Study on the mechanical properties of 3D-printed continuous jute yarn-reinforced concrete

The inherent brittleness of 3D-printed concrete limits its structural applications. To enhance toughening methods and improve their effectiveness, this study introduced a novel 3D printing strategy that coaxially embeds continuous flexible jute yarns as toughening agents into concrete. Macroscopic mechanical tests reveal how the jute yarn diameter and volume content methodically influence the compressive strength, flexural strength, mechanical anisotropy, and toughness of 3D-printed cement composites cured for 3 and 28 days. Our results demonstrate that the incorporation of continuous jute yarn significantly enhances mechanical properties under Z-axis loading, markedly increasing the flexural strength of 28-day-cured composites by 203.1 %, coupled with a 734.78 % improvement in the flexural-to-compressive strength ratio and a 210.35 % gain in fracture energy compared with the control group. Microscopic analysis revealed that synergistic toughening mechanisms such as crack bridging, interface debonding, and plastic deformation during jute yarn pull-out are primarily responsible for this enhanced strength and toughness. • Continuous jute yarn integration enhances mechanical performance of 3D-printed concrete. • Optimized continuous jute yarn diameter and content significantly improve flexural strength and toughness. • Increasing the diameter and content of continuous jute yarns transforms the failure mode of concrete from brittle to ductile.