Fly ash is a fine particulate residue generated during the combustion of pulverized coal in thermal power plants. Pulverisation involves grinding coal into a very fine powder to ensure more efficient and complete combustion.
When coal is burned, non-combustible minerals in the fuelâ??such as silica, alumina, and ironâ??melt and fuse into tiny glass-like particles. These particles are carried away with flue gases and are captured using electrostatic precipitators or bag filters, resulting in what is known as fly ash. The material is ideal for use in cement, concrete, AAC blocks, and other construction applications.
Class F fly ash is designated in ASTM C 618 and originates from anthracite and bituminous coals. It consists mainly of alumina and silica and has a higher LOI than Class C fly ash. Class F fly ash also has a lower calcium content than Class C fly ash.
Replacement
When used in portland cement, Class F fly ash can be used as a portland cement replacement ranging from 20-30% of the mass of cementitious material.
Advantages
When used as a portland cement replacement, Class F fly ash offers the following advantages when compared to unmodified portland cement:
Increased late compressive strengths (after 28 days)
Increased resistance to alkali silica reaction (ASR)
Increased resistance to sulfate attack
Less heat generation during hydration
Increased pore refinement
Decreased permeability
Decreased water demand
Increased workability
Decreased cost ($80/ton for portland cement vs. $30/ton for fly ash).
Fly ash is a siliceous or siliceous and
aluminous material that, by itself,
possesses little or no cementitious value.
In the presence of water, however, fly ash
chemically reacts with calcium hydroxide
released by hydration of Portland
cement to form compounds possessing
cementitious properties. This can result
in a denser, durable concrete.
Fly ash also can be used to improve concrete workability,
decrease permeability, reduce sulfate attack, decrease
bleeding and segregation, reduce shrinkage, reduce heat
of hydration, increase compressive strength and increase
flexural strength. Fly ash is suitable for a variety of concrete
construction applications from general construction to
dams, piers, massive mat placements, footings and similar
structures.
Fly ash, also known as flue-ash is a residue which is generated during combustion and consists of fine particles. There are impurities in coal which mostly consist of clays, limestone and dolomite particles. These turn up into ash as they cannot be completely burned.
Fly ash is useful in a number of ways and is one of the most researched upon mineral source. It is mainly a pozzolanic substance which contains aluminum and silicon material which in return due to the presence of water can take form of cement.
A lot of research and development initiative have been taken place across the globe to build and develop technologies that can utilize the full potential of fly ash. Royal Mineral takes care to ensure flawless production stages.
Fly ash is a by-product of coal burning at the utility plants. As coal is burned, non-combustible mineral impurities in coal evaporate andcondense into tiny particles of glass, almost totally spherical inshape. The individual particles are very small, like talcum powderand are carried up and out of the boiler in the flow of exhaust gasesleaving the boiler after the coal is consumed.
The fly ash particlesare removed from the exhaust stream in bag houses or electrostatic precipitators and then stored for later shipment
The difference between fly ash and Portland cement becomes apparentunder a microscope. Fly ash particles are almost totally spherical inshape allowing them to flow and blend freely in mixture. Thatcapability is one of the properties making fly ash adesirable admixture of concrete.
Coal Fly Ash
CFA could be used in huge quantities in two areas: ash dyke construction and low-lying region filling [26,27,28]. In several affluent countries, CFA has been utilized successfully as a structural filler.
