Berkeley Cob Project

[Paul & Mary Salas]

Otherfish at aol.com wrote:

sniped
> are you going to make so you can pump to the wall?

That is affirmative----I will be shooting it like gunite.

I have not tried " COB" in its true sense. Does anyone on the list have
data as to the actual time in days/weeks it takes per inch of material
to dry?  In discussion with Paul G. McHenry (author of several books on
building with earth), and verified through my own experiments with thick
mass structures, it takes about a week per inch of material for it to
fully cure and attain at least 300 PSI.  It's slightly less for rammed
earth.  How about the E-shippers and rammed tires--any drying time data?

I will be working on reducing the moisture content and utilizing natural
pozzolanic material to achieve a more rapid set as well as a higher PSI
value as a remediation measure to the above.  The addition of cement or
similar high energy material for the core portion of the wall is a waste
of time and money.  Excellent results can be achieved by adjusting the
mix design to maintain a uniform clay content.  Fully stabilized
material is generally only required for the first 2 feet above grade and
then the entire surface covered with the dreaded "STUCCO".  I have been
working on a earth render that is only 1/2" thick and basically
waterproof (less than 2% moisture absorption @ 8 days).  When the
process is fully developed, this will be a major leap forward for all
the cobbers, adoberos and even straw-bale folks who need an inexpensive
impermeable exterior coating.  The per SQ FT price will be about half
the cost of stucco and can be applied with a $60 hopper gun from Home
Depot.  A trusted sole who posts to this list has some of the material
and will hopefully have some time to experiment and report the findings.

The machine I am building will convey the material with very low
moisture content and by controlling hydration and impacting the material
pneumatically, the result will be a combination of cob-adobe and rammed
earth all in one package.  Still need to introduce an insulation media
into the equation to complement the thermal mass. Working on several
alternatives.



Paul Salas
SANCO Enterprises
Albuq., N.M.