Degradation model of bond performance between deteriorated concrete and corroded deformed steel bars

• Bond behaviour between the deteriorated concrete and corroded deformed steel bars are studied.
• The specimen failure mode is mainly splitting failure, but the mark of steel bars became unclear gradually.
• The relative thickness of protective concrete has great effect on the ultimate bond strength.
• Estimation model of bond strength between deteriorated concrete and corroded deformed steel bar was established.

An experimental investigation was conducted to explore the degradation model of bond stress between concrete and deformed steel bars with four different diameters (12, 16, 20 and 25 mm) to determine the coupling effects on the bond between deteriorated concrete and corroded steel bars. The results indicated that the failure mode of the specimens was primarily splitting failure; however, the marks of the steel bars at the interface between the deteriorated concrete and corroded steel bars became unclear as the corrosion ratio increased. The ultimate bond strength of the two specimens with the smaller diameters increased with deterioration before a crack appeared and then it decreased, whereas that of the two specimens with the larger diameters continuously decreased due to smaller protective concrete thickness. A simplified calculation model of the bond strength between the cracked concrete and heavily corroded deformed steel bars was established based on the bonding theory of concrete and plane steel bars suing the following factors: the corrosion ratio of the steel bars, the compressive strength of concrete, the width of the cracks in the concrete and the friction factor between the deteriorated concrete and corroded steel bars.