The curing of concrete is accompanied by chemical reactions, which are significantly influenced by the presence of water. In the mass when diluting the concrete, a sufficient amount of liquid is added to provide hydration. In order for this process to continue until the concrete has completely solidified, it is necessary to replenish the water reserves or take measures to preserve them. It is based on the care of concrete after pouring to maintain a moist state for a set time to prevent moisture absorption by the soil surface or formwork and its evaporation. It is also possible to systematically wet the plane.
Concrete is heavy GOST 26633 2012, which has a composition of slow-hardening cement, is kept in a moistened state for at least two weeks. A shorter time is required for cement with a fast hardening, but in this case the work is done more carefully.
Wet concrete has a lower temperature, compared to conventional. This factor is relevant for alumina material, since a decrease in its strength is observed almost in two times when the temperature threshold is exceeded at 32 ° C.
Regulation of maintenance of concrete SNiP 3.01.01-85 is regulated. All methods of regulating the humidity and temperature regimes are established by the project of the facility.
Features of summer care
The main task of surface care in the summer is to prevent drying out. The formation of a humid suitable regime has simple rules requiring systematic execution. Solar direct rays and wind adversely affect open surfaces, so they must be protected from them. Used for this are waterproof coatings, for example, tarpaulins or burlap. Polyethylene film can also act as a material to prevent drying out. It helps to prevent the emergence of such questions as: "Why does the concrete crack and there is a saline attack?"
In the absence of special coatings, the surface is watered a few hours after the work is completed or sand is poured. The frequency of watering is affected by the surrounding conditions, but, regardless of them, the coating should be permanently wet until the concrete gets most of the established strength. It is possible to use a hose with a spray gun for irrigation.
Under the condition of high temperatures, before the beginning of work on concreting, formwork is also poured. If it is removed before the care of concrete is completed, it will be necessary to moisten the decoupled vertical planes. For regions with a hot dry climate, it is rational to use a system with small holes for watering vertical surfaces with a sharp slope.
Other negative factors
The quality of the laid concrete can be affected not only by heat, but also by groundwater. To avoid aggressive influence, a layer of insulation or water disposal is arranged. Such work is carried out for alumina cement for three days, and for 10-14 days for other species.
A significant content of salts in water can complicate the watering of the structure. After evaporation of the liquid, the salts remain on the material and lead to a decrease in the strength of the concrete. In such a case, only the coating that is placed a few centimeters from the structure is watered. Vapors moisten the mixture, while the salts remain on the cover material.
To protect and moisten the concrete mixture, considerable time and effort is required. Therefore, often used bitumen and paint formulations, polymer protective films for surfaces with a large footprint, provided that there is no further contact with the concrete.
A special moisture regime is required for lightweight cement elements with porous type fillers. Concrete maintenance in summer is carried out with the help of coatings made of film and paints protecting from moisture ingress.
Work at low temperatures
Naturally, if there is a choice of time for concrete works, it is better to give preference to the summer months. But if concreting has to be carried out in winter, special actions are needed to protect the material from freezing before it gains proper strength.
When preparing the solution without adding special modifiers, it is necessary to heat the water. In this case, continuous laying should be carried out. Frozen top layers should be treated with steam and removed, after which the work on pouring is immediately continued.
In winter care for concrete is the following:
- Subject to the boundary temperature range, the building is insulated using insulating materials.
- Transformers with high power are used to heat the solidifying base.
- A light type of material or heavy concrete is used, the GOST of which provides the presence of antifreeze additives.
The creation of a thermal normal mode is possible with the help of a "tent" with simultaneous heating by a heat gun. It is worth noting the undesirability of electric heating for thin-walled elements, as this can lead to overdrying. The way out of the situation is the use of steam heating or infrared heater.
Modern designs provide sufficient protection against drying, the remaining open planes should be sheltered immediately after pouring in dry weather.
To ensure that the timber formwork does not absorb moisture and ensures high-quality hardening of concrete, its inner surface is pre-coated with a special oil composition. It will not be superfluous to systematically spray outside, especially in hot weather.
For small structures, increased protection against drying is required, compared to concrete massifs, this is due to the developed plane in combination with the available volume. The edges and corners begin to dry out faster than the rest of the plots.
Working with large surfaces
From the moment when the laying of concrete on an open large surface is completed, appropriate care is necessary, the implementation of which is possible in several ways.
For irrigation, a standard hose with a spray nozzle is used. In some cases, the installation of a continuous irrigation system is rational. But this can lead to the flowering of concrete due to the dissolved iron contained in the water. Therefore, it is desirable to use pipes from specialized alloys.
When constructing dams, it is worth remembering that a large open surface is present on each block, that is, the care for concrete in the summer should be carried out by shelter and irrigation with water.
Thin coating features
Due to the insignificant thickness, the concrete floor is characterized by a rapid loss of moisture. This contributes to the formation of a dusting and wear-resistant coating. It is necessary to organize the appropriate work, so that hardening of the concrete is not accompanied by a loss of moisture. The floor after the final ironing is sprinkled with water and covered with sand, or covered with waterproof material. Coverage is possible only if there is no probability of damage to the surface. The sand cover must always be moistened. There are also other methods of retaining moisture, but they are less effective.
Care of concrete with the help of protective preparations
A variety of protective devices have been developed which are used for spraying on a concrete mass and are divided into three types: painted black, white and colorless. The last two options have less impact on the shade of the material. White compounds are designed to cover the concrete surface from the sun, reduce heat caused by sunlight and reduce the amount of fumes. As practice shows, concrete with a white surface has properties similar to protecting the material from exposure to sunlight, which leads to a reduction in heating on its entire surface.
Resin solutions were used to apply to the surface of aerodromes, as care of concrete Until the sufficient strength necessary for other techniques is achieved. Due to the dark color and increased absorption of heat, the protective coating was much less effective.
Based on bitumen
Bituminous coatings increase the temperature and lead to active evaporation. Temperature stresses increase in the presence of empty areas, which contributes to the occurrence of cracks. In cloudy weather bituminous compounds can reduce cracking, but in dry wind they are powerless before the evaporation of moisture. Using a white additional coating will reduce heat absorption. But it is not capable of completely eliminating all the disadvantages of protective compounds of black color, as white coatings are destroyed under the influence of environmental conditions. In any case, so that later you do not have to guess why the concrete is cracking, it must be covered with burlap or film, and then moistened with the usual method.
For surfaces with subsequent falling asleep, as well as for pipes and tunnels, the use of tar or bitumen coatings is rational. To reduce the degree of heat absorption, whitewashing is carried out before the coating is covered.
Recently, the use of protective agents has been noted, which form an elastic, thin, strong film. They have not yet acquired extensive distribution due to their narrow focus, but with proper use they are useful in moderately dry, hot weather. Their effectiveness is reduced in regions with arid climate.
Care of concrete after pouring is also carried out with the help of salts that absorb moisture from the environment. It should be noted that if the relative humidity falls below the critical level, the reverse effect occurs, consisting in the evaporation of water.