Hello everyone, let me answer the above questions for you. Concrete segregation treatment agent, many people still don’t know the cause of concrete segregation, let’s take a look at it now!
1. Factors affecting concrete segregation: cement: Cement is the most important cementing material in concrete. The stability of cement quality directly affects the stability of concrete quality.
2. Changes in cement quality will cause segregation of concrete, and there are many factors in cement that affect the performance of concrete mixtures.
3. 3.1.1 Changes in cement fineness As we all know, the higher the fineness of cement, the higher its activity and the greater the water demand of cement. , at the same time, the greater the fineness of the cement, the stronger the adsorption capacity of the cement particles to the concrete water-reducing agent, which greatly weakens the water-reducing effect of the water-reducing agent.
4. Therefore, in actual production, when the fineness of cement is greatly reduced, the water consumption of concrete admixtures will be greatly reduced.
5. The decrease in cement fineness can easily cause excessive amounts of concrete admixtures and cause segregation of concrete.
6. And this kind of segregation usually occurs in high-strength concrete with a higher amount of water-reducing agent.
7. Changes in cement mineral components: The most important mineral components in cement are C3S, C2S, C3A, C4AF, etc. Among them, C3A and C3S are very important for water reducing agents. The adsorption activity of cement is strong, so the adaptability of cement with high C3A and C3S content to admixtures is worse than that of cement with low C3A and C3S content. When the content of C3A and C3S in cement is high, the demand for admixtures in concrete is reflected On the contrary, the amount of water-reducing agent can be appropriately reduced, otherwise the concrete will easily segregate.
8. Changes in alkali content in cement: The alkali content has a great influence on the adaptability of cement and admixtures. As the alkali content of cement decreases, the water reducing agent The water-reducing effect is enhanced, so when the alkali content of cement changes significantly, it may have a greater impact on the viscosity and fluidity of concrete.
9. The impact of cement storage time: Cement is a hydraulic cementitious material. If it is not stored well, it is easily affected by moisture. After the cement gets damp, the water demand will decrease. At the same time, the longer the storage time of cement, the temperature of the cement itself decreases, and the fine cement particles condense into larger particles through adsorption, which reduces the surface energy of the cement particles and weakens the adsorption of the cement particles to the water-reducing agent. During the concrete test, the water reduction of the water-reducing agent is often enhanced, and the new concrete mixture appears to ooze slurry and catch the bottom.
10. In actual production, if cement stored for a long time is used, even if the concrete mix ratio is the same as before (when the concrete mix was produced with this ratio in the past, the (good performance), it may also cause the segregation of concrete. Of course, the impact of cement storage time on different types of cement is inconsistent, which needs to be understood through experiments.
11. The storage time of cement will cause obvious changes in the adaptability of cement and admixtures.
12. Especially when doing trial mixing of concrete mix proportions, special attention should be paid to the consistency between the cement sample during the trial mixing and the batch supply of cement. This can effectively To ensure the feasibility of trial fitting work.
13. During the production process, if the cement is stored for too long, it is best to conduct a suitability test on the cement and admixtures to re-determine the reasonable mixing of admixtures. quantity to ensure good workability of concrete.
14. Admixtures used in concrete are mostly composed of water-reducing agents and other compounds such as air-entraining agents, retarders, plastic retaining agents, etc. It is a multi-functional product and an indispensable material for pumping concrete. The addition of admixtures can greatly improve the performance of concrete mixtures (fresh performance and long-term performance), but improper use of admixtures may lead to segregation of concrete.
15. (1) If the amount of concrete water-reducing agent is too large and the water-reducing rate is too high, the water consumption of a single concrete will be reduced, which may cause the reduction The water agent did not fully play its role in the mixer, but continued to work during the concrete transportation process, causing the slump of the concrete to the site to be greater than the slump when it left the machine.
16. This situation can easily cause serious segregation of concrete.
17. It often appears in high-strength concrete and is extremely harmful to concrete.
18. (2) Excessive amounts of retarding components and plastic-preserving components of admixtures, especially excessive amounts of phosphates or sugars, can easily cause Causes concrete to segregate.
19. Fly ash is one of the important admixtures in concrete. Fly ash has great microbead effect, filling effect and volcanic ash effect in concrete. Improved concrete workability, compactness and strength properties.
20. High-quality fly ash is an ideal material for preparing concrete. It can replace 10% to 30% of cement, which greatly reduces the cost of concrete production.
21. However, the supply of fly ash on the market is now tight, and most…No one can guarantee the quality of fly ash. The quality of fly ash fluctuates greatly, which increases the difficulty of concrete quality control and sometimes causes segregation of concrete.
22. Sand and gravel are the most commonly used materials in concrete. The quality of sand and gravel directly affects the quality of concrete. Fluctuations in the quality of sand and gravel can easily cause the segregation of concrete. And there are many factors causing segregation.
23. (1) The increase in gravel particle size, deterioration of gradation, and single gradation can easily cause the segregation of concrete.
24. (2) Excessive stone content in sand, especially excessive flake stone chips, will seriously affect the workability of concrete, resulting in concrete severe segregation.
25. (3) The moisture content of sand and gravel is too high (especially the moisture content of sand is too high, greater than 10%), which will make it difficult to control the quality of concrete. , it is easy for concrete segregation to occur.
26. Since the water content in the sand is too large and is in a supersaturated state, when the concrete mixture is mixed in the mixer, the water content in the capillary tubes on the surface of the sand cannot It is released in time, so it is easy to use too much mixing water during mixing; at the same time, during the transportation of concrete, the water in the aggregate capillary is continuously released, destroying the bond between the aggregate and the cement slurry, causing the concrete to deteriorate. Separate the bleeding water.
27. (4) Excessive mud content in sand and gravel will reduce the bonding force between cement slurry and aggregates, and the ability of cement slurry to wrap aggregates. decreases, resulting in the separation of aggregates and concrete segregation.
28. Mixing a certain amount of mineral admixtures into concrete can, on the one hand, improve various properties of concrete, and on the other hand, it can achieve good economic benefits.
29. Therefore, the use of mineral admixtures is very common in various concrete mixing stations, such as: slag powder, steel slag powder, silica powder, zeolite powder, etc.
30. Various mineral admixtures have different effects on concrete segregation.
31. Silica powder and zeolite powder have strong ability to resist the segregation of concrete and can greatly improve the workability of concrete.
32. Due to its large specific gravity, steel slag powder can increase the density of mortar after being added, which is helpful to improve the workability of concrete.
33. The incorporation of slag powder will increase the viscosity of concrete to a certain extent, and concrete will easily segregate. The degree of influence is closely related to the fineness of slag powder. Generally, the higher the fineness, the better the concrete’s resistance to segregation.
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