[Cob] high clay-

[Kristen Davenport]

I'd be interested in hearing people's experience with really high levels of 
clay, like 90 percent, with the remaining 10 percent as sand/gravel. We're 
building a round structure with a mix like this right now and although there 
are plenty of teensy spider cracks, I certainly am not seeing an shrinkage 
away from stuff (like rocks or wood) in the cob....

Kristen

----- Original Message ----- 
From: "Shannon Dealy" <dealy at deatech.com>
To: <yewberry at wavecable.com>
Cc: <coblist at deatech.com>
Sent: Tuesday, July 28, 2009 6:27 PM
Subject: Re: [Cob] Soil Survey


> On Tue, 28 Jul 2009, yewberry at wavecable.com wrote:
>
> [snip]
>> A high percentage of silt (I'm pretty sure 30% constitutes "high") will 
>> greatly weaken your cob mixture.  I don't know of any real way to remove 
>> silt from a large amount of soil.  Better to find another source, I'm 
>> guessin'.
> [snip]
>
> There is no substitute for actually testing the mix.  The soil at my place 
> works just fine for cob even though the silt is around 35%.  While silt 
> does interfere with the bonding of clay, lots of clay or lesser amounts of 
> very sticky clay may make up for it.
>
> Shannon C. Dealy      |               DeaTech Research Inc.
> dealy at deatech.com     |          - Custom Software Development -
> Phone: (800) 467-5820 |          - Natural Building Instruction -
>    or: (541) 929-4089 |                  www.deatech.com
>
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