Cob: Origins of Cement vs Cob

[John Schinnerer]

Aloha,

-----Original Message-----
From: SANCO Enterprises <Paul & Mary Salas>
>What you described in your test example does not correlate to
>any ASTM test method for the material. Compression, modulus of rupture
>and absorption are accepted test standards and should be utilized if one
>is going to compare similarities or differences between materials.

...and neither the "homebrew" tests described nor the comparable ASTM tests
deal with the materials as actually used in a completed structure.  Bits and
sheets and bricks and blocks of small sizes are not a cob house, nor is a
cob house made of these bits but rather of a relatively monolithic mass of
cob shaped in ways that have a lot to do with the viability (or not) of the
building.  

A lot of these tests are designed for, and only relevant to, linear and
sheet materials used in stick-frame-with-sheathing construction, and
therefore (IMO, obviously) not all that relevant for cob.  Some may be
passed by cob, which may or may not indicate that cob "works;" some may not
be passed, which will be taken as a failure of cob in testing-land but again
may not indicate actual failure in an actual building.

So, if we're going to work for codes and whatnot, I suggest we work for
relevant testing of cob as actually used in actual structures, not abstract
testing of bits and pieces to satisfy some existing test methodology for
materials used in quite different ways. 

>I understand your concern about opinions being repeated so often that
>they take on the appearance of fact...

...and the supposed validity of ASTM tests for cob structures seems to be an
example of this happening.

John Schinnerer