One of the effective ways to prevent the brittle behavior of high-strength concrete is to use fibers. Therefore knowing the stress strain behavior of high-strength fiber-reinforced concrete is essential for nonlinear analysis and design purposes. In order to investigate the compressive stress-strain behavior of concrete reinforced with Forta-Ferro and steel fibers with and without the inclusion of silica-fume and nanosilica pozzolans, this paper experimentally investigates the effect of fibers and pozzolans on the mechanical properties of fiber-reinforced high-strength concrete including compressive strength, strain at peak stress, ultimate strain, and toughness index. Based on the experimental results, empirical equations are proposed for the compressive stress-strain parameters affecting the behavior of fiber-reinforced concrete. Finally, to predict the stress-strain relationship of high-strength fiber-reinforced concrete, two different models are presented which are capable of properly predicting the experimental curves. Because using silica fume and nanosilica leads to a change in the gradient of the stress-strain curve of fiber-reinforced concrete, the necessity of modifying the proposed models in order to improve accuracy is explored.
