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, when it gets wet, the internal pressure 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 for application such as: toxic waste sealing, landfill projects, tunnels and ponds.