1. Cracks caused by load are divided into
direct stress and secondary stress cracks, which mostly occur in the tensile zone, shear zone or parts with severe vibration. 2
. Cracks caused by temperature are caused by concrete deformation due to
environmental or internal temperature changes. If the deformation is restrained, stress will occur in the structure, and when the stress exceeds the tensile strength of concrete, temperature cracks
will occur. 3. Cracks
caused by shrinkage include plastic, shrinkage, autogenous and carbonization shrinkage, mostly surface cracks and crisscross cracks. During construction, it is necessary to control the water-cement ratio to reduce shrinkage
. 4. The cracks
caused by the deformation of the foundation are caused by the vertical uneven settlement or horizontal displacement of the foundation. Exceeding the tensile capacity of concrete leads to structural cracking
. 5. Cracks
caused by corrosion of steel bars are caused by poor quality of concrete or insufficient protective layer, and cracks are caused by volume expansion of rusted objects. It is necessary to prevent and control
cracks by controlling the width of cracks. 6. When the temperature of cracks
caused by frost heave is below zero, the concrete saturated with water will freeze and cause volume expansion; At the same time, the migration of supercooled water causes osmotic pressure, which leads to the reduction of concrete strength and cracks
. 7. The quality of
cement, sand, aggregate and other materials used in concrete configuration is not up to standard. Cracks
may occur in the concrete structure. 8. Cracks
caused by the quality of construction technology. Concrete pouring, stripping, transportation and other links are unreasonable and the construction quality is poor, which can easily lead to cracks in various directions in the structure, especially
in slender thin-walled structures.
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