In the age of new technologies and high speeds everything is developing very quickly. Appear technical solutions, allowing you to perform work faster, better and more efficiently than a couple of decades ago. The construction industry also boasts many innovations that have significantly increased the speed of construction projects. If earlier, for example, when asked whether it is possible to pour the foundation in winter, the developer would have heard a clear “no,” today the answer will not be so categorical. Let's figure out how to carry out this work without loss of quality.
Pouring concrete in winter - some nuances
The question of constructing the foundation of the structure in winter divided the builders into two diametrically opposed camps. The first - adherents of classical technology - believe that no innovations can provide high-quality hydration of the solution. Without it, the strength characteristics of the base may be reduced. The second, supporters of various know-how, argue that it is possible to fill the foundation in winter, providing the required foundation parameters.
Both views on resolving this issue have the right to life. Traditional foundation pouring at above-zero temperatures is described in detail in many sources. Let's try to figure out how to carry out work during the cold season. At subzero temperatures, the water in the solution begins to crystallize, which ultimately leads to an increase in the porosity of the concrete mass. The main problem when pouring the base in winter is ensuring high-quality hydration of the concrete solution.
Not so long ago, with the onset of frosts, it was customary to “freeze” construction in our latitudes.
Hydration - educational program for novice builders
The solidification process at above-zero temperatures occurs in stages:
- a thin shell of acidic salt forms on the surface;
- in the upper layers, cement particles are bound with water;
- the outer layer, losing moisture due to evaporation, slowly contracts;
- the cement is bound by water at the next level.
The process gradually covers all layers. Within a month, the concrete gains the necessary strength, sufficient for the next stages of work.
When pouring a foundation in winter, it is difficult to evaporate moisture, which gradually freezes. This leads to an increase in the porosity of the concrete mass and a significant decrease in its strength. Therefore, the main rule for concreting in winter is to ensure normal temperature conditions that prevent the formation of ice crystals during hardening.
Pouring the foundation in winter - technological features
To reduce hardening time, several methods are used that are aimed at maintaining the temperature of the concrete mass within limits that ensure normal hydration conditions.
The length of winter breaks in construction forced residents of the northern country to look for methods that would allow them to continue concrete work in the cold
Heat is retained using:
- pair;
- electricity;
- infrared or induction radiation;
- thermal tent;
- thermal insulation around the formwork.
Let's look briefly at each of the methods.
Heating with steam
Heating the concrete mass with steam significantly accelerates hardening. By maintaining the temperature within 70 degrees Celsius for 1–1.5 days, the concrete reaches a strength corresponding to the solidification of the mass for 15 days at above-zero temperatures.
The duration of steam heating depends on:
- required strength;
- type of cement used;
- warm-up temperature.
Steam heating is carried out by arranging a steam jacket, which is mounted at a distance of no more than 15 cm from the formwork. This parameter ensures free steam flow around the array.
Owners, puzzled by the problem of whether it is possible to fill the foundation in winter, receive a clear affirmative answer, but with many variations
Heating by electric carriers
You can create favorable conditions for concrete hardening using electrical energy. The most common heating methods are:
- electrodes;
- PNSV wires.
Heating with electrodes is a fairly cheap method. Various types of electrodes are used for work:
- strings The main area of application is pouring vertical structures (pillars, columns, beams);
- rod-shaped To maintain the required temperature, metal fittings with a diameter of 8–12 mm are used;
- lamellar. When using plates, they are placed on opposite planes of the formwork.
More effective method warming up - using the PNSV wire. The high efficiency is explained by the fact that the heat source is not the concrete mass, but the wire itself, the temperature of which is much easier to regulate.
A type of electrical treatment of a concrete mass is the effect of infrared or induction radiation on it. Due to the complexity and uneven heating of large volumes, these methods are rarely used.
The electrodes are connected to the transformer at one end, and to the fittings at the other end in increments of about half a meter
Arrangement of a thermal tent
In this article we will discuss the pressing question of whether it is possible to pour concrete in cold weather and how to do this with the least damage to the quality of the final result. It is no secret that the use of cement-containing mortars in winter is practiced in industrial construction, since the construction of individual low-rise buildings can be preserved until the onset of the warm season.
However, there are exceptions to this rule, and concrete has to be poured into the formwork at sub-zero temperatures. Let's consider how this can turn out and how to avoid such consequences.
In the photo - laying the foundation at sub-zero temperatures
Low temperatures are a negative factor when concreting
Instructions for the winter use of cement-containing mortars are significantly complicated by two features that negatively affect the rate of setting and hardening of the material:
- slowing down the hydration of cement particles and, as a consequence, increasing the duration of time required to gain strength;
- freezing of water in concrete, resulting in a stop in the process of strength gain.
Let's try to figure out how many days after pouring concrete is afraid of frost and how the above factors affect the rate of strength gain.
Low temperatures in the range from 0 to +10 degrees inhibit the hydration of cement. That is, cement particles are saturated with water more slowly and chemical reactions responsible for the intensity of strength gain occur more slowly. As a result, the material not only dries slowly, but even after complete drying it has insufficient strength characteristics.
For example, under normal temperature conditions (+20°C), concrete gains at least 70% of its optimal strength within a week. The material acquires similar strength indicators, at which it is possible to cut reinforced concrete with diamond wheels, at a temperature of +5°C within 4 weeks.
The photo shows the use of concrete with antifreeze additives
Temperature parameters are a catalyst for most different chemical processes and cement hydration is no exception. Therefore, in the process of manufacturing concrete products, various technologies for heating cement-containing mixtures are widely used.
For example, the previously mentioned 70% of the brand strength, at which it is possible to carry out diamond drilling of holes in concrete, the material gains within 12 hours at a temperature of 70°C and a humidity of over 80%.
While temperatures below 10 degrees Celsius slow down the development of strength, negative temperatures completely stop these processes. Since the water in the solution partially or completely freezes out, chemical reactions become impossible.
In accordance with concreting technology, cement particles must be in contact with water during the entire period of curing. Average term required for this process to occur under normal climatic conditions is 28 days. But as already mentioned, a lack of heat can negatively affect the process, and therefore construction in winter will require a special approach.
Features of working with cement mortars at low temperatures
Since we are considering winter concreting, we will agree that it takes place at sub-zero temperatures. Therefore, our main task is to prevent freezing of the water included in the solution.
Currently, several popular and effective methods are known to protect water in cement mortars from crystallization.
Among these methods we note:
- use of antifreeze additives (AMD);
- use of electric heating
- sealing the solution with polyethylene films and insulation;
- the use of temporary prefabricated shelters around the formwork with IR heaters or heat guns.
Let's talk about each of these methods in more detail.
Antifreeze additives (AMD) and their use
In the photo - antifreeze additives (AMD)
This method of ensuring optimal solution hardening parameters has become widespread. Almost all domestic specialized enterprises have mastered the production of winter concrete with PMD additives.
On this moment Several variants of winter-type solutions have been developed, differing from each other in the percentage of additives in relation to the volume of material used.
Among the advantages of the method, we note the following:
- Ease of use when producing concrete with your own hands, since additives are poured into the mixer simultaneously with other components;
- Complete safety, in comparison with the same electric heating;
- Affordable price of PMD, which has a positive effect on the cost of the finished object.
Important: The use of additives in individual construction has one significant drawback. To ensure optimal strength properties, PMD must be used in strict accordance with laboratory tests, which most contractors prefer to turn a blind eye to.
Application of electric heating
On large construction sites Before pouring concrete in cold weather, special electric heating systems are installed. For these purposes, powerful transformer equipment with a capacity of over 30 kW and a system of thermal cables are used.
The method has the following advantages:
- the possibility of effective heating throughout the entire thickness of the layer and, as a result, ensuring uniform setting of the mixture;
- possibility of accelerated dialing over large areas at temperatures down to - 20°C;
- suitability of the method for combination with thermally insulated formwork.
Among the disadvantages, we note high energy consumption and the high cost of concreting.
Sealing the solution with polyethylene films and insulation
Sealing and insulating the mixture using materials with low thermal conductivity today seems to be the most rational method of working with concrete at temperatures as low as -3°C.
The process of hardening and drying of cement mortars is isothermal. In other words, when cement particles interact with water, a chemical reaction occurs and a certain amount of heat is released into the external environment. Thus, by covering the formwork and its contents with cellophane or peat-insulating material, this heat can be saved and used to ensure strength gain.
Of course, this method is not the best solution for severe frosts. But if necessary, the solution can be preheated, and after that it can be covered and then construction can be done at temperatures down to -10°C.
The use of heat guns and IR heaters
If the air temperature drops below -15°C, instead of the previously listed methods, it is advisable to use more effective methods warming up. For example, during the construction of small objects around structures made of monolithic concrete, temporary collapsible shelters are built, inside which heat guns are used.
In some cases, the formwork can be wrapped with thermomats with infrared heating function. This technique is quite effective, but expensive to implement.
Conclusion
So, we looked at the features of concreting in winter and found out that sub-zero air temperatures are not yet a reason to abandon construction. But if there is such an opportunity, it would be better to postpone the planned work to warmer days.
If you still have any questions that require comprehensive explanations, you will find the answers you are interested in by watching the video in this article.
The best time for construction work is the warm season. But it also happens that for a number of reasons it is necessary to start or continue construction in the winter, when there are sub-zero temperatures outside. The main part of the construction work is the construction of a foundation for the house, the strength and quality of which will determine the reliability of the building. In this article we will figure out whether it is possible to fill the foundation in winter.
In some areas there is soil, excavation which is difficult to deal with in the warm season due to its susceptibility to shedding. In some regions there are climatic zones in which there is no summer season, and most days of the year the ground is frozen. In such cases, the foundation is poured in winter. The need to complete construction as quickly as possible is an argument for work regardless of the season.
Thanks to special technologies, construction in the cold season has become possible. But it must be remembered that excavation and construction work must be carried out in accordance with special rules so that the construction of the foundation in winter is of high quality and efficient.
Features of winter foundation laying, possible difficulties and ways to eliminate them
During the hardening process of the concrete mixture, a hydration reaction occurs, as a result of which cement minerals, interacting with water, form special compounds.
Dewatering of concrete in early dates can slow down or stop the hardening process, lead to a lack of strength and cause shrinkage and cracking. At sub-zero temperatures, water freezes without reacting with cement.
In this case, the hydration reaction does not occur and the concrete does not harden, which can lead to a decrease in the strength of the foundation and its durability. Water frozen in concrete expands in volume when it freezes, which leads to poor adhesion of concrete to reinforcement and can lead to further destruction of the foundation. Therefore, you need to know how to properly fill the foundation in winter.
Working in winter conditions is more difficult than in other seasons. Special requirements for placing and curing concrete are required. Pouring into frozen soil can lead to subsidence in the spring and the formation of cracks in the concrete, which may require expensive repairs. And despite the savings when purchasing some materials, the price of others will increase. Therefore, there are pros and cons to pouring the foundation in winter.
Let's look at ways to eliminate the difficulties of winter filling.
1. Artificial heating of the area using heating devices.
During the period when the concrete reaches its maximum strength, it is necessary to carefully protect the base of the pour from frost. Along the perimeter of the site, you can install heating devices - heat guns that maintain the desired temperature of the concrete when hardening. This method is quite expensive.
2. Heating using electrical power.
This method ensures the transfer of heat from hot to cold. In this case, it is not the area itself that warms up, but the concrete. An electric current (380 V) is supplied to the reinforcing mesh, as a result of which the metal rods heat up and heat up the concrete. An important condition is the experience and professionalism of workers in order to correctly implement this method.
3. Use of special additives for concrete - modifiers.
Additives are added to the concrete mixture for the foundation, which slow down the freezing process of water and allow the concrete to gain the necessary qualities before setting. Such modifiers allow the concreting process to proceed without heating. The packaging of these additives indicates the frost resistance and hardening speed of the concrete mixture.
Some additives can be used at temperatures of -5...-10°C, and some can reduce the crystallization temperature of water to -20...-30°C.
The price of additives and modifiers that increase the frost resistance of concrete can be high due to the large volume of additives required to pour even a small foundation.
Sometimes the presence of modifiers in concrete is insufficient, then both heating of the concrete and the installation of additional thermal insulation are required to maintain a constant temperature of the structure.
Pouring concrete using special heating elements is extremely expensive due to the fact that it requires high level energy costs, in addition, constant monitoring of the filling cycle by specialists.
Features of pouring the foundation depending on the type
The pile foundation is poured in winter using technology that involves heating and insulating the concrete.
The pile type of foundation is well suited for land plots with soft, loose soil. Such a foundation consists of piles that are immersed in the ground and connected to each other by reinforced concrete beams or a slab. With this arrangement of the foundation, it is necessary to transfer its loads to harder soil rocks. The depth to which the piles are laid depends on the geological features of the site. The best option for installing piles would be soil that freezes to a great depth.
The advantage of metal screw piles is that this type of foundation can be laid in the cold season. The advantage of winter installation is the integrity of the grass cover on the construction site, which will delight the owners with its appearance in the spring. The piles are made of steel, which withstands cold well.
To properly install the pile- screw foundation in winter, you need to do the following:
- make markings and start screwing the piles, having previously made small pits (if you make them to the depth of soil freezing, then screwing will be no different from summer);
- if the ground is very frozen and cannot be drilled, you will have to preheat it with a fire;
- add anti-frost additives to the concrete (the cost of these materials is significant, but you need little concrete for such a foundation, so a small amount of additive will be required).
Let's look at how easy it is to lay a screw foundation in winter:
- Open up the top frozen layer of soil.
- Screw the piles into soft soil.
Unlike a strip foundation, a screw foundation has the following number of advantages:
- time savings associated with the quick installation of screw piles (1-2 days of work);
- cost savings compared to strip laying in winter;
- opportunity to use screw piles with large differences in heights and in the presence of “difficult soils”.
It is also possible to build a strip foundation in winter using frost-resistant additives, but experts recommend constructing it in winter from ready-made concrete blocks, where the mortar is poured only into the connecting seams.
There is a solution for winter laying, depending on what type of foundation you want to build for your house.
Work algorithm
Let's look at a simple algorithm for pouring a foundation in winter.
Preparation of concrete mixture
In order for the structure being built to be completed in accordance with the norms and requirements, the concrete mixture must be prepared before pouring.
The temperature of the components of the mixture for the foundation at the time of loading concrete into the mixer must be such as to ensure its required temperature upon exit. Therefore, when preparing it in winter, it is necessary to heat aggregates or water, and sometimes both together, taking into account heat losses during preparation, transportation and laying of the concrete mixture.
Cement and finely ground additives are introduced without heating. If modifiers are used, they are added to this species supplements according to instructions.
Pouring concrete
To prevent the concrete from freezing and gaining the necessary strength, if there are not enough anti-frost additives, the poured area or the base of the foundation is heated.
Maturing of concrete
To ensure that the concrete matures in accordance with building codes and frost does not damage the top layer, it must be covered with a covering after pouring: an awning or PVC film. Sawdust or other materials are also used to maintain the required temperature when concrete hardens. For convenience, formwork is used, which is dismantled in the spring or in conditions when the development of concrete strength will not be threatened by negative temperatures.
Thanks to heating and the use of special additives, you have the opportunity to pour the foundation for a house at any time of the year, even in winter.
During the construction and design of residential or non-residential buildings, it often becomes necessary to fill the foundation with concrete mortar in late autumn or already winter. When the air temperature drops below 0°C. According to the recommendations of specialists and the concrete manufacturer, the optimal temperature for pouring and hardening the mixture is +5°C. Hence, the next question arises - how to pour concrete in winter without warming up?
Many qualified specialists and construction companies To fill the mixture in the autumn-winter period, special heating systems are used, which are represented by three methods:
- Electric heating of the solution in special bunkers immediately before pouring to an optimal temperature of 50-70°C;
- Electric heating of the mixture using heat guns, which are installed under the greenhouse (awning, film) and directed directly to the concrete surface;
- Electric heating of a poured foundation using alternating electric current, which is passed through specially installed fittings or pre-laid heating wires.
However, if it is not possible to use the above methods, then in this article we will look in more detail at how you can pour concrete in winter without auxiliary heating.
Helpful information
Pouring mortar at sub-zero temperatures has a number of specific nuances. Winter conditions in the construction industry begin when the average air temperature is below +5°C, or when this indicator drops below 0°C during the day.
The main task in the process of concreting in winter is to ensure the hardening of the solution in a humid and warm environment during the entire period of its hardening. In other words, you need to provide optimal conditions for the concrete solution to gain a percentage of strength - at least 60%, which will guarantee the preservation of the structure of the entire foundation and its optimal hardening after the thaw.
The poured mortar must gain its strength in winter, which will be sufficient for full or partial loading of a monolithic structure, as well as for stripping.
Below we provide a table with optimal data on the curing time of the concrete mixture and strength gain.
Important! Concrete can gain strength only if the solution temperature is positive.
During the concreting process, you must first protect the solution from freezing so that the hydration process proceeds normally, and the solution does not gain sufficient strength to ensure optimal ice resistance, and maintain the ability to harden at above-zero temperatures without deteriorating the main properties of the monolithic structure. When presented to the foundation high conditions to dynamic characteristics and frost resistance, then the concrete should be protected from freezing until it gains sufficient grade strength. The percentage of optimal strength gain for a mortar will depend on the brand of cement used, additives, mixture temperature and other conditions.
Special Additives
If you do not have the opportunity to fully heat the concrete, then you need to use special antifreeze additives, which have a number of advantages:
- Accelerate the hardening process;
- Increase the duration of hardening of the mixture;
- Understand the freezing point of water;
- Allow concrete to gain sufficient strength at subzero temperatures.
Anti-frost additives allow the concrete not to freeze until the entire process of hydration of the mixture has taken place. Otherwise, the water will begin to tear apart, freezing the set part of the foundation. Typically, water will rise to the top layers of concrete (which may cause peeling if it thaws and freezes).
Hydration will only occur when water is in a liquid state, and the reaction rate at subzero temperatures decreases rapidly. For this, a frost-resistant additive is used, which also accelerates the hardening and setting process.
Depending on the ambient temperature, the method of pouring the monolithic structure, the requirements for the solution and the method of caring for hardening concrete, the amount and type of additives introduced into the finished mixture will depend.
Concrete heating
The second important factor, if it is impossible to pour concrete in winter without heating, for full concreting is heating the solution. Depending external factors, air temperature, massiveness of the structure, you can heat the water for the solution or fillers - gravel, crushed stone, sand, etc. The optimal temperature for the solution when leaving the mixer should not be more than 40°C, otherwise the concrete will thicken almost instantly. The minimum temperature of the solution when pouring massive foundations is considered to be at least 5°C, and for pouring thin structures at least 20°C.
When the filling of the structure with mortar is completed, it is necessary to cover the entire foundation with a thick film or special insulation materials (foam plastic, sawdust, mineral wool, etc.). You can also additionally insulate the entire perimeter of the formwork.
In order for concrete to gain sufficient strength without heating, the following methods can be used:
- You can burn a fire on the leeward side for 3-4 hours (this method is especially effective at negative temperatures down to -5-6°C).
- As stated above, insulate the foundation using heat-insulating materials.
Conclusion and video
After winter, we carefully inspect everything monolithic structure, pick or tap in questionable places. If defects, peeling, or insufficient complaints about the concrete mixture begin to appear, then it is necessary to contact the plant supplier of the solution and make claims about the quality of the concrete. Good luck!
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If you are building a house yourself, then it is not always possible to choose a favorable period for construction. Sometimes vacation falls in the winter, so you have to look for a way out of the situation. Is it feasible in winter? Yes, but it will be more difficult to do this than in the warm season. There are two solutions to the problem:
- Construction. We are not waiting for spring to come, but are taking the situation into our own hands. We select special solutions, a suitable type of foundation and begin work.
- Preservation of the foundation for the winter. For example, you started construction work in November, but you don’t really want to continue construction. Sometimes this is simply not feasible, so you need to leave the work until spring.
We will analyze both options in detail, since both construction and conservation are complex and time-consuming processes, so it is better to entrust them to professional builders.
We build in winter - types of foundations
For winter construction, there are two main types of foundations that can be used in cold weather:
- Strip foundation. To make the work easier, craftsmen recommend choosing ready-made blocks. “Wet” operations are best left for the warm period.
- Pile foundation. A foundation where concrete piles are used as the main element will be an excellent solution for lightweight structures. Usually pile foundation chosen for wooden houses.
Preparing the concrete mixture
Of course, what to do strip foundation You won’t be able to do it with regular concrete in winter. Here you will need a solution containing special additives. These modifiers do not allow the concrete to harden ahead of time; the mixture sets only after the required strength has been achieved.
Also, “winter” additives make pouring easier. The selection of the right mixture should be done by a professional, since they differ in the speed of hardening and frost resistance. The packaging usually indicates how many modifiers should be in the concrete mixture.
Pile foundation in winter
This type of foundation can be built in all seasons. Builders do not need to adapt to the weather, since installation work it has no effect. Construction proceeds as follows:
- Piles are screwed into frozen soil to the freezing depth. Typically the distance is 1.5 meters.
- The next step is cutting to level.
- Next, the concrete mixture is poured into the foundation.
- Now you can put the heads on the piles.
- If necessary, waterproofing and thermal insulation are carried out.
- Piles help distribute the load evenly over the entire area of the foundation.
Features of the use of additives
Before starting work, you need to familiarize yourself with the main features of modifiers. The solution needs 10-15% less water when compared with a regular mixture. Modifiers perform their tasks up to a certain frost threshold - this is -25 degrees. You also need to monitor air humidity. If this figure exceeds 60%, then additives cannot be used.
We often repeat that a professional should choose a solution and modifiers, because you need to know how the additives will react with a certain type of concrete. Despite the fact that modifiers help cope with frost, you cannot do without thermal insulation. The base concrete should be heated so that the temperature of the structure does not change much. Now let's look at the pros and cons of working in winter.
Positive and negative points
First you should consider the pros:
- The soil does the work of formwork, since the frozen soil does not crumble;
- Savings on building materials. Don't forget that with the arrival of cold weather, stores are trying to get rid of seasonal materials.
- In some regions, the favorable season for construction lasts no more than 2 months, so leaving work for almost a year is the wrong decision. A “winter” pile or strip foundation will help here.
As you can see, there are advantages. Now let's look at the cons:
- Although building materials will be cheap, earthworks will be expensive if you hire builders;
- Some owners decide to leave construction until the warmer months for the reason that it is simply impossible to work at -20;
- Using special equipment in cold weather will be problematic and, as a result, more expensive.
Foundation conservation
Preservation can be carried out in several stages:
- Waterproofing of finished or unfinished foundation;
- Thermal insulation of the foundation;
- Groundwater drainage.
To understand how to leave the foundation for the winter without damage, you need to analyze each point.
Groundwater drainage
Before construction begins, specialists from the construction bureau study the site where the future structure will stand. By examining the characteristics of the soil, you can determine whether it is possible to do without drainage or not. Soil saturated with moisture will not be able to provide the required strength for a house. Due to increased humidity, cracks will appear in the concrete, but the strongest impacts on the structure will be in winter - liquid will get into the pores of the concrete and freeze.
Discharge is carried out using drains and grooves. By performing this action, you will protect the foundation and future home from the adverse effects of moisture. The scheme is as follows:
- Experts find the lowest place on your site.
- Next, a hole is dug, which will later serve as a reservoir.
- It is necessary to dig grooves with a depth of about 40 centimeters along the entire perimeter of the base. The exception will be the grooves on the side of the pit - there the depth should be increased to 50 cm.
- Drains should be dug perpendicular to the ditch, the direction should be towards the tanks.
Waterproofing and thermal insulation
4 weeks after pouring the solution, you can begin waterproofing. It is worth saying that such protection is not needed in all cases. In any case, this issue is resolved when planning the foundation.
You need to have time to do waterproofing before the onset of cold weather, this applies to strip and tile structures. If you choose a columnar or pile foundation, then waterproofing is not needed.
As for insulation, it is carried out along the entire perimeter of the base. The material you can choose is extruded polystyrene foam. It is convenient to work with it, since the material is sold in slabs. Of course, thermal insulation is carried out after waterproofing. After the slabs have been laid, you can sprinkle shavings or straw around the entire perimeter of the base. Next, the foundation needs to be covered with film and pressed down with heavy material. After this, the structure can be safely left for the winter.
Bottom line: is it possible to fill?
As you can see, there are many “Pros” and “Cons” of pouring the foundation in winter, but the fact remains that if necessary, the foundation is poured even in frosty weather. Yes, the work is specific, you need to understand additives so that the output is a high-quality solution. If you are not afraid of the cold, then feel free to get to work.
Is it possible to pour the foundation in winter? updated: February 26, 2018 by: zoomfund