Fracture Behavior of Steel Fiber Reinforced Geopolymer and Normal Concrete

The study aims to enhance the ductility of Geopolymer Concrete (GPC) with the inclusion of hooked-end steel fibers. The influence of the fiber-matrix bond on the cohesive stress response in the fracture is evaluated for GPC and Normal Concrete (NC) matrixes. The fracture responses of GPC and NC with 25 kg/m³ hooked-ended steel fibers are evaluated experimentally. The pullout behavior of the steel fiber from the geopolymer and cementitious matrices is also determined experimentally. The fracture response of steel fiber-reinforced GPC is improved significantly when compared with steel fiber-reinforced NC, with a low dosage of fibers. The cohesive stress-crack opening relationship derived from the measured fracture responses indicates that a significantly higher crack closing stress is generated at smaller crack openings in GPC than in NC. The pullout resistance of the steel fiber embedded in the GPC matrix is significantly higher compared with NC. The improved bond between the GPC matrix and fiber contributes to higher debonding resistance in the early part of the fiber pullout. The higher peak pullout load resistance at low slip indicates better engagement of the fiber in providing crack closing stresses across a crack. The higher efficiency of the steel fiber in providing crack opening resistance contributes to significant improvement in the cohesive stress at small crack openings in GPC.