Used as Waterproofing
Sodium Bentonite has the ability to absorb small amounts of water and to prevent the penetration of more water. This is similar to creating a molecular “ball valve” where in the transmission rate through it drops as you increase the pressure. Only the sodium bentonite generates the internal pressure when it gets wet necessary to form a waterproof seal. The confinement of wet bentonite prevents further expansion and therefore stops water absorption and/or penetration. This is the mechanism bentonite uses to waterproof buildings. This confining expansion of wet bentonite also gives it the capability to prevent water migration, to self-repair damaged areas and to reseal cracks that will occur from time to time in most concrete. Bentonite’s capacity to “self repair” and a potential life span measured in centuries (it is already up to 90 million years old) makes it the major sealing component of virtually all toxic waste and landfill projects. In combination with the strength and impervious qualities of high-density polyethylene (HDPE), bentonite/HDPE composite creates a strong, resealing waterproofing system providing waterproof protection for the lifetime of your building. The construction of permanent earthen dams, levees and ponds are rendered waterproof by the incorporation of bentonite products.
For the ultimate in multi-layered waterproofing system, bentonite clay is laminated on both sides of virgin HDPE membrane to form a waterproof barrier on both surfaces. This will eliminate water migration between building layers. The toughest projects (such as blindside installations, shotcrete lagging, underslab floors, and elevator pits under hydrostatic conditions) require an unmatched waterproofing system, with multiple layers in one membrane.
The fact that bentonite will form a waterproof seal to any impermeable material to which it is applied to or sandwiched between, makes it a vital component in the proper external placement of extruded polystyrene insulation because it forms a waterproof seal between the outside wall and the insulation. This feature allows the placement of insulation on the external side of the walls and floors of a building, thus placing the dew point temperature of the concrete in the insulation where it belongs, not on the interior wall where it can create condensation and nurture mold and mildew.