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RE: Rammed earth construction

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I do RE in BC, Canada.  If I can help ...
 
1)  Get lab tests done on the available material - material is site-specific and needs care in selection.
 
2)  Generate several particle-size gradings of the material and develop "mixes" that when tested give the "best" behaviour.
 
3)  Decide what, if any, admixtures you might want to add.  Eg: cement, flyash, other pozzolans etc that may be beneficial to the final working material.
 
4)  If you decide to go reinforced RE and cement stabilized RE then make sure that you are comfortable using the masonry block design standards.  Most engineers use masonry or concrete.  While masonry approximates what is essentially a cement-stabilized aggregate, I'm not convinced yet.
 
5)  For further information on material choice, SIREWall Inc here on Saltspring Island, BC has over 15 years of aggregate sampling experience, design of RE structures, and has a fund of knowledge on the behaviours of RE material in Canada, China and the US.  I am one of their structural consultants so we familiar with their work.
 
6)  I don't know Rwandan climates but while RE does perform well in wet and cold climes, it is prudent to design with reasonably large overhangs of the roof.  Verandahs are an excellent way to protect.
 
7)  If you go with cement-stabilized RE then curing is as important as in conc. construction.
 
8)  There is a lot of info on the internet.  Peter Walker of Bath University, UK has done much research on un-reinforced RE and Kepa Morgan of Auckland University, NZ and done a lot of work with fibre-reinforced RE.  If you go with unreinforced and no-additive RE then I recommend those 2 Profs will be of great help.
 
Hope this helps you get started.  If you need any further assistance then please contact me privately.

Thor A. Tandy P.Eng, C.Eng, Struct.Eng, MIStructE
UNISOL Engineering Ltd
Unit 7 - 625 Hillside Ave
Victoria, BC, V8T 1Z1
Tel/Fax: (250) 382-9115
Email: vicpeng(--nospam--at)telus.net

-----Original Message-----
From: Michael Hemstad [mailto:mhemstad(--nospam--at)mbjeng.com]
Sent: Friday, October 31, 2008 10:17 AM
To: seaint(--nospam--at)seaint.org
Subject: Rammed earth construction

All,
I have a project in Rwanda on which my client wants to try some alternative means of construction.  Rammed earth and straw bale construction have come up.
 
(For those who haven't heard of these, rammed earth is made by building wall forms, placing soil in them, and pounding it until it rings.  It makes a durable, fireproof wall with local materials and labor.  Straw-bale construction involves stacking straw bales, often dowelling them together with wood dowels, then applying thick parging to each side.   This apparently results in a strong, fireproof, relatively durable wall too, although I know less about it than rammed earth.)  
 
Does anyone have information on either of these?  I am specifically looking for information on what soil properties are needed for a successful rammed-earth installation (e.g. clay content, sand content, moisture content).  I don't yet know whether a geotechnical engineer is available to the project; so information of the "holds together as a ball when dropped" type is also appreciated.
 
I appreciate any help, or alternate suggestions.
 
Thanks,
Mike Hemstad, P.E., S.E.
MBJ
Minneapolis, Minnesota