One of the most popular building materials is reinforced concrete. These are durable plates 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 of concrete and steel bars. They work together to create strong, durable material. Concrete is an artificial stone. It withstands compression loads well, but does not respond well to tension. For this reason, a beam made of concrete collapses easily when bent. In the compressed zone, the potential of this material is huge.
What building material is reinforced concrete? This is a more advanced version of artificial stone made of concrete. It acquires completely different qualities if steel bars are laid in its stretched zone until solidification. In this case, the reinforcement will take on such an effort. Concrete takes over compressive loads. His 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.
As part of reinforced concrete, all reinforcing metal bars are joined by spot welding, as a result of which a strong frame is formed.
The cross-sectional area of the 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 armo-belts depends on the convenience of welding, laying cement mortar and other factors.
Adhesion of reinforcement to concrete is an important condition for the joint work of these two materials. It is provided by the following factors:
- On the surface of the steel rods there are special protrusions.
- In the process of creating a steel structure at the intersection of reinforcement, a rod of one type serves as an anchor for a product of a different direction.
- The compression of the rods is done with cement mortar during its pouring by shrinkage.
Product Types
During various construction works, the material presented is applied. Reinforced concrete is produced in two main variations:
Plates, unlike beams, have a larger width and a lower cross-sectional height.
Steel reinforcement, which is part of reinforced concrete, is highly durable. Therefore, this material becomes appropriate to apply not only in stretched, but also in compressed elements. For example, it can be columns. The presence of reinforcement in such structural elements allows to reduce their cross section. If the column consists only of concrete, it will be much thicker and, accordingly, heavier.
This feature of the material allows 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.
Reinforcement in reinforced concrete allows the use of material in the form of panels in high-rise construction. If earlier for the manufacture of such panels used concrete grade M100-M200, today cement M400-M500 is used. To create columns you need material of the M900 brand.
The fittings are protected against corrosion by a layer of concrete. Therefore, slabs and beams are used for outdoor installation, for example, power lines, panel houses. During the construction of facilities that will be subject to high heat, heat-resistant reinforced concrete is used. It is made of heat-resistant cement and hot rolled fittings.
Advantages and disadvantages
Reinforced concrete is a modern, reliable material.
It has both advantages and disadvantages. The advantages of reinforced concrete include:
- Durability. With the correct calculation of the load and operation of the structure under the conditions established by the manufacturer, the material serves an indefinitely long time. At the same time, its bearing capacity does not decrease.
- Less weight. To achieve the same strength indicators, a monolith structure must have a mass of 5 times more. Therefore, the weight of reinforced concrete is much smaller, which allows to reduce construction costs.
- Fire resistance.
- Reliability. Good resistance to static and dynamic loads.
- Reasonable cost. During the construction and operation of a reinforced concrete facility, costs will be as low as possible.
The material presented has its drawbacks. It is worth noting that although the weight of reinforced concrete is significantly less than that of products from pure concrete, it still weighs quite a lot. Therefore, in the course of modern production began to use lightweight aggregates. Builders also prefer thin-walled and hollow structures, while choosing a rational form of structural elements.
Reinforced concrete may become cracked. Until a certain point, this circumstance does not reduce the bearing capacity of the material.
In addition, concrete has increased sound and heat conductivity. Therefore, during construction work, additional costs are required to create a layer of insulation and sound insulation.
Another disadvantage of the material presented is the inability to control the reinforcement of the product during the production of reinforced concrete. When reconstructing a building, reinforcing the structure will be quite difficult.
Monolithic concrete
Concrete and reinforced concrete production is regulated by 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:
- Monolithic.
- Prefabricated.
Previously, exclusively monolithic structures were used during construction work. They were completely created from scratch at the construction site. They had exactly the location that was provided for by the project. Monolithic reinforced concrete structures are created in several stages:
- Installation of pre-harvested scaffolding, forms that are attached to them. These structures are intended for pouring cement mortar into them. Forms are called formwork, which is assembled from boards.
- Installation of frameworks from fittings.
- Preparation of cement mortar and pouring it into the formwork.
- Material care in the process of hardening. The optimum temperature, humidity level is supported. This allows concrete to gain the required strength. Otherwise, cracks appear on its surface, and the bearing capacity decreases.
- Removing the formwork, the release of hardened cement from the prepared form upon reaching the required strength characteristics.
This is a rather lengthy process, which has many nuances and subtleties. In winter, the construction process requires additional costs.
Prefabricated structures
Precast concrete production has several distinctive features. This gives the material special advantages. In this case, individual elements, such as columns, slabs, beams, etc., are manufactured under production conditions. Then they are transported to the construction site. Therefore, all products made of reinforced concrete, which 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 variety of material. It is brought to the object and installed on the foundation with a crane.
There are two ways to connect prefabricated structures at the construction site:
- Of the structural elements stands reinforcement. The joint in place is connected using a concrete mortar. When it hardens, the joint acquires the properties of a monolithic structure.
- In prefabricated elements during production, the presence of embedded steel elements for fixation is provided. They protrude on the surface. Such clamps are firmly fixed in concrete and have welded anchors. When assembling the structure, welding is used. After this, the joints are also filled with concrete. This protects the embedded elements from corrosion.
The advantages of prefabricated structures
There are several advantages to using precast concrete. This technique is more modern. When using this technology, the formwork turnover increases dramatically. It is used repeatedly, which saves timber. If reinforced concrete structures are used in mass prefabrication, metal formwork is used during production, not wooden.
Acceleration of the turnover of molds for production is achieved by accelerating the process of hardening concrete. Products are steamed or apply quickly hardening cement mortars.
When using prefabricated reinforced concrete structures, the construction period is significantly reduced. This can be achieved through the combination of different works in time. This is due to the advance manufacture of all structural elements. Their installation is carried out using construction cranes. This procedure can be carried out almost at any time of the year.
At the same time, in the process of using precast concrete, mechanization is actively used. You can create structural elements with prestressing. This improves the quality and durability of reinforced concrete products. The complexity of the process and the consumption of materials are reduced.
Pretensioned material
During the production of reinforced concrete products, a method of creating a prestressed material may be used. In some cases, the formation of cracks in the place of extension is unacceptable. This requirement is put forward when creating reservoirs, structures that will be exposed to aggressive environments, and another.
To exclude the likelihood of cracks in the place of tension, make structures that have been prestressed. During operation, the likelihood of cracks and deformations is reduced. This increases the safety of system operation.
The technology for the production of pre-stressed reinforced concrete involves the creation of significant pressure and compression in the tensile zone. This produces round billets, products on the surface of which there are no cracks. The design uses pre-stretched durable reinforcement. This increases crack resistance, rigidity.
It should be noted that the use of high-strength steel rods in the design allows to reduce the cost of the product. The fact is that the price of such reinforcement decreases with an increase in its strength indicator. But it can only be used in pretensioned constructions.
Ways
Concrete can be prestressed in two ways:
- Reinforcement tension on special stops.
- Tension directly to concrete.
In the first case, with the help of hydraulic jacks, the reinforcement is stretched on the stops to a certain voltage. This indicator should not exceed the established elastic limit. The fittings are fixed by the ends in the stops. Further on the prepared frame spread cement mortar. The reinforcement remains stretched until the concrete hardens. Further, the ends of the reinforcement are released from the stops. She seeks to take its original position, while squeezing concrete.
If hot rolled steel is used, it is not pulled with jacks, but heated. For this, an electric current passes through the metal. Heated rods are firmly fixed in the stops. They are poured with concrete and released only after the solution has hardened.
Concrete tension
The reinforcement can be stretched after the concrete has hardened. For this, channels are left in the solution. They remain after curing the mixture. The rods lead into the channels. Hot-rolled fittings are used for this. Such rods are pulled with a jack using a reactive transmission. This allows for concrete compression.
When the required force is reached, the reinforcement is fixed in this position. The equipment is turned off, but in concrete the reinforcement tension is maintained. The channel is subsequently filled under pressure with cement mortar.
Material processing
During construction or repair work, reinforced concrete cutting may be required. In this case, special equipment is used. These are diamond drills that allow you to create door or window openings. In some cases, reinforced concrete cutting is used to dismantle partitions. So during the repair create studio apartments.