Effects of Cyclic Freeze–Thaw on the Steel Bar Reinforced New-To-Old Concrete Interface

Frost damage of concrete has significant effects on the safety and durability of concrete structures in cold regions, and the concrete structures after repair and reinforcement are still threatened by cyclic freezing and thawing. In this study, the new-to-old concrete interface was reinforced by steel bar. The shear strength of the new-to-old concrete interface was tested after the new-to-old combination was subjected to cyclic freeze–thaw. The effects of the diameter of the steel bar, the compressive strength of new concrete, the number of freeze–thaw cycles and the freezing temperatures on the shear properties of new-to-old concrete interface were studied. The results showed that, in a certain range, the shear strength of the interface was proportional to the diameter of the steel bar and the strength of the new concrete. Meanwhile, the shear strength of the reinforced interface decreased with the decreasing of the freezing temperature and the increasing of the number of freeze–thaw cycles.