Experimental study of bond performance of corroded reinforcement in concrete under various cooling methods

Corroded reinforced concrete (RC) structures have a bond performance degradation exposed to fire, and fire water spray causes more serious deterioration. To study the bond behavior of corroded RC element under various cooling methods after high temperature, tests were conducted at both microscopic and structural levels. Eccentric pull-out specimens with various corrosion degrees were prepared, and pull-out tests after heating and two cooling methods were conducted. The degradation mechanism of bond strength in specimens following high temperature is analyzed by ultrasonic pulse velocity detection, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Pull-out test results indicate that both high corrosion degree and high temperature have a detrimental effect on bond performance. The bond strength of water-cooled specimens is reduced by approximately 20 % compared to natural-cooled specimens. Because of the severe damage of the mechanical interlocking on bonding interface results from the microcracks induced by high temperature, the bond performance is more sensitive to high temperature than compressive performance. The analysis and regression of experimental data are used to establish a calculation method for bond strength between corroded RC element under two cooling methods. Additionally, a three-stage bond-slip constitutive model under various cooling methods is proposed. The calculation method is applied to predict the bearing capacity of corroded beam after fire, taking into account bond slip. The accuracy and applicability are demonstrated using experimental data from other researchers.