Mechanical and Structural Performance of 3D-Printed Cement Mortar Incorporating Modified Basic Oxygen Furnace Slag and Waste Printed Circuit Board Powder: Experimental and Numerical Study

This study developed 3D-printable cement mortar (3DPCM) incorporating modified basic oxygen furnace slag (MBOFS) sand and waste printed circuit board powder (WPCBP). Five WPCBP-to-cement ratios, namely 0, 10, 20, 30, and 40 wt.%, were adopted, and the printability of each mixture was first evaluated. Subsequently, the compressive, flexural, and splitting tensile behaviors of mold-cast and 3D-printed specimens were compared, and the structural response of 3D-printed truss members was assessed through four-point bending tests and finite element analysis. The results showed that all mixtures could be printed stably. For the standard 3D-printed specimens, WPCBP/C = 20 wt.% provided the highest quasi-static mechanical performance, and the mechanical response exhibited clear anisotropic behavior. In contrast, the mechanical performance of the mold-cast specimens decreased with increasing WPCBP content. In the 3D-printed truss members, the average peak load increased from 8.041 to 20.710 kN, the displacement corresponding to the peak load increased from 0.201 to 0.683 mm, and the finite element analysis reasonably captured the overall load–displacement response. Overall, MBOFS sand and WPCBP can be effectively incorporated into 3DPCM and show potential for sustainable structural material applications.