A Study on Achieving High Tensile Ductility in 3D-Printable Engineered Cementitious Composites Reinforced with 8mm Fibers (2025-02)¶

This paper delves into the design and formulation of 3D printable Engineered Cementitious Composites (ECC) mixes, featuring 8mm fibers, to tackle challenges like nozzle blockage and improve print quality. It explores the mechanical performance of four ECC mixes—S50, FA50, FA40-MK10, and FA40-SF10—by replacing 50% of cement with mineral admixtures such as slag (S), fly ash (FA), metakaolin (MK), and silica fume (SF), specifically tailored for mold-cast and extrusion-based 3D printing. PolyVinyl Alcohol (PVA) and Ultra-High Molecular Weight Polyethylene (PE) fibers were incorporated at different ratios (1.5% and 2%). Comprehensive mechanical testing, including compressive, direct tensile, and three-point bending tests, was conducted, considering various parameters' influence, such as different admixtures, fiber types and volumes. The S50 mix demonstrated superior strength and ductility, with 2% PVA and 2% PE fibers displaying significantly larger strain capacities than FA50 mixes. Substituting 10% of FA with MK improved mechanical performance, while SF substitution reduced strength and bending capacity. Ultra-ductile ECC with 8mm PE fibers, printed with high quality, achieved a strain capacity of up to 11.9% and a tensile strength of 5.85 MPa, with optimized mixing procedures and viscosity modifier admixture. Analysis of SEM images revealed that ECC mixes with 2% PE fibers predominantly exhibited pullout failures, whereas those containing 2% PVA fibers displayed rupture failures. These findings expand possibilities for developing high-quality 3D printable ECC with both high compressive strength and ductility, offering insights for advancing sustainable and resilient construction materials.