Post-tensioning is a construction technique used to strengthen concrete structures. It involves placing high-strength steel tendons within the concrete before it hardens. After the concrete sets, these tendons are tensioned, or pulled tight, and anchored at the ends. This process helps to improve the concrete's ability to withstand tensile forces, making it more durable and resistant to cracking. This method is commonly used in various structures, including bridges, parking garages, and high-rise buildings. By using post-tensioning, engineers can create thinner slabs and longer spans, reducing the amount of material needed and enhancing overall efficiency in construction projects.