1.Use of fly ash in concrete

2. What is Fly ash???Fly ash is one of the residues generated incombustion , and comprises the fineparticles that rise with the flue gases.Ash which does not rise is termedbottom ash. In an industrial context, flyash usually refers to ash produced duringcombustion of coal. 3. f fly ash ring o C ap tu Fly ash is generally captured by Photomicrograph made with a Scanningelectrostatic precipitators or other Electron Microscope (SEM): Fly ashparticle filtration equipment before particles at 2,000x magnificationthe flue gases reach the chimneysof coal-fired power plants, andtogether with bottom ash removedfrom the bottom of the furnace isin this case jointly known as coal 4. f fly ashp on e nt oCom Depending upon the source and makeupof the coal being burned, thecomponents of fly ash varyconsiderably, but all fly ash includessubstantial amounts of silicon dioxide(SiO2) (both amorphous and crystalline)and calcium oxide (CaO), both beingendemic ingredients in many coal-bearing rock strata. 5. f fly ashlass es oC ASTM C618 classifies fly ash in twocategories. Class F fly ash and Class C fly ash. The chief difference between these classes isthe amount of calcium, silica, alumina, andiron content in the ash. The chemicalproperties of the fly ash are largely influencedby the chemical content of the coal burned(i.e., anthracite, bituminous, and lignite). 6. f fly ash lass es o C Not all fly ashes meet ASTM C618 requirements,although depending on the application, this may not benecessary. Ash used as a cement replacement mustmeet strict construction standards, but no standardenvironmental regulations have been established in theUnited States. 75% of the ash must have a fineness of45 m or less, and have a carbon content, measured bythe loss on ignition (LOI), of less than 4%. 7. ashseso f Fly U There is no U.S. governmental registration or labelling of fly ash utilization in the different sectors of the economy -industry, infrastructures and agriculture. Fly ash utilization survey data, acknowledged as incomplete, are published annually by the American Coal Ash Association. The ways of fly ash utilization include (approximately in order of decreasing importance): Concrete production, as a substitute material for Portland cement and sand Embankments and other structural fills (usually for road construction) 8. ashseso f Fly U Grout and Flowable fill production Waste stabilization and solidification Cement clinkers production - (as a substitute material for clay) Mine reclamation Stabilization of soft soils Road subbase construction As Aggregate substitute material (e.g. for brick production) Mineral filler in asphaltic concrete 9. Flyashrial ic m ateozz ol a na sP Owing to its pozzolanic properties, fly ash is used as areplacement for some of the Portland cement content of concrete. The use of fly ash as a pozzolanic ingredient was recognized asearly as 1914, although the earliest noteworthy study of its usewas in 1937. Before its use was lost to the Dark Ages, Roman structures suchas aqueducts or the Pantheon in Rome used volcanic ash (whichpossesses similar properties to fly ash) as pozzolan in theirconcrete. Use of fly ash as a partial replacement for Portland cement isgenerally limited to Class F fly ashes. 10. Flyashrial ic m ateozz ol a na sP It can replace up to 30% by mass of Portland cement, and can addto the concretes final strength and increase its chemicalresistance and durability. Recently concrete mix design for partial cement replacement withHigh Volume Fly Ash (50 % cement replacement) has beendeveloped. E.g. For Roller Compacted Concrete (RCC)[used in damconstruction] replacement values of 70% have been achieved withprocessed fly ash at the Ghatghar Dam project inMaharashtra,India. 11. Flyashrial ic m ateozz ol a na sP Due to the spherical shape of fly ash particles, it can also increaseworkability of cement while reducing water demand. Since the worldwide production of Portland cement is expectedto reach nearly more then 2 billion tons in 2013, replacement ofany large portion of this cement by fly ash could significantlyreduce carbon emissions associated with construction. 12. Cement + Water Free lime Fly ashCementitious Material Additional cementitious Material 13. Advantages of Fly ash in ConcreteGreater Long term Strength Improve WorkabilityReduce Permeability Low heat of hydrationIncrease sulphate resistanceIncrease corrosion resistanceReduce Alkali aggregate reaction 14. Disadvantages of Fly ash in Concrete Slower Strength GainAir Content Controle (require more air-entraining admixture) Color Variability(Dark Surface) 15. The EndAny Question Please.???