This paper reports the results of some experimental studies on the use of non-ground-granulated blast-furnace slag (NGGBFS) as fine aggregate in concrete. Two groups of concrete samples were produced. The NGGBFS/sand ratios were 0% (reference), 25, 50, 75, and 100%. The first group (CI) contains only 0 to 7 mm (0 to 0.276 in.) sand as fine aggregate. The second group (C2) contains two sub-types of fine aggregates that are 0 to 3 nun (0 to 0.118 in.) and 0 to 7 mm (0 to 0.276 in.) sands. NGGBFS replaces 0 to 7 mm (0 to 0.276 in.) sand in both groups. Strength and durability characteristics of concrete were compared with respect to control samples and vice versa. According to the results, if the NGGBFS/ sand ratio is high in the C1.type, the concrete is porous and has relatively. low compressive strength. In the C2 type, however concrete strength and durability characteristics were better than those in the CI type. It was concluded that the non-ground-granulated blast-furnace slag can be used as fine aggregate under some conditions.