Mode II Fracture Toughness of Hybrid FRCs

Abstract

Mode II fracture toughness (KIIc) of fiber reinforced concrete (FRC) has been widely investigated under various patterns of test specimen geometries. Most of these studies were focused on single type fiber reinforced concrete. There is a lack in such studies for hybrid fiber reinforced concrete. In the current study, an experimental investigation of evaluating mode II fracture toughness (KIIc) of hybrid fiber embedded in high strength concrete matrix has been reported. Three different types of fibers; namely steel (S), glass (G), and polypropylene (PP) fibers were mixed together in four hybridization patterns (S/G), (S/PP), (G/PP), (S/G/PP) with constant cumulative volume fraction (Vf) of 1.5 %. The concrete matrix properties were kept the same for all hybrid FRC patterns. In an attempt to estimate a fairly accepted value of fracture toughness KIIc, four testing geometries and loading types are employed in this investigation. Three different ratios of notch depth to specimen width (a/w) 0.3, 0.4, and 0.5 were implemented in this study. Mode II fracture toughness of concrete KIIc was found to decrease with the increment of a/w ratio for all concretes and test geometries. Mode II fracture toughness KIIc was sensitive to the hybridization patterns of fiber. The (S/PP) hybridization pattern showed higher values than all other patterns, while the (S/G/PP) showed insignificant enhancement on mode II fracture toughness (KIIc). The four point shear test set up reflected the lowest values of mode II fracture toughness KIIc of concrete. The non damage defect concept proved that, double edge notch prism test setup is the most reliable test to measure pure mode II of concrete.