Which method of prestressed concrete fabrication is tensioned both before casting and after curing?

The correct choice, indicating that a method of prestressed concrete fabrication involves tensioning both before casting and after curing, is a combination method. Combination prestressing refers to the integration of both pre-tensioning and post-tensioning techniques.

In pre-tensioning, the steel tendons are stretched before the concrete is poured. After curing, the tension is released, allowing the concrete to be anchored against the steel, introducing compressive stresses that improve its resistance to tensile forces. In post-tensioning, tendons are placed in ducts within the concrete and are tensioned after the concrete has cured, directly stressing the structure.

Both methods can be effectively used in conjunction to optimize the performance characteristics of the concrete, allowing for enhanced load-carrying capacity and improvements in overall structural integrity. This hybrid approach allows engineers to leverage the advantages of both techniques, leading to increased flexibility in design and application.