钢筋锈蚀引起的裂缝由于混凝土质量较差或保护层厚度不足，混凝土保护层受二

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.

Cracks caused by corrosion of rebar due to poor quality of concrete or insufficient thickness of the protective layer, concrete protective layer by carbon dioxide erosion carbonized to the surface of the rebar, so that the concrete alkalinity around the rebar is reduced, or due to chloride intervention, the high content of chlorine ions around the rebar, can be Caused the destruction of the oxide film on the surface of the rebar, the iron ions in the rebar and the oxygen and water invading the concrete rust reaction, the rust iron hydroxide volume increased by about 2 to 4 times over the original, thus creating expansion stress on the surrounding concrete. Lead to the protective layer concrete cracking, peeling, along the longitudinal cracks of steel bars, and rust to the concrete surface. As a result of corrosion, the effective section area of rebar is reduced, the grip force of rebar and concrete is weakened, the carrying capacity of the structure is reduced, and other forms of cracks will be induced, which will aggravate the corrosion of rebar, resulting in structural damage. To prevent corrosion of rebar, the design should be in accordance with the specification requirements to control the width of cracks, the use of adequate protective layer thickness (of course, the protective layer can not be too thick, otherwise the effective height of the components reduced, force will increase the width of cracks);

Due to the poor quality of concrete or insufficient thickness of protective layer, the concrete protective layer is eroded and carbonized by carbon dioxide to the surface of reinforcement, which reduces the alkalinity of concrete around the reinforcement, or due to the intervention of chloride, the chloride ion content around the reinforcement is high, which can lead to the destruction of oxidation film on the surface of reinforcement, iron ion and oxygen and water invading into the concrete The volume of iron hydroxide increases about 2-4 times than that of the original, which produces expansion stress on the surrounding concrete, causes cracking and peeling of the concrete in the protective layer, and cracks along the longitudinal direction of the reinforcement, and the rust on the surface of the concrete. Due to corrosion, the effective cross-sectional area of reinforcement is reduced, the bond strength between reinforcement and concrete is weakened, and the bearing capacity of structure is reduced. Other forms of cracks will be induced, which will aggravate the corrosion of reinforcement and lead to structural damage. In order to prevent the corrosion of reinforcement, the crack width should be controlled according to the specification requirements, and the thickness of the protective layer should be sufficient (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 the force is applied); during the construction, the water cement ratio of concrete should be controlled, and the vibration should be strengthened to ensure the compactness of the concrete and prevent the invasion of oxygen, and the chloride containing salt should be strictly controlled The dosage of admixtures is especially cautious in coastal areas or other areas with strong corrosive air and groundwater.<br>