The concept of functionally graded materials (gradient materials) has its origins in aerospace engineering. The physical properties of the material are varied along at least one of the three spatial directions and thus optimally adapted to the requirement profile. Werner Sobek was the first to transfer this technological approach to the construction industry and invent the so-called gradient concrete (Gradientenbeton®).
Graded concrete (Gradientenbeton®) is not to be understood as a pure material, but rather as a technology for internal structural optimization and weight reduction of concrete components. Components made of gradient concrete are characterized by the fact that their physical properties such as strength, density, stiffness or thermal conductivity are specifically adapted to the stress profile prevailing inside the component by means of pore-forming measures. In micrograding, for example, mineral lightweight aggregates with different volume contents are introduced into the concrete composition in an automated spraying process in order to optimally meet the requirements in the component in terms of strength and stiffness.
Mesograding involves the creation of larger cavities in the component by installing mineral hollow bodies developed at the institute or reversible formwork techniques. Regardless of the grading methods chosen, they combine, on the one hand, the approach of a monomaterial technology to ensure complete and unmixed recyclability of the component at the end of its life. On the other hand, material is only used inside the component where it is actually needed. In this way, the weight and consequently the resource consumption of graded concrete components can be reduced by 50% or more compared to solid components, while maintaining the same functionality and performance.
At the Institute for Lightweight Design and Construction (ILEK) of the University of Stuttgart, material technologies, manufacturing processes, calculation methods as well as fields of application for graded concrete (Gradientenbeton®) have been investigated for more than 20 years within the framework of research projects and scientific work.