Z眉blin uses a Putzmeister 3D printer to construct a warehouse for Strabag in Germany (Image: Putzmeister)

The building is Strabag Baumaschinentechnik International鈥檚 newest warehouse in Stuttgart, Germany, and its construction will both create a new facility for Strabag while testing Z眉blin鈥檚 3D printing capabilities and processes.

Using Putzmeister鈥檚 KARLOS mobile concrete printer, the machine鈥檚 mast boom has a 26-metre reach. It鈥檚 extensive span, Z眉blin said, allows the application of 鈥渃oncrete in several layers precisely on the basis of a predefined and digital blueprint via a special print head.鈥�

Alexander Kuhn, head of technical services construction and technology at Z眉blin, said, 鈥淭he basis of the KARLOS printing process is an intelligent truck-mounted concrete pump, whose telescopic arm can move and deliver concrete automatically along predefined paths in three-dimensional space using a specially developed print head.

Until now, the challenges of 3D concrete printing have mainly been the lack of scalability of the technology for large-scale projects. 鈥淧rinting has mainly been done with so-called portal printers, which are limited to the production of smaller buildings,鈥� said Z眉blin.

The company added that KARLOS allows more flexibility and range, which provides the potential for scalability 鈥� even for large-scale projects.

鈥淭he economic advantage of this 鈥榳orld-first鈥� technology, compared to other concrete or mortar printing technologies like using a gantry printer, lies in its flexibility and range as well as in the ability of printing load-bearing solid walls in one step that comply with relevant standards and regulations,鈥� added Kuhn.

The finished Strabag warehouse after KARLOS, a Putzmeister 3D printer, delivered the concrete paste. (Image: Putzmeister)

Delivering cementitious paste in a rectangular method, much like the form of a brick (as opposed to a rounded edge like most 3D concrete printers), the squared walls are able to support the weight of the building.

鈥淪tacked on top of each other, the cuboid cross-sections of each layer result in unreinforced but load-bearing concrete walls that do not require any further work steps,鈥� added Kuhn, noting 鈥渢he material used in this process is plain concrete, C30/37, in accordance to EC2.鈥�

Using every aspect of automation

The project was not without its challenges, however. Kuhn added that a multifaceted and dynamic plan helped pull the structure together. 

鈥淢ajor challenges to getting load-bearing capability are to be found in the combination of concrete technology and process technology,鈥� he acknowledged. 鈥淥n the one hand, concrete recipes must take into account an early-stage strength as well as an adequate consistency regarding the pumping process, whereas on the other hand, the pumping boom must be exactly controlled with regards to positioning and movement speed.

鈥淔urthermore,鈥� he continued, 鈥渃ontrolling and monitoring the concrete shrinking behaviour and its strength gain are crucial in order to avoid cracks within each layer and between adjacent layers which could result either in the collapse of the freshly printed wall section prior to and/or in (partially) the loss of mechanical properties of the wall after reaching the final concrete strength.鈥�

Combined with electrification, digital planning, and use of a BIM model on this project, Z眉blin said it鈥檚 hoping to develop novel construction methods for the future.

鈥淭he combination of the production steps from the digital planning of the BIM model (Building Information Modelling) to the implementation by 3D printer revolutionizes the processes in construction. Work processes are significantly streamlined and accelerated by automation,鈥� said the company.

鈥淚n addition to the complete elimination of formwork work, the economic and ecological advantages of the method include the production of solid wall cross-sections in a single operation and the use of CO₂-reduced concretes.

鈥淏y using only green electricity for the all-electric machine and using CO₂-reduced concretes, Z眉blin and Putzmeister are making an important contribution to making building construction more sustainable in the future.鈥�