Cob-Wood and experiments

[Bob Bolles]

The combination of clay and other materials  falls into the category of
*light clay*
The clay/sand/dirt mix ie in block form is Adobe, in a monolithic form
(created by lumps of clay mix) is cob.
As a straight mix, it would be *heavy clay*, having some weight/density per
unit.
Adding other *lighter* material has the advantage of reducing the weight
(easier to work with), increases the insulative value (reducing thermal
conductivity), and in some cases, helps hold the mix together; straw may be
the best for that, chips somewhat less, sawdust very little.

We have experimented with a variety of materials - the outfall from a
chipper, recycled Styrofoam, sawdust, vermiculite etc, with varying results
- At the heart of the issue is what is available and works best in your
location and for your application.  Much of the success/failure depends on
the type of clay available in your locality - results vairy greatly.

The light clay material works well when packed into forms to make blocks,
used cob-like for a monolithic assembly, or a plaster (the more course the
material mix, the less handy as plaster).  Forms tend to slow the drying
process.

In areas where seismic loading is an issue, I would guess that internal
form-work like that used for rammed-earth would appropriate.  I am told
that adobe can now be permitted in seismic areas, but I am not familiar
with the structural requirements - perhaps someone can shed some light on
that.

As I posted earlier, I am concerned about how the Portland Cement actually
reacts in the papercrete mix, re excess water and draining time, but I
would tend to believe that a clay component vs the PC might yield good
results.  I would be very interested in hearing anyones experiences on that
subject.

I have had excellent results with clay mixes as a mortar.
We have even used a clay mortar between straw bales (not so thick as to
interfere with the thermal characteristics) with excellent results.

Regards
Bob


> HI Rog...yes I made a few bricks and they are still drying..made some
with
> just clay/chips....my concern is what would you mortar with?
> 
> I am not sure I like this stuff for bricks...may be too weak in EQ
country
> for movement..monolithic 'feels' safer to me, ie poured wall and bricks
are
> so dang much trouble>> make, dry, turn out, tuner over,  pick up, break
> fingernails,  mortar, level, repeat x 9,004 or so....:>
> 
> The  bricks are a bit heavier than the FC ones, but I can still manage
them OK