly Ash ◽  
Mechanical Activation ◽  
Thermal Power ◽  
Cement Industry ◽  
Production Costs ◽  
Blended Cements ◽  
Power Stations ◽  
Physico Chemical ◽  
Thermal Power Stations ◽  
Alternative Solutions

Nowadays, the cement industry is the largest emitter of CO2. In 2015, cement production accounts for roughly 8% of global CO2 emissions. In order to reduce this impact, cement plants are working on alternative solutions, for instance, producing cement by adding additives like fly ash known for reducing the emissions of CO2 and minimizing production costs. The thermal power stations in Morocco produce more than 500 000 tons per year. For ecological and sustainable development reasons, it is desirable to recycle these quantities according to beneficial methods to their addition in the cement. This study aims to investigate the influence of grinding fly ash on the physico-chemical and mechanical properties of fly ash blended CPJ45 cement. The addition of the fly ash particles to the grinder leads respectively to the breakage of the particles and to reduce the agglomeration effect in the balls of cement grinder. Fly ash milling was found to improve particles fineness, and increase the silica and alumina content in the cement. Furthermore, milled fly ash blended cements show higher compressive strength compared to unmilled fly ash blended cements, due to improved fly ash reactivity through their mechanical activation.

Development of Structural Concrete with Fly Ash

2014 ◽  
Vol 1054 ◽  
pp. 143-147 ◽  
Author(s):  
Rudolf Hela ◽  
Martin Ťažký
Keyword(s):  
High Temperature ◽  
Fly Ash ◽  
Power Plants ◽  
Elasticity Modulus ◽  
Partial Replacement ◽  
Past Century ◽  
The Past ◽  
Temperature Combustion ◽  
Pozzolanic Properties ◽  
High Temperature Combustion

The paper describes problems of using fly ash in concrete. Using fly ash produced during high temperature combustion in power plants as addition for concrete has been known since the 60s of the past century. The Standard EN 206 Concrete - Specification, performance, production and conformity characterizes high temperature combustion fly ash as an addition of the type II, i.e. active addition with pozzolanic properties. Use of fly ash as an active addition also enables partial replacement of cement. The paper solves the extent of cement which can be replaced with fly ash in this manner. Influence of addition of fly ash on consistency of concrete, development of compressive strength and elasticity modulus at the age of 7, 28, 60 and 90 days of concrete are observed.

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