Mining and agricultural Residues-based composites materials for engineering applications: Red mud and Rice husk Ash Geopolymers

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The processing of raw materials into finite products releases residues and waste, the management of which becomes an environmental matter. In the Bayer process the reaction of bauxite mineral with NaOH for alumina production releases red mud RM, a waste that occupies land and causes environmental hazards. Rice is the staple food for a large part of the population in Guinea. Rice husk RH is generated in bulk quantities and poses environmental hazards. It contains approximately 20% silica a suitable material for a wide range of application. After burning the resulting rice husk ash RHA contains about 90% silica. Geopolymer technology is a promising application for the use of industrial wastes. For the synthesis of a RM/RHA based composite Geopolymer (GP), RM from a local Alumina Plant; RH from a local mill in Guinea and water glass solution WGS were used. Different mix ratios of RM, RHA and WGS were performed. The specimens were tested for compressive strength at different temperatures. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) were used to investigate the microstructure of parent materials and the resulting GP specimens. The analyses showed that the final product is mainly composed of amorphous Geopolymer material and that higher temperatures improve the compressive strength.