How to add concrete admixtures appropriately? What data indicators are there?

Throughout the development history of concrete, from traditional concrete to the emergence of modern concrete, concrete admixtures have played an important role. Since the advent of concrete admixtures, its promotion and application has not been smooth sailing. Many authorities have denied the application value of concrete admixtures from a technical perspective. Practice has proven that concrete admixtures play an important role in improving the properties of fresh concrete and hardened concrete. With the research and exploration of admixtures, concrete construction technology and new types of concrete have made great progress.

Concrete admixtures are mainly substances added to improve the performance of concrete. They are now a very widely used raw material in the construction industry. The application of various admixtures makes concrete materials achieve high performance. One of the important measures for performance and greening. Concrete preparers should conduct quality inspection and concrete trial mixing tests for each batch of cement and admixtures, seek the technical characteristics of the raw materials, and try to use admixtures with good adaptability to each other with cement to avoid incompatibility. Quality accidents, material waste or cost increase caused by the joint use of cement and admixtures.

Common misunderstandings about the use of concrete admixtures

1. Purchase admixtures at low prices

Due to fierce market competition, mixing stations have strict control over the procurement of raw materials. Mixing stations all hope to purchase raw materials at the lowest price, and the same goes for concrete admixtures.

Mixing stations lower the purchase price of admixtures, which will inevitably lead to admixture manufacturers lowering their quality levels. In general, the acceptance criteria for admixtures are rarely specified in the procurement contracts of mixing plants. Even if there is, it is only in accordance with the national standard requirements, and the national standard requirements are generally the lowest standards. This leads to the fact that when admixture manufacturers win the bid at a low price, the admixtures they supply are of low quality and generally barely meet the national standard requirements, making it difficult to meet the functional requirements of the mixing station for the use of admixtures.

　2. Limit the amount of concrete admixtures

The decision-making level of the mixing station strictly monitors the mix proportion cost, and even has clear requirements on the cement dosage and admixture amount. This will inevitably lead to the technical department not daring to break through the decision-making layer’s maximum dosage requirements for additives when designing the mix ratio.

3. Lack of quality monitoring and trial preparation verification of admixtures

At present, for the incoming inspection of admixtures, most mixing stations conduct solid content, water reduction rate, For 1 to 2 of the technical indicators such as density and slurry fluidity, few mixing stations conduct concrete tests.

In production practice, we have found that even if technical indicators such as the solid content of admixtures, water reduction rate, density, and fluidity of the slurry meet the requirements, the concrete test may still not achieve the effect of the original trial mix. , that is, the concrete water reduction rate is insufficient or the adaptability is poor.

In actual projects, the adaptability test of cement and concrete admixtures should be completed before the preparation of concrete mixtures, so that cement, admixtures and admixtures can be correctly selected and the optimal Optimized mix ratio. During construction, cement plants and admixture plants should provide products with stable quality. If a certain batch of cement or admixtures has incompatibility problems, we should immediately cooperate to analyze and find the reasons to find effective countermeasures.

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