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<TITLE>Re: [GSBN] Follow up re mesh in clay</TITLE>
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<FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>Felie,<BR>
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Not off topic at all. This looks like a terrific kit for testing the important characteristics of soil and earthen materials for construction. <BR>
<BR>
I like the low tech and compact press using a small jack for testing compressive strength of samples. The entire kit is expensive for a single project in a poor community, but I can see it being very valuable for an entire community or an organization implementing multiple projects. And it is far less expensive than a full lab and is portable. One could also obtain only the pieces that are relevant to specific needs. The instruction pdf looks great.<BR>
<BR>
Thank you.<BR>
<BR>
Martin<BR>
<BR>
</SPAN><SPAN STYLE='font-size:8pt'><B><I>Martin Hammer, Architect<BR>
</I></B><I>Builders Without Borders<BR>
</I></SPAN><SPAN STYLE='font-size:7pt'>Berkeley, CA, USA<BR>
510-525-0525 (office)<BR>
510-684-4488 (cell)<BR>
Port-au-Prince, Haiti<BR>
509-4930-8579 (Haiti cell)<BR>
www.builderswithoutborders.org <BR>
</SPAN><SPAN STYLE='font-size:9pt'><BR>
<BR>
On 8/29/13 8:53 AM, "Feile at Mud and Wood" <<a href="feile@mudandwood.com">feile@mudandwood.com</a>> wrote:<BR>
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</SPAN></FONT><BLOCKQUOTE><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>Slightly off topic - but this soil testing kit was developed at Bath University, UK, specially for earth construction in developing countries (including conservation repairs) - all parts easily replaceable off the beaten track. It only became available this year.<BR>
<BR>
<a href="http://www.bath.ac.uk/ace/research/cicm/low-carbon-materials/low-cost-test-kit-construction-apps.html">http://www.bath.ac.uk/ace/research/cicm/low-carbon-materials/low-cost-test-kit-construction-apps.html</a><BR>
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I'm not sure if tests for salts or PH are included - but all of the other characteristics necessary to make a judgement on soil suitability can be tested. It might be of interest to some of you.<BR>
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Regards<BR>
<BR>
<BR>
Feile<BR>
<BR>
<BR>
</SPAN><FONT SIZE="4"><SPAN STYLE='font-size:10pt'><B>Féile Butler<BR>
</B></SPAN></FONT><B><SPAN STYLE='font-size:9pt'>MRIAI B.Arch Dip. Arch Conservation Grade III<BR>
</SPAN></B></FONT><B><FONT COLOR="#990000"><FONT SIZE="5"><FONT FACE="Courier New"><SPAN STYLE='font-size:12pt'>Mud and Wood<BR>
</SPAN></FONT></FONT></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>Grange Beg, Skreen, Co. Sligo, Ireland<BR>
</SPAN></FONT></B><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'> <BR>
</SPAN><SPAN STYLE='font-size:8pt'><B>T: +353 (0) 71 930 0488 <BR>
M: +353 (0) 86 806 8382<BR>
E : </B></SPAN><B><FONT COLOR="#0066CC"><SPAN STYLE='font-size:9pt'><a href="feile@mudandwood.com">feile@mudandwood.com</a><BR>
</SPAN></FONT><SPAN STYLE='font-size:8pt'>W:</SPAN><SPAN STYLE='font-size:9pt'> <FONT COLOR="#0066CC">www.mudandwood.com</FONT></SPAN><SPAN STYLE='font-size:8pt'> <mhtml:{AACFA5AA-422F-463C-803B-AB35086D2473}mid://00000614/!x-usc:http://www.mudandwood.com/> <BR>
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----- Original Message ----- <BR>
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<B>From:</B> Derek Stearns Roff <<a href="mailto:derek@unm.edu">mailto:derek@unm.edu</a>> <BR>
<BR>
<B>To:</B> Global Straw Building Network <<a href="mailto:GSBN@sustainablesources.com">mailto:GSBN@sustainablesources.com</a>> <BR>
<BR>
<B>Sent:</B> Thursday, August 29, 2013 2:30 PM<BR>
<BR>
<B>Subject:</B> Re: [GSBN] Follow up re mesh in clay<BR>
<BR>
<BR>
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As you will see below, a few of us have had a bit of off-list discussion on steel mesh in clay. Martin thought this might be of interest to some on the GSBN list, so here it is. <BR>
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<BR>
<BR>
Derek<BR>
<BR>
<BR>
<BR>
On Aug 29, 2013, at 12:47 AM, martin hammer wrote:<BR>
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</SPAN></FONT><BLOCKQUOTE><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'> <BR>
Hi Derek,<BR>
<BR>
Thanks very much for taking the time to answer Dmitry’s questions with such careful thought. People on the GSBN might also be interested in what you had to say, but I’ll leave it up to you if you want to post it (probably along with Dmitry’s questions) on the GSBN.<BR>
<BR>
Best.<BR>
<BR>
Martin<BR>
<BR>
<BR>
On 8/27/13 9:05 PM, "Derek Roff" <<a href="derek@unm.edu">derek@unm.edu</a> <x-msg:<a href="//11/derek@unm.edu">//11/derek@unm.edu</a>> > wrote:<BR>
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</SPAN></FONT><BLOCKQUOTE><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>Hi, Dmitry and Martin,<BR>
<BR>
I'm happy to try and answer your follow up questions, although I don't want to give the impression that I am an authority. I have researched these questions out of my own interest, and revisited some of them in greater detail, in response to Martin's questions. I have not done any formal research on this myself, but am drawing from my modest building experience, and from Internet research resources. <BR>
<BR>
Your question on testing soil in developing countries is an interesting one. I don't know how available testing materials would be in various locations. For testing pH, I think it could be reasonable to transport the needed pH paper. pH paper is inexpensive, and a single $10 roll could test perhaps a hundred soil samples. pH paper can be very accurate. Electronic pH meters are another possibility. Some are available for under $100. A problem with electronic meters is that they require calibration, normally with carefully prepared calibration fluids of certified pH. That makes the process rather more complex for mobile, field operations. <BR>
<BR>
Testing for salts is not so simple as using pH paper, but there are electronic soil salinity meters for around $100-$200. There are a few that cost less, including this one at $15.59. <a href="http://www.amazon.com/HM-Digital-TDS-EZ-Measurement-Resolution/dp/B002C0A7ZY/ref=pd_sim_sbs_lg_2">http://www.amazon.com/HM-Digital-TDS-EZ-Measurement-Resolution/dp/B002C0A7ZY/ref=pd_sim_sbs_lg_2</a> I can't vouch for its accuracy, but perhaps it would be sufficient for our building purposes. Alternatively, soil testing is one of the fundamentals of improving agriculture, so in many locations, it might be possible to have soil tested locally by an agricultural extension agency or laboratory. This could be a good way to connect with the local economy and researchers. <BR>
<BR>
On your second point, I may have not communicated clearly in my earlier message. For galvanized steel, the zinc coating will, of course, corrode first, both because it coats the steel, and because it is intended to be a sacrificial coating. I would think that galvanized steel would always last longer than bare steel, but it will cost more, and not be as widely available. A separate point that I was trying to make, is that with bare steel in concrete, the rate of corrosion will increase if some other (non-reinforcing) galvanized steel or aluminum (or another metal) is also embedded in the concrete, or attached, nearby. This can happen when concrete reinforced with normal, bare reinforcing steel also has galvanized or aluminum flashing, anchors, awnings, roofing, decking, or other metal objects embedded in the concrete or attached to it. These dissimilar metals can set up an electrical potential, in effect turning the concrete into a simple battery. The tiny current flow will increase the corrosion rate of the bare steel. This is sometimes called galvanic corrosion. It would not happen in clay with a fairly neutral pH, that is free of salts and other electrolytes. It would happen in an acid soil, or one with salts. However, earthen plasters/bricks/cob are likely to be less electrically conductive than concrete, even when they have a similar salinity, so I would expect the galvanic corrosion to be less in clay. <BR>
<BR>
Increasing the pH of the earthen material in contact with the steel will decrease the corrosion rate. However, the effect is most significant at really high pH values, pH 11 or above. Reaching this pH level would require a lot of lime, which would be very expensive. If the clay soil used for the earthen mixes was mildly acidic, it might be reasonable to add enough lime to get the mix into the alkaline range (above pH 7). Clays and limes vary, so every local soil and lime mix must be tested to make sure it bonds well without too much cracking. <BR>
<BR>
Your final question is one that I am curious about, in relation to clay plasters with steel. The research shows that steel corrosion in concrete increases in wetter climates, since it increases the electrical activity of the concrete. I wonder if the same would be true for steel in clay, assuming non-acid, non-salty clay. These clays are less conductive and great moisture buffers. I want to believe that they would protect the steel more, but I don't have any evidence to support this, beyond seeing some very old steel embedded in old adobe houses, with quite modest corrosion levels. <BR>
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I hope some of this is useful.<BR>
<BR>
Best wishes,<BR>
Derek<BR>
<BR>
On Aug 26, 2013, at 5:04 PM, Dmitry Ozeryansky wrote:<BR>
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<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>Hello Derek, <BR>
Thank you for your very informative reply to our question!<BR>
<BR>
May I ask you a few brief follow ups?<BR>
<BR>
</SPAN></FONT><UL><LI><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>If we were to recommend use of steel mesh in clay plaster for developing countries, are there simple tests for salts and pH that we could/should prescribe to determine if local subsoil is adequate?
</SPAN></FONT><LI><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>You say that zinc corrodes faster than steel in concrete, is that also true for clay?
</SPAN></FONT><LI><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>Would you propose adding lime to the plaster mix to further reduce the rate of corrosion?
</SPAN></FONT><LI><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>Do you think that wet climates would significantly increase the rate of corrosion? <BR>
</SPAN></FONT></UL><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>Best regards,<BR>
<BR>
Dmitry Ozeryansky<BR>
<BR>
</SPAN></FONT><SPAN STYLE='font-size:9pt'><FONT FACE="Arial Black"><B>OZERYANSKY ENGINEERING</B></FONT><FONT FACE="Arial"> <BR>
www.ozerengineering.com <<a href="http://www.ozerengineering.com">http://www.ozerengineering.com</a>> <<a href="http://">http://</a>www.ozerengineering.com/> <BR>
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</FONT><FONT FACE="Arial Black">South Main Retrofit Initiative<BR>
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</FONT></SPAN></BLOCKQUOTE><SPAN STYLE='font-size:9pt'><FONT FACE="Arial"><BR>
</FONT></SPAN><FONT SIZE="5"><FONT FACE="Helvetica, Verdana, Arial"><SPAN STYLE='font-size:12pt'>Derek Roff<BR>
<a href="derek@unm.edu">derek@unm.edu</a> <x-msg:<a href="//11/derek@unm.edu">//11/derek@unm.edu</a>> <BR>
<BR>
</SPAN></FONT></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'><BR>
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</SPAN></FONT></BLOCKQUOTE></BLOCKQUOTE><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'><BR>
<BR>
Derek Roff<BR>
<a href="derek@unm.edu">derek@unm.edu</a><BR>
<BR>
<BR>
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