At present, the use of a single breed admixture in concrete admixture is very rare, has gradually toward the direction of efficient and multi-functional development of concrete admixture purpose is to meet the need of concrete to various performance at the same time, and the common action between each compound and produce superposition effect Compound admixtures are usually made up of a variety of surfactants, or inorganic electrolytes, such as composite early strength agent composite antifreeze pumping agent composite retarder air and water reducing agent and other general compound admixtures by at least two or more than two components, forming binary or multivariate compound Each admixture in the compound admixtures acts at different stages of cement hydration or together at the same time.
Principle of preparation
With a certain rate of water reduction slump to maintain the performance of low pressure bleeding and a certain air entrainment performance, that is, water reduction, slump, plastic, water retaining and air entrainment.
Basic components and functions
Water reduction component + protection slump retarded component + Air entrainment component + water retention other additives
Water reducing components include: lignin naphthalene series superplasticizer sulfonated melamine superplasticizer amino sulfonate superplasticizer aliphatic superplasticizer superplasticizer poly carboxylic acid superplasticizer
Under certain water-binder ratio, the workability of concrete can be guaranteed to meet the requirements of construction technology. According to different cement and admixtures, water reducing components should be adapted to them, and the amount should be sufficient.
The retarder components include lignin, sugar, phosphate, tartrate, gluconate, citric acid and its salts, cellulose and its derivatives and other organic and inorganic components.
Control slump loss and concrete setting time to ensure proper delivery and pumping. When using different raw materials and different mix ratio, appropriate retarding components should be used, and the amount of use is appropriate, to avoid the problem of cement adaptability and setting time abnormality. The water reduction rate increases when used together with water reduction components.
Water retention components include various water reducing agents, cellulose and its derivatives, etc
According to the concrete trial mix, adjust the variety and dosage of water-retaining components to ensure the workability of concrete to meet the requirements.
Air entrainment components include vensa resins, pine soaps, alkyl sulfonates, alkyl benzene sulfonates, lignin, etc.
Proper air entrainment can improve the pumping performance and workability of concrete, and has a great benefit to the durability of concrete. There is a certain rate of water reduction. Make concrete contain gas quantity to be in commonly 2-3% or so appropriate (special product excepted), do not affect the strength of concrete not only, the improvement of all sorts of performance to concrete is more obvious also
1. When preparing admixtures, the adaptability between them and various raw materials should be fully considered. At the same time, the interaction between different components and the sequence of solid dissolution should be paid attention to.
2 different cement and admixtures, admixtures in other components on the performance of water reducer is still very big, such as naphthalene system water reducer and sodium gluconate used together, water reduction rate increased significantly, organic and inorganic to reasonable collocation.
3. Different cement and admixtures as well as different mix ratios will make the retarding effect change.
4. The air-entraining effect of the air-entraining agent is affected by many factors, such as cement fineness, gravel particle size, sand mud content, temperature, mix ratio, etc. When fly ash is added, the fine material is more, the stone particle size is small, the slump is large, the temperature is low, and the gas content of concrete will be high.
In short, the adjustment of admixtures should be carried out according to the actual situation, based on the test results.
Post time: Jun-01-2021