Ground Granulated Blast Furnace Slag is obtained by quenching molten iron slag (a by-product of iron and steel-making) from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into a fine powder. Silicate and aluminate impurities from the ore and coke are combined in the blast furnace.  When used as a cementitious material in concrete, GGBFS enhances long-term performance and durability characteristics while reducing life-cycle and maintenance costs. The glass content of slags suitable for blending with Portland cement typically varies between 90-100% and depends on the cooling method and the temperature at which cooling is initiated.