Concrete projects are the focus of construction. Concrete quality problems will be transmitted to building quality along the construction sequence. Therefore, the construction industry should strengthen research on concrete-related issues. Concrete segregation is a common quality problem in concrete construction. Concrete segregation manifests itself in the occurrence of phenomena such as separation of coarse and fine aggregates, deposition of large particles, and concrete bleeding. Concrete segregation can easily affect the quality of concrete construction, extend the concrete construction time, and reduce the strength of the concrete structure. It is a problem that cannot be ignored in concrete projects during construction. Improper pouring and vibration, proper proportion of coarse and fine aggregate, and low cement content are the main causes of concrete segregation. Construction companies should focus on the details of concrete construction, control materials and processes, effectively prevent the occurrence of concrete segregation, and improve the quality of concrete projects and building construction.
1. The harm of concrete segregation
1.1 The impact of concrete segregation on construction
First of all, concrete segregation will cause great waste and reduce the economy of construction. benefit. Secondly, concrete segregation will cause sticky pots and blocked pipes, extending the construction period of concrete projects. Finally, concrete segregation can also cause quality problems and bring hidden dangers to the construction quality of buildings.
1.2 The impact of concrete segregation on concrete structures
First of all, concrete segregation will have an impact on the appearance of the structure. Concrete segregation will form sand patterns and exposed aggregates on the surface of the concrete structure. , exposed steel bars and other appearance quality issues. Secondly, concrete segregation will have an impact on the strength of the concrete structure. Concrete segregation will seriously affect the bearing capacity of the concrete structure. The decrease in the structural bearing capacity will destroy the safety performance of the structure. It will not only easily cause the rework of the construction project, but also cause huge economic losses to the construction project. Third, concrete segregation will cause structural cracks, and concrete segregation will lead to a decrease in the homogeneity of concrete. During the construction of concrete floor slabs, concrete segregation will cause serious cracks in the floor slab. Finally, concrete segregation reduces the durability of concrete structures, and concrete segregation reduces concrete impermeability and frost resistance.
2. Preventive and control measures for concrete segregation caused by cement
2.1 Concrete segregation caused by cement
Cement is the main cementing material in concrete. The main factors for concrete segregation are: first, the higher the fineness of the cement, the higher its activity, the greater the water demand of the cement, and the stronger the adsorption capacity of the cement particles to the concrete water-reducing agent, which greatly weakens the water reduction. The water reducing effect of the agent. Secondly, the increase in alkali content in cement will lead to changes in the water-reducing agent during concrete mixing. Changes in the water-reducing agent may have a greater impact on the viscosity and fluidity of concrete, which can easily lead to segregation of concrete. Finally, the longer the cement is stored, the more obvious the phenomenon of cement condensation after getting wet will weaken the adsorption of water-reducing agent by cement particles during mixing. Cement stored for a long time can easily cause segregation of concrete.
2.2 Solutions to concrete segregation caused by cement
First of all, after the cement enters the concrete mixing or construction site, it must be tested according to the required test items, paying 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 used 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, add appropriate amounts of fly ash I and II to control the segregation of concrete and improve the workability of concrete.
3. Preventive and control measures for concrete segregation caused by admixtures
3.1 Concrete segregation caused by admixtures
The main admixtures used in concrete include air-entraining agents, Various admixtures such as retarders and plastic retainers can be used alone or in combination to improve the performance and quality of concrete. First of all, if the amount of water-reducing agent is too large during concrete mixing, it will lead to excessive water reduction, which will cause the concrete to lack workability and easily cause serious concrete segregation. Secondly, the air-entraining agent in concrete mixing will affect the fluidity of concrete, and concrete segregation will easily occur during pouring and vibration. Finally, excessive addition of phosphate or sugar during the concrete mixing process can easily cause segregation of concrete.
3.2 Solutions to concrete segregation caused by admixtures
First, adjust the mix ratio of admixtures in the concrete mixture to purposefully reduce the amount of water-reducing agent. Secondly, a certain amount of thickening agent is added 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 cohesion of concrete, but also improve the segregation resistance of concrete.
4. Preventive and control measures for concrete segregation caused by fly ash
4.1 Concrete segregation caused by fly ash
First, the quality of fly ash fluctuates greatly. It will make it more difficult to control the quality of concrete. If the amount of fly ash is controlled, it will cause segregation of concrete. Secondly, when the fineness of fly ash changes from 19% to 4%, the fly ashThe water demand of � is greatly reduced, which can easily cause sudden segregation of concrete. Finally, when the fineness of fly ash changes from 19% to 38%, fly ash loses its function as a cementing material, causing segregation of concrete.
4.2 Solutions to concrete segregation caused by fly ash
First of all, strengthen the detection of fly ash, and conduct inspections on each vehicle entering the construction and mixing sites. Strict testing. Secondly, the mix ratio of fly ash should be appropriately adjusted according to the quality of fly ash for concrete mixing. Finally, after adding fly ash, water consumption should be appropriately reduced to prevent segregation of concrete.
5. Preventive and control measures for concrete segregation caused by coarse and fine aggregates
5.1 Concrete segregation caused by coarse and fine aggregates
First of all, the particle size of gravel when mixing concrete Increase, gradation deterioration and single gradation can easily cause concrete segregation. Secondly, excessive stone content during concrete mixing will seriously affect the workability of concrete and lead to serious segregation of concrete. Third, the moisture content of the concrete raw material sand and gravel is too high, which is prone to concrete segregation. Finally, the excessive mud content of sand and gravel in concrete causes the cement slurry's ability to wrap aggregates to decrease, causing the separation of aggregates and causing concrete segregation.
5.2 Solutions to concrete segregation caused by coarse and fine aggregates
First of all, strict inspection system for aggregate entry to ensure the quality of aggregates. 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 cementing material should be increased.
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