Bentonite can be used under structural or non-structural concrete floor slabs, below-grade foundation walls, between slab applications, under slab applications and along tunnels and subway walls. Bentonite is a type of clay having the unusual characteristics of cohesion, binding, sealing, and thickening. Usually gray in color and when processed has the consistency of fine powder, similar to cement. When installed below grade as a waterproofing membrane, it becomes hydrated with the moisture that is naturally present in the soil and forms an impermeable barrier that absorbs and expels water and chemicals. Bentonite can expand and contract an infinite number of times and is capable of absorbing seven to ten times its own weight in water, swelling up to eighteen times its dry volume.