Expansive Soils List Expansive Soils List RareBugRA (Structural) (OP) 16 May 17 21:41 Hello. I am looking for a list of expansive soils. Can someone share a link. I have identified the soil as UtD per USDA, I would like to know more types to be aware of. This is for personal reference. Thanks! RE: Expansive Soils List dik (Structural) 16 May 17 22:17 The Bentonite and Montmorillonite (sp?) clays are expansive. We have a highly plastic clay in the Manitoba-Saskatchewan area, but, other than it being lacustrine I don't know what the composition is. Expansive clays have charged surfaces and water being a polar molecule readily bonds to the surface area of the clay 'platlets' increasing its volume. Clay particles are very small and are flat and thin (maybe only a few angstrom units thick). There may be other materials/clays that are expansive, but, those are the ones I'm familiar with. One of the geotechs may be able to fill you in a little better. Dik RE: Expansive Soils List oldestguy (Geotechnical) 16 May 17 22:49 dik has a good start. However, I'd do a Google search for "Expansive soil classification". There are several soil classification standards and each generally has test data limits indicating degree of expandability. Depending on you use, perhaps one of these classification methods will apply. A little more looking into the subject with the search for "drilling mud" might help also. RE: Expansive Soils List Doctormo (Geotechnical) 18 May 17 20:33 Almost any clay west of the Mississippi River in the US is a potential expansive issue although they can occur about anywhere. Only way to know is to test soil and/or local experience. Very hard to determine expansive properties by visual observation.