Concrete segregation means that the cohesion between the components of the concrete mixture is insufficient to resist the sinking of the coarse aggregate. The components of the concrete mixture separate from each other, resulting in uneven internal composition and structure. Often coarse aggregate separates from the mortar, either as dense particles settle at the bottom of the mix, or the coarse aggregate separates from the mix as a whole. Factors causing concrete segregation and solutions:
1. Solutions to concrete segregation caused by fly ash
First of all, the large fluctuations in fly ash quality will make it difficult to control the quality of concrete. If the amount of food in fly ash control is present, it can cause concrete to segregate. Secondly, when the fineness of fly ash changes from 19% to 4%, the water demand of fly ash is greatly reduced, which can easily cause sudden segregation of concrete. Finally, when the fineness of the fly ash changes from 19% to 38%, the fly ash loses its role as a binder, causing the concrete to segregate.
First of all, strengthen the detection of fly ash and strictly detect the fly ash of every vehicle entering the construction and mixing site. Secondly, according to the quality of fly ash, appropriately adjust the mix ratio of fly ash for concrete mixing. Finally, after incorporating fly ash, water consumption should be appropriately reduced to prevent concrete segregation.
2. Solutions to concrete segregation caused by admixtures
Admixtures used in concrete There are mainly air-entraining agents, retarders, plastic retaining agents and other varieties. Various admixtures can be used individually or in combination to improve the performance and quality of concrete. First of all, excessive dosage of water-reducing agent in concrete mixing will lead to excessive water reduction, insufficient workability of concrete, and may easily cause serious concrete segregation. Secondly, the air-entraining agent in concrete mixing will affect the fluidity of concrete and easily cause concrete segregation during pouring and vibration. Finally, excessive addition of phosphate or sugar during concrete mixing can easily cause concrete to segregate.
First, adjust the mix ratio of concrete admixtures and reduce the amount of water-reducing agent. Secondly, add a certain amount of thickener to the concrete admixture to optimize the slump of the concrete. Finally, adding a certain amount of air-entraining agent during the process of adding admixtures to concrete can not only enhance the adhesion of concrete, but also improve the resistance to segregation of concrete.
3. Solutions to concrete segregation caused by cement
First, cement enters the concrete to mix or After the construction site, the test must be carried out according to the required test items, with special attention to the water demand of the cement. If necessary, the concrete mix proportion test should be re-done according to the actual situation. Secondly, while ensuring that the water-cement ratio of the concrete remains unchanged, the amount of water-reducing agent during concrete mixing should be appropriately adjusted. Third, on the basis of ensuring the strength of concrete, increase the proportion of fly ash in concrete mixing. Finally, by adding an appropriate amount of grade 1 fly ash, the segregation of concrete is controlled and the workability of concrete is improved.
4. Solutions to concrete segregation caused by coarse and fine aggregates
When mixing concrete, The particle size of gravel increases and the gradation becomes worse. A single gradation can easily lead to concrete segregation. Secondly, too much gravel content in concrete mixing will seriously affect the workability of concrete and lead to serious segregation of concrete. Third, the moisture content of sand and gravel, the raw material for concrete, is too high, which easily causes concrete segregation. Finally, the mud content of the sand and gravel in the concrete is too large, which reduces the ability of the cement slurry to wrap the aggregate, causing the separation of the aggregate and the segregation of the concrete.
First of all, strictly implement the aggregate incoming inspection system to ensure the quality of the aggregate. Secondly, when mixing concrete, the sand rate can be appropriately increased to adjust the concrete mix ratio. Finally, when the flake stone chips are too large, the amount of concrete cementitious material should be increased.
Related questions and answers: How to deal with concrete segregation?
Concrete segregation depends on what causes it. It may be too much water, too much additives, or changes in the particle size of the raw materials of sand and gravel. .
But regardless of the cause, appropriate anti-segregation agents can be added to the concrete mixer truck depending on the degree of segregation.
The function of the anti-segregation agent is to evaporate the water in the concrete. It is mainly used to deal with the large slump of concrete or the failure of production control to follow up in time due to material changes. Emergency treatment for special situations where concrete segregation cannot meet construction requirements.
Take powdered concrete as an example. Usually, 0.3-0.5kg is added to each cubic meter of concrete, and then it is poured into the tank with water and stirred for about 3-5 minutes, depending on the site. Fine tune the situation.
Usually a bottle of liquid anti-segregation agent can adjust about 12 cubic meters of concrete.
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