Rheological, Mechanical, and Self-Recovery Performance of 3D-Printed ECC Reinforced with Shape Memory Alloy Fibers (2025-10)¶

The increasing demand for rapid and sustainable construction methods has accelerated the adoption of 3D-printed concrete (3DPC) technologies. However, integrating conventional steel reinforcement into layer-by-layer printing processes remains a significant challenge. This study investigates the influence of shape memory alloy (SMA) fibers on the rheological behaviour, extrudability, mechanical performance, and self-recovery capacity of 3D-printed engineered cementitious composites (3DP-ECC). SMA fibers with a 0.4 mm diameter, lengths of 26 mm and 32 mm, and volume fractions of 0.35%, 0.70%, and 1.0% were incorporated into the mix design to evaluate their effects on material performance. Results indicate that fiber length and content significantly affect rheology and extrudability, with static yield stress increasing by up to 50.64% and dynamic yield stress reaching 253 Pa at 1.0% fiber content. SMA-reinforced ECC exhibits superior strain-hardening behaviour, with cast specimens achieving peak stress up to 5.78 MPa, ultimate strain up to 7.67%, and strain recovery rates exceeding 53.9% compared to 3D-printed counterparts. Digital Image Correlation (DIC) analysis confirmed enhanced crack closure and improved recovery in SMA-reinforced mixtures. SEM analysis confirms enhanced fiber-matrix bonding and denser C–S–H gel formation, while EDS analyse the elemental composition of matrix. Additionally, the finite element model (FEM) validated stress redistribution and interfacial bonding mechanisms, with the calculated values closely aligning with the experimental results. These findings demonstrate that the developed SMA-reinforced 3DP-ECC mixtures offer improved strength, ductility, and self-healing capability, making them promising for use in 3D-printed structural elements requiring high durability and damage resilience.