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Q18 (IAS/2015) Environment & Ecology › Pollution & Conservation › Waste management practices Official Key

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.

Result
Your answer: —  ·  Correct: A
Explanation

The correct answer is option A (statements 1 and 2 are correct).

Fly ash bricks are light in weight and offer high strength and durability[1], confirming statement 1 is correct. Cement can be replaced by fly ash upto 35%, thus reducing the cost of construction, making roads, etc[1], which validates statement 2.

However, statement 3 is incorrect. Fly ash contains many hazardous substances within its composition in addition to substantial amounts of silicon dioxide (SiO2) and calcium oxide (CaO)[2]. This clearly shows that fly ash is not composed solely of silicon dioxide and calcium oxide, but also contains toxic elements and hazardous substances.

The beneficial uses of fly ash are further supported by additional applications: Fly ash can be used in reclamation of wastelands, abandoned mines can be filled up with fly ash, and fly ash can increase the crop yield and it also enhances water holding capacity of the land[1].

Sources
  1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > Advantages: > p. 67
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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. With reference to 'fly ash' produced by the power plants using coal as fuel, which of the following statements is/are correct? 1. Fly as…
At a glance
Origin: Books + Current Affairs Fairness: Moderate fairness Books / CA: 7.5/10 · 2.5/10
You're seeing a guest preview. The Verdict and first statement analysis are open. Login with Google to unlock all tabs.

This is a classic 'Sitter' disguised as a technical question. Statement 3 is a logical suicide—claiming an industrial waste product is 'chemically pure' and 'non-toxic' contradicts the very definition of pollution. The positive applications (Statements 1 & 2) are standard textbook material found in every basic Environment module (e.g., Shankar IAS).

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Can fly ash produced by coal-fired power plants be used to manufacture bricks for building construction?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > Advantages: > p. 67
Presence: 5/5
“• Cement can be replaced by fly ash upto 35%, thus reducing the cost of construction, making roads, etc, • Fly ash bricks are light in weight and offer high strength and durability, • Fly ash is a better fill material for road embankments and in concrete roads. • Fly ash can be used in reclamation of wastelands. • Abandoned mines can be filled up with fly ash. • Fly ash can increase the crop yield and it also enhances water holding capacity of the land.”
Why this source?
  • Explicitly names 'fly ash bricks' and states they are light-weight with high strength and durability.
  • Notes that fly ash can replace cement (up to 35%), indicating its suitability in building materials and masonry.
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 6: Environmental Issues > Suggestions > p. 115
Presence: 4/5
“NM sHANKAri • The most viable alternative is 'manufactured sand'. It is produced in a stone crushing plant. M-sand is produced from stones used for aggregates, and the quality is consistent and even better than river sand. M-sand is relatively cheaper too. • Use of fly ash from industries as an alternative should be promoted for construction purposes. • 3.”
Why this source?
  • Recommends promotion of using fly ash from industries as an alternative for construction purposes.
  • Frames fly ash use in construction as a viable/encouraged option, supporting practical application.
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > How it is collected? > p. 66
Presence: 3/5
“r Fly ash is generally captured by electrostatic precipitators or other particle filtration equipments before the flue gases reach the chimneys of coal-fired power plants.”
Why this source?
  • Describes how fly ash is collected (electrostatic precipitators), indicating an available, capturable feedstock for manufacturing.
  • Supports feasibility by showing fly ash is a recoverable byproduct from coal-fired plants.
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