Cob: Re:Test Bricks | online book...

[Michael Blaha]

Kim, 

Here is a link to Becky Bee's Book online where she talks about mixes- maybe it will help. 

http://www.weblife.org/cob/cob_043.html

m i c h a e l 


 
 Kim West wrote:
>I am new here [and new to cob] and do not know what all subjects have been covered, but my interest has been piqued by the recent posts concerning the mixture to use in making cob.
>
>After doing some tests on the soil on my property I found that it was anywhere from 80-95% sand, according to where I collected the sample, with the remainder being silt. There was no clay mixed in with the soil, but if I dug down anywhere from 6 inches to 1 foot I found solid red clay.
>
>I made some test bricks using the soil and the red clay in three different ratios and found that 25% clay and 75% soil was a bad mixture and the bricks made from it crumbled easily.
>
>The two other ratios that I tried were 50/50 clay/soil and 75/25 clay/soil. 
>
>The 50/50 did not crack in the drop test until 3 feet above the ground, and it broke at 5 feet above the ground. 
>
>The 75/25 cracked at 5 feet above the ground and broke at 7 feet above the ground.
>
>With what little I know it seems that the 75/50 ratio is the best and should be used in any cob that I make from my land, but reading here and on other sites it seems that 75% clay is too high.
>
>Am I missing something here? Would someone please fill me in on whether or not I should use the 75/25 clay/soil mixture. It would seem to me that I should since it passed the drop test so well, but looks can sometimes be deceiving and I would like to know if I am missing something.
>
>Thanks,
>
>Kim
>


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