Producing sodium silicate powder from iron ore tailings for use as an activator in one-part geopolymer binders

•Mining tailings can be used in the production of an alternative sodium silicate.•Eco-friendly and low-cost activators can be produced from SiO2-rich waste materials.•New activators boost geopolymer competitiveness over conventional cements. Mine tailings disposal is an increasingly important issue for mining companies. Two recent tailing dam failures in Brazil have caused unmeasurable environmental, social and economic damages. This study evaluated the use of iron ore tailings (IOT) as a source of silica (SiO2) to produce an alternative form of sodium silicate (SS) for use as an activator in one-part geopolymer binders. The novel SS was produced in a mechano-thermo-chemical process for mixing IOT with sodium hydroxide (NaOH). The materials were characterised by mineral composition, mineral phase, chemical groups and morphology. One-part geopolymer binders were synthesised with commercial SS and SS produced from tailings to compare their reactivity. Compressive strength tests showed that geopolymers produced with tailings SS and commercial SS achieved maximum mechanical resistance values of approximately 32 MPa and 40 MPa, respectively, which are comparable to regular Portland cement.