Production of Curved Precast Concrete Elements for Shell Structures and Free-form Architecture using the Flexible Mould Method

Free-form buildings tend to be expensive. By optimizing the production process, economical and well-performing precast concrete structures can be manufactured. In this paper, a method is presented that allows producing highly accurate double curved-elements without the need for milling two expensive mould surfaces per single element. The flexible mould is fully reusable and the benefits of applying self-compacting concrete are utilised. The flexible mould process work as follows: Thin concrete panels are cast in a horizontally positioned flexible mould, using a selflevelling concrete. After a certain initial hardening, the mould is deformed and the concrete is allowed to harden further. The knowledge about rheological characteristics is essential during casting and to find the suitable moment for the mould to be deformed. The behaviour of the concrete in the plastic stage is important: A) to allow the concrete to follow the deformation of the flexible mould, B) to counteract its movement under a slope and C) to prevent cracking in an early phase. After the flexible mould has reached its final position, the concrete develops its strength and can be demoulded in a short production-cycle; aesthetically attractive elements of different and complex geometries can be produced with the same reusable mould.