Electrokinetic Phenomena and Surface Characteristics of Fly Ash Particles

1984 ◽  
Vol 43 ◽  
Author(s):  
R. I. A. Malek ◽  
D. M. Roy
Keyword(s):  
Fly Ash ◽  
Surface Characteristics ◽  
Ionic Species ◽  
Point Of Zero Charge ◽  
Fly Ashes ◽  
Electrokinetic Phenomena ◽  
Zeta Potentials ◽  
Low Calcium ◽  
High Calcium

AbstractThe zeta-potentials of two fly ashes were studied (high-calcium and low-calcium). It was found that they possess a point of charge reversal at pH = 10.5 to 12. The point of zero charge (low-calcium fly ash) was found to be at pH = 5. Furthermore, it shifted to more acidic values after the fly ash is aged in several calcium-containing solutions. The surficial changes that could happen when mixing fly ashes with cement and concrete were further evaluated by aging fly ashes in different solutions: Ca(OH)2, CaSO4·2H2O, NaOH and water solutions. Information from analyses for different ionic species in the solutions and characterization of the solid residues (XRD and SEM) was used in tentative explanations for the different behavior of the two types of fly ash in cementitious mixtures and concrete.

X-Ray Powder Diffraction For Studying the Mineralogy of fly ash

1987 ◽  
Vol 113 ◽  
Author(s):  
Gregory I. McCarthy
Keyword(s):  
Fly Ash ◽  
Powder Diffraction ◽  
Reference Materials ◽  
Standard Reference Materials ◽  
National Bureau ◽  
Fly Ashes ◽  
X Ray ◽  
High Calcium

ABSTRACTA brief summary of the use of x-ray powder diffraction for studying the mineralogy of fly ash is presented. Mineralogies of low-, intermediate- and high-calcium fly ashes are discussed and illustrated by results from XRD characterization of U.S. National Bureau of Standards fly ash Standard Reference Materials.

scholarly journals An Appraisal of Compressive Strength of Concrete Incorporated with Chemically Different Fly Ashes

2020 ◽  
Vol 14 (1) ◽  
pp. 188-199
Author(s):  
Atsushi Suzuki ◽  
Dinil Pushpalal ◽  
Hiroo Kashima
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Physical Properties ◽  
Calcium Content ◽  
Fly Ashes ◽  
Fly Ash Concrete ◽  
Low Calcium ◽  
High Calcium ◽  
Applicable Range ◽  
Compressive Strength Of Concrete

Introduction: Generally, the compressive strength of fly ash concrete differs depending on the properties of fly ash. This strength difference causes difficulties for concrete engineers to guarantee the strength of supplied concrete. Methods: This research firstly carried out the compressive strength tests on the concrete incorporated with fly ash possessing various chemical composition, which are high and low calcium fly ashes. The linear and nonlinear regression analyses were adopted to build the strength prediction model. Results: The chemical and physical properties of procured fly ash with high and low calcium contents have been quantified. Specifically, the compressive strength of concrete with high calcium fly ash demonstrates a strong correlation with calcium content, rather than physical properties such as the surface area and loss of ignition. Therefore, the compressive strength on 28th day can be assessed by a simple formula, taking CaO content of fly ash as an independent variable. In further, the strength on an arbitrary day can be predicted based on the 28th day strength and the replacement rate of fly ash. Conclusion: The two-step framework proposed in this research enables concrete engineers to evaluate the compressive strength of fly ash concrete with an error rate of less than 30%, within the applicable range addressed in this research.

scholarly journals Characterization of the Physical, Chemical, and Adsorption Properties of Coal-Fly-Ash–Hydroxyapatite Composites

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 774
Author(s):  
Eleonora Sočo ◽  
Dorota Papciak ◽  
Magdalena M. Michel ◽  
Dariusz Pająk ◽  
Andżelika Domoń ◽  
...  
Keyword(s):  
Fly Ash ◽  
Coal Fly Ash ◽  
Thermal Power ◽  
Synthesis Conditions ◽  
High Calcium ◽  
Ft Ir ◽  
Ir Analysis ◽  
Wet Synthesis

(1) Hydroxyapatite (Hap), which can be obtained by several methods, is known to be a good adsorbent. Coal fly ash (CFA) is a commonly reused byproduct also used in environmental applications as an adsorbent. We sought to answer the following question: Can CFA be included in the method of Hap wet synthesis to produce a composite capable of adsorbing both heavy metals and dyes? (2) High calcium lignite CFA from the thermal power plant in Bełchatów (Poland) was used as the base to prepare CFA–Hap composites. Four types designated CFA–Hap1–4 were synthesized via the wet method of in situ precipitation. The synthesis conditions differed in terms of the calcium reactants used, pH, and temperature. We also investigated the equilibrium adsorption of Cu(II) and rhodamine B (RB) on CFA–Hap1–4. The data were fitted using the Langmuir, Freundlich, and Redlich–Peterson models and validated using R2 and χ2/DoF. Surface changes in CFA–Hap2 following Cu(II) and RB adsorption were assessed using SEM, SE, and FT-IR analysis. (3) The obtained composites contained hydroxyapatite (Ca/P 1.67) and aluminosilicates. The mode of Cu(II) and RB adsorption could be explained by the Redlich–Peterson model. The CFA–Hap2 obtained using CFA, Ca(NO3)2, and (NH4)2HPO4 at RT and pH 11 exhibited the highest maximal adsorption capacity: 73.6 mg Cu/g and 87.0 mg RB/g. (4) The clear advantage of chemisorption over physisorption was indicated by the Cu(II)–CFA–Hap system. The RB molecules present in the form of uncharged lactone were favorably adsorbed even on strongly deprotonated CFA–Hap surfaces.

scholarly journals Durability of blended cement against sodium sulphate attack and alkali-silica reaction

2021 ◽  
Author(s):  
Giri Raj Adhikari
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Alkali Silica Reaction ◽  
Sulphate Attack ◽  
Ternary Blends ◽  
Replacement Level ◽  
Fly Ashes ◽  
Study Results ◽  
High Calcium ◽  
High Calcium Fly Ash

Blended cements were studied for their efficacy against sulphate attack and alkali-silica reaction using six different types of fly ashes, a slag, a silica fume and four types of General Use Portland cement of different alkalinity. The study results showed that low calcium fly ash, silica fume and ground granulated blast furnace slag enhanced the sulphate resistance of cement with increased efficacy with the increase in the replacement level. However, slag and silica fume, especially at low replacement levels, exhibited increased rate of expansion beyond the age of 78 weeks. On the contrary, high calcium fly ashes showed reduced resistance to sulphate attack with no clear trend between the replacement level and expansion. Ternary blends consisting of silica fume, particulary in the amount of 5%, high calcium fly ashes and General Use (GU) cement provided high sulphate resistance, which was attributable to reduced permeability. In the same way, some of ternary blends consisting of slag, high calcium fly ash and GU cement improved sulphate resistance. Pre-blending optimum amount of gypsum with high calcium fly ash enhanced the latter's resistance to sulphate attack by producing more ettringite at the early stage of hydration. In the context of alkali-silica reaction permeability was found to be a contributing factor to the results of the accelerated mortar bar test. High-alkali, high-calcium fly ash was found to worsen the alkali silica reaction when used in concrete containing some reactive aggregates. Ternary blend of slag with high calcium fly ash was found to produce promising results in terms of counteracting alkali-silica reaction.

Characterization of pore solutions expressed from high-calcium fly-ash–water pastes

Fuel ◽  
2001 ◽  
Vol 80 (6) ◽  
pp. 815-819 ◽  
Author(s):  
J.K. Tishmack ◽  
J. Olek ◽  
S. Diamond ◽  
S. Sahu
Keyword(s):  
Fly Ash ◽  
High Calcium ◽  
High Calcium Fly Ash

Image Analysis of Fly Ash in the Characterization of the Shape of the Grains

1994 ◽  
Vol 370 ◽  
Author(s):  
M. Barrioulet ◽  
H. Cros ◽  
B. Husson ◽  
E. Ringot
Keyword(s):  
Image Analysis ◽  
Fly Ash ◽  
Mineralogical Composition ◽  
Fly Ashes ◽  
Particle Content ◽  
Power Stations ◽  
Fresh Material ◽  
Quantitative Image ◽  
Strength And Durability

AbstractFly ash from power stations is used as concrete additive to improve strength and durability. Surprisingly, studies of ashes of identical mineralogical composition from two different places have reported different results in terms of the rheological properties of the fresh material. The viscosity of the pastes made from these different fly ashes seems to be linked to the proportion of spherical and smooth-shaped grains found in them. A quantitative image analysis was carried out to characterize the shape of the grains of these two ashes from different geographical origins. The main result proves that the higher the glassy particle content of the fly ash, the more the hydraulic matrix is fluid.

Characterization of Fly Ash Reactivity by Isothermal Conduction Calorimetry

1987 ◽  
Vol 113 ◽  
Author(s):  
David J. Cook ◽  
H. Trinh Cao ◽  
Daksh Baweja
Keyword(s):  
United Kingdom ◽  
Fly Ash ◽  
Performance Prediction ◽  
The United States ◽  
Fly Ashes ◽  
Structural Concrete ◽  
Codes Of Practice ◽  
The United Kingdom ◽  
Direct Reflection

SUMMARYThe reactivity of fly ash is generally difficult to determine because neither a single physical nor chemical property nor any combination of these can be used characterize a particular sample completely. A direct reflection of this is the range of pozzolanicity tests proposed by standards worldwide and the applicability and relevance of such tests is currently being debated.In many countries, codes of practice and standards relating to fly ashes are currently under review. Some work has been carried out in countries including Australia, United Kingdom, and the United States on commercial fly ashes with a view to possible classification and implementation into standards [1-2]. It is generally recognized that current standards on fly ash do have some inadequacies with regard to performance prediction when included in concrete. Fineness requirements for fly ash for use in structural concrete (BS3892: Part 1) in the United Kingdom are currently being debated [2] with many workers suggesting that it would be possible to produce durable concrete with ashes which would not comply with the requirements of the standard [3].

Characterization of North American Lignite Fly Ashes II. XRD Mineralogy

1987 ◽  
Vol 113 ◽  
Author(s):  
G. J. McCarthy ◽  
D. M. Johansen ◽  
A. Thedchanamoorthy ◽  
S. J. Steinwand ◽  
K. D. Swanson
Keyword(s):  
Fly Ash ◽  
Bituminous Coal ◽  
Coal Fly Ash ◽  
Fly Ashes ◽  
X Ray ◽  
Mining Areas ◽  
Lignite Fly Ash ◽  
Coal Fly Ashes ◽  
Ferrite Spinel

ABSTRACTX-ray powder diffraction has been used to determine the crystalline phase mineralogy in samples of fly ash from each of the lignite mining areas of North America. The characteristic phases of North Dakota lignite fly ashes were periclase, lime, merwinite and the sulfate phases anhydrite, thenardite and a sodalite-structure phase. Mullite was absent in these low-Al2O3 ashes. Montana lignite ash mineralogy had characteristics of ND lignite and MT subbituminous coal fly ashes; mullite and C3A were present and the alkali sulfates were absent. Texas and Louisiana lignite fly ashes had the characteristic mineralogy of bituminous coal fly ash: quartz, mullite, ferrite-spinel (magnetite) and minor hematite. Even though their analytical CaO contents were 7–14%, all but one lacked crystalline CaO-containing phases. Lignite fly ashes from Saskatchewan were generally the least crystalline of those studied and had a mineralogy consisting of quartz, mullite, ferrite spinel and periclase. Quantitative XRD data were obtained. The position of the diffuse scattering maximum in the x-ray diffractograms was indicative of the glass composition of the lignite fly ash.

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