Bond Behavior of Alkali-Activated Concrete with Steel and FRP Reinforcement

This paper expands upon previous research on the development and characterization of an eco-friendly, high-workability, shrinkage-compensating alkali-activated slag-based concrete designed for repairing and strengthening rein-forced concrete (RC) structures. In this study, the focus is on understanding the bond behavior at the interface between the developed concrete and both steel and ribbed glass fiber-reinforced polymer (GFRP) rebars. Following the preliminary evaluation of the mixture’s properties in both fresh and hardened states, the investigation focuses on the influence of key parameters affecting the stress transfer mechanism, such as rebar diameter, bonded length, and surface characteristics for FRP bars. A comprehensive experimental campaign was conducted, including 50 pull-out tests performed with different types of reinforcement bars. To enhance the understanding of bond behavior, this study introduces tests with a reduced bonded length (2.5 times the bar diameter). The findings reveal a substantial reduction in ultimate bond load for both steel and ribbed GFRP rebars in specimens with the shortened bonded length, with the peak bond strength observed to be nearly halved compared to standard specimens.