Mechanical performance of high-strength engineering cementitious composites (ECC) with hybriding PE and steel fibers

In this paper, the mechanical performance of high-strength ECC with hybriding steel and PE fibers (HF-ECC) was investigated experimentally; meanwhile, the effects of ultra-fine fly ash and crumb rubber on the properties of HF-ECC were also researched. Based on experimental findings, partial substitution of PE fibers by steel fibers or using ultra-fine fly ash can enhance the compressive strength and tensile modulus of ECC mixtures. For instance, as compared with that of mono PE fiber reinforced ECC (P2.0S0), admixing steel fiber at 1.0% improved the compressive strength and tensile modulus of P1.0S1.0 series ECC by 18.1% and 37.9%, which reached 79.98 MPa and 27.34 GPa, respectively. The compressive strength and tensile modulus of HFR0 series ECC are increased by 9.5% and 10.8% after employing ultra-fine fly ash, reaching 82.11 MPa and 29.41 GPa, respectively. Nevertheless, the incorporation of steel fibers or ultra-fine fly ash had the side effect on ductility of ECC, however, it can be remediated by incorporating crumb rubber, in which the strain capacity can even exceed that of reference one (P2.0S0). Additionally, the utilization of steel fiber or crumb rubber can reduce the material cost of ECC. At micro-scale level, the HF-ECC matrix containing ultra-fine fly ash notably enhanced fracture toughness and friction bond between PE fiber and matrix. Interestingly, the rubberized HF-ECC matrix obtained relatively lower fracture toughness and higher PSH value to that of reference mix.