Comprehensive Study on Design Optimization and Retardation Mechanism of SS-GGBS-FA Ternary Geopolymer Mortar

A ternary geopolymer mortar (TGM) was synthesized using steel slag (SS), granulated blast furnace slag (GGBS), and fly ash (FA) as raw materials. The effect of the SS content (0-60%) and the GGBS/FA mass ratio (5:1 to 1:5) on the TGM's setting time was studied. To address the issue of rapid setting, the impact of different mixing methods ((A) dry mixing, (B) pre-dissolution, and (C) pre-coating) and dosages of BaCl₂ on the setting and hardening properties of TGM was further explored. The hydration product evolution and microstructural characteristics were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS), with an in-depth analysis of the retarding mechanism of BaCl₂. The results indicate that, as the steel slag content increases, the setting time of TGM significantly shortens. The setting time decreases slightly with an increase in the GGBS/FA mass ratio. The mixing method influences the retarding effect of BaCl₂, with the C method showing significant advantages over both the A and B methods. Under the C mixing method, BaCl₂ consumes the alkaline components (SiO₃^2-) in the alkaline activator and forms a BaSiO₃ coating layer on the precursor surface, which further delays the hydration process of the precursor particles. This study provides a promising approach for the high-value utilization of multi-source solid waste and suggests that future research should focus on large-scale application strategies and long-term performance evaluation to support its practical use in sustainable construction.