Cold-resistant concrete additives - characteristics and

Concrete is one of the most important building materials. Reliability and safety of various construction objects depend on how well the solution is made and the technology of its application is precisely observed. This material will be devoted to special additives that help the process of hardening the material in the winter.

If the majority of construction works used to stop in winter, today the construction of various objects can be carried out even at low temperatures. Filling in winter designs has become commonplace.

For this, it is only necessary to use certain materials, for example, anti-frost additives in concrete and special equipment, so that the work can be performed as well as reliably and with high quality, as in the normal period.

Winter concreting: features, methods

Since lowering the temperature in the solution below 0 ° C stops the process of its hardening, its operation at temperatures from +5 ° C and lower has a number of its own nuances. The instruction requires the material to gain a certain strength, otherwise with increasing temperature, construction objects may collapse.

In order for the concrete to harden in optimal temperature-wet conditions, different means are used. Most often, various methods of heating the solution are used, including its subsequent maintenance until the required strength values ​​are reached. They depend on the type of construction for which the solution is used, and the temperature of its surrounding environment.

Allocate:

• methods of "thermos";
• method of pre-heating the concrete before pouring it into the formwork;
• electrical heating for monolithic structures using heating wires;
• use of warm concrete;
• creation of thermal formwork;
• special frost-resistant concrete additives or hardening accelerators are used.

In our case, we are interested in the last item. Let us consider in more detail additives for concrete in frost and accelerators of hardening.

How to protect the concrete mix in the cold

To understand why we need frost-resistant additives for concrete and accelerators, it is necessary to study the process of solidification of such a solution. The setting and hardening of the material is called cement hydration.

This is the process of crystallization of various minerals in its composition as a result of their interaction with water:

• the ready solution is set during the first days after the mixture is created. The initial stage of this process will occur already after 2 hours, if the ambient temperature reaches +20 ° С.
• the concrete mortar sets completely after another 1 hour at the same temperature. If the temperature is 0 ° C, the setting time is increased to 10-20 hours.
• the next stage of readiness is hardening. According to calculations at this stage, it takes 28 days, although this process can really go on for years, but in the first days and months it is much more intensive.

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Brand of concrete for frost resistance

Frost resistance is the maximum possible number of freezing and thawing cycles that can withstand samples of a certain size. At the same time their mass should not decrease by more than 5%, and the loss of compressive strength by no more than a quarter.

Based on the specific climatic conditions of a region in which the construction is carried out, the degree of frost resistance of concrete is determined (for example, this indicator will be different for Krasnodar and Murmansk). This indicator is governed by GOST 1006 (0-4) -95.

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This parameter is especially important for concrete solutions used in the construction of the most important objects (for example, bridge supports). Most often, this indicator is directly dependent on the density of the material, since the denser one has a greater frost resistance. On packages, this indicator is indicated by the letter F with the number from 25 to 1000, the higher the grade of concrete, the more this indicator.

A scope of brands from F25 to F100 - construction of houses. A solution with a higher value is used in the construction of hydraulic structures.

Types and scope

During the construction of construction sites in the winter (at temperatures up to -25 ° C, at lower rates, you should not work), experts recommend the use of concrete with frost-resistant additives.

Such additives in the production of added at a temperature of -5 ° C and below. If the temperature is higher, only hot water is used when mixing the concrete solution and no additives are added.

Frosty concrete additives are of two types:

• accelerating the process of setting the solution;
• contributing to a decrease in the freezing temperature of water (lower the temperature from 0 ° C to -10 ° C and lower, do not allow water to turn into ice, so that the process of setting of concrete occurs in the same time as with positive temperature values).

The latter also includes an anti-frost additive for concrete, where the ammonia solution, carbamides, polyhydric alcohols, and sodium nitrite act as additives.

Tip: in the manufacture of the solution with their own hands with or without a concrete mixer, the use of antifreeze additives is mandatory. They are introduced into the concrete solution strictly in accordance with the recommendations of the manufacturer.

Remember that you can not save on the cost of additives, their price - the key to the desired result.

It is also unacceptable to use low-quality additives:

1. Such false savings will degrade the characteristics of the concrete solution.
2. Such additives can not be added in large quantities.

Answers on questions

Some developers believe that the use of antifreeze additives reduces the strength of the concrete material, but this is not entirely true. In the first days after casting, the hardening of concrete occurs more slowly than that of concrete that does not contain additives, but after a reference 28 days, the increase in the strength of the mortar will begin to increase.

There is also an opinion that the addition to concrete during frost enhances the corrosion processes on the reinforcement of reinforced concrete structures. Indeed, if it contains chlorides, it can contribute to the development of such processes on the metal. But additives, having in its composition sodium nitrite, on the contrary, slow them down.

Tip: Experts recommend that in winter, in spite of the use of antifreeze additives, they are further heated when pouring concrete structures.

Conclusion

Concrete work in the winter without the use of special anti-frost additives will not give the desired result. In addition, you can not save on such materials, acquiring low-quality product. The use of additives is strictly regulated by the manufacturer's instructions. The video in this article will help you find additional information on this topic.