UPSC Prelims 2020 Q76: Environment & Ecology – Renewable Energy & Green Technologies
Steel slag can be the material for which of the following ?
1. Construction of base road
2. Improvement of agricultural soil
3. Production of cement
Select the correct answer using the code given below:
- (a) 1 and 2 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Answer: (d) 1, 2 and 3
Explanation
Uses of steel slag
Steel slag is the by-product left after impurities are removed from molten steel.
India generates over 19 million tonnes a year, and the Government promotes its reuse.
| Use | Possible? | How |
|---|---|---|
| 1. Construction of base road | Yes | Processed slag aggregate replaces natural stone; the CRRI built a steel-slag road in Surat (2022) |
| 2. Improvement of agricultural soil | Yes | Slag is rich in lime (CaO) and silicates, so it can correct acidic soils |
| 3. Production of cement | Yes | Used in Portland slag cement and as a clinker substitute |
Reusing slag reduces landfill, mining of aggregates and CO₂ from cement making.
Answer: (d) 1, 2 and 3.
Why each option is right or wrong
- (a) Incorrect. Steel slag is also used in cement production, not just roads and soil.
- (b) Incorrect. It leaves out road construction, a major use of processed slag.
- (c) Incorrect. Its lime content also makes slag useful for treating acidic farm soils.
- (d) CORRECT. Steel slag is used in roads, soil improvement and cement.
Key point
Steel slag: road aggregate (Surat steel-slag road), lime source for acidic soils, and raw material for slag cement.
Remember
Steel slag: roads, soil, cement.
Common mistakes
- Thinking industrial waste cannot be used on farmland; slag's lime corrects soil acidity.
- Not knowing slag cement is a standard product.
- Treating slag only as landfill waste.
Exam tip
For 'waste to resource' questions, assume broad reuse unless an option is clearly harmful.
Sources
- Ministry of Steel — Steel Slag Utilisation
- CSIR-Central Road Research Institute — Steel slag road technology