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Characteristics
of Fly ash
CHEMICAL CHARACTERISTICS
The chemical composition of flyash depends largely on its geological
and geographic factors related to coal mines.
Mostly flyash consists of following chemical composition:
Constituents Percentage of weight
Loss on ignition 1 – 16
SiO2 45 - 65
Al2O3 12 - 30
Fe2O3 2 – 14
CaO 1 – 4
MgO 0.5 – 2.5
Alkalies 0.1 – 3.0
SO3 0.2 – 1.25
Indian Fly ash consists of relatively high silica content,high alumina content, high-unburnt carbon and low CaO content.
Microscopic images of Fly ash
MINERALOGICAL CHARACTERISTICS
The mineral content of Fly ash as determined by XRD
are characterised by
Quartz, mullite, hematite, magnetite and glass content (Glass content
helps to enhance reactivity property of fly ash)
PHYSICAL CHARACTERISTICS
Flyash varies in color from light to dark grey. This
Grey color of ash is due to its carbon content … greater the carbon content
darker is the color of fly ash.
Fly ash differ in size and shape due to :
difference in degree of pulverization of coal.
boiler type
Power load and
efficiency of collection system.
The blaine fineness of Indian Flyashes varies between
3000
– 6000 cm2/gm. Another physical property which is important
regarding the usage of fly ash is its Lime reactivity.Lime reactivity of
fly ash generally is characterized by its fineness, that is with the increase
in fineness of Fly ash, its lime reactivity increases.Lime reactivity of
fly ash increases when it is grinded. Lime reactivity of Indian Fly ash
generally varies from 35 kg/cm2 to
65 kg/cm2
Microscopic images of Fly ash
