Inorganic polymers synthesized using biomass ashes-red mud as precursors based on clay-kaolinite system

Geopolymers are a new class of non-Portland cements produced using an alumino-silicate material (natural minerals, waste and/or industrial by-products) and an alkaline activator to be subsequently cured at relatively low temperatures. The aim of this work is to produce a new type of geopolymer using metakaolin (MK), rice husk ash (RHA) and red mud (RM) by alkaline activation containing sodium silicate and sodium hydroxide (NaOH). Four different geopolymer compositions were prepared at various Si/Al molar ratios (3.85, 4.30, 4.45 and 5.30). A metakaolin based geopolymers were synthesized as a reference. Specimens were characterized by XRD, ATR-FTIR and SEM/EDS. The study revealed that geopolymerization products exhibit an amorphous homogeneous structure with acceptable mechanical properties. RMRHA1 geopolymers shows the best mechanical characteristics (30 MPa) after 60 curing days. MK-RHA-RM based geopolymers obtained seem to offer a feasible alternative to conventional Portland cement contributing to the valorization of the wastes.