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Re: Portland Cement, Earth Friendly or Not??




In article <MOD$971006.24743@rec.gardens.ecosystems>, Dave Snyder
<skarkrow@sunlink.net> wrote:

> Hi
>     I need help.  I need to know if Portland Cement would be considered
> natural.  I am using it in a project which is supposed to be Earth
> Friendly and all natural and the question has been raised whether it
> is truly earth friendly or not.  I think it is because I think it has
> limestone and clay in the ingredients.  But I don't know for sure.  If
> anyone has the answer, please cc answers to me.  

You are right about the raw ingredients for cement. In essence, limestone
and clay are cooked (burned?) in order to produce the powder. I think one
would have to be very strictly 'organic' in mindset to reject
cement/concrete as being non "Earth friendly" *in and of itself*. In
essence, concrete (what you get when you mix the cement, sand [& sometimes
gravel]) and water is a sort  of artificial rock. It weathers much as does
natural rock, and is in this way quite 'natural'. AFAIK, there are no
harmful breakdown products in ordinary concrete.

OTOH, if you consider the process of producing this product, you may have a
different opinion of the environmental impact. The raw materials are
extracted by large scale mining, and the energy for cooking them is usually
from fossil fuels--also acquired by large-scale mining, and which must be
burned (with all the associated problems associate with that) in order to
provide the heat. Then, the final product is shipped (more energy used) to
the final destination. While many of us have no problem with that, one can
easily see that some people might consider that to be excessive.

The whole question may boil down to what your alternatives might be. If
your construction can be accomplished by use of local materials, you avoid
all the environmental and transportational 'costs' mentioned above, but you
incur a different set of costs associated with the local materials. You
might want to compare the costs [environmental, as well as econmic] of
concrete with the cost of local materials. The result of the comparison
will differ from case to case, of course. These costs include not only the
damage of extraction and transportation, but also the cost of maintaining
the structure.

Well-made concrete can last for a long time. [The Pantheon for example, is
made of top-notch concrete and still stands after 2000 years.] Poorly-made
concrete can break down in a few decades. If your alternative is wood, then
you must know that it breaks down more quickly than concrete (depending on
climate, quality of concrete/type of wood, maintenance), and may have to be
replaced several times. Stone- or brick- work can be long-lasting, but may
require a lot of maintenance, and each has its own costs in terms of
extracting the material from the environment. If a concrete structure lasts
say, 200 years, but a wooden structure must be replaced every 25 years, you
must multiply the cost of the wood by a factor of 8 to make the correct
comparison.

You have to consider the various costs, benefits and problems associated
with each option. You must also consider what you are trying to do: is it
to be short-lived or long-lasting?

I have given you no answer here. You must weigh the alternatives and come
up with your own answer.

Regards,
Bill

-- 
Bill Morgan
wtmorgan@pilot.msu.edu
Center for Room Temperature Confusion

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