Fly Ash: Composition, properties, uses

Fly Ash: Composition, properties, uses

Fly Ash


• National Thermal Power Corporation (NTPC) Limited has invited Expression of Interest (EOI) for sale of fly ash, in its endeavour to achieve 100% utilization of fly ash, from the designated plants of the Middle East and other regions.
• Fly Ash is a byproduct from burning of coal in the thermal power generation.


Fly Ash:

• It is called fly ash because it is transported from the combustion chamber by exhaust gases.
• It is collected from the exhaust gases by electrostatic precipitators or bag filters.
• An electrostatic precipitator (ESP) is defined as a filtration device that is used to remove fine particles like smoke and fine dust from the flowing gas.
• It is the commonly used device for air pollution control.


Fly ash includes substantial amounts of silicon dioxide (SiO2), aluminium oxide (Al2O3), ferric oxide (Fe2O3) and calcium oxide (CaO).


• Resemble Portland cement but is chemically different.
• Portland cement is a binding material in the form of a finely ground powder that is manufactured by burning and grinding a mixture of limestone and clay.
• Its chemical composition includes calcium silicates, calcium aluminate and calcium aluminoferrite.
• Exhibit cementitious properties.
• A cementitious material is one that hardens when mixed with water.


• It is used in concrete and cement products, road base, metal recovery, and mineral filler among others.

Harmful Effects:

• Fly ash particles are toxic air pollutants. They can trigger heart disease, cancer, respiratory diseases and stroke.
• When combined with water they cause leaching of heavy metals in ground water.
• It also pollutes the soil, and affects the root development system of trees.

Fly Ash Utilisation:

• NTPC has collaborated with Cement manufacturers around the country to supply Fly Ash.
• To promote the use of Fly Ash bricks in building construction, NTPC has set up Fly Ash brick manufacturing Plants at its Coal based Thermal Power Plants.
• These bricks are being utilized in Plants as well as township construction activities exclusively.
• On average, 60 million Fly Ash bricks are being manufactured annually by NTPCs own Fly Ash brick Plants.
• As per the MoEF&CC directives, NTPC stations must keep at least 20% of total Fly Ash produced in reserve for the issue to Fly Ash brick/blocks/tiles manufacturers and issuing Fly Ash free of cost to them.
• About 9% of the total Fly Ash produced in NTPCs stations, is being utilized by Fly Ash bricks/blocks and tiles manufacturing units annually.
• During the year 2020-21, almost 15 NTPC stations supplied Fly Ash to various Road projects and Ash utilization crossed by nearly 20 million tonnes.
• Over the last five years the fly ash utilisation has grown up by 80% in the country.
• Pradhan Mantri Awas Yojana (Urban) has focused on new construction technologies such as using fly ash bricks that are innovative, and environmentally friendly.
• Even state governments have come out with their Fly ash utilization policies, e.g. Maharashtra was the first state to adopt the policy.
• A web portal for monitoring of fly ash generation and utilization and a mobile based application titled “ASHTRACK” has been launched by the Government.
• GST rates on fly ash and its products have been reduced to 5%

Download Yojna IAS Daily Current Affairs of 6th July 2021

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