Blast furnace slag is used in the production of cement (iron Portland and blast furnace cement).
Air-cooled blast furnace slag is formed by allowing the molten slag to cool relatively slowly under ambient conditions; final cooling can be accelerated with a water spray. The cooled material is hard and dense, although it can have a vesicular texture with closed pores. After crushing and screening, air-cooled slag can be used in several applications.
Granulated slag is formed by quenching molten slag in water to form sand-sized particles of glass. The disordered structure of this glass gives the material moderate hydraulic cementitious properties when very finely ground into granulated blast furnace slag, but if it can access free lime, the granulated blast furnace slag develops strong hydraulic cementitious properties.
Pelletized or expanded slag is cooled through a water jet, which leads to rapid steam generation and the development of innumerable vesicles within the slag. The vesicular texture reduces the overall density of the slag and allows for good mechanical binding with hydraulic cement paste.
Blast Furance Slag is a nonmetallic co-product which is produced in the process of iron manufacturing, Granulated Blast Furnace Slag is a glassy granular material formed when molten blast furnace slag is rapidly cooled by direct water.
Rapid cooling prohibits the formation of crystals and forms glassy, non-metallic, silicates and alumino silicates of calcium.