Impact of fire exposure on the rebar-concrete bond strength

Structural fire resistance is a primary aspect of a passive fire engineering design measure that allows a structure to withstand intense fires.Generally, concrete structural elements perform well under these conditions due to their non-flammable nature.However, fire incidents require a deeper understanding of concrete behavior and structural mechanics to improve fire design.Structural elements exposed to fire and heat show reduced strength; this reduction must be evaluated to determine whether to demolish or repair a building based on its condition and capability to support future loads.Evaluating the post-fire strength characteristics, including compressive, tensile, and bond strengths, is essential for determining the structure's safety.Prolonged exposure to high temperatures can degrade concrete properties, particularly the bond strength between rebar and concrete.This paper investigates the bond strength of materials after exposure to fire.The study explores the effects of temperatures ranging from 20 C to 500 C, following the ISO 834 fire curve, on compressive, tensile, and bond strengths.Cylindrical pull-out specimens were heated to specific temperatures and held for 2 hours.Afterward, they were cooled for one day before testing.The results indicate that bond strength decreases by approximately 72% at 500 C, about twice the reduction observed in compressive and tensile strengths.