[HH] 3D printing with concrete

[Tom Metro]

I made a comment abut 3D printing with concrete on Google+ and a
response post linked to this:

http://www.theverge.com/2012/2/21/2811146/3d-printing-d-shape-monolite-enrico-dini

An article about a guy developing a building printer, similar to the
other one mentioned here, but this one uses sand plus an inorganic,
two-part, non-epoxy binder. (So if it isn't epoxy, then what is it? No
real details on the binder. I guess that's the "secret sauce.")

The demo structures seem to be more free-form - including domes - though
also not very smoothly finished. I suppose easily fixed with some stucco
or shotcrete.

If I understand the description of how it works correctly, it works more
like traditional stereo lithography systems where you start with a layer
of powder (sand), then do something to the portion you want to keep to
solidify it, then discard the excess powder. ("The surplus sand that
doesn't get printed acts to buttress the structure, and can be reused
for the next print.") This probably explains why the process can create
domes and other spanning structures.

The article also mentions there is a documentary in the works on the
inventors life.

 -Tom