Synergistic effects of polypropylene fibers on the strength and durability properties of <scp>3D</scp> printed concrete

Abstract Optimizing material composition in 3D concrete printing, is essential to enhance both printability and structural performance. This study explores the influence of polypropylene fibers on the fresh and hardened properties of 3D printed concrete. Marble powder waste was incorporated as a partial replacement for cement of 10% to promote sustainability, while polypropylene fibers were added at varying dosages from 0.1% to 0.5% to assess their impact on fresh and hardened state behavior. Fresh properties such as extrudability and buildability were systematically evaluated. Notably, the mix with 0.2% fiber content demonstrated superior buildability, ensuring stable layer deposition and structural integrity during the printing process. Further, in terms of hardened performance, 0.2% polypropylene fiber inclusion significantly enhanced compressive, flexural and interlayer bond strengths. Durability was assessed through water absorption and sorptivity tests, where the optimal mix exhibited reduced permeability, indicating better resistance to moisture ingress and enhanced long‐term durability. Scanning Electron Microscopy analysis further validated these observations, demonstrating the microstructure with better fiber distribution, less porosity, and the development of a compact C–S–H gel. These findings highlight the potential of integrating an optimal 0.2% polypropylene fiber content in 3D Printing Concrete to achieve superior performance in better buildability and durability performance.