Cement is responsible for 8% of the worldwide CO2 emissions. By using secondary resources from industries such as the metallurgical industry, the carbon footprint of concrete can be decreased drastically. The use of metallurgical ferrous and non-ferrous slags as cement replacement in concrete was researched in the SIM projects DUSC, TOGETHER and 3D2BGREEN to develop sustainable, durable, chemically resistant and 3D-printed concrete.