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Re: GSBN:Cemento (combined responses)

What are some examples of using less Portland cement to do the same
job?  Adding fly ash has been mentioned.  Rob Tom advocated the
development of an inside out insulated concrete form, where the
concrete skins would be on the outside, and the foam in the middle.
Rene and maybe Lars talked about using a small amount of cement, to
cement seashells together, with lots of air gaps.  Living near
volcanoes, pumice-crete uses the same idea, with a little cement and a
lot of pumice.  A cement grade beam on a rubble trench saves a lot of
concrete, with potentially superior performance.  Each of these
approaches can save many tons of cement, while using local, low
embodied energy materials such as seashells, rock or pumice.

Other examples and techniques?


--On Wednesday, July 4, 2007 9:39 PM -0400 John Straube
jfstraub@... wrote:

I also think one has to consider that cement is just one material
that is used. It is used an awful lot, and this is part of its
environmental footprint. However, the reason it is used a lot is that
it is made of clay and limestone (available most places in quantity)
and results in a very durable and low dollar cost product. I am all
for reducing cement use, and changing cement manafucturing to
dramatically reduce CO2 and other emissions. however, if the
replacement for the apartment buildings in China is, for example,
steel, then the CO2 emissions will rise dramatically as steel will
use more energy and CO2 for the same beam or column. Lots of cement
is used in heavy civil works like roads, and sewers, curbs and
sidewalks. There are some replacements, but few work as well.
At the end of the day, I think cement is one of many materials that
we need to use more wisely and hence less of, but for many purposes,
it is hard to find an equally durable, non-combustible material that
has less impact.
One of the clear substitutions is wood framed housing instead of
concrete. This works in some places, like where they have trees, but
there are limits to height, fire resistance, and durability that are
quite practical. For most other applications, like basements,bridges,
sewer pipes etc, I think we can gain more by be smarter in its use
(optimally designed structures) and dramatically improve is
production (e.g. there is little reason why a coal-fired cement plant
could not use carbon sequestration.

Graeme North wrote:
Thanks Mark ?

It looks as though the 6-10% figure so often quoted in green
architecture circles for cement manufacturing?s CO2 contribution may
be partially right- and wrong.

But see a graph at

<a  target="_blank" href="http://cdiac.esd.ornl.gov/trends/emis/glo.htm";>http://cdiac.esd.ornl.gov/trends/emis/glo.htm</a>

This was in one of the references Mark so kindly put out.  It puts
cement manufacturing contribution at somewhere around  2-3 %  annual
global CO2 emissions

So although cement is one of the major players in the world?s
pollution, and certainly in the construction industry?s
contribution, it looks to me that although its present contribution
may now be nearer 2-3 % of overall annual global CO2 emissions, its
cumulative total effect of all human generated CO2 appears to be
nearer 8% ?  does this look right to anybody else?

Graeme North Architects,
49 Matthew Road,
RD1, Warkworth,
New Zealand 0981
Ph/fax +64 (0)9  4259305


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