On post-fire bond strength of steel rebar embedded in thermally-damaged concrete - a review

This study summarizes the state-of-the-art research progress concerning the influence of high-temperature exposure on the residual bond strength of steel rebar. Also, an experimental database from the literature was collected and analyzed for use in fire safety management in concrete design codes and specifications for high important reinforced concrete (RC) structures, such as public health-care buildings, to reduce and mitigate the risk of thermal damages, especially in steel-congested areas. Different vital variables are debated in the present review, including concrete cover-to-rebar diameter ratio, rebar deformation, fiber addition, transverse confinement, aggregate type, concrete water-to-binder ratio, concrete type, cooling regime, thermal loading regime, and heating exposure time. The review shows that high-temperature exposure significantly reduces the residual bond strength. It is concluded that increasing concrete cover, the addition of fibers, considering transverse confinement, using deformed rebar instead of a plain one, using a concrete mixture with a lower value of w/c ratio, and air-cooling regime alleviate the detrimental influence of high-temperature exposure on the residual bond strength. Standing time can significantly recover the bond reduction as a healing period. Additionally, research gaps and the current conflicting results regarding some variables are drawn to be considered for future works.