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Mistakes in the Use of Concrete Ads

Release time:

2022-11-28

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With the development of modern buildings to high-rise buildings and the development of concrete to centralized mixing ready-mixed concrete, the application of concrete admixtures is becoming more and more extensive. However, improper application of admixtures often fails to achieve the expected results and even causes quality accidents. Then, let's understand the misunderstanding of the use of concrete admixtures!

Concrete admixture is an indispensable and important part of modern concrete, and also a method and technology of concrete modification. It can improve the physical and mechanical properties of hardened concrete, improve the quality and durability of physical components of real estate, save cement, reduce costs and speed up the progress of the project. With the development of modern real estate to high-rise buildings and the development of concrete to centralized mixing ready-mixed concrete, the application of concrete admixture is more and more extensive, but the application of admixture is improper, often fail to achieve the desired results, and even cause quality accidents.

Misunderstanding 1, concrete admixture without testing direct use

Before concrete construction, construction units and supervision units always send cement, sand, stone and other building materials products to testing institutions for testing in batches according to the requirements of the specifications, but the performance testing of admixtures is often not paid much attention. In fact, there are many types of concrete admixtures, and there are corresponding quality standards, its performance directly affects its role in concrete, such as the size of the water reduction rate, the amount of chloride ion content, etc.

Misunderstanding 2. according to the actual situation of the project does not use concrete admixture

1. Please consider the purpose of use to choose external additives

When the admixture is selected, it shall be determined through the test according to the engineering materials and construction conditions. All kinds of admixtures have their own characteristics. When using admixtures, they should be considered according to the characteristics of admixtures and the purpose of use, such as saving cement, improving concrete performance, accelerating template turnover and other comprehensive indicators. In other words, the use of admixtures must be determined through technical and economic comparison.

2. Several kinds of concrete application of admixture

Analysis

1) The purpose of applying admixtures in waterproof concrete is to improve the impermeability of concrete. In order to improve the impermeability of concrete, reduce the internal voids of concrete and block the leakage channel, the application of water reducing agent and air entraining agent is the key.

2) The key of mass concrete construction technology is to ensure the good combination of the initial solidification of the layered pouring concrete, reduce the temperature rise when the concrete hardens, and avoid the concrete cracking. The use of retarding water reducing agent can reduce the above requirements, that is, the temperature rise of retarding and concrete hardening, and improve the quality of concrete.

3) In large-span prestressed concrete structures, since the structure weight is often the main contradiction, the purpose of using admixtures is to prepare high-strength concrete, reduce the weight of the structure, and effectively use the stress of high-strength steel bars. It is suitable to use high-efficiency water reducing agent to greatly reduce the unit water consumption,

Misunderstanding three, do not pay attention to the adaptability of concrete admixture and cement

1. What is the practicality of admixture and cement

The compatibility of concrete admixtures with cement can be interpreted as follows: admixtures that are confirmed to meet the standard are mixed into concrete composed of cement that can be used in accordance with the regulations. If the original effect can be obtained, the cement is suitable for the admixture.

2. Examples where admixtures and cements are not suitable for applications

There are adaptability problems between most varieties of concrete admixtures and cement. In several kinds of ordinary portland cement, when adding a certain kind of high-efficiency water reducing agent to prepare concrete (verified to meet the quality standard of high-efficiency water reducing agent), under the same conditions, the concrete prepared by a certain cement has a large shortage in water reduction rate, which is because the cement In addition, adding a certain cement to prepare concrete meeting the quality standard of the accelerator can not achieve the rapid setting effect, adding a retarder can not achieve the retarding effect, this may be due to the admixture and cement do not adapt to cause.

Key words:

Concrete admixture

The importance of concrete admixture to concrete quality