Short Answer:
Prestressed concrete is a special type of concrete where compressive forces are applied to the concrete before it takes any external load. This is done using high-strength steel tendons or wires to reduce tension in concrete during service. It helps in making the structure more crack-free, durable, and efficient.
It differs from RCC (Reinforced Cement Concrete) because in RCC, steel bars resist tension after the load is applied, while in prestressed concrete, tension is reduced in advance by pre-compressing the structure. This leads to higher strength, lesser cracking, and longer spans with smaller sections.
Detailed Explanation:
Prestressed concrete and its difference from RCC
Prestressed concrete is a modern and advanced form of concrete construction where internal compressive stresses are intentionally introduced before applying any external loads. This pre-compression helps counteract the tensile forces that develop under load and allows the member to perform better by reducing or eliminating cracks.
This is achieved by using high-tension steel wires or tendons, which are stretched (tensioned) and then anchored to apply compressive force to the concrete. The technique significantly improves the behavior of concrete under load and allows for slender, longer, and lighter structural elements.
How Prestressed Concrete Works
There are two main types of prestressing:
- Pre-tensioning – Steel wires are tensioned before casting concrete. After the concrete hardens, the tension is released, transferring stress to the concrete.
- Post-tensioning – Concrete is cast with ducts, and wires are tensioned after the concrete gains strength, using hydraulic jacks, then anchored.
The main purpose is to balance the expected tensile stresses during service by pre-applying compressive forces, thus keeping the concrete mostly in compression. Since concrete is strong in compression but weak in tension, prestressing enhances the strength and durability of the structure.
Difference Between Prestressed Concrete and RCC
| Feature | RCC (Reinforced Cement Concrete) | Prestressed Concrete |
| Load Handling | Steel resists tension after load is applied | Pre-compression reduces tension before load |
| Cracking | Cracks may form under tension | Cracks are minimized or prevented |
| Steel Used | Mild or HYSD bars | High-tensile steel wires/tendons |
| Member Size | Larger cross-sections needed | Slender and longer sections possible |
| Construction Cost | Less costly initially | Costlier but efficient in long-term |
| Application Areas | Residential, low-rise buildings | Bridges, flyovers, tanks, long-span beams |
Advantages of Prestressed Concrete
- Higher load-carrying capacity.
- Lesser chances of cracking and deflection.
- Long spans with smaller sections.
- Improved structural performance and safety.
- Reduced maintenance and longer lifespan.
Where Prestressed Concrete is Used
- Bridges and flyovers
- High-rise buildings
- Industrial structures
- Water tanks and silos
- Railway sleepers and precast girders
RCC is still widely used, especially in low-rise and normal buildings, due to ease of construction and lower cost, but for long spans and heavy loads, prestressed concrete is more efficient.
Conclusion:
Prestressed concrete is a high-performance material where internal compressive forces are applied to resist future tension, making the structure stronger and more durable. It differs from RCC by the way it handles tensile forces—before they appear. Prestressed concrete is ideal for long spans, heavy loads, and crack prevention, offering superior performance over traditional RCC in many structural applications.