In order to be able to perform non-linear analysis and design of structures made of fiber-reinforced concrete members, the knowledge of their stress–strain behaviour under axial compression is required. In this study, an extensive experimental programme was conducted to investigate the compressive stress–strain behaviour of synthetic fiber-reinforced highstrength concrete. To accomplish this, 22 mixtures including different percentages of macropolymeric fibers and polypropylene fibers as well as different hybridisations of the two fiber types with or without the presence of nano-silica and silica fume pozzolans were prepared. Then, the effect of adding fibers and pozzolans on the properties of fiber-reinforced highstrength concrete including the shape of the stress–strain curve, compressive strength, strain at peak stress, ultimate strain and toughness index was investigated. Furthermore, based on the obtained experimental results, empirical relationships were proposed for the relevant parameters of the stress–strain curve of synthetic fiber-reinforced concrete. Finally, two simple yet accurate models were proposed to predict the compressive stress– strain curve of synthetic fiber-reinforced concrete based on the empirical relationships proposed for the maximum stress and the corresponding strain. The results suggest that the presented models are capable of predicting the experimental results with a very good accuracy.
