Cob: Concrete, reduce, reuse, eliminate!

[louis at pcmagic.net]

>> crtaylor wrote:
>> >
>> Lumber, adobe mixes, sand, gravel - all of these building materials
>> nearly always have to be harvested/mined from SOMEWHERE, and trucked to
>> where ever you are using them.  Concrete's no worse, IMO.  In fact, from
>> the standpoint of longevity of the building, a concrete building that
>> lasts virtually forever actually could be said to leave a smaller
>> footprint on the earth's ecology - as opposed to the current fad for
>> stick-frame buildings that are often decrepit and require extensive
>> repairs in 20 or 30 years, and are usually a lost cause in less than 50.
>
>Unfortunately, concrete lasting forever hasn't been invented yet.  Concrete
>in the present form we know it was inverted just after WW2 and our landfills
>contain many mega tons of the stuff.  The earlier forms of it were even less
>durable.  One of the longest lasting example is the great pyramids, where
>the mixture used was more of a mineral and boiled cactus (as a binder)
>content.  From several of the weekend workshops I attended, we learned that
>environmental load of concrete is something on the order of a thousand
>years.  We have barely covered fifty years of concrete in its present form
>for foundations and it seems to be doing only slightly better than limestone
>(fortunately concrete is easier to apply water proofing to, which wouldn't
>be as necessary had builders been competent is designing in French drains
>automatically from the beginning -- which helps limestone foundations
>immensely too).  

So which is it?--does concrete last too long or not long enough?

If you're going to compare it to lime, you're talking about a matter of
degrees of undesireability.  They've both got embodied energy, it just that
cement is roughly 60% more.  Lime is weaker--for foundations.  On walls it
requires regular maintenance => more embodied energy.

An environmental load of one thousand years?  That's pure goobledegook.
Concrete is essentially inert, doesn't leach or poison anything.


>There is ANOTHER reason for severely limiting our use of concrete.  While
>many, many groups and organizations try to seal out and positively ventilate
>around, RADON gas is in many cases is actually produced by radioactive decay
>of the rock inside the concrete itself.  Since concrete is actually a very
>porous material, it is nearly impossible to eliminate it from seeping out
>radon gas.  As a Band-Aid fix in my twenty year old stickbuilt ranch house
>(that soon some other poor smuck will own as we start to build our cob/SB
>home), we have to run an air-to-air heat ventilator to exhaust the radon
>build up.  Many thousands of homes have this problem, especially "tight"
>homes.  A cob (and SB home with lots of added thermal mass) home doesn't
>need to be tight and this helps reduce any radon buildup potential quite a
>bit.

This is a red herring.  Radon can come out of any soil or aggregate.
Individual rocks can be radioactive.  I remember reading a white paper on
the web somewhere [sorry I don't know where it was right now] which
addressed this issue.  It said there can be radon generated in the
aggregate, but for all practical purposes it is _locked up_.  Radon gas has
got to become concentraded to become a problem, and it can't do that when
it's locked up in the concrete.   OTOH, some rocks are radioactive all by
themselves.


>From the EPA website:

MYTH: Radon affects only certain types of homes.
FACT: Radon can be a problem in all types of homes such as old homes, new
homes, drafty homes, insulated homes, homes with basements and homes
without basements. Construction materials and the way the home has been
built may also affect radon levels.

Radon Has Been Found In Homes All Over the U.S.
Radon is a radioactive gas that has been found in homes all over the U.S.
It comes from the natural breakdown of uranium in soil, rock and water and
gets into the air you breathe. Radon typically moves up through the ground
to the air above and into your home through cracks and other holes in the
foundation. Your home can trap radon inside. Sometimes radon enters the
home through well water (see Section 6 for more information about radon in
water.)

Any home can have a radon problem. This means new and old homes,
well-sealed and drafty homes, and homes with or without basements. In fact,
you and your family are most likely to get your greatest radiation exposure
at home. That is where you spend most of your time.

Nearly 1 out of every 15 homes in the U.S. is estimated to have elevated
radon levels. Elevated levels of radon gas have been found in homes in your
state. Contact your state radon office for information about radon in your
area.

___end quote_____

So going with a drafty cob or strawbale house won't help.


>And the final thing I'd like to say about concrete really makes me sick.
>You've heard about companies dumping their toxic leftovers into commercial
>fossil fuel based fertilizers as fillers?  Yeah, they do that because the
>leftovers are almost impossible to dispose of safely and cost effectively.
>Well, we learned at a recent hands-on workshop that companies have been
>doing this to concrete for many. many years and not telling us.  There is a
>certain percentage of fill and contaminants that are allowed and your local
>concrete operator may not even be aware of it because they are chiefly
>concerned with baking their cakes and getting them to market as soon as they
>can.  This is very sickening and is typical of what happens when the
>consumer is not baby sitting every step of every process where greed and
>profit are the main determiners of business.  No wonder why childhood
>cancers and diseases seem to linger on through the generations.

You're rather vague, what contaminants are you talking about?  If you're
talking about fly ash, that is _generally_ seen as a good thing, ie making
use of a by-product.

Rants are okay, just try to keep them rational.

---Louis