Fly Ashes Used For Blended Portland Cement: Effect Of Grinding on Cement Quality

1988 ◽  
Vol 136 ◽  
Author(s):  
Erik Stoltenberg-Hansson
Keyword(s):  
Particle Size ◽  
Fly Ash ◽  
Specific Gravity ◽  
Portland Cement ◽  
Large Scale ◽  
Void Content ◽  
Strength Increase ◽  
Fly Ashes ◽  
Laser Method ◽  
Air Void

ABSTRACTTests have been performed with Class F fly ashes used for the production of interground 20% fly ash cement. Unground and ground fly ashes were mixed with a reference high fineness Portland cement and tested for strength in mortar (ISO/CEN method). The fly ashes were also tested for chemical composition, bulk density and specific gravity, fineness (Blaine) and particle size distribution (laser method). There are considerable variations in the specific weights of the asdelivered fly ashes. It is shown that even a small amount of grinding increases the specific gravity significantly, and improves and homogenizes the particle size distributions, resulting in higher strength. The strength increase corresponds to the decrease in air void content.Intergrinding of fly ash and clinker in large scale mills reduces the power consumption, giving the same 28-day strength as mixed fly ash cement with higher fineness.

Low Cement/High Fly Ash Concretes: Their Properties and Response to Chemical Admixtures

1987 ◽  
Vol 113 ◽  
Author(s):  
V. H. Dodson
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Calcium Hydroxide ◽  
Pozzolanic Reaction ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Fly Ashes ◽  
Chemical Admixtures ◽  
Reaction With Water

ABSTRACTIn practice, the amount of fly ash added to portland cement concrete varies depending upon the desired end properties of the concrete. Generally, when a given portland cement concrete is redesigned to include fly ash, between 10 and 50% of the cement is replaced by a volume of fly ash equal to that of the cement. Sometimes as much as twice the volume of the cement replaced, although 45.4 kg (100 lbs) of cement will only produce enough calcium hydroxide during its reaction with water to react with about 9 kg (20 lbs) of a typical fly ash. The combination of large amounts of certain fly ashes with small amounts of portland cement in concrete has been found to produce surprisingly high compressive strengths, which cannot be accounted for by the conventional “pozzolanic reaction”. Ratios of cement to fly ash as high as 1:15 by weight can produce compressive strengths of 20.7 MPa (3,000 psi) at I day and over 41.4 MPa (6,000 psi) at 28 days. Methods of identifying these “hyperactive” fly ashes along with some of the startling results, with and without chemical admixtures are described.

Jet mill grinding of portland cement, limestone, and fly ash: Impact on particle size, hydration rate, and strength

2013 ◽  
Vol 44 ◽  
pp. 41-49 ◽  
Author(s):  
Hongfang Sun ◽  
Brian Hohl ◽  
Yizheng Cao ◽  
Carol Handwerker ◽  
Todd S. Rushing ◽  
...  
Keyword(s):  
Particle Size ◽  
Fly Ash ◽  
Portland Cement ◽  
Hydration Rate

scholarly journals Modified Fly Ash-Based Adsorbents (MFA) for Mercury and Carbon Dioxide Removal from Coal-Fired Flue Gases

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7101
Author(s):  
Marta Marczak-Grzesik ◽  
Piotr Piersa ◽  
Mateusz Karczewski ◽  
Szymon Szufa ◽  
Hilal Ünyay ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Particle Size ◽  
Fly Ash ◽  
Chemical Composition ◽  
Solid Waste ◽  
Flue Gas ◽  
Flue Gases ◽  
Co2 Removal ◽  
Fly Ashes ◽  
Modified Fly Ash

One of the solid waste produced during the combustion of coal are fly ashes. Disposal challenges and environmental consequences are the results of significant process yield and atmospheric emission of fly ashes. The exact chemical composition of FA depends mainly on the type of utilised fuel and combustion conditions. It consists mainly of chemically stable metal oxides, such as Al2O3, Fe2O3, SiO2, CaO, MgO, K2O, Na2O and TiO2, but its toxicity is related to the possible presence of some trace elements, such as As, Hg, Cd, Se and Cr. The chemical and physical properties of fly ash (e.g., particle size distribution, porosity, and surface area) make it suitable as an adsorbent to remove various impurities from process flows such as flue gas stream. Its suitability for capturing mercury from flue gas was experimentally confirmed due to its abundant supply, particle size, bulk density, porosity, chemical composition and low cost. Hence, the use of fly ash as adsorbents and precursors for the production of heavy metal adsorbents is of great practical importance, as it reduces the cost of mercury capture and alleviates the problems associated with the disposal of solid waste. Studies showed that the chemical components present in fly ash additives could stimulate catalytic oxidative capacity, which increases the adsorption of Hg0 oxidation and adsorption of both Hg and CO2. The presented study analysed fly ashes from different zones of the electrostatic precipitator and verified their suitability for removing impurities from flue gases, i.e., mercury and carbon dioxide. The results outlined modified fly ash as having good Hg and CO2 removal capabilities. The adsorption efficiency of Hg reached 92% for Hg and 66% for CO2, while untreated fly ash reached 67% for Hg and 59% for CO2.

scholarly journals REVIEW ON WASTE MATERIAL USAGE IN CEMENT CONCRETE MIX

YMER Digital ◽  
2021 ◽  
Vol 20 (12) ◽  
pp. 694-709
Author(s):  
S Mahaboob Subhani ◽  
◽  
P Dinesh Sankar Reddy ◽  
S .Altaf Hussain ◽  
◽  
...  
Keyword(s):  
Particle Size ◽  
Fly Ash ◽  
Portland Cement ◽  
Calcium Oxide ◽  
Plastic Waste ◽  
Waste Materials ◽  
Cement Concrete ◽  
Sustainable Technologies ◽  
Concrete Mix ◽  
Granite Rocks

Nature has blessed with natural resources like rocks / minerals, vegetation, air and water. These are about one crore eighty six lakhs living creatures existing in the world. Most of the living creatures are using their intellect and residing in the natures nest, where as human being is blessed with unique knowledge and wisdom which propelled to discover wheel, moving machineries and established good shelter with ultra architectural designs. Ancient man was living in huts further more constructed mud houses with the available clay / mud. Over a period of time man discovered calcium oxide to use in construction. In 1840s, a scientist by name William Aspdin has invented the manufacturing process of Portland cement production. Over a period of time, lot of advancements took place in producing different types of cement. During 1950’s fly ash was considered as a waste and used to land fill /dumps. Over a period of time man discovered compatible chemicals in fly ash and successful in mixing Ordinary Portland cement up to 30% which is called Pozzolana Portland cement. Several Researchers tried different waste materials to be used as a potential, concrete mix and have been successful in doing so. This paper deals in reviewing potential waste materials being used in cement concrete. Granite rocks are sliced to fine plates for the utility as flooring material. In the process of cutting and smothering the granite, fine dust of approximately 50µm is generated. Researchers discovered compatibility of granite saw dust in cement mix and were successful. Everyday hundreds and thousands of tones of plastic waste is generated. Researchers also tried to use plastic waste in civil construction and partially successful as plastic is organic in nature where as cement is inorganic in nature, nevertheless plastic waste is found as a potential mix in laying bitumen road. Limestone which consists of calcium atom and oxygen atom exists naturally in certain areas where as calcium oxide is also produced synthetically by cracking calcium carbonate at approximately 1000oC. Researchers have been successful in using calcium oxide, municipal waste in civil construction at different proportions. The optimal quality of final cement is governed by particle size and its distribution. Therefore adequate review is also done in terms of particle size, distribution and quality. The current objective of this review article is to give an insight about the sustainable technologies in cement using waste materials disposed in abundance.

Influence of Physical and Chemical Properties on the Activity of Fly Ashes

1987 ◽  
Vol 113 ◽  
Author(s):  
F. Sybertz
Keyword(s):  
Particle Size ◽  
Fly Ash ◽  
Hydrochloric Acid ◽  
Potassium Hydroxide ◽  
Chemical Properties ◽  
Experimental Program ◽  
Physical And Chemical Properties ◽  
Fly Ashes ◽  
Physical And Chemical ◽  
And Chemical Properties

ABSTRACTIn an experimental program, the suitability of various methods for testing the pozzolanic activity of fly ash was investigated. The research was conducted on virtually all fly ashes approved as concrete additives in Germany. This paper discusses differences in the particle size distribution and the solubility on dissolution with hydrochloric acid and potassium hydroxide of the fly ashes. It also reports on interrelationships between the physical and chemical properties of the fly ashes and the workability and strength of mortars containing fly ash.

Retardation Effects in the Hydration of Cement-Fly Ash Pastes

1984 ◽  
Vol 43 ◽  
Author(s):  
Michael W. Grutzeck ◽  
Wei Fajun ◽  
Della M. Roy
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Solid Phase ◽  
Heat Of Hydration ◽  
Type I ◽  
Fly Ashes ◽  
Solution Composition ◽  
Early Hydration ◽  
High Calcium ◽  
Phase Characterization

AbstractThe hydration of high-calcium and low-calcium fly ash-cementmixtures was investigated to determine the effect of fly ash upon the hydration of a Type I portland cement, and to determine the associated mechanisms of hydration. When blended with portland cement, both fly ashes retarded the early hydration process, the high-Ca more so than the low-Ca. Analyses of solution compositions and calorimetric (heat of hydration) measurements were made. The retardation and hydration effects are discussed in terms of solution composition data and solid phase characterization. The hydration effects were interpreted and compared with the results of previous work.

scholarly journals High Strength Geopolymers Produced from Coal Combustion Fly Ash

2013 ◽  
Vol 11 (2) ◽  
pp. 155-161
Keyword(s):  
Particle Size ◽  
Compressive Strength ◽  
Fly Ash ◽  
Coal Combustion ◽  
High Strength ◽  
Coarse Fraction ◽  
Strength Development ◽  
Fly Ashes ◽  
The Relationship ◽  
Geopolymer Material

High strength geopolymers were produced from coal combustion fly ashes. These matrices reached compressive strength values over 100 MPa, much stronger and denser than obtained by using Portland Cement binders. Size fractions were obtained by size separation techniques and the relationship between strength and particle size was investigated. The differences in compressive strength measured in the geopolymers made from fine fractions, the original fly ash and a coarse fraction of the same ash, were not significantly higher than the variation found for a reference geopolymer material. Therefore, a direct size-strength relationship could not be proven. Moreover, the chemistry and the pH of the fractions also varied, and this might as well has played a role in the strength development.

scholarly journals Lightweight masonry block without Portland cement

2021 ◽  
Vol 26 (5) ◽  
pp. 945-953
Author(s):  
Paki Turgut ◽  
Mehmet Can Alas ◽  
Muhammed Arif Gurel
Keyword(s):  
Thermal Conductivity ◽  
Fly Ash ◽  
Portland Cement ◽  
Chemical Properties ◽  
Waste Materials ◽  
Fly Ashes ◽  
Free Lime ◽  
The World ◽  
Belt Conveyors ◽  
Lightweight Masonry Block

ABSTRACT Huge amounts of fly ash - a substance that does not conform to the ASTM C618 classification due to its chemical properties - have been abandoned in landfills around the world, despite their self-cementing property. It has not been used in concrete making applications due to its large amounts of free lime and sulfate contents. The fly ash in these plants is dumped in landfills, causing serious environmental hazards. Fly ash is disposed to the landfills by belt conveyors after being humidified with water. Therefore, the fly ashes humidified in the landfill areas are hydrated in nature. This hydration is further intensified in landfills by rain and snow. Thus, the free lime content of fly ash decreases due to its long hydration process. In this work, the lightweight masonry blocks were produced by mixing normal and hydrated fly ashes or normal, hydrated fly ash and lime without Portland cement. The compressive strength, water absorption, sorptivity, density, porosity, and thermal conductivity values of the samples produced were determined. The results obtained from these tests showed that lightweight masonry blocks could be produced by using these waste materials in building applications.

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