Reinforcement of reinforced concrete structures: the minimum

Independent construction has long ceased to be something out of the ordinary: if you have the necessary knowledge, skills and helpers, this is quite feasible. Construction works rarely do without pouring concrete, which for the most part must contain a certain number of reinforcing elements. Reliability and durability of a concrete object can only guarantee the reinforcement of reinforced concrete structures according to GOST.

Of course, self-pouring reinforced concrete objects for the construction of a multi-storey building or another similar structure is not possible, since such scales require an industrial approach. In this case, we consider only cases that may arise in private practice, where you can easily do on their own.

This article will give the rules for reinforcement of reinforced concrete structures, which are used in private construction.

Concrete reinforcement

Reinforcement is necessary to increase the strength potential of concrete - reinforced concrete is many times greater than an ordinary analog in fracture strength. Improved reliability provides a metal frame, welded from reinforcement, which is located in the thickness of the concrete. It plays the role of a skeleton, which repeatedly increases the endurance of the object (find out here how the reinforcement of aerated concrete occurs).

In modern construction, the use of reinforced concrete is a de facto standard, despite the fact that its price is much higher than the usual equivalent. However, the presence of reinforcement does not convert concrete to reinforced concrete. Sometimes a frame welded at random is simply immersed in the formwork, which is then poured with mortar - some builders may mistakenly call it reinforced concrete, but this statement is erroneous.

Minimum gain percentage

To turn ordinary concrete into reinforced concrete, it is not enough just to lay a metal frame in it. There is such a concept as the minimum percentage of reinforcement of reinforced concrete structures, through which the degree of transition of one state to another is determined. If the percentage of occurrence of metal elements is less than the required, then this product refers to concrete names.

Note! This section is based on clause 5.16 of SNiP 2.03.01-84 “Concrete and reinforced concrete structures”

If the number of metal components is less than the required, then this type of reinforcement is considered to be structural reinforcement - while the product does not become reinforced concrete.

Minimum gain percentage объекта продольной арматурой рассчитывается исходя из площади сечения бетонного элемента.

• In eccentrically stretched and bendable objects, if the longitudinal force is located outside the working height of the cross section, the reinforcement must be at least 0.05% (reinforcement S) of the cross sectional area of ​​the concrete element;
• In eccentrically stretched objects, where the longitudinal force is located between reinforcement S and S ”, the reinforcement must be at least 0.06% (reinforcement S and S”) of the cross-sectional area of ​​the concrete element;
• In eccentrically compressed objects, the minimum percentage of occurrence of metal elements is from 0.1 to 0.25% (fittings S and S ”).

Note! If the longitudinal reinforcement is located along the contour of the section (uniformly), then the cross-sectional area of ​​the reinforcement should be twice as large as the specified values. This also applies to centrally stretched objects.

Maximum gain percentage

In concrete work, the instruction “the more the better” is inappropriate.

An excessive amount of metal components will significantly impair the technical characteristics of the product.

As in the previous case, there are also standards.

• Regardless of the class of concrete and reinforcing elements, the largest percentage of reinforcement in the cross section of the product should not exceed 5% in the case of columns and 4% in all other cases. At the same time, the concrete mortar must efficiently penetrate between the parts of the reinforcement cage;

Note! In both cases, hot-rolled steel is meant as reinforcing elements for the reinforcement of reinforced concrete structures.

Concrete cover

Усилительный каркас должен покрываться защитным слоем бетона, который обеспечивает совместную работу бетона и металлического скелета. Также он защищает металл от коррозии и воздействия окружающей среды (см.также статью «Защита бетона от влаги: способы и применяемые материалы»).

The thickness of the layer above the metal frame components should be.

In walls and plates (mm thickness) not less:

• Over 100 mm - 15 mm;
• Up to 100 mm and inclusive - 10 mm;

In ribs and beams:

• Over 250 mm - 20 mm;
• Up to 250 and inclusive - 15 mm;

In the foundation beams:

• Not less than 30 mm;

In the columns:

• Not less than 20 mm;

Note! If the protective layer is more important, then for additional reinforcement, wire is used for the reinforcement of reinforced concrete structures, which will block the surplus.

In the foundations:

• Monolithic with cement pad - 35 mm;
• Prefab - 30 mm
• Monolithic without cement pad - 70 mm;

Note! This section was compiled in accordance with clause 5.5 of SNiP 2.03.01-84 “Concrete and reinforced concrete structures”

It should also be noted that diamond drilling of holes in concrete or cutting of reinforced concrete with diamond circles should take into account the location and structure of the reinforcement cage. Separating parts or through holes can significantly reduce the strength potential of an object. If we are talking about the complete dismantling of the object, then this circumstance is not necessary to take into account.

Total

Compliance with the norms and standards will be a reliable guarantee of durability and reliability of reinforced concrete structures. You can get more detailed information on this topic by watching the video in this article (find out also how the concrete is heated by the welding machine).