Printable and mechanical properties of 3D-printed nano-silica modified concretes

This study investigated the effect of nano-silica (NS) on the fresh and hardened properties of 3D-printed concretes. It is observed that the addition of NS significantly reduces fluidity and setting time while increasing yield stress and thixotropy, thereby enhancing workability. Furthermore, the observed increase in thixotropic behavior indicates that reducing NS particle size improves buildability. Specifically, incorporating 1.5 wt.% of 20 nm NS increases compressive strength by 27.25% at 7 days and 15.61% at 28 days compared to the control group. Notably, the mechanical properties of 3D-printed concrete surpass those of casted ones. Moreover, 3D-printed concretes exhibit evident anisotropy. Additionally, the analysis of microstructure, hydration heat, and phase composition indicates that the incorporation of NS can refine the pore structure and accelerate the hydration process, thereby enhancing the mechanical properties of 3D-printed concretes. The findings suggest that the integration of nano-silica positively impacts both the fresh and hardened properties of 3D-printed concretes.