3D-printed Clay Formwork for Topology-Optimized Concrete Elements

Abstract

"The use of topology-optimized precast concrete elements leads to material savings and thus to a reduction in the CO2 footprint
of a building. Material is only used where it is structurally necessary. The optimum shape of a component is influenced by its
structural boundary conditions. This results in a variety of bespoke shapes and geometries. Additive manufacturing techniques
such as 3D printing are particularly suitable to produce such formwork. This paper examines the production of 3D-printed
formwork elements made of clay using the example of an optimized concrete ribbed slab. The use of unfired clay as a formwork
material is intended to enable a circular reuse of the same material for subsequent prints. For a simplified analysis of the
manufacturing process, work is carried out on a reduced model scale of 1:8 or 1:16. Two manufacturing strategies will be
tested. Firstly, a segmented formwork system to produce the ribs without a ceiling slab is investigated, and secondly, individual
displacement bodies are produced which are then placed in a wooden formwork and with which the ribs and ceiling slab can be
cast at once. In both cases, the clay is kept in a moist state until the concrete is poured. Both production strategies can achieve a
dimensionally accurate result, as the clay does not deform or crack due to drying. In addition, the clay can be easily removed
from the finished component after the concrete has hardened and contains only minor impurities. The production of formwork
or displacement bodies for optimized concrete parts from 3D-printed clay is showing promise as an alternative to other
materials such as plastic or concrete. As clay and concrete do not form a permanent bond during the curing process, the clay
can be recycled. However, further investigations into the processing and cleaning of the dried clay are necessary to make precise
statements about the proportion of reusable clay."