The use of building materials allows you to create the desired element in a short period of time. The most high-quality and durable concrete is considered. From this material, you can build houses, flood floors, create technical structures. The main parameter that determines the quality of the material is the concrete surface modulus.
Description of the concept
The surface module is the ratio of the cooled or heated area using building material to its volume. This parameter is important both for construction and for the operation process, since it determines the conditions of use and the durability of the material.
Mn = S / V - formula:
- Mn is the surface modulus;
- S is the area of the structure;
- V is the volume of the monolith.
There are several ways to calculate its values, which are designed for real structures. Also, when drawing up the formula, the filling method and the presence of additional elements, the layer thickness, the conditions in which the base is dried, are taken into account. With incorrect calculations of the concrete surface, this can lead to the wrong choice of heating technology, the appearance of defects on the surface, cracks and breaks.
The builders are faced with the main task when laying the mixture in the winter - to provide concrete the opportunity to quickly harden under conditions in which it would gain all its characteristics. With frequent precipitation, low temperatures, climatic differences, concrete laying is not recommended.
Quality definition
If we talk about the ideal time for concrete work in the open air, then this is certainly a warm season. In such a period, as a rule, a positive temperature prevails, there is not a large amount of precipitation, a stable sun, due to the heating of which the texture of the material quickly hardens. Unfortunately, it is not always possible to work under such conditions, most often construction is carried out at low temperatures.
In the process of concreting under frost, the main problem arises, the essence of which is to increase the strength of concrete and begin to crystallize water in it. The main methods for solving it include the creation of thermal insulation of the formwork or special heating of the laid mixture.
The choice of solution depends on how quickly the mold with the embedded material will solidify. This can be determined using special formulas and the ratio of the area to the surface to be cooled and its volume. The surface modulus of concrete helps to solve a number of issues and determine how quickly, in contact with cold air, this area can harden.
When calculating the module in winter, it is necessary to take into account the factor that the process of gaining strength by concrete stops when the temperature is cooled to 0 degrees. Only those parts of the surface that come in contact with colder air are considered to be cooled.
Masters advise using additional heating elements that will help to quickly solve the problem of hardening of the laid monolith.
Calculation Parameters
If we talk about the practical side, then the calculation of beams, cylinders, additional transitions in diameter can be quite complicated. Therefore, wizards simplify this and use several formulas for the main structural elements.
When deducting, tricks such as beam length or column height are used; other indicators do not affect the surface modulus and are not taken into account in the calculations. In the calculations, the entire surface is taken into account. True, this calculation will be relevant only if it cools as quickly as possible.
That is, the concrete surface is on frozen ground or constantly in contact with cold air. Otherwise, its elements are not taken into account. Builders advise using a concrete surface module when designing a building.
This will help to calculate the necessary data and take measures by which the hardening process will be fast and high-quality.
Heating and cooling
Unfortunately, it is unrealistic to provide high-quality simultaneous heating or cooling of concrete along the entire perimeter of the monolith. Any change in the conditions in plus or minus can lead to the appearance of delta temperatures between the core and the surface.
If the delta is small, then there will be no concrete effect on the surface, the concrete will gradually harden, then its basic qualities will appear. But if the temperature is very sharp, then cracks or chips may form on the surface. As for the calculation in practice, it will be the larger, the more massive the design and vice versa. If the increase in temperature difference is sharp, then this will lead to an increase in internal stresses in the material.
In order to avoid this, builders advise laying with balls, pouring concrete gradually. The temperature in all its sections should be approximately the same. This index is also taken into account when drawing up the formula for the modulus of concrete surface.
With a surface modulus of up to 4 meters, the temperature change should not be more than 5 degrees per hour. If it lies in the range from 5 to 10 meters, then the rate of change should not exceed 10 degrees per hour. If the module is more than 10 meters, then the rate of change is not more than 15 degrees per hour.
As for ensuring temperature stability, this factor is possible when using thermal insulation of a concrete monolith. With high-quality heating, constant power adjustment of the cable for concrete or the use of a heat gun should be carried out. Without this, chips are formed in the event of overheating and rapid crystallization of water on the surface of concrete.
Temperature support
The fact that this is a module of the surface of concrete will be considered in more detail. Almost everywhere, information is given on the importance of maintaining a stable temperature. Various techniques may be used for this.
If the surface modulus is in the range of 6 to 10 meters, then it is advisable to warm the mixture here before laying it in the mold. With this option, the cooling period to a critical temperature is increased, hot concrete sets faster and gains the required strength. This is an effective option for quick work. The second way is to use additional elements that are introduced into the mixture immediately before the masonry and accelerate its hardening. For example, quick-hardening Portland cement of high grades. This can also be achieved by increasing the amount of concrete.
As for the alternative approach, it boils down to lowering the temperature by crystallization of water. It also adds special elements that increase strength even at low temperatures. With the right choice of hardening method, based on deductions of the surface modulus, you can get a high-quality result and a durable surface without flaws and cracks.
Routing
This is the main document in which there is information about concrete laying, its technical characteristics, a list of people participating in the masonry. It also indicates the temperature regime at which hardening will be maximum. The technological map is considered an important document for engineering and technical workers, construction and design organizations.
It can also be used by manufacturers, craftsmen and team leader in the process of laying materials. Mandatory is the attribution of the technological map.
It consists of several categories. The main ones are: the scope, organization and technology of the work, indicating the quality requirements, the need for material and technical resources, as well as a list of the necessary elements that will be used when laying the material.
A mandatory element of the technological map is the availability of solutions for safety, as well as technical and economic indicators. Although this document is drawn up for a specific area, examples of determining the surface modulus, using a routing sheet and determining the strength of concrete are also considered mandatory .
The routing is a document by which the level of practicality and quality of concrete will be determined. Its obligatory element is the calculation of the concrete surface modulus.
Formwork
After the poured concrete begins to gain the minimum necessary strength, the temperature on the surface and near the core stabilizes, the formwork is removed and the created insulation is removed. This should occur at low temperatures. If the temperature regime is not observed during the process, this leads to a surface split.
If the reinforcement coefficient exceeds 3%, the air may be several degrees colder than concrete. If the surface modulus is more than 5 meters, the maximum allowable temperature differences take the value of 30, 40 or 50 degrees. This must be taken into account. If we say that this is the surface modulus of a concrete structure, then its concept is close to the concrete modulus. But this includes the values of additional elements that are used in the masonry process.
The factor depends on the availability of additives in the base mixture.
Concrete processing in winter
If we talk about the processing of concrete after it has gained the necessary strength, then there is nothing special. But as for the device of the aperture in the monolith until it gains strength, a number of specific factors stand out here.
Experts advise not to use a jackhammer or a perforator on a surface that has not yet gained the required strength. In other words, it is better not to touch the concrete, which has not yet gained the required brand strength, since this is fraught with the appearance of cracks and imperfections on the surface.
The best option for the device of openings is the formation of formwork and additional elements for it at the stage that begins before pouring the monolith. In this case, the surface will not collapse under the influence of mechanical stress.
There are places where it is impossible to add formwork, corrugated fittings are used there. Corrugation on the surface itself serves as an anchor for further work. In the process of creating a technological map, the surface module of the floor slab is also taken into account.
Expert Advice
Builders and craftsmen advise to carry out technological preparation before laying concrete, clarify its brand, the presence of additives and calculate the surface modulus well. If the work will be carried out in the winter, it is imperative to take into account the temperature delta and the availability of additional means that will provide reliable thermal insulation and protection against mechanical damage.