What is the Pre-tensioned concrete

In Pre-tensioned concrete tendons are kept stretched with suitable mechanisms and concrete is cast into the forms through which stretched tendons pass, as shown in Figure. At the start, the prestressing force is not transferred into the concrete as tendons are kept in a stretched form using jacks and abutments from both the sides. When concrete gains sufficient strength (and hence has sufficient bond strength with tendons), stretched tendons are cut from outside. The stretched length of tendons falling inside concrete remains in a stretched state, due to its bond with concrete, and the prestressing force of tendons (which is of a tensile nature) is passed into concrete in the form of a compressive force. Depending on its magnitude, this compressive force reduces or eliminates the tensile stresses, produced due to external loads, in concrete.