When to shoot a formwork after pouring concrete?

The foundation and formwork are one of the most important stages of the construction of the house, as they act as the basis and framework for the formation of the future structure. The design of the formwork should remain assembled until the complete pouring of concrete. Therefore, it is very important to have information, after what period of time it can be safely disassembled.

Influencing factors

To form a foundation, a concrete is used, which is a semi-liquid composition. But it is necessary that the substance retains the required form. For this purpose, a wooden formwork is used. It is a temporary removable design, the internal volume of which is in accordance with all the necessary parameters and configuration. The formwork is formed immediately at the construction site, it is fixed using a wooden or reinforcement frame, then the concrete fill is directly carried out.

Depending on the type of foundation, the wooden formwork is formed in different ways. Its removal from the ribbon foundation or from a bar may differ somewhat in terms of timing. To achieve a uniform distribution of load on the building, Armopoyas. From Armopoyas to dismantle the formwork requires exclusively after installing the reinforcement and solo the concrete solution.

Concrete is formed in several stages.

  • Concrete decay.
  • The process of durability.

In concreting, important factors affecting the strength of the composition of concrete are such.

  • Water availability (constant saturation of concrete water avoids the appearance of cracks on the formed surface, with a lack of moisture, the composition becomes fragile and loose).
  • Temperature mode (any reactions proceed the faster than the higher the temperature).

During the work, it is possible to influence only the humidity of concrete. It is impossible to affect the temperature regime. Therefore, the time of frozen in different regions and in different climatic conditions will be different.

Formwork can be with a film or without a film.

Film used to protect the boards from high humidity. The feasibility of its use is disputes, the decision must be taken in each particular case individually.

Standards

In accordance with S Snip 3.03-87 Removing the formwork must be performed only if concrete achieved the necessary degree of strength and depending on the configuration of a specific design.

  • Vertical design – Making a removal in the case of an indicator of 0.2 MPa.
  • Foundation Ribbon or Monolith Reinforced – can be disassembling the wooden formwork in the case when the indicator will be 3.5 MPa or 50% of the concrete brand.
  • Inclined constructions (stairs), Various overlaps, the length of which is more than 6 meters – The period of platform occurs when 80% of concrete strength is reached.
  • Designs oblique (stairs), overlap less than 6 meters long – The parsing period occurs when 70% of the strength of the brand of the concrete used is reached.

Snip 3.03-87 is currently officially considered not extended. However, the requirements specified in it are absolutely relevant and at the moment. Perennial Construction Practice This confirms. According to the American Standard ACI318-08 Formwork from wood Must be deleted after 7 days, by comparable air temperature and humidity, all accepted standards.

In Europe, there is own standards of ENV13670-1: 20,000. According to this standard, dismantling of the wooden formwork can be carried out in the case when 50% of the strength of the concrete composition takes place if the average daily temperature was at least zero degrees.

With strict observance of the deadlines specified in the requirements of SNiP, the strength of the monolithic structure can be achieved. The accumulation of strength is carried out and subsequently, but the minimum required strength must be achieved until the dismantling of the wooden formwork is performed.

In the implementation of private construction, there is no possibility to establish the exact percentage ratio of the strength of the concrete material, most often due to the absence of the necessary devices. Therefore, it is required to make a decision on the disassembly of the formwork, pushing off from the time of concrete exposure.

Experienced, it was proved that Concrete of frequently used M200-M300 brands at the average daily air temperature 0 degrees in 14 days can dial a strength of approximately 50%. If the temperature is about 30%, then the same brands of concrete get 50% much faster, namely in three days.

Removing the wooden formwork is carried out the next day or after a day after the completion of the grapping period of concrete. However, experts recommend not to rush with disassembly of a wooden formwork, because every few hours the solution is only stronger and more reliable.

In any option, it should be sure to make sure that the concrete has reached the required level of strength of the composition.

After how many days to remove with the temperature of the air?

To make a decision when you can clean the wooden formwork, you need to consider one main factor, namely, the ambient temperature. According to this at different times of the year, the grasp period will be different. As a result, mostly all construction work related to the fill of the foundation are carried out in the summer.

When calculating the temperature, not the maximum or minimum value throughout the day, but the average daily value. Depending on the specific weather conditions, the time is calculated to remove the created formwork from concrete overlap. It should not be too rushing with the platform uniquely, since certain unaccounted factors can somewhat slow down the process of crystallization of the concrete solution.

In practice, during the work on the organization of the foundation, a wooden formwork preferes not to remove at least two weeks. Most intensively concrete acquires strength in the first week. Subsequently, the base is hardening for two years.

If it is possible, it is recommended to wait 28 days. This time is required in order for the foundation to have approximately 70% of strength.

Is it possible to speed up?

In order for construction work to go more quickly, it may be necessary to speed up the process of hardening concrete solution. For this purpose, three main ways apply.

  • Heated mixture of concrete.
  • Using special types of cement.
  • The use of specialized additives that accelerate the hardening process of concrete solution.

In factory conditions, high temperature is used to accelerate the hardening of concrete composition. The process of steaming various reinforced concrete structures significantly reduces grasp. But this method is not usually applied in private construction. Increased temperature for every 10 degrees increases the setting speed of 2-4 times.

A fairly effective method of accelerating the grasp process is the use of cement of fine grinding.

Despite the fact that the cement of large grinding has a large shelf life, it is a mixture of fine grinding a much faster.

The use of special additives is another way to make the process of hardening the composition of concrete faster. Calcium chloride, sodium sulfate, iron, potash, soda and others can be used as additives. These additives are mixed in the process of preparing the solution. Such accelerators increase the solubility of cement components, the water is saturated faster, as a result of which the crystallization is more actively. In accordance with the requirements of GOST, the accelerators increase the speed of hardening in the first day at least by 30%.

What will happen if you disassemble the formwork too early?

In the warm season, the platform can be done quite quickly, you can not wait 28 days. Concrete after the completion of the first week already has the ability to maintain the necessary form.

But immediately carry out construction on such a foundation can not. It is necessary to wait for the time when the monolith will reach the desired level of strength.

If the formwork dismantling is too early, it can lead to the destruction of the created concrete structure. The foundation is the basis of the structure, and not just one of their technological details. On this monolith, all the structure will be held, so it is very important to comply with all the necessary standard requirements and standards.

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