Application of a protective layer of concrete for foundation reinforcement: minimum and maximum thickness values

How to ensure the desired thickness when pouring

If you study the recommendations, it becomes clear that the thickness of the concrete layer is included in the preliminary design calculations and drawings.
All that remains is to comply with all the requirements practically. Naturally, the bottom row of rods in the foundation trench must be raised above the ground to a certain height. Complete ignorance is demonstrated by workers who use scraps of lumber instead of supporting elements. Wood is not durable and allows moisture to pass through it. Corrosion occurs in places where such supports are installed.

It is allowed to use brick or concrete stone as supports, but this option is not an ideal solution, since it does not provide reliable tightness.

The optimal solution is special racks made of polymer materials. They are made in different sizes, you can always choose the appropriate option that matches a particular design. Their cost compared to the cost of building materials is quite acceptable. In addition, such elements have hollow structures, which, when poured, are also filled with concrete mortar.

Thickness formation factors

Values ​​that determine the main parameter of the protective concrete layer:

• The magnitude of the load on the foundation is directly proportional to the thickness of the protective layer.
• The greater the thickness of the reinforcing bar section, the larger the layer of concrete required to protect the metal.
• The size of the protective layer is directly dependent on the climatic conditions of the construction site, the proximity of groundwater, the type of soil, and temperature changes.

The thickness parameters of the concrete protective layer must be indicated in the foundation design. The optimal layer of monolithic concrete between the surface of the reinforcement and the base wall is selected in accordance with the requirements of regulatory documents.

The practical implementation of design solutions, as a rule, does not require special knowledge or additional costs—conscientious adherence to standard recommendations is sufficient.

Permissible protection value for industrial structures

Basically, industrial-type structures are characterized by significant weight, so they must be durable. Let's consider the permissible values ​​of the protective layer for industrial structures.

1. When creating flat or ribbed slabs, wall panels, and partitions, make the thickness 20 millimeters.
2. If you plan to build columns or beams, then the wall is made 25 millimeters.
3. To make a foundation or beams for it, the wall thickness is about 30 millimeters.
4. Underground structures must have a protection of 20 millimeters.

To protect the end parts of the reinforcement, the recommended fill layer thickness is 10 millimeters, for structures with a length of up to 9 meters, up to 12 meters - 15 millimeters, from 12 meters - 20 millimeters. To make a frame or clamps with transverse rods, it is necessary to take into account the height of the product; if it is less than 250 millimeters, then the layer is 10 millimeters, and if it is more than this figure, then 15 millimeters. Such standards apply when creating structures in normal climatic conditions. If the weather conditions are too aggressive, that is, there is a sharp change in temperature, harsh winters or high humidity, then the standards should be different:

• concrete foundation - from 40 millimeters;
• if the base is in constant contact with the surface of the earth - from 75 millimeters;
• in contact with the ground and adverse weather conditions, for grades d18-40 - 52 millimeters, and d10-18 - from 25 millimeters;
• use of elements in the open air - from 30 millimeters;
• indoors, which has high humidity - from 25 millimeters.

To check the thickness of the protective layer, a magnet is used; various measuring instruments are made based on it.

Why do we need protection?

The fittings are made of steel. But even the strongest metal begins to rust under the influence of chemical compounds. Sources of corrosion provoke the formation of voids located inside the structure. With severe destruction, the strength characteristics of the concrete structure decrease, cracks and curvatures appear. In a neglected state, a monolithic product falls apart.

Steel rods for the reinforcement frame are additionally treated with an anti-corrosion coating. Galvanizing slows down oxidative processes, but does not leave the metal destroyed. Thin film can be damaged during careless transportation or careless installation.

Frame in solution Source prom.ua

To neutralize corrosion, a protective layer is needed for the reinforcement. The deficiency of the binding component in the structure reduces the parameters of strength and durability. Protecting steel from exposure to aggressive external environments is the main task of cement. Suitable concrete layer:

• fixes frame rods inside the structure;
• isolates capricious material from aggressive environments (water, temperature, air);
• distributes the load evenly.

If the thickness of the protective layer is insufficient, the cement and steel inside the structure will begin to collapse. Overuse of concrete increases the construction budget. High-quality reinforcement should create a reliable, strong barrier from oxygen and chemicals from the cement mortar. Correctly calculated parameters will ensure long-term operation.

Restoring the protective layer of concrete

The protective layer of concrete is a layer of concrete mixture, the thickness of which is equal to the distance from the surface to the beginning of the reinforcing parts. The main purpose of the protective concrete layer is to protect the reinforcement from the adverse effects of the external environment - high humidity, heating, corrosion, etc. In addition, the protective layer is necessary to secure the reinforcement in the concrete and ensure the joint work of iron and concrete.

During the operation of buildings or structures, building structures are exposed to severe atmospheric influences, the main of which are periodic wetting of the concrete surface and temperature fluctuations, which lead to the gradual destruction of the protective concrete layer. Various kinds of cracks and peelings appear in it, the reinforcement is exposed and its subsequent corrosion occurs. All this indicates the need to restore the protective concrete layer.

In the modern construction industry, there are a number of methods used to restore and strengthen the protective concrete layer. Let's take a closer look at them.

1. Plastering the building structure with a dense cement-sand mortar followed by application of a crack-resistant paint and varnish coating;

2. Coating the surface with cement or polymer concrete having a strength not lower than the structure being restored.

3. Application of special polymer adhesive materials to the surface.

4. Gunning of concrete surfaces.

The first three methods allow you to effectively get rid of damage to the protective layer, however, they do not directly improve the performance characteristics of the structure being repaired. In addition, these methods do not provide sufficient adhesion of new concrete or cement mortar to old concrete, and the protective layer obtained after restoration does not have acceptable strength, water resistance and corrosion resistance. The use of special adhesive compositions is complicated by the high cost of work and poor compatibility of the repair layer material with the material of the structure being repaired in terms of deformation properties.

Shotcrete can be used on surfaces with any irregularities located in any plane. The main advantage of shotcrete is the high adhesion strength of the repair layer to the surface of the structure being repaired. The concrete layer obtained after shotcrete has increased density, mechanical strength, water resistance and frost resistance. In addition, the physical and mechanical properties of the repaired concrete surface are significantly improved - bending strength increases by 40%, compressive strength by 15% and elasticity of concrete by 5 percent or more. Important advantages of shotcrete are high productivity (and, as a result, speed) and low cost of construction work.

There are two methods of shotcrete – “wet” shotcrete and “dry” shotcrete.

When using “wet” shotcrete, a mixture of cement, water and special additives is prepared in advance, and only then is supplied through a transport hose to the surface to be repaired. “Wet” shotcrete has the following advantages - uniform concrete composition, the ability to carry out work in tight spaces, minimal rebound, etc. This shotcrete method is used for repairing large surfaces (with an area of ​​2 thousand sq.m. or more).

With “dry” shotcrete, shotcrete and water are mixed only at the exit from the nozzle of the shotcrete installation. The use of the “dry” shotcrete method does not require preparation of the base of the surface to be repaired, allows you to apply a thick layer of shotcrete in one pass and makes it possible to carry out repair work intermittently (unlike “wet” shotcrete, in which the prepared mixture must be used continuously).

Thus, shotcreting of concrete surfaces is the fastest and most effective way to restore the protective layer of concrete. This method has been used in construction for many years. The fundamental principles of the company's work are high speed and quality of work, the use of advanced technologies and materials. Highly qualified specialists and extensive experience allow SDT LLC to guarantee the quality of work on restoring the protective layer of concrete using the gunite method. Here at this link you can learn in more detail about how shotcreting of concrete surfaces is carried out, prices and deadlines for completing the work.

Ultracolor Plus

High-quality polymer-containing quick-setting and fast-drying non-fading joint filler (from 2 mm to 20 mm) with the DropEffect® hydrophobic effect and BioBlock® antifungal barrier.

APPLICATION AREA

Grouting of floors and walls of internal and external cladding of all types of ceramic tiles (double fired, single fired, clinker and porcelain), terracotta, stone materials (natural stone, marble, granite, agglomerates, etc.), glass and marble mosaics .

Some application cases:

• Grouting floors and walls in places subject to heavy foot traffic (airports, shopping centers, restaurants, bars, etc.)
• Filling cladding joints on floors and walls in residential premises (hotels, private houses, etc.)
• Jointing on facades, balconies, terraces and swimming pools.

SPECIFICATIONS:

Ultracolor Plus is a blend of special hydraulic binders, high quality fillers, special polymers, additives, water repellents, organic molecules and pigments.

Ultracolor Plus, compared to Ultracolor technology, based on special hydraulic binders that guarantee excellent color uniformity, is complemented by advanced technologies developed as a result of MAPEI research: BioBlock® and DropEffect®.

BioBlock® technology is based on special organic molecules, evenly distributed in the composition, which block microorganisms that cause mold formation. DropEffect® technology is based on a synergistic effect that reduces water absorption of the surface.

Properties of Ultracolor Plus when mixed with water in the recommended proportion and correct technological application:

• water-repellent properties with the effect of forming a drop on the surface;
• uniform color and absence of stains; Ultracolor Plus does not fade. From the analysis made on an electron microscope, it is clear that, in comparison with Portland cement-based binders in conventional cement mortars for filling joints, special cements in Ultracolor Plus do not emit calcium hydroxide, the crystals of which cause color changes during the hydration process;
• color fastness to ultraviolet radiation and atmospheric agents;
• quick drying and easy to remove;
• readiness for foot traffic after a short period of time;
• smooth, dense surface with low water absorption and, as a result, easy cleaning;
• optimal abrasion resistance, compressive and bending strength, resistance to frost-thaw cycles and durability;
• good resistance to acids at pH > 3;
• compensated shrinkage therefore does not form cracks.

Concrete

To increase the strength characteristics of monolithic structures and increase their durability, a protective layer of concrete for reinforcement is necessary.

At the same time, their purpose is completely unimportant; they can serve as the basis not only for paving slabs, but also for a foundation or a swimming pool. In order for the concrete mixture to perform its functions, it is important not only to prepare it correctly, but also to use it on time, otherwise the structure may soon become unusable

Purpose of the protective concrete layer

Quite a large number of people involved in their own construction are completely unfamiliar with the concept of a “protective layer of concrete” and have no idea about its purpose. But thanks to it, as well as correctly laid reinforcement, the erected building will be less susceptible to destruction and will last a long time.

First of all, it is necessary to understand that the layer of concrete covering the reinforcement performs a protective function, preventing the negative effects of external factors on the metal

In addition, it is important to pour the cement mixture correctly, since even minor temperature changes and changes in humidity can affect the structure.

The protective layer of concrete for reinforcement should be of average thickness, which is determined based on the following factors:

• the type of structure being created and its purpose;
• the magnitude of the applied load;
• features of the environment in which the structure will be located;
• characteristics of reinforcement and the size of its section.

Taking into account all the necessary requirements, it can be noted that the concrete layer must protect metal elements from corrosion, aggressive external factors, and also ensure good interaction with reinforcement and cement mixture. An example of poorly done work can be seen on the streets of any city where there are areas covered with concrete slabs.

As a rule, each element “lives its own life” and has some kind of defect, for example, chips, cracks and exposed metal ligaments. All this is explained by the fact that the craftsmen incorrectly calculated the proportions of concrete and, as a result, it is not able to cope with its functions.

Regulatory requirements for concrete pavement

The preparation of protective concrete mixture for reinforcement must be carried out in accordance with established norms and rules, which will make it possible to create truly durable structures. For each type of object the following values ​​are provided:

• the thickness of the layer to protect structures inside buildings at low or normal humidity levels should be from 20 mm, and in conditions of high humidity - from 25 mm;
• products located outdoors should be filled with concrete with a layer thickness of at least 30 mm, and if there is no additional protection and the structure is placed in the soil - from 40 mm;
• when constructing foundations, a minimum of 40 mm must also be observed;
• the maximum thickness of the concrete layer, namely from 76 mm, is recommended in cases where the structure has constant contact with the ground.

The regulatory documentation additionally specifies values ​​for clamps and frames that have transverse metal elements. For example, if the height of the reinforcement section does not exceed 25 cm, then the concrete layer should be 10 mm; in other cases, the protective solution should be laid with a thickness of 15 mm or more.

To monitor compliance with the rules and regulations for laying a protective cement layer, special devices with magnetic sensors are used. With their help, it is easy to identify deviations from the norm up to 1 mm

It should be noted that in addition to following the rules for laying the mortar on the reinforcement, it is important to prepare it correctly, since it must have the necessary viscosity and strength to ensure reliable protection of the entire structure and withstand heavy loads

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Source: vest-beton.ru

Proper restoration

If the thickness of the pour is not taken into account at the construction stage, the protective layer of concrete for the reinforcement may collapse. Partial or complete exposure of steel bars should be restored. The complexity of the procedure is influenced by the size of the lesion, operating conditions and geometric characteristics of the structure.

In case of minor damage, restoration is easier to carry out using the plaster method. After removing the damaged layer, the areas are treated with a solution based on cement and sand. The mixture necessarily uses additional ingredients that increase resistance to moisture, cold and cracking. Professionals recommend adding 3-4 mm to the minimum protective layer of concrete. After polymerization of the composition, the surface is painted.

How to restore Source adgesia.ru

Pasting technology will help to quickly and efficiently restore reinforced columns or vertical structures. After thorough cleansing, the affected area is covered with a polymer-based material. The substance has high thermal insulation characteristics. The raw material holds well and protects steel bars from moisture.

Repair of a horizontal slab Source youtube.com

How much reinforcement is needed for 1 cubic meter of concrete?

The amount of reinforcement per 1 m3 depends on the type of reinforced concrete (slab or strip foundation, lintels over openings, monolithic ceiling) and its operating conditions; class of rolled metal and grade of concrete. If we are talking about the foundation, then the key parameters will be its type, the area of ​​the building, the weight and loads from its structures, soil, seismic hazard in the region and other factors that are taken into account by architects when designing in each individual case. For example, for a belt up to 60 cm deep, the frame is made in two levels, and with greater depth, their number is increased, placing rows in 40 cm increments.

The calculation is a complex technical task and only a specialized design organization can handle it. It must be carried out separately for different types of reinforced concrete structures (beam, foundation strip, column) and their operating conditions. For example, for ceilings the average consumption figure is about 110-120 kg/m3, and for columns - up to 350 kg per 1 m3.

For quantitative assessment, the reinforcement coefficient is used: μ = [Sa/(V∙H)]∙100%, where:

• Sa is the cross-sectional area of ​​the rods;
• B is the width of the product (slab, strip);
• H is its height.

How to repair the protective layer?

Even with the correct thickness, the concrete surface can collapse, this depends on exposure to weather conditions and the quality of the final finish. If you start repairing the surface in a timely manner, you can save the structure, while all chips, cracks, and depressions are repaired; sometimes a complete replacement of the layer is required.

1. Before performing the main work, the base is thoroughly prepared, that is, the surface is cleaned of dust or other contaminants.
2. After this, the restoration area is treated with a primer mixture.
3. Then the damaged areas are repaired, all chips, cracks, and significant differences are filled with a solution, after which the surface is leveled.

A complete replacement of the layer is performed when the quality of the material is lost, the main part of the frame is covered with corrosion, or significant delamination of the outer surface occurs.

How to ensure compliance with the required thickness of the protective concrete layer

In this publication, we will not dwell in detail on other rules for installing a reinforcement cage for a foundation. This is a very broad topic, and it is well covered in other articles on our portal.

If you read the recommended instructions (to which the links lead), it becomes clear that the size of the protective layer is laid down already when performing frame calculations and drawing up drawings of the future reinforcement structure. But how can this be observed in practice?

It is clear that the lower tier of reinforcement must be raised above the level of the bottom of the trench (pit) to the required height. Complete ignorance is demonstrated by those “masters” who use scraps of boards or timber remaining after installing the formwork as supports. Wood, firstly, is short-lived, and secondly, it will not become a barrier to moisture penetration. And in the places of such supports under the sole, areas for the spread of corrosion of steel reinforcement will inevitably appear.

An acceptable, but, frankly speaking, not the most ideal option is to use fragments of brick or concrete for lining. All the same, the “tightness” of the protective layer at the support points will be insufficient.

Prices for a concrete mixer

concrete mixer An acceptable option for supports for the lower tier of the reinforcing frame is fragments of brick or old concrete. But still – not without shortcomings.

The best option seems to be the use of special polymer racks. They are available in different heights, that is, it is possible to choose exactly the ones required for a given design. Their cost, especially compared to the overall costs of creating a foundation, is quite small. But they have a hollow structure, which will also be filled with concrete when pouring, and the reinforcement will be “sealed” with concrete along its entire length.

A special element is a plastic “glass” stand, which provides the required thickness of the protective layer on the side of the base of the foundation. Probably the most practical and reliable solution to the problem.

It is most convenient to do the same to create the necessary clearance between the external longitudinal bars and the formwork stacks. When pouring very heavy concrete mortar, the frame may move, and it must be securely fixed in a certain position. For this purpose, special fasteners are used—“stars” of the required radius. They are installed literally in one motion, and the problem is solved by itself.

What could be simpler - install “star” fasteners, and the required clearance between the reinforcement and the formwork will not be disturbed when pouring concrete mortar.

By the way, you can watch an interesting video in which a master shares the secret of making concrete clamps for reinforcement on his own. A very good option in cases where it is not possible to purchase special “glasses” or “stars”.

Video: How to make your own clamps to create a protective concrete layer

Immediately before pouring concrete, after completing the installation of the reinforcement frame, it makes sense to carefully inspect the created structure again. It happens that some transverse structural rod with its end is “dangerously approaching” the walls of the formwork. It is better to eliminate this immediately - trim it to set the required clearance. Otherwise, it is at this point that the concrete surface may chip and a surface crack may appear. And it’s good if everything is limited to this - it’s worse when such an area becomes a hotbed for the spread of large-scale concrete erosion.

*******

So, in order to create a uniform protective concrete layer, it is necessary to set up the reinforcing frame taking into account the established standards, that is, place the reinforcing bars at a given distance from the bottom and from the walls of the formwork. When pouring concrete mortar, it must be distributed as evenly and densely as possible throughout the entire formwork container. This will ensure an even distribution of loads, and the metal of the reinforcing “skeleton” will be properly protected from external influences, and therefore from the occurrence of corrosion. And this, in turn, is the key to the overall durability and reliability of the entire foundation as a whole.

How to follow the recommendations

The coefficients of the protective layer are laid at the stage of creating the foundation. The design must take into account regulatory requirements and exceptions. The optimal data is recorded in the plan. The frame of the lower structure is raised above the ground to the minimum thickness of the protective layer of concrete for the reinforcement. The mesh should not rest against the bedding.

To obtain cement supports, it is prohibited to use short-lived, moisture-permeable materials. Professionals recommend choosing models from:

• natural stone;
• polymer compounds;
• concrete.

When pouring, it is important to distribute the solution evenly over the formwork. Air bubbles, unevenness and heterogeneity should be avoided in cement. When working with heavy grades of building material, the frame is additionally fixed in one position. A thick mass can displace the structure, so “star” or “chair” fasteners are used. The parts are attached at the top of the structure using a latch.

Chair under fittings Source prorab2.ru

Options for different designs

Reinforcement of concrete structures is often additional, although more often it is a mandatory step in increasing the strength of concrete. Often, different solutions can be used as reinforcement: steel wire, steel rods of different diameters, plastic reinforcement, composite-polymer reinforcement. In addition, there are 2 types of connecting various types of reinforcing parts into one structure: binding using soft knitting wire and fastening elements using electric arc welding. And many are interested in the question of how best to combine the elements.

Of course, welding is usually used in industrial settings. Due to the fact that this process is very responsible, it is usually carried out only by specialists who are highly qualified and have extensive experience. And at home, of course, it would be better to use wire of 2-3 mm diameter. Sometimes it even makes sense to knit it in 2 layers. At least 50% of the intersections of individual structural parts and connections must be welded or connected at the same time. Next, we will consider in more detail the different options for various designs.

For floor and ceiling screed

To reinforce ceiling or floor screeds, a special metal grid or mesh is usually used.

For strip foundation

If it is necessary to reinforce a strip foundation, then use a welded or knitted version in the shape of a square, which consists of 4 reinforcement rods or more. Such a belt should be made along the entire foundation perimeter. This reinforcement option is considered one of the most reliable. It perfectly withstands all types of mechanical loads.

For columns and pillars

If it is necessary to reinforce columns, pillars and this type of foundation, a variation of the previous method is used. This method is called a variation because in the previous case everything was done horizontally, but here everything will happen vertically. To save metal, one or more rods can be used to reinforce vertical structures, which will only work in tension.

For large-scale foundation slabs

To reinforce large-scale foundation slabs or blocks of this type, so-called “combined” reinforcement is usually used. Sometimes it is also called double. Its essence lies in the fact that first a steel grid or mesh is laid, after which a reinforcing belt is installed inside the structure being poured. Moreover, this happens according to the same principle as in the cases described above.

Thickness of the protective layer of concrete

For each type of reinforced concrete structures, a different thickness of protection is sufficient. This parameter is regulated by regulatory documents, in particular SNIP 52-101-2003 (Concrete and reinforced concrete structures without prestressing reinforcement). The standards are described in the section Reinforced concrete structures. There are four main types of protection:

• The first (smallest) option is 20 mm thick. It is used in enclosed spaces where the humidity level does not exceed normal values.
• The next option is slightly thicker - 25 mm. It is used under similar conditions, but in the absence of additional protective measures.
• The 30 mm thick option is used outdoors, unless other protective measures are provided.
• The latter option has a minimum thickness of 40 mm and can be used in soils and foundations subject to concrete preparation.

An additional 5th option is used for those structures that are in direct contact with the ground. In this case, the recommended protection thickness is 70-75 mm. But some sources mention a smaller thickness.

There are also special specifications for specific reinforced concrete products, for example, columns, beams, slabs, blocks. The situation is similar with the requirements for different types of concrete, for example, light, heavy, cellular, etc.

Layer thickness requirements

The issue regulating the dimensional parameters of the protective layer is regulated by building codes in the document SNIP 52-01-2003. It is calculated by designers, indicating this value on working diagrams. The minimum recommended thickness of the concrete protective layer for reinforcement is affected by:

• type of fittings;
• diameter;
• function in reinforced concrete (structural or working);
• type of product (foundation, column, monolithic stairs, etc.);
• cross-sectional dimensions of the monolith and diameter of metal rods;
• environment.

Important! The minimum thickness of the protective layer of concrete for reinforcement must be at least its diameter and not less than 10 mm.

Table of the minimum thickness of the protective layer of concrete

When the structure does not have a developed design, it is recommended to fill the monolith using the values ​​from the table:

Basic indicators

When determining the minimum thickness of the protective layer of concrete, depending on the scope of use, choose:

• for prefabricated types of bases, it is preferable to fill a layer of 30 mm;
• in a prefabricated foundation with concrete preparation - 35 mm;
• in the absence of concrete preparation - 70 mm;
• SNiP standards have formed a rule for choosing the layer size for slabs, panels and walls at the level of 20 mm;
• in the area of ​​the base beams – 35 mm;
• when constructing columns - 20 mm.

The best protection for the frame is the concrete pour itself

Non-tensioned reinforcement

When a protective layer is used together with a non-tensioned metal frame, the concrete value should be taken to be no less than the diameter of the reinforcement bar. In the case of a slab with a thickness of 10 cm, a value of 1 cm is taken. Beams with a height of over 25 cm are treated with a 2 cm layer of cement. For the foundation, a protection layer of 3 cm should be laid. If a steel frame with a rod cross-section of 10 cm or more is laid in the solution, a protective layer is made 1 .5 cm.

Prestressed reinforcement

• In reinforced concrete structures with prestressed reinforcement, a protective layer is applied along the axis in the area of ​​load transfer.
• Its size is calculated using the formula 2*x, where x is the diameter of the metal rod.
• In some cases, a value of 3 times the diameter of the rod is accepted, but provided that the cross-section is greater than 20 mm.

It is important to create a distance between the reinforcements prestressed along the axis, but up to 2 cm

In industrial structures

For industrial structures, standards indicate the distinctive parameters of the formation in thickness:

• 2 cm – slabs, walls, creation of concrete foundations;
• 2.5 cm – columns, beams, trusses;
• 2 cm – underground structures.

The enclosing bed of concrete mortar depends on the conditions and parameters

To create a protective layer, concrete is placed on the end of the reinforcement stick:

• 1 cm – for structures up to 9 m;
• 1.5 cm – in 12 m buildings;
• 2 cm is used in reinforced concrete structures with a length of over 20 m.

Under negative environmental conditions

The type of reinforcement for different operating conditions differs significantly, as does the size of the protective layer:

• with preparation of the base from a water-cement mixture - from 4 cm;
• when the structure is in the ground or underground - 7.5 cm;
• for structures in contact with the ground and having a reinforcement cage - 5 cm;
• for structures operated in open areas - from 3 cm;
• in wet rooms made of reinforced concrete - 2.5 cm.

Characteristics of the protective layer

The porous structure of concrete protects the metal frame rods from the aggressive environment. According to GOST requirements, building materials and steel structures must interact tightly with each other. The correct width of the covering for the rods ensures the durability of the structure. Excess increases the consumption of the solution and the total mass of the building.

Main Factors

The thickness of the protective layer of reinforcement differs for each structure. The indicator of the fencing layer is influenced by 4 factors:

• Characteristics of rods. The larger the diameter of the steel part, the wider the concrete layer.
• Base load. The size of the protective layer for the reinforcement depends on the dimensions and weight of the structure.
• Terms of Use. Environmental characteristics (humidity, temperature) affect the width of the cement layer.
• The role of the frame. The functions of the foundation can be operational or constructive.

It is forbidden to determine the width of the protective layer approximately. The minimum protective layer of concrete should not be thinner than the cross-section of the rod. If the tier is less than 10 mm, then the structure is considered unprotected.

Corrosion processes Source rus-stroy.net

Recommended standards

To calculate limit values, there is a set of rules and special regulatory documentation. For longitudinal reinforcement of a strip foundation, the thickness should be 30 mm. Parameters for a monolithic base with preliminary cement preparation – 35 mm. For other options use 70 mm.

For transverse reinforcement of slabs and walls 10 cm wide, 10 mm of cement is sufficient. If the parameters of fencing structures are more than 100 mm, but less than 50, then take 15 mm. For large buildings with a diameter of more than 25 cm - 20 mm.

Minimum percentage of reinforcement in reinforced concrete structures

Let's consider what the minimum percentage of reinforcement expresses. This is the maximum permissible value, below which the probability of destruction of building structures sharply increases. If the indicator is below 0.05%, products and structures cannot be called reinforced concrete. A lower value indicates local reinforcement of concrete using metal reinforcement.

Depending on the characteristics of the load application, the minimum indicator varies within the following limits:

• with a coefficient of 0.05, the structure is capable of withstanding tension and compression when exposed to a load outside the working section;
• the minimum degree of reinforcement increases to 0.06% when loads are applied to the concrete layer located between the elements of the reinforcement frame;
• for building structures subject to eccentric compression, the minimum concentration of steel reinforcement reaches 0.25%.

Main function of the protective layer

The concrete layer between the reinforcement and the outer surface is designed to prevent moisture from penetrating the metal.

The thickness of the protective layer of concrete varies depending on a number of factors; standards have been developed for all variations. To create the required thickness, special clamps and substrates have been developed.

Minimizing contact with moisture and creating a barrier for it is the main task of the protective layer of concrete.

In addition, it is assigned a number of other functions:

• precise positioning of the reinforcement structure in the foundation;
• protection of metal from the effects of aggressive chemical compounds;
• ensuring uniform distribution of perceived loads, reliability during installation of waterproofing or finishing of the base;
• increasing the fire resistance of the structure.

Reinforcement table. Saint Petersburg

Reinforcement table

distributes various types of fittings in St. Petersburg and other settlements of the North-Western region.

Characteristics of fittings

We strive to do everything possible to simplify the selection of products, offering our customers tables reflecting the main properties of fittings.

First of all, you should pay attention to the values ​​that affect the quality of adhesion of products to concrete, presented below:

Reinforcing wire

Reinforcing ropes

It is necessary to have an understanding of the documents defining the characteristics of the fittings:

Legend + recommended diameters and classes of effective reinforcing steel for use, — — diameters and classes of reinforcing steel excluded from the assortment; 0 - assortment.

Notes: 1. The diameters of the reinforcement are taken in accordance with the assortment according to the relevant GOST or TU, taking into account the instructions for the scope of various classes of steel; diameters and classes of reinforcing steel excluded from the assortment; 0 - steel assortment - according to paragraphs. 2.18—2—25 SNiP P-21-75. 2. Steel of class A-IIIb with diameters of more than 20 mm, reinforcement strengthened by drawing at construction industry enterprises, is allowed for use as prestressed reinforcement in the absence of reinforcing steel of higher classes. 3. When manufacturing structures, it is allowed to replace class Bp-I wire with available class B-1 wire.

It is important to know the actual weight of reinforcement of a certain diameter:

Rebar weight table

Familiarization with the proposed valve tables will allow you to purchase products that are ideal for solving specific practical problems at minimal financial costs.

Scope of application of fittings

Smooth and corrugated reinforcement is widely used in construction. Durable reinforced concrete products, various metal frames, meshes, etc. are made from it.

Any fittings on favorable terms

is ready to offer customers fittings of various standard sizes. In addition to tables with the characteristics of the fittings, the website has a catalog with current prices for all products.

Order high-quality fittings with delivery throughout St. Petersburg and the region! You can get additional information about cooperation by phone!