Effect of nano silica with high replacement of GGBS on enhancing mechanical properties and rheology of 3D printed concrete

This study investigates the synergistic effects of incorporating nano-silica (NS) and high replacement levels of ground granulated blast furnace slag (GGBS) on the mechanical properties and rheology of 3D printed concrete. Concrete mixes were designed with varying proportions of cement and GGBS (50-70 %) combined with a fixed dosage of 1 % NS. The results demonstrated that NS significantly enhanced both rheological behaviour and compressive strength. Mixtures containing NS exhibited higher static and dynamic yield stress, optimized plastic viscosity and controlled thixotropic properties, favourable for enhanced buildability, pumpability, and extrudability in 3D printing. The optimal mix C3G7N1 (70 % GGBS and 1 % NS), achieved a compressive strength of 105 MPa at 28 days, showcasing superior mechanical performance and rheological control. Moreover, high-volume GGBS significantly reduced the carbon footprint, supporting sustainable 3D concrete printing applications. This research provides an inclusive understanding of material performance critical for advancing scalable and sustainable additive manufacturing in construction.