Reinforced concrete refers to a combination material composed of reinforced mesh, steel plates or fiber to the concrete. The main purpose is to change the mechanical properties of concrete. For example, it improves its shear resistance. It is a more wide structure of structural form. Many buildings adopt steel -reinforced concrete pouring.
The main materials of reinforced concrete are stone and sand. The proportion of steel and cement is relatively small in the materials used in the materials used. ,very convenient. From the perspective of the structure of reinforced concrete, concrete wraps tightly the reinforcement, and even in the environment of a corrosive medium, the concrete can be made into corrosion resistance through special processes to ensure that the building has been used for a long time. Not easy to occur.
Steel concrete is the abbreviation of reinforced concrete. The concrete is the combination of artificial stones. It is a building material similar to stone -like materials such as stone sandwiches and binding materials.
Steel concrete puts reinforced steel in it before pouring concrete, or penetrates the steel bars after pouring concrete (post -tension, prestressed steel concrete). High -grade building materials with high plasticity.
Steel concrete is a combination of reinforced tensile resistance and concrete pressure, which has a higher bearing capacity than concrete.
Different from the construction method: paddling, assembly, and assembly overall paddling steel concrete floor.
The paddling steel concrete floor is shaped by branches at the construction site, tied to steel bars, pouring concrete, maintenance and other processes.
Advantages: good overall, strong earthquake resistance, irregular shapes, can be reserved, convenient to arrange pipelines.
Disadvantages: template, large dosage, slow construction speed.
Prefabricated prefabricated reinforced concrete floor
Prefabrication at the prefabricated plant or construction site
Disadvantages: Poor of the floor of the floor, long cracks when the seams are not well embedded.
Concrete is a mixture of cement (usually silicate cement) and aggregate. When a certain amount of water is added, cement hydration forms a micro -transparent lattice structure to wrap and bind binding aggregate into the overall structure. Generally, the concrete structure has strong compressive strength (about 3,000 pounds/square inch, 35 mPa). However, the tensile strength of the concrete is low, usually only about one -tenth of the pressure resistance strength. Any significant bending effect will cause its micro crystal structure to crack and separate, leading to the destruction of the structure. The vast majority of structural components have the need to be stressed in the inside of the structural components. Therefore, the concrete without steel bars is rarely used in engineering alone.
Compared with concrete, the tensile strength of the reinforcement is very high. Generally, it is more than 200MPa. Therefore, it is usually worked together to add reinforced materials such as reinforcement to the concrete. For example, in Figure 2 In the bending component of the beam, when the load P is applied, the upper part of the beam section is pressed and the lower part is pulled. At this time, the steel bars configured at the bottom of the beam bear the tension, and the concrete ⑵ is underneath of the upper shadow area. In some small cross -section components, in addition to being tensile, reinforcement can also be used to bear pressure, which usually occurs in the pillars. The section of the reinforced concrete component can make different shapes and sizes according to the needs of the project.
The reason why reinforced concrete can work together is determined by its own material nature. First of all, the reinforcement and concrete have the same line expansion coefficient, which will not produce excessive stress from different environments. Secondly, there is a good adhesion between the reinforcement and the concrete. Sometimes the surface of the reinforcement is also processed into interval ribs (called deformation reinforced bars) to improve the mechanical bite between concrete and steel bars. When the concrete is tensile, the end of the steel bars is usually bent 180 degrees. In addition, the alkaline environment provided by calcium hydroxide in concrete, a layer of passivation protective film is formed on the surface of the reinforcement, making reinforcement less easily corrosive than in a neutral and acidic environment.
The tensile tendons in reinforced concrete are very small, from 1%of the section of the component section (more common in the beam board) to 6%(more common in columns). The cross section of the reinforcement is round. From 0.25 to 1 feet, 1/8 feet per level increased; in Europe, from 8 to 30 mm, 2 mm per level increased; in mainland China, it was divided into 19 and so on from 3 to 40 mm. In the United States, it is divided into 40 steel and 60 steel according to the amount of carbon in the steel bars. The latter has a higher carbon content, and the strength and stiffness are high, but it is difficult to bend. In the corrosive environment, electroplating, outer epoxy resin, and stainless steel are also used.
Under humid and cold climate conditions, reinforced concrete roads, bridges, parking lots, etc. The structure that may use ice salt should use epoxy resin steel or other composite materials. Essence
The frozen loop of the steel bars and the concrete
The frozen cycle of the rust of steel and concrete can cause damage to the structure of the destructive concrete. When the reinforcement is corroded, the rust is expanded, causing the concrete to crack and lose the binding force between the steel and the concrete. When water penetration of the concrete surface enters the interior, the volume of the frozen and concrete water is swollen. After repeated freezing and cyclic effects, the concrete can be cracking and deepened by micro. damage.
The pore water in the concrete is usually alkaline. According to the Pourbaix diagram, the reinforcement is inert when the pH value is greater than 9.5 and does not rust. The alkali reaction of carbon dioxide and cement in the air makes pore water more acidic, which reduces the pH value. From the formation of the component, carbon dioxide will carbonize the concrete on the surface of the component and deepen. If the component cracks, carbon dioxide in the air will be easier and easier to enter the inside of the concrete. In the process of structural design, the thickness of the minimum steel protective layer will be determined according to the architectural specifications. If the carbonization of the concrete weakens this value, it may cause structural damage caused by the corrosion of the steel bar.
The method of carbonization on the surface of the test component is to drill a hole on its surface and drip the phenolite. The carbonization part will become pink. By observing the discoloration part, you can know the depth of the carbonized layer.
Chloride, including sodium chloride, can corrode reinforced steel in concrete. Therefore, only water is allowed when mixing concrete. It is also prohibited to remove ice for concrete pavement.