The correct answer is 1, 2, and 3.

• Steel slag, a by-product of steel making, is produced during the separation of the molten steel from impurities in steel-making furnaces.
• One of the ingredients of asphalt is steel slag, a by-product of the steel and iron production processes.
• Asphalt roads are made of a mixture of aggregates, binders, and fillers.
• The aggregates are typically iron or steel slag, sand, gravel, mixed with asphalt that produces bitumen.
• The bitumen, produced by the refineries, plays an important role in road construction. Hence, statement 1 is correct.
• Steel slags can be used in several activities, such as construction and paving, and also in the agricultural sector
• Steel slag has the ability to correct soil acidity, as it contains some nutrients for the plants and also as silicate fertilizer that is capable of providing silicon to the plants. Hence, statement 2 is correct.
• Steel slag, another waste from the Iron & Steel Industry, has shown potential for use as a raw mix component up to 10% in the manufacture of cement clinker.
• Steel slag can also replace granulated blast furnace slag up to 10% in the manufacture of Portland Slag Cement. Steel slag has been used successfully to treat acidic water discharges from abandoned mines. Hence, statement 3 is correct.