Mechanical and chemical analysis of one-part geopolymers synthesised with iron ore tailings from Brazil

The mining industry is closely related to economic development in many countries but is also responsible for generating large amounts of waste materials. If not properly processed and/or stored, these residues can present environmental and social risks. Geopolymers are known for their ability to be used in many applications where ordinary Portland cement (OPC) is commonly used. They present some advantages over OPC, such as the use of several forms of waste as precursor material, better heat and fire resistance and higher strength. In this study, one-part geopolymer cement pastes were synthesised with different iron ore tailings (IOT) to evaluate the use of IOT as fillers. Three different IOTs were studied to verify the effects of the fillers in the geopolymer cements. The one with the highest compressive strength was chosen to be evaluated for the impact of increasing the proportion of tailings. The tailings-metakaolin-based cements were cured at room temperature and had their compressive strength assessed after 1, 3,7 and 14 days. Particle size distribution, X-ray diffraction, X-ray fluorescence and infrared spectrometry were also analysed. It was seen that part of the iron, originally from the tailings, reacted and seems to have been incorporated into geopolymer tetrahedral bonds. The one-part geopolymer cement pastes achieved maximum compressive strength at around 50 MPa. They proved that IOT can be satisfactorily incorporated as filler, which is desirable for better mining tailing management practices.