Fracture Properties of Concrete Reinforced with Steel Fibers

Background: Concrete is a material strong in compression but exhibits low tensile strength, low strain capacity in tension and low cracking & fracture resistance due to presence of defects like voids, cracks, air pockets. Hence to improve fracture resistance of concrete, different types of discrete short fibers are added in concrete at the time of casting. Objectives: To evaluate the various fracture properties such as fracture energy, toughness (K_IC) and Critical Tip Opening Displacements (CTOD_C) of normal strength concrete reinforced with Steel Fiber (SF) (0, 0.25, 0.5, 0.75 & 1% by volume of concrete). Methods: Authors have studied the effect of addition of steel fibers on various fracture properties of concrete. Normal strength concrete was cast by using water to cement ratio as 0.38 and a total of five mixtures were prepared by using steel fibers (0.25, 0.5, 0.75 & 1% by volume of concrete) into those concretes. Notched beam specimen was used to conduct three-point bending test to study fracture properties such as fracture energy, fracture toughness (K_IC) and CTOD_C of different concrete mixes. Findings: Test results showed an improvement in tensile strength and fracture properties of steel fiber reinforced concrete mixes when compared with control mix. Fracture energy was enhanced by 243 % & 208 % with addition of 0.75% and 1% steel fibers. Fracture toughness was also enhanced by 95% & 94 % with addition of 0.75% and 1% steel fibers. However inclusion of steel fibers resulted in reduction in the workability of concrete mixture with increasing fiber contents. Novelty/Improvements: For the novel material containing steel fibers, fracture properties of concrete are enhanced to a great extent and thus brittle and sudden failure of concrete can be avoided and material undergoes a more ductile failure which in turn improves the performance of structure in terms of durability and serviceability.