The use of building materials allows you to create the desired element in a short period of time. Concrete is considered the highest quality and most durable. From this material, you can build houses, pour 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 modulus is the ratio of the cooled or heated area using a building material to its volume. This parameter is important both for construction and for the operation process, as it determines the conditions of use and the durability of the material.
Mp=S/V – formula:
- Mp – surface modulus;
- S – construction area;
- V is the volume of the monolith.
There are several ways to calculate its values, which are designed for real designs. Also when compilingThe formula takes into account the method of pouring and the presence of additional elements, the thickness of the layer, the conditions under which the base is dried. 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.
Before the builders, when laying the mixture in the winter, the main task is to provide the concrete with the opportunity to quickly harden in conditions under which it would gain all its characteristics. With frequent precipitation, low temperatures, climatic changes, it is not recommended to lay concrete.
Definition of quality
If we talk about the ideal time for concrete work outdoors, then this is definitely the warm season. During such a period, as a rule, a positive temperature prevails, there is no 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 appears, the essence of which is the strength gain of concrete and the beginning of water crystallization in it. The main methods of its solution 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 form with the embedded material will harden. This can be determined using special formulas and the ratio of the area to the cooledsurface and volume. The surface modulus of concrete helps to solve a number of issues and determine how quickly, in contact with cold air, a given area can harden.
When calculating the modulus in winter, one must take into account the fact that the process of curing concrete stops when the temperature cools to 0 degrees. Only those parts of the surface that are in contact with colder air are considered cooled.
Masters advise using additional heating elements that will help to quickly solve the problem with the 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, the wizards simplify this and use several formulas for the main structural elements.
When deducting, tricks such as the length of a beam or the height of a column are used, other indicators do not affect the surface modulus and are not taken into account in the calculations. The calculation takes into account the entire surface. True, this calculation will be relevant only if it cools as quickly as possible.
That is, the concrete surface stands on frozen ground or is constantly in contact with cold air. Otherwise, its elements are not taken into account. Builders advise using the concrete surface modulus when designing a building.
This will help you calculate the right data and take steps to ensure that the hardening process is fast and of good quality.
Heating and cooling
Unfortunately, it is unrealistic to provide high-quality simultaneous heating or cooling of concrete around the entire perimeter of the monolith. Any change in conditions, plus or minus, can lead to a temperature delta between the core and the surface.
If the delta is small, then there will be no specific effect on the surface, the concrete will gradually harden, then its main 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 structure 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 to do the laying with balls, pouring concrete gradually. The temperature in all its parts should be approximately the same. This pointer is also taken into account when formulating the modulus of the 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 of 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 the thermal insulation of a concrete monolith. With high-quality heating, a constant adjustment of the power of the cable for concrete or use should be carried out.heat gun. Without this, chips are formed in case of overheating and rapid crystallization of water on the surface of the concrete.
Temperature maintenance
Let's take a closer look at the concrete surface modulus. Almost everywhere information about the importance of maintaining a stable temperature is indicated. Various techniques can be used for this.
If the surface modulus is in the range of 6 to 10 meters, then it is advisable to heat the mixture here before laying it in the form. With this option, the cooling period to the critical temperature increases, hot concrete sets faster and gains the desired strength. This is an efficient option for fast work. The second way is to use additional elements that are introduced into the mixture immediately before laying and accelerate its hardening. For example, fast-hardening Portland cement of high grades. You can also achieve this by increasing the amount of concrete.
As for an alternative approach, it comes down to lowering the temperature with the help of water crystallization. Special elements are also added here that increase strength even at low temperatures. With the right choice of hardening method, based on the deductions of the surface modulus, you can get a high-quality result and a durable surface without flaws and cracks.
Technological map
This is the main document that contains information about the laying of concrete, its technical characteristics, listing the people involved in the laying. Still in itthe temperature regime at which hardening will be maximum is indicated. The technological map is considered an important document for engineering and technical workers, construction and design organizations.
It can also be used by foremen, foremen and foreman in the process of laying materials. It is obligatory to indicate the authorship of the technological map.
It consists of several categories. The main ones include: the scope, organization and technology of work performance, 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.
An obligatory element of the technological map is the presence of a safety solution, as well as technical and economic indicators. Although this document is written for a specific area, examples of determining the surface modulus, using the technological map and determining the strength of concrete are also considered mandatory here.
Technological map is a document that will determine the level of practicality and quality of concrete. Its mandatory element is the calculation of the modulus of the concrete surface.
Presence of stripping
After the poured concrete begins to gain the minimum required strength, the temperature on the surface and near the core stabilizes, the formwork is removed and the created thermal insulation is removed. This should take place at sub-zero temperatures. If the temperature inprocess is not followed, it leads to splitting of the surface.
If the reinforcement ratio exceeds 3%, the air can be several degrees colder than the concrete. If the surface module is more than 5 meters, the maximum allowable temperature differences are 30, 40 or 50 degrees. This must be taken into account. If we talk about the fact that this is the modulus of the surface of a concrete structure, then its concept is close to the modulus of concrete. But this includes the values of additional elements that are used in the masonry process.
The factor depends on the presence of additives in the main mixture.
Working concrete in winter
If we talk about the processing of concrete after it has gained the desired strength, then there is nothing special. But as for the device of the opening in the monolith before it hardens, a number of specific factors stand out here.
Experts advise not to use a jackhammer or perforator on a surface that has not yet gained the desired strength. In other words, concrete that has not yet gained the required brand strength should not be touched, as this is fraught with the appearance of cracks and imperfections on the surface.
The best option for 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 load.
There are places where it is impossible to add formwork, corrugated reinforcement is used there. Corrugation on the surface itselfserves as an anchor for further work. In the process of creating a technological map, the surface modulus of the floor slab is also taken into account.
Expert Tips
Builders and craftsmen advise to carry out technological preparation before laying concrete, specify its brand, the presence of additives and calculate the surface modulus well. If the work will be carried out in winter, be sure to take into account the temperature delta and the availability of additional funds that will provide reliable thermal insulation and protection against mechanical damage.
