The Materials Book

Holy Concrete! Hollowing out sections can reduce the material needed by up to 60 percent Building elements affected by bending—for instance, slabs and beams—rarely use materials efficiently. It’s hard to minimize weight by changing the shape of these elements, and it’s often impractical because unusual forms are difficult to integrate into designs. An alternative approach developed by Werner Sobek instead seeks to reshape these elements from the inside. Low-stress areas of the concrete can effectively be hollowed out with spherical voids in various sizes, while parts that face greater stress remain solid—and therefore stronger. This strategy can reduce mass by as much as 60 percent without reducing load-bearing capabilities. Example: Concept of gradation by the use of mineral hollow spheres (left: sphere packing, right: concrete structure), developed at ILEK, University of Stuttgart, Germany Contributed by: Institute for Lightweight Structures and Conceptual Design (ILEK), University of Stuttgart, Germany 371