Micropore structure controlling: A strategy toward superior tensile properties in high strength engineering cementitious composites

High strength engineering cementitious composites (HSECC) exhibit excellent mechanical properties and ductility, making them highly effective in enhancing structural safety. However, significant fluctuations exist in the tensile properties of HSECC with identical compositions because of the chaotic micropores. The paper optimizes the tensile performance of HSECC by classifying the plastic viscosity of fresh cement paste into five ranges to control its pore microstructure. The results showed that appropriate plastic viscosity could effectively regulate micropore structure, quantity, and distribution. Specifically, increased plastic viscosity prevented bubble escape, resulting in uniform micropore structure distribution within the material. By adjusting the plastic viscosity of the slurry, the micropore size and distribution capable of forming saturated multi-cracks were obtained, which promoted the dispersion and bonding of fibers, thereby significantly improving the tensile properties of HSECC. When the plastic viscosity was between 11 - 15 Pa·s, HSECC achieved peak performance metrics: initial cracking strength of 4.87 MPa, ultimate tensile strength of 8.30 MPa, tensile strain of 10.24%, and energy absorption of 710.5 kJ/m 3 . X-CT testing confirmed that the modified micropore structure efficiently guided crack propagation, markedly enhancing the composite’s overall mechanical characteristics, solving the problem of inconsistent tensile properties. • This study proposes a novel strategy to enhance the tensile performance of high-strength engineering cementitious composites by regulating the plastic viscosity of the cementitious paste, thereby optimizing the micropore structure of the matrix. • The optimized micropore structure, in terms of both size and distribution, facilitates saturated multiple cracking, leading to improved ductility and increased crack density in the matrix.