With reference to ‘fly ash’ produced by the power plants using coal as fuel, which of the following statements is/are correct?

  1. Fly ash can be used in the production of bricks for building construction.
  2. Fly ash can be used as a replacement for some of the Portland cement contents of concrete.
  3. Fly ash is made up of silicon dioxide and calcium oxide only, and does not contain any toxic elements.

Select the correct answer using the code given below.

[UPSC Civil Services Exam – 2015 Prelims]

(a) 1 and 2

(b) 2 only

(c) 1 and 3

(d) 3 only


Answer: (a)        

Explanation:

  • Fly ash is the residual substance that results from the combustion of pulverized coal and is carried away from the combustion chamber by exhaust gases.
  • This by-product is generated primarily by coal-fired electric and steam generating plants.
  • Furthermore, fly ash finds numerous uses each year in a wide range of engineering applications, such as soil and road base stabilization, grouts, structural fill, and asphalt filler.
  • Additionally, fly ash is utilized in the production of Portland cement, embankments, flowable fills, geopolymers, roller compacted concrete, bricks, metal matrix composites, waste treatment and stabilization, and catalysts.
  • Fly ash consists primarily of oxides of silicon, aluminum iron and calcium. Magnesium, potassium, sodium, titanium, and sulfur are also present to a lesser degree.
  • Environmental benefits
    • Incorporating fly ash into the production of concrete can enhance its durability, thereby prolonging the lifespan of concrete roads and structures.
    • Additionally, the use of fly ash in place of manufactured cement results in a net reduction of energy usage and greenhouse gas emissions, as well as other air pollutants.

Consider the following statements:                                                                   The Parliament of India can place a particular law in the Ninth Schedule of the Constitution of India. The validity of a law placed in the Ninth Schedule cannot be examined by any court and no judgement can be made on it. Which of the statements given above is/are correct?

Consider the following statements:                                               

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Consider the following statements:                                                         The Parliament of India can place a particular law in the Ninth Schedule of the Constitution of India. The validity of a law placed in the Ninth Schedule cannot be examined by any court and no judgement can be made on it. Which of the statements given above is/are correct?

Consider the following statements:                                               

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