Proposals for Enhancing Performance of Repair of Deteriorated Concrete Structures

Repair cases of deteriorated concrete bridges are increasing due to aging and the use of de-icing chemicals. In addition, damage is repeatedly inspected on repaired locations of deteriorated bridges. Types of damage fall into types of shrinkage-induced cracks and delaminations caused by lower bond strength. This study aims at improving performance of repair of deteriorated concrete structures. Therefore, bond strength of repaired concrete bridges in service was evaluated and a comparative study was also conducted on guidelines of concrete repairs among countries. Based on results of field tests and the comparative study, the following conclusions for enhancing performance of repaired concrete structures are drawn: ① Compressive strength of the repair material should be raised to 25 MPa, and the bond strength should be equal to or larger than 1.5 MPa ② The removal area of the deteriorated concrete should expand 150 mm from the delaminations or cracks ③ Concrete substrates should be in a saturated surface-dry (SSD) condition immediately before casting ④ The repair material should be placed in one layer; otherwise, second layer should be placed before setting of former layer or casting second layer on a SSD conditioned former layer ⑤ Repair materials should be wet-cured.