Salty swelling bars are commonly used in waterproofing applications, particularly in below-grade structures such as basements and tunnels. The bars are made of bentonite clay, which expands when it comes into contact with water, forming a waterproof seal. The salty swelling bar is usually placed in a groove or joint in the concrete structure, where it can expand and create a tight seal. This helps prevent water from penetrating the structure and causing damage.