Synergistic Effect of Multi-Supplementary Materials on Rheology and Ultra-Early Stage Properties of 3D Printable FA-GBFS Geopolymer (2025-12)¶

The rheological performance plays an important role in tailoring 3D printability of geopolymer. However, since geopolymer commonly incorporates industrial solid wastes, how these materials jointly affect the ultra-early rheology remains unclear and limits further optimization. To better modify the ultra-early stage properties of geopolymer, the supplementary materials of steel slag (SS), silica fume (SF), and flue gas desulfurization gypsum (FGD) were incorporated in fly ash (FA) - ground granulated blast furnace slag (GBFS) based geopolymer individually or in combination at 0-50% to investigate their effects on the rheological properties and the underlying mechanisms via rheology tests, mini-slump measurement and microstructure characterization with freeze-dried paste samples after 3 min of mixing. The results indicated that the combined incorporation of SF-SS and SS-FGD mix had more significant influence on the rheology and ultra-early stage properties of FA-GBFS geopolymer. Due to the increased absorption of SF on SS, the dissolution of SF was enhanced by the higher alkalinity from SS and the internal resistance between particles was raised by the coated SS. This synergistic effect facilitated the development of dense and cohesive C(N)-A-S-H and C-S-H gel networks and remarkably improved the internal structural integrity and thixotropic recovery of geopolymer.