Effects of Waste Glass Powder on Printability, Hydration and Microstructure of 3D Printing Concrete (2025-08)¶

3D printing concrete (3DPC) technology plays an increasingly important role in intelligent construction, requiring improved performance and reduced environmental impact. In this study, waste glass powder (WGP) was used as a sustainable supplementary cementitious material (SCM) to partially replace ordinary Portland cement (OPC) or silica fume (SF) in 3DPC. The effects of WGP on printability, mechanical properties, hydration behavior, and pore structure were evaluated. Results showed that replacing OPC with WGP initially enhanced extrudability due to reduced friction, but excessive replacement led to reduced buildability caused by the angular shape of WGP particles. While early-age hydration was delayed, later hydration was accelerated by the filler and nucleation effects. The optimal replacement level of 10–15% WGP improved 28-day compressive strength through pozzolanic reactions. In contrast, replacing SF with WGP had limited impact on mechanical and microstructural performance. These findings provide insights into the effective use of WGP in 3DPC for enhanced performance and sustainability.