Quickly cooled blastfurnace slag solidifies into a glassy sand with markedly latent hydraulic binding forces. This material is preferably used for the emission-reducing and energy-saving production of cement. Slowly cooled blast-furnace slag solidifies in a crystalline manner and becomes a rock with a pore structure that can be influenced as to the size and number of the pores. This crude slag is processed in certain steps to make marketable finished products that are used in construction (particularly road construction) and concrete structures.