Geotextile waterproofing mats are specialized geomembranes used for artificial lakes, landfill sites, underground parking garages, rooftop gardens, ponds, oil storage facilities, and chemical storage yards to prevent seepage. These mats are made by filling high-expansive sodium bentonite between a custom composite geotextile and nonwoven fabric, creating a needle-punched bentonite impermeable mat that forms numerous small fiber spaces. This prevents bentonite particles from flowing in one direction, and when water is present, it forms a uniform, high-density gel-like waterproof layer within the mat, effectively preventing water seepage.

The mineralogical name of bentonite is montmorillonite. Natural bentonite is mainly divided into two categories based on its chemical composition: sodium-based and calcium-based. Bentonite has the property of expanding when it comes into contact with water. Generally, calcium-based bentonite expands to about three times its original volume, whereas sodium-based bentonite absorbs water up to five times its own weight, expanding to 15-17 times its original volume. Locking sodium-based bentonite between two layers of geosynthetic materials serves as a protective and reinforcing function, giving the GCL a certain overall shear strength.