Analysis on mechanical property and pore structure of fiber concrete for spraying use in hot-dry environment

To reveal the improvement mechanism of fiber on shotcrete for spraying in the hot-dry environment at high ground temperature, the basic mix proportion condition, the glass fiber condition, the copper plating microfilament steel fiber condition and the hooked end steel fiber condition were designed. Mechanical property and microscopic pore characteristics of concrete were studied by mechanical property tests and the mercury injection method. The mathematical models of the strength and the pore structure parameters were established. The results show that in the hot-dry environment, the mechanical properties of concrete can be improved after adding fiber materials, and the hooked end steel fiber condition has the best improvement effect. Compared with the basic mix proportion condition, the compressive strengths with the age of 1, 7, 28 d increase by 28.47%, 64.40% and 74.78%, respectively, and the splitting tensile strengths increase by 88.5%, 72.6% and 110.6%, respectively. The addition of fiber materials can effectively reduce the porosity of harmful pores of concrete. The most probable aperture of the fiber addition with the age of 28 d is about 62.5 nm, while the basic mix proportion condition is about 110 nm. The multi-factor strength mathematical model that comprehensively considers the influence of fractal dimension and composite porosity can accurately describe the quantitative relationship between strength and pore structure parameters. © 2022, Editorial Department of Journal of Southeast University. All right reserved.