Cob: earth versus concrete in poorer counties

[Robert Bolman]

Hello,
I just responded to the following inquirery for someone and though I might
as well share it with the list.
Feedback?
Rob


>So I guess what all this boils down to are two major questions;
>1)What are the implications (environmental, health etc.) of adding cement
as a
>component of your mix to earthen based materials?
>2) What are the implications of using cement in general?


Portland Cement, typically mixed with sand & gravel to create what we call
"concrete", in & of itself is not a problem from a standpoint of toxicity.
The exception to this would be unscrupulous manufacturers that burn toxic
waste to fuel the manufacturing process & put the ash in the portland cement
as a convenient way to dispose of it.
The big envronmental problem WRT cement is that it is very energy intensive
to produce & distribute and that it is used in vast quantities around the
world (over 6 billion tons annually).  For this reason, it accounts for 4-5
percent of the world's greenhouse gases.  So in & of itself concrete is a
major problem.
As far as an additive to earthen construction is concerned, I really don't
see the point.  Every time there is an earthquake in Turkey or Egypt or
somewhere, we hear of high fatalities resulting from poorly built CONCRETE
housing falling in on its occupants.  The same criticism could certainly be
made of much of the unstabilized earthen housing in poorer countries, but,
all other things being equal,  I don't see where it's going to change much
by "stabilizing" that housing.
More important would be to apply known engineering principals to the housing
in poorer countries.  It's tough though.  The "leaders" in those countries
are struggling with budget shortfalls & corruption on one hand and a
population demanding "western style" housing on the other.  I can fully
understand how they can be pressured to allow unsafe housing to be built.
In the best of all worlds, I suppose I'd like to see people living in
UNSTABILIZED earthen housing that is designed realistically and
thoughtfully.  It wouldn't  be highrises.  It would be 2-3 stories, but with
a great enough density and mixed-use design that people could walk to many
places.  Urban farming, permaculture & appropriate technology would further
reduce the need to go places.  The housing would be beautiful with thick
curving walls that would be less likely to topple in an earthquake.  Smaller
rooms would be well designed enough to function nicely and help make the
housing earthquake resistant.
I suppose I could go on & on.  If you'd like me to elaborate or clarify,
please let me know.  You could also call me at 541-344-7196.
Best wishes,
Rob