Waste Plastic Fiber Reinforced Cementitious Cavity Structures Manufactured by Mortar Extrusion 3D Printing (2025-06)¶

To promote environmental sustainability and enhance construction efficiency, this study uses waste plastic fibers to reinforce cementitious cavity structures manufactured by mortar extrusion 3D printing. The flowability of the printing mortar, as well as the buildability, compressive strength, flexural strength, thermal conductivity, and micro morphology of both the printed solid and (square and triangular) cavity structures were systematically investigated. The results indicate that the incorporation of fibers leads to a reduction in the material consumption of the printed structures and enhances the buildability of the cavity structures, while decreasing that of the solid structure. Despite compressive strength reductions of 18.7 % (solid), 41.5 % (square-cavity), and 35.2 % (triangular-cavity) at 0.3 % fiber content, flexural strength exhibited significant improvements of 78.4 %, 165 %, and 12.3 % respectively, demonstrating remarkable crack-bridging effects. Cavity configurations achieved 25.4 %-52.6 % lower thermal conductivity (0.498–0.783 W/(m·K)) versus solid counterparts (1.056 W/(m·K)), correlating with higher hollowness and porosity in cavity structures that also explains the mechanical-thermal property tradeoffs. This work establishes a sustainable paradigm for upcycling waste plastics into functional building components while advancing automated construction of energy-efficient cavity structures.