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<DIV dir=ltr align=left><SPAN class=591490714-07052010><FONT face=Arial
color=#0000ff size=2>This is indeed correct. Carbonation is the conversion of
Calcium Hydroxide to Calcium Carbonate. Calcium Hydroxide is lime, whereas in
cement it is also the product of the hydration process. none the less it absorbs
atmospheric carbon dioxide and should rightly be considered in any holistic LCA
analysis of above ground/water concrete. cement/concrete does generally
carbonate much more slowly than lime (due to its denser pore structure) and
whilst like lime carbonation is beneficial (for strength) carbonation of
concrete is seen as detrimental because of the pH reduction and subsequent loss
of passive protection for any embedded steel reinforcement. Carbonation in plain
(unreinforced concrete) is also beneficial for its strength development.
</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=591490714-07052010></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=591490714-07052010></SPAN><SPAN
class=591490714-07052010><FONT face=Arial color=#0000ff size=2>The embodied
carbon of modern blended cements and efficient kilns is getting
closer to that of hydraulic limes. We should specify lime because of its
favourable performance qualities (breathability, flexibility, aesthetics etc)
rather than because of the carbon argument. You can indeed achieve
much lower embodied materials of equivalent strength (if that's your criteria)
using blended cement binders compared to hydraulic lime (simply by using
less cement) because cement is a much stronger binder.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=591490714-07052010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=591490714-07052010><FONT face=Arial
color=#0000ff size=2> For a really low embodied CO2 render use
clay.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=591490714-07052010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=591490714-07052010><FONT face=Arial
color=#0000ff size=2>Pete</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=591490714-07052010><FONT face=Arial
color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=591490714-07052010><!-- Converted from text/plain format -->
<P><FONT size=2>Prof. Pete Walker,<BR>Director BRE Centre for Innovative
Construction Materials,<BR>Dept. Architecture & Civil
Engineering,<BR>University of Bath,<BR>Bath BA2 7AY,<BR>UK.<BR>Tel: 01225
386646<BR>Fax: 01225 386691<BR><A
href="http://www.bath.ac.uk/bre">http://www.bath.ac.uk/bre</A><BR></FONT></P></SPAN></DIV><BR>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> GSBN-bounces@greenbuilder.com
[mailto:GSBN-bounces@greenbuilder.com] <B>On Behalf Of </B>John
Straube<BR><B>Sent:</B> 07 May 2010 14:41<BR><B>To:</B> (private, with public
archives) Global Straw Building Network<BR><B>Subject:</B> Re: [GSBN] embodied
energy and sequestration<BR></FONT><BR></DIV>
<DIV></DIV>Concrete absolutely carbonates and consumes CO2.
<DIV>This is one of its problems: carbonation reduces the high initial pH of 13
and when it drops below 10 or so (some say 9, others 11!), steel within it
becomes much more susceptible to corrosion.</DIV>
<DIV>The industry has been working for years to produce very dense concrete, and
even produce CO2 blocking coatings, to reduce this problem. </DIV>
<DIV>Porous lower strength concrete can carbonate several inches in a decade,
whereas high strength, low w/c ratio, high fly ash and silica fume concrete
carbonates much much slower (at least 10 times more slowly)</DIV>
<DIV><BR></DIV>
<DIV>The CO2 released by the coal or nat gas during the firing of lime cant ever
be reabsorbed only the CO2 released by the chemical decomposition is. Portland
is likely the same.</DIV>
<DIV><BR>
<DIV>
<DIV>On 2010-05-07, at 8:19 AM, Tom Woolley wrote:</DIV><BR
class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">
<DIV
style="WORD-WRAP: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space">
<DIV>Dear all</DIV>
<DIV><BR></DIV>Maybe there is confusion here between cement and lime
<DIV><BR></DIV>
<DIV>Lime can absorb C02 during carbonation and this can make a small
contribution to carbon sequestration over its life in a building</DIV>
<DIV><BR></DIV>
<DIV>Cement however does not in most cases as cement works best if it does not
carbonate unlike lime. </DIV>
<DIV><BR></DIV>
<DIV>The argument that C02 is stored in concrete is a bogus argument put
about by the cement and concrete industry to try and greenwash cement.</DIV>
<DIV>The carbonation argument seems to be based on the idea that concrete can
be crushed at the end of life and that this has some carbonation benefit</DIV>
<DIV>See</DIV>
<DIV><A
href="http://www.sustainableconcrete.org.uk/main.asp?page=85">http://www.sustainableconcrete.org.uk/main.asp?page=85</A></DIV>
<DIV><BR></DIV>
<DIV>The C02 is emitted during the manufacture of cement and is not recovered
in my opinion . It contributes to fossil fuel energy wastage and global
warming</DIV>
<DIV>Even the use of recycled material like ash involves energy though the
cement industry have made great strides in reducing this</DIV>
<DIV><BR></DIV>
<DIV>Cement manufacture remains one of the highest emitters of C02 in all
human activity as alternatives are not being used in many parts of the
world</DIV>
<DIV><BR></DIV>
<DIV>Pragmattically we probably all use a bit of cement from time to time but
it should be avoided if there are better alternatives like lime or earth</DIV>
<DIV>Here is an interesting paper which discusses these issues and compares
cement to alternatives</DIV>
<DIV><BR></DIV>
<DIV><A
href="http://www.springerlink.com/content/56266t21424h4854/">http://www.springerlink.com/content/56266t21424h4854/</A></DIV>
<DIV><BR></DIV>
<DIV><B>Calculation of sequestration in wood straw etc.</B></DIV>
<DIV><B><BR></B></DIV>
<DIV><B>A paper on this is being prepared by David Robson of University of
Cumbria and initial findings have been presented to the UK Renewable Building
Group</B></DIV>
<DIV><B>Several GSBN UK members are part of this group</B></DIV>
<DIV><B><BR></B></DIV>
<DIV><B>This research will be made available when complete and will hopefully
provide some hard data on the sequestration contribution of renewable bio
based materials</B></DIV>
<DIV><B><BR></B></DIV>
<DIV><B>Tom</B></DIV>
<DIV><B><BR></B></DIV>
<DIV><B><BR></B>
<DIV>
<DIV>On 7 May 2010, at 04:13, Mészáros Attila wrote:</DIV><BR
class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">
<DIV>Dear All,<BR><BR>I completely agree with Derek. Though the amount of
the reabsorbed CO2<BR>could be nearly 50 % of the portland cement's dry
mass, the CO2 emission<BR>during the production is higher than this
amount.<BR>The net CO2 production of portland cement production and curing
is<BR>positive. The whole process does not sink, but produces CO2. It is
pure<BR>chemistry and physics.<BR><BR>So I am really surprised on Martin's
info on IPCC's perception.<BR>I know personaly the hungarian member of IPCC,
Diana Ürge-Vorsatz, she<BR>is also a physisist.<BR>So if we can have a bit
more info, we can act. First informal ways, and<BR>then even
formaly...<BR><BR>Attila<BR><BR>Attila Mészáros<BR>CEO, CereDom
Ltd<BR>email: <A
href="mailto:meszaros.attila@ceredom.hu">meszaros.attila@ceredom.hu</A><BR>tel:
+36 20 9772258<BR><BR>2010.05.06. 23:22 keltezéssel, Derek Roff írta:<BR>
<BLOCKQUOTE type="cite">Thanks, Martin. Could you clarify a bit about this
sentence? Do the<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">sources that you quoted give an
explanation?<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">"cement-based products in contrary are accepted to
reduce the PCF<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">(product-carbon-footprint) as the CO2 used for
production is stored<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">for a long time."<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">What I find confusing, is that production of
cement produces a lot of<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">CO2 from fossil fuels in mining, processing,
calcining, and utilizing.<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">It produces/releases a fair amount of sequestered
CO2 from the<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">limestone during the calcining chemical reaction.
I'm not thinking of<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">any point at which "the CO2 used for production"
is stored at all. A<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">small amount of CO2 is reabsorbed from the air by
finished concrete,<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">but what I have read is that this is a tiny
fraction, and needs to be<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">tiny, to maintain the integrity of the
concrete.<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">So what CO2 storage are they talking
about?<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">Derek<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">--On Thursday, May 6, 2010 9:24 PM +0200 martin
oehlmann<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><<A
href="mailto:moehlmann@wanadoo.fr">moehlmann@wanadoo.fr</A>>
wrote:<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">Dear all,<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">however not much response here on this issue...
some possible<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">interesting observations in the
meantime:<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">According the perception of IPCC and UN-FCC
straw and wood are not<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">seen as CO2-sink, yet CO2 neutral, cause of the
durability is<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">“difficult” to calculate. In contrary
cement-based products in<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">contrary are accepted to reduce the PCF
(product-carbon-footprint) as<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">the CO2 used for production is stored for a long
time. (source:<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">Memorandum Product Carbon Footprint, German
Ministry for Environment,<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">Nature Protection
etc.)<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">Comment: compliments for the cement lobby, low
cost cementbased<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">massproduction for housing with a lifespan 30-40
years.<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">If planted forests get cut after 30 years and
seen as a CO2 sink, a<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">high quality building which lasts 100 years and
longer built with<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">natural materials better should be perceived as
storage, if the<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">intention from IPCC and UN-FCC is to support
sustainable<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">constructions.<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">Nice day and all the very
best,<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">Martin Oehlmann<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">Brittany<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">Derek Roff<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">Language Learning Center<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">Ortega Hall 129, MSC03-2100<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">University of New Mexico<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">Albuquerque, NM 87131-0001<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">505/277-7368, fax 505/277-3885<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">Internet: <A
href="mailto:derek@unm.edu">derek@unm.edu</A><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE
type="cite">_______________________________________________<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">GSBN mailing list<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><A
href="mailto:GSBN@greenbuilder.com">GSBN@greenbuilder.com</A><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><A
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<DIV>Tom Woolley</DIV>
<DIV><BR class=khtml-block-placeholder></DIV>
<DIV>Rachel Bevan Architects</DIV>
<DIV>80 Church Road</DIV>
<DIV>Crossgar</DIV>
<DIV>Downpatrick</DIV>
<DIV>BT30 9HR</DIV>
<DIV><A
href="mailto:tom.woolley@btconnect.com">tom.woolley@btconnect.com</A></DIV>
<DIV>028 44 830988</DIV><BR
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<DIV>
<DIV>Dr John Straube, P.Eng.</DIV>
<DIV>Associate Professor</DIV>
<DIV>University of Waterloo</DIV>
<DIV>Dept of Civil Eng. & School of Architecture</DIV>
<DIV><A
href="http://www.buildingscience.com">www.buildingscience.com</A></DIV></DIV></SPAN></DIV><BR></DIV></BODY></HTML>