Fly ash is one of the residues generated in combustion, and comprises the fine particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash usually refers to ash produced during combustion of coal. Fly ash is generally captured by electrostatic precipitators or other particle filtration equipments before the flue gases reach the chimneys of coal-fired power plants, and together with bottom ash removed from the bottom of the furnace is in this case jointly known as coal ash. Depending upon the source and makeup of the coal being burned, the components of fly ash vary considerably, but all fly ash includes substantial amounts of silicon dioxide (SiO2) (both amorphous and crystalline), being endemic ingredients in many coal-bearing rock strata.
Fly ash is comprised of the non-combustible mineral portion of coal. it is first ground to the fineness of powder. The carbon is consumed leaving molten particles rich in silica, alumina and calcium. These particles solidify as microscopic, glassy spheres that are collected from the power plants exhaust before they can fly away - hence the products name: Fly Ash.
Fly ash is very good resource material. It can advantageously used in cement and concrete works as well as fill applications. Flyash is transported to fly ash storage silo. Fly ash is loaded in close tankers and transported to RMC plants. Fly ash is also available in bags.
Portland cement when mixed with water produce cementitious material in this process free lime is also liberated. This free lime cause of porosity in concrete, however if fly ash available in the mix, free lime will reacts with fly ash to produce additional cementitious materials which produce additional strength and make the concrete denser, thus increase its durability, the present of fly ash also helps reducing heat of hydration.
Fly ash is versatile material and can be utilised in making cement, concrete, ash bricks, and other building products this is also useful material for making road and bagments, development of low ling area, mine filling.
