The feasibility of using electric and furnace (EAF) dust as partial substitute to the fine aggregate in cement mortar to produce new concrete composite is evaluated. It possesses lime, alumina, silica and iron oxide, the same oxides that make up the cement. The effects of percentage of EAF dust from 0 percent to 10 percent, water cement ratios of 0.45 and 0.55 and age specimen are considered to develop a suitable method for mortar mix design.