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.
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