Free Formwork: 3D printing for complex concrete architecture

Abstract

Concrete, the most used human-made material in the world, is responsible for circa 8% of the total greenhouse gas emissions globally. Due to this significant impact, efficient concrete construction methods are one of the most researched topics in architecture, civil engineering, and materials science. One of the important hurdles that need to be overcome is the limitation of traditional flat-panel formworks, which lead to inefficient and oversized building elements. Most investigations focus on extrusion 3D printing with concrete, which has the advantage of bypassing the need for formworks altogether. Instead, the present thesis considers a different approach, which aims to digitise formwork construction. At the intersection of architectural design and digital fabrication, the present research investigates a new fabrication method for concrete based on 3D-printed formworks. Motivated by the gap between the unlimited geometric freedom of digital design and the physical constraints of fabrication, the research aim is to facilitate complexity in concrete construction. Geometric complexity is not a goal in itself but rather a prerequisite for achieving material efficiency, functional integration, and a radically new design vocabulary for concrete. The thesis identifies two 3D printing technologies that are suitable for high-resolution details and large build volumes: polymer extrusion and binder-jetting. First, polymer extrusion is investigated for the fabrication of formwork shells less than 1 mm in thickness. For speeding up the printing process for large objects, a custom computational workflow is developed, and optimised for reducing the extruder travel times. Furthermore, the research puts forward methods to mitigate the corrosive action of concrete on thin 3D-printed polymer shells. Subsequently, the free-form polymer formworks are used to produce a concrete canoe, a helical stair prototype, and a funicular slab with an integrated, efficient ventilation system. Second, binder jetting is an alternative 3D printing process used to fabricate formworks with the resolution of a grain of sand. These formworks were used to fabricate two functional building elements in real-world buildings: the Smart Slab, completed in 2018, and the HiRes Slab, completed in 2021. The two concrete elements are comparable in size but use different approaches, one being prefabricated and post-tensioned, while the other was unreinforced and cast in situ. Additionally, the HiRes Slab demonstrates the integration of an efficient custom ventilation system based on thin stay-in-place 3D-printed formworks. Through the case studies, 3D-printed formworks demonstrate an unprecedented capability to produce free-form and high-resolution geometries in concrete. Due to this potential, it is a viable method in real-world construction in its own right, not simply a stepping stone towards 3D concrete printing. The approach brings together the geometric freedom of digital formworks with the material strength of familiar concreting processes. The resulting method enables new possibilities in architecture for material efficiency, structural and functional optimisation, and freedom of design expression rooted in the plasticity of concrete