Novel inorganic products based on industrial wastes.

This contribution reports the use of industrial slugdes obtained upon processing metallic materials: i) steel wiredrawing (F) ii) red mud (R) from alumina production from bauxite. Three distinct valorisation ways were explored, namely production of black ceramic pigments, belitic clinker, and geopolymers. The colourimetric behaviour of strontium hexaferrite pigments based on steel wiredrawing sludge is slightly poor than the one of formulations prepared from pure reagents. Particularly, L* and b* coordinates are higher in the first case, meaning higher interference of green (-a*) and yellow (b*) undesirable hues. Belitic clinkers were produced by using red mud. Corresponding cements were then used to formulate mortars and their compressive strength was found similar to or better than the one of corresponding mortars prepared by using cement produced from pure chemicals. At the same time the relative amounts of C3A and C4AF diminished in the first case. Finally, the technological properties of geopolymers were affected by the addition of red mud. However, in small proportions the mechanical strength was improved at 28 days curing, certainly due to the high alkaline nature of this sludge.