In the field of waterproofing in water table or below-ground applications, bituminous systems can fail through ageing or tearing. Sodium Bentonite overturns this limitation: it is an active and millennial material that uses water itself as a motor to seal the building.
Sodium bentonite is a volcanic clay. Its ‘sodium’ variant (natural or activated) is composed of over 75% Montmorillonite, a layered mineral. Water penetrates between these lamellae, causing extraordinary swelling of 15–20 times its dry volume. When confined between wall and backfill, the bentonite transforms into an impenetrable gel, creating an absolute hydraulic barrier.
The bentonite powder is encapsulated between two layers of geotextile to form a GCL (Geosynthetic Clay Liner). This is nailed directly against the foundation wall. The greatest advantage over plastic membranes is its self-healing capacity. If the concrete wall cracks due to structural settlement (micro-cracks up to 2 mm), the bentonite gel expands autonomously inside the crack, sealing it permanently.
Standards
European and international references applicable.
Physical properties
Usage environment
Bentonite works EXCLUSIVELY in compression. If left unconfined (not held by heavy backfill or a concrete counter-wall), contact with water will simply turn it into an ineffective muddy mass. RISK: in contaminated soils (landfills) or coastal zones (saltwater), sodium is chemically replaced by calcium ions, blocking expansion. Use polymeric bentonite GCL in these cases.