Cob: Re: Bentonite

[Matthew HALL(SED)]

I have read about the potential for bentonite in earth walls in Houben & Guillaud's book, but i
have never seen any examples. Does anybody else know of any?

I know that bentonite is about 70% montmorillonite which swells massively on contact with water;
very undesirable in sub-soils from a building point of view. Still, if you were to add it to an
earth wall (made of suitable soil) i suppose it could have the effect of swelling inside the pore
spaces and to some degree prevent water penetration. i would imagine that this is rather difficult
to acheive, has anybody seen/tried this on a load-bearing earth wall?

For those who have used bentonite to stabilise a soil - how does it perform in frosty conditions?
If it retains a lot of water then i can see problems with frost damage in an earth wall.

Finally, how much does it cost to buy and is it easily available?

Regards
Matthew

____________________________________________________________________
Matthew Hall BSc (Hons) GradBEng
Centre for the Built Environment
Unit 9 Science Park
Sheffield Hallam University
Pond Street
Sheffield S1 1WB
England

Tel: +44 (0) 114 225 3200
Fax: +44 (0) 114 225 3206
E-mail: M.Hall at shu.ac.uk
Webpage: http://www.shu.ac.uk/schools/sed/earth