An acoustic, material saving aesthetic ceiling

Researchers at ETH Zurich developed a concrete ultra-efficiency structural element that uses the advantages of 3D-printed formwork: material reduction, acoustic advantages and aesthetics.

Called HiRes Concrete Slab, the concrete slab is a thin, double curved funicular shell. Vertical stiffeners transfer loads to the boundary supports through compression forces only. The forces are concentrated in the corners, where their horizontal thrust is distributed to post-tensioned ties. The material is placed only where it is structurally needed, according to the flow of forces through the shell. This approach results in a 70% reduction of material compared to a standard reinforced concrete slab.

Used as a soffit, the slab is decorated with flowing contours that reach their highest density in a central peak and fade out towards the perimeter. The pattern is based on several constraints that reflect the fabrication process and the functional requirements of the slab. In addition, the pattern aims to achieve a balanced composition within the asymmetrical vault while reacting to the optimal position of the lights and ventilation outlets within the shallow vault. The patterns enhance the acoustic quality of the space.

The slab is made using 3D-printed formwork. There are three main components within the formwork system. Firstly, 43 binder-jet 3D-printed formwork parts define the bulk of the surface. The 3D-printed parts are only five centimetres in thickness to reduce material and production costs. Secondly, a laser-cut waffle supports the thin 3D-printed parts to ensure a precise transition between the flat surface of the standard scaffolding system and the uneven lower surface of the 3D-printed parts. Combining the two processes ensures a fast, resource-efficient process, designed to be flexible enough to deal with on-site tolerances.

The third fabrication process is polymer extrusion 3D printing, which complements binder-jetting to devise the integrated functional features of the slab developed in collaboration with A/S: integrated heating and cooling, ventilation ducts, and provisions for lighting features.

Photos: Andrei Jipa / Digital Building Technologies (DBT), ETH Zürich