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Kiko Denzer on Art


Cob: Re: cob, pise

Yun Que yunk88 at hotmail.com
Fri Jan 31 21:53:39 CST 2003 

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<P>Cat here, In that little book that is still out on loan it showed a tamping method that was rather simple.  It was a few hardy souls and a good sized chunk of tree trunk.  I can't remember what was used as the handles but the stones for the foundations were pounded into the ground this way and no other foundation was needed.  They did not dig a hole first!  The house was then set on these piers.  Thinking I may do my floor this way, but it may work for rammed earth if the forms are well buttressed.  </P>
<P><EM>for the good of all </EM>Cat<BR><BR></P></DIV></DIV>
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<DIV></DIV>>From: "SANCO Enterprises, LLC" <CHANSEY at EARTHLINK.NET>
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<DIV></DIV>>Reply-To: "SANCO Enterprises, LLC" <CHANSEY at EARTHLINK.NET>
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<DIV></DIV>>To: "Jill hotmail" <WRITEJILL at HOTMAIL.COM>,"cob list" <COBLIST at DEATECH.COM>
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<DIV></DIV>>Subject: Cob: Re: cob, pise 
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<DIV></DIV>>Date: Fri, 31 Jan 2003 19:38:35 -0700 
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<DIV></DIV>>Jill inquired, <LET straight this have I if see me>
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<DIV></DIV>>Jill made a serious inquiry about the different methods of construction and I will attempt to clear up a few things. I realize that those of us who have been around for a while take things too lightly--and if I have I apologize. 
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<DIV></DIV>>Let's start with some basics. All earthen compositions regardless of the terminology must accomplish one thing ---provide a strong building component. If you look at the material ratios of clay, soil, sand or aggregate for cob, adobe or rammed earth, they are all essentially the same when used in their natural state. 
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<DIV></DIV>>Straw is an added component that that has to be used appropriately. When used in cob or in more humid climates, the permeability of the structure in improved through the use of straw--it breathes better. In less humid areas where rain fall is not a factor, you can do without the straw. In many areas where there is not a sufficient amount of non-clay material, straw, grass or other organic materials will be used to minimize cracking and provide for a monolithic unit. 
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<DIV></DIV>>Pise and Rammeed Earth 
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<DIV></DIV>>NO-EQUIPMENT: if this is the approach one is going to take, the forms can be simple. Hand tamps do not provide the same amount of impact force as pneumatic equipment, therefore the lifts must be in the 2 or 3 inch range. Any more than that, you will have weak or void areas when the forms are pulled. The moisture content is critical and should be optimum based on the materials being used. With hand tamps you will be fortunate if you achieve 90% compaction. This would be identical to the material mix for CEB's (compressed earth blocks) made by machine. Pozzolan based materials or cement may be added to the base material to add strength. This is a matter of choice. If enough cement is used, you will not need a render or plaster. 
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<DIV></DIV>>Machinery and equipment for Pise and Rammed Earth 
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<DIV></DIV>>Tampers (powder-puff), usually about 6" in diameter is used to tamp the material. It is similar to a pogo-stick with a plate of steel at the end and is run by compressed air. Bobcats, tractors and conveyors are often used to deposit material into the forms. Here the lifts can be 6" deep as the tamper is capable of achieving 100% compaction. Over-compacting can blow-out a form. Cement is optional and will achieve the same results as above. 
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<DIV></DIV>>Easton's Method for PISE 
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<DIV></DIV>>This is not rammed earth or Pise--it is concrete, be it a weak mix, that is applied. It is no different than the methods used for guniting a swimming pool, lining a mine shaft or stabilizing a hillside. It is the same equipment and process used for ferro-cement applications. You can not achieve consolidation and compaction of soil and optimum moisture simply by blowing or guniting the material---it will fall apart. Eaton's use of a high cement content is what makes his process work. I works and is successful--but expensive. 
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<DIV></DIV>>All earthen construction has limits as to how high you can build. The aspect ratio is the limiting factor. This is another topic onto its own. 
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<DIV></DIV>>Re-bar or reinforcing steel will work only if can be encapsulated to utilize its properties. It has very little beneficial use in cob, adobe or CEB construction. When used in a rammed earth or a-la-Easton process, you enrich the material around the re-bar with cement to create a beam or column. 
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<DIV></DIV>>Hope this has helped a wee bit. 
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<DIV></DIV>>SANCO Enterprises, LLC 
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<DIV></DIV>>Paul Salas, General Manager 
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<DIV></DIV>>P.O. Box 45741 
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<DIV></DIV>>Rio Rancho, NM 87174 
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<DIV></DIV>>(505) 238-1485 
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<DIV></DIV>>chansey at earthlink.net 
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