Concrete is an incredibly strong material, but depending on the project and load it has to support, it can need a little help. Reinforced and prestressed concretes are two composite materials that keep us safe on the roads and in buildings, make walkways and patios long-lasting, and keep your home upright.
While reinforced concrete is used for different projects than prestressed concrete, there is one major similarity between them: both use steel to let the concrete handle the tension. However, the types of steel and the uses of the concrete are very different!
Reinforced Concrete And Its Uses
Concrete is great at resisting pushing or “compressive” stress. Stretching or “tensile” forces on concrete, however, can cause problems as large as a structural failure or as small as cracking on
your patio. To prevent this, the builders have to use steel, which has high tensile strength. They
also have to choose the right kind of support, and for structures, it’s usually reinforced concrete.
In this type of composite material, the reinforcing steel is either solid bars with ribbing (these reinforcing bars are better known as rebar) or a mesh. The reinforcements add enough tensile strength to allow a concrete slab to flex slightly without breaking apart. It can withstand the weight of foot traffic (as in your back patio) or an entire house (as in your foundation!).
Builders will use reinforced concrete to make street and road paving, sidewalks, foundation walls, dams, and other solid concrete forms that will be under a lot of compressive and tensile pressures.
Prestressed Steel And Its Uses
Prestressed steel uses solid bars or bundles of wire called “tendons” to create induced stresses throughout the entire structure and counteract tensile loads. Builders install the tendons under high tension, meaning the form itself is made under stress. The builders place the steel bars or wires in a form and stretch them on each end. They pour the concrete around the stressing bonds before releasing the pressure and creating the necessary tension. When the builders release the tendons, the steel tries to return to its original form, adding a lateral compressive force to the concrete and giving it strength over longer spans.
This process makes prestressed concrete more resistant to shock and vibration than regular concrete. It’s an innovation that allows builders to form long, thin structures with smaller sections that can support equal loads. The tendons in prestressed concrete let concrete span support weight between beams and piers on either side of a project. Without this type of reinforcement, the concrete would lack the tensile strength necessary to stand up under pressure, causing it to collapse.
Prestressed concrete is a key part of projects like bridges, highway overpasses, and commercial buildings. You’re not likely to find it around your home because prestressed concrete requires a high degree of workmanship. The special alloy steels it uses are also more expensive than steel found in reinforced concrete.