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2023

The concrete always cracks, and the main culprit is them!

Concrete cracking is a very headache problem in construction engineering. The common causes of cracking are as follows: 1、 Unauthorized change of water-cement ratio during construction During the construction of pumping concrete, in order to facilitate the construction, water is added without authorization to improve the fluidity of concrete, or the water-cement ratio is increased due to other reasons, resulting in the increase of shrinkage when the concrete is hardened, and the structure has network or irregular cracks of different length. 2、 The concrete mixing and transportation time is too long If the concrete is mixed and transported for a long time, the water will evaporate too much, resulting in low slump of concrete and irregular shrinkage cracks. 3、 Formwork operation is not standardized The rigidity of the formwork is insufficient. When pouring concrete, due to the effect of lateral pressure, the formwork is deformed, resulting in cracks consistent with the deformation of the formwork. The formwork is removed too early during construction, and the concrete strength is insufficient, which causes cracks in the components under the action of dead weight or construction load. The formwork support is not compacted enough or the support stiffness is insufficient, and the support will not sink evenly after pouring concrete, resulting in cracks in the concrete. The formwork is not sprayed with enough water before pouring and is too dry. After pouring, due to the large water absorption of the formwork, the concrete shrinkage and plastic shrinkage cracks are caused. 4、 Unreasonable construction process and disordered management The construction machinery and materials shall be stacked without restriction during the construction; Do not understand the stress characteristics of the prefabricated structure, and turn over, lift, transport and install at will; Do not construct according to the design drawings, arbitrarily change the structural construction sequence and change the structural stress mode; These behaviors will produce cracks. Tread on the bound upper reinforcement randomly, and the reinforcement is bent and stepped down, which thickens the protective layer of the load-bearing reinforcement bearing the negative bending moment, resulting in the reduction of the effective height of the component, the reduction of the bearing capacity, and the formation of cracks perpendicular to the load-bearing reinforcement.

Concrete cracking is a very headache problem in construction engineering. The common causes of cracking are as follows:
1、 Unauthorized change of water-cement ratio during construction
During the construction of pumping concrete, in order to facilitate the construction, water is added without authorization to improve the fluidity of concrete, or the water-cement ratio is increased due to other reasons, resulting in the increase of shrinkage when the concrete is hardened, and the structure has network or irregular cracks of different length.
2、 The concrete mixing and transportation time is too long
If the concrete is mixed and transported for a long time, the water will evaporate too much, resulting in low slump of concrete and irregular shrinkage cracks.
3、 Formwork operation is not standardized
The rigidity of the formwork is insufficient. When pouring concrete, due to the effect of lateral pressure, the formwork is deformed, resulting in cracks consistent with the deformation of the formwork. The formwork is removed too early during construction, and the concrete strength is insufficient, which causes cracks in the components under the action of dead weight or construction load. The formwork support is not compacted enough or the support stiffness is insufficient, and the support will not sink evenly after pouring concrete, resulting in cracks in the concrete. The formwork is not sprayed with enough water before pouring and is too dry. After pouring, due to the large water absorption of the formwork, the concrete shrinkage and plastic shrinkage cracks are caused.
4、 Unreasonable construction process and disordered management
The construction machinery and materials shall be stacked without restriction during the construction; Do not understand the stress characteristics of the prefabricated structure, and turn over, lift, transport and install at will; Do not construct according to the design drawings, arbitrarily change the structural construction sequence and change the structural stress mode; These behaviors will produce cracks. Tread on the bound upper reinforcement randomly, and the reinforcement is bent and stepped down, which thickens the protective layer of the load-bearing reinforcement bearing the negative bending moment, resulting in the reduction of the effective height of the component, the reduction of the bearing capacity, and the formation of cracks perpendicular to the load-bearing reinforcement.

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