On 13 November 2020, NTPC Ltd., India's largest power producer and a Public Sector Undertaking (PSU) under Ministry of Power, Government of India, announced that it has successfully developed Geo-polymer coarse aggregate from 90% fly ash generated at its plant. It will help in replacing natural aggregates such as cement and will reduce the impact on the environment.
As per the Ministry of Power, NTPC's research project on the production of Geo-polymer coarse aggregate from fly ash meets the statutory parameters of Indian Standards and was confirmed by the National Council for Cement and Building Materials (NCCBM).
Key Highlights:
1- The Geo-polymer coarse aggregates will replace natural aggregates such as cement.
2- NCCBM tested the technical parameters and the suitability to use it in concrete works.
3- The results were found in acceptable range by the National Council for Cement and Building Materials (NCCBM) and was recommended for use in building construction as a substitute for natural aggregates such as cement.
4- Fly ash will help in meeting India's demand of 2000 million metric tons every year for these aggregates for infrastructural development.
5- The NTPC-Ramagundam's achievement will also help in minimizing the impact on the environment.
6- Geo-polymer aggregate is an achievement in expanding the horizon in ash utilisation and has been developed as a part of the concept of waste-to-best, using fly ash generated in the thermal power plant.
Usage of Geo-polymer aggregates
1- Geo-polymer aggregates are used in the construction industry and are environment friendly.
2- They do not require cement for application in concrete as their mortar acts as the binding agent.
3- These aggregates will also help in reducing carbon emission and water consumption.
| Do you Know? Approximately 258 MMT of ash is produced in India every year by the coal-fired thermal power plants. Out of this, only 78% of the ash is utilized. In addition to the current research project, NTPC is searching for new ways to utilize the remaining ash. |
What is 'Fly Ash'?
Fly ash is a byproduct produced by burning pulverized coal in electric power generating plants and causes air pollution. During combustion, the contaminated minerals in the coal such as clay, feldspar, quartz, etc. fuse in suspension and float out of the combustion chamber with the exhaust gases. As the fused material rises, it cools and solidifies into spherical glassy particles called Fly Ash. It is collected from the exhaust gases by electrostatic precipitators or filters.
All fly ashes exhibit cementitious properties to varying degrees depending on the chemical and physical properties of both the fly ash and the cement.
Types of Fly Ash used in concrete
Two types of fly ashes are commonly used in concrete and are as follows:
1- Class C: They are high-calcium fly ashes having less than 2% carbon contents and are produced from burning sub-bituminous or lignite coals. When exposed to water, they react and become hard just like cement.
2- Class F: They are generally low-calcium fly ashes having less than 5% carbon contents but may have carbon contents as high as 10% and are produced from burning bituminous or anthracite coals. Most of them will only react with the byproducts formed when cement reacts with water.
Problems associated with fly ash
1- Toxic heavy metal pollution
2- Water Pollution
3- Radiation Pollution
4- Destruction in mangroves
5- Reduction in crop yields and so on.
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