The protective layer of the reinforcement in reinforced concrete refers to the main reinforcement or

Ferroconcrete.

The protective layer of the middle reinforcement does not refer to either the main reinforcement nor the stirrups. Reinforcement cover.

The distance from the outer edge of the outermost rebar to the surface of the concrete. The distance from the outer edge of the outermost reinforcement to the concrete surface is: the distance from the outer edge of the stirrup to the concrete surface).

In the durability design, unless otherwise specified, this protective layer should be the protective layer of the outermost reinforcement, usually the stirrup protective layer. From the perspective of the durability of concrete carbonization, blunting and steel corrosion, the outer edge of the longitudinal stressed steel bar is no longer used, but the outermost steel bar (including stirrups, structural reinforcement, and distribution reinforcement).

etc.).

The reinforcement protective layer specifically refers to the distance from the outer edge of the outermost steel bar to the surface of the concrete, that is, the distance from the outer edge of the stirrup to the surface of the concrete.

Function. 1. Protect the steel bar from being corroded (water content in the air, the higher the carbon dioxide content in the air, the thicker the protective layer required).

2. Bonding and anchoring (the steel bar should be transmitted to the concrete through the protective layer, if the thickness of the protective layer is not enough, cracks will appear prematurely, and the steel bar can not be fully stressed, and at the same time, water and carbon dioxide can invade a lot and corrode the steel bar).

3. The inside of the steel bar is composed of countless triangles, not a straight plate, and is designed to withstand the protective effect of the vehicle.

Extended information: The reinforcement configured in the reinforced concrete structure can be divided into the following types according to its function:

1. Stress ribs - steel bars that bear tensile and compressive stress.

2. Stirrups - bear a part of the oblique tensile stress and fix the position of the stress bars, which are mostly used in beams and columns.

3. Erection bar - used to fix the position of the steel hoop in the beam to form the steel skeleton in the beam.

4. Distribution ribs - used in roof panels and floor slabs, arranged perpendicular to the stressed ribs of the slab, evenly transmitting the weight to the stressed ribs, fixing the position of the stressed ribs, and resisting the temperature deformation caused by thermal expansion and contraction.

5. Others - structural reinforcement configured due to component construction requirements or construction and installation needs. Such as waist bars, embedded anchor bars, prestressed tendons, rings, etc.

According to page 54 of 11G101-1, the thickness of the concrete cover refers to the distance from the outer edge of the outermost steel bar to the concrete surface, i.e., the stirrups.

Answer: The protective layer of steel bars in reinforced concrete refers to the outer edge of the outermost steel bar (including stirrups, structural bars, distribution bars, etc.) to calculate the thickness of the concrete protective layer.

See the elaboration of the "Code for Design of Concrete Structures" GB50010-2010 and the description of the provisions

Explanation of Provisions:

In reinforced concrete, the thickness of the concrete cover is calculated by the outer edge of the reinforcement "with the outermost reinforcement" refers to (stirrups, structural reinforcement, distribution reinforcement, etc.).

Paragraph 2 of the Code for the Design of Concrete Structures GB 50010-2010 (2015 Edition):

2 Concrete structures designed to have a service life of 50 yearsThe thickness of the protective layer of the outermost rebarshould be in accordance with Table 8provisions; Designed with a 100-year service life of tear concretion structuresThe thickness of the protective layer of the outermost rebarshould not be smaller than Table 8 2.

1 is a multiple of the value.

In the second paragraph of the explanatory article of the article explanatory article of the Code for the Design of Concrete Structures (GB 50010-2010 (2015 Edition), it is seen that the thickness of the concrete protective layer is calculated on the outer edge of the reinforcement in the current reinforced concrete "with the outermost reinforcement" refers to (stirrups, structural reinforcement, distribution reinforcement, etc.). "Calculate the thickness of the concrete protective layer by the outer edge of the longitudinal stressed reinforcement no longer by the outer edge of the outermost reinforcement (including stirrups, structural reinforcement, distribution reinforcement, etc.). Therefore, the actual thickness of the revised protective layer is larger than that of the original specification.

2. From the perspective of the durability of concrete carbonization, ravioli and steel corrosion, the thickness of the concrete protective layer is calculated by the outer edge of the outermost steel bar (including stirrups, structural reinforcement, distribution reinforcement, etc.) of the outermost reinforcement no longer by the outer edge of the longitudinal stressed reinforcement. Therefore, the actual thickness of the revised protective layer is larger than that of the original specification.

After the 2016 revision of the design code for concrete structures, the thickness of the protective layer was revised to the thickness of the concrete on the outside of the stirrups, which is more stringent than in the previous version. In this way, the stirrups will also be protected by the concrete and will not be easily rusted and damaged.

The thickness of the concrete reinforcement cover is calculated from the main reinforcement, that is, the concrete thickness from the inside of the stirrups to the outside of the building.

Concrete cover thickness – The distance from the outer edge of the outermost rebar to the concrete surface.

The current code requirement for stirrups refers to the distance from the outer edge of the reinforcement to the concrete surface.

The thickness of the reinforcement cover in reinforced concrete refers to the thickness of the cover layer of the outermost reinforcement.

According to the current "Code for the Design of Concrete Structures" GB50010-2010 (2015 Edition), the definition is as follows:

Note 1 on page 56 of the 16G101-1 atlas provides greater clarity on the distance from the outside of the stirrups to the concrete surface.

It is shown below. <>Thank you.

According to the relevant regulations, the concrete reinforcement protective layer should be calculated from the edge of the stirrups. Because the protective layer is defined from the outermost edge of the rebar. The vertical distance to the outer edge of the concrete. The thickness of the protective layer is related to the environment in which the concrete reinforcement is exposed.

Previously it was from the main reinforcement.

Now from the stirrups.

However, if it is a distribution rib that is not subject to force, it does not count.

The protective layer is calculated from the outermost layer of the outermost reinforcement.

The protective layer of the reinforcement in reinforced concrete refers neither to the main reinforcement nor to the stirrups. The steel bar cover is the distance from the outer edge of the outermost steel bars to the concrete surface.

The distance from the outer edge of the outermost reinforcement to the concrete surface is: the distance from the outer edge of the stirrup to the concrete surface).

In the durability design, unless otherwise specified, this protective layer should be the protective layer of the outermost reinforcement, usually the stirrup protective layer. From the perspective of the durability of concrete carbonization, blunting and steel corrosion, the thickness of the concrete protective layer is calculated by the outer edge of the outermost steel bar (including stirrups, structural reinforcement, distribution reinforcement, etc.) instead of the outer edge of the longitudinally stressed reinforcement.

Specification for the thickness of the rebar protective layer:

If it is a stressed steel bar, the thickness of the protective layer is 40-65mm, a layer of tensile steel bar is arranged in the beam and column, and the protective layer is 40mm thick, and two rows are arranged, and the protective layer needs to be 65mm thick; If it is a general steel bar, that is, the built-in steel bar of the floor and wall, the thickness ratio of the protective layer is 20mm, and if the strength level of the protective layer is below C25, it needs to be thickened by 5mm.

1. Look at the appearance.

Buying steel bars, presumably most people do not know how to judge the advantages and disadvantages, which can be preliminarily identified from the appearance of steel bars, so you need to carefully check the appearance of steel bars, the incisions at both ends of the steel bar remain straight, and there are no cracks, creases, scars and other defects on the appearance of steel bars, which are of better quality, on the contrary, they should not be purchased.

2. Look at the standard number.

Steel bars are mainly divided into four levels, and their tensile strength and toughness are different, because it is necessary to select the appropriate steel bar according to the use environment, that is, the use of steel bars, and steel bars are identified by the standard number, and only need to find the corresponding standard number, for example, if the reinforced concrete is combined, you can choose the steel bar with the standard number.

3. Look at the ingredients.

For example, in the stressed steel bar, manganese element is required not to exceed the silicon element to be controlled, and the sulfur and phosphorus elements should be less than. <>

The reinforced concrete protective layer refers to the concrete used to protect the steel bar from the outer edge of the steel bar to the surface of the component.

2 Terms and Symbols.

18 concrete protective layer.

concrete

The concrete used to protect the reinforcement from the outer edge of the reinforcement to the surface of the component in the cover structural member is referred to as the protective layer.

50010-2010 (2015 edition).

What is the reinforcement cover of building structure?

Count from stirrups.

The greater the thickness of the concrete protective layer, the better the bonded anchorage, durability and fire performance of the stressed steel bars of the component. However, too large the thickness of the protective layer will make the crack width of the component after being stressed too large, which will affect its performance, and the excessive thickness of the protective layer will also cause economic waste.

The thickness of the protective layer of the reinforcement on the bottom surface of the foundation should be calculated from the top surface of the cushion when there is a cushion, and should not be less than 40mm; It should not be less than 70mm when there is no cushion. The thickness of the reinforcement protective layer on the ground of the cap should not be less than the length of the pile head embedded in the cap.

The thickness of the protective layer of the steel bar, also called the thickness of the protective layer of concrete in some books, in the reinforced concrete structural component, the steel frame is poured in the concrete, because the chemical composition of the steel bar is more active, it is easy to be corroded in the air, in order to ensure the durability of the steel bar, but also for the concrete component to have a reliable and effective grip on the steel bar, it must be required to have a certain thickness of concrete around the steel bar skeleton to wrap the steel bar, The distance between the main reinforcement of the reinforcement or the outer skin of the stressed reinforcement and the outer surface of the concrete component, that is, the thickness of the concrete protective layer of the reinforcement, the thickness of the protective layer, must meet the requirements of the reinforced concrete construction specifications and procedures.

The thickness of the reinforcement protective layer not only directly affects the stirrup length in the reinforced concrete structure, but also affects the calculated length of the main reinforcement or the stressed reinforcement.

There are two forms of supply for steel bar products manufactured by steel mills, one is steel bar in the form of straight bars, and the other is steel bar in the form of disc circles. For the steel bar in the form of straight bars, we can directly cut and process the use, and for the steel bars in the form of disc circles, we can not directly cut and process, and before blanking, the steel bars first need to be straightened. There are two ways to straighten the rebar, one is to use the rebar straightening machine for straightening, and the other is to use a slow winch for stretching.

The diameter of the steel bar in the form of disc circle is generally not large, and the hot-rolled round first-class steel bar HPB235 with a diameter of less than 10mm is the main. In particular, the steel bars with a diameter of 6 mm and 8 mm are mainly supplied in the form of disc rounds.

When calculating the circular steel bar with a diameter of 6mm, it should be noted that since most of the steel mills in China produce this type of steel bar, they are all of the steel bars with a diameter, and the steel bar with a diameter of 6mm cannot be bought in the steel market. Therefore, here we must pay attention to the conversion and adjustment of the weight of the reinforcement, the diameter of the steel bar is 6mm, 22kg m, and the diameter of the steel bar, the difference between the two. Although this number is large from time to time, it already accounts for this part of the reinforcement project, which is a number that cannot be ignored.

It is also said that the diameter of the disc round steel bar is yes, but once it is stretched by the slow winch, it becomes a steel bar with a diameter of 6mm. In fact, it is a misunderstanding, you can think about it this way, if this theory is true, then the steel bar with a diameter of 8mm will not become a steel bar with a diameter after stretching? That's not to meet the requirements of the design.

Therefore, as the cost budget personnel of the project, the calculation of this part of the steel bar should be adjusted according to the diameter of the steel bar. In particular, as the budgeter of the construction unit, he should be more careful not to lose this part of the project. Of course, if you are the budget officer of the construction unit to review the budget, the construction unit can not give this part of the project regardless of what you want.

However, I do not approve of such a practice, as a project budget officer, whether it is done by the construction unit or in the construction unit, it should be based on the principle of seeking truth from facts, and I especially do not approve of the various practices of deducting the construction unit.

According to the description of the minimum thickness (mm) of the concrete cover layer in the table on page 54 of Atlas 11G101-1, the thickness of the concrete reinforcement cover refers to the distance from the outer edge of the outermost steel bar to the concrete surface.

According to the definition of the 2010 version of the new standard flat law atlas (11G101-1), the reinforcement protective layer is the distance from the outer edge of the outermost steel bar to the concrete surface.

So it's counted from the outer layer of stirrups.

The vertical distance from the outer surface of the longitudinally stressed steel bar to the edge of the section is called the thickness of the concrete protective layer. It is the distance from the outer edge of the longitudinal bar to the surface of the concrete, which cannot be regarded as stirrups.

As required by the new specification (10th edition of the concrete code), it is stirrups. According to the requirements of the old code (02 version of the concrete code), it is a longitudinal bar.

The thickness of the concrete reinforcement cover is calculated from the stirrups. The thickness of the concrete protective layer refers to the distance from the outer edge of the outermost steel bar (such as the outermost steel bar of the beam is naturally stirrups) to the concrete surface, so the thickness of the concrete steel reinforcement protective layer is calculated from the stirrups.