Flexural Behavior of Reinforced Concrete Beams with Unbonded Repair Patch

The short-term and long-term flexural properties of 18 concrete beams were experimentally investigated with an emphasis placed on the influence of the unbonded interface between repair materials and concrete substrate. These beams were divided into four different series, namely: normally repaired beams, unbonded repaired beams (by using a layer of plastic membrane between new and old concrete), unrepaired beams (with exposed reinforcement), and control beams. The short-term loading test results showed that the ultimate moment capacity of the unbonded repaired beams was slightly lower than that of the control beams. Great decreases in stiffness and ductility were observed in the unbonded repaired beams compared with the reference beams. The long-term loading test results suggested that most of the deflection caused by the unbonded slip between new and old concrete was completed within 1 day after loading.