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Q: What is the content of SiO2 in fly ash?
  • A. 18% – 25%
  • B. 5% – 24%
  • C. 2% – 12%
  • D. 30% – 60%
Correct Answer: Option D - • Fly ash or pulverized fuel as is the residue from the combustion of pulverized coal collected by mechanical or electrostatic separators from the flue gases or power plants. • It constitutes about 75% of the total ash produced. • The specific surface of about 3500 cm²/g and may be as high as 5000 cm²/g. • The silica contained in fly ash should be present in finely divided state since it combines slowly over a very long period with the lime liberated during the hydration of the cement. • In fly ash, SiO₂ content is 30-60%.
D. • Fly ash or pulverized fuel as is the residue from the combustion of pulverized coal collected by mechanical or electrostatic separators from the flue gases or power plants. • It constitutes about 75% of the total ash produced. • The specific surface of about 3500 cm²/g and may be as high as 5000 cm²/g. • The silica contained in fly ash should be present in finely divided state since it combines slowly over a very long period with the lime liberated during the hydration of the cement. • In fly ash, SiO₂ content is 30-60%.

Explanations:

• Fly ash or pulverized fuel as is the residue from the combustion of pulverized coal collected by mechanical or electrostatic separators from the flue gases or power plants. • It constitutes about 75% of the total ash produced. • The specific surface of about 3500 cm²/g and may be as high as 5000 cm²/g. • The silica contained in fly ash should be present in finely divided state since it combines slowly over a very long period with the lime liberated during the hydration of the cement. • In fly ash, SiO₂ content is 30-60%.