A study on achieving high tensile ductility in 3D-Printable engineered cementitious composites reinforced with 8 mm fibers

Abstract

This paper delves into the design and formulation of 3D printable Engineered Cementitious Composites (ECC) mixes, featuring 8 mm 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 8 mm 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.