Abstract：
After completion of the main structure construction of an office building, a great number of cracks are generated along the steel bar laying direction on concrete components on floors 7 to 9. Inspection and verification results show that main reasons causing these cracks are excessive content of chloride ion in concrete, which causes rust and expansion of steel bars. Many repair measures are adopted, such as removing concrete at places where crack is serious, derusting steel bars, coating interface binder and repouring concrete, etc. At places where the crack is slight, penetrating steel bar rusty retardant agent is coated outside, cracks on component surface are repaired and 30mm thick polymer mortar is plastered on the lateral surface. Since completion of the repair construction, no new crack is generated on concrete components.
