Abstract
	The continuous increase of industrial waste production elicits greater demands on effective re-use of waste in order to enusre appropriate protection of environment. Various industries search for a way to minimize their waste outflow and, when impossible, the waste is used as raw materials for other production branches. Recycling and re-use of industrial wastes help conserve primary commodities and energy resources, puts off natural resources exhaustion and contributes to environmental protection; the latter is endangered by accumulation of waste, its high dustiness and pollution of streams stemming thereof. 
	This article deals with the effective usage of steel slags as replacements to natural aggregates in the making of concrete mixtures of varying qualities. Steel slag is a material of considerable rigor; it originates as a by-product of steel production. Fractions of natural aggregates of 4-8 mm and 8-16 mm were gradually replaced by steel slag. Within the research, four batches were made: three based on steel slag and a comparative one. The basic constitution of the test batches adhered to a 40:30:30 voluminous ratio of fine to coarse aggregate. A presentation of procedures for mixing the experimental batches and test body fabrication follows. Each experimental mixture is presented with records of its physical and mechanical qualities. Examinations of cone settling immediately after mixing and after 30 minutes of setting, cube compression strength after 3, 7, 14, 21, 28 and 90 days and prism compression strength after 28 days were performed.