Pre-tensioning is a technique used in construction and engineering to enhance the strength of concrete structures. It involves placing high-strength steel tendons or cables under tension before the concrete is poured. This process helps the concrete resist tensile forces, making it more durable and capable of handling heavy loads. Once the concrete hardens, the tension in the steel is released, transferring compressive forces to the concrete. This method is commonly used in precast concrete elements, such as beams and slabs, allowing for longer spans and thinner sections, ultimately improving the efficiency and performance of the structure.