Cohesive Fracture and Fiber Pullout Responses in Normal and SCC Fiber-Reinforced Concrete

The link between the fracture behavior of fiber-reinforced concrete composite and the underlying mechanisms that influence the pullout behavior of fiber are studied. The influence of the fiber-matrix bond on the cohesive stress response in fracture is evaluated for normal vibration compacted concrete (NC) and self-compacting concrete (SCC) matrixes. The fracture response of steel fiber-reinforced SCC (SFSCC) improves significantly when compared with steel fiber-reinforced NC (SFNC). The cohesive stress-crack opening (sigma-w) relationship derived from the measured fracture responses indicates that a significantly higher crack closing stress is generated at smaller crack opening in SFSCC than SFNC. The pullout resistance of the steel fiber embedded in the SCC matrix improves significantly compared with NC. The enhancements in the cohesive debonding and frictional components of resistance contribute to the improved pullout resistance of the steel fiber from SCC. The improvement in the fiber-SCC matrix bond results in increased efficiency of the fibers and produces an increase in stiffness and peak load in the resistance to the pullout of fiber from the SCC matrix when compared with NC. The enhancement in the pullout response of the fibers from SCC contributes to improvements in the cohesive stress mobilized at smaller crack openings in SFSCC. (C) 2021 American Society of Civil Engineers.