In experiments and practices, people have found that adding admixtures to concrete can improve the technical functions of concrete and achieve significant technical economic effects. However, accurate and reasonable use has a major impact on the technical and economic effects of concrete admixtures. If used improperly, accidents may occur. Therefore, when using admixtures, you should pay attention to the following points:
(1) Selection of types of concrete admixtures
There are many types of admixtures with different effects, especially for different types of concrete admixtures. The same type of cement has different effects. When selecting admixtures, it should be determined through experiments based on project requirements, on-site material conditions, reference to relevant data, and experiments.
(2) Determination of the dosage of concrete admixtures
Concrete admixtures all have suitable dosages. If the dosage is too small, it usually cannot achieve the expected effect; if the dosage is too large, , it will constitute waste, sometimes affect the quality of concrete, and even cause quality accidents. Therefore, the best dosage should be determined through experiments.
(3) Methods of adding concrete admixtures
Admixtures are mixed into concrete mixtures in different ways, and their effects are also different. For example, the post-mixing method of water-reducing agent is better than the first-mixing method and the simultaneous-mixing method, and the dosage is only half of that of the first-mixing method and the simultaneous-mixing method. The so-called first-mixing method is to mix the water-reducing agent with cement first and then mix it with aggregate and water; the simultaneous-mixing method is to dissolve the water-reducing agent in water to form a solution and then add it to the mixture and mix it together; the post-mixing method It means that after the concrete mixture is delivered to the pouring location, the water-reducing agent is added and mixed evenly again for pouring. Therefore, the use of concrete admixtures must be determined through experiments based on project characteristics, material conditions and construction conditions.
Construction technology of cement concrete admixtures in highway projects
Requirements for raw materials
The concrete raw materials used to mix admixtures in highway projects include cement , gravel, water, sand, etc., except for special circumstances, their respective use requirements are subject to compliance with relevant national regulations.
Adaptability test
In highway projects, when concrete admixtures are used in cement concrete structures, the adaptability of the admixtures and cement needs to be tested. Unsuitable admixtures cannot be used. Use, or replace in time. When the basic properties of cement variety, strength, grade, etc. used in highway engineering cement concrete do not change, the adaptability of the cement needs to be tested and strengthened.
Sampling and quality inspection
(1) Basic requirements for sampling: Admixture products in highway construction are transported in batches of 20t, and those with a total amount of less than 20t can also be transported. Called a batch. Each batch is required to select 15 working points, take 300g of samples from each point, mix them, and divide them into 4 equal parts, of which 1 part is selected for inspection and 1 part is sealed for 3 years.
(2) Quality and performance inspection: After the test results meet the basic performance of the admixture, it must reach the standard of first-class products. In cement concrete pavement using admixtures, every 10km can be used as a road section. The quality and performance of large and medium-sized pavements using admixtures must be inspected during use.
The application technology, varieties and precautions of concrete admixtures were analyzed, and it was pointed out that relevant standards must be strictly observed during the addition and construction process of admixtures, and efforts should be made to avoid the consequences of improper use of admixtures on highway projects. losses, and fundamentally improve the sustainable development of cement concrete pavements in highway projects in my country.
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