Concrete is probably the most widely used building material in the world. Anyone who wants to build a house with it nowadays needs not only a plot of land, but above all one thing: time. It is not unusual for up to three months to pass before the shell, i.e. the foundation, the exterior walls and the roof structure, are in place. Concrete is classically shaped by formwork on the construction site or in a precast plant. A concrete formwork is a kind of casting mold into which a steel reinforcement is inserted. The mold is then filled with concrete. The use of formwork elements is associated with an increased need for personnel and equipment, and also has a significant impact on the duration and overall cost of the construction project.

If materials, costs and time are to be reduced, one technology is enjoying particular attention: additive manufacturing or 3D printing. The potential of this technology has not gone unnoticed by the construction industry either. Various branches of research are now looking into direct 3D printing of concrete. One process stands out: contour crafting, or 3D concrete printing. It is said to be able to build entire houses in just 24 hours. What’s behind this technology? It’s high time we took a closer look.

What is Contour Crafting?

Contour crafting refers to a special form of 3D concrete printing. In this process, an extruder nozzle attached to a gantry crane is used to apply a concrete mixture. The crane or extruder nozzle travels along a digital floor plan of the building object and places layers of concrete on top of each other – to a certain extent similar to the FDM process. It is important to note that the term Contour Crafting is trademarked by the Contour Crafting Corporation. Founded by Behrokh Khoshnevis, the company began researching direct concrete 3D printing using extruders in 2008. Other leading manufacturers, especially in the concrete formwork industry, are also dedicated to the development of concrete 3D printing, including companies such as Doka and Peri.

How does Contour Crafting or 3D printing in concrete work?

As with all 3D printing processes, CAD data forms the basis of the printing process. This computer-generated data is fed into the 3D printer. Most concrete 3D printers work with a similar approach: Layers of concrete are placed on top of each other by means of a nozzle attached to movable axes. In the process, the printer or nozzle traverses the floor plan layer by layer, pulling up both the interior and exterior walls. Recesses for window and door frames are often already shown in the digital floor plan and are also kept clear by the printer. Fast-curing special concretes are often used as materials. Ultra High Performance Concrete (UHCP concrete) is characterized by its high resistance to physical or chemical influences and also hardens particularly quickly. This enables continuous and uninterrupted 3D printing.

What is Contour Crafting used for?

Concrete 3D printing technology is ideal for rapid construction of houses or storage facilities. It is still in the development stage, and there are only a few 3D-printed houses. But the construction industry continues to work diligently on this manufacturing process. If the technology matures and proves effective and efficient, in just a few years it could be possible for more and more people to 3D print their own homes.

Customer Story: DOKA

In this webinar, the renowned German formwork manufacturer, Deutsche Doka, will talk about their experiences of 3D printed formwork elements.

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What are the advantages of contour crafting or 3D printing in concrete?

Concrete 3D printing brings decisive advantages: time and cost savings. Unlike conventional house construction, contour crafting does not require any formwork to pour concrete walls. Work steps such as setting up formwork and laying out curbing are eliminated. Accordingly, house construction using 3D printers requires only a few workers. This also reduces costs: if only the printer has to work, the resources freed up can be used elsewhere. Material and labor costs are reduced, and the completion of the project is accelerated overall. Concrete 3D printing technology can be particularly effective after natural disasters, for example, when many shelters need to be quickly restored.

What other uses might there be for Contour Crafting in the future?

The construction industry faces many challenges, including the careful use of limited resources, a continuously growing world population, rising material costs and the need for affordable housing. This is where 3D concrete printing can provide a remedy. With appropriate software solutions, buildings can be planned in such a way that only exactly as much material is used as necessary. In addition, concrete 3D printing can be used to create new housing quickly and cost-effectively, even after natural disasters or in other humanitarian crises. These possibilities make concrete 3D printing interesting for the construction industry and a promising technology approach for the future.

What does Contour Crafting look like at voxeljet?

At voxeljet, we do not (yet) use any form of concrete 3D printing. Although our binder jetting technology also allows us to 3D print concrete directly, projects in this direction are still at the research stage. However, the feasibility is given: Instead of sand or plastic, we can apply cement or concrete powder to the building platform using a recoater and print a special water-based binder using our print head. Possible applications could be, for example, integral formwork for concrete casting.

Project examples for Contour Crafting

The first 3D-printed residential building in Germany comes from Peri, a company specializing in formwork. The de-monstration object is used in particular for show purposes to familiarize the market with the technology.

At voxeljet, we rely on the combination of 3D printing and conventional formwork construction. With our binder jetting technology, we can print highly complex formwork elements that – if appropriately post-processed – can be used like conventional formwork elements on the construction site. This technology approach is characterized above all by its possibilities for material savings and the feasibility of implementing complex multi-curved objects using special formwork.


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