Tensile and fracture behavior of engineered cementitious composite with polyethylene fibers and calcium sulfate whiskers

The scale of fibers in cementitious composites spans from macro to micro levels. Hybrid fibers at different scales can fully leverage the properties of each fiber type, showcasing synergy across multiple scales. This paper studies multi-scale enhancement in ECCs with polyethylene (PE) fibers and calcium sulfate whiskers (CSWs). The impact of CSWs content and types on ECCs' tensile and fracture behavior were mainly investigated. CSWs significantly improved the mechanical properties of ECC, including compressive strength, flexural strength, fracture energy, and fracture toughness, which reached 70.5 MPa, 23.4 MPa, 18.58 kN/m, and 14.46 MPa·m^0.5, respectively. Excessive whisker contents may cause CSWs agglomeration, compromising CSWs' enhancement effects. S- and M-type whiskers enhanced ECC optimally at 2 %, while L-type whiskers were optimal at 1 %. ECC with 2 % M-type CSWs exhibited an unstable fracture toughness 2.14 times greater than the control group. The multi-scale fracture resistance mechanism of PE fibers and CSWs was elucidated through strain and displacement field analysis. Further, the microscopic morphology observations revealed that PE fibers and CSWs displayed bridging effects at multiple scales, delaying microcrack formation and preventing macroscopic crack development in ECC. This study proposes a novel multi-scale fiber design to enhance and toughen cementitious composites. • Incorporating CSWs into ECC improved the flexural strength and fracture toughness by 1.6 and 2.1 times, respectively. • S- and M-type CSWs enhanced ECC optimally at 2 %, while L-type whiskers were optimal at 1 %. • CSWs and PE fibers exhibited synergistic fracture resistance effects at multiple scales. • CSWs could fill voids and optimize the substrate microstructure but may encounter issues with aggregation.