Mechanical Performance and Microstructure of Silica Powder–Calcium Binder Systems Fabricated by Binder Jetting 3D Printing

This study investigates the feasibility of using a silica powder–calcium-based binder material system for binder jetting (BJ) 3D printing of rocklike materials. After particle size grading, silica powder was mixed with a calcium silicate binder. During the 3D printing process, deionized water was selectively sprayed onto the powder to initiate a hydration reaction, bonding the particles into a specific shape. The printing parameters, including a layer thickness of 100 μm, inkjet volume of 60 μL/mm2, and a printing speed of 51 s/layer, were optimized. Uniaxial compression tests of mold-cast samples showed that particle size–graded samples (cured for 28 days) achieved an average compressive strength of 38.99 MPa, significantly higher than the nongraded samples, with notably lower porosity. This highlights the importance of particle size grading. The 3D-printed samples exhibited a compressive strength of 3.59 MPa after 28 days, lower than that of the mold-cast specimens, but their stress–strain curve resembled that of natural sandstone. Micro-computed tomography (CT) analysis revealed a porosity of 36.7% in the 3D-printed samples, characterized by a layered pore structure and high interlayer porosity, which reduced their strength. In contrast, the mold-cast samples had a porosity of 27.7%. Scanning electron microscope (SEM) analysis showed uneven binder distribution in the printed samples, with insufficient calcium silicate hydrate (C-S-H) gel crosslinking, likely due to inconsistent hydration between the upper and lower layers. The results suggest that BJ 3D printing with silica powder and calcium silicate binder can produce materials with properties similar to natural rock, but further optimization is needed to improve compressive strength and reduce porosity. This study lays the foundation for future applications of BJ printing in construction and other engineering fields.