Tensile behavior of ultra‐high performance concrete reinforced with different hybrid fibers

Abstract Seventy eight dog‐bone shaped ultra‐high performance concrete (UHPC) tensile specimens were designed to study the effects of single steel fiber and hybrid steel fiber with polyolefin (PP) fiber, polyvinyl alcohol (PVA) fiber, glass fiber (GF), polyester (PET) fiber, and basalt fiber (BF) on the compressive strength, tensile strength, peak strain, and fracture energy of UHPC. The results showed that hybrid fiber reinforced UHPC had good toughness damage characteristics, which reflected the strengthening and toughening effects of different fibers. The tensile stress–strain curves of hybrid fiber reinforced UHPC could be divided into the rising section and softening section, and the softening section was significantly influenced by the type and volume content of fibers. Among the microfiber (PVA fiber, GF, and BF), GF had the most significant strengthening effect, PVA fiber had the best ability to improve the deformation of UHPC, and BF had the most significant effect on the improvement of fracture energy. Among macrofiber (PP fiber, PET fiber), PP fiber had a better ability to improve UHPC deformation than PET fiber, but both were lower than microfiber. When the total volume content of steel fiber and PVA fiber was 2.5%, the best toughening and crack resistance effect was achieved when the volume content of steel fiber was 1.5% and the volume content of PVA fiber was 1.0%. Combined with the experimental results, the UHPC tensile σ–ω curves of single steel fibers, hybrid steel–PVA fibers, and hybrid steel–PVA–PET fibers were established, and the predicted curves were in good agreement with the experimental curves.