Axisymmetric fiber orientation distribution of short straight fiber in fiber-reinforced concrete

The anisotropic orientation distribution of short fibers in fiberreinforced concrete and the impact on mechanical properties have been established in past research. In this paper, the cast-flow induced anisotropic fiber distribution was categorized as axisymmetric with respect to the cement paste flow direction. The probabilistic spatial orientation for fibers is introduced using the beta distribution and uniformity parameters. Either theoretical or approximate equations for the orientation factor and the probability density function of the crossing angle were derived for any arbitrary cut planes. The derived orientation factor equation can be used to quantify the degree of anisotropy via image analysis. This process is easier and more accurate because instead of detailed orientation information for every single fiber, only total fiber counts on the cut sections are needed. The probabilistic macro-mechanical properties, such as ultimate tensile strength, are estimated based on the selected micromechanical model that defines the single fiber-matrix interactions.