PT Krakatau Semen Indonesia (KSI) produces Ground Granulated Blast Furnace Slag (GGBFS) using Granulated Blast Furnace Slag (GBFS) as the raw material, which is non-hazardous waste from the steel-making process using Blast Furnace technology. GGBFS is an environmentally friendly product used as an eco-friendly concrete mixture component. In the production process, PT Krakatau Semen Indonesia (KSI) utilizes a Vertical Mill machine with German technology, with a production capacity of 125 tons per hour, capable of producing 690,000 tons of GGBFS per year.