[Cob] Soil Survey

[rodger at inbox.com]

As well, it is beneficial to have SOME silt in your mix.  The silt is really just super fine sand, so it can help fill the gaps between the sand particles.  It can act much like mixed aggregate does for concrete.

However there is a point where it becomes too much, and that point depends on your clay and sand.

Do your own tests.  It's the only way to know.

Cheers:)

> -----Original Message-----
> From: dealy at deatech.com
> Sent: Tue, 28 Jul 2009 17:27:56 -0700 (PDT)
> To: yewberry at wavecable.com
> 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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