From Waste to Strength (2025-08)¶

This study investigates the sustainable valorization of recycled polyethylene terephthalate (rPET) fibers through dopamine surface modification for enhanced 3D printed concrete (3DPC). Comprehensive tests on flowability, rheology, buildability, and mechanical anisotropy were conducted to assess the impacts of various MPET fiber content (0–0.5 vol%). The results showed that 0.5 vol% MPET fibers significantly increased dynamic yield stress and plastic viscosity by 247.6 % and 200.0 %, respectively, compared to the control group (P-0), while moderately reducing flowability. The 0.3 vol% content was found to be optimal, enhancing maximum printing heights in hollow cylindrical and rectangular structures by 114.8 % and 130 %, respectively, compared to the control. At this content, the 30-minute early compressive strength reached 66.0 MPa. Quantitative analysis revealed a strong correlation (R² > 0.94) between early strength development parameters and buildability performance, with rate of strength gain exerting greater influence than initial strength. Mechanical anisotropy tests showed that MPET fibers significantly enhanced the flexural strength of 3DPC in the Z-direction of printing. Scanning electron microscopy (SEM) analysis confirmed that dopamine modification significantly enhanced the fiber-matrix interface bonding. This research applies modified recycled PET fibers to enhance 3DPC performance while contributing to sustainability efforts in the construction sector, supporting approaches that integrate material recycling with technical innovation.