[Cob] cob shake test info

[Henry Raduazo]

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.
>>> 
>> 
>