Materials called very fine aggregate or mineral filler may affect the performance of concrete in an either positive or a negative way. Washing the aggregate residue has been the only way to solve this matter until now. This study was to determine how the content of mineral filler might affect the properties of concrete. Two types of aggregates with different amounts of cement and mineral filler were used. Basically, mineral filler replaced sand. The effect of applying different amounts of mineral filler on concrete was then determined. The addition of 7–10% of mineral filler to fine aggregate (0–2 mm) was found to considerably improve the properties of concrete. Compressive and flexural strength were improved and permeability, absorption and porosity decreased. With more than 10% either the concrete properties remained constant or changed negatively. 23 refs.