Blast furnace slag is a by-product resulting from iron pig manufacture. With its oxide composition being basically similar, to quite a great extent, to that of clinker, and its partial content in clinker mineral components, blast furnace slag may be employed among other alternative raw materials to substitute integrally or partly the traditional silicate and aluminate components in the raw mix in spite of its relatively small deficit in calcium oxide. This is likely to be the way to obtain expected process technology effects, such as: reducing the specific heat consumption in the clinker burning plant, increasing the hourly clinker output, reducing the specific consumption of raw materials, reducing the specific toxic emission, etc. These effects have been assessed by means of calculation, and the subsequent results have been confirmed in experiments in the laboratory and at scale. Depending on the specific local conditions, the use of blast furnace slag is likely to have an extremely positive effectiveness in economical terms and may add up to the ongoing efforts to protect the environment.