Ken Kern did some work with substituting lime for portland cement in his
slipformed concrete systems.
A good slipforming system was also developed by the Helen and Scott
Nearing, and is described in their book "Living The Good Life"
In the Nearing system, you essentially have a conventional concrete
wall, except that the hand-placed rocks are really just large aggregate.
This allows you to reduce the proportion of portland in a conventional
1:2:3 portland:sand:aggregate mix. One way to reduce the fraction of
portland further, or be able to substitute a weaker binder like lime, is
to add more information to the hand-placed rocks, ie., use some of the
principles of conventional stone masonry in placing them and in
selecting the rocks themselves.
Another interesting new system worth checking out is cast earth. There
is an article in the last issue of Fine Homebuilding, and a website at
http://www.lvnexus.net/nimud/
It avoids some of the labor intensive aspects of conventional rammed
earth methods by using a poured earth slurry that uses gypsum as a
binder.
Conventional stabilized rammed earth uses about 10% portland as a
binder, whereas concrete is about 13% portland, so there is not much
difference in embodied energy with rammed earth, plus you need thicker
walls. Traditional (or reinforced) stone masonry, with a high skilled
labor content, would probably have the least embodied energy, depending
on how and where you got the stone.
-- -------------------------------------------------------- Norbert Senf email: mheat@mha-net.org Masonry Stove Builders mheat@hookup.net RR 5, Shawville website: http://mha-net.org/msb Quebec J0X 2Y0 fax: 819.647.6082 voice: 819.647.5092 __________________________________________________________________ This greenbuilding dialogue is sponsored by Oikos (www.oikos.com) and Environmental Building News (www.ebuild.com). For instructions send e-mail to greenbuilding-request@crest.org. __________________________________________________________________