Concrete hardening is accompanied by chemical reactions, which are significantly affected by the presence of water. When diluting concrete, a sufficient amount of liquid is added to the mass to ensure hydration. In order for this process to continue until the concrete has completely hardened, it is necessary to replenish water supplies or take measures to preserve them. Concrete care after pouring is based on maintaining a wet state for a set time to prevent moisture absorption by the soil surface or formwork and its evaporation. Systematic wetting of the plane is also possible.
rules
Heavy concrete GOST 26633 2012, which contains slow-hardening cement, is aged in the moistened state for at least two weeks. A shorter time is required for cement with fast hardening, but in this case, work is carried out more carefully.
Wet concrete has a lower temperature than normal. This factor is relevant for alumina material, since there is a decrease in its strength by almost a factor of two when the temperature threshold is exceeded 32 ° C.
Concrete maintenance on SNiP 3.01.01-85 is regulated. All methods of regulation of humidity and temperature are set by the project of the facility.
Features of summer care
The main objective of surface care in the summer is to prevent drying out. The formation of a suitable humidity regime has simple rules that require systematic execution. Solar direct rays and wind adversely affect exposed surfaces, so they must be protected from them. Moisture-resistant coatings are used for this, for example, tarpaulin or burlap. A polyethylene film can also act as a material to prevent drying out. It helps prevent the appearance of questions such as: "Why does concrete crack and salt deposits appear?"
In the absence of special coatings, the surface is watered several hours after completion of work or filled with sand. The frequency of watering is influenced by environmental conditions, but, regardless of them, the coating must be constantly moist until the concrete acquires most of the set strength. Use of a sleeve with a sprayer for watering is possible.
Under the condition of high temperatures, formwork is also watered before concreting works. If it is removed before the concrete maintenance is completed, moistening of the dismantled vertical planes will be required. For regions with a hot, dry climate, it is rational to use a system with small openings 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 effects, an insulation layer or wastewater is arranged. Such work is carried out for alumina cement for three days, and for 10-14 days for other types.
Significant salt content in water can complicate watering the structure. After evaporation of the liquid, salts remain on the material and lead to a decrease in the strength of concrete. In this case, only the coating is exposed to watering, which is placed at a distance of several centimeters from the structure. Vapors moisturize the mixture, while the salts remain on the covering material.
To protect and moisten the concrete mixture, a significant investment of time and effort is required. Therefore, bituminous and painting compositions, polymer protective films for surfaces with a large footage are often used, provided that there is no further contact with concrete.
A special moisture regime is necessary for elements of light cement with porous aggregates. Concrete care in the summer is carried out with the help of coatings made of film and paintwork, protecting from moisture.
Low temperature work
Naturally, if you can choose the time for concrete work, it is better to give preference to the summer months. But if concreting has to be carried out in winter, special steps are necessary to protect the material from freezing before it regains proper strength.
When preparing the solution without adding special modifiers, you need to heat the water. In this case, continuous laying should be carried out. Frozen upper layers should be treated with steam and removed, after which pouring work continues immediately.
Concrete winter care includes the following:
- Under the condition of the boundary temperature range, the structure is insulated using insulating materials.
- Transformers with high power are used to heat the hardening base.
- A light type of material is used or heavy concrete, GOST which provides for the presence of antifrosty additives.
Creating a thermal normal mode is possible with the help of a “tent” with simultaneous heating with 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 an infrared heater.
Formwork
Modern designs provide sufficient protection against drying out, the remaining open planes should be covered immediately after pouring in dry weather.
So that the timber formwork does not absorb moisture and provides high-quality hardening of concrete, its inner surface is pre-coated with a special oil composition. Systematic spraying from the outside, especially in hot weather, will not be superfluous.
For small structures, increased drying protection is required, compared with concrete masses, this is due to the developed plane in combination with the available volume. Faster than the rest, the edges and corners begin to dry out.
Work with large surfaces
From the moment the concrete is laid on an open large surface, appropriate care is necessary, the implementation of which is possible in several ways.
For irrigation, a standard hose connected to the pipeline with a spray nozzle is used. In some cases, the installation of an irrigation system with continuous operation is rational. But this can lead to concrete blooming due to the dissolved iron contained in the water. Therefore, it is desirable to use pipes from specialized alloys.
When arranging dams, it is worth remembering that there is a large open surface on each block, that is, concrete care 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 dusty and wear-resistant coating. The organization of appropriate work is required so that the hardening of concrete is not accompanied by a loss of moisture. After finishing ironing, the floor is sprayed with water and covered with sand, or covered with waterproof material. Arrangement of the coating is possible only when there is no likelihood of surface damage. Sand shelter should always be wet. There are also other methods of moisture retention, but they are less effective.
Concrete Care with Protective Products
Many protective agents have been developed that are used for spraying on concrete and are divided into three types: painted in 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 exposure to 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 decrease in heating on its entire surface.
Resin solutions were used to apply to the surface of airfields, as concrete care until then, until sufficient strength is achieved, which is necessary for other methods. Due to the dark color and increased heat absorption, the protective coating had much less efficiency.
Bitumen Based Compounds
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 compositions can reduce cracking, but in a dry wind they are powerless before evaporation of moisture. The use of a white additional coating will reduce heat absorption. But it is not able to completely eliminate all the shortcomings of the protective compositions in black, since white coatings are destroyed under the influence of environmental conditions. In any case, so that later you do not have to wonder why concrete is cracking, it must be covered with burlap or film, and then moistened with the usual method.
For planes with subsequent falling asleep, as well as for pipes and tunnels, it is rational to use coatings from tar or bitumen. To reduce the degree of heat absorption, concrete is whitewashed before the coating is covered.
Recently, the use of protective agents that form an elastic thin durable film has been noted. They have not yet gained wide distribution due to their narrow focus, but when used correctly, they are useful in moderately dry, hot weather. Their performance is reduced in regions with arid climates.
Hygroscopic salts
Concrete care after pouring is also carried out using salts that absorb moisture from the environment. It should be noted that if the relative humidity drops below a critical level, the opposite effect occurs , which consists in the evaporation of water.