Solvent-free polyurethane that is injected. Upon contact with water, they form a dense foam that fills the voids in the concrete, sealing it. 

They are used for waterproofing and sealing of diaphragm walls or sheet piles, tunnels, and structures below the water table, as well as for recovering watertightness in areas that have suffered leaks or present wet cracks. 

Although they are mono-component, they can be combined with an accelerator to adjust the reaction time.