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Fwd: Re: [Cob] Difference between cob and rammed earth (reinforcing)Ian Marcuse dtebb at alternatives.com
Fri Dec 10 20:43:12 PST 2004
Reinforcing cob in earthquake zones is probably a good idea. Bamboo would work fine I think, embedded vertically would help to prevent shear failure. In our recent earthquake tests at UBC this year, the need for this type of reinforcment was quite clear. Mind you at a 7.2 richter quake the cob held up briliantly without reinforcement, apart from straw. At a >9 richter, the building seriously failed, but without roof collapse. A 9 quake is however extremely rare. If you have bamboo, I doubt that it would hurt. Does anybody have other thoughts on this? We hope to post a video of the quake test on the web soon Ian Marcuse > > >In response to Layth, > >The response is not that cob "can't" be reinforced with rebar, it's >that it doesn't need to be! > >Cob is a equivalent to adobe in consistency: clay and sand are >combined with water and straw. The cob mix is then sculpted by hand >into a monolithic structure (unlike typical adobe construction where >dried bricks are mortared together with clay slip). Since the straw >fibers in cob run through the structure, no rebar or other extra >reinforcement is needed. Adding rebar would just increase costs, >plus moving away from the beauty and simplicity of building with >completely natural materials. A testament to structural integrity, >there are Medieval cob buildings, standing safe & sound to this day! >Cob is also called sculpted, poured or puddled adobe. > >"Rammed earth", as I've understood it to be, consists of a mixture >of soil and portland cement, lightly wetted, then rammed in between >plywood forms. Since the mix contains no straw, rebar is required >for structural integrity. I think rammed earth isn't an accurate >name; actually this should be called "Rammed Cement-Soil" when >portland is added. Rammed Cement-Soil turns out to be a rather >toxic and industrialized material. Have you ever had cement burn a >hole in your skin? Not fun! > >I hope this helps. There are many good books on cob, the best I've >seen is the "Hand Sculpted House" by Ianto, Michael and Linda of Cob >Cottage Company... > >(Note to Shannon - How's the description of cob on the cob website? >Is it detailed enough to direct inquiries like this to the site?) > >Ocean > >Intaba's Restaurant, Corvallis, Oregon >http://www.intabas.com > >Ahimsa Sanctuary for Peacemaking and Sustainable Living, Philomath, Oregon >http://www.peacemaking.org > > >On Dec 10, 2004, at 1:39 PM, laythss at yahoo.com wrote: > >>Hello all again, >> I would like to know the reasons (or possible reasons) why Rammed >>earth can be reinforced with re-bar whereas cob cannot. >> >>Any help is appreciated. >> >>Layth >> >> >>_______________________________________________ >>Coblist mailing list >>Coblist at deatech.com >>http://www.deatech.com/mailman/listinfo/coblist >> > > >_______________________________________________ >Coblist mailing list >Coblist at deatech.com >http://www.deatech.com/mailman/listinfo/coblist
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