In this work a complete characterization of electric arc furnace slag (EAF-S) coming from an Italian steel production plant has been carried out with the goal to study if this type of waste is suitable to be used as cement constituent or aggregate for cement based materials. Exploiting the different chemical composition and grain size distribution of two types of EAF-S produced in different steps of the same industrial plant, mortar samples were prepared containing EAF-S as sand (from 10 up to 100%) or 25 wt% ordinary Portland cement replacement, respectively. Chemical and physical results agree with the requirements prescribed for cement and aggregate by European standards. Moreover, the mechanical performances determined on mortar samples seem promising, although an active participation of EAF-S in the hardening process has not been detected.