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:

Steel slag is a by-product of steelmaking, and all three uses are established. Here is each statement.

• Statement 1 (correct): Processed and aged steel slag, which has been made volume-stable, is used as aggregate in road base and sub-base layers such as Wet Mix Macadam and granular sub-base. Indian Roads Congress guidance permits it, and it reduces dependence on natural aggregates.
• Statement 2 (correct): Steel slag contains calcium and magnesium oxides, so it acts as a liming material that neutralises acidic soils. It also supplies silicon and other micronutrients, which is why it is marketed as a soil conditioner.
• Statement 3 (correct): Steel slag can serve as a raw material or clinker substitute in Portland cement manufacture, because its calcium silicate phases contribute cementitious properties. Blast furnace slag is the more common example, but steel slag use is also permitted and practised.

Core concept: valorisation of industrial by-products and the circular economy. This links to GS-III on waste management, infrastructure and sustainable resource use, and to Mains questions on converting industrial waste into resources.

Trap: aspirants reject statement 2 because they associate slag only with construction. The calcium-rich chemistry of slag is what makes it useful as a liming agent.