Introduction To The Functions Of Seven Concrete Admixtures

Concrete admixture is a material added before or during concrete mixing. Its main purpose is to improve the properties of fresh concrete or hardened concrete. Nowadays, construction requirements are getting higher and higher, and various requirements are put forward for concrete, such as high fluidity, early strength, high strength, rapid setting, retarded setting, anti-freeze, anti-penetration, low heat of hydration and other performance requirements. In order to meet these performance requirements, concrete admixtures need to be used. Next, the functions of seven concrete admixtures will be introduced.
1. Water reducing agent
Without reducing the amount of mixing water, adding water-reducing agent to concrete can significantly improve the fluidity of the mixture. Reducing water without reducing cement can increase the strength of concrete. If water is reduced at the same time, cement is appropriately reduced. dosage, you can save cement. At the same time, the durability of concrete can be significantly improved.
2. Early strengthening agent
The performance of early strength agent is consistent with its name. It is an admixture that can improve the early strength of concrete and has no obvious impact on the later strength. In actual application, it can shorten the concrete construction and maintenance cycle, improve the construction technology, and increase the turnover rate of formwork and site. Early strength agents can only play a practical role in concrete with frost resistance requirements, concrete in low or negative temperature environments, etc.
3. Retarder
Moderators are mainly used for concrete in high-temperature seasons, large-volume concrete, commercial concrete constructed by pumping and slip form methods, and long-distance transportation. They are not suitable for concrete constructed with daily low temperatures below 5°C, and cannot be used for concrete with early strength. Required concrete and steam cured concrete.
4. Air-entraining agent
Air-entraining agent is a form of anionic surfactant. In practical applications, it has certain activity due to the active agent on its surface. After adding air-entraining agent to the concrete mixture, the air microbubbles introduced during the mixing process can be evenly distributed in the internal structure of the concrete, and these microbubbles can remain in a relatively stable state for a long time. Dissolve the air-entraining agent in water. In this case, whether it is gaseous or liquid, it can be adsorbed and form a strong liquid film through interfacial activity, foaming and foam stabilization. The inherent tension at the solution surface gradually decreases. On this basis, the contact area between air and liquid can be increased, and the adsorbed air-entraining agent molecules can further ensure the stability of the liquid film and ensure that the bubbles will not burst. A large amount of data can confirm that the gradual increase in the amount of air-entraining agent will gradually increase the internal air content of concrete.
5. Expanding agent
Expanding agents cause a small amount of volume expansion in concrete during the hardening process.
6. Antifreeze
Antifreeze can significantly reduce the freezing point of concrete at a specified temperature, so that the liquid phase of the concrete does not freeze or only partially freezes, thereby ensuring cement hydration and obtaining the expected strength within a certain period of time.
7. Pumping agent
Pumping agents are admixtures used to improve the pumping performance of concrete.
At present, water-reducing agents are commonly used in concrete. The commonly used water-reducing agents are naphthalene-based water-reducing agents and polycarboxylic acid-based water-reducing agents. Water-reducing agents are surfactants that can reduce water consumption and improve the strength and durability of concrete under the same flow.