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Fly Ash
Consider the following statements with reference to the Fly ash:
- Fly ash is a byproduct from burning pulverized coal in electric power generating plants.
- It consists primarily of oxides of silicon, aluminum iron and calcium.
- There are two common types of fly ash: Class D and Class H.
Which of the statement(s) given above is/are correct? Choose the correct answer from the codes given below:
A |
1 and 2
|
|
B |
2 and 3
|
|
C |
1 and 3
|
|
D |
1, 2 and 3
|
Your Ans is
Right ans is A
Your Answer Is Correct
Your Answer Is Wrong
Explanation :
Context: Recently, National Thermal Power Corporation(NTPC) Ltd. has started to collaborate with cement manufacturers across the country to supply fly ash as part of its endeavour to achieve 100% utilisation of the by-product produced during power generation.
About Fly Ash
- Fly ash is a fine powder that is a byproduct of burning pulverized coal in electric generation power plants.
- During combustion, mineral impurities in the coal (clay, feldspar, quartz, and shale) 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 bag filters.
- All fly ashes exhibit cementitious properties to varying degrees depending on the chemical and physical properties of both the fly ash and cement.
- Fly ash includes substantial amounts of Silicon Dioxide (SiO2), Aluminium Oxide (Al2O3), Ferric Oxide (Fe2O3) and Calcium Oxide (CaO).
Types
Fly ash is classified as either Class C or Class F ash based on its chemical composition.
- Class C ashes are generally derived from sub-bituminous coals and consist primarily of calcium alumino-sulfate glass, as well as quartz, tricalcium aluminate, and free lime (CaO). Class C ash is also referred to as high calcium fly ash because it typically contains more than 20 per cent CaO.
- Class F ashes are typically derived from bituminous and anthracite coals and consist primarily of an alumino-silicate glass, with quartz, mullite, and magnetite also present. Class F, or low calcium fly ash has less than 10 percent CaO.
Applications
- Fly ash can be used as prime material in many cement-based products, such as poured concrete, concrete block, and brick.
- One of the most common uses of fly ash is in Portland cement concrete pavement.
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