Effect of early-hydration on paste rheological properties for ultrahigh performance geopolymer concrete(UHPGC)

The development of ultrahigh-performance geopolymer concrete (UHPGC) has attracted considerable attention owing to its low carbon emissions and sustainable development. However, its rheological properties are affected by complex factors, which are difficult to control, limiting its engineering applications. Therefore, improving the rheological properties of UHPGC is critical. This study employed response surface methodology (RSM) to investigate the effects of granulated blast furnace slag (GBFS), alkali activator modulus (AAM), and water-to-geopolymer binder (W/B) on the rheological properties (plastic viscosity, yield stress) and compressive strength of UHPGC. The results confirmed the suitability of RSM for multi-objective optimization: at the optimal mix (60.9 % GBFS, AAM=1.44, W/B=0.33), plastic viscosity, yield stress, and compressive strength reached 3.15 Pa·s, 20.60 Pa, and 128.5 MPa, respectively. GBFS and AAM, along with their interaction, significantly influenced the rheological properties, providing a practical mix design reference for engineering application of UHPGC.