Prelims 2015 · Environment · Question 18
With reference to 'fly ash' produced by the power plants using coal as fuel, which of the following statements is/are correct?<br/>1. Fly ash can be used in the production of bricks for building construction.<br/>2. Fly ash can be used as a replacement for some of the Portland cement contents of concrete.<br/>3. Fly ash is made up of silicon dioxide and calcium oxide only, and does not contain any toxic elements.<br/><br/>Select the correct answer using the codes given below.
Answer
1 and 2
1. Correct. Fly ash is widely used to make fly ash bricks/blocks for building construction.
2. Correct. Fly ash is a supplementary cementitious material and can replace a part of Portland cement in concrete.
3. Incorrect. Fly ash is not made only of silicon dioxide and calcium oxide; it also contains alumina, iron oxides and may contain trace toxic elements/heavy metals like arsenic, lead, mercury, etc.
Hence, statements 1 and 2 only are correct.