Concrete hardening is accompanied by chemical reactions, which are significantly affected by the presence of water. A sufficient amount of liquid is added to the mass when diluting concrete 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 conserve them. Care of concrete after pouring is based on maintaining a wet state for a specified 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 a moistened state for at least two weeks. A shorter time is required for fast curing cement, but in this case, work is carried out more carefully.
Wet concrete is cooler than regular concrete. This factor is relevant for aluminous material, as there is a decrease in itsstrength is almost doubled when the temperature threshold is exceeded at 32 ° С.
Regulated concrete care SNiP 3.01.01-85. All methods for regulating humidity and temperature regimes are established by the project of the facility.
Features of summer care
The main task of surface care in summer is to prevent drying out. The formation of a suitable humidity regime has simple rules that require systematic implementation. The direct rays of the sun and the wind have a detrimental effect on open surfaces, so they must be protected from them. Moisture-absorbing coatings are used for this, for example, tarpaulin or burlap. Polyethylene film can also act as a material to prevent drying out. It helps prevent questions such as: "Why does concrete crack and s alt deposits appear?"
In the absence of special coatings, the surface is watered or covered with sand a few hours after completion of work. The frequency of watering is influenced by environmental conditions, but regardless of them, the coating must be constantly wet until the concrete has reached most of the specified strength. It is possible to use a sleeve with a spray for watering.
Under the condition of high temperatures, the formwork is also watered before the start of the concreting work. If it is removed before the curing of the concrete is complete, dampening of the stripped vertical surfaces will be required. For regions with a hot dry climate, it is rationalusing a system with small holes to water vertical surfaces with a sharp slope.
Other negative factors
The quality of laid concrete can be affected not only by heat, but also by groundwater. To avoid aggressive impact, a layer of insulation or drainage is equipped. Such work is carried out for aluminous cement for three days, and for 10-14 days for other types.
Significant s alt content in the water can make it difficult to water the structure. After evaporation of the liquid, the s alts remain on the material and lead to a decrease in the strength of the concrete. In this case, only the coating is irrigated, which is placed at a distance of several centimeters from the structure. The vapors moisten the mixture while leaving the s alts on the covering material.
To protect and moisten the concrete mixture requires a significant investment of time and effort. Therefore, bituminous and painting compounds, polymer protective films are often used for surfaces with a large footage, provided there is no further contact with concrete.
Special moisture regime required for light cement elements with porous type aggregates. Concrete care in the summer is carried out with the help of film coatings and paints and varnishes that protect against moisture.
Work at low temperatures
Of course, if there is a choice of time for concrete work, it is better to give preference to the summer months. But ifconcreting has to be carried out in winter, special measures are necessary to protect the material from freezing before it gains proper strength.
When preparing a solution without adding special modifiers, you need to heat the water. In this case, continuous laying should be carried out. Frozen top layers should be steamed and removed, after which pouring work can continue immediately.
Winter concrete care includes the following:
- Subject to the boundary temperature range, the building is insulated using insulating materials.
- High power transformers are used to heat the hardening base.
- A light type of material is used or heavy concrete, the GOST of which provides for the presence of antifreeze additives.
Creation of thermal normal mode is possible with the help of a “tent” with simultaneous heating with a heat gun. It is worth noting that electrical heating is undesirable for thin-walled elements, as this can lead to overdrying. The way out is to use steam heating or an infrared heater.
Formwork
Modern designs provide sufficient protection against drying out, remaining exposed surfaces should be covered immediately after pouring in dry weather.
So that the formwork made of wood does not absorb moisture and ensures high-quality hardening of concrete, its inner surface is pre-coated with a special oil composition. Will notunnecessary systematic spraying outside, especially in hot weather.
Small structures require increased protection against drying out compared to concrete masses, this is due to the developed plane in combination with the available volume. Edges and corners begin to dry out faster than other areas.
Working with large surfaces
From the moment the concrete is laid on a large open surface, appropriate care is required, which can be done in several ways.
For watering, a standard hose connected to the pipeline with a spray nozzle is used. In some cases, it is rational to install a continuous irrigation system. But this can cause the concrete to bloom due to the dissolved iron in the water. Therefore, the use of pipes made of specialized alloys is desirable.
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.
Features of thin coating
Because of the slight thickness of 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 loss of moisture. After the final ironing, the floor is sprayed with water and covered with sand, or covered with waterproof material. The arrangement of the coating is possible only if there is no possibility of damage to the surface. The sand shelter should always be moistened. There are also other methods of retaining moisture, but they are less effective.
Concrete care with protective preparations
Many protective agents have been developed, which are used for spraying on the concrete mass and are divided into three types: painted black, white and colorless. The last two options have less effect on the shade of the material. White compounds are designed to cover the concrete surface from the sun, reduce the heat caused by sunlight and reduce the amount of evaporation. In practice, concrete with a white surface has properties similar to protecting the material from exposure to sunlight, which leads to a decrease in heating over its entire surface.
Resin solutions have been used for application to the surface of airfields, as a curing of concrete until sufficient strength is achieved, required by other methods. Due to the dark color and increased heat absorption, the protective coating was much less effective.
Compounds based on bitumen
Bitumen coatings increase the temperature and lead to active evaporation. Thermal 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 winds they are powerless against moisture evaporation. The use of white additional coating will reduce heat absorption. But it is not capablecompletely eliminate all the shortcomings of black protective compounds, since white coatings are destroyed under the influence of environmental conditions. In any case, so that later you don’t have to guess why the concrete is cracking, it must be covered with burlap or film, and then moistened in the usual way.
For planes with subsequent backfilling, as well as for pipes and tunnels, it is rational to use tar or bitumen coatings. To reduce the degree of heat absorption, the 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 become widespread due to their narrow focus, but when used correctly they are useful in moderately dry, hot weather. Their effectiveness is reduced in regions with arid climates.
Hygroscopic s alts
Concrete care after pouring is also carried out with the help of s alts that absorb moisture from the environment. It is worth noting that if the relative humidity drops below a critical level, the opposite effect occurs, consisting in the evaporation of water.
