What does Pre-stressing in construction involve?

Pre-stressing in construction involves the method of applying a compressive force to concrete before it is subjected to external loads. This is primarily achieved through techniques such as tensioning steel tendons or reinforcing bars within the concrete. When reinforcing bars are tensioned prior to pouring concrete, they create a pre-compression in the material, which helps counteract the tensile stresses that the concrete will experience when it is in service. This pre-compression enhances the performance and strength of the concrete structure, allowing for longer spans and greater load-bearing capabilities.

In this context, while other options mention relevant construction practices, they do not accurately define pre-stressing. Adding insulation to roofs is related to energy efficiency, while post-tensioning refers to a specific technique often used in conjunction with pre-stressing, but it occurs after the concrete is poured. Installing fire retardant materials pertains to fire safety measures, which are separate from the structural performance aspects addressed by pre-stressing methods.