What are the causes of concrete cracking? What are the causes of concrete cracking?

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.

If the concrete always cracks, it is basically caused by the following reasons.

1. The first reason is that in the process of construction, the proportion of cement lime is incorrect, and some staff may add water privately in order to facilitate construction in the construction process, thereby improving the fluidity of concrete, but increasing the proportion of water and ash, resulting in irregular cracks when hardening in the later stage.

2. The second reason is that the concrete is in the process of mixing and transporting, the time is too long, resulting in the evaporation of water is relatively fast, and when it comes to on-site construction, the strength of the concrete does not meet the requirements, and cracks will occur.

3. The third reason is that in the process of construction, the construction speed is relatively fast, the pouring is more frequent, and the fluidity will be relatively low, resulting in insufficient concrete settlement, and in the process of pouring in the later stage, especially at the joints, cracks are most likely to appear.

4. The fourth reason is that the maintenance is unreasonable, there is no watering in the later stage, and regular wetting is carried out, so that the surface dries relatively quickly, and once the cement loses water, it will shrink sharply. If the strength is reduced, cracking will occur in the later stage.

5. The fifth reason is also related to the environment. For example, if the air is relatively dry, the temperature is relatively high, and the wind blows, the evaporation rate of the surface of the water concrete will be accelerated, and cracking will occur in the later stage. Especially in summer or winter, temperature difference cracks are most likely to occur.

Cracking, may be related to poor maintenance, such as after pouring concrete, the surface has not had time to cover, exposed to the wind and sun, the moisture on the surface shrinks rapidly, reducing the strength. Unable to resist this stress, cracking occurs.

2. There are also some cracks in the concrete that have been formed, but are affected by the temperature, mainly because of the cracks in the surface temperature, and the cracks caused by the large temperature. This kind of crack is called a temperature difference crack, and generally speaking, there is no law on its direction, some are relatively large, and some are relatively small.

3. Cracks in concrete may also be caused by uneven settlement, mainly because of the settlement of the foundation, resulting in the foundation beam, including the ring beam, etc., which is too large, resulting in cracks.

4. Cracks may also be related to inadequate construction, such as pouring too fast and low fluidity. In addition, if the vibration is not timely, tight and uneven in the later stage, there will be honeycomb or hemp surface.

There are two reasons: one is because the quality of concrete is not up to par.

Second, because of the uneven temperature of the concrete, it is recommended to add ice cubes.

The concrete mixing transportation time is too long.

The template job is not standardized.

The construction speed is too fast, etc.

It may be that the pavement base absorbs water, causing the concrete to shrink, or it may be that the maintenance is not in place, and the temperature is high and causes the shrinkage.

Ask what's going on with cracks all around the wall.

As we all know, cement releases heat when it is hydrated, and the structure of bulk concrete is thicker and has a smaller surface coefficient, which causes the heat generated by cement to accumulate inside the structure and is not easy to lose. As a result, the heat of hydration cannot be dissipated in time, and the higher the accumulation, the increase of the temperature difference between the inside and outside leads to cracks in the concrete.

2. Changes in external temperature.

When building a large volume of concrete, the pouring temperature will change according to the air temperature. Especially when the temperature drops suddenly, the temperature difference between the inner and outer layers of concrete will be greatly increased, resulting in greater temperature stress. In the case of cracks, temperature control measures should be taken in this case.

3. Shrinkage of concrete.

The evaporation of water in the concrete causes the concrete to shrink. The alternation of dry and wet will lead to alternating changes in the volume of concrete, which is not conducive to the volume of large concrete.

4. Constraints.

When a large volume of reinforced concrete and the foundation are poured together at the same time, the temperature rises to a certain extent, and the expansion will occur, so that the lower foundation is constrained and compressive stresses are generated. Moreover, the elastic modulus of concrete is small, and the stress relaxation degree is large, which leads to the infirm connection between concrete and foundation, and the stress is small at this time. However, once the temperature drops, there will be a large tensile stress, and once the tensile strength of the concrete is exceeded, vertical cracks will appear.

It's good to ask questions about how to deal with them.

Answer 1: Surface repair method: the material is coated on the surface of the concrete, which plays a sealing role, and the film thickness is up to millimeters; 2. Filling method: the material is directly filled into the cracks, which is usually used to repair wide cracks, which is simple to construct and low in cost; 3. Structural reinforcement method:

Especially cracks due to overloading; 4. Grouting method: both fine and large seams can be used, and the effect is good.

Hope it can help you kiss it.

Question: Is there a big difference between the repair and the past?

Is the service life the same?

Ask what the fix is counted on, and the person who repaired it can be found there.

1 Plastic shrinkage cracks.

The main reasons for the occurrence of plastic cracks are: the concrete has almost no strength or very little strength before the final setting, or the concrete has just been finalized and the strength is very small, and the water loss on the surface of the concrete is too fast under the influence of high temperature or large wind, resulting in a large negative pressure in the capillary tube and the volume of the concrete shrinks sharply, and the strength of the concrete can not resist its own contraction at this time, so it produces cracks. The main factors affecting the plastic shrinkage cracking of concrete are water-cement ratio, concrete setting time, ambient temperature, wind speed, relative humidity and so on.

2. Settlement shrinkage cracks.

The generation of subsidence cracks is caused by uneven settlement caused by uneven soil quality, softness or backfill soil or water immersion in the structural foundation, or because the formwork stiffness is insufficient, the formwork support spacing is too large or the support bottom is loose, etc., especially in winter, the formwork is supported on the frozen soil, and the uneven settlement is produced after the frozen soil is thawed, resulting in cracks in the concrete structure.

3 Temperature cracks.

Temperature cracks mostly occur on the surface of large volumes of concrete or in concrete structures in areas with large temperature differences.

Summary. In three cases, temperature and humidity changes, excessive deformation caused by external loads, and improper construction methods.

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Severe cracking of concrete, what causes it? Severe cracking of concrete, what causes it? The concrete is severely cracked.

In three cases, temperature and humidity changes, excessive deformation caused by external loads, and improper construction methods.

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The water-cement ratio is not right.

Summary. There are many reasons for concrete cracking, and the following is a list of several 1. Structural design problems. Due to the uneven settlement of the foundation caused by cracking, structural design defects, there are local uneven forces.

2. After the concrete is poured, the curing is not timely, which causes surface cracking.

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, and there is a problem with the ratio, and 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.

What causes concrete cracking?

Hello, I have seen your question and am sorting out the answer, please wait a while Oh Shashi, is there a possibility that something will go wrong?

It is also possible because of the quality of the sand and gravel or the wrong ratio.

The most common problems with cracks in concrete engineering are shrinkage cracks caused by constrained shrinkage deformation and load (force) cracks caused by external loads. It is difficult to avoid the appearance of cracks in pure concrete, but they can be prevented and treated. After the crack appears, the crack is a problem that needs to be solved.

Extension: concrete, referred to as "concrete (tóng)": refers to the general term of engineering composite materials that are cemented into a whole by cementitious materials.

The word concrete usually refers to the use of cement as cementitious material, sand and stone as aggregate; Cement concrete, also known as ordinary concrete, is widely used in civil engineering engineering when it is mixed with water (which can contain admixtures and admixtures) in a certain proportion and is mixed to obtain cement concrete.

Concrete can also be divided into low-strength concrete (compressive strength less than 30MPa), medium-strength concrete (compressive strength 30-60MPa) and high-strength concrete (compressive strength greater than or equal to 60MPa); According to the amount of cement per cubic meter, it can be divided into: poor concrete (cement consumption does not exceed 170kg) and rich concrete (cement consumption is not less than 230kg).

The calculation of the water-cement ratio of high-strength concrete can not use the formula of the strength of ordinary concrete, and the relationship between the strength of concrete and the water-cement ratio should be proposed according to the test data, and then used as a diagram or calculation method to find the water-cement ratio corresponding to the strength of the concrete preparation. When a number of different mixtures are used for the strength test of the registered concrete, one of them should be the benchmark mixture, and the water-cement ratio of the other mixtures should be increased and decreased respectively compared with the benchmark mixture.