Geopolymer materials from wastes for sustainable building application: mineralogical and morphological characterization

Red mud (RM) is the primary waste product generated through the Bayer from caustic digestion of bauxite and its disposal represents one of the biggest issues in the mining industry due to its hight alkalinity. New technologies are being developed for its treatment and reuse, according to circular economy and environmental protection. The presence of aluminium and silicon oxides makes RM a suitable material for developing geopolymer formulations, in combination with commercial metakaolin (MK). In fact, geopolymers are usually obtained from aluminosilicate precursors by polycondensation in an alkaline environment using sodium silicate. In addition to activation in an alkaline environment, in recent years an acid-type activation has also been developed regarding the geopolymerization reaction using a phosphoric acid solution. In this work, both basic- and acid- geopolymer were synthesized and characterized through different techniques. The obtained samples show excellent chemical and physical properties and high compressive strength, suggesting their application in the building sector.