[Cob] lime-clay- pozzolans : was: cob raised beds

[Charmaine Taylor-dirtcheapbuilder]

Yun Que wrote:

>    Cat here,  what is the burnt clay you speak of?  What does it do for
>    the morter and could crushed clay bricks be used?
>    for the good of all C.
>

Yes crushed bricks/dust can be used as long as the bricks were kiln fired.
It is the chemistry of the firing that makes the clay pozzolanic.  You can
also use rice hull ash as an additive ( but finding it is not easy, no
commercial businesses  of RHA for natural building exisit in the US, and
indeed getting it to happen in India where they tried was a failure too)

a brick yard or local supplier may let you take the dust from loads of
brick,  crushting them yourself is  too much human energy to get a pozzolan.



And yes mixing bits of broken kiln fired bricks in with a lime mix with make
it stronger, but  not evenely so throughout...however,using what you have
available  is also a good thing.

Most really sticky clays will give a pozzolanic raction  ( mild) with lime
added.

Ms. Charmaine  Taylor/ Taylor Publishing
http://www.dirtcheapbuilder.com
http://dirtcheapbuilder.blogspot.com/   <resources for building/lime
plasters
PO Box 375, Cutten CA 95534
707-441-1632