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The Concrete Pump was invented in 1927, nearly a century ago. The Concrete Boom Pump Truck was invented in 1958, over a half-century ago. Truck-mounted concrete boom pumps are well-established equipment for heavy construction.
The next step in evolution is to adapt the Concrete Boom Pump Truck for
precision computer control over the end-nozzle where the concrete comes out, for precision printing of large building structures from concrete.
Nozzle at the end of the Boom Hose will be fitted with a printer head which can control the output of the concrete. This print-head is attached to a cable-pulley system which will precisely control the movement of the print-head, to lay down layer after layer of concrete, just like a 3D printer.
This is similar to the Contour Crafting idea of Prof Behrokh Khoshnevis of University of Southern California, except that his design doesn't make use of the already pre-existing legacy functionality of the Concrete Boom Pump Truck.
Concrete Boom Pump Truck
See Link to Concrete Boom Pump Truck [sanman, Jan 30 2013]
See Link to Contour Crafting [sanman, Jan 30 2013]
Using 3D printers to build houses
It's already very nearly a reality. [DrBob, Jan 31 2013]
Insulated concrete forms build walls using the concrete boom
This concept comes close to sanman's idea. Hopefully the right concrete formula and pouring procedures would allow the forms to be removed (+) [Sunstone, Feb 01 2013]
||A boom truck arm isn't nearly precise enough to build a
structure the way Dr. Khoshnevis' design does, but it could
definitely be set up to automatically fill any number or
pattern of forms.
||It's not the Boom Truck Arm which provides the precise control, it's the cable-pulley system which would be attached to the print-head to move it more precisely by computer control.
||The problem is that properly mixed concrete is rather
liquid, and will not hold shape while it cures. So
you're either going to end up with what is essentially
a structure made up of very thin (and structurally
weak) concrete laminate layers with uneven edges,
about a half inch to an inch being the most that can
be deployed at any one time, or you're going to end
up with something at concrete's wet angle of repose,
which I believe is somewhere round 10-15 degrees.
||Getting the concrete to hold shape is simply a matter of finding the right formulation, and additionally finding a way to partially cure it as it comes out of the printer head. That last part might be done through some kind of intense heating, so that the concrete comes out hot with the water evaporating sooner. Or there could be some kind of chemical binder that gets mixed in at the print head, which causes rapid curing as it comes out. There are various possible solutions, and it's a matter of finding the optimal one.
||The problem is that if concrete is sufficiently solid
or cured to hold its shape, it won't bond well to
the layer beneath, nor the layer above. This
would produce a very flaky concrete that wouldn't
hold up for any length of time. While there are
paint on adhesives specifically designed to fix this
problem when patching concrete, they are
extremely expensive relative to the bulk concrete.
Even then, I don't believe they're as strong as
unitary cured concrete.
||A massive 3D printer to print the forms would be a
||I'm still waiting for fully autonomous agile
construction bots with integrated power hammers,
drills, and so forth.
||A modern construction worker pretty much needs
power, pneumatic, and other leads everywhere
anyway so it's just a matter of intelligence and
||It's also a matter of experience. There are uncountable
little tricks and subtle skills that go into building something
of quality. It's not just about having the right tools and
||I suppose first we do the rebar with a 3d "vector" printer
||//water evaporating sooner// Concrete doesn't set by evaporation of water.
||One way to reduce slumping is to add fibres.
||I've messed around with free-form cob construction, wherein you add handfuls of mud and straw (or similar) to the growing structure. In a sense, it's a primitive version of this idea.