C-FORM fire protection recess
Formwork element with integrated fire penetration seal

The new C-FORM fire protection recess from Hensel is a prefabricated formwork made of concrete using a 3D printing process with an integrated fire protection bulkhead. All EN-approved HENSOTHERM® and HENSOMASTIK® product systems for the construction of fire protection penetration seals with European Technical Assessment (ETA) from Hensel can be pre-installed, e.g. a HENSOMASTIK® mixed penetration soft seal with 2 x 50 mm or 1 x 60 mm mineral fibre boards.

How does concrete 3D printing work?

Concrete 3D printing, also known as additive concrete construction or concrete additive manufacturing, is an innovative technology that makes it possible to produce complex structures from concrete in a single step. The common abbreviation for concrete 3D printing is 3DCP for 3D Concrete Printing or 3D Construction Printing. But how does concrete 3D printing actually work?

3D printing with concrete essentially works in a similar way to other forms of additive manufacturing, in particular it is comparable to the 3D printing of extruded plastics, but with specific adaptations for processing concrete materials. In fused deposition modelling (FDM) of plastics, extrusion refers to the process in which the printing material, usually a plastic filament, is heated and forced through the nozzle of the print head to form a thin layer of the object, which is then built up layer by layer to create the final 3D object. In contrast to conventional construction methods, where concrete is poured into a formwork or mould, concrete 3D printing is built up layer by layer by extruding special concrete mixtures that have the right flowability and ensure rapid curing without the need for significant heating as with plastic filaments.

For production, a digital model of the C-FORM fire protection recess with the desired dimensions is first created to control the 3D printer. This model is then broken down into small layers that are to be printed one after the other. The process of converting a 3D model into a series of layers or slices is therefore also known as slicing.

The slicing software plays a central role in the 3D printing process. It regulates the thickness of each layer that is printed and the printing speed. A smaller layer height leads to higher resolution and finer details, but also increases the printing time. A higher speed can shorten the print time, but possibly at the expense of print quality. It is important that a concrete layer has sufficient time to cure so that it develops enough strength to support the weight of the overlying layers without the structure deforming or even collapsing. A special concrete mix was specially developed for the C-FORM fire protection recess to optimise the ratio between compression speed, strength and maximum construction height.

Once all the settings have been made, the software generates the so-called G-code, which controls the precise movements and operations of the 3D printer. The G-code contains instructions for each layer and movement of the print head as well as for temperatures and other relevant parameters. With the generated G-code, the 3D printer can now build up the C-FORM fire protection recess layer by layer.

After complete drying and curing, the desired product system for fire protection penetration seals is installed with the specified positions of the mineral fibre boards by trained specialists using original Hensel products. The mineral fibre boards coated with the waterproof fire protection coating HENSOMASTIK® 5 KS Farbe/viskos are force-fitted into the C-FORM fire protection recess and bonded at the sides with HENSOMASTIK® 5 KS Spachtel filler and sealed to prevent the penetration of moisture. Finally, if necessary, protective films are applied to additionally protect the C-FORM fire protection recess from waterlogging and dirt. These are particularly recommended if the mineral fibre board layers are not flush with the component surface and water could collect in the stripping element.

3D printing is an innovative technology that is also becoming increasingly important in the construction industry. Precast moulds produced using the 3D printing process are just the tip of the iceberg. Overall, concrete 3D printing offers new possibilities for the construction industry and opens up exciting opportunities for the design of architectural structures. Using concrete 3D printing, impressive concrete structures and complete buildings can be realised that are aesthetically pleasing as well as stable and durable.

Another important aspect of concrete 3D printing is its sustainability. Through the targeted use of materials and the reduction of waste, the consumption of resources can be minimised and the environmental impact reduced.

Overall, concrete 3D printing offers enormous potential for the construction industry and promises numerous advantages in terms of efficiency, flexibility and sustainability. It is expected that this innovative technology will play an increasingly important role in the design and construction of buildings and infrastructure in the future.