Question 89 from UPSC CSE 2020 - ENVIRONME NT

Question

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:

IASCODEX · Accepted Answer

Correct Option: D. 1, 2, and 3

Strategy: - Evaluate statements based on the known industrial and environmental utility of steel slag.
- Confirm its established use as an aggregate in base road construction.
- Verify its role in soil amendment due to alkaline content.
- Acknowledge its application as a raw material replacement in cement production.
- Conclude that all statements are correct given these multi-sectoral applications.

Key Info: Steel slag is a by-product generated during the steel-making process, whether via the Basic Oxygen Furnace (BOF) or Electric Arc Furnace (EAF). This material contains silicates, calcium, iron, and other mineral components, giving it unique properties valuable across sectors:

-   **Construction of base road**: Steel slag is frequently used as an aggregate in road construction, particularly for base and sub-base layers. Its high density and good mechanical stability improve road strength and durability. Guidelines from the Indian Road Congress (IRC) and global studies recognize steel slag in pavement mixes (asphalt and concrete) due to its strength and binding qualities.
-   **Improvement of agricultural soil**: Steel slag acts as a soil amendment, especially in acidic soils. It contains calcium and magnesium oxides, which help neutralize soil acidity, and contributes silicon, an important plant nutrient. It can function as a liming agent and a silicate fertilizer, supported by agricultural research in India, Japan, and Europe.
-   **Production of cement**: Steel slag is employed in cement manufacturing, where it substitutes natural raw materials or serves as a component for Portland Slag Cement and clinker. Standards (e.g., BIS in India and ASTM internationally) permit partial replacement of cement ingredients with steel slag, typically up to 10%, owing to its mineral composition that supports setting and strength.

Steel slag is also utilized in water treatment and mine reclamation to neutralize acidic environments. Its use in these fields promotes a circular economy and reduces the environmental landfill burden associated with industrial by-products.

IASCODEX · Answer

Option A: 1 and 2 only

IASCODEX · Answer

Option B: 2 and 3 only

IASCODEX · Answer

Option C: 1 and 3 only

Steel slag can be the material for which of the following? Construction of base road Improvement of agricultural soil Production of cement Select the correct answer using the code given below:

Steel slag can be the material for which of the following?

Construction of base road

Improvement of agricultural soil

Production of cement
Select the correct answer using the code given below: