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Select the appropriate additive according to the characteristics of the project
The appropriate additives can be used in almost all kinds of concrete. Almost all kinds of concrete can be mixed with additives, but it is necessary to select the appropriate type of additives according to the different standard requirements, construction conditions and construction technology of concrete.
Pay attention to the quality of additives
At present, there are many brands of additives in China, for example, CSA cement additive. However, most of manufacturers do not clearly classify their product varieties, and the quality of products is different. Therefore, according to the quality standards, the additives and the performance of concrete should be tested before application.
Pay attention to the selection of cement
Among the additive materials, cement has the greatest influence on water-reducing admixture. Different types of cement will affect the water reducing and strengthening effect of water-reducing additive, especially the effect on water reducing. Water-reducing additive is more selective to cement, and the water reducing rate of different cement varies greatly. The mineral composition of cement, setting agent, alkali content and fineness will affect the effect of water reducer. Therefore, the same water reducer often has different effect due to different cement under the same dosage. While the same water reducer can achieve the same phase in different cement with the same water reducing and strengthening effect, the dosage of water-reducing additive is obviously different. When the water reducing agent is available, the water-reducing additive which is more suitable for the construction cement should be selected to play a better role. Before using, the adaptability test of cement and additive should be carried out.
Pay attention to the dosage
Each kind of additive has a suitable dosage. Even if it is the same additive, it has different appropriate dosage according to different uses. If the dosage is too large, it may cause not only a waste in economy, but also a quality accident. If the dosage of water-reducing additive is too small, it will lose its high-efficiency function; if it is too large, it will affect the quality of concrete due to bleeding.
Pay attention to adjusting the mix proportion of concrete
Generally speaking, additives have no special requirements for concrete mix proportion, and can be designed according to common methods. However, in the case of water reduction or cement saving, the sand ratio, cement dosage and water cement ratio should be adjusted appropriately.
Sand rate has great influence on the workability of concrete. The high sand rate not only affects the strength of concrete, but also increases its plastic shrinkage. The specific ratio should be determined by the trial results.
The amount of cement and the use of water-reducing additive in concrete can save cement in varying degrees. The ordinary water-reducing additive can save 5% - 10% and the high-efficiency water-reducing admixture can save 10% - 20%.
The water cement ratio of concrete mixed with water-reducing additive should be determined according to the water reducing rate of the additive.
