Today we are going to talk about a fundamental topic in the construction of reinforced concrete structures: metal mesh.
Let's see why it is used, how it works and what benefits it brings to buildings. The combination of concrete and steel is one of the reasons why modern buildings are so strong and durable.
Introduction to concrete and its behavior
First, we must understand what concrete is.
This material is mainly composed of cement, water, sand and gravel.
One of its main characteristics is that it is very strong in compression, meaning it can withstand large weights when pressed. However, concrete has one major weakness: it is very brittle when it comes to traction.
This means that when pulled or subjected to tensile forces, concrete can crack and break.
Let's imagine a concrete block. If we apply a force from above (compression), the block will hold up without any problems. But, if we try to bend it, the block will break easily. This is a significant limitation for any structure we want to build.
The role of metal mesh
This is where wire mesh comes in. This material is made of steel rods that cross each other, forming a net-like structure.
Mesh is incorporated into concrete to improve its strength and durability. The metal mesh we are referring to is part of what is called reinforcement in reinforced concrete.
The mesh that makes up the armor must fulfill the following functions:
- Tensile Strength: By adding wire mesh, a material is introduced that can resist tensile forces. When concrete is subjected to forces that try to stretch or bend it, the mesh helps to withstand these stresses.
- Crack prevention: Mesh also helps control the formation of cracks. When concrete dries, it can shrink and, consequently, crack. Mesh acts as a reinforcement that holds the pieces together and prevents cracks from spreading.
- Load distribution: Mesh helps distribute loads across the structure. This is especially important in areas where weight is concentrated, such as in the beams and slabs of a building.
Bending stresses
Bending stresses occur when a force is applied to an object in such a way that it tends to bend it.
In reinforced concrete structures, this type of stress is common in elements such as beams, slabs and other components that support loads in a direction perpendicular to their length.
In the case of concrete beams, the wire mesh is generally placed at the bottom of the element.
When a load is applied to the center of the beam, compressive stresses are generated at the top and tensile stresses at the bottom. The wire mesh at the bottom resists these tensile stresses, preventing the beam from cracking or collapsing.
Types of metal mesh
There are different types of metal mesh used in construction, among which the following stand out:
- Electrowelded mesh: It consists of steel rods that are joined together by an electric welding process. This mesh is very common in the construction of slabs and pavements.
- Steel Reinforcement Mesh: This type of mesh is used in more specific applications, where greater strength is required. It is used in structures that support heavy loads.
- Stainless Steel Mesh: Used in environments where corrosion is a problem, such as structures exposed to weather or salt water.
How metal mesh is used in construction
Before pouring concrete, workers place the wire mesh in the proper location. It is raised slightly above the base where the concrete will be poured using small plastic or metal pieces called spacers to ensure that the mesh stays in the center of the concrete, where it can be most effective.
Once the mesh is in place, concrete is poured over it. This way, the concrete fills all the spaces between the mesh rods.
When the concrete sets, it adheres to the mesh, creating a strong bond that improves the properties of the material.
Benefits of using metal mesh
The combination of concrete and wire mesh increases the lifespan of structures. This is especially important in constructions exposed to adverse weather conditions, such as bridges or coastal buildings.
While wire mesh represents an additional cost in construction, its use can significantly reduce maintenance and repair costs over time. Structures that crack or collapse require costly repairs.
Structures reinforced with wire mesh are safer. In the event of an earthquake or unexpected load, the mesh helps prevent the structure from collapsing, protecting the people inside.
Examples of the use of reinforced concrete
Reinforced concrete is a construction material used in a multitude of applications. Here are some examples:
- Multi-storey buildings: In the construction of high-rise buildings, wire mesh is essential to provide the necessary strength to the slabs and beams that support the weight of the building.
- Bridges: Bridges use a mix of concrete and steel to ensure they are able to withstand the weight of traffic and external forces such as wind and vibrations.
- Paving: Concrete slabs for paving parking lots or streets also benefit from wire mesh, which helps maintain the integrity of the surface.
- Retaining Walls: In the construction of retaining walls, wire mesh is used to reinforce the concrete and prevent the wall from slipping or collapsing due to soil pressure.
- Nuclear power plants: Due to the strict safety regulations in the construction of a nuclear power plant and the structural demands, reinforced concrete structures in these facilities require additional reinforcement. Wire mesh helps ensure that the structures are able to withstand extreme forces and prevent failures that could have serious consequences.
Relevant data
The compressive strength of concrete can vary, but is typically measured in megapascals (MPa). For example, ordinary concrete may have a strength of 20-30 MPa, while high-strength concrete may exceed 60 MPa.
The steel used in wire mesh has a high tensile strength, typically between 400 and 600 MPa. This means that it can withstand high forces without breaking, thus complementing the limitations of concrete.
Conclusions
In conclusion, wire mesh is a vital component in the construction of concrete structures. It provides the strength needed to withstand loads and prevent cracks, ensuring that our buildings are safe and long-lasting.
The combination of concrete and steel has allowed the creation of more complex and resistant structures, from tall buildings to long bridges and nuclear power plants.
Next time you see a concrete construction, remember that there is a steel mesh working to keep everything in place, and that is what makes buildings safe and effective!