<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">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 href="http://greenbuilder.com/mailman/listinfo/GSBN">http://greenbuilder.com/mailman/listinfo/GSBN</a><br></blockquote><br><br>_______________________________________________<br>GSBN mailing list<br><a href="mailto:GSBN@greenbuilder.com">GSBN@greenbuilder.com</a><br><a href="http://greenbuilder.com/mailman/listinfo/GSBN">http://greenbuilder.com/mailman/listinfo/GSBN</a><br></div></blockquote></div><br><div apple-content-edited="true"> <span class="Apple-style-span" style="font-size: 12px; "><div style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; -webkit-text-decorations-in-effect: none; text-indent: 0px; -webkit-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; -webkit-text-decorations-in-effect: none; text-indent: 0px; -webkit-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><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 class="Apple-interchange-newline"></span></span></div></span> </div><br></div></div>_______________________________________________<br>GSBN mailing list<br><a href="mailto:GSBN@greenbuilder.com">GSBN@greenbuilder.com</a><br>http://greenbuilder.com/mailman/listinfo/GSBN<br></blockquote></div><br><div>
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><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>