Changes in fractal dimension and durability of ultra-high performance concrete (UHPC) with silica fume content

The combined utilization of silica fume (SF) and steel fiber in UHPC is an inevitable trend to improve its mechanical properties and durability. In this study, the influence of SF dosage on mechanical property, permeability, drying shrinkage as well as the pore structure and fractal dimension (D-s) of UHPC was investigated. Finally, the relationships between the durability of UHPC and the porosity as well as the D-s were revealed and discussed. The results demonstrate that the synergistic effect of SF and fiber increased mechanical properties of UHPC due to the friction and mechanical interlocking of the steel fiber to the fiber-matrix and the adhesion between fiber and paste provided by the silica fume. In addition, incorporating 20% enhanced the mechanical property, decreased the chloride diffusion coefficient, and increased the D-s value. Moreover, increasing D-s value linearly raised compressive strength and drying shrinkage but nonlinearly depressed permeability in UHPC, so D-s can be served as a navel parameter to characterize the permeability and drying shrinkage of UHPC.

Automated summary

The combined utilization of silica fume and steel fiber in UHPC can improve its mechanical properties and durability. The study investigates the influence of silica fume dosage on the properties of UHPC and reveals the relationships between durability, porosity, and fractal dimension.