3D printing with concrete a technology for the future for which in the present still some problems have to be solved

It is interesting to see today what printing results universities and printer manufacturers achieve.

The results are an interplay between printer technology and material technology. In my opinion today, very good results are achieved in the design areas with the printers, but many problems still have to be solved in professional architectural building construction.

There are

Compressive strength

The standard concrete reaches its maximum compressive strength after 28 days. For the printing technology unacceptable, here must be helped with accelerator. Printing speed and strength development must be matched and optimized without loss of strength.
UHPC Ultra High Performance Concrete can be a solution. Strengths of over 200 MPa can be achieved here.

Print speed

Of course you want an optimum speed, you want to process a large amount / weight of concrete in a very short time. The concrete should be able to support itself after a very short time and be load-bearing for ceiling elements.
With UHPC materials, large amounts of material are already processed in a short time using the wet and dry spraying process. The consistency of the UHPC print material can be adapted to the printer characteristic. UHPC materials already develop high strength values in short time in the standard qualities. However, this time can be extremely reduced by changing material production.

Statics

The print heads are usually small in diameter and the applied wall thicknesses compared to a masonry or a finished concrete wall are very thin. Static load-bearing walls can be printed for several floors, or double-skin walls must be printed in order to achieve a structurally stable construction. Do I have to print double-shelled?

Heat / cold insulation

If I print with a standard concrete I do not achieve any insulating properties. So I have to print double-shelled and fill the cavity with insulation material or retrofit an insulating layer from the inside.
At the moment we are the only ones who are able to combine a high pressure resistant material with an insulating material. This combination material is also pumpable.

Steel girders, reinforcements

Even with 3D printing, you can not ignore reinforcements and support structures, or you can remain eternally restricted to small, simple and low-rise building constructions. How can I optimally combine carrier structures, steel reinforcements with a single printing process?

Last but not least interesting design

So far I have seen the obligatory pressure bulges on all prints. For the beginning, this may be fine but soon you should have printing technologies that ensures a sharp-edged pressure even on the wall corners. A rework of the walls in the flat areas to get is cost and time consuming. Of course, when I use the printing technology, I also want to print exceptional geometry and thin-walled constructions.

I have a note at the end

If all my misgivings can be wiped out the question remains if I want to print a large building, I need a fairly large printer technology which is not even built and dismantled and I need a very fast continuous flow of material to the printer when the printer should work quickly.

I do not want to know misunderstood. I think 3D printer technology is very interesting for the future and I know that some engineering companies are working on technical solutions. As part of our material development, we also work on a flexible, extreme fast-curing, high-compressive strength material for the printer producer. In close technical agreement with the respective printer manufacturer, we can adapt our UHPC materials to the requirements and provide test material to the printer manufacturer.