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Each additive is responsible for certain properties of the resulting mixture. According to qualitative parameters, classification into categories is carried out as follows:
Plasticizing
The inclusion of additional components ensures the plasticity of the mixture without adding excess liquid. Also plasticizers in the composition of concrete increase the strength and resistance of structures to frost.
Air Entraining
The pores inside the material give free space for water expanding during the freezing process. The percentage of air entraining additives should be minimal, because a large amount of impurities reduces the strength of the mixture.
Setting accelerators
These additives are used to accelerate the process of hardening of concrete. Low ambient temperature slows down the process of hydration of concrete. The accelerator significantly reduces the curing time, which allows the use of multi-layer casting.
Setting retarders
They are used in cases when it is necessary to increase the time interval for maintaining the survivability of the mixture. Use in the first case justifies itself when the ready mix is to be delivered to the construction site, which is located at a great distance from the production site.
Compactors
Increasing the density of the mixture contributes to its durability. The compactor fills the space between the grains of concrete, which leads to an increase in strength. Also, these components help to reduce pores, which significantly increases the impermeability of the structure.
Corrosion Inhibitors
The principle of their action consists in the formation of an oxide film on the anode. Concrete admixtures introduced in small quantities will protect the reinforcement from corrosion. Inhibitors cannot be used in combination with chlorides, because they contribute to the destruction of the oxide film.
Antifreeze
They allow you to perform work on concreting at temperatures up to –25 ° C. The main task of these impurities is to accelerate the process of removing the liquid from the solution. Antifreeze additives for concrete make it possible to work at sub-zero temperatures without additional heating.
Selection of additives
Additives that are introduced into concrete must be selected in accordance with the requirements for technology. The choice of certain components should solve the following tasks:
- improve the technological properties of concrete;
- regulate the mobility of the mixture;
- increase durability and water resistance;
- increase resistance to frost and corrosion;
- reduce the amount of time for heat treatment;
- reduce the consumption of expensive cement and aggregate;
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