Rebar is included in poured concrete to reinforce and distribute load, compensating for the low tensile strength of concrete. Different lengths and thicknesses are used for different jobs, and rust-resistant polymer-coated rebar is used in certain situations.
When pouring concrete, several factors must be taken into consideration which will affect the strength of the final cured slab. Fluctuations in temperature, groundwater and air quality can affect the overall strength of poured concrete, so engineers needed to find ways to ensure the quality of the finished product. Today, metal bars called rebars are included in poured concrete to help distribute the load and reinforce the hardened concrete. Rebar is usually made of carbon steel and is cast with ridges for better adhesion to the concrete, and when set into the poured concrete, it strengthens the completed structure.
Concrete is a relatively strong substance once it has hardened, but it has low tensile strength and therefore does not adhere well to itself as it expands and contracts due to changes in weather or terrain conditions. Therefore, rebar is placed in the concrete to compensate for the low tensile strength of the concrete. It keeps concrete from separating, which can cause cracks and other weaknesses in the structure. Rebar is effective at holding the structure together because steel and concrete expand and contract at nearly the same rate, meaning the two are less likely to separate from each other.
Rebars come in different lengths and thicknesses to suit different types and sizes of jobs. They can be bonded together to form a grid or cage, especially useful for larger projects, and can also be used in other masonry applications. Brick and mortar structures are sometimes reinforced with rebar and is therefore known as reinforced masonry. Most load-bearing structures today employing the use of concrete will contain reinforcing bars, ensuring strength and longevity.
Because rebar is susceptible to rust, which can cause expansion and, in turn, cracking, it must be installed to the correct depth. If it is too close to the concrete surface, water could reach it, causing corrosion and rust. The concrete itself is usually sufficient to keep moisture from reaching the rebar, but in some situations, such as places near salt water or on bridges, it is necessary to use polymer-coated rebar that resists rust. This type of rebar is more expensive than ordinary steel rebar, but it can save the builder’s repair and rebuilding costs in the long run.
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