Concrete admixtures are characterized by many varieties and small quantities, and they play an important role in concrete modification. Therefore, its quality control, application technology, and variety selection are more important than other engineering materials.
Concrete admixtures are chemical substances that are added during the mixing process of concrete, accounting for less than 5% of the cement mass, and can significantly improve the performance of concrete. Concrete admixtures are characterized by many varieties and small dosages, which have a great impact on the performance of concrete. They have the characteristics of low investment, quick results, and significant technical and economic benefits. With the continuous advancement of science and technology, admixtures have been increasingly used, and admixtures have become the fifth important component in addition to the four basic components of concrete. Admixtures have a certain improvement effect on the carbonation resistance of concrete. There is a certain linear relationship between the carbonation depth and porosity of concrete. Admixtures have a great influence on the frost resistance of concrete. Concrete mixed with air-entraining water-reducing admixtures is anti-freeze. It has good corrosion resistance, but adding early strength agent alone has no effect on improving the frost resistance of concrete
Fourteen chemical admixtures that have formulated national standards or industry standards:
Ordinary reduction Water agent, air-entraining agent, air-entraining water-reducing agent, high-efficiency water-reducing agent, antifreeze, expansion agent, retarding high-efficiency water-reducing agent, waterproofing agent, pumping agent, early strength agent, retarding water-reducing agent, early strength Water reducing agent, accelerating setting agent
1. What is concrete admixture?
It is a substance that is added before or during the mixing process of concrete to improve the performance of concrete.
2. What are the functions of concrete admixtures?
It is mainly to improve the properties of concrete, specifically:
(1) Increase the fluidity of concrete.
(2) Adjust the setting time of concrete.
(3) Reduce bleeding and segregation, improve workability and water elution resistance.
(4) Can reduce slump loss
(5) Reduce shrinkage and even compensate for shrinkage.
(6) Delay the initial hydration heat of concrete, reduce the temperature rise rate of large-volume concrete, and reduce the occurrence of cracks.
(7) Improve the early strength of concrete and prevent freezing at negative temperatures.
(8) Improve strength, increase frost resistance, impermeability, wear resistance, and corrosion resistance.
(9) Control the alkali-aggregate reaction, prevent corrosion of steel bars, and reduce the diffusion of chloride ions.
(10) Made into concrete with other special properties.
(11) Reduce the viscosity coefficient of concrete, etc.
3. What are the main concrete admixtures?
According to the "Definition, Classification, Nomenclature and Terminology of Concrete Admixtures" (GB8075-2005) standard, concrete admixtures are classified according to their main Functions can be divided into four categories:
(1) Admixtures that improve the flow properties of concrete mixtures: including various water-reducing agents, air-entraining agents, and pumping agents.
(2) Admixtures that adjust the setting time and hardening performance of concrete: including retarder, early strength agent, accelerating agent, etc.
(3) Admixtures that improve the durability of concrete: including air-entraining agents, waterproofing agents, and rust inhibitors.
(4) Admixtures to improve other properties of concrete: including air-entraining agents, expansion agents, antifreeze agents, colorants, waterproofing agents and pumping agents, etc.
4. Are concrete admixtures the same as concrete additives?
Concrete admixtures are mother solutions or powders that are compounded with various small materials and added directly according to certain requirements. It is very helpful in many aspects such as concrete workability, pumpability and strength.
Concrete additives actually include concrete admixtures. Admixtures are added based on the concrete proportion and then new things are added, such as expansion agents. With the continuous improvement of industry technology, there are also Additives are added directly to the admixture.
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