Review of bond strength coefficient (k) between FRP bars and concrete

Reinforced concrete structures have traditionally employed steel bars for reinforcement. Nonetheless, durability related issues such as corrosion have led to a shift toward fiber-reinforced polymer (FRP) bars, particularly in structures highly susceptible to weathering. Challenges in replacing steel with FRP bars are mainly focused on absence of yield phase, lower modulus, cost and understanding the bond mechanism with concrete. The current work examines the adhesive interaction between FRP bars and concrete, placing specific emphasis on the bond-dependent coefficient, kb. Despite the recent surge in research addressing the FRP-concrete bond, there has been a notable gap in comprehensive reviews on kb. Through extensive examination of existing literature and experimental findings, this research reveals that numerous factors, including concrete properties, FRP bar characteristics, and geometric parameters, considerably influence the determination of kb value. Statistical assessments underscored the effects of parameters like concrete compressive strength and beam width on kb. Notably, variations in experimental setups, particularly in the number of FRP bars used, can introduce discrepancies in the reported kb values. The study culminates in emphasizing the need for adoption of standard testing methodology and a deeper exploration of the effects of combined parameters on kb, providing valuable insights for future research and construction practices.