While both are methods of prestressing concrete, they differ in when the tendons are tensioned:
Pre-tensioning: The steel tendons are tensioned before the concrete is cast. The tendons are stretched between fixed abutments, concrete is then cast around them, and once the concrete gains sufficient strength, the tendons are released. Prestress is transferred to the concrete through the bond. This method is typically used in precast manufacturing plants.
Post-tensioning: The tendons are tensioned after the concrete has hardened. Ducts or sleeves are cast into the concrete, tendons are threaded through these ducts after curing, then tensioned using hydraulic jacks and anchored at the member ends. This method is commonly used for cast-in-place construction and allows for on-site prestressing.
