Enhancing geopolymer binder reactivity and performance via mechanochemical activation: A comprehensive study of rheological, mechanical, and microstructural properties

In this study, mechanochemical activation was utilized to formulate an eco- and user-friendly geopolymeric binder. This method offers an alternative approach to address challenges inherent in conventional two-part geopolymers. The process involves milling solid-state raw materials with diverse compositions, followed by the addition of water solely to initiate the geopolymerization reaction. Comparative analyses were conducted using conventionally activated geopolymer (CAG) paste and ordinary Portland cement (OPC) paste. The study also investigates the effects of ground granulated blast furnace slag/fly ash (GGBFS/FA) ratios (50:50, 75:25, and 100:0) and sodium silicate/sodium hydroxide (SS/SH) ratios (0.5, 1.5, and 2.5) on the rheological, fresh, mechanical, and microstructure characteristics of mechanochemically activated geopolymer (MAG) paste. The experimental findings indicate that mechanochemical activation reduced rheological characteristics and setting time, accompanied by an 11% increase in strength compared to the conventional activation method. Additionally, increased GGBFS content positively influenced rheological characteristics and mechanical properties, whereas higher SS/SH ratios adversely impacted these aspects. Setting time was significantly reduced with higher GGBFS content but increased with higher SS/SH ratios. Microstructural analysis revealed the presence of additional unreactive particles in both conventionally activated geopolymer and MAG paste containing 50% GGBFS.