UPSC CSE Prelims
Question 21
With reference to 'fly ash' produced by the power plants using coal as fuel, which of the following statements is/are correct?
- Fly ash can be used in the production of bricks for building construction.
- Fly ash can be used as a replacement for some of the Portland cement contents of concrete.
- 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.
View correct answer and explanation
Correct answer: A
Correct Option: A
Explanation: Fly ash, a coal-combustion residue, can improve bricks and partially substitute for cement in concrete. It contains a variety of compounds and may contain toxic trace elements.
Statement/Pair-wise Analysis:
Statement/Item 1: Correct - Fly-ash bricks are used in building construction.
Statement/Item 2: Correct - Its pozzolanic properties allow partial replacement of Portland cement.
Statement/Item 3: Incorrect - Fly ash contains alumina and other oxides and can include hazardous trace metals; it is not only silica and lime.
Option-wise Analysis:
A: Correct - includes all and only the correct items.
B: Incorrect - omits correct statement/item 1.
C: Incorrect - includes incorrect statement/item 3; omits correct statement/item 2.
D: Incorrect - includes incorrect statement/item 3; omits correct statement/items 1, 2.