Fatigue fracture characteristics of normal concrete and high ductility geopolymer bonding based on DIC technique

This study reveals the adhesive fatigue behavior of normal concrete (NC)–high-ductility geopolymer (HDG) interfaces. A digital image correlation (DIC) technique was employed to capture the fracture characteristics. The fatigue stress level (β) and interfacial inclination angle (α) are the variables used in this research. The failure mode of the NC–HDG bonding interface was affected by α, and gradually transformed from compression crushing to debonding. The HDG matrix ultimately remained relatively intact compared to NC owing to the bridging effect of the polyvinyl-alcohol (PVA) fibers. The NC–HDG bonding interfaces experience three-phase fracture development: crack initiation phase, stable crack propagation phase, and final rapid crack propagation phase. At the earlier 15%∼40% of the fatigue life, the microcrack was initiated rather than propagated. The stable crack propagation phase presented a stabilized fracture propagation rate for most of the fatigue life. The cracks finally propagated rapidly until failure. A high fatigue stress accelerates damage accumulation and causes a greater degree of damage. Moreover, through inspection, the fatigue life of the NC–HDG interfaces was proven to abide by the Weibull distribution. The existing fatigue model was adopted to predict the fatigue life of an NC–HDG interface under a preset fatigue stress level and reliability.