Two grams of finely ground, dried bentonite are sprinkled slowly into a graduated cylinder of water, and the settled, swollen volume is read after at least 16 hours. Good sodium bentonite for GCLs typically reaches 24 milliliters or more. Low swell can point to poor-grade clay or to bentonite that has exchanged sodium for calcium, both of which raise permeability.
Swell index came back at 19, so this lot of GCL is on hold until we see the fluid loss too.
Also heard as
- free swell
- swell index test
Related terms
GCL
Geosynthetic clay liner: a factory-made barrier of sodium bentonite held between two geotextiles.
Conformance testing
Testing samples from rolls delivered to a site to confirm the material matches the specification.
Composite liner
Barrier made of a geomembrane in direct contact with a low-permeability soil or GCL layer beneath it.