Blast Furnace Slag (internationally GGBFS — Ground Granulated Blast Furnace Slag) is produced when liquid blast furnace slag from iron smelting is rapidly quenched with water and subsequently finely ground. The material exhibits hydraulic binding properties and is a key component of climate-optimized cements such as CEM II and CEM III.
The CO2 footprint of blast furnace slag is only 5–10 % of clinker — hence its critical role in low-emission concrete.