Blast Furnace Slag is a by-product of the refining of iron process. In the production of iron, the blast furnace is charged with iron ore, flux stone and coke for fuel. Two products are obtained from the furnace: molten iron and blast furnace slag.

Granulated Blast Furnace Slag (GBFS) is manufactured by rapidly cooling blast furnace slag with water which forms a glassy granular material with latent-hydraulic properties. It is used for cement, concrete, mortar and aggregates.

The most common use for GBFS is GGBFS, Ground Granulated Blast Furnace Slag, which is dried and ground to a fineness similar to Ordinary Portland Cement.
GGBFS is a cement substitute manufactured from GBFS, which can replace up to 70% Ordinary Portland Cement in concrete structures by improving concrete strength, durability and reducing carbon footprint.