What is the process called when tendons are stressed before concrete is poured?

The process in which tendons are stressed before concrete is poured is referred to as pre-tensioning. In pre-tensioning, high-strength steel tendons are stretched prior to the placement of concrete. This is done by anchoring the tendons at each end of the concrete form, and the tendons are then tensioned using hydraulic jacks. When the concrete is poured and subsequently cured, it bonds to the tendons, which remain in a state of tension.

This method effectively places the concrete under compressive stresses, countering tensile stresses that will occur when the structure is loaded. By initiating a compressive force in the concrete, pre-tensioning enhances the overall load-bearing capacity and durability of the concrete element, helping to prevent cracking under service loads.

Understanding pre-tensioning is essential for engineers as it directly impacts the design and structural performance of prestressed concrete elements used in construction.