"Ground Granulated Blast-Furnace Slag" (GGBFS) is produced by the process for grinding "Granulated Blast Furnace Slag" (GBFS) that is a kind of by-product produced via blast furnace operated in steel works. Ground granulated blast furnace slag (GGBFS) has been used in the construction industry for years as a replacement for Ordinary Portland Cement (OPC). Ground granulated blast furnace slag also has a lower heat of hydration and, hence, generates less heat during concrete production and curing. GGBFS cement can be added to concrete in the concrete manufacturer's batching plant, along with Portland cement, aggregates and water. The normal ratios of aggregates and water to cementitious material in the mix remain unchanged. GGBS is used as a direct replacement for Portland cement, on a one-to-one basis by weight. Replacement levels for GGBS vary from 30% to up to 85%. Typically, 40 to 50% is used in most instances. This study is the result of using 70% GGBFS instead of cement even if it is allowed to use maximum 25% of GGBFS instead of it. The use of GGBFS, which has an amorph structure and shows pozzolan characteristics when finely granulated, as a replacement material within the systems of cement or concrete positively effects the properties of fresh and hardening concrete.