Mechanical properties of hybrid fiber reinforced concrete

Abstract

The research reported herein studied the effect of adding Fibrillated Polypropylene (FPP), Glass Fiber (GF), and Carbon Fiber (CF) at relatively low volume fractions on the fresh and hardened properties of concrete. The research was also concerned with optimizing the combined use of two different fiber types in cementitious matrix. Two series of hybrid Fiber Reinforced Concrete (FRC) were examined. The first series contained FPP and GF, and the second series contained FPP and CF, with a volume fraction ranging between 0.1 and 0.5%. Hydrating characteristics were evaluated through the compressive strength, modulus of elasticity, splitting tensile, strength, impact strength, drying shrinkage, modulus of rupture, and toughness indices. The inclusion of low-modulus fiber (FPP) in concrete led to a considerable improvement in toughness, and impact strength. Meanwhile, the high modulus fibers (i.e., GF and CF) led to a considerable improvement in modulus of rupture, and splitting tensile strength. Results revealed the effectiveness of adding FPP on improving the toughness, and impact strength of carbon and glass FRC, which are characterized by their improved strength properties. The fractured surface of FRC specimens was also examined through Scanning Electron Microscope, in order to assess the failure mechanism of different types of fiber.