The primary components of iron and steel slag are limestone (CaO) and silica (SiO2). Other components of blast furnace slag include alumina (Alsub>2O3) and magnesium oxide (MgO), as well as a small amount of sulfur (S), while steelmaking slag contains iron oxide (FeO) and magnesium oxide (MgO).
Slag produced in steelmaking undergoes 4 processes.
1. Solidifying and cooling of molten slag: This is done through different techniques such as air cooling in a yard, subjecting the slag to compressed air; subjecting to water sprinklers after being poured to a steel box.
2. Crushing and magnetic separation: Slag contains 10-40% metal iron is being generated in the different process of steelmaking such as converter, hot metal/molten steel ladle or tundish. Iron is separated after the slag is cooled and crushed through means of magnetic separation. This constitutes part of the by-products.
3. Crushing and classification: This is required for commercial purpose as the customer usually requires a certain grain size. Classification is done through screening.
4. Aging treatment: This is done either water from rainfall or utilizing steam/hot water/high pressure aging treatment. The treatment involves the hydration of free CaO and MgO. The hydration reaction causes them a significant increase a size which is not suitable for road construction applications.
