At what temperature can be poured foundation

From the strength of the foundation depends reliability and durability of the entire structure.When planning such a "zero" qi cells roitelnyh art works, many factors must be considered.Of particular importance acquires information at any temperature can be poured foundation.

If you do not take into account the weather conditions at the time of the foundation of the pouring process, the quality and brand of the solution, the use of additives, which are able to reduce temperature crystallization water, activities on dderzhaniyu necessarymodes for concrete maturation, the work can be carried out in vain, and erected basis building starts to crumble immediately after solidification.

Some owners of suburban areas in a hurry to build on their newfound territory of permanent structures, not paying attention to the time of year.In some rather rare cases, it is justified, however, difficulties with this approach are many, and they start already at the stage of preparatory work.

Preparations for pouring the foundation

Regardless of the time of year preparatory measureswill include a list of mandatory work:

• place where it will get the foundation for the construction of buildings, should be cleaned from the top layer of soil and spaced appropriately.Remove the upper soil layers in cold weather - enough laborious task.
• When the total space will be defined, marking the internal borders of the trench, which is necessary to dig the foundation.Depth it should be between 500 to 800 mm - this value will depend on the type of soil the area where being construction, the depth of frost penetration, features of the building being erected (its number of floors, walls and roof material and etc .) earthmoving equipment for passages narrow and fairly deep trenches with smooth walls can be applied is not always .Manual digging the frozen soil - still one problem during the winter work.
• At the bottom of the excavation trench-laid waterproofing and firming cushion.First stacked sand and well compacted, layer thickness may be from 100 to 150 mm.On it poured gravel and also well compacted.Very often in winter and sand and gravel are "stuck" frost condition.There is a high probability that a rise temperature theft may lose the necessary density, even in the most high-quality compaction.

• In addition, there is no certainty, that a total thawing of soil in the spring and possible at the same time it moves the entire structure erected foundation not « lead », which canlead to the formation of internal stresses and cracks.
• next step is installing formwork boards or wooden boards, which waterproofing thick polyethylene film .In severe frost polyethylene often it loses its elasticity, becomes brittle, and the waterproofing may be damaged.

• can be used and permanent formwork made of extruded polystyrene, which, in addition to its direct functions, performs still and the role of insulation.

• Next, the formwork must install the reinforcing structure which is welded or twisted steel wire.Armature for this design taken thickness of 10 to 15 mm.We must not forget that the reinforcing steel is quite significant coefficient of linear thermal expansion.Brewed in the frost reinforcing cage necessarily seek to change the size with increasing temperature.It - yet another weighty "additive" to unnecessary internal stress design of the foundation.

However, as already mentioned, there are situations where, due to various reasons, the construction of the basement in the winter season is justified:

• This may be due to the peculiarities of the soil.If the area where the construction is carried out, is dominated by sandy loose soil, the better to carry out the construction of the foundation in the frozen solid soil, which retains the right to form the pit.
• should not be discounted accounts impossibility of building in the summer because special climatic conditions of the region.
• In some areas due to poorly developed road network delivery of large volumes of building materials or movement of heavy special equipment possible only by frozen ground.
• Sometimes winter resort construction site in order to save money, as the prices of the required materials are reduced in this period.This will be beneficial in the event that the work will be carried out independently.
• Often it is possible to save the expense of construction companies reduce the cost of services, due to a sharp decline in their activities demand during the cold season.

When all the preparatory processes are completed, it is possible to calculate density and composition of the solution, the parameters of which will depend on the temperature at which it will be poured into the formwork.

Pouring concrete foundation

• Whenever not carried fill, for the foundation of the solution should not be too thin, so it is most often made from cement and medium-sized gravel .
• Often plasticizers are added to the solution, and that improve the strength of concrete, increase its adhesion to reinforcing structures improves moisture resistance of the foundation. In addition, according to the producers, by pouring plasticizers reduce the consumption of cement mortar by 20%.

Due to the plasticizers have a positive effect on the hardiness of the solution, they are very often added in those cases when it is necessary to fill funda nt etc. and negative air temperatures.

• For all recommendations should be made of concrete pouring at a temperature not below 5 degrees - is, in fact, is a critical parameter for the normal maturation.However, and the summer heat is also not well suited for these construction processes.Optimum temperature for pouring the solution into the pit is +15 ÷ 25 degrees.These conditions will provide no extra cost and technological techniques most solid foundation for the construction of the walls and in the shortest time.

What are the general guidelines for pouring the concrete foundation:

• In case solution made yourself right on the construction site, all used to it materials should not be be frozen and should not have his composition of snow or ice crystals.Therefore it is better to buy them in companies that guaranteed to provide them with proper storage.
• solution is necessary to fill and distribute formwork quickly to the frost did not have time to grab moisture in the solution.Therefore, fill the entire volume concrete is produced in such conditions only once.If the foundation has a large volume and area, it is best to use offers specialized firms that engaged in the manufacture, delivery and unloading of the required solution in the prepared formwork.

• not recommended to carry out the pouring of concrete layers, as between them, thanks to the low temperatures, can form cracks that make the foundation less durable.

If circumstances were such, that have to carry out work under extreme temperatures, you need to know, that setting and hardening processes will be increased by several times.Therefore, fill the basement in the winter is carried out only if absolutely necessary.

Below is a table from which clearly shows the effect of ambient temperature on the ripening time and a complete set of the required strength of conventional concrete solution brand M200 - M300, manufactured on the basis of Portland cement M-400 or M-500.

concrete hardening period, days	-3 ° C	0 ° C	+ 5 ° C	+ 10 ° C	+ 20 ° C	+ 30 ° C
1	3%	5%	9%	12%	23%	35%
2	6%	12%	19%	25%	40%	55% *
3	8%	18%	27%	37%	50% *	65%
5	12%	28%	38%	50% *	65%	80% **
7	15%	35%	48% *	58%	75% **	90%
14	20%	50% *	62%	72% **	90%	100%
28	25%	65%	77% **	85%	100%	-

Notes:

- percentages calculated in proportion to the strength of the reference concrete matured this brand.

- under the icon (*) are listed so-called conditional regulatory safe timing of stripping drenched concrete structure.

- icons (**) - a maturation time to initiate a fully secure future work.

To provide the required minimum allowable temperature conditions using several technologies:

• percent ss etc. gadfly with warming reinforcement design or the installation of special heating cables.In this case, the foundation should be corresponding voltage is supplied.There are several technologies, such as with the use of high voltage currents (up 380 volts ) and low current ( 12 volts ).Having warmed up, reinforcing structure or the heating cable will not give smerznutsya wet, grabbed solution.

However, such methods are justified only for large-scale industrial construction - these technologies are very dangerous and require highly qualified specialists.In addition, no small importance will be the expenditure of large amounts of electricity, and then will have to pay a hefty sum.As a result, the total budget of the arrangement of the foundation is unlikely to be acceptable to the average Russian private developer .

• You can also use other technology - use it for the foundation of a non-removable device insulated formwork.

For this method used hollow blocks made of extruded polystyrene, which is conveniently placed on each other, thanks to the existing teeth on the side and upper surfaces .They are perfectly combined with each other without leaving gaps (an analogue of «Lego» Children's Designer ).In the interior of the set reinforcing structure, which gives the foundation required total stiffness .

Styrofoam from the foundation are not removed, and after the concrete has set, the surface is delayed reinforcement mesh-serpyanku, plastered and waterproofing .

However, this approach only reduce the negative impact of freezing temperatures during the maturation of the concrete, but not remove the problem completely.

• In any case, for a reliable setting flooded basement in sub-zero temperatures on top of it always closes tightly with plastic wrap .To this end, erected over it temporary constructions of wood or reinforcing rods, which also tightened polyethylene.In the resulting enclosed area that looks like a greenhouse, the necessary support for high-quality hardening temperature using heat guns.It is clear that this will require a very significant material costs.

As you can see, even from an economic point of view work on pouring the foundation in winter causes great concern.Therefore, before starting this kind of work during the cold weather, you need to very carefully weigh the financial risks and the justification for such haste.

Video: work on "winter" laying the concrete foundation

Are the "panacea" antifreeze additives?

There is a very widespread opinion that the problem of winter pouring the concrete foundation may well be solved using a special salt additives in the solution being prepared.Judging by the numerous advertisements, it should be added that assembles nt etc. and kneading, and then everything will its course With this is to understand in detail.

Video: one option antifreeze additive in concrete

First of all, you must understand how, in fact, there is proce ss tv Erden and concrete blocks maturation.

When the solution is poured into the mold, it runs until cooked through two stages - this setting and hardening.

• grasp poured concrete for 24 ÷ 30 hours.During this time the liquid consistency becomes solid state, however, it still does not have sufficient strength.It was in this period begin to form crystalline communication , binding occurs free water and cement solution components.
• Then begins the second phase - this final curing, maturation and hardening of the concrete structure - he runs for much long term.This period depends on several factors, such as the brand prepared solution, the level of humidity and temperature, as well as the availability of special uprochnitelnyh additives.

As mentioned above, the optimum temperature for the chemical reactions of both processes vary from 15 to 25 degrees.The higher it is in this range, the faster host final crystallization transition gelled water.Even under optimal conditions about the readiness of the foundation can say no earlier than 4 weeks - the basis is completely ready for the erection of walls.

danger lies in the negative temperatures of several reasons:

• Firstly, the expansion of the frozen unrelated cement water causes internal pressure to the porous structure of concrete, which leads to its destruction.