Filling the solution at sub-zero temperatures. At what temperature can concrete be poured - construction in winter and summer. Methods for heating concrete mass

At the turn of the seasons, the question of at what temperature it is possible to pour concrete under the foundation is of particular relevance so as not to endanger the structural elements of the new building. To get an answer, it is necessary to understand the ongoing processes inside the cement slurry.

Hydration of concrete - thickening and hardening of cement mortar

Hydration is the chemical process of hardening a mixture of cement and water into stone. It begins after mixing the mortar, however, the concrete setting occurs only after the foundation is poured. While the mixture is mixed with a mixer or concrete mixer, it is subjected to vibrations, due to which hardening is delayed, and the quality of the concrete does not suffer at all. After the mortar is removed from the concrete mixer, the material begins to harden and goes through two stages:

1. 1. At the first stage, the mortar sets. This process, depending on the composition of the mixture and external conditions, takes from 1 to 20 hours.
2. 2. At the second stage, the mortar hardens and gains up to 90% of its final strength. This process takes place within 28 days. After that, the concrete continues to harden throughout the entire service life.

The course of hydration directly depends on external factors, in particular, on the ambient temperature. At +5 degrees Celsius, the setting process begins after 2 hours and lasts up to 10 hours. At +20 degrees, 3 hours after pouring the concrete, its hardening begins, while the setting has not yet had time to complete. The hardening of cement is due to the components that make up its composition: tricalcium aluminate, tricalcium silicate, dicalcium silicate, tetracalcium aluminoferrite.

Answering the question at what temperature can the foundation be poured, we can say that ideal conditions for hydration are as follows:

1. 1. The temperature of the mixture is +30 degrees Celsius in normal weather conditions, up to +70 degrees in the cold months due to the heating of the components (water, sand and gravel) warm air or ferry.
2. 2. Temperature environment(air) - from +5 to +30 degrees Celsius.

Due to the fact that the solidification (hardening) temperature of concrete has a framework, when pouring the foundation, it is necessary to take into account external conditions.

Rules for concreting the foundation in the summer months

It is believed that pouring the foundation in winter is the most difficult, because due to sub-zero temperatures, the solution may freeze before the completion of the hydration process. However, the heat is no less dangerous for a fresh foundation than winter frosts. Due to the high outside temperature during chemical reaction cement mixture will increase in volume. After the formation of the cement stone, it will inevitably cool down and decrease, but this will not happen due to the formed crystalline structure.

As a result, freezing high temperature leads to strong internal stress in the foundation before construction begins structural elements a new house, and the owner will receive a foundation in operation, capable of cracking at any time. Usually, their first signs appear already a few hours after laying the solution inside the formwork.

High summer temperatures force builders to use special fast-hardening Portland cements if foundation pouring is planned to be carried out at temperatures above +25 degrees and at air humidity less than 50%.

The brand of cement used should be one and a half times the design parameters of concrete, in addition, to improve the performance of the foundation, plasticizers and various modifying additives will have to be added to the mixture, due to which hydration will slow down. For concreting, we recommend using the least hot hours of the day (early morning or evening). Another danger to the foundation of a house in the summer is the possible dehydration of the solution. To protect concrete from water evaporation, you must:

• cover the surface with chips, sand or sawdust;
• moisten the foundation from the watering can;
• water wooden formwork from buckets.

Winter work – construction at low temperatures

At low temperatures hydration does not accelerate, but slows down, as a result of which the foundation does not have time to gain the strength it needs. At zero degrees, the process of solidification of the solution in the outer layer stops completely, and inside the structure it continues for several hours until all components have cooled down. In this case, water does not have time to react with cement, after which it freezes, increases in volume and literally breaks the structure of concrete.

Specialists are well aware at what temperature concrete can be poured for the foundation without fear of losing its performance. Frost is a significant obstacle to concreting, because in winter period professionals have to use special technologies and means:

• heating of concrete elements before pouring and formwork heating;
• laying a heated cable inside a slab or;
• feed to reinforcing cage elements electric current for heating;
• installation of heaters around the foundation for the first three days;
• creating a greenhouse by covering the entire perimeter of the foundation with a film;
• introduction to the mixture special reagents, which reduce the t of water crystallization or accelerate the hardening time of the foundation.

The use of any of the described technologies significantly increases the cost of building a foundation. Therefore, it is difficult for private owners to recommend these funds. There are other ways to pour concrete when sub-zero temperature. One of them is to change the amount of water and cement in the produced solution. It requires the most accurate and competent dosage of the used components of the mixture. Calculate at home required amount water and cement to improve the hardening of the foundation in winter is almost impossible.

• heating two-thirds of the water for the solution to t of the order of 70 degrees Celsius;
• adding sand and gravel to the water;
• adding the remaining third of the water and cement to the mixture.

Mixing the solution should be done twice as long as usual. The time of vibration compaction also increases by 1.5 times. Before pouring the solution, the formwork must be checked for ice, snow removed and the underlying layer warmed up. We cover the poured solution polymer film, which will keep the mixture warm for a while. If the above rules for concreting the foundation cannot be observed at home, it is recommended to wait for the air temperature to rise above +5 degrees. With a favorable forecast for the next three weeks, the owner of the house will be able to fill using standard technology.

The dependence of the cost of work on the weather - how to save on the foundation?

Almost all modern construction companies work on pouring concrete summer months, in late spring and early autumn. All this is explained very simply - at this time it is cheapest to carry out construction in general and build a foundation in particular.

Building a house in winter can lead to additional and extremely significant financial expenses:

• with the most optimistic forecasts, the construction budget in the cold months increases by 25-30% ;
• thaws in winter do not eliminate the need to use expensive reagents in the construction of the foundation;
• in winter it is impossible to prepare the solution on the spot, therefore the owner will have to additionally order the delivery of concrete by mixers;
• a transformer substation is required to heat the foundation, since the home electrical network cannot withstand such high loads.

The only advantage of building a foundation in winter months lies in the possibility in early spring to start erecting the structures of the facility and complete the construction, necessary finishing and other works by the end of autumn. In practice, the owner has to invest colossal funds in winter construction, which will definitely overshadow the joy of building a private house.

Construction in modern world you can start not only in spring, summer and early autumn, but now late autumn and even in winter.

And this became possible with the invention of antifreeze additives. We will talk about this interesting additive later.

Application conditions

Such additives make it possible to use low-quality instead of expensive high-quality ones, and this makes it possible to reduce the cost of concrete products. Due to this, it is also possible to reduce the thickness of the product, for example, floor slabs, moreover, without compromising quality.

About the use of antifreeze additives

How to use

How to cook containing special additive?

An antifreeze additive is added to concrete along with other ingredients (sand, water, plasticizer). Better supplement add along with water, because the additive can replace water. Everything must be mixed well with a concrete mixer for an hour, until a homogeneous mass.

The additive is introduced into the mixture according to the instructions on the package. This amount is approximately 0.2% of the amount of cement at an air temperature not exceeding or decreasing the value indicated on the package.

In the event of a decrease in temperature, the dosage of the additive should be increased at the rate of 0.05% per degree. On the packaging, the dosage is indicated in grams.

In the event that the dosage of the additive is indicated in milliliters, then in order to determine the amount of the substance, its mass is divided by 1.45. The result obtained will be the volume in milliliters. Then we measure right amount and add to the mixture.

Antifreeze additives are used only at sub-zero ambient temperatures. They cannot be used under other conditions! After pouring concrete, structures made of this material are moistened for about two days.

Construction objects

The use of antifreeze additives makes it possible to build at any time of the year and under any weather conditions. Due to this, the construction time of facilities is reduced, as well as the cost is reduced due to rational operation. construction equipment and labor force.

Antifreeze additives are used:

• in the manufacture of heavy and light reinforced concrete structures,
• in the construction of monolithic reinforced concrete structures,
• it is added to
• when laying pavement and production of road elements,
• build bridges, oil and gas platforms, various buildings, dams, dams and much more.

Antifreeze additives are applicable at air temperatures from -15 to approximately -25 ° C, depending on the substance used.

To shops, retail network antifreeze additives delivered in containers with a volume of 1 m3 or 5 liters.

If you are thinking of building in the cold season, we recommend that you use antifreeze additives and be sure to carefully read the instructions on the packaging of additives.

We hope that this article was useful to you. We wish you good luck in your endeavors!

Undoubtedly, to engage in construction in winter time harder than in summer. Often weather not very conducive to doing quality work. Usually work in severe frosts continue either professional construction teams, or craftsmen who want to move into their own homes as soon as possible. invaluable help for those and others there will be specialized antifreeze additives. The use of the latter helps to prevent premature hardening of the cement.

What is an antifreeze additive in the solution?

As a rule, with a significant decrease in ambient temperature, builders begin to experience additional difficulties in working with concrete and all kinds of solutions. This is because cement-based compounds cannot stand frost. So, at a temperature of -5 o C, it would seem that high-quality solutions cease to gain strength.

AT last years craftsmen are increasingly using antifreeze additives that can withstand temperatures down to -35 ° C or more. Specialized formulations for contain chemicals, active ingredients which are reduced As a result, the concrete sets in the masonry even in extreme cold.

The problem of organizing brickwork in cold weather

When building in winter, it becomes most problematic to provide the structures with the necessary strength. When the temperature drops below zero, the liquid in the solution crystallizes. Thus, the process of cement hydration is stopped.

With an increase in air temperature, the ice formed inside the masonry and on the surface of the building material begins to melt, which necessarily causes a decrease in the adhesion of the solution. Another negative effect is the formation of small cavities in the concrete structure, which can subsequently lead to a rather rapid destruction of walls and ceilings.

Features of the preparation of the solution

In spite of difficult conditions work, can be no less qualitative than in the warm season. However, in order to obtain the expected result, it is necessary to prepare a special solution, which must contain antifreeze additives.

Getting Started Cooking building mix you need to take care of your personal safety. It should be borne in mind that almost all antifreeze additives differ in composition based on fairly aggressive chemical substances which may be harmful to health. Therefore, during the preparation of concrete, it is necessary to work in tight gloves, goggles, rubber boots and, if possible, overalls.

With a more serious cooling down to -30 ° C, it is advisable to use potash. The advantage of this solution is protection against corrosion manifestations in case of construction reinforced floors. The use of potash also prevents the appearance of efflorescence on the hardened mortar. As for chlorine-containing additives, the latter do not slow down the destruction of the reinforcing parts of building structures.

Antifreeze additive: consumption

In the manufacture of formulations for brickwork it is important to observe the necessary proportions. They depend primarily on the ambient temperature.

Let's look at the average norms typical for the use of the most popular "antifreeze" in the table. It reflects the consumption of antifreeze additives in percentage to the mass of cement.

plasticizers

Can be replaced with special plasticizers, which increase the elasticity of the mortar and reduce the need for liquid. Thanks to the use of the latter for several days, there are practically no changes in the laid composition. Thus, the solution has time to seize even with significant frosts.

In addition to masonry, such a specific anti-frost additive can be used for glue, preparation of mixtures for arranging self-leveling floors, when performing concrete works. Plasticizers are mixed with a minimum amount of water. Their content in the solution is about 5% by weight of the cement. Compliance with this proportion is sufficient to perform reliable masonry at low temperatures.

What you need to know about masonry work in the winter?

In order not to be disappointed in the results of construction activities that are carried out at negative air temperatures, it is enough to pay attention to the following recommendations:

1. For masonry, it is forbidden to use building materials covered with snow, frost or ice.
2. All components of the future solution, including antifreeze additives and plasticizers, should be stored in dry, ventilated areas at room temperature.
3. Regardless of the composition of the solution and temperature conditions laying in winter is recommended to be done as soon as possible. The lack of delay allows the substances to seize faster.
4. Going on a break, the rows of masonry must be insulated plastic wrap or other suitable material suitable for the role of an effective temporary insulator.
5. As a basis for preparing the solution, it is worth using cement of a grade not lower than M-50. Mixing the components, even in the case of the use of "antifreeze" should be carried out in a warm room.
6. If necessary, work with low temperatures it is better to give preference to the acquisition ready solutions, to which antifreeze agents are added in optimal proportions at the production stage.

Eventually

While doing construction works in winter, the main thing is not to forget to add special antifreeze additives to the solution. However, the introduction of "antifreeze" in cement composition looks appropriate only if the ambient temperature drops to -5 o C.

During the preparation of the solution, it is absolutely not recommended to use long-stored, old antifreeze additives with a questionable shelf life. Otherwise, you will have to pay with the formation of abundant smudges and efflorescence on the surface of the structures.

Pouring concrete is an integral part of most construction work. As is known, ideal period for repair and construction work - this is a warm season and pouring concrete is no exception to this rule. However, what should those who decide to continue construction despite the frosty weather do?

Pouring concrete at sub-zero temperatures in most cases is contraindicated by SNiP standards, since extreme cold does not allow the compositions that contain liquid to fully polymerize. But in some cases, the circumstances are such that the concrete must be poured, no matter what. And the question is quite natural, is it possible to pour concrete at sub-zero temperatures?

For areas where there is no warm season or situations in which winter construction is vital, there are several technological solutions that can be used to form concrete structures without compromising quality. In this article, you will be given detailed instructions how to pour concrete at sub-zero temperatures.

Pouring concrete

At sub-zero temperatures, the liquid in cement mortar freezes and the ice crystals break crystal lattice concrete, thereby weakening the strength future design. After thawing, the bond structure is not restored, and the structure loses a significant part of the strength potential, up to complete destruction.

The direct effect of sub-zero temperatures on concrete structure permissible only after it acquires the required amount of strength, frost resistance, etc. In construction terminology, this value is called the critical strength threshold - after overcoming it, frost does not negative impact on the concrete structure.

The threshold of critical strength is determined depending on the brand concrete mortar. The standard cement mix of the M400 brand must gain at least 30% of its maximum strength, and the lower the concrete grade, the higher the percentage of gained should be.

Before pouring concrete in sub-zero temperatures, it is necessary to create conditions that will prevent it from freezing. There are several technologies that help create or maintain the temperature necessary to overcome the critical strength threshold.

Among them are the following:

• Mixture heating. Before pouring concrete at sub-zero temperatures, the solution is heated to a certain state, which gives it the opportunity to overcome the critical strength limit as it cools;
• Internal heating. Maintain positive temperature in reinforced reinforced concrete structures it is possible through internal electric heating, which is carried out at the expense of electricity and metal components;
• External heating. It is possible to create the temperature necessary to achieve critical strength using external steam or;
• thermal insulation. Pouring concrete at minus 5 degrees can be carried out using high-quality insulated formwork, which does not release heat from the inside and allows cold to penetrate inside;
• The use of specialized additives that prevent water from freezing.

Each of these technologies has its own characteristics, which must be taken into account, giving them their preference. Consider the above options in more detail.

Mixture heating

The concrete solution is kneaded on heated water, the temperature of which can be from 60 to 90 degrees. This technology can only be used if the ambient temperature does not fall below -15 degrees. This circumstance should be taken into account if you are wondering, “At what sub-zero temperature can concrete be poured?”

Specialty Blends

AT cement mixture various antifreezes are added to prevent the formation of ice crystals. Most often, calcium chloride or sodium chloride (table salt) is used for this purpose, which can be no more than 2% of the total mass of the components. If the temperature does not fall below 15 degrees below zero, then modifying additives will save the structure from freezing.

Note!
Despite the fact that the price of modifying components is quite affordable, it is best to purchase factory mixtures that guarantee technical qualities product.
A homemade recipe mixed with your own hands can be a waste of resources.

thermal insulation

If you want to pour the foundation at sub-zero temperatures, then you can do without heating or third-party additives. It is enough to qualitatively insulate the formwork with sheet or loose insulation.

During the crystallization of the concrete solution, heat is released, which is quite enough to overcome the critical strength threshold if the formwork is assembled according to the thermos principle. However this technology undesirable to use at too low temperatures.

Note!
Heat-insulating formwork can be used in conjunction with the above technologies - thus, you will increase their effectiveness.

Internal and external heating

Internal heating is carried out by connecting to the reinforcing frame alternating current from a special transformer - the metal is heated and heats the cement mixture. External heating consists of a specialized mobile formwork, which contains heating elements that are powered by steam or electricity.

The disadvantages of this technology are the high cost of construction - the enormous consumption of resources for heating affects. Also, this technology cannot be used independently, since without the presence necessary knowledge and equipment, it is impossible to achieve the desired effect.

Among the advantages, it should be noted that you may not think about the question, “Up to minus how much concrete can be poured?” - concrete heating allows pouring at temperatures up to -25 degrees.

Outcome

The correct approach to the question of how to pour concrete in sub-zero temperatures makes it possible to obtain a high-quality result even in the most adverse conditions. In the future, eliminate small errors and establish additional elements concrete cutting will help you diamond circles and diamond drilling holes in concrete. More detailed information on this topic you can get by watching the video in this article.