What is Prestressed Concrete? How Does it Work

When we talk about construction, the first thing that appears in our minds is concrete. Concrete is an integral part of construction and is widely used in this industry.

However, there are some restrictions related to its natural strength, especially the tensile area. But with the help of prestressed concrete, we can overcome all these shortcomings.

Prestressed concrete can be applied to stage bridges, beams, and heavy-load structures. Due to these numerous benefits, it is considered to be the first choice of engineers in modern-day construction.

With modernization and advancement in the construction industry, prestressed concrete is one of the best innovations. Prestressed concrete enhances the strength, durability, and flexibility of concrete.

What is Prestressed Concrete?

• Prestressed concrete is a kind of concrete where internal stress is applied to the concrete before external loads are applied to reduce the effect on the potential tensile stresses. This effectively strengthens the concrete thereby allowing the concrete to bear heavy loads with the least cracks and deformations.
• It reduces cost and extends the lifespan of structures and due to these reasons is considered to be the number one available option.
• Prestressed concrete is dependent on steel tendons & cables which are stretched within the concrete either before or after the concrete is cast.
• In the case of traditional reinforced concrete, there is steel reinforcement to manage the tension whereas in prestressed concrete the counterbalance in stresses is done by pre-stretching.
• So if prestressed concrete is compared with reinforced concrete always prestressed concrete is preferred as there are a lot of benefits attached to it like improving strength, durability, longevity, and less cost.

 Why is Prestressed Concrete Required?

• Traditional concrete contains compressive strength but there is a lack of breaking strength which causes crack formations under stress.
• Prestressed concrete counterbalances the external stresses due to the internal stress induced by compressive forces.
• This results in better performance, providing a longer life span to the structures, reducing structural thickness, and saving the material used as compared to normal reinforced concrete.

How to do the Prestressed Concrete works?

• Prestressed concrete is a concrete that is strengthened by prestressing or stretching with steel tendons or cables, often incorporating admixtures to enhance its properties.
• In this process, the tendons are stretched when the concrete is poured and cured  this helps the concrete to bear maximum load without any fracture when being pulled .

There are two types of Prestressing

1. Pre-tensioning

• In this technique, the high-strength steel wires & stands or steel tendons are tensioned or stretched before the concrete is poured.
• These tendons are held in the formwork and the concrete is poured once the concrete hardens up the tendons are let out and this provides the desired compressive force to the structure.
• Pre-tensioning is mostly used in factories producing components like slabs, beams, and railway sleepers.

2. Post-tensioning

• Post-tensioning is different from tensioning in this method the concrete is cast and allowed to harden first and then the tensions are applied to the tendons.
• After the concrete is  set the tendons are housed in ducts within the concrete and tensioned
• They are stretched and anchored after sufficient strength is gained by the concrete.
• These tendons are very often filled with material like grout to avoid corrosion and thus bond the tendons with the concrete.
• Post-tensioning is likely to be applied in structures like bridges, parking lounges, high-rise buildings, and structures for heavy loads.

Advantages of Prestressed Concrete

Due to the numerous benefits of prestressed, prestressed concrete is considered to be the best available alternate option for engineers.

The below points would prove this to be true.

• Load Bearing capacity – Prestressed concrete enhances the load-bearing capacity of the concrete thus allowing it to support heavy loads  structures to stand for longer period of time.
• Minimizing the crack formations– Prestressed concrete counterbalances external stresses by the internal stresses induced by the prestress which helps in the reduction of the risk of crack formation.
• Enhances Efficiency and Durability– The use of prestressed concrete helps in enhancing the efficiency of concrete in terms of strength and provides durability.

Concrete made through prestressing makes it more resistant to factors like corrosion, and environmental & chemical exposure.

• Reducing cost of maintenance- When prestressed concrete is opted for, initially the cost is more due to advanced materials and techniques used but its long-term benefits like longevity and durability reduce the maintenance cost required in the case of traditional concrete.
• All-rounder – The way through which prestressed concrete has brought tensile strength in concrete has opened up opportunities for many structural and architectural designs.

Prestressed concrete provides thinner slabs, extended life to structures, and extended open space due to which it is considered to be the best modern-day innovation in construction industries. 

Areas of Applications

Due to the tremendous advantages received by selecting prestressed concrete, it is being used in the below structures.

• Flyover & bridges – Due to the capacity of the prestressed concrete to bear heavy loads and take longer spans it is used in bridge and flyover constructions. It allows the structures to be durable and stable for a long time.
• Pavements and Railway sleepers- Prestressed concrete allows railway sleepers to give superior performance by withstanding loads with repeated train movements. It also provides longer spans to roads and airport pavements.
• High Rise buildings – In the case of tall buildings, prestressed concrete helps in providing thinner slabs and building slabs & columns with maximum utilization of floor space reducing the cost.
• Underground Tanks-Prestressed concrete is widely used in foundations like tanks and reservoirs as it has very good strength and leakage resistance.

Conclusions

Prestressed concrete has brought a very good change in the construction industry .Which lead to avoiding the restriction of relying on traditional reinforced concrete .

It had helped  meeting the challenges of modern-day constructions by giving benefits of stronger structure, durability, longevity, and flexibility, with reduction in cracks in a cost-effective manner which was not possible with the traditional method. It is considered to be the best innovation.  

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