About the causes of concrete segregation and how to prevent it

In the process of building construction, concrete is the most used basic building material. At the same time, the quality of concrete directly determines the quality of the project. Therefore, the quality of concrete production, transportation, and pouring processes must be strictly controlled.

In fact, concrete does encounter some problems during the production and transportation process, which may affect the quality of concrete, such as concrete segregation. Segregation is one of the most common problems with concrete. It not only changes the pumping properties of the concrete, but may also cause the concrete to become less functional. Today we will talk about the causes of concrete segregation and how to prevent concrete segregation.

1. Causes of concrete segregation

What is concrete segregation?

Concrete segregation mainly refers to a phenomenon in which the cohesion between the components of the concrete mixture is insufficient and the coarse aggregate sinks. Under normal circumstances, if a large amount of water is secreted from the concrete, it is basically certain that the concrete has segregated.

After segregation, the various constituent materials of concrete show an obvious layering phenomenon, with aggregate at the bottom and water at the top. If you stir the concrete at this time, you will find that it has lost its original stickiness. Therefore, the main manifestations of concrete after segregation are: separation and layering, bottom grabbing, poor workability, etc. These can lead to changes in the properties of concrete, ultimately affecting the quality of the project.

1. Poor cement quality leads to segregation

Cement is the most important component of concrete. The quality directly determines the performance of concrete. At the same time, segregation also has a lot to do with cement. Therefore, changes in cement properties directly affect the quality of concrete.

Cement fineness is one of the most important parameters to measure the performance of cement. It represents the thickness of cement. The finer the cement, the larger the area after combining with water, and the stronger the activity. If the cement fineness is reduced, the concrete material will have severe segregation problems. Therefore, the higher the performance of the cement, the more susceptible the concrete is to segregation problems.

In addition, the alkali content in cement also determines the performance of cement. If the alkali content fluctuates from high to low, it can easily lead to segregation problems in concrete. At the same time, the cement that has just been poured into the cement silo will also cause the concrete to segregate due to excessive temperature. In short, after segregation of concrete occurs, the first thing that comes to mind is to detect whether the quality of the cement has changed.

2. Aggregate causes segregation

The interaction between coarse aggregate and fine aggregate , in order to make the gaps inside the concrete smaller, so as to better ensure the fluidity of the concrete and prevent the problem of concrete segregation. Secondly, if the mud content in the sand and gravel is too high, it will also deteriorate the performance of the concrete and eventually lead to concrete segregation.

At the same time, if the water content in the sand and gravel is high, it will be difficult to effectively squeeze out the water in the sand and gravel during the concrete mixing process. On the contrary, larger bubbles are formed in the sand and gravel materials, which is not conducive to the stability of concrete. Moreover, if excess moisture is secreted during transportation, this will directly lead to concrete segregation.

3. Segregation is caused by admixtures

There are many types of admixtures. At the same time, They also have different functions. For example, water reducing agents are used to reduce the amount of water in concrete, which can not only ensure the flow performance of concrete, but also prevent segregation. Because the water content in the concrete is reduced, the chance of concrete segregation is greatly reduced.

However, if the wrong type of admixture is used, or the amount is incorrect, it can also cause segregation problems in concrete. Therefore, admixture is a double-edged sword, with advantages and disadvantages. How to use admixtures needs to be determined according to the actual situation. Do not increase or decrease the amount of admixtures arbitrarily.

4. Segregation caused by equipment reasons

During the production process of concrete, various materials The dosage is strictly in accordance with the proportion and is accurately measured by the weighing system of the mixing station. However, the probability of weighing system failure is still high. If, in the production process of concrete, the amount of a certain raw material is too much or too little, it will directly change the properties of the concrete. Referring to the above three causes of concrete segregation, equipment failure is very likely to cause concrete segregation.

2. What are the hazards of concrete segregation?

1. The pumping performance of concrete decreases

The pumping performance of concrete is the most intuitive Performance is the fluidity of concrete. After concrete segregates, its fluidity plummets. This will lead to the problem of pump clogging easily occurring during the pumping process of concrete. Most clogged pipe problems are caused by concrete segregation.

2. Decrease in concrete quality

After segregation, the concrete is layered. During the pouring process, the sand and gravel at the bottom increase, while the surface is mostly cement slurry. After hardening, the concrete is prone to dust and ash, which directly leads to unqualified project quality. .At the same time, if the aggregate gap in the concrete after segregation is too large, it will cause bubbles in the concrete and cause a honeycomb phenomenon. Or, the strength of the concrete after hardening is not enough, which can easily cause cracking problems.

3. Prevent concrete segregation

First of all, of course, it is still necessary to strictly control the quality of concrete raw materials, especially after replacing cement. Later manufacturers, or newly imported cement, need to keep samples to test the performance of the cement. As for aggregates, the moisture content and mud content must also be strictly controlled.

During the production process, concrete needs to be produced in strict accordance with the mix ratio. The operator cannot change the amount of certain raw materials in the concrete at will. During the transportation process, no one can add water or other additives to the concrete at will to ensure that Consistency of concrete quality.

Concrete segregation is a problem that is difficult to control. The actual situation needs to be treated realistically. In the daily production process, it should be strictly followed Production process services. Analyze the possibility of problems from all aspects and solve them one by one.</p