Bond properties between corroded steel bars and recycled aggregate concrete after high-temperature exposure

Increasingly used reinforced recycled aggregate concrete (RAC) structures may suffer from steel corrosion and high-temperature exposure. The bond behaviors between corroded steel bars and RAC after high-temperature exposure are important in the high-temperature/fire damage assessment of aging RAC structures. In this study, pull -out tests were carried out on specimens of corroded steel and natural aggregate concrete (NAC) or RAC after high-temperature exposure. The specimens were exposed to 20, 100, 200, 300, 400, 500, 600, 700 and 800 degrees C with steel bar in the specimens corroded with corrosion ratios of 0.00 %, 1.05 %, 3.07 %, 5.34 %, 7.50 %. The failure modes, bond -slip curves and bond strength were studied. Effects of corrosion/temperature on bond strength and their difference when using different aggregates (RAC and NAC) were analyzed. The test results indicated that the bond strength of most specimens decreased with increasing high-temperature exposure, and the bond strength degradation of NAC was slightly higher than that of RAC. The bond strength first increased and then decreased as the corrosion ratio increased, and the bond strength of NAC is higher than that of RAC under high corrosion conditions. The failure modes and bond strength also varied with and without stirrups. A bondslip constitutive model of corroded steel bar and RAC without stirrups after high temperature was established introducing temperature and corrosion influence coefficients.