The possibility of using the metallurgical slags of metallurgical enterprises of the Novokuznetsk city as a filler in the manufacture of mortars is shown in this work. The methodology of the research is based on the previously developed technological schemes for recycling metallurgical slags in the form of a system of work stages, which is associated with the need for a consistent transformation of the properties of slags, and what is achieved through a series of mechanical and physicochemical effects. The use of the express method of selecting the composition of aggregate fractions from open-hearth slag made it possible to obtain the densest packing of filler grains in compliance with the strength requirements for mortars. On a set of basic physical and mechanical quality indicators, experimental mortars meet the current regulatory requirements, which allows us to recommend their compositions for testing in industrial conditions.