Assessment and restoration of bond strength of heat-damaged reinforced concrete elements

Abstract

This investigation focuses on the assessment of the residual (after cooling) bond strength between concrete and steel rebars of reinforced concrete elements after exposure to elevated temperature and how to restore the bond strength using different repairing techniques and materials. The bond test was carried out on twenty-four beam end test specimens. The test parameters considered in the current research are the exposure condition, concrete compressive strength, rebar type, rebar size, rebar location, repairing techniques, and repairing materials. The test results indicated a significant reduction in the residual bond strength for heat-damaged specimens with a dramatic change in the bond stress-slip behavior. The deep repair technique is more efficient than the shallow repair technique in restoring a large portion of the original bond strength for heat-damaged specimens. Among the different repair materials used in the current research, the commercially fiber reinforced mortar is the most efficient one. Based on the limited number of specimens considered in this study, simple relationships are proposed to predict the bond strength and characterize the bond stress-slip behavior. The proposed relationships yield good agreement with the experimental results.