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:
- 1 and 2
- 2 only
- 1 and 3
- 3 only
Explanation
Statement 1 and 2 are correct
- Fly ash is primarily generated as a by-product of coal combustion in thermal power plants. Its improper disposal leads to environmental concerns, as it can pollute air and water, introduce heavy metals into water bodies, and adversely affect crops and vegetation when it settles on leaves, thereby reducing photosynthesis. However, when managed properly, fly ash has several beneficial uses. It can replace cement in construction up to about 35%, reducing costs, and is used to make lightweight and durable bricks. It serves as an efficient fill material for road embankments and concrete roads. Fly ash is also useful in the reclamation of wastelands and in filling abandoned mines. In agriculture, controlled application of fly ash can improve soil properties by enhancing water-holding capacity and increasing crop yield. Nonetheless, its deposition on plant leaves remains harmful, as it hampers photosynthesis.
Statement 3 is incorrect
- Fly ash is oxide-rich and consists of silica, alumina, oxides of iron, calcium, and magnesium and toxic heavy metals like lead, mercury, cadmium, arsenic, cobalt, and copper. Oxides present in large quantities are aluminium silicate, silicon dioxide (SiO2) and calcium oxide (CaO).
