Why does concrete segregation, causes and remedies for concrete segregation

The segregation of concrete is that the cohesion between the constituent materials of the concrete mixture is not enough to resist the sinking of the coarse aggregate, and the components of the concrete mixture are separated from each other, resulting in uneven internal composition and structure. This is usually manifested by the separation of the coarse aggregate from the mortar, e.g. by the deposition of dense particles to the bottom of the mixture, or by the separation of the coarse aggregate from the mixture as a whole.

Causes of segregation.

The causes of segregation may be improper pouring and vibration, the maximum particle size of the aggregate is too large, the proportion of coarse aggregate is too high, the content of cementitious material and fine aggregate is too low, the density of coarse aggregate is too large compared with fine aggregate, or the mixture is too dry or too thin. The use of mineral admixtures or air-entraining agents can reduce the tendency to segregation.

The hazards of segregation.

It affects the pumping construction performance of concrete, resulting in sticking tanks, blocking pipes, affecting the construction period, etc., and reducing economic benefits.

Affecting the apparent effect of the concrete structure, the concrete surface appears sand grain, aggregate exposure, steel bar exposure and other phenomena.

The strength of concrete is greatly reduced, which seriously affects the bearing capacity of concrete structure, destroys the safety performance of the structure, and seriously causes rework and huge economic losses.

The homogeneity of concrete is poor, resulting in inconsistent shrinkage of various parts of concrete, and it is easy to produce concrete shrinkage cracks. Especially during the construction of concrete floor slabs, due to the concrete segregation, the cement slurry layer of the surface layer is thickened, and the shrinkage increases sharply, and serious cracking occurs. It greatly reduces the durability of concrete such as impermeability and frost resistance.

1, the water-cement ratio is too large, the concrete collapse is too large, in the vernacular is thin, the water is big, the workability of the concrete is not good after the water is large, the large aggregate can not get the restriction of cement and other binders, it will sink, which leads to segregation, 2, the coarse aggregate particle size is large, the cause of segregation caused by poor aggregate gradation is the same, when the aggregate gradation in the concrete is good, all kinds of aggregates will form a whole, and the small material fills the gap of the large material, Sand fills the gaps of small materials, cement slurry combines these to form concrete aggregates, and when the gradation is poor, the material cannot form a whole, of course, segregation.

3. If the amount of superplasticizer is large, it will be too dry and inappropriate.

1. Too much water;

2. Excessive dosage of admixtures;

3. The sand rate is too small;

4. The quality of admixtures is not good;

5. The stirring is uneven or the time is too short;

6. Other known or unknown reasons.

There is more water. There are too many admixtures.

To put it bluntly, the collapse is too big, big, big, big, and it will be separated.

The essential reason is that the cement slurry cannot suspend the stones.

The cement slurry is too thin.

The causes and remedies of concrete segregation are as follows:

The causes of concrete segregation are: poor cement quality, aggregate segregation, admixtures, regret equipment failure reasons, etc.

Remedies for concrete segregation:

1. For the concrete segregation caused by the problem of aggregate moisture content, it is also effective to control such problems by prolonging the mixing time to solve the problem of increasing the amount of admixtures such as fly ash.

2. In the construction process, the quality should be strictly controlled, and unqualified materials should be resolutely prevented from entering the construction site to ensure the stable quality of aggregates.

3. If the water content in the sand of the letter fiber fruit is in a saturated state, the method of prolonging the mixing time can be adopted to solve or increase the amount of admixture such as fly ash.

4. Improving the sand rate to adjust the concrete mix ratio can also solve the segregation. The main reason for the problem of concrete segregation is that it is stopped for too long and is not stirred, or the water-cement ratio is too large. Treatment method: In general, the first phenomenon should be stirred in time to do the slump test, and the slump test can be carried out normally only when the slump test is suitable.

If the water-cement ratio is too large, adjust the amount of water consumption in time, and it is best to have a tool or meter to measure the amount of water.

Concrete segregation mainly refers to the phenomenon of insufficient cohesion between the constituent materials of concrete mixture and the sinking of coarse aggregate. Under normal circumstances, if a large amount of water is secreted in the concrete, it can basically be determined that the concrete has been segregated.

Hello, I am happy to answer for you: how to prevent the segregation of concrete The solution is as follows: (1) After the cement enters the factory, it must be tested according to the required test items, pay special attention to the water demand of cement, and when the water demand is abnormal, do the adaptability test of cement and the admixture used in time.

If necessary, re-do the concrete mix test. (2) Under the premise of ensuring that the water-cement ratio of concrete remains unchanged (basically ensuring the 28-day strength of concrete), the dosage of superplasticizer should be appropriately adjusted. (3) On the basis of ensuring the strength, the production is carried out with a large amount of admixtures such as fly ash (commercial concrete companies should have different proportions of the same strength grade), which must be based on tests.

Replacing the hail mold cement with a small amount of fly ash will be able to control the segregation of concrete and improve the workability of concrete. Admixtures. Most of the admixtures used in concrete are multi-functional products composed of superplasticizers and other products such as air-entraining agents, retarders, plasticizers, etc., which are indispensable and important materials for pumping concrete, and the incorporation of admixtures greatly improves the performance of concrete mixtures, but improper use of admixtures may lead to the segregation of concrete.

Segregation refers to a phenomenon in which the cohesion between the constituent materials of the concrete mixture is not sufficient to resist the sinking of the coarse aggregate. It is mainly manifested in the separation, delamination, sinking of the bottom, and poor workability of concrete bones. Concrete segregation will seriously affect all aspects of concrete performance.

I believe we all know that if there is a phenomenon of segregation when the concrete mixer is used, it will become very troublesome. However, when such a phenomenon occurs in concrete, the first thing we need to do is to find a way to remedy it. So, how to remedy concrete segregation?

What are the hazards of concrete segregation? Let's find out together!

1. How to remedy concrete segregation?

First of all, it is necessary to control the slump of the concrete machine, because after reducing the slump of the machine, the time of concrete mixing can be effectively increased. In general, the segregated concrete can be mixed for the next time. However, if the phenomenon of concrete segregation is very serious, it can only be scrapped.

2. What are the hazards of concrete segregation?

1. The pumping performance of concrete decreases.

We all know that the pumping function of concrete is the most common, which actually refers to the flow function of concrete. However, when the phenomenon of segregation occurs in concrete, its flow function will slowly weaken. This can easily lead to pump blockage during pumping.

2. The quality of concrete declines.

When the concrete is segregated, the sand and gravel at the bottom will slowly increase. However, because there is a lot of cement slurry at this time, after they are hardened, the concrete will appear dusty, easy to ash and other phenomena, and in serious cases, it will also lead to unqualified project quality. At the same time, the skin is scattered, because the gap between the concrete aggregate after segregation is relatively large, so it will lead to the phenomenon of honeycomb and bubbles in the concrete.

In addition, because the strength of the concrete after hardening is not qualified, it is easy to crack the image of the situ excavation.

Hello, I'm sorry to keep you waiting, I can only remedy it, if the concrete is segregated, we must first control the slump of the concrete out of the machine within a certain range, so as to reduce its slump, and then increase the mixing time of the concrete. Generally speaking, the segregated mixed concrete can also be stirred in the next step, but it also depends on the condition of its segregation. If the segregation is particularly severe, it can no longer be stirred, and it can only be invalidated.

If the concrete is segregated, then its feeding performance will be reduced. To put it simply, it is concrete, and its function of flowing and moving bridges is reduced. Because of the segregation, its own flow function is weakened.

As a result, the concrete will be blocked in the process of feeding. Basically, it's because the mixer is clogged, but it's also because of the segregation of concrete.

1.The dosage of admixtures is too large.

2.The water-glue ratio is too large.

3.The sand rate is too small.

4.Gravel grading is not good.

5.The adaptability of admixtures and cementitious materials is poor.

6.Improper construction workmanship.

In the process of engineering construction, quality accidents caused by concrete segregation often occur. Such as: pouring concrete columns, after the removal of the mold, found that from the bottom to the top can be clearly divided into several sections, namely:

The normal concrete part, the honeycomb part with more gravel, the mortar part with more sand content, and the chalky part with almost no sand.

There are many reasons for concrete segregation, and its prevention and control measures should also be considered from many aspects. In the above example, it was caused by the large amount of water deposited in the column and the concrete was poured without inspection.

In the process of modulating concrete, we must master the skills, so that we can know what kind of dust is more appropriate. Next, I will introduce to you what problems will occur in concrete segregation.

What problems can occur when the concrete pie is segregated late.

1. The fluidity will be weakened, and the pump will be blocked when pumping. 2. There will be large gaps between aggregates, bubbles and honeycombs. 3. It will lead to the coagulation after hardening, the strength is difficult to reach the standard, and cracking will occur.

What to pay attention to in concrete construction.

1. Fine sand cannot be used for surface mortar.

Because there will be a variety of pressures and impacts on the ground, it must have good wear resistance and strength. When choosing sand, it is also based on coarse and medium sand, remember not to choose fine sand, or the dry shrinkage is relatively large, and it is easy to crack. The water retention of fine sand is poor, the pressure will be poor, and there will be sand problems in the later stage.

2. The maintenance time should be sufficient.

After the concrete construction, it can be cured, usually in about a week, if the time is not long, this leads to the concrete hardening slowly, it is also difficult to achieve a hardness, and it will be sandy, it is possible to make the strength low, and the surface layer will be damaged.

3. Control the water-cement ratio.

During construction, the water-cement ratio should also be paid attention to, not too large, or the surface will be rough and wear-resistant, which will affect the compactness of the concrete. If you can't use damp cement, not only the strength will decrease, but the cementation cavity will also be poor, and the sand phenomenon will occur.

4. Master the calendering time.

Before the concrete solidifies, the time should be controlled, not too early, or it will affect the strength of the mortar, if the time is too late, it will also destroy the structure of the cement gel, and it will also hinder the strength of the mortar to grow, and there will be fine pores or sand on the surface.