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RE: Rammed earth construction

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Hi Yi

Assuming that masonry standards apply to rammed earth (and I'm not yet
convinced of that) then I invoke (conservative) masonry anchor technology.
I have found that careful drilling into cured RE and using appropriate epoxy
adhesive results in a satisfactory anchoring system.  I use this when window
and door lintels are to be placed between wall sections (assists with
uniform truss/floor layouts over openings).  Or I go with a top-hung hanger
that is usually onto the top plate on top of the wall.

I always make sure that "structural" anchors be kept a min of 6" from any
wall end, and mid point in any wythe (we use insulated wall panels here.  I
try to stay with 1/2" anchors.  If the lintel is between segments then there
is a measure of support from the strut action of the lintel.

BTW, for reinforced RE walls, I also stay with 5/8" or less bar.  The
smaller the bar the better the compaction around the bar.  At the other
extreme, large, or bundled bars, are IMO a no-no!

Thor A. Tandy P.Eng, C.Eng, Struct.Eng, MIStructE
Victoria, BC
Canada
  -----Original Message-----
  From: Yi Yang [mailto:YI(--nospam--at)summit-sr.com]
  Sent: Monday, November 03, 2008 5:06 PM
  To: seaint(--nospam--at)seaint.org
  Subject: RE: Rammed earth construction


  Thor,

  I'm curious on how you get anchor values (epoxy anchor I assume), say in a
ledger condition.



  YI YANG, S.E.



----------------------------------------------------------------------------
--
  From: Thor Tandy [mailto:vicpeng(--nospam--at)telus.net]
  Sent: Friday, October 31, 2008 9:39 AM
  To: seaint(--nospam--at)seaint.org
  Subject: RE: Rammed earth construction


  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