Concrete cast against PREFLEX 3000's thermo-reactive bonding surface forms an integral seal that holds through ground settlement and structural movement. It is passive and non-reactive, needing no water activation, bentonite hydration or confining pressure, so wet sites and early wetting do not affect it, and it resists groundwater, ground salts, chlorides, sulphates and hydrocarbons. The 1.7 mm composite records typical elongation of 1273% and water vapour transmission of 0.10 g/m²/24 h, and the factory self-adhesive selvedge gives watertight laps. Use it under basement slabs, on blindside retaining walls, and in lift pits, cut-and-cover tunnels and pile caps. Pre-applied only; not for permanently exposed use.