Cracks caused by steel corrosion ar

Cracks caused by steel corrosion are due to poor concrete quality or insufficient protective layer thickness. The concrete protective layer is corroded and carbonized to the surface of the steel bar by carbon dioxide, which reduces the alkalinity of the concrete around the steel bar, or the chloride ion content around the steel bar is higher due to the intervention of chloride. It can cause damage to the oxide film on the surface of the steel bar. The iron ions in the steel bar react with oxygen and water invaded into the concrete to rust. The volume of the corroded iron hydroxide increases by about 2 to 4 times compared with the original. This will cause expansion stress on the surrounding concrete, resulting in protection The layered concrete is cracked and peeled off, cracks are formed along the longitudinal direction of the steel bar, and there are rust marks on the concrete surface. Due to the corrosion, the effective cross-sectional area of ​​the steel bar is reduced, the bond between the steel bar and the concrete is weakened, the structural bearing capacity is reduced, and other forms of cracks will be induced, which will aggravate the corrosion of the steel bar and cause structural damage. To prevent corrosion of steel bars, the width of cracks should be controlled in accordance with the requirements of the specification, and the thickness of the protective layer should be used in the design (of course, the protective layer should not be too thick, otherwise the effective height of the component will be reduced, and the crack width will be increased when stressed); Control the water-cement ratio of concrete, strengthen vibrating, ensure the compactness of concrete, prevent oxygen intrusion, and strictly control the amount of admixtures containing chloride salts, especially in coastal areas or other areas with strong corrosive air and groundwater.