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<P align=left>Mark and All,</P>
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<P align=left>I am sure you will be aware of some of what I suggest, as it's common knowledge in the earth plaster world. Too much clay, too little sand/aggregate, the size of the sand/aggregate (too fine sand) can all cause excessive cracking. Removing clay, adding more sand/aggregate or <SPAN id=DWT207 class=ZM-SPELLCHECK-FIXED word="uping">upping</SPAN> the size of the sand/aggregate could help. I've found that the more/longer straw added can eliminate higher clay content cracking. I've used a 1:1:1 ratio of clay, long straw, masons sand for a very sticky, super strong, low/no cracking application to stick as a base over foam, lumber and plywood (placing some of this mix on the surface, tack mesh to subsurface, place more mix, for an added mechanical bond). </P>
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<P align=left>When you start adding lime and cement to a mix sounds like what we do in the US. If it doesn't move, get a bigger hammer. It's not better living through <SPAN id=DWT208 class=ZM-SPELLCHECK-MISSPELLED word="'bigger">'bigger</SPAN> <SPAN id=DWT209 class=ZM-SPELLCHECK-MISSPELLED word="hammer'">hammer'</SPAN> chemistry. Often less is more. I think you'll find some of your answers to cement earth plaster ratios in a study by the U. of Penn as they attempted to do some repairs to the mortar on ancient ruins in the Mesa Verde and <SPAN id=DWT210 class=ZM-SPELLCHECK-MISSPELLED word="Chaco">Chaco</SPAN> Canyon adobe structures. <SPAN class=serp_results_site><A href="http://repository.upenn.edu/cgi/viewcontent.cgi?article=1044&context=hp_theses"><SPAN id=DWT211 class=ZM-SPELLCHECK-MISSPELLED word="http">http</SPAN>://repository.<SPAN id=DWT212 class=ZM-SPELLCHECK-MISSPELLED word="upenn">upenn</SPAN>.<SPAN id=DWT213 class=ZM-SPELLCHECK-MISSPELLED word="edu">edu</SPAN>/<SPAN id=DWT214 class=ZM-SPELLCHECK-MISSPELLED word="cgi">cgi</SPAN>/<SPAN id=DWT215 class=ZM-SPELLCHECK-MISSPELLED word="viewcontent">viewcontent</SPAN>.<SPAN id=DWT216 class=ZM-SPELLCHECK-MISSPELLED word="cgi">cgi</SPAN>?article=1044&context=hp_theses</A></SPAN> You'll find test results on "tensile strength, modulus of rupture, water vapor permeability, and water porosity (respectively) (and freeze/thaw) </FONT><I><FONT face=Arial-ItalicMT>vs</I></FONT><FONT face=Arial>. volume-percent of Portland cement for amended mortars" . </FONT></P>
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<P align=left><FONT face=Arial>Also, you might check out Stabilized Compressed Earth Block sites (adobe block on steroids...it's what happens when engineer types make adobe block). My limited experience with <SPAN id=DWT217 class=ZM-SPELLCHECK-MISSPELLED word="SCEB's">SCEB's</SPAN> is they only use about 6-12% cement...lime may be substituted, but don't quote me. Check out the Auroville Earth Institute <A href="http://www.earth-auroville.com/">www.earth-auroville.com</A> for mixes using cement. Maybe others can chime in here with knowledge on substituting lime for cement. Of coarse, different areas have different clays that react in <SPAN id=DWT218 class=ZM-SPELLCHECK-FIXED word="variing">varying</SPAN> ways so experimenting with different mixes/ratios would be prudent. The one advantage of using cement amended earth mixes is that it hardens much faster so the results of your experimenting is swifter.</FONT></P>
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<P align=left><FONT face=Arial>For a shameless plug for the Conference in Sept. 2012 <A href="http://www.strawbaleconference.com/index.html"><SPAN id=DWT219 class=ZM-SPELLCHECK-MISSPELLED word="http">http</SPAN>://www.<SPAN id=DWT220 class=ZM-SPELLCHECK-MISSPELLED word="strawbaleconference">strawbaleconference</SPAN>.com/index.<SPAN id=DWT221 class=ZM-SPELLCHECK-MISSPELLED word="html">html</SPAN></A> the Auroville Institute will be represented at the conference by a presentation by Richard Presley. </FONT></P>
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<P align=left><FONT face=Arial>If the locals insist on using cement additives to the earthen plaster mix, visiting the information on these two sites should help with your educated guess as to ratio's. I did some extensive stone work this last summer and wanted to use an earthen mortar. I used a 9:1 mix of my earth plaster mix/cement. My mason buddy thought I was nuts. Eight months later, 4 feet of snow and lots of freeze/thaw in our Colorado winter climate and that mix seems to be holding up amazingly. There's little to no <SPAN id=DWT222 class=ZM-SPELLCHECK-FIXED word="degredation">degradation</SPAN> of the mortar.</FONT></P>
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<P align=left><FONT face=Arial>For those interested in pre-fab straw bale walls and those using cement stucco's these amended earthen mixes may be worth noting.</FONT> </P>
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<P><FONT face=Arial>Hope this helps Mark...<SPAN id=DWT223 class=ZM-SPELLCHECK-FIXED word="Rregards">Regards</SPAN>,</FONT></P><FONT face=Arial>
<DIV><SPAN name="x"></SPAN>Mark (see you in September) Schueneman<BR>Colorado Straw Bale Association</DIV>
<DIV>303-444-6027 hm.<BR>303-591-9841 cell<SPAN name="x"></SPAN><BR></DIV></FONT>
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<P align=left><B>From: </B>"Mark Jensen" <<SPAN id=DWT224 class=ZM-SPELLCHECK-MISSPELLED word="markj">markj</SPAN>@<SPAN id=DWT225 class=ZM-SPELLCHECK-MISSPELLED word="redfeather">redfeather</SPAN>.org><BR><B>To: </B>GSBN@<SPAN id=DWT226 class=ZM-SPELLCHECK-MISSPELLED word="sustainablesources">sustainablesources</SPAN>.com<BR><B>Sent: </B>Saturday, March 3, 2012 3:44:05 AM<BR><B>Subject: </B>[GSBN] Plaster thoughts<BR><BR>Hello <SPAN id=DWT227 class=ZM-SPELLCHECK-MISSPELLED word="et">et</SPAN> <SPAN id=DWT228 class=ZM-SPELLCHECK-MISSPELLED word="al">al</SPAN>,</P>
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<DIV>I am in Kenya right now working on two straw bale buildings, stacking for both Monday and Tuesday. I am struggling with plaster thoughts. I guess the last plaster they did was clay, sand, cow dung, chopped straw, lime, cement and water. Nobody knows the proportions but they had severe cracking, like a dried up lake bed.</DIV>
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<DIV>Now they want to do 1 1/2 bags of lime, 1/2 bag cement, 4 wheelbarrows of sand, chopped straw and water. This seems like a recipe for disaster to me. They are on a very short budget. I suggested harvesting clay and just doing a earthen plaster, it's free other than some labor to harvest. </DIV>
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<DIV>Any thoughts on the recipe above?</DIV>
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<DIV>Your input would be appreciated.</DIV>
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<DIV><SPAN id=DWT229 class=ZM-SPELLCHECK-MISSPELLED word="Asante">Asante</SPAN> Sana, Thank you very much,</DIV>
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<DIV>Mark</DIV><BR>_______________________________________________<BR>GSBN mailing list<BR>GSBN@<SPAN id=DWT230 class=ZM-SPELLCHECK-MISSPELLED word="sustainablesources">sustainablesources</SPAN>.com<BR><SPAN id=DWT231 class=ZM-SPELLCHECK-MISSPELLED word="http">http</SPAN>://<SPAN id=DWT232 class=ZM-SPELLCHECK-MISSPELLED word="sustainablesources">sustainablesources</SPAN>.com/mailman/<SPAN id=DWT233 class=ZM-SPELLCHECK-MISSPELLED word="listinfo">listinfo</SPAN>.<SPAN id=DWT234 class=ZM-SPELLCHECK-MISSPELLED word="cgi">cgi</SPAN>/GSBN<BR><BR><BR>-- <BR></div></body></html>