Optimization of Precursor Proportions and Performance Characteristics of Iron Ore Tailings-Based One-Part Geopolymers

To promote high-value utilization, bulk iron ore tailings (IOT) were combined with fly ash (FA) and ground granulated blast furnace slag (GGBS) to prepare one-part geopolymers. A simplex lattice design was used to investigate the effects of precursor proportions on compressive strength and fluidity. The FA–GGBS system exhibited continuous strength development with curing age, whereas the IOT–GGBS system showed early-age strength stagnation. In the IOT–FA–GGBS ternary system, strength development was strongly dependent on mix proportion. Polynomial regression models for 28-day compressive strength and fluidity were highly significant (P < 0.0001), with F-values of 52.57 and 22.01 and R ² values of 0.9228 and 0.8334, respectively. Model optimization identified an optimal precursor composition of 35% IOT, 40% FA, and 25% GGBS, yielding the greatest 7–28 day strength gain (10.3 MPa). Response surface analysis showed that compressive strength was enhanced by synergistic gelation and the micro-aggregate effect of IOT when FA and IOT contents were both 30–50%, while fluidity improved at FA contents of 40–60% and IOT contents of 20–40%. Microscopically, C–A–S–H and N–A–S–H gels coexisted in the FA–GGBS and IOT–FA–GGBS systems, whereas the high Si/Al ratio (2.9) in the IOT–GGBS system limited gel development and strength.