Main causes of cracking of concrete members

1.Load

It includes self weight, vehicle load, crowd load, construction load, wind load, seismic load, water pressure, ice pressure, water buoyancy, soil pressure, and prestress.

2.Deformation

They include shrinkage, creep, hydration heat, environmental temperature changes, forced displacement (such as foundation or support displacement). The restraining effect and supporting friction effect between different parts of the same component.

According to the investigation data, the cause of structure cracking in engineering practice is about 80% of the cracks caused by “deformation” or cracks caused by “deformation” as the main factor, and about 20% of the cracks caused by the “load” factors.

Necessity of crack repair

In reinforced concrete structures, the strain of tension steel always exceeds the ultimate tensile strain of concrete, and cracks are inevitable. According to the durability requirements, when the width of the crack is less than 0.2mm, the steel bars are generally not corroded. Even if the cracks reach or slightly exceed the allowable value (0.2mm), the strength of the beams will not have obvious influence. When the cracks are large and the width is large, the stiffness of the beams will be reduced, and the reinforcement is eroded by harmful medium. Reinforcement must be carried out at this time, otherwise the service life of the bridge will be affected.

Method of crack repair

The usual methods for repairing cracks are crack repair, structural crack injection, externally bonded steel plate, externally bonded CFRP wrap, Pre-stressed FRP plate.