What is the primary purpose of applying an overlay to a bridge deck?

The primary purpose of applying an overlay to a bridge deck is to protect the underlying structure from environmental damage and improve the riding surface for traffic. Overlays act as a barrier against water, chlorides (from de-icing salts), and other harmful substances that can penetrate the concrete and cause corrosion of the reinforcing steel. By preventing or slowing down this deterioration, overlays extend the service life of the bridge deck. Additionally, overlays can correct surface irregularities, improve skid resistance, and provide a smoother, more comfortable ride for vehicles. The overlay material, which can be concrete, asphalt, or a specialized polymer, is chosen based on its durability, impermeability, and compatibility with the existing deck.