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How can you tell when concrete needs extra reinforcement with rebar? One of the interesting things about concrete as a construction material is that it features high compression strength—but not so much tensile strength. Where tensile strength is needed, that’s where rebar is needed. It helps to prevent cracks when concrete is placed under tension.

To learn more, read below. We’ll dive into everything you need to know about rebar, and when it’s appropriate to use it.

When to Use Rebar

There are actually three different types of strain that concrete can experience. The first is compression, which is inward pressure—the concrete being compressed. Tension is the second type, which is where forces pull concrete apart rather than push it together, and shear is the third type, which consists of twisting or differential forces going in different directions.

On its own, concrete is strong against compression. However, where tension and shear are concerned, it’s much less resistant—and that’s when you need rebar, to reinforce it in applications where tension or shear are a concern.

So which applications experience tension and shear? The truth is, most construction applications will experience all three types of stress. For example, roads experience forces coming not only from the vehicles traversing it but also from the ground shifting beneath. Beams within buildings experience compressive strength from the building above, and without rebar, those beams are very likely to crack.

The real key to reinforcing concrete with rebar is choosing the right rebar for your particular application.

What is Rebar?

Understanding when to use rebar means learning a little bit about what it is and the different types available. “Rebar” is short for “reinforcing bar,” which is exactly the job that it does. It’s made from steel, and it can be used in both bars and mesh to help reinforce concrete.

Most of the time, rebar will come in what is known as “deformed bars.” These are bars that feature heavy ridges, which are designed to help give the rebar more grip inside the concrete. In other words, bars with ridges have less chance of slipping on the concrete surrounding them than smooth bars would, which is crucial to the reinforcement that rebar provides. There are some applications, however—like highways and bridges where that slip is necessary—in which plan, non-deformed bars are required.

When you use rebar in concrete, this not only increases the material’s strength, but it also allows you to reduce the thickness of the concrete. For instance, when pouring a concrete slab, if you don’t use rebar, you’ll need to pour it thicker to prevent cracks whereas if you incorporate rebar, you can pour a thinner slab.

Types of Rebar

The most common type of rebar, the one that most of us are familiar with, are the long steel bars with ridges. These are typically made from hot-rolled steel, and they are used in a broad variety of applications. But there are also a few other types that you should be aware of.

  • Welded wire fabric is steel product in which the wires are welded together at right angles to form a grid pattern. This type of rebar is ideal for slabs to help prevent cracks.
  • Stainless steel rebar is useful where corrosion might be a concern since this could save money on expensive repairs later on.
  • Epoxy coated rebar is another that, like stainless steel, resists corrosion due to the epoxy coating that seals over the metal. This is a good choice in corrosion-prone environments or where salinity is high, such as in marine environments.
  • Expandable metal is a sheet metal mesh that is installed in parallel lines which are then expanded into diamond and square shapes. It works best of thin concrete installations or even for plaster.
  • Sheet metal reinforcement is useful where more complex forms may be needed, like stairs, floors and rooftops.

It’s also important to be aware that rebar comes in a variety of diameters and tensile strengths, each with their own usages. Make sure to choose not only the right type for your project, but also the right size and strength.

Most projects can benefit from the addition of rebar for added strength against a variety of forces, but it isn’t a requirement for all projects. In particular, rebar is a must in applications that will experience high tension or shear, so keep the different types of force that will be applied to your project in mind as you choose the type of rebar that will work best.