Steel making slag formation is part of the intrinsic process of steel production. The European steel industry generated about 21.8 million tons of slag. About 24 % were still landfilled (2.8 Mtons) or self-stored (2.2 Mtons). From the environmental point of view, the landfill of slags is a significant source of pollution. RESLAG will face this environmental problem by providing 4 eco-innovative solutions for the valorisation of steel slags through 4 pilots development.