Reinforced concrete is Concept, definition, production, composition and application

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

One of the most popular building materials is reinforced concrete. These are durable slabs that are used during the construction of high-rise buildings. The material is able to withstand significant loads. It is not subject to the destructive influence of external adverse factors. Features of reinforced concrete, its production technology and application will be discussed in detail in the article.

General definition

Reinforced concrete is a complex structure made from concrete and steel bars. They work together to create a strong, durable material. Concrete is an artificial stone. It withstands compressive loads well, but responds poorly to tension. For this reason, a beam made of concrete is easily destroyed when bent. In the compressed zone, the potential of this material is enormous.

What building material is reinforced concrete? This is a more advanced version of an artificial stone made of concrete. He acquires completely different qualities,if steel bars are laid in its stretched zone before solidification. In this case, the reinforcement will take on such a force. Compressive loads are taken by concrete. Its tensile work is neglected in this case.

Reinforced concrete is a durable material that can withstand heavy loads. This can be achieved due to the presence in the structure of the material of not only longitudinal, but also transverse reinforcement. Such vertical rods are able to withstand tensile stresses closer to the supports.

In the composition of reinforced concrete, all reinforcing metal bars are connected by spot welding, resulting in a strong frame.

The cross-sectional area of transverse and longitudinal rods is determined during load calculations, and the method of combining such elements into a frame, as well as the number of such armored belts, depends on the convenience of welding, laying cement mortar and other factors.

The adhesion of reinforcement to concrete is an important condition for the joint work of these two materials. It is provided by the following factors:

1. There are special protrusions on the surface of the steel rods.
2. In the process of creating a steel structure at the intersection of a rebar, a bar of one type serves as an anchor for a product of a different direction.
3. Compression of bars is made by cement mortar in the course of its filling by shrinkage.

Product types

In the course of various construction works, the presented material is used. Reinforced concrete is produced in two mainvariations:

• beams;
• plates.

Slabs, unlike beams, have a larger width and a lower cross-sectional height.

Steel reinforcement, which is part of reinforced concrete, is highly durable. Therefore, it becomes expedient to use this material not only in stretched, but also in compressed elements. For example, it can be columns. The presence of reinforcement in such structural elements makes it possible to reduce their cross section. If the column is only made of concrete, it will be much thicker and therefore heavier.

This feature of the material allows you to reduce the cost of construction work, increasing their quality. Even with random eccentricities of longitudinal forces and loads of the transverse type, it is possible to maintain the integrity of the product or structure. This makes the material reliable and durable.

Rebar in reinforced concrete allows the use of material in the form of panels in high-rise construction. If earlier concrete of the M100-M200 brand was used for the manufacture of such panels, today cement M400-M500 is used. To create columns, you need material grade M900.

The rebar is protected from corrosion by a layer of concrete. Therefore, slabs and beams are used for outdoor installation, such as power lines, panel houses. In the construction of objects that will be subject to high heat, heat-resistant reinforced concrete is used. It is made of heat-resistant cement and hot-rolled rebar.

Advantages and disadvantages

Reinforced concrete is a modern, reliable material.

He has both advantages and disadvantages. The benefits of reinforced concrete include:

1. Durability. With the correct calculation of the load and operation of the structure in the conditions established by the manufacturer, the material serves indefinitely. At the same time, its bearing capacity is not reduced.
2. Less weight. To achieve the same strength indicators, a monolith structure must have a mass 5 times greater. Therefore, the weight of reinforced concrete is much less, which reduces construction costs.
3. Fire retardant.
4. Reliability. Good resistance to static and dynamic loads.
5. Affordable value. During the construction and operation of the reinforced concrete facility, the costs will be as low as possible.

The presented material also has disadvantages. It is worth noting that although the weight of reinforced concrete is much less than that of pure concrete products, it still weighs quite a lot. Therefore, in the course of modern production, light aggregates began to be used. Also, builders prefer thin-walled and hollow structures, while choosing a rational form of structural elements.

Reinforced concrete can crack. Up to a certain point, this circumstance does not reduce the bearing capacity of the material.

Besides, concrete has a high sound and heat conductivity. Therefore, during construction work, additional costs are required to create a layer of insulation and noise insulation.

Another disadvantage of the presented material isthe impossibility of control during the production of reinforced concrete product reinforcement. It will be quite difficult to strengthen the structure during the reconstruction of the building.

In-situ concrete

The production of concrete and reinforced concrete is regulated by the relevant standards. This allows you to provide the necessary operational qualities of the material. According to the installation method, reinforced concrete is divided into two groups:

1. Monolithic.
2. Assembly.

Previously, only monolithic structures were used during construction work. They were completely built from scratch at the construction site. They had exactly the location that was provided by the project. Monolithic reinforced concrete structures are created in several stages:

1. Installation of pre-prepared scaffolding, forms that are strengthened on them. These structures are designed for pouring cement mortar into them. Forms are called formwork, which are assembled from boards.
2. Installation of rebar frames.
3. Preparation of cement mortar and its pouring into the formwork.
4. Maintenance of the material during its curing. Optimum temperature and humidity levels are maintained. This allows the concrete to gain the required strength. Otherwise, cracks appear on its surface, and the bearing capacity decreases.
5. Removal of formwork, release of hardened cement from the prepared form when it reaches the required strength characteristics.

This is a rather lengthy process that has many nuances and subtleties. ATwinter time construction process requires additional costs.

Prefabricated Structures

The production of precast concrete has several distinctive features. This gives the material special advantages. In this case, the individual elements, such as columns, slabs, beams, etc., are manufactured in a production environment. Then they are transported to the construction site. Therefore, all reinforced concrete products that are produced at the plant are called prefabricated. This is true even for solid elements that do not consist of separate parts.

It should be understood that the foundation under the column, poured directly on the construction site, is a monolithic reinforced concrete structure. But the column itself is a prefabricated kind of material. It is brought to the site and installed on the foundation with a crane.

There are two ways to connect prefabs on site:

1. Rebar protrudes from structural elements. The joint is connected in place with a concrete solution. When it hardens, the joint acquires the properties of a monolithic structure.
2. In the production of prefabricated elements, the presence of embedded steel elements for fixing is provided. They come to the surface. Such clamps are securely fixed in concrete and have welded anchors. When assembling the structure, welding is used. After this, the joints are also poured with concrete. This protects embedded elements from corrosion.

Advantages of prefabricated structures

There are several advantages to using precast concrete. This technique is more modern. When using this technology, formwork turnover increases dramatically. It is used repeatedly, which saves timber. If reinforced concrete structures are used in mass prefabrication, not wooden, but metal formwork is used during production.

Speeding up the turnover of molds for production is achieved by speeding up the curing process of concrete. Products are steamed or fast-hardening cement mortars are used.

When using precast concrete structures, the construction period is significantly reduced. This can be achieved by combining different works in time. This is due to the advance manufacturing of all structural elements. Their installation is carried out using construction cranes. This procedure can be carried out at almost any time of the year.

At the same time, mechanization is actively used in the process of using precast concrete. You can create prestressed structural elements. This improves the quality and durability of reinforced concrete products. The labor intensity of the process and the consumption of materials are reduced.

Pre-tensioned material

During the production of reinforced concrete products, the method of creating a prestressed material can be used. In some cases, the formation of cracks in the place of tension is unacceptable. This requirement is put forward when creating tanks, structures that willbe exposed to aggressive environments, and more.

To eliminate the possibility of cracking at the point of tension, structures are made that have been prestressed. During operation, the likelihood of cracks and deformations is reduced. This improves the safety of systems operation.

Prestressed concrete production technology involves the creation of significant pressure and compression in the tension zone. This is how round blanks are obtained, products on the surface of which there are no cracks. The design uses pre-stretched strong reinforcement. This increases crack resistance, rigidity.

It is worth noting that the use of high-strength steel rods in the construction can reduce the cost of the product. The fact is that the price of such reinforcement decreases with an increase in its strength index. But it can only be used in designs with preload.

Ways

Concrete can be pretensioned in two ways:

1. Tensioning reinforcement on special stops.
2. Stretching directly on concrete.

In the first case, with the help of hydraulic jacks, the armature is stretched on the stops to a certain tension. This indicator should not exceed the established limit of elasticity. The fittings are fixed with ends in stops. Next, a cement mortar is laid out on the prepared frame. The rebar remains taut until the concrete hardens. Next, the ends of the reinforcement are released from the stops. She strives to takeoriginal position, while compressing the concrete.

If hot-rolled steel is used, it is not stretched with jacks, but heated. To do this, an electric current passes through the metal. The heated rods are firmly fixed in the stops. They are poured with concrete and released only after the mortar has hardened.

Tension on concrete

Rebar can be stretched after the concrete has hardened. To do this, channels are left in the solution. They remain even after the mixture has hardened. The rods are inserted into the channels. For this, hot-rolled reinforcement is used. Such rods are tensioned with a jack using a reactive transmission. This allows you to create a compression of concrete.

When the required force is reached, the reinforcement is fixed in this position. The equipment is turned off, but the tension of the reinforcement is maintained in the concrete. The channel is subsequently filled with cement mortar under pressure.

Material Handling

Reinforced concrete may need to be cut during construction or renovation work. In this case, special equipment is used. These are diamond drills that allow you to create door or window openings. In some cases, cutting reinforced concrete is used to dismantle partitions. This is how studio apartments are created during renovations.