Geopolymer synthesis with iron ore tailings addition

Full text: Iron ore tailings are mainly stored in dams in Brazil, which cause risks and environmental impacts. The use of these tailings in civil construction is being considered, e. g., by incorporation into geopolymer binders. Geopolymers are cements similar to Portland cement, with the advantage of a lesser environmental impact. They are produced by the alkaline activation of aluminosilicates. In this study the mining tailings of Samarco Mineração were incorporated in a geopolymer matrix. Metakaolin was mixed with an activation solution made of sodium silicate and sodium hydroxide with addition of the tailings. These materials were characterized by optical microscopy, laser granulometry and both X-ray diffraction and fluorescence. 40 to 70 wt% of tailings were added to the binder. The compressive strength of the hardened samples was evaluated after 7 and 28 days of cure and as well as the water absorption. The compressive strength of the samples reached around 43 MPa for 50 wt% (7 days) and 40 wt% (28 days), but it fell considerably for 60-70 wt%. The water absorption was from 10 and 16 wt%.The fraction of tailings in the geopolymer matrix was an important factor for the compressive strength. The observed high compressive strengths suggest that this material has the potential to be employed in civil construction. References: [1] IBRAM. Relatório Anual. Brasília, 2016. [2] J.L. Provis, S.A. Bernal, Annual Rev. Mater. Res. 44 (2014) 299. (author)