CO2-Enhanced Concrete Is Better - 3-D Printing Method Developed

https://scitechdaily.com/scientists-transform-co2-into-super-strong-3d-printed-concrete/

The structure also displayed better strength and durability. The printed 
concrete was up to 36.8 percent stronger in compression (how much weight 
it can bear) and up to 45.3 percent stronger in bending (how much it can 
flex before breaking) compared to regular 3D-printed concrete.

. . .

   The concrete blocks were 3-D printed - basically kinda
   2cm thick 'ropes' of concrete stacked up.

   However unless you NEED lots of exotic shapes, it'd
   probably be better to use ordinary cast blocks.

   In any case, moist CO2 injection does seem to improve
   the product. Likely affects crystal formation geometry.

   I think it HAS been done already, you CAN 3-D print
   an entire house using layered extrusions to build
   up and up. However we're talking LARGE 'printer'
   machines here, generally I don't see how it's worth
   all the effort and expense except as 'proof of
   concept'.

   If you want a 'molded' house, try using waste plastic/sand
   mix instead. Such parts can take the form of pre-fab bolt-
   together wall segments too. Took some searching, but waste
   plastic + sand is actually pretty damned good and strong
   enough for at least a 2 or maybe 3 floor home. Ideal mix
   seems to be 4 or 5 parts sand with the plastic serving
   as the 'glue'.

   The BEST concrete is made with volcanic ash or something
   very similar like coal fly-ash - the ROMANS thought up
   this one, then the secret was lost. There IS a whole
   lot of natural volcanic ash to be had - think Mt.St.
   Helens - and the supply is always replenished. Coal
   ash ... industrial countries have VAST mountains of
   the stuff everywhere. Ash-based concrete has a slightly
   different chemistry from 'Portland' cement. It's very
   strong, it LASTS the ages, even hardens underwater.

   Anyway, today, I'd strongly suggest going with pre-fab
   wall segments four to six inches thick (the latter if
   cat-3+ winds are an issue). They come on a truck, a
   crane just plops them into position. Very quick and
   you save the expense and possible screw-ups of masons
   putting in individual concrete blocks. Just slap an
   inch or two of insulating sheet and some wallboard
   on the inside and you've got a nice house in a
   third the time. This CO2 chemistry is NOT gonna be
   limited to just 3-D stuff.

   (Hey, WOOD wall-boards, not that cheapo gypsum-board
   crap !  :-)

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