The temptation to pour a foundation in winter is incredibly strong. Building materials for the foundation, as well as labor, are much cheaper at this time than in the summer, and any person has much more free time.
However, many people are afraid to start construction in the cold season, since there are a number of concerns that are associated with possible destruction of the structure, poor hardening of solutions, as well as preliminary wear and tear of some building materials.
Pouring a foundation during frost is a truly labor-intensive and complex process, but at the same time, it is possible to implement. Those wishing to start construction in winter should be prepared to work in conditions of low air temperatures and carefully select technologies and materials.
Pros and cons of winter foundation pouring
Advantages
- Pouring the foundation in winter is justified when the building plot has very “fragile” soil. Frozen soil retains its shape well, so work here is usually carried out in winter.
- Pouring the foundation in the cold season is justified by construction in the northern regions.
- Low price of building materials and labor.
- In winter, people have more free time.
Flaws
- If workers can dig a trench under the foundation in the summer, then in winter it will be necessary to use special equipment to cope with the frozen ground.
- There is a risk of buying low-quality materials that suppliers have not been able to sell for a long time.
- Work in fairly harsh conditions.
Features of winter filling
To ensure the reliability and strength of the foundation of a country house when pouring it in winter, certain rules must be followed. First of all, you cannot carry out work in parts with very long periods of time between each individual pour. The concrete solution is laid in small segments, quickly covering them with the next layer. You also need:
- It is good to clear the prepared trench of snow and remove any ice that has formed from the bottom of the ditch and the reinforcement.
- Cover the pit with special insulating material.
- Warm up the bottom between all the walls of the formwork in advance.
- Provide full access to the formwork.
It is impossible to pour concrete on top of frozen soil, since when it thaws it will settle and may well become the main cause of subsidence of the foundation.
Pouring the foundation depending on its type
- Strip foundation. This option is the most popular among developers. The disadvantage of pouring the foundation in winter is low labor productivity. Workers need to rest more often, and some operations require much more time than in the summer. Experts advise, as far as possible, to reduce the number of “wet” operations. For example, the use of ready-made concrete blocks. They are delivered directly from the factory and placed in a finished pit. For the blocks you will need just a little bit of concrete mortar, which means a significant reduction in “wet” work.
- Ready-made concrete piles. If the planned building is lightweight, then you can use pile technology. This type of foundation is very popular among timber houses. By following the rules of construction, you can build a reliable and durable pile foundation in winter, which will not be inferior to other types of foundations. Concrete piles are divided into two categories: bored and drilled. The first ones are made by pouring concrete into drilled wells, while drilling ones are driven into the ground. The second category is much faster and more convenient, since piles can be purchased from the factory without having to make a solution. But the disadvantage of these piles is their price and a lot of noise at the moment of driving the piles into the ground. The solution to the problem is the use of screw pile technology. Today this technology is very widespread and popular in the construction market.
How to pour a foundation in winter?
Algorithm for pouring a foundation with concrete in winter:
- Excavation. Digging in winter is difficult, so we use an excavator.
- Formwork. This is done in the same way as in the summer. Shields are assembled from boards 20 mm thick and supported with special spacers.
- Mixing concrete. First you need to mix water with an additive and a plasticizer so that it does not freeze. Then add crushed stone and sand. Proportion 1:3.
- Filling. Before pouring the foundation in winter, it is advisable to choose a day without wind or precipitation.
- Insulation. We cover everything on top with polystyrene foam and press it down with bricks so that frost does not hit the cement. Very low temperatures can easily damage the top layer. In severe frosts down to -20C, uncured concrete is completely safe. More than -20C is dangerous, you need to withstand it until this time for at least one or two months.
- Waterproofing. If spring waters are just around the corner and the concrete has not hardened, it is necessary to isolate it from water in any way. Inside the pit, you can dig a hole to collect sediment, and then pump out all the water, you can spray bitumen, and bolt the roll waterproofing.
The work methods used by professional builders are being improved. New technological techniques reduce the duration of construction activities, increasing the quality of constructed structures regardless of climatic conditions. Until recently, developers, pondering whether it was possible to fill the foundation in winter, gave a negative answer. Now the approach has changed - technology allows concreting in winter, guaranteeing the quality of concrete.
Different approaches to the question of whether pouring concrete in winter is possible
Discussions periodically arise between builders about the possibility of carrying out concrete work at temperatures below zero degrees Celsius. There are two positions:
- supporters of traditional methods are confident that cement hydration can only occur at positive temperatures. They deny the possibility of using special techniques and believe that in winter the strength of concrete is lower and it is preferable to pour concrete in the fall;
- adherents of the latest technologies do not doubt the effectiveness of proven know-how. They believe that it is possible to concrete the foundation in winter, regardless of the level of temperature decrease, and at the same time ensure the strength characteristics of the foundation.
Each opinion is based on certain views and experiences. Let us dwell in detail on the features of performing concrete measures in cold climatic conditions. The main task is to prevent water crystallization. After all, frozen ice crystals increase the porosity of the mass and create an obstacle to the hydration of the concrete mixture.
Pouring the foundation in winter is quite feasible
Pouring the foundation in winter - how hydration proceeds
Provided that special methods are used, involving the introduction of additives or heating of the solution, the hydration process in winter and summer is no different.
It provides the following stages:
- formation of a surface film based on sodium salts;
- absorption of water by the binder in the outer layer of the massif;
- contraction of the outer layer with a simultaneous increase in density;
- stopping moisture absorption and further increasing hardness.
The concrete mass acquires operational hardness gradually:
- The initial setting of the solution lasts no more than 24 hours. The liquid mixture hardens, but it is not strong enough to carry out further work;
- the final set of hardness occurs within 28 days. Duration is affected by weather factors and recipe.
The construction of the foundation in winter has its own characteristics. As a result of crystallization, water freezes in concrete pores, which impairs the strength of the mass. The main requirement when pouring concrete in winter is to create a solution temperature favorable for hydration.
Pouring the foundation in winter - methods used
By maintaining an optimal temperature, builders ensure the required duration of concrete hardening.
Winter foundation installation is the only way to speed up the pace of construction of structures in a harsh climate zone Various methods are used for this:
- steam heating;
- heating with electricity;
- directional heating by an infrared source;
- temperature increase by induction radiator;
- protection of concrete with a thermal tent;
- insulation of the massif with heat-insulating formwork;
- introduction of additives that prevent water from freezing.
Let's look at the features of popular technologies.
Using steam heating
Hot steam can deeply heat concrete and create favorable hardening conditions. Heat treatment of concrete for 24–36 hours with steam heated to 75 ⁰C is equivalent to gradually settling the concrete for half a month at a positive temperature.
The duration of processing is determined by the following points:
- the required hardness of the monolith;
- the brand of Portland cement used;
- heating intensity.
Heat treatment is carried out by creating a steam jacket. It is constructed near the surface of the formwork and allows steam to flow unhindered around the concrete.
This is a rather labor-intensive and costly method, as it involves heating the trench, pit or concrete to a higher temperature. Application of electrical energy
With the help of electricity, it is possible to provide normal conditions for hardening. The following methods of increasing temperature are popular:
- the use of a heated cable of the PNSV brand, which, after installation, is filled with concrete mixture;
- the use of electric heating from a step-down transformer through electrodes inserted into the array.
The electrode heating method does not require significant costs and provides for the possibility of using various conductive elements:
- stretched wire. A vertically positioned string is effective when concreting elongated structures in the form of support columns or load-bearing beams;
- reinforcing bars. Depending on the size of the concrete products, the rods are immersed in the solution to the required depth and cannot be reused;
- metal plates. Plate electrodes are placed on oppositely located formwork panels, ensuring direct contact with the solution.
The greatest effect is provided by the use of a heating cable. The technology allows you to regulate the heating intensity of the wire that transfers thermal energy to the concrete mass.
This method can be carried out at any temperature and weather conditions. The following heating methods are less popular in the construction industry:
- infrared;
- induction.
They have serious disadvantages associated with increased energy intensity, complexity of implementation, and uneven heating of significant volumes of concrete.
Construction of a thermal “jacket”
Construction of an easily erectable tent with internal heating is an economically feasible method. Main elements of the tent:
- power structure made of durable metal profile;
- covering made of polyethylene film or tarpaulin material.
Heating inside the structure is carried out using the following equipment:
- heat guns with autonomous power supply;
- portable stoves using various energy sources.
This method of construction is very well suited for all weather conditions, even the most severe frosts Heating of formwork panels
Warming up the formwork panels is also used to maintain the temperature regime. It is based on the formation of thermal insulation cladding based on the elements of the formwork structure.
Various coolants are used:
- water vapor;
- Electric Energy;
- hot water.
The heating circuit is formed from hermetically connected lines that transfer thermal energy to the solution. This method has weaknesses:
- uneven evaporation of moisture from concrete;
- the appearance of cracks in the heating zone.
At the same time, situations are possible when heating the formwork is the only possible method of maintaining the temperature.
Is it possible to pour the foundation of a cottage in winter?
The financial capabilities of private developers do not always allow the use of industrial heating methods. After all, it is problematic to purchase or rent special equipment, as well as maintain the required temperature throughout the day.
As you can see, pouring the foundation in winter has its advantages That is why quite simple technologies are used when constructing private buildings:
- heating the concrete mixture during the preparation stage;
- introduction of frost-resistant modifiers into the solution.
Using these techniques, you can concrete the foundation of a private house in winter.
How can you increase the temperature of the mixture yourself?
It is easy to increase the temperature of the concrete solution on your own, observing the following rules:
- Heat the water to 75–80 degrees Celsius.
- Mix it with aggregate.
- Add cement to the mixture.
- Stir by adding hot water until the solution reaches the desired consistency.
After pouring, use a vibrator to eliminate air pockets.
The use of additives to increase frost resistance
Frost-resistant additives, which prevent water crystallization, make it possible to carry out winter concreting without the use of energy-intensive heating processes.
Today in the construction industry various types of additives are used to improve the quality of concrete and its hardening. To ensure the desired effect you must:
- study the manufacturer's instructions;
- analyze the compatibility of components with the materials used.
Independent use of additives does not cause difficulties for private developers.
Preservation of the foundation for the winter
Private developers are interested in whether it is necessary to cover the foundation for the winter, and also when to close the vents in the foundation for the winter. Preventing a newly poured concrete foundation from overcooling helps increase its strength. In this case, sealing of the vents should be carried out before the onset of the first frosts.
Preserve the base in stages:
- Waterproof the base. Waterproofing the foundation in winter is carried out 30 days after concreting and involves covering the surface with polyethylene or roofing felt. When aquifers are located close together, a drainage system is constructed.
- Insulate the surface. Thermal insulation will allow you to maintain favorable temperature and humidity for a long time, eliminating the influence of temperature changes. Expanded clay, expanded polystyrene, sand, sawdust or straw are used as insulation.
It is important to reliably cover the heat insulator with polyethylene and secure the film with heavy objects.
Conclusion
Not all winter concreting options can be used by private developers. Study the technology thoroughly and perform an economic analysis. Only then choose the optimal method. In addition, there is another option - wait for warmer weather and save money.
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. Typically, pile foundations are chosen for wooden houses.
Preparing the concrete mixture
Of course, you won’t be able to make a strip foundation in winter from ordinary concrete. 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 it does not affect installation work. Construction proceeds as follows:
- Piles are screwed into the 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;
- Saving 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 warmer weather 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 most severe impacts on the structure will be in winter - liquid will enter 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
With the onset of winter, concreting is much more difficult, and most importantly, such work requires careful preparation and full compliance with all construction regulations. When pouring a foundation into frozen soil in winter, you should be prepared for the fact that in the spring the ground will thaw and sag, and the foundation will crack, which will entail...
But sometimes life makes its own adjustments. The estimated time for work is disrupted, and the foundation, which was planned to be poured in the summer, needs to be built when the thermometer drops below zero.
You can take a chance and try to create a reliable foundation for yours in adverse weather conditions! The experience of site users suggests that during such construction the main thing is to arm yourself with knowledge and not leave anything to chance!
Pouring the foundation in winter
Forum user with nickname AlecScrab The builders proposed pouring the strip foundation in winter, in December, so that it would set by spring, and in March they would begin to raise the walls. They promised to significantly reduce the prices for their work, because... Now is not the season, and they have few orders.
Needless to say, the offer is tempting, but the forum member is haunted by the question: at sub-zero temperatures, and whether this will further affect the strength of the strip foundation.
Profanus:
– Concrete gains strength in 28 days, but this is at “plus” temperatures, and at negative temperatures concrete may not gain strength at all.
The forum member’s verdict is this: pouring the foundation in winter is beneficial only for builders, because... they want to make money. And for himself, he would never pour the foundation in winter, even with serious benefits.
If the air temperature during the day drops to +5°C, and at night the thermometer drops below 0°C, then such construction conditions are considered winter.
During winter construction, the foundation must be poured using antifreeze additives and a special technology for warming the concrete. And this leads to a significant increase in the cost of construction estimates. The rise in price may completely offset the benefit from the seasonal reduction in prices for construction workers.
According to 44alex, If you pour concrete in winter in compliance with all the technology, it will work out cheaper if only the workers work completely free of charge.
The cons of winter monolith
According to a forum member with the nickname Greenpeak, It is not worth constructing a monolithic foundation in winter because:
- additional costs for concrete are required;
- special requirements for laying and curing concrete are required;
- electrical heating of the concrete (or other heating) is required under constant temperature control;
- short winter days lead to additional costs for lighting the site and insulating the shed for workers who are not eager to work in the cold;
- You can run into a large number of low-quality materials.
Emelya:
– At first I also wanted to pour the foundation in winter, but, looking at the ordeals of my neighbors who poured their slab last year in December at -5 C, I changed my mind. Now they have pieces of concrete peeling off the edge of the slab and falling off. The top layer was apparently caught by frost, but it crumbles underfoot.
Hydration reaction
To understand what the technology of winter foundation pouring is and how much the complexity of such work increases, it is necessary to consider the processes that occur in concrete when it is poured at subzero temperatures.
During the hardening process, hydration reactions occur in concrete, during which cement minerals, interacting with water, form new compounds. Dehydration of concrete in the early stages can slow down or stop the hardening process and lead to a lack of strength, as well as cause shrinkage and cracking.
At sub-zero temperatures, water freezes without having time to react with cement. Therefore, the hydration reaction does not occur, which means the concrete does not harden. The strength of the foundation and its durability are also significantly reduced. Water frozen in concrete expands in volume, the coefficient of adhesion of concrete to reinforcement decreases, which leads to further destruction of the foundation. Therefore, building a foundation in winter requires careful adherence to complex pouring technology.
Therefore, most developers are distrustful of winter concreting. However, if you approach the matter wisely and arm yourself with the necessary knowledge, you can pour a high-quality foundation even at subzero temperatures. And sometimes this is the only way out.
How to make a shelter for heating a foundation
Forum member's foundation Svetoch – shallow tape for a house 10x10. He only managed to dig a trench and began tying the reinforcement. I wanted to pour the concrete in the middle of the week (with anti-frost additives, since at night it has long been a minus). And then it turned out that weather forecasters were promising rain and snow. The forum member was worried whether it was possible to leave the dug trench with formwork, a partially filled foundation and reinforcement for the winter.
Costeapechnik:
– If you leave everything as it is, the reinforcement will rust and the base of the tape will burst! The foundation must be poured completely, and rain and snow are not a hindrance, the main thing is to take care of the concrete after pouring.
Forum user with nickname Georgespb understands how to make a shelter for pouring a foundation and what type of shelter for heating a structure is the most reliable.
motorist:
– The shelter is made like this: a large tent is erected over the perimeter of the foundation, a heat gun is installed in it, and the temperature inside rises to positive.
Required gun power depending on outside temperature
Concrete is also heated using electricity - a welding transformer connected to the fittings.
For this, there are special transformers for heating concrete products: current is supplied through electrodes placed approximately 40-50 cm apart in the foundation.
But this method of warming up requires special attention!
sem2005:
– An experienced technician is needed to install the electric heating correctly and ensure that the required temperature is maintained.
This method of heating concrete increases the likelihood of electric shock to workers. That is why, in order to avoid accidents, it is necessary to use a transformer with a voltage of 36 volts. Overheating of concrete is also fraught with severe cracks, and underheating can lead to freezing.
Antifreeze additives
For concrete with antifreeze additives, the strength at the time of its cooling to the temperature for which the additives are designed must be at least 30% of the design for grades up to 200, 25% for concrete grade 300 and 20% for concrete grade 400.
For concrete without the use of antifreeze additives for monolithic structures and the monolithic part of prefabricated monolithic structures, the strength at the time of freezing should be:
- not less than 50% of the design value for concrete grade 150,
- 40% – for concrete grades 200–300, 30% – for concrete grades 400–500,
- 70% – regardless of the brand of concrete for structures exposed to freezing and thawing.
If antifreeze additives are used, this ensures the process of cement hydration and concrete hardening, but at subzero temperatures these processes proceed slowly, and in this case the concrete gains critical strength after about a month of hardening in the cold.
Concrete that has reached critical strength by the time of freezing acquires the required design strength only after thawing and maintaining at a positive temperature for at least 28 days! This means that it is necessary to maintain a positive temperature of the covered foundation not only during concreting, but also after.
To summarize, we can say that pouring the foundation in winter and at sub-zero temperatures leads to an increase in the cost of the estimate and requires careful monitoring at all stages of work. In return, developers get the opportunity to speed up construction work and prepare the foundation for the house in advance before the start of the spring construction season.
FORUMHOUSE tells you what temperature to maintain at. You can also read about.
Here you can find the most complete and detailed information about. How to pour what its decent quality depends on - a heated discussion of a “cold” issue.
This video talks about the nuances of reinforcing shallow
Not so long ago, with the onset of frost, construction was also adopted to “freeze” in our latitudes. Moreover, no one undertook to start it. There could be no talk about the construction of concrete foundations and reinforced analogues if the thermometer warned of a drop below +5º C during the daytime, and at night stated negative temperatures. However, the length of the 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. This is how methods have emerged through which a durable monolithic foundation can be built at low temperatures. Having figured out how to pour a foundation during a difficult frosty period, you can safely begin building a bathhouse in winter.
The nuances of concreting in winter
It is not for nothing that winter was considered not the best period, both for pouring a monolithic structure and for constructing supporting elements of bored and pile types of foundations. The reason for this is the crystallization of water, one of the main components of the concrete solution. By turning into ice, water not only interferes with the normal course of the hydration process of the concrete mixture - that is, the formation of reliable molecular bonds due to its work. Due to the formation of ice crystals, the dimensions of which increase the initial volume of water by 10%, porosity increases. This fact in no way contributes to obtaining the planned strength of the foundation, but significantly reduces it.
Let's understand the mechanism of hydration
Concreting is the process of gradual transition of a mixture of cement with sand and crushed stone from the liquid phase into the solid stone state assigned to it by rank. At a temperature background of + 15º and at a humidity level favorable for setting, the following occurs:
- first, a kind of sodium hydrosilicate shell is formed on the surface of the poured structure;
- then the upper layers of the poured mass are involved in the reaction - the hard grains of cement gradually suck out the moisture, due to which the components of the solution “stick together”;
- then the outer shell, losing evaporating water, begins to shrink;
- then deeper layers react;
- and further in the same sequence until after 28 days the concrete structure gains maximum strength.
If the foundation has to harden on a hot, dry day, the rate of hydration increases. But the water also begins to evaporate more actively, leaving in its place pores unfilled with bound concrete. At low temperatures, the reaction slows down, but pores appear due to the formation of ice crystals. To avoid this, the foundation is poured in winter according to special rules that make it possible to obtain the temperature of the solution required for normal hardening inside the poured concrete mass or individual pillars.
Hydration is accompanied by a spontaneous increase in temperature. The greater the thickness and dimensions of the concrete structure, the more heat the concrete generates and the slower it cools. Therefore, you should not get carried away with pouring support pillars in cold weather; it is advisable to prefer tape or monolith. If you install heat-saving formwork from insulating mats or slabs around massive structures, with minor drops in temperature you can do without additional tricks.
Classification and analysis of concreting methods
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. Options for solving the problem of maintaining or creating the conditions necessary for normal hydration depend on:
- on the dimensions of the structure;
- on the chemical composition of the concrete mixture and on the proportions of the components;
- on the brand of binder cement and the fineness of its grinding;
- from climatic nuances;
- from the ability to heat water and filler.
Often the heat released during hydration is not enough to create the conditions necessary for concrete during the frosty period. Finely grinding the cement helps to slightly increase the temperature, due to which it reacts faster and releases more heat when combined with water. Heating the water and aggregate before mixing also helps.
Attention. Only water and fillers can be heated. Cement cannot be heated, otherwise it will lose its binding properties.
Usually in our latitudes, for winter pouring, a solution with a temperature above 21º C is not used, given that when moving from a concrete mixer to a place, it will release 4.5-5º C to the atmosphere. To obtain the working temperature of concrete, it is enough to heat the water to 32º. At temperatures above the specified value, hot water is first mixed with aggregates, then cement is added in portions.
Increasing the mixing period will help maintain the temperature of the solution. Thoroughly mixed concrete will quickly take its positions in the formwork and will cool less along the way. Therefore, builders recommend increasing the mixing time of concrete mixture components by 25% to optimize fluidity and using finely ground cement.
The simplest heating of concrete mixture
An option with separate heating of water, aggregate or the entire mixture in a concrete mixer by installing a brazier, a heat gun, or a gas burner next to it is suitable for those who are puzzled by the question of how to fill the foundation in winter with light frosts at night and positive thermometer readings during the day.
This scheme has strict rules:
- heating water max up to 80º C;
- initial mixing of water with aggregate and subsequent gradual introduction of cement, preferably with M from 400 to 500;
- the use of additives that increase the hardening rate.
Advice. The use of a vibration device is not a necessary condition for private buildings, but desirable. A construction vibrator is needed to compact the concrete mixture, reduce air content, and reduce porosity.
After pouring, the concrete mass is immediately carefully covered with tarpaulins, bags, insulating mats, slag felt blankets or straw. Until strength gains, the temperature must be maintained by installing braziers or other heat-generating devices around the foundation. Then the heating is stopped and the formwork is dismantled. If the concrete cannot be fully cured, it can be allowed to freeze. All processes will be preserved, and after defrosting the reaction will proceed as usual minus the period between freezing and reverse action.
Attention. Stripping is carried out only after sufficient strength has been gained. According to SNiP III-15-76 regulations, the structure must gain 70%, regardless of the grade of concrete without additives.
Typically, “unfrozen” foundations built according to the rules do not lose more than 5% of their design value in strength properties if the water-cement mixture ratio was no more than 0.6.
Mixing concrete in frosty conditions is a difficult task. A justified decision by a reasonable owner would be to turn to the services of builders or purchase a ready-made solution with modifying additives at the factory. There the proportions will be calculated and weather conditions will be taken into account. With a ready-made solution, solving the question “how to properly fill a foundation with your own hands in winter” will no longer be an impossible task.
Use of concrete with modifying additives
The introduction of antifreeze additives into the solution is also aimed at increasing the thermal energy generated by the concrete itself. In addition to this stimulating effect, modifiers lower the “threshold” for water crystallization. Due to this, the hydration of concrete will take place according to the usual scheme at a temperature lower than for standard conditions.
In order to develop anti-frost properties, concrete is enriched mainly with calcium chloride. No more than 2% of the total mass can be added to the solution, otherwise the compressive strength of the concrete structure will significantly decrease. When the thermometer readings are stable below zero, the solution is mixed with sodium chloride (ordinary salt), potash, sodium nitrate, which ensures trouble-free concreting at -15º below zero. Despite the availability of additives, craftsmen looking for methods on how to pour the foundation for a bathhouse in cold weather should not experiment with solution formulas. It is better to purchase a ready-made composition without the risk of irretrievably losing all the money invested.
When using anti-frost modifiers, you can begin dismantling the formwork when:
- a solution with M200 will gain 40% strength;
- concrete with M to 300 will gain 30%;
- concrete marked M400 and above will gain 20%.
Most often, the use of concrete with modifiers is combined with artificial heating methods. When combining improved concrete, for example, with electric heating, it is necessary to take into account that urea will decompose at + 40º C, and due to potash heated to 30º, the strength will be reduced by 30%.
Technically complex methods of winter concreting
Let us briefly consider methods of artificial heating of concrete in formwork, the purpose of which is to increase the rate of setting of the mixture. Depending on the possibility of using electrical appliances, the availability of insulating materials and the financial framework of construction, the owner of a country estate can choose, or rather, order from a construction organization:
- concreting using the thermos method. Leakage of thermal energy and cooling of the body of the concrete mass are eliminated by the insulating sheathing constructed around the formwork. It is a metal casing with an electric, steam or water circuit that heats hardening concrete;
- pouring the foundation with steam heating. To implement concreting with steam heating of the solution, you will need powerful equipment and a considerable amount of water. It is necessary to accurately calculate the number of pipes installed in the formwork and build a pipeline supplying steam, which will forever remain in the body of the structure. Due to the considerable cost and complexity of implementation, few private owners prefer steam heating.
- installation of a greenhouse around a poured foundation It’s also not the cheapest way, because you need to build a large tarpaulin or plastic tent. It is necessary to maintain a constant temperature inside the tent and monitor the humidity so as not to dry out the concrete. The greenhouse is heated with portable stoves, cannons, and electrical equipment. A separate project is created for the construction of the greenhouse; it is dismantled after the formwork is removed.
- concreting with electric heating, carried out by starting current through wires with a steel core located in fresh concrete. The formwork or reinforcement structure is “entangled” with a wire with a calculated pitch, or the heating cable is simply laid in the concrete. Compared to the above options, this is the most economical and easiest to implement method, and therefore the most common.
- infrared and induction electric heating options, arranged by analogy from tubular heating elements, carborundum rod emitters or cables that create magnetic fields in reinforcement or steel formwork.
All of the methods listed do not belong to the category of work that should be undertaken without knowledge and qualifications. You need calculations of the amount of energy supplied, design of additional devices, and also the skills of a good electrician for electrical methods.
General rules to follow
Let's start with the fact that everyone who wants to know whether it is possible to fill the foundation in parts in winter conditions will probably be disappointed with the answer. A definite no. And until the filling is completed you will have to work around the clock. Laying should be done in segments that are small in height and length, immediately covering them with the next layer to avoid temperature loss. If for some unforeseen reason a helium shell begins to form on the surface of the poured concrete, it must be chipped off.
It is important to properly prepare the object for pouring:
- clear the pit or trench of snow, chip and remove ice from the bottom and from the reinforcement. To prevent freezing and icing of the bottom, you need to cover the trench or foundation pit with straw immediately after digging and laying the sand cushion;
- warm the bottom between the walls of the formwork approximately 30 cm. Do not pour concrete on top of frozen soil! Thawing under the mass of the solution, the soil will settle. It is not a fact that the settlement will be uniform. Moreover, there is no certainty that the foundation will not sag too much;
- provide access to the formwork from all sides.
There are few rules for safe, effective concrete pouring in winter, but they must be strictly followed. It is much easier to be diligent before pouring and during the process than to waste time and money on dismantling and alterations.
How to properly fill a foundation in winter with your own hands: work rules
Anyone who wants to economically and reliably build a solid foundation for a bathhouse at a time when the cost of building materials is affordable should learn how to pour a foundation in winter.