How can concrete be reinforced

View Full Term. By clicking sign up, you agree to receive emails from Corrosionpedia and agree to our Terms of Use and Privacy Policy. Reinforced concrete is a building material in which two or more materials with different physical properties are used to impart a higher tensile strength and ductility to a building's structure. The purpose of reinforcement is to mitigate the tensile stresses that a building structure faces on a regular basis due to natural weather conditions. The reinforcement of concrete is often accomplished with the use of steel reinforcement bars or rebars, but it can also be done by using additional concrete passively.

The reinforcement materials usually consist of steel, composites or polymers, which impart strength, ductility and reinforcement to a concrete structure.

Subscribe to our newsletter to get expert advice and top insights on corrosion science, mitigation and prevention. By: Della Anggabrata. Reinforced Concrete is the common term given to a concrete member or slab that contains steel reinforcement usually in the form of steel bars to increase the strength of the structure.

The material that results from the combination of concrete and reinforcing bars is called Reinforced Concrete RC. During construction, the reinforcement steel is placed in the formwork first, either in the form of a prefabricated steel cage or steel rebars that are fastened together and wired in-situ. Then concrete is poured into the formwork and vibrated using adequate devices so as to guarantee a high level of collaboration between the two materials.

Figure 1: Rectangular concrete beam, with steel rebar, is an example of a reinforced concrete member. One of the main disadvantages of concrete is its very low tensile strength that is practically exceeded at low levels of load.

This results in cracking of the concrete surfaces that in turn leads to aesthetical problems large deflection of beams or slabs for the serviceability limit state as well as structural integrity problems at the ultimate limit state.

On the other hand, reinforcing steel has rather high tensile strength and a symmetrical material constitutive law under tension and compression. However, rebar alone that is subjected to compression fails prematurely due to buckling. For these reasons, the use of reinforcement in an RC section leads to effective structural behavior as reinforcing steelworks effectively under tension and concrete works effectively under compression and confines the compression reinforcement.

View all Documents on Reinforcement in Concrete ». E-2 00 Reinforcement for Concrete. CCS-4 20 : Shotcrete for the Craftsman. View all free presentations on Reinforcement in Concrete ». Reinforcement in Concrete Definition: bars, wires, strands, fibers, or other slender elements that are embedded in a matrix such that they act together to resist forces.

Reinforcement for concrete is provided by embedding deformed steel bars or welded wire fabric within freshly made concrete at the time of casting. The purpose of reinforcement is to provide additional strength for concrete where it is needed. It seems to only indicate that concrete should not be used as a rope.

Imagine a horizontal concrete beam, on which pressure is applied down from the top. This would be similar to walking on a concrete 2nd story floor. On the top of the concrete beam, the force is compression, as the concrete is pressed together. On the bottom, however, as the beam bows, the concrete is pulled apart by a force of tension. This is where plain concrete fails. Concrete is also weak against shear forces, which cause the material to move along a line or plane.

A non-reinforced concrete wall would crumble if it experienced too much shear force from:. As we can see, plain concrete is useful if you only apply weight directly down onto it, such as the base of a statue. Modern buildings, however, have to withstand pressure from many types of sources in all types of direction. Without reinforcement, plain concrete will simply fail under these conditions. When plain concrete fails, it does so suddenly.

One moment the concrete is intact, and the next moment, when the force is greater than the concrete can withstand, it crumbles or breaks into pieces. This sudden breaking is known as brittle mode failure. The main disadvantage of this type of failure is that there are no visual warning signs.

Unless you know the specific strength of the material and are actively measuring the amount of stress applied to the material conditions which are absolutely unfeasible outside of a laboratory setting there is no way of predicting failure. Reinforced concrete, on the other hand, experiences ductile mode failure.

This means that cracks begin to form before the concrete completely shatters. This is because though the concrete has been stretched further than it can stand alone, the steel rebar still holds the structure together. If the structure is only subject to compressive forces such as a slab of flooring these cracks might not be a big deal. Unless water is likely to infiltrate the crack and undermine the structure by rusting the rebar or expanding the fissure when freezing, the cracks will simply be pressed together by further compression.

In other situations, cracks signify the need to repair the area. In order to be as versatile as it is, concrete needs to be reinforced by some material that overcomes these weaknesses. Steel is used to reinforce concrete more often than any other material. The reason steel is used to reinforce concrete is because steel has several properties that make it particularly suited for this application. Ductility is a measure of how much deformation a material can undergo before breaking.

Concrete has very low ductility. If you twist a chunk of concrete with enough force, it will crumble in your hands. Wood, for example, is somewhat ductile, in that you can bend it a little bit before it will break. Steel, though, is highly ductile. If you bend it, it will simply stay bent. Steel ductility is useful before the cement is poured because it can be bent into whatever shape will best support the form that is to be poured.

When enough force is applied to the structure to deform it, the concrete may crack, but the steel rebar will maintain intact in the deformed shape. Often the steel is still able to support the structure until it can be repaired or replaced.

When solids are heated, the molecules within the materials move faster. These more active atoms take up more space the faster they move, so each molecule, and therefore the material as a whole expands.

The opposite happens when a solid is cooled. The net result is that solids expand when heated and shrink in size when cooled. While this is universally true among solids, it happens at different rates for different materials. In an extremely fortuitous coincidence, steel and concrete have very similar coefficients of thermal expansion. This means that when they are subject to heat or cold they expand or shrink at essentially the same rate.

If this were not the case, steel would be a poor choice to reinforce concrete. Imagine a corn dog, for example. If when cooked the hot dog doubled in size while the cornbread only grew a little bit, the hot dog would quickly burst through the cornmeal.