Solidification of (Pb–Zn) mine tailings by fly ash-based geopolymer I: influence of alkali reagents ratio and curing condition on compressive strength

Abstract

Fly ash-based geopolymer is a crucial application for tackling climate change, limiting the production of greenhouse emissions. The main aim of this study was to determine the effect of the fundamental parameters on compressive strength to ensure a feasible and effective solidification of mine tailings. Three sodium hydroxide (NaOH) molarities (5, 8, and 10 M) and sodium silicate (Na₂SiO₃) were combined to form the alkaline solution. Four fly ash (FA) proportions (28%, 44%, 54, and 61%) of the dry mix and mine tailings (MT) were utilized as raw materials. This study demonstrated that both 25 °C and 65 °C have a considerable effect on the mechanical properties of geopolymers. The UCS value increased with an increase in NaOH molarity. In addition, the highest Unconfined Compressive Strength (UCS) value was achieved (36.04 MPa) at 10 M. Furthermore, the results also showed that UCS values kept decreasing with the increase of SiO₂/Al₂O₃ and Na₂O/SiO₂ ratios. The optimal UCS values found were in the range of 0.28–0.38 liquid/solid ratio. It has been concluded that the previously mentioned parameters have a strong influence on the mechanical strength of fly ash-based geopolymer with the new proposed FA proportion.