What Is Prestressed Concrete | Advantages and Disadvantages of Prestressed Concrete

Prestressed Concrete is simply concrete that is stressed before concrete is poured in from work with the help of a jack and tension embed in it.

In the case of prestressed concrete, high-strength prestressed steel bars produce tension in a concrete member before actual loads are applied which will be balanced by the tensile stresses imposed on the member during the service period or after commissioning.

As we generally know that concrete is the mixture of three main ingredients which are cement (a fine mixture of clay, limestone, and a small amount of gypsum ground up to the desired degree of fineness), sand (only river sand or obtained through pit) and aggregate (Made form blasting and grinding from rocky soil) and when we add water (free from impurities) in this mixture it creates concrete which we use for various civil work.

One of the main important characteristics of concrete or drawback of concrete is, that it is weak in tension and strong in compression because the material used in concrete is rigid and posse’s low tensile/flexural strength.

Under such a circumstance we have to adopt different kinds of methods and one of the most commonly adopted methods is the prestressing of concrete

Prestressed Concrete Structures

Conventional concrete has embedded with high tensile strength steel bars which have great compressive strength to form ideal structural material which is good in both compression and tensile.

In the case of prestressed concrete, high-strength prestressed steel bars produce tension in a concrete member before actual loads are applied which will be balanced by the tensile stresses imposed on the member during the service period or after commissioning.

As you can see in fig. 1 which is a normal R.C.C beam where no prestressing is done beam will deflect under loading and the crack will develop.

In the pre-tensioning process, the steel tendon is stretched before the concrete is poured into the formwork.

Then High–strength Steel Tendons are placed between two abutments and stretched as per the required deflection or strength.

After that Concrete is poured into molds and around the tendons and allowed to cure. Tendons are kept stretched until the desired concrete strength is reached after curing.

As the steel reacts to regain its original length, the tensile stresses are translated into compressive stress in the concrete.

The most popular prestressed concrete elements are roof slabs, piles, poles, bridge girders, wall panels, and railroad ties.

Advantages and Disadvantages of Prestressed Concrete

Advantages of Prestressed Concrete

• We can achieve the overall economy as by adopting prestressing we can reduce the of the er for higher load smaller C/S can be achieved.
• A large span can be achieved without increasing the member size for the same loading condition.
• Other advantages, such as excellent fire resistance, low maintenance costs, elegance, high corrosion resistance, adaptability, etc.
• By adopting prestressed concrete we can achieve a structure that will have less crack or crack-free structure.
• Because of better material being used and nullifying the effect of dead loads, smaller deflections are caused.

Disadvantages of Prestressed Concrete

• The cost of high-strength materials being used is higher than the normal RCC.
• The initial cost is incurred due to the prestressing equipment and its installation.
• Excessive cost for prestressing is also there.
• Prestressing is uneconomical for short spans and light loads.