Hardening time of concrete: polymerization theory.

To effectively plan all construction work, you need to know how long the concrete hardens. And here there are a number of subtleties that largely determine the quality of the erected structure. Below we describe in detail how the solution is drying, and what you need to pay attention to when organizing related operations.

Theory of Cement Polymerization

To lead the process, it is very important to understand exactly how it happens. That is why it is worthwhile to study in advance what constitutes cement hardening (learn here how to make vases from concrete).

In fact, this process is multistage. It includes both strength and drying.

Let's look at these stages in more detail:

• The hardening of concrete and other cement-based solutions begins with the so-called setting. In this case, the substance in the formwork enters the primary reaction with water, due to which it begins to acquire a certain structure and mechanical strength.
• Setting time depends on many factors.. If we take the standard air temperature in 20⁰C, then for the M200 solution, the process starts approximately two hours after pouring and lasts about an hour and a half.
• After setting, the concrete hardens.. Here, the bulk of the cement granules react with water (for this reason, the process is sometimes called cement hydration). The optimal conditions for hydration is about 75% humidity and 15 to 20 temperature.⁰WITH.
• At temperatures below 10⁰C there is a risk that the material will not gain design strength, which is why special anti-frost additives should be used for working in the winter period..

• The strength of the finished structure and the rate of solidification of the solution are interrelated. If the composition loses water too quickly, not all of the cement will have time to react, and low density densities will form inside the structure, which can become a source of cracks and other defects.

Note! Cutting reinforced concrete with diamond circles after polymerization often clearly demonstrates the heterogeneous structure of the plates, filled and dried in violation of technology.

• Ideally, the solution takes 28 days to cure.. However, if the design does not put forward too stringent requirements for bearing capacity, then you can begin to exploit it within three to four days after pouring.

Practical recommendations

Factors affecting the freezing

Планируя строительные или ремонтные работы, важно верно оценить все факторы, которые будут влиять на скорость обезвоживания раствора (читайте также статью «Неавтоклавный газобетон и его особенности»).

Experts highlight the following points:

• First, environmental conditions play a crucial role. Depending on the temperature and humidity, the foundation poured in can either dry out in just a few days (and then not gain design strength), or remain wet for more than a month.
• Secondly - the density of styling. The denser the material, the slower it loses moisture, which means that cement is more effectively hydrated. Vibro-processing is most often used for compaction, but when doing work with your own hands, you can get by with a bayonet.

Tip! The denser the material, the harder it is to handle after hardening. That is why for structures, the erection of which was applied vibroplate, often requires diamond drilling holes in concrete: ordinary drills wear out too quickly.

• The composition of the material also affects the speed of the process. Mainly, the rate of dehydration depends on the porosity of the filler: clay and slag accumulate microscopic particles of moisture, and give them much slower than sand or gravel.
• Also, moisture retention additives (bentonite, soap solutions, etc.) are widely used to slow down drying and more effective curing. Of course, the cost of construction increases, but you do not need to worry about premature drying.

• In addition to all of the above, the instruction recommends paying attention to the formwork material. The porous walls of unedged boards draw a significant amount of liquid from the edge areas. Therefore, to ensure strength, it is better to use a formwork made of metal shields or to lay plastic wrap inside the plank box.

Process Tips

Self-pouring concrete foundations and floors should be carried out according to a specific algorithm.

To retain moisture in the thickness of the material and promote maximum strength, you need to act as follows:

• To begin with, we perform high-quality waterproofing formwork. To do this, we cover wooden walls with polyethylene or use special plastic collapsible shields.
• The composition of the solution we introduce modifiers, the action of which is aimed at reducing the rate of evaporation of the liquid. You can also use additives that allow the material to gain strength faster, but they are quite expensive, and therefore apply them mainly in high-rise construction.
• Then pour concrete, compacting it carefully. For this purpose it is best to use a special vibrotool. If there is no such device, we treat the mass to be filled with a shovel or a metal rod, removing air bubbles.

• The surface of the solution after setting, cover with plastic wrap. This is done in order to reduce moisture loss in the first few days after installation.

Note! In the fall, polyethylene also protects cement in the open air from precipitation washing away the surface layer.

• In about 7-10 days, the formwork can be dismantled. After dismantling, we carefully examine the walls of the structure: if they are wet, then you can leave them open, but dry ones should also be covered with polyethylene.
• After that, once every two or three days we remove the film and inspect the surface of the concrete. If a large amount of dust, cracks or peeling of the material appears, we moisten the frozen solution with a hose and cover it again with polyethylene.
• On the twentieth day, remove the film and continue drying in the natural mode.
• After 28 days have passed since uploading, the next stage of work can begin. At the same time, if we did everything correctly, the construction can be loaded “to the fullest” - its strength will be maximum!

Conclusion

Knowing how long the concrete foundation hardens, we can properly organize all other construction work. However, it is impossible to accelerate this process, since cement acquires the necessary performance characteristics only when it hardens for a sufficient time (also learn how to build a concrete cellar).

More detailed information on this issue is described in the video in this article.