Bricks and mixers

[Shannon C. Dealy]

On Sun, 24 Nov 1996, Eric D. Hart wrote:

> Had a few, perhaps heretical, questions.
> 
> 1.  Can you make cob bricks?  I was thinking that it would be easier than
> building the wall on site, a foot or two at a time.  Thought it would make
> more sense for the raised bed idea that I am working on.  Might be able to
> get some people making cob bricks in their basements during the winter so we
> will be ready in the spring.  Although, we would have to act quickly to get
> the dirt out of the ground before it freezes!!

Yes you can, cob is simply one form of adobe.  One way to think of the
difference between cob and adobe is that with adobe you generally make
bricks and mortar them together to create your building, with cob you only
make one brick and it's in the shape of a building :-)  The primary
advantage of making your structure as one large brick is that it will be
stronger.  In the case of a raised bed, I don't think that strength will
be a major concern.  The biggest concern that I see would be that you will
need to mortar them together with a cement based mortar.  Cob is not a
good mortar mix for binding materials together, though it is good for
filling in holes.

> 
> 2.  What about mixing cob in a cement mixer??  I've mixed stucoo by hand in
> a wheel barrow and in a cement mixer and the mixer was much easier!!  I know
> part of the appeal of cob is mixing with you feet but I'm just trying to
> make it easier.  
> 

You can mix the earth and water ingredients with a cement mixer, but once
you start adding straw, I hear that the mix becomes to thick/solid to work
in a mixer, so you will still need to work the straw in with your feet.


Shannon Dealy
dealy at deatech.com