Pouring concrete under special conditions

Many had to deal with a problemperformance of concrete screed, especially in winter. Pouring concrete in winter differs significantly from similar work that is performed in the summer, and requires knowledge of some features.

It is also known from school physics lessons that waterat negative temperatures takes the form of a solid, that is, it passes into ice, which is several times larger than the volume of water. Thus, when pouring concrete in winter in the usual way, the water that enters the solution freezes, which stops the solidification processes and forms breaks in the binder.

Especially harmful for concrete are the differencestemperature. Of course, we can not say that there is no grasping, but with repeated thawing and freezing, pouring concrete into the formwork can give zero result.

How to produce concrete works in cold weather?

Working with solutions to create a screed, inFirst of all, it is necessary to follow the general rules that exist in construction. There are two requirements. Firstly, to create a screed, it is necessary to prepare a qualitative concrete that meets the standards. When delivering it to the site it is better to use a concrete pump. In addition, the builder takes full responsibility for the preparation of the future place for pouring and for the further care of concrete.

That the solution is well hardened, which will ensureabout 75 percent of its strength, it is necessary to create conditions for maintaining the temperature regime. And for a high-quality strong screed, concrete casting should be carried out at a temperature of 10 degrees above zero. Therefore, work on the production of screeds should be carried out in warm rooms that have walls, roof and heating.

When concrete is poured in place withtemperature regime of 5 degrees (this is the minimum figure at which it is possible to work with cement, however, the time of recruitment increases several times), the following actions should be taken. Firstly, additives for concrete or chemical additives (not recommended for screeding) are used to stop the freezing process. Concrete must be poured into the formwork, which must first be insulated. Formwork can be covered with roofing felt, mineral wool, straw, reed, and between the boards to fill slag, sawdust or fill the space with foam. You can use infrared heat sources for heating. In addition, the fillers are heated: water, sand or crushed stone.

It follows that the best way to ensurenormal solidification of the solution and the necessary microclimate is the use of a thermal curtain, as well as the use of a heat generator, if necessary the inclusion of electric or gas heat guns.

It is necessary to remember the rules of using heating equipment. Incorrectly installed heat gun will do more harm, one part of the screed can dry out, and the second - it will freeze.

If the pouring of concrete is carried out under conditions and with constant support (about 4-5 days) of the thermal regime, then its quality can not be worried.

Sometimes it happens that the concrete freezes. Its solidification can be restored by creating a positive temperature (at least 10 degrees). This often happens during autumn frosts. But in this case you can not worry, such colds will not cause significant harm to concrete. Only the upper thin layer can be destroyed.

If the screed is frozen, then urgentlyit is necessary to cover it with a polyethylene thick film so that frosts and thaws do not destroy concrete. In this case, the strength will be somewhat lower, but this only applies to the upper layer.