Optimization of the flexible mould process for the production of double-curved concrete elements

Abstract

Free-form buildings tend to be expensive. By optimizing the production process, economical and wellperforming concrete structures and elements can be manufactured. In this paper, an innovative 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 self-levelling 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. The flexible mould process was studied with an experimental program on the influence of the mould material, shaping mechanism, element thickness, mix design and rheological characteristics. High strength self-compacting concrete was applied with different aggregate sizes for the production of the elements. In initial experiments, no reinforcement was added in the panels. In later tests, elements were reinforced with textiles that were able to follow the deformation of the mould.