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[Cob] Fwd: cob shake test infodhowell at pickensprogressonline.com dhowell at pickensprogressonline.comSun May 20 12:34:27 CDT 2012
Begin forwarded message: > From: "dhowell at pickensprogressonline.com" > <dhowell at pickensprogressonline.com> > Date: May 20, 2012 1:33:32 PM EDT > To: Henry Raduazo <raduazo at cox.net> > Subject: Re: [Cob] cob shake test info > > Ed, > That is my primary concern also. I think it's common knowledge > that dirt leaches out iron. One thing I think is suspicious is that > bamboo has been tested to out perform steel rebar and it's a > fraction of the weight, yet there's never a mention of that. I > think bamboo dowels in cob walls (just laid across the wall and > cobbed around) would have the same function as steel rebar and > probably would keep the integrity of the wall. > It's a good time for proposing such a thing because there is > almost no new construction and the inspectors may be more willing > to take the time to learn about cob just to have something to do. I > just can't scare the daylights out of them by proposing an American > style cob house. Although they look cool and are sufficient, they > look like a nightmare to an inspector that looks at straight lines > and 90 degree angles in homes all day. > Damon > > On May 18, 2012, at 9:41 PM, Henry Raduazo wrote: > >> Damon: >> You are of course absolutely right, and cob is vastly superior to >> adobe. That does not make it easy to get approval. Usually to get >> approval there is such a huge safety margin that the net effect is >> to be almost prohibitive to natural building. >> People doing rammed earth structures used to put a little >> concrete in their mix just to make the inspectors feel happy. >> There was so little concrete in the mix and so much time between >> mixing and pouring the mix into the form that there was no >> strength imparted to the mix, but making inspectors feel good is >> important. >> I have done it both ways. I had one project where the inspector >> required me go go in and get special approval for a wall, and my >> other projects have been the "Don't ask don't tell" format. I >> have a huge respect for people like David Eisenberg who have >> devoted their lives to trying to get reasonable building codes >> that include natural building materials. >> I have been through the whole college routine too with strength >> of materials and concrete design... I understand how engineers >> think, and I wish I had an answer to this problem other than just >> doing it under the table. I think the adobe got approved just >> because the prior situation was intellectually embarrassing. >> Native people could not build and finance traditional structures >> in their homeland, but they were allowed to build and finance >> structures built with imported materials and technology foreign to >> their native culture and traditions. >> >> I wonder: if we took apart some of the 1000 year old Pueblo >> structures and randomly tested some of the 1000 year old bricks, >> do you suppose that these bricks would pass current Adobe code? I >> don't think current adobe code has anything to do with a realistic >> assessment of what is required for a structure to last 1000 years. >> The strength that a wall has the day it is manufactured and the >> strength it has 100 or 1000 years from now depends on the chemical >> and mechanical stability of the materials. That is why putting >> steel in cob or adobe bothers me. It is not chemically stable and >> it expands as it reacts with moisture or minerals in the wall >> material. Think about all the possible impurities in clay soil. >> >> I wish Good Luck to the Alpha Testers, >> >> Ed >> >> >> >> On May 17, 2012, at 2:52 PM, dhowell at pickensprogressonline.com wrote: >> >>> Ed, >>> Understood about quality control. I must point out concrete >>> mixes from scratch in a wheelbarrow can also have vastly >>> different strengths according to the amount of water used. Adobe >>> bricks? New Mexico Earthen Building Materials code states, "each >>> of the tests prescribed in this section shall be applied to >>> sample units selected at random at a ratio of five units per >>> twenty-five thousand bricks to be used or at the discretion of >>> the building official." Five out of 25,000 seems like a pretty >>> unrepresentative number for the whole. Quality control can be >>> done by performing tests at the foundation, sill height, and >>> lintel height of the walls. Did you know the adobe code allows a >>> psi of 250 and one out of five can have a psi less than that? >>> We're talking about the same material just a different building >>> procedure. Their code is a good guideline, but some things are >>> questionable, such as it requires concrete stucco which is an >>> accident waiting to happen according to the Devon Earth Building >>> Association. A healthy topic that must be discussed, don't you >>> think? >>> Damon >>> >>> On May 17, 2012, at 2:09 PM, Henry Raduazo wrote: >>> >>>> The problem might be one of quality control. When you are >>>> mixing something in a large batching machine (like a concrete >>>> mixer) you have large 3-5 yard batches which are perfectly >>>> uniform. When you have small crews making 1/27th of a yard >>>> batches on a tarp asserting quality control is a nightmare. >>>> Every crew can not make every batch the same let alone getting >>>> the 5 or 6 different crews to make uniform batches. >>>> I have been able to make uniform cob batches by mixing one ton >>>> batches on a concrete slab with a rototiller. That might satisfy >>>> a quality control person, but getting such anal persons to >>>> accept hundreds of batches made by half a dozen different crews >>>> might be expecting too much even if we had a code that described >>>> the material in a way to differentiate acceptable cob from >>>> unacceptable cob. >>>> >>>> Ed >>>> On May 17, 2012, at 11:29 AM, dhowell at pickensprogressonline.com >>>> wrote: >>>> >>>>> Thanks Ron, >>>>> As I mentioned; "but no paperwork which building officials >>>>> will accept." >>>>> >>>>> >>>>> On May 16, 2012, at 8:17 PM, Henry Raduazo wrote: >>>>> >>>>>>> but no paperwork which building officials will accept. >>>>> >>>> >>> >> >
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