Experimental Study on Hybrid Fiber–Reinforced Concrete Subjected to Uniaxial Compression

This paper presents the uniaxial compression behavior of steel-polypropylene hybrid fiber–reinforced concrete (HFRC). A total of 30 batches of specimens with different fiber-reinforcement indices in terms of volume fraction and aspect ratio are investigated by the orthogonal experimental method. A variance analysis is conducted to obtain the optimum proportion of hybrid fiber in terms of compressive strength and corresponding peak strain. It is observed from the experimental results that the uniaxial compression behavior of plain concrete can be improved by inclusion of hybrid fibers; it is also noted that the hybrid effect between volume fraction and aspect ratio of steel fiber as well as the volume fraction of polypropylene fiber should be considered as influential factors on uniaxial compressive strength. Furthermore, in comparison to single fiber-reinforced concrete, HFRC exhibits more ductility at postpeak performance. Subsequently, the results are used to develop predictive equations for the strength, deformation, and the complete stress-strain relation of HFRC under uniaxial compression. The developed equations for compressive strength and stress-strain relationship account for the effect of varying fiber volume fractions and aspect ratios; the results obtained by the equations are found in satisfactory agreement with the experimental results. It is believed that the proposed equations can be useful for further analytical investigations and practical engineering simulations.