Rheological Optimization and Mechanical Performance Assessment of High-Volume GGBS-Silica Fume Mortars for 3D Printing (2025-11)¶

This study investigates the rheological and mechanical performance of high-volume ground granulated blast-furnace slag (GGBS) cement mortars incorporating silica fume (SF) tailored for extrusion-based three-dimensional concrete printing (3DCP). Mortar formulations with GGBS contents ranging from 50% to 70% were evaluated to explore their suitability for 3D printing applications. A comprehensive evaluation was conducted on key rheological parameters including static and dynamic yield stress, plastic viscosity, thixotropy and flow index, together with compressive strength at 7 and 28 days. The results reveal that increasing GGBS content significantly enhances shear-thinning behaviour and long-term strength, while reducing yield stresses and thixotropy. In contrast, SF markedly increases static and dynamic yield stress and improves structural rebuild capacity, effectively compensating the reductions induced by high GGBS levels. Principal Component Analysis and ANOVA confirm distinct and interactive effects of GGBS and SF across fresh and hardened properties, while desirability function analysis identifies an optimal mix comprising 54.91% GGBS and 20% SF. This formulation balances pumpability, buildability, and strength, achieving compressive strengths of 83.1 MPa at 7 days and 108.7 MPa at 28 days with a global desirability index of 0.557. Importantly, the embodied carbon of this optimized mix is 365.5 kg CO2-e/m3, corresponding to a 49% reduction compared with a fully cementitious reference mix. This demonstrates a high-performance, lower-carbon solution for 3D-printed construction. These findings support the potential of GGBS-silica fume blends for low carbon 3D printing applications.