How is prestressed concrete different from reinforced concrete?

The primary difference between reinforced concrete and prestressed concrete lies in how the internal steel components interact with the concrete to manage structural stress.

• Reinforced Concrete: In this system, steel bars, rods, or mesh are embedded within the concrete to provide tensile strength. Because concrete is strong in compression but weak in tension, the steel acts as a partner to absorb tensile, shear, and bending forces, allowing the structure to sustain heavy loads over significant spans.12
• Prestressed Concrete: This method involves placing the concrete member into a state of permanent compression before it is subjected to external loads. By using pretensioning or posttensioning techniques, steel cables are stretched to compress the concrete. This internal compressive stress effectively neutralizes the tensile forces that would otherwise cause the concrete to crack under a load.31

Because prestressed concrete manages stress more efficiently, it allows engineers to design structures that are lighter, shallower, and capable of spanning greater distances than those built with traditional reinforced concrete.31