What are the causes of cracks in concrete? What are the reasons for cracks in concrete??

The construction of the decoration workers is not standardized, and the ratio of cement mortar to water is not well adjusted.

Under the influence of the external environment, the temperature should not be too low, try to be above 0, and pour water directly on the concrete to ensure humidity.

If there is a problem with the quality of the raw materials, do not buy the cement if it is agglomerated or damp.

Ground settlement can also cause cracks in concrete. When pouring a large volume of concrete, the heat of hydration generated inside it will increase the temperature of the concrete, and the resulting deformation may be constrained by the existing structure or formwork, resulting in restraint stress. After the concrete is poured, the rise in temperature will cause the concrete to expand and deform.

1.Cracks caused by cement shrinkage. This crack appears on the surface of the concrete and is relatively small. Cement is a hydraulic material with dry shrinkage, and cracks may occur if there is not enough water due to improper maintenance in the early stage of hardening.

2.The temperature difference changes, by thermal expansion and cold contraction.

effect caused by cracks. This kind of crack generally appears in an environment with a large temperature difference and a large area or length, and there is no expansion joint in the appropriate part.

on the component or structure.

3.Stress concentration.

caused by cracks. This kind of crack generally appears at the yin and yang corners of the concrete slab or at the support. It is caused by insufficient reinforcement of negative moment reinforcement on the plate surface or excessive spacing of thick reinforcement.

4.Cracks caused by overload and excessive deformation caused by improper use. This type of crack usually occurs in the tension zone of the concrete flexural member.

5.Cracks caused by tensile force. in prestress.

In the tensioning process of reinforced concrete components, if they are not well controlled, cracks may be caused. This type of crack usually occurs at the end of the prestressed member or at the corner of the upper surface of the slab.

6.Cracks caused by uneven settlement. Due to the uneven settlement of the foundation, the foundation or ring beam.

Cracks occur due to excessive tension of girders and other components.

7.During construction, cracks will occur in the structure due to the vibration, deformation or displacement of the formwork in the initial setting stage of concrete.

8.Cracks created prematurely by loading. During construction, due to the early removal of the formwork, the concrete strength did not meet the design requirements and the load was added in advance, which caused the components to be overloaded and cracks appeared.

9.construction joints.

If the treatment is not good, cracks may appear in the construction joints.

10.In the process of demoulding, transportation, stacking and lifting, the compression area of the component is in a tensile state due to various reasons, which may cause cracks in the component.

Cracks in concrete may be caused by the inappropriate choice of cement, resulting in excessive shrinkage of concrete. It is also possible that the later maintenance is not in place, and the temperature difference between the inside and the surface of the concrete exceeds the specified range, resulting in concrete cracking.

1. Structural design issues. Cracking due to uneven settlement of the foundation; Structural design defects, local uneven force occurs.

2. After the concrete is poured, the curing is not timely, which causes surface cracking. This problem is common, but generally does not affect security.

3. When the mold is removed too early, it will cause cracking due to premature stress on the incompletely solidified concrete.

4. There is a problem with the concrete mix ratio, and the strength cannot reach the design strength, which causes the safety problem of stress.

5. The amount of cement is too much (it is also a mix ratio problem), when the concrete begins to solidify, the surface cracking is caused by excessive hydration heat and difficult to control the curing.

6. When the concrete floor slab is over-dried and calendered, the cement slurry layer with high water content will appear on the surface of the floor slab, and it will react chemically with the air, resulting in cracks in the concrete floor slab.

Four common causes of cracks in concrete building structures.

(1) Concrete is a man-made mixed material, and an important sign of its failure is the uniformity and compactness of the concrete after molding. Therefore, any defects and omissions in the mixing, transportation, pouring and compaction processes of concrete may be the direct or indirect cause of cracks.

2) Improper formwork structure, water leakage, slurry leakage, insufficient support stiffness, subsidence of the supported foundation, premature removal of the formwork, etc. may cause concrete cracking. During the construction process, the surface pollution of the steel bar, the concrete guarantee layer is too small or too large, and the collision of the steel bar during pouring may cause cracks.

3) Concrete curing, especially the early curing quality and cracks are closely related, if the concrete curing is improper, the early surface is dry or the early internal and external temperature is larger, and cracks are more likely to occur.

4) In reinforced concrete structures, the main reason for cracking is uneven settlement. The size, shape and direction of the crack are determined by the deformation of the foundation, and the stress caused by the deformation of the foundation is relatively large, so that the crack is generally penetrating.

5) Concrete has the property of thermal expansion and cold contraction, and its linear expansion coefficient is generally 1 10-5 0cWhen the ambient temperature changes, temperature deformation will occur, resulting in additional stress, and when this stress exceeds the tensile strength of the concrete, cracks will occur.

(1) Shrinkage of concrete. Shrinkage is one of the main characteristics of concrete, which has a great impact on the performance of concrete. Microscopic cracks caused by shrinkage may cause cracking, deformation and even destruction of the mechanism once they develop.

2) Temperature stress. The cement in the concrete emits a lot of heat in the hydration reaction, which heats up the concrete and forms a certain temperature difference with the external air temperature, resulting in temperature stress. Its size is related to the temperature difference, and directly affects the cracking and crack width of the concrete.

3) Insufficient reinforcement. The concrete structure with large reinforcement spacing and small reinforcement ratio has more cracks, and the unreinforced concrete has more cracks than the reinforced concrete. The position of the reinforcement should be correct, and the protective layer that is too large or too small may lead to concrete cracking.

4) Concrete material and mix ratio. Improper mix design directly affects the tensile strength of concrete, which is the cause of concrete cracking that cannot be ignored. Improper mix ratio refers to excessive cement dosage, large water-cement ratio, improper sand content, poor aggregate type, improper selection of admixtures, etc., which are interrelated.

5) Conservation conditions. Curing is an important means to harden concrete normally. Curing conditions have a key impact on the appearance of cracks.

Under standard curing conditions, the concrete hardening is normal and will not crack, but it is only suitable for the production of test blocks or prefabricated parts in the factory, and it is impossible to have such conditions in on-site construction. The closer the on-site concrete curing is to the standard conditions, the less likely the concrete is to crack.

6) Construction quality. In the concrete pouring construction, uneven vibration, or leakage vibration, over-vibration, etc., will cause concrete segregation, poor compactness, and reduce the overall strength of the structure. When the bubbles inside the concrete can not be completely eliminated, the bubbles on the surface of the steel bar will reduce the adhesion between the concrete and the steel bar.

If the rebar is subjected to too much vibration, the cement slurry will be dense around the rebar, which will also greatly reduce the cohesion.

The floor concrete has almost been poured, and some concrete has been cracked, what is going on?

Excessive water-cement ratio and improper maintenance are the most common causes.

Four common causes of cracks in concrete building structures.

1. The construction of decoration workers is not standardized.

Construction technical problems, to a large extent determines whether the concrete is cracked, if the decoration workers do not debug the ratio of cement mortar and water, it will lead to concrete cracking in the later construction.

As for the correct ratio of cement to water, it is about 1:, that is, 1kg of cement should be mixed with 400g of water.

2. The influence of the external environment.

If you want the concrete to solidify, the temperature and humidity must meet certain requirements, the temperature should not be too low, try to be above 0, and pour water directly on the concrete to ensure humidity. Especially in summer, you need to sprinkle water 5 times a day, every 2 hours.

Because concrete releases heat as it sets, it needs to be watered to maintain temperature and humidity, otherwise it will crack.

3. There is a problem with the quality of raw materials.

Good cement must have information such as production date, production license, product factory inspection report, etc., if you don't have it, don't buy it. Do not buy the cement if it is agglomerated or damp, as this will reduce the strength and eventually crack.

4. Foundation settlement.

Concrete cracking caused by foundation settlement is rare, but it is not impossible, so before building a house, you must tamp the foundation to prevent it from having voids to settle, and severe settlement will even lead to the collapse of the house.

Hello dear! We'll be happy to answer for you. What are the causes of cracks in concreteAnswer:

Hello dear dear, the cracks caused by the load in the concrete under the conventional static, dynamic load and secondary stress are called load cracks, which can be summarized into two main types: direct stress cracks and secondary stress cracks. Direct stress cracks refer to cracks caused by direct stress caused by external loads, and secondary stress cracks refer to cracks caused by secondary stress caused by external loads. The characteristics of load cracks vary according to different loads, and present different characteristics.

This type of crack mostly appears in the tension zone, shear zone or severe vibration area. However, it must be pointed out that if there is peeling or short cracks along the compression direction in the compression zone, it is often a sign that the structure has reached the limit of bearing capacity and is a precursor to structural failure, and the reason is often that the cross-sectional size is too small. 2. Cracks caused by shrinkage concrete has the properties of thermal expansion and cold contraction, when the external environment or the internal temperature of the structure changes, the concrete will be deformed, if the deformation is constrained, the stress will be generated in the structure, and when the stress exceeds the tensile strength of the concrete, temperature cracks will be generated.

In some long-span bridges, temperature stresses can reach or even exceed live-load stresses. The main characteristic of temperature cracks that distinguish other cracks is that they will expand or close with temperature changes. 3. Cracks caused by loadIn actual engineering, cracks caused by concrete shrinkage are the most common.

Among the types of concrete shrinkage, plastic shrinkage and shrinkage shrinkage (dry shrinkage) are the main causes of concrete volume deformation, as well as autogeneous shrinkage and carbonization shrinkage. Thank you for your patience. The above is my full reply, if you are satisfied with my service, please give a thumbs up, and I wish you all the best!

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