The gradation of concrete elements allows for an functional adaption of the inner structure and thereby, also of the elements properties regarding the static and structural-physical requirements. An automated way of construction is a key feature to enable reproducability for graded concrete elements. The entire process, starting from an optimization based element design, the subsequent mixture selection, dosage and conveyance, and finally the material application with or without formwork, needs to be covered by and integrated into a process control concept. This conceptual design and the implementation of an automated process chain in from of a prototypical test rig as well as the development of a suitable control concept are the key research features for the ISYS in this interdisciplinary research, which is pursued in collaboration with the Institute of Construction Materials (IWB) and the Institute for Lightweight Structures and Conceptual Design (ILEK).
Werner Sobek initiated the research on the graded concrete technology in 2011. Since then it has been continuously developed further in an interdisciplinary collaboration between the ILEK, ISYS and IWB at the University of Stuttgart. Within two research projects as part of the DFG priority program 1542 - Lightweight Construction with Concrete - ("Optimal structures from functional graded concrete elements – design, computation and automated construction" and "Efficient and automated manufacturing of multifunctional graded concrete components with mineralized hollow bodies") an automated process chain for the manufacturing of graded concrete elements with a concrete dry-spraying technique has been realized. This involves the targeted development of concrete mixtures with adaptable density, the element design with an optimized material placement, as well as an automated manufacturing process enabling an accurate positioning of the adaptable concrete mixtures.
Automated manufacturing of a boundary layer with dry-sprayed concrete
Manufacturing of a middle layer through superposition of standard and lightweight concrete
Manufacturing of a hollow body from concrete
In the current research ("Multi-functional graded elements for the sustainable construction with concrete" founded by the Baden-Württemberg Foundation) an alternative concrete process technology (wet-spraying) is investigated. At this, the technology of mineral hollow bodies shall be extended towards an automated manufacturing process. With these hollow bodies cavities can be placed even more effectively in unstressed areas of the concrete elements and therefore, improve the savings in resources without spoiling the recyclability. Within another research project ("Development of an ecological and economical way of construction through usage of precast multifunctional wall elements from graded concrete" founded by the Research Initiative "Zukunft Bau") the transferability of the concept towards wall construction elements shall be shown.
We would also like to gratefully thank our founders of our research projects and the supporters from the industry.