GCL (Geosynthetic Clay Liner / Bentonite Blanket)

GCL (geosynthetic clay liner) is a needle-punched composite blanket of sodium bentonite sandwiched between geotextiles. When hydrated, the bentonite swells into a low-permeability gel that self-heals punctures — a puncture that would leak through a geomembrane seals itself in a GCL. No welding equipment is needed, which makes it extremely fast to install.

Specifications

Bentonite Content	≥4500 g/m² (sodium bentonite)
Standard	GB/T 21825 (Bentonite Waterproofing Blanket)
Permeability	≤5.0×10⁻¹¹ m/s
Swell Index	≥24 ml/2g (sodium bentonite)
Structure	Needle-punched, film-coated option available
Key Feature	Self-healing, no welding required
Roll Width	2 – 6 m, custom available

GCL vs Geomembrane — When to Use GCL

• GCL alone: artificial lakes, canals and landscape water bodies with moderate water head, where self-healing and fast installation are valued.
• GCL + HDPE geomembrane (standard landfill composite liner): GCL as secondary liner below the geomembrane — the two layers back each other up.
• Landfill capping: GCL is widely used in final covers because it conforms to irregular surfaces and tolerates differential settlement better than rigid liners.

Installation Notes

• Overlap edges with sodium bentonite powder or paste between laps (typically 150–300mm overlap)
• No welding — just overlap, place and cover; speed up to thousands of m² per day
• Cover promptly after placement to prevent premature hydration from rain
• Avoid long-term immersion without cover in high-head applications — design per project